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16. Lymphatic dranaige of thoracic organs. The diaphragm. The histology of the skin. Implantation. Formation and differentiation of the trophoblast. Early phases of placentation.

16 Dec

16. Lymphatic dranaige of thoracic organs. The diaphragm. The histology of the skin. Implantation. Formation and differentiation of the trophoblast. Early phases of placentation.

Flash Cards:

Diaphragm 1

Diaphragm 1

Anatomy: Lymphatic dranaige of thoracic organs. The diaphragm.

Lymph Drainage of Thoracic Organs:


  • superficial (subpleural) lymphatic plexus –  deep to visceral pleura, drain tissue of lung itself and visceral pleura –> bronchopulmonary l.n
  • Deep lymph plexus (submucosal) – in submucosa of bronchi, and in peribronchial CT, drain structures that will go into root of lung  –> pulmonary l.n along bronchi –> broncho pulmonary l. n
  • From bronchopulmonary l.n. –> sup/inf tracheobronchiol lymph nodes ( above/below bifurcation of trachea) –> R & L bronchomediastinal l.n. @ angulus venosus
  • R bronchomediastinal l.n. –> R lymphatic duct
  • L bronchomediastinal l.n. –> thoracic duct
  • Lymph from parietal pleura –> nodes of thoracic wall ( IC, parasternal, mediastinal, phrenic l.n.), some near cupula pleura go to axillary l.n.

Lymph Drainage of heart:

  • Lymph vessels in myocardium and subendocardial CT –> subepicardial lymph plexus –> coronary  groove & follow coronary a
  • some will flow to inf tracheobronchial l.n. on R side


lymph vessels of thymus –> parasternal, brachiocephalic and tracheobronchial l.n

Posterior mediastinum:

Posterior mediastinal l.n. rec lymph from esophagus, post side of diaphragm and pericardium, middle/post IC spaces –> thoracic duct


  • ant/post diaphragmatic l.n. on thoracic surface of diaphragm –> parasternal, post mediastinal, phrenic l.n
  • diaphragmatic l.n. on abdominal surface of diaphragm –> ant diaphragmatic, phrenic, superior lumbar l.n

    • absorb peritoneal fluid


Thoracic Duct:

  • in posterior mediastinum
  • lies of ant side of T5-T12
  • receives lymph from:
    • lower limbs,pelvis, abdomen, and left upper quadrant of body
    • and middle/upper IC spaces, post mediastinal structures
    • jugular, subclavian, bronchomediastinal lymph trunks
  • originates from cisterna chyli in abdomen
  • comes thru aortic hiatus
  • empties eventually into L angulus venosus

ant = esophagus
post = vertebral column
left = aorta
right = azygos v

Right Lymphatic duct:

  • also in post mediastinum
  • receives lymph from R upper quadrant of body: R half of head & thorax, and R upper limb
  • empties into R angulus venosus



Parts of Diaphragm:
Central fibrous tendon – clover leaf shaped, no bony attachment
Peripheral musc fibers:

  • sternal part – attach to post side of xyphoid process
  • costal part – attach to inf six costal cartilages, and ribs – form R & L domes of diaphragm
  • lumbar part – from med/lat arcuate ligaments, L1-3, form R & L crura

Med arch: made of the crura of diaphragm : musc/tendon bundles from ant surfaces of L1-L3, ant longitudinal ligament, IV discs

  • R crus – L1-3/4,
  • Lcrus – L1-2

Lat arch:

  • Med arcuate lig – L1 body –> transv process of L1, rib 12, passes over psoas major and SNS trunk
  • Lat arcuate lig – transverse process of L2 –> rib 12, passes over quadratus lumborum


  • central tendon attaches to pericardium via pericardiophrenic ligaments


  • xyphoid process (sternum)
  • lower 6 costal cartilages and ant costal margin
  • med/lat lumbosacral arches (lumbar arches)
  • tip of 12th rib


  • insert into central tendon of diaphragm
  • b/w 12th rib and lumbar vert, diaphragm will attach to fascia over quadratus lumborum, psoas major

major musc of inspiration/expiration

1. Contraction = diaphram desc, causing inc thoracic volume, by inc vert diameter of thoracic cavity –> dec intrathoracic pressure –> Lungs EXPAND

2. Relaxation = diaphram asc, causing dec thoracic volume, by dec vert diameter of thoracic cavity –> inc intrathoracic pressure –> Lungs DEFLATE

Openings of Diaphragm:
A. Outside diaphragm
1. Sternocostal triangle – b/w rib cage & sternal and lumbar part of diaphragm – contains int thoracic a/v or sup epigastric a/v
2. Aortic hiatus – behind diaphragm, space b/w L and R crus  – contain Aorta, thoracic duct, gr. splanchnic n, azygos v (called asc lumbar v below diaphragm)

B. W/in Diaphragm
1. Caval hiatus – lies in central tendon, @ T8, to the R and post – contains IVC, R phrenic n, lymph vessels
2. Esophageal hiatus – T12 behind crossing of L & R crus – contains Esophagus, ant/post trunks of vagus

C. Structures that pierce diaphragm w/o specific opening

  • SNS trunk
  • Splanchnic n

Surface Projection of Diaphragm:
R = upper border of 5th rib @ midinguinal line – higher b/c of liver underneath it, attaches to liver via coronary ligament, R & L triangular ligament
L = lower border of 5th rib @ midinguinal line

Blood supply:

  • Musculophrenic (int thoracic a)
  • Pericardiophrenic (int thoracic a)
  • Sup/inf phrenic (aorta)

Nerve supply:

  • SM = phrenic n
  • Central tendon SS = phrenic n
  • Peripheral musc SS = IC n

Develops from:

  • septum transversum
  • pleuro-peritoneal folds
  • mesoderm of adjacent bodywalls
  • esophageal mesoderm
Ignore the developmental errors, just see where it develops from

Ignore the developmental errors, just see where it develops from

Histology: The histology of the skin.

Embryology: Implantation. Formation and differentiation of the trophoblast. Early phases of placentation.


  • occurs w/in ant/post sup wall of uterus on day 7 after fertilization w/in functional layer of endometrium during secretory phase of menstrual cycle
  • this is when the trophoblast splits into cytotrophoblast & syncytiotrophoblast
  • the Uterine glands and arteries become coiled b/w opening of glands


  • Syncytiotrophoblast – outer multinucleated cells of trophoblast
    • no mitosis
    • invasion of endometrial stroma, eroding the endometrium a/v & glands
    • lacunae formed w/in – filled w/ nutrient material from maternal blood & glandular secretions – comes in via diffusion
    • NOTE Fetal and maternal blood never mix!!
    • Endometrial stromal cells = filled w/ glycogen + lipids =to feed to embryoblast
  • Cytotrophoblast = inner mononucleated layer of trophoblast, mitotically active
    • makes cells that migrate to syncytiotrophoblast
    • from cells into mounds called primary villi (chorionic villi)


  • @ 3rd wk = Primary villi form = cytotrophoblastic core covered by syncytioblast
  • mesodermal cells –> core of primary villi, grow toward decidua = secondary villi
  • @ end of 3rd wk = mesodermal cells in the core –> differentiate into RBCs + small a/v = form villous capillary system = tertiary villi
  • Tertiary villi – connect w/ a/v of mesoderm of chorionic plate and in connecting stalk
    • connect w/ intraembryonic circulation  = connect placenta w/ embryo
  • Cytotrophoblastic cells in villi –> syncytioblast –> endoderm form a  thin outer cytotrophoblastic shells = attaches chorionic sac firmly to maternal endoderm
  • Anchoring villi = villi from chorionic plate that extend to decidua basalis
  • Free villi = villi that branch from anchoring villi, into intervillous spaces
  • @ 24th day, embryo attached to trophoblastic shell by connecting stalk
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The bones, muscle, fasciae, nerves, blood vessels and lymphatic dranaige of the thoracic wall. The histology of the mammary gland. The formation and differentiation of the extraembryonic mesoderm.

15 Dec

The bones, muscle, fasciae, nerves, blood vessels and lymphatic dranaige of the thoracic wall. The histology of the mammary gland. The formation and differentiation of the extraembryonic mesoderm.

Flash Cards:

Thoracic Wall - Joints and Fascia

Thoracic Wall - Joints and Fascia

Thoracic Wall - Ribs, musc, movements

Thoracic Wall - Ribs, musc, movements

Thoracic Wall - Intercostal spaces and arteries, nerves, etc

Thoracic Wall - Intercostal spaces and arteries, nerves, etc

Thoracic Wall Blood supply lymph nerves

Thoracic Wall Blood supply lymph nerves

Anatomy: The bones, muscle, fasciae, nerves, blood vessels and lymphatic dranaige of the thoracic wall.

Anatomy of Thoracic Wall

Function: protects contents of thoracic cavity, mechanical function of breathing

Thoracic Inlet: T1, 1st pair of ribs +their costal cartilages, sup border of manubrium

Thoracic Outlet: T12, 11th,12th ribs, costal cart of ribs 7-10, xiphisternal joint

12 ribs, sternum, vertebral column

Has 3 parts:
Head = Manubrium

  • has 2 clavicular notches to that articulates laterally w/ clavicle
  • Sup margin has jugular notch
  • lat side articulates w/ 1st rib
  • @ level of T3-T4


  • Joins w/ manubrium @ Manubriosternal joint = sternal angle
    • located @ border b/w T4-5
    • Important marking point for:
      • Jxn b/w manurbium and sternal body
      • @ 2nd rib articulates w/ sternum
      • aortic arch begins and ends
      • trachea –> R & L bronchi
      • inf border of superior mediastinum
  • Body starts as 4 sternabrae that fuse in life
    • fusion lines = transverse ridges

Xyphoid process

  • joins body @ Xyphisternal joint @ level of T9/T10
  • is flat and cartilaginous @ birth
    • slowly ossifies
    • becomes fully bone @ middle age
  • CLINICAL NOTE – People notice it in their 40’s and think there is a new growth in the area
  • Marks:
    • border b/w thorax & abdominal cavity
    • ant attachment of diaphragm
    • sup surface of liver
    • R margin of heart
    • stomach

Head, Neck, Tubercle, Body, angle

Classicification of Ribs:
1-7 true ribs – attach directly to sternum via cartilagenous extension (vertebrocostal)
8-12 false ribs – do not attach directly to sternum

  • 8-10 attach to ant costal margin (Vertebrochondral)
  • 11-12 do not have an anterior attachment, but “float” , only articulate w/ vert bodies post (vertebral, free)

Movements of ribs:

3 important joints:

  • Costovertebral – head articulates w/ vertebral bodies, each head attaches to 2 vertebrae, @ their junction pt
  • Costotransverse – tubercle of rib attaches to transverse processes to vertebrae
  • Sternocostal – ribs 1-7
  • Costochondral – ant connection w/ ribs and cartiliage that attaches them to sternum, ant costal margin

2 types of movements:

  1. “pump handle”

    • change the ant-post diameter,
    • when upper ribs are elvated, inc the ant-post diametere
  2. bucket handle”

    • change lateral diameter
    • when middle parts of lower ribs move lat, when elevated

Anim: Movements of Ribs during breathing

See Diaphragm, Lung topic for more on breathing process.

Joints & Fascia of Thoracic Wall
1. Sternoclavicular Joint

  • b/w manubrium of sternum, head clavicle
  • moves like ball and socket, saddle type joint
  • fibro cart articular surface
  • 2 synovial cavities, sep b/ w IV disk, like TMJ
  • Ligs = ant/post sterno-clavicular, costo-clavicular joint

2. Costovertebral Joint

  • 2 joints in one:
    • Costovertebral – b/w head of rib and articular facet of vertebral body
    • Costotransverse – b/w tubercle of rib & transverse process of vertebra
  • plane type joint
  • Ligs =
    • (ant) radiate lig, intra articular lig
    • (post)lat/sup costotransverse lig
      • b/w sup c.t. lig and vertebrae allowes spinal n and dorsal br of IC a to come out

3. Sternocostal =

  • b/w ribs and sternum, either directly, indirectly
  • rib 1 = primary cartiligenous connection
  • 2-7 = synovial plane joint
    • Lig = ant/post radiate sternocostal
  • 8-10 = cxt w/ costal margin, not sternum,
  • 11-12= do not connect w/ sternum

Other joints:

  • Intervertebral joints (see vertebral column)
  • Costochondral- b/w ribs and costal cartilage
  • Interchondral- b/w costal cartilages & ant costal margin
  • Manubriosternal – listed above
  • Xyphisternal – listed above

Fascia of Thoracic Wall
1. Sub cutaneous tissue = superficial fascia aka Camper’s fascia

  • loose CT just below skin w/ ligament = retinacula cutis
  • contains: a/v/n,  sweat glands, lymph vessels, mammary glands
  • Remember it this way – Campers go out in the woods and hunt and eat, so they have more fat – therefore the fatty fascia is Camper’&s

2. Deep (investing) fascia

  • thin fibrous membrane b/w subcut tissue and skin
  • NO fat
  • covers and invests muscle & their tendons = epimysium
  • holds thorax together
  • is barrier to infection
  • Named for part covered:
    • Pectoral – breast bed, pectoralis major m
    • Clavi-pectoral – clavicle, pect minor m
    • Endothoracic – inf side of thoracic cage
  • Located where fleshy portions of IC m missing
  • cont as IC membrane
  • CLINICAL NOTE – Endothoracic fascia is thin fibro-alveolar layer b/w int aspect of thoracic cage and lining of pulmonary cavity–> opened surgically to gain access to intra thoracic structures

Muscles of Thoracic Wall
* all innervated by IC n, except levator costarum (dorsal primary rami of C8-T11)

3 layers of musc in IC spaces:
1. Ext layer – Ext IC m
2. Middle layer – Internal IC
3. Internal layer – Innermost IC, Subcostal, Transverse Thoracis, Levator Costarum

Elevators of ribs:

  • External IC
    • tubercles of ribs –> costochondral junctions, run inf/lat direction
    • cont inf w/ ext oblique m
  • Internal IC – ant portion (chondral)
    • run deep and perpendicular to Ext IC m
    • floors of costal groove –> inf/post –> sup borders of ribs inf
  • Innermost IC –
  • Subcostalis
  • Levator costarum – transv pr of C7,T1-12 –> run inf/lat –> rib tubercles

Depressers of ribs:

  • Internal IC – post portion (costal)
  • Transverse Thoracis
    • 4/5 strips of m that attach to post side of body of xyphoid process/sternum –> run sup/lat–> 2-6 costal cart

Muscles of Thoracic wall not related to IC spaces:
Serratus post mInspiration

  • Superior part:
    • (nuchal lig (inf), spinous processes of C7, T1-T3 –> runs inf/lat –> sup border of 2-4th, 5th rib)
    • => elevate 1st 4 ribs
  • Inf part:
    • (sp processes of T11-12, L1-2 –> runs sup/lat –> T8-T12 inf border)
    • depresses last 4 ribs
    • prevents them from pulled up by diaphragm

Superficial Musc of Thorax:

  • Pectoralis major – flexes and adducts the arm, medially rotates the arm
  • Pectoralis minor – draws the scapula forward, medialward, and downward
  • Serratus ant – rotate & hold scapula, it draws the scapula forward; the inferior fibers rotate the scapula superiorly
  • Scalene m – lift ribs 1+2 in forced breathing
  • Subclavius m


Intercostal Spaces – structure, content, related structures

Layers of IC space:

  1. skin
  2. subcutaneous CT
  3. Ext IC m and membrane
  4. Int IC m and membrane
  5. IC a/v/n – located in costal groove, @ inf border of rib
  6. Innermost IC m
  7. Endothoracic fascia
  8. Parietal wall of pleura

IC blood supply:

  • Subclavian a
    • Int thoracic a – 1st branch, Thoracic part
      • gives off pericardiophrenic a
      • ant IC 1-6 a
      • ant perforating br –> med mammary br
      • thoracoepigastric a
        • runs behind/lat to sternocostal joint and gives 1st 6 IC a
      • sup epigastric a –> runs in rectus sheath, and anatomoses w/ inf epigastric a
      • musculophrenic a
        • gives off IC a 7-9 a
        • anatomosis w/ deep circumflex iliac a
    • NOTE – IC spaces b/w 10/11th rib, and 11/12 ribs do NOT HAVE a ant IC a
    • supreme IC a
      • and from costocervical trunk
      • gives of 1st 2 post IC a
  • Axillary a –> gives off lat thoracic a
  • Thoracic aorta –> gives post IC a
    • as mentioned above, 1st 2 post ICa come from costocervical trunk of subclavian a
    • post IC 3-11a direct from of thoracic aorta
  • Br of IC a
    • dorsal br
    • lat cut br
    • ant perforating br
    • collateral br

NOTE – Each IC space has 1 post IC a, the collateral branch of post IC a and 2 ant IC a

In order, there is, from deep ->sup, the IC v, then a, then nerve = VAN OUT

Blood Supply of Thoracic Wall

Blood Supply of Thoracic Wall

Venous Drainage: Azygos system
Ant IC v:
IC 1-6 –> int thoracic v
IC 7-11 –> musculophrenic v

Post IC v:

(R) –> azygos v
(L) –> hemiazygos v inf, accessory hemiazygos v superiorly
both hemiazygos can flow into azygos, crosses midline @ T8
or acc. hemiazygos v can flow into hemiazygos, or angulus venosus

Nerves of IC spaces:
11 pairs of nerves, + subcostal n

IC 1-3n = Intercostobronchial n
IC 4-6n = Thoracic n
IC 7-12n = Thoracoabdominal n

originate from ventral rami of Thoracic spinal n

supply sk m, skin,
carry autonomic innervation to sweat glands, cutaneous vessels, hair follicles

Br of IC n

  1. Lat cut br – pierce int/ext IC m on lat side, has ant/post br => skin of lat thoracic and ab wall
  2. Ant cut br – pierce m @ parasternal line, had med/lat br => skin of ant thoracic and ab wall
  3. Collateral br – aid  w/ IC m supply
  4. white/gray br for SNS trunk (rami communicantes) => SNS trunk on same ggl –> desc br => a/v, sweat glands, smooth m
  5. Musc br for m => IC m, subcostalis m, transv thoracis m, levator costarum, serratus post m

Each spinal n supplies
1 dermatome
1 myotome
1 sclerotome

CLINICAL NOTE: Thoracic puncture
Necessary when pleural cavity fills w/ fluid or air
done @ phrenico-costal sinus b/w post axillary & scapular line in 10th and 11th IC spaces
b/w lower margin of upper rub & upper margin of lower rib

Nerve Supply of Thoracic Wall

Nerve Supply of Thoracic Wall

Lymph Drainage of Thoracic Wall:

All of the lymphatic drainage of the thorax is directed toward the bronchomediastinal trunks, thoracic duct, and descending intercostal lymphatic trunks, but the actual lymphatic trunks themselves are highly variable.

The thoracic duct extends from the abdomen to the neck, where it ends in one of the large veins

  • It begins as either a plexus or a dilatation called the cisterna chyli,
  • passes through or near the aortic opening of the diaphragm
  • ascends in the posterior mediastinum between the aorta and the azygos vein.
  • Next it crosses obliquely to the left, posterior to and then along the left side of the esophagus.
  • Finally it passes posteiror to the left subclavian artery, enters the neck (where it forms an arch above the level of the clavicle),
  • ends in the left internal jugular vein
  • The thoracic duct receives the left subclavian and jugular trunks and often the left bronchomediastinal trunk.

CLINICAL NOTE: Most of the lymph in the body reaches the venous system by way of the thoracic duct, but anastomoses are so extensive that no serious effects result if the thoracic duct is ligated.

On the R  side, the bronchomediastinal trunk forms various combinations with the subclavian and jugular trunks.

all three unite to form a right lymphatic duct, which then empties directly into the junction of the internal jugular and subclavian veins.= R angulus venosus

Flow of Thoracic Lymph Drainage, starting from abdomen

Flow of Thoracic Lymph Drainage, starting from abdomen


General Info:
Location = 2-6th ribs, parasternal line –> midaxillary line

  • Breast bed = rests in deep pectoral fascia (2/3), other (1/3) in fascia over serratus ant m
  • b/w the 2, loose CT = retromammary space
  • held to skin w/ retinacula cutis via suspensory lig (of Cooper) –> support tubules of glands
  • has nipple surrounded by pigmented circular area = areola
    • nipple has no fat, hair, sweat glands, only smooth m, in circular layers
  • has a tail portion (of Spence), that runs towards the axillary region

Mammary glands:

  • in subcut. tissue over the pectoral m.
  • are modified sweat glands , no capusle or sheath
  • lacitferous ducts have 15-20 lobules – run towards the nipple to open there
  • below areola, ducts dilated to form lactiferous sinus, where milk collects
  • enlarge in pregnancy
  • Areola –> have sebaceous glands that inc in # pregnancy, secrete oil to protect nipple from irritation

Blood supply:

  • int thoracic a
    • med mammary br (perforating br)
    • ant IC br
  • axillary a
    • lat thoracic a
    • thoraco-acromial a
  • Post IC a = 2,3,4 IC spaces

Venous Drainage
: axillary v, int thoracic v

Nerves of Breast

  • ant & lat cut br of 4-6 IC n
  • sensory to skin of breast (SS)
  • SNS to a/v of breast & smooth m of skin & nipple

Lymph Drainage

  1. Subareolor l.n. nipple, areola, gland lobules
  2. Axillary l.n = lat quadrants
    • pectoral l.n.
    • interpectoral l.n
    • deltopectoral l.n
    • supraclavicular l.n.
    • inf deep cervical l.n.
  3. Parasternal l.n. = med quadrants –> can go opposite breasts
  4. Interpectoral l.n. = upper quadrants –-> supraclavicular l.n.
  5. Subdiaphragmatic l.n. = inf phrenic
    • Clavicular –> subclavian lymph trunk –> angulus venosus + jugular lymph trunk
    • bronchiomediastinal trunk –> jugular l.n
    • Jugular lymph trunk –> (L) thoracic duct, R lymph duct

Histology: The histology of the mammary gland.

Embryology: The formation and differentiation of the extraembryonic mesoderm.

  • Develops from epiblast (yolk sac cells) and consists of loosely arranged cells – new cell population forms b/w inner and outer surface of cavity
  • layer fills space b/w exocoelemic membrane & cytotrophoblast
  • Large spaces develop in extraembryonic mesoderm, and group to form extraembryonic coelem
  • Extraembryonic coelem splits mesoderm into somatic & visceral mesoderm
    • Somatic mesoderm lines trophoblast, forms connecting stalk, and covers amnion
    • Visceral mesoderm covers yolk sac
  • Syncytiotrophoblast & cytotrophoblast & somatic mesoderm together forms chorion
  • Embryonic coelem = chorionic cavity – surrounds the primitive yolk sac and amniotic cavity, except where the germ disc is connected to the trophoblast/embryoblast by connecting stalk

14. The pleura and pericardium. Bone formation. Formation of the blastocyst and the bilaminar germ disc.

14 Dec

14. The pleura and pericardium. Bone formation. Formation of the blastocyst and the bilaminar germ disc.

Flash cards:

Pleura 1

Pleura 1

Pleura 2 - reflections

Pleura 2 - reflections

Pericardium 1

Pericardium 1

Pericardial reflections

Pericardial reflections

Anatomy:  The pleura and pericardium.


  • serous membrane covering the Lung
  • Double layer:
    • Inner visceral – covers lung itself
    • Outer parietal -covers inner surface of thoracic wall
  • B/w 2 layers = Pleural cavity – 4 ml of serous fluid
  • Function:
    • lubricates the 2 pleural surfaces
    • allows layers of pleura to slide smoothly over each over during respiration
    • surface tension allows lung surface to stay touching thoracic wall
    • Creates a seal b/w 2 pleural surfaces
  • The two layers combine around the root of of the lung – so the root of lung has no pleural coverage, the layers combine to form the pulmonary ligament, which runs inf and attaches the root of the lung to the diaphragm
  • CLINICAL NOTE: When parietal pleura is punctured, lungs collapse due to air rushing (air pressure higher outside than in) = pneumothorax

Pleural surfaces and recesses

Pleural surfaces and recesses

Parietal Pleura – senses PAIN, lines inner surface of thoracic wall
4 parts:

  1. Cupula pleura (aka cervical pleura) – part of pleura which project above clavicle
    • located w/in scalenus tent
    • strengthened by a layer of endothoracic fascia call the suprapleural membrane = Sibson’s fascia
  2. Diaphragmatic pleura – faces domes of diaphragm inf
    • , also separated from diaphragm via endothoracic fascia,
    • only attached to lateral sides of diaphragm
    • as central tendon of diaphragm attaches to pericardium
  3. Sternocostal pleura – attaches to rib and sternum
    • separated from ribs via a part of endothoracic facsia called phrenicopleural fascia
  4. Mediastinal pleura – faces vert column and midline space b/w two areas of pleura = mediastinum

3 Pleural reflections: Lines where the surfaces of parietal pleura meet each other

  • Sternal line = costal –> mediastinal (ant)
  • Costal line = costal –> diaphragmatic (inf)
  • Vertebral line = costal –> mediastinal (post)

* first 2 have a sharp,defined border, the last is a gradual rounded border

Nerve supply:

  • IC n (sternocostal pleura, and peripheral part of diaphragmatic pleura)
  • Phrenic n (central diaphragmatic pleura, and mediastinal pleura)

Blood supply
= Int thoracic a, post IC, sup phrenic a, sup IC a

Visceral Pleura – sensitive to STRETCH, lines lung ext and dips into all fissures
Nerve supply = contains vasomotor fibers and sensory ending of CN X for respiratory reflexes

Blood Supply = bronchiol a, pulmonary v

Surface Projection:

  1. Lat –  lat wall thorax = lat wall of pleura
  2. Sup = Cupula Pleura= dome of pleura,
    • projects into neck
    • above neck of 1st rib
    • 2 cm above clavicle @ med end
    • middle 1/3 clavicle b/w midclavicular line and midline
  3. Med border:
    • R – R sternoclavicular joint –> desc to lower border of R 6th rib
    • L – goes toward midline from apex, but never reaches it, follows the lung and desc down to 4th rib, runs a bit laterally and then comes back towards midline @ 6th rib, to form the pleural cardiac notch
  4. Inf border
    • @ parasternal line – inf border crosses border of 6th/7th rib
    • @ midclavicular line – inf border crosses 8th rib
    • @ mid axillary line – 10th rib
    • @ paravertebral line – T12, 11th rib
Surface Projection of Pleura

Surface Projection of Pleura

Pleural recesses:
If you notice, the surface projection of pleura is larger than the surface projection of the lung itself.

In between parietal pleura, are a series of recesses:

  1. Costo-mediastinal recesses – vertical in direction, costal & mediastinal pleura meet
  2. Phrenico-mediastinal recess – ant-post direction, b/w mediastinal & diaphragmatic pleura
  3. Costo-diaphragmatic recess – b/w costal & diaphragmatic pleura
    • largest of the 3, horseshoe shaped,
    • accumulates fluid when standing
    • potential space that allow lung to expand into them when inhaling
    • can collect sample of pleural fluid from here
    • deepest point of sinus is @ mid-ax line where space b/w lung and pleura = 12 cm, or 4 fingers

Pleural Recesses

Pleural Recesses

strong fibrous layer, double walled sac w/ heart w/in
originates from intraembryonic somato and splanchno pleura

Layers of Heart itself: (sup –> deep)

  1. Fibrous pericardium
    • bound to central tendon of diaphragm for deep inspiration,heart follows diaphragm, so heart is more vertical,
    • in deep expiration, heart rises due to upward movement of diaphram – heart is more horizontal
  2. Serous pericardium
    • Has a parietal layer – stong dense reg CT, prevent heart from over dilating
    • Visceral layer – simple squamous epithelium (mesothelium), that lines the heart itself aka Epicardium
    • B/w 2 layers = Pericardial cavity
  3. Subepicardial CT
  4. Myocardium – muscular wall – striated cardiac m
  5. Subendocardial CT
  6. Endocardium – simple squamous epithelium (endothelium), same epith as blood vessels

Layers of Pericardium

Layers of Pericardium

Pericardium moves along w. movements of structures around it b/c:

  • fused w/ tunica adventia of great vessesl entering/leaving heart
  • attached to post surface of sternum by sternopericardial ligaments
  • fused w. central tendon of diaphragm

Blood supply = mostly from pericardiophrenic a (int thoracic a) musculophrenic a (int thoracic a), bronchiol, esophageal, sup phrenic a (thoracic aorta), coronary arteries

= phrenic n (C3-C5), vagus n (CN X), SNS trunk

Reflections of pericardium: where 2 layers of pericardium meet each other

  1. @ arterial endTransverse sinus
    • where pul a and aorta leave heart,
    • when doing surgery on aorta or pulmonary a, can stop circulation to this area by making a stitch through this sinus,
    • reach by reaching under pulmonary trunk and ant to SVC
  2. @ venous end – Oblique sinus =

    • where SVC,IVC pulmonary v enter heart,
    • reach via inserting finger under apex of heart and pushing up and right towards root of R lung

Development of Sinuses:

  • Form during embryonic life due to folding of embryonic heart tube
  • As heart tube folds, venous end moves posterior and up, so venous end then is up by arterial end, separated by transverse sinus
  • As veins of heart grow and expand, oblique sinus is formed, a recess, a blind sac behind post side of the heart,
Development of pericardium

Development of pericardium

Histology: Bone formation.

Embryology: Formation of the blastocyst and the bilaminar germ disc.


Blastocyst, labeled in English
Image via Wikipedia
  • fluid is secreted within the morula (16 cell) = blastocyst cavity
  • now called blastocyst, and has 2 distinct cell layers
  • inner cell mass = embryoblast –> is the future embryo
  • outer cell mass = trophoblast –> will form the placenta

Bilaminar Germ Disk

Bilaminar Disc Formation:

  • In the 8th day, the blastocyst has the inner cell mass & outer cell mass
  • Each cell mass  differentiated into 2 different cell layers
  • Trophoblast = outer cell mass splits into:
    • Cytotrophoblast – inner layer of mononucleated cells – distinct cell barriers
    • Syncytiotrophoblast – outer layer of mutlinucleated cells – no  obvious cell boundaries
    • cells are probably created in cytotrophoblast, and then migrate into syncytiotrophoblast
  • Embryoblast = inner cell mass – splits into:
    • Epiblast – layer of high columnar cells, next to amniotic cavity
    • Hypoblast – layer of small cuboidal cells, next to blastocyst cavity
    • small cavity forms in epiblast – is amniotic cavity , epiblast cells next to the cytotrophoblast = amnioblasts
    • Cells at periphery of hypoblast migrate over inner surface of cytotrophoblast – forming thin layer extraembryonic endoderm = Heuser’s membrane
    • Blastocyst cavity = is then called primitive yolk sac
  • Uterus endometrium has interstitial edema (increased interstitial fluid b/w cells), and increased # of a/v

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12. The blood vessels of the heart. Conducting system (innervation) of the heart The histology of blood vessels. The formation of granulocytes (granulocytopoesis).

12 Dec

12. The blood vessels of the heart. Conducting system (innervation) of the heart The histology of blood vessels. The formation of granulocytes (granulocytopoesis).

Anatomy: The blood vessels of the heart. Conducting system (innervation) of the heart

Arteries and Veins of Heart:

Coronary a – arise from asc aorta @ aortic sinuses – the bulges at the most proximal part of asc aorta

  • supply  the myocardium and endocardium of heart, both atria and ventricles
  • filled w/ blood during ventricle diastole
  • max blood flow = diastole
  • min blood flow = systole

Ventricles are covered w/ epicardial fat (deep to the epicardium)
blood vessels of heart embedded into the fat on the surface of heart
so musc receive blood from outside
therefore – CLINCAL NOTE – the musc just below endocardium is most susceptible to hypoxia

Blood cannot enrich subendocardial musc from inside the heart, b/w the endothelium covering inside of the heart forms non-penetrable barrier.
*Heart wall is covered by simple squamous epith, called endothelium*

There are no anastomosis w/in subendocardial musc arteries w/ other coronary a – so if a is blocked, the area it supply simply receives no blood.

Anastomosis do exit on the surface of the heart.

1. R coronary a – emerges from R aortic sinus, and turns R to run under R auricle, then to coronary groove –> gives off marginal branch –> turns to post side of heart (still in groove) –> when reaches the middle of posterior surface = gives post Intraventricular br, which descends down the back of heart and runs to apex

Branches of R coronary a:

  • SA nodal br
  • R marginal a
  • AV nodal br
  • Post IV a

Areas supplied by R coronary a:

  • SA node
  • AV node
  • R atrium
  • R ventricle except narrow strip @ ant intraventricular septum
  • the Post intraventricular septa

CLINICAL NOTE –  If nodal br to SA node blocked (whether from L or R coronary a) – will lead to arrythmia – ventricle contraction will be separated from atria = nodal delay

2. Left Coronary a – emerges from L aortic sinus, and runs L and under pulmonary trunk and then the L auricle of heart –> is shorter than right –> gives major anterior intraventricular br –> sends a branch around the coronary groove of heart as well = circumflex br & branch down the left margin of heart

Branches of L coronary a:

  • circumflex a
  • ant IV br (sometimes called desc br)
  • L marginal a
  • Lat diagonal br
  • sometimes will give the nodal br of SA node

Areas supplied by L coronary a:

  • L atrium
  • L ventricle
  • Ant IV septa
  • narrow zone of R ventricle by ant IV septa




Cardiac veins: 3 major, 1 minor v, cardiac sinus

1. Great cardiac v – begins @ apex of heart –> asc in ant IV groove –> coronary sinus, runs w. it in coronary groove, turns L

2. Coronary sinus – largest vein of heart, in coronary groove b/w atria and ventricles

  • opens into R atrium b/w IVC and tricuspid valve, covered by Thebesian valve
  • formed from the joining of great, middle, lesser cardiac v
  • Then, oblique vein of L atrium & post v of L ventricle flow into it

3. Middle cardiac v – runs from apex –> in post IV groove w/ post IV br of R coronary a

4. Lesser (small) cardiac v – originates from ant side of coronary groove, runs on R margin w/ marginal a of R coronary a

5. Oblique v of L atriumremnant of embryonic ant cardinal v, on post wall of L atrium, runs b/w the pulmonary veins, runs in an oblique (diagonal) direction –> coronary sinus

6. Ant cardiac v – originates from wall of R ventricle, bridges over coronary groove and opens directly into R atrium
drains R ventricle itself

7. Minimae cardiac veins (venae cordis minimae) – originate in walls of the chambers themselves and drain into each chamber directly. So each chamber has a little bit of venous blood flowing into it.


Lymph Drainage of Heart covered in topic #17

Conduction System of Heart: done in order of flow of signal

1. SA node – primary pacemaker of heart

  • located just deep to epicardium, @ junction of opening of SVC on crista terminalis
  • collection of specialized cardiac musc fibers
  • impulse = 70x a min
  • Blood supply: nodal br of R or L coronary a
  • Innervation: cardiac plexus
  • NOTE SNS = inc heart rate (HR), PNS = dec HR

2.AV node – secondary pacemaker of heart

  • located b/w tricuspid and opening of coronary sinus on intra-atrial septum
  • receives signal from SA node via muscle of heart
  • sends signal up walls of ventricle via AV bundles
  • Blood supply = AV nodal br of  R coronary
  • SNS = speeds up conduction, PNS = slows conduction

3. AV bundle – the only connection b/w the atria/ventricular myocardium conduction systems (remember that anulus fibrosus acts like an insulator b/w the two)

  • runs through anulus fibrosus & moderator band
  • inside inter-ventricular septum
  • divides in R & L bundle
  • same as Bundle of His, or bundles of Tawara

4. Purkinje fibers

  • are branches from R & L AV bundles
  • R bundle – stimulates (+) muscle in IV septum, ant papillary musc of R ventricle via moderator band and wall of R ventricle
  • L bundle – stimulates (+) IV septum, ant/post papillary musc and wall of L ventricle

Pathway of conduction:

  1. SA node starts signal that conducted via cardiac m fibers in atria, causing them to contract
  2. Impulse spreads via myogenic conduction that sends signal from SA node to AV node
  3. Signal from AV node –> AV bundle and its branches,
  4. R & L bundles –> run on each side of IV septum to supply walls of ventricles respectively and papillary m


Innervation of Heart itself:

  • rec Sup,Mid,Inf cervical and thoracic cardiac n from SNS trunk and CN X plexus
  • SNS = Made of the presynaptic fibers from T1-T5, and post synaptic fibers from cervical and stellate ggl of SNS trunk
  • PNS =  presynaptic fibers of CN X
  • have superficial and deep branches (beneath/behind arch of aorta)
  • SNS = Inc HR, force of contraction –> VD of coronary a (from lat horn of T1-5)
  • PNS = dec HR –> VC of coronary a (CN X)

Histology: The histology of blood vessels.

Embryology:The formation of granulocytes (granulocytopoesis).




11. The fibrous skeleton and chambers of the heart. The histology of the red bone marrow. Formation of red blood cells (erythropoesis).

11 Dec

1. The fibrous skeleton and chambers of the heart. The histology of the red bone marrow. Formation of red blood cells (erythropoesis).

Anatomy: The fibrous skeleton and chambers of the heart.

Heart – Fibrous skeleton & Chambers

Fibrous skeleton of Heart = anulus fibrosus
made of 4 rings, 2 trigones, 1 ligament


  • separates atria from ventricles
  • provides attachment of cusps of valves & myocardium (all musc originate and insert into it)
  • keep AV and semilunar valves open, but inhibits over distension
  • forms an electrical “insulator”, by separating the electric impulses of atria and ventricle, so they contract independently, and by surrounding and making a passage way through which AV bundles travel

Position of it can be shown on the external side of the heart as coronary groove (sulcus)

1. L fibrous ring – around bicuspid valve
2. R fibrous ring – around tricuspid valve
3. Pulmonary ring – pulmonary valve
4. Aortic ring – around aortic valve
5. R fibrous trigone – R fibrous ring + aortic ring
6. L fibrous trigone – L fibrous ring + aortic ring

Chambers of Heart: Will be doing this in order of blood flow

R atrium – receives de-O2 blood from systemic circulation via SVC, IVC
remember that 3 things enter the R atrium – SVC, IVC, coronary sinus
Structure to mention/identify:

  1. R auricle = sup/ant part of atrium, covers origin of R coronary a, has the pectinate m, which are ridges of myocardium that push up into endocardium
  2. Sinus venarum cavarum – smooth area where SVC, IVC enter the R atrium, as well as coronary sinus, and ant cardiac v.
  3. Crista terminalis – crest like line b/w rough part of atria (where pectinate m are), and smooth area – shown externally as sulcus terminalis
  4. Opening of coronary sinus –  a vein that receives most of v of heart itself, covered by Thebesian valve
  5. SA node – show this by crista terminalis as superior most point of sinus venarum cavarum, where SVC enters – is primary pacemaker of heart
  6. AV nodesecondary pacemaker of heart, show this by pointing to the area b/w opening of coronary sinus and R AV valve
  7. Fossa ovalis – show this on intra-atrial wall,

    • to find it – put thumb in R atrium, and forefinger in L atrium and pinch the intra-atrial wall
    • the thinnest part of this wall is fossa ovalis.
    • Or hold it up to the light, and this is where light shines thru the intra-atrial wall.
    • Remnant of foramen ovalis, an opening b/w 2 atria that existed in embryonic life
  8. Tricuspid valve – leading to R ventricle

R ventricle – receives blood from R atria, and pumps blood into pulmomary trunk –> lungs to be re-O2’d, major portion of ant surface of heart
Structures to identify/mention:

  1. Inflow limb – area that leads from R atria directly, where blood flows down, desc part of V in longitudinal section
  2. Outflow limb = infundibulum = conus arteriosus – asc part of V in longitudinal section – sends blood into pulmonary trunk
  3. Papillary m – show all 3; ant, post, septal – cone shaped m that attach to cordae tendinae, valves open when these contract
  4. Chordae tendinae – dense reg CT cords that run from papillary m –> each cusp of tricuspid,
    • NOTE – b/c action of valve opening is active, when m. not contracted, valve closes passively –> prevents blood from returning to R atrium
  5. Trabeculae carnae – ridges of myocardium that projects into endocardium
  6. Supraventricular crest – a ridge that separates inflow and outflow limb and also lifts septal cusp of tricuspid – remnant of ridge b/w bulbus cordis and primary ventricle
  7. Septomarginal traveculae- has moderator band – which carries Purkinje fibers to ant pap m, and interventricular septa from R limb of Bundle of His to sternocostal wall of ventricle,
  8. Moderator band – musc bundle that runs from inf part of IV septa to base of ant papillary musc. Look for it and show if you can.
  9. Interventricular septum – has both muscular/membranous part, wall b/w R & L ventricle, show membranous part just below pulmonary/ aortic valve.

    • To find membranous part of septum, again, put thumb in R ventricle and forefinger in L ventricle, and feel up to sup most part of interventricular septum.
    • The wall should feel thinner here – membranous part.
    • Like fossa ovale, this part will also have light shine through it.
    • This membranous part was where the ventricles were closed of by downgrowth of endocardial cushions in embryonic life
  10. Bundle of His = AV bundle = Tawara = located in lower part of IV septa, tertiary pacemaker
  11. Pulmonary valve – leads from outflow limb –> pulmonary trunk, show all three cusps; right, left, ant

L atrium – receives O2 blood from lungs via 4 pulmonary v (Remember from lung, that R lung has 3 pulmonary v, and L has 2, but R sup/mid pulmonary v combine, so only 4 pulmonary v enter heart)

  • pulmonary v have no valves
  • very capable of strong contraction
  • most posterior of the 4 chambers, makes most of diaphragmatic surface of heart
  • just anterior to esophagus

Structures to mention/identify:

  1. L auricle – sup/ant part of atrium, also has pectinate m, but less than R atrium, musc are active in atrial systole, covers origin of L coronary a
  2. Fossa ovale – can also be shown here, but shown better in R atria
  3. Smooth area of L atria – where 4 pul v enter
  4. Bicuspid valve – leading to L ventricle


L ventricle – receives O2 blood from L atria –> sends it to aorta

  • wall much THICKER than R, b/c has to pump blood out to entire system = 15 mm thick
  • divided into L ventricle proper & aortic vestibule (upper/ant portion of ventricle — leads to aorta)
  • longer, narrower and thicker than R ventricle

Structures to mention/identify:

  1. Papillary musc – only 2 here, one for each cusp of bicuspid valve cone shaped, m. that attach to cordae tendinae, valves open when these contract, also larger than R ventricle
  2. Chordae tendinae – dense reg CT cords that run from papillary m –> each cusp of bicuspid
  3. Trabeculae carnae – ridges of myocardium that projects into endocardium, many more than in R ventricle
  4. Aortic ventricle – sometimes called outflow part of L ventricle, area leading to aortic valve.
  5. Interventricular septum – has both muscular/membranous part, wall b/w R & L ventricle,
    • show membranous part just below pulmonary/ aortic valve.
    • To find membranous part of septum, again, put thumb in R ventricle and forefinger in L ventricle
    • and feel up to sup most part of interventricular septum.
    • The wall should feel thinner here =  membranous part.
    • Like fossa ovale, this part will also have light shine through it.
    • This membranous part was where the ventricles were closed of by downgrowth of endocardial cushions in embryonic life.

Histology: The histology of the red bone marrow.

Embryology: Formation of red blood cells (erythropoesis).



Erythropoiesis is the development of mature red blood cells (erythrocytes). Like all blood cells, erythroid cells begin as pluripotential stem cells. The first cell that is recognizable as specifically leading down the red cell pathway is the proerythroblast . As development progresses, the nucleus becomes somewhat smaller and the cytoplasm becomes more basophilic, due to the presence of ribosomes. In this stage the cell is called a basophilic erythroblast . The cell will continue to become smaller throughout development. As the cell begins to produce hemoglobin, the cytoplasm attracts both basic and eosin stains, and is called a polychromatophilic erythroblast . The cytoplasm eventually becomes more eosinophilic, and the cell is called an orthochromatic erythroblast . This orthochromatic erythroblast will then extrude its nucleus and enter the circulation as a reticulocyte . Reticulocytes are so named because these cells contain reticular networks of polyribosomes. As reticulocytes loose their polyribosomes they become mature red blood cells.


10. The absolute and relative dullness of the heart. Surface projection of the contour and valves of the heart. The histology of the blood. The formation of platelets, monocytes and lymphocytes (thrombopoesis, monocytopoesis, lymphopoesis).

10 Dec

10. The absolute and relative dullness of the heart. Surface projection of the contour and valves of the heart. The histology of the blood. The formation of platelets, monocytes and lymphocytes (thrombopoesis, monocytopoesis, lymphopoesis).

Anatomy: The absolute and relative dullness of the heart. Surface projection of the contour and valves of the heart.

Dullness of Heart:
Relative and absolute dullness of heart is related to percussion of the heart
Using fingers to tap on the chest wall, and listening to sound, one can approximate the size of the heart/lungs

Starting from lower L side of rib cage, tapping in a diagonal line towards upper R side:

The area where just lung is present – there is a resonant sound (like beating on a drum)

Area w/ Heart + lung = sound is relatively dull (compared to resonant sound)
now can estimate size of heart
Points where relative dullness begins = Surface projection of heart borders

  • SVC =  3rd R rib, next to sternum
  • R limit of coronary groove = 6th IC space, 2-3 cm R of sternum
  • Apex of Heart = 5th IC space, 9 cm left = also called location of Apex beat
    • Apex beat = pulse resulting from apex of heart being forced against ant thoracic wall when L ventricle contracts
  • L limit of coronary groove = left 3rd rib, 3 cm left

Area w/ just heart = sound is totally dull

  • Technically, where heart not covered by lung/pleura
  • Where heart has direct contact w/ ant thoracic wall (except for pericardium)

    • *Kind of like Space of Traube for stomach
  • usually you start hearing this b/w 4th & 6th rib, parasternally *on L side*

Location of resonant sound – location of absolute dullness = size of lung

– If you never hear absolute dullness, lungs are enlarged, and there is no point that the heart projects to surface w/o lung in front of it.

Relative vs Absolute dullness of heart

Relative vs Absolute dullness of heart

Auscultation Points of heart:

  • Where we listen for valves of heart,
  • NOTE – in order to not get confused, doctors like to listen for diff valves of the heart as far apart from each other as possible,
  • The sound of the valve closing is carried in the direction of blood flow in straight line.
  • For example, This is why we listen for biscuspid or L AV valve @ apex of heart, because flow of blood goes towards that directly from the AV valve.

Auscultation Points of valves:

  • Bicuspid valve = Apex, 9cm midline in L 5th IC space
  • Tricuspid valve = Sternal end, R 5-6 IC space
  • Aortic valve = sternal end, R 2nd IC space
  • Pulmonary valve = Sternal end, L 2nd IC space

(Sternal end, means the end of the rib that connects to the sternum, starting from the sterno-chondral joint of the rib.)

Auscultation points of heart - arrows show blood flow - so we know where we can listen

Auscultation points of heart - arrows show blood flow - so we know where we can listen

Surface Projections of Heart:
We project two parts of the heart onto the surface, the borders of the heart, as mentioned earlier, and anulus fibrosus (the fibrous “skeleton” of the heart)

Tip!! = Find a picture of heart sitting within ribs, and draw it yourself, you’ll never forget it.

Borders of Heart:

  • Sup = Convex line from inf border 2nd L cc –> sup border of 3 R cc
  • Right = convex line from 3 R cc –> 6th R cc
  • Inf = convex line from 6th R cc –> 5th IC space close to L midclavicular line
  • Left = convex 5th IC space close to L midclavicular line –>inf border 2nd L cc
X ray of Heart - need to know 4 test

X ray of Heart - need to know 4 test



Projection of Anulus Fibrosus:

  • Draw 2 convex lines connecting the lower R corner to upper L corner
  • You’ve just drawn a line from the R limit of the coronary groove to L limit of it.
  • These two lines are the surface projection of anulus fibrosus, which of course, has the valves of the heart in it
  • Remember,you show location of anulus fibrosus externally as coronary groove
  • *See next topic for more info on anulus fibrosus

From lower R corner to upper L corner, think logically about what valve is first. (picture a heart in hand, in anatomical position)

  1. R AV valve comes first, being most lateral and R of the valves
  2. Left AV valve is next, most lateral and L of the valves, deeper than both aortic and pulmonary valves
  3. Aortic valve comes next, leading from R ventricle – more superficial to the R AV valve
  4. Pulmonary valve is last, because pulmonary trunk is just L to asc aorta, and slightly deeper to it


Note there seems to be some discrepancy, because some sources have mitral valve as 2nd, and some as last.  I decided to stick w/ BRS book on this one. – B/c that is what I said on the 2nd SCT and he said it was right.  Rosa, however said that mitral valve was last.  I think you are safe as long as you say which is most R and most L and what is deeper and what is superficial.

Histology:The histology of the blood.

Embryology:The formation of platelets, monocytes and lymphocytes (thrombopoesis, monocytopoesis, lymphopoesis).



The mediastinum. The histology of the esophagus. Fertilization and cleavage.

9 Dec

The mediastinum. The histology of the esophagus. Fertilization and cleavage.

Inf Mediastinum

Inf Mediastinum

Sup Mediastinum

Sup Mediastinum

Anatomy: The mediastinum.

Superior Mediastinum:


  • ant = manubrium of sternum
  • post = T1-T4
  • lat = mediastinal pleura, 1st rib
  • sup = thoracic inlet
  • inf = line b/w sternal angle –> Intervertebral disk b/w T4,T5

Superficial Dissection of Superior Mediastinum

Superficial Dissection of Superior Mediastinum

1. Thymus – in youth only, mostly adipose in adults

  • lymphoid organ
  • gradually replaced w/ fat as an adult
  • produces T cells throughout life, but does T cell education during youth
  • Blood Supply =   ant IC & ant mediastinal br of int thoracic a, internal thoracic and inf thoracic v

2. Veins and phrenic n

  • L & R brachiocephalic v – formed by union of subclavian and internal jugular v = angulus venosus, combine to form SVC
    • L is 2x as long as left b/c has to cross many structure in midline to get to SVC – receives thoracic duct
    • R rec R lymphatic duct
  • SVC – will desc to enter R atrium @ 3rd cc, rec blood from all structures above diaphragm, except lungs and heart, is lat to trachea and asc aorta
  • Inf thyroid v
  • Int thoracic v
  • Phrenic n – supply diaphragm, SS, runs b/w subclavian a and origin of brachioceph v, will desc and run in front of root of lung on both sides

3. Arteries and vagus n (remember that vagus will run behind root of lung, and phrenic in front)

  • arch of aorta – originates @ 2nd R sternocostal joint @ level of sternal angle, and starts to desc @ 2nd L sternocostal joint
  • Brachiocephalic trunk – 1st branch of arch, ant to trachea and behind v – @ R SC joint, becomes R common carotid and subclavian a
  • L common carotid a – asc in carotid triangle
  • L subclavian a – runs behind L SC joint, w/ L common carotid
  • L & R vagus n

4. Trachea and Esophagus

  • Trachea – see topic # 8, divides @ sternal angle into R & L main bronchus
  • Esoph – fibromuscular tube that leads from pharynx –> stomach, runs b/w trachea and vertebral column, thoracic duct is left to it, runs down to pass thru esophageal hiatus in diaphragm

5. Prevertebral structures

  • Prevertebral M (see topic #4, ex/ longus capitis, longus colli, rectus anterior)
  • Post IC a/v/n
  • SNS trunk, white and gray branches
  • Azygos system
  • Thoracic duct (more on that in topic #16)

Deep Dissection of Superior Mediastinum

Deep Dissection of Superior Mediastinum

Inferior Mediastinum:

Inf Mediastinum – divided into ant, middle, posterior


  • ant = sternum, ribs
  • post = vert column
  • lat = mediastinal pleura
  • sup = line b/w sternal angle and intervertebral disk b/w T4,T5
  • inf = diaphragm

Anterior Mediastinum – b/w sternum and ant side of pericardium, larger in infants b/c of size of thymus

  • int thoracic a/v
  • ant IC a/v
  • Transverse thoracic m
  • Parasternal lymph nodes
  • sternocardial ligaments
  • Areolar CT

Middle Mediastinum
– w/in pericardium, see pericardium topics/heart

  • heart
  • last part of SVC
  • last part of IVC
  • Asc aorta
  • pulmonary trunk
  • terminal part of 4 pulmonary v
  • phrenic v
  • pericardiophrenic a/v
  • bronchiol a/v
  • bifurcation of trachea
  • R & L main bronchi

Posterior Mediastinum – post side of pericardium –> vertebral column
Step by Step showing of layers of Post mediastinum :

1. thoracic part of desc aorta – continuation of desc aorta, begins from inf border of T4,  and desc thru post mediastium, till it goes thru aortic hiatus of diaphragm @ about midline

    • surrounded by thoracic aortic plexus
    • behind root of lung, pericardium and esophagus

Branches of thoracic aorta:
has parietal and visceral branches

  • post IC – 3rd – 11th IC spaces
  • subcostal
  • sup phrenic – anastomose w/ musculophrenic, pericardiophrenic from int thoracic a


  • bronchial – 1 R, 2 L
  • pericardial – post wall of pericardium
  • esophageal – 4-5 br
  • mediastinal – supply lymph nodes and minor structures


2. Azygos system –
On R side:

Azygos v –  runs to R of T4-T12, arches of root of R lung –> empty into SVC

  • receives R post IC v, mediastinal v, esophageal v, R bronchial v
  • anatomosis w/ vertebral venous plexus
  • originates below diaphragm as asc lumbar v –> asc on R side of vertebrae –> diaphragm –> then called azygos v

On L side:

Hemiazygos v – collects L lower post IC v (7-12 IC v)

  • Hemiazygos crosses midline @ T6-T7 , joins azygos v –> SVC

Accessory hemiazygos v – collects L upper post IC v (1-6 IC v), rec bronchiol v on L side

  • joins hemiazygos v or runs sup to join brachiocephalic v

3. Esophagus:

  • pass post and R to arch of aorta
  • just behind L atrium
  • goes thru esoph hiatus of diaphragm @ T10
  • has impressions on it made by aortic arch, L bronchus, diaphragm

4. Vagus n
– desc lat to esoph on both sides

  • L & R recurrent laryngeal n –

    • R recurrent laryngeal hooks around R subclavian a,
    • L recurrent laryngeal desc and hooks around arch of aorta
  • Each contribute to esophageal and pulmonary plexus on each side, R vagus n also gives br to cardiac plexus
  • forms ant/post vagal trunk after diaphragm b/c will run ant/post to esophagus in this area, instead of lateral

Br of vagus n:

  • recurrent laryngeal n
  • pulmonary plexus
  • esophageal plexus
  • cardiac n
  • Vagus runs w/ esophagus in inf mediastinum

5. Thoracic duct – details in topic # 16

6. Posterior mediastinal & paraaortic l.n

7/8. Nerves of Post mediastinum:

  • Thoracic part of SNS trunk – cont w/ cervical & lumbar SNS trunk
  • Greater/Lesser/Least splanchnic n – supply viscera below diaphragm, have presynaptic fibers from 5th -12th SNS ggl, synapse w/ ggl in abdomen

9. Other structures:

  • 4-11th post IC a/v
  • 4-11th IC n
  • Subcostal a/v/n


Histology of the esophagus.

Embryology: Fertilization and cleavage.


  • occurs in ampulla of uterine tube, close to ovary
  • @ ovulation, sperm again are motile (they sit in the ovarian tube)
  • Before fertilization = sperm has to go through a few reactions:
    • Capacitation – epithelial interaction b/w sperm and mucosal surface of tube –> glycoprotein coat removed, plasma protein removed from plasma membrane over head of sperm
    • Acrosome reaction – after binding to zona pellucida, zona proteins induce the release of enzymes to help the penetration

Phases of Fertilization:

Penetration of Corona Radiata:

  • aided by action of sperm & uterine tube mucosal enzymes

Penetration of Zona pellucida:

  • Zona = glycoprotein shell around egg
  • The Zona induces acrosome reaction –> release of enzymes = acrosin
  • Permeability of zona pellucida changes when head of sperm come in contact w/ oocyte
  • sperm contact w. cell membrane of secondary oocyte = cortical reaction –> release of cortical granules from oocyte cytoplasm  –> this inhibits sperm penetration
  • zona pellucida & oocyte membrane = impermeable to other sperm

Fusion of sperm & oocyte:

  • both membranes bind and then breaks down near the fusion area
  • the entire sperm enters the cytoplasm of secondary oocyte
    • mitochondria and tail degenerate
    • sperm nucleus = male pronucleus
  • secondary oocyte completes meiosis II –> mature ovum
  • ovum nucleus = female pronucleus


  • series of mitotic divisions = blastula = 2 cell –>4 –> 8 of blastomeres = totipotent
  • formation of morula by undergoing compaction
  • tight junctions form between cells in  outer cell mass
  • inner cell mass is connected via gap junctions
  • this separates inner and outer cell mass from each other

9. The valves of the heart. The histology and development of the heart.

9 Dec

9. The valves of the heart. The histology and development of the heart.

Anatomy: The valves of the heart.

Valves of Heart
all of valves of heart originate from anulus fibrosus
2 valves on arterial end and 2 valves at AV Jxn

View of valves @ level of anulus fibrosus

View of valves @ level of anulus fibrosus

Semilunar valves

  • made of 3 semilunar cusps
  • NOTE – Pumonary valve has an R, L, and ant cusp & Aortic valve has a R,L, and post cusp —> So it is always P & A – Pulmonary has Ant, and Aortic has Post
  • Each cusps has a pars flaccida, and a pars tecta
  • The side of each cusp, thin CT area = lunule
  • peak of every cusp, fibrous = nodule
  • When valve closes, the lunules and nodules meet in the center.

Pulmonary Valve:

  • @ border b/w conus arteriosus of R ventricle & pul trunk
  • has an ant, R, L cusps
  • opened in ventricular systole & shuts after aortic valve closes
  • SP = behind med end of L 3rd costal cartilage & sternum connects there
  • Auscultation Point = heard best @ L 2nd IC space, just lat to sternum
  • each cusp is concave from superior view, project into pul trunk, but flatten against wall when blood is flowing through
  • cusps open up when they close, and catch backflow and prevent blood from going back into R ventricle
  • just above each cusp of valve, pul trunk bulges out, forming the pulmonary sinuses – these prevent cusps from sticking to the walls of the pulmonary trunk.

Aortic Valve:

  • b/w L ventricle and asc aorta
  • has R,L, post cusps
  • each cusp is concave from superior view, project into ascending aorta, but flatten against wall when blood is flowing through
  • cusps open up when they close, and catch backflow and prevent blood from going back into L ventricle
  • just above each cusp of valve, asc aorta bulges out, forming the aortic sinuses – these prevent cusps from sticking to the walls of the pulmonary trunk.
  • R&L coronary a originate from the aortic sinuses above R&L cusps
  • Post cusp’s sinus does not have an a. originate from it
  • blood pumped into coronary a in diastole
  • SP = behind L 1/2 sternum @  3rd IC space
  • Auscultation Point = heard best @ R 2nd IC space, just lat to sternum
  • closed during ventricular systole
  • 2nd Heart sound
Parts of Semilunar/Cuspid Heart valves, showing lunules, nodules, etc

Parts of Semilunar/Cuspid Heart valves, showing lunules, nodules, etc

Cuspid Valves

3 main structures:

  1. Cusps w/ core of CT
  2. papillary m (emerging from myocardium) –  cone shaped m that attach to cordae tendinae, valves open when these contract
  3. chordae tendinae – threads of dense reg CT connecting papillary m w/ cusps of valve
Location and Parts of cuspid valves

Location and Parts of cuspid valves

Tricuspid Valve = R AV valve

  • B/w R atria & R ventricle
  • SP = opposite 4th IC space, covered by endocardium
  • Has Ant, Post, Septal cusps = Ant works the most!
  • closed during ventricular systole ( contraction)
  • Auscultation Point = heard best @ R lower sternum body

Bicuspid valve = mitral = L AV valve:

  • b/w L atria and ventricle
  • SP = behind L 1/ sternum @ 4th costal cart
  • has Ant cusp & smaller post cusp
  • closed @ onset of ventricular systole
  • Ausculation point = heard best @ L 5th IC space @ midclavicular line

Mechanism of contration:

  1. Papillary m contract during ventricular systole, wall of ventricle, contracts and shorten, cusps stay closed
  2. If no contraction occurs, chords will relax, cusps flip open to atria
  3. If pap m. shorten too much, chordae pull down cusps, and they will open during diastole
  4. NOTE – b/c action of valve opening is active, when musc not contracted, valve closes passively, and shape of each cusp stops backflow back into atria

Histology: Histology of the heart.

Embryology: development of the heart.

Anim 1 = Early Heart and Primitive Heart Tube Folding

Anim 2 = Overview of Heart Tube Folding and Early Heartbeat

Anim 3 = Interatrial Septum Development

Anim 4 = Division of the Atrioventricular Canal

The primordium of the heart forms in the cardiogenic plate located at the cranial end of the embryo. Angiogenic cell clusters which lie in a horse-shoe shape configuration in the plate coalesce to form two endocardial tubes. These tubes are then forced into the thoracic region due to cephalic and lateral foldings where they fuse together forming a single endocardial tube.

The tube can be subdivided into primordial heart chambers starting caudally at the inflow end: the sinus venosus, primitive atria, ventricle, and bulbus cordis.

The heart tube begins to grow rapidly forcing it to bend upon itself. The result is the bulboventricular loop. Septa begin to grow in the atria, ventricle and bulbus cordis to form right and left atria, right and left ventricles and two great vessels- the pulmonary artery and the aorta. By the end of the eighth week partitioning is completed and the fetal heart has formed.


8. The anatomy and histology of the trachea and lung. The development of the respiratory tract.

8 Dec

8. The anatomy and histology of the trachea and lung. The development of the respiratory tract.

Lung - Parts, surfaces, a/v

Lung - Parts, surfaces, function, a/v

Lung - Parts, Impressions

Lung - Parts, Impressions

Lung - lymph, nerves, development

Lung - lymph, nerves, development

Lung 2 - development, action

Lung 2 - development, action

Anatomy of the trachea and lung


fibrocartilaginous tube supported by incomplete hyaline cartilage rings
back of ring is completed by trachealis m
Location: from lower end of larynx @ C6 –> Sternal angle @ border b/w T4-5, in superior mediastinum


lat to trachea = common carotid a, lobes of thyroid glands,
below the thyroid isthmus = jugular arch, inf thyroid v
R to trachea = brachicephalic thrunk

Trachea bifurcates @ level of sternal angle
R bronchus – wider, shorter and runs more vertically than L
L bronchus – passes inf to arch of aorta and ant to esophagus and thoracic aorta



Surface Projection:

R lung:

  • Apex @ parasternal line , 2 fingers above clavicle
  • descends till body of 5th rib, then runs lat to make inf border

L lung:

  • Apex @ parasternal line , 2 fingers above clavicle  (Instead of parasternal line, some would prefer that you say,1/3 of the way b/w midline and mid clavicular line)
  • @ 4th rib, goes a littl lateral , and then comes back towards midline @ 6th rib = cardiac impressions

Inf border of both lungs:

  • parasternal line = top of 6th rib
  • @ midinguinal line = bottom of 6th rib
  • @ant axillary line = body of 7th rib
  • @ mid axillary line = body of 8th rib
  • @post axillary line = body of 9th rib
  • @ para vertebral line = 11th rib

Function: major organs of respiration
Musc = Diaphragm, Ext/Int/Innermost IC m, SCM, Levator scapulae, Serratus Ant, Scalenus m, Pectoral Major & Minor, Levator costarum, Serratus Post sup m

1. Diaphragm contracts (inc vert diameter of thorax)
2. Pleural cavity & lung expands – dec intrapulmonary pressure (neg) –> air rushes into lungs passively as result of atmospheric pressure
3. Forced inspiration – involves contraction of IC m & elevation of ribs (superiolat movement) w/ sternum moving ant (bucket handle movement), Ribs move up and ant –> results in inc transverse and antero-post diameteres of thoracic cavity

Ab volume is decreased as ab pressure is increased

Musc = m of ant ab wall, int IC m, serratus post inf m
1. Overall process – involves relaxation of diaphragm, int IC m, and other m
dec in thoracic volume, inc in intrathoracic pressure, Ab pressure decreased & ribs depressed
2. Elastic recoil of Lungs – produces subatmospheric pressure in pleural cavities –> much of air is expelled
3. Forced Expiration – contraction of ant ab m and int IC m

* Quiet inspiration results from movement of diaphram mainly,
* Quiet expiration is passive process caused by elastic recoil of lungs

Apex – projects into scalenus tent, 1-2cm above clavicle, poorly ventilated
Base – rest on diaphragm, lowers in inspiration, rises in expiration
Root – place where a/v/n, main bronchi enter lung, one place NOT covered by pleura

  • = main bronchus, pul a/v, bronchial a/v,lymph vessles, Hilus lymph nodes, Pulmonary plexus
  • root of lung w/in sleeve of pleura = mesopneumonium (mesentary of lung),
  • unites around root to form pulmonary ligament, that runs inferiorly and attaches to the diaphragm

1. Costal surfaces – faces the ribs, sternum, costal cartilages, intercostal m

  • has costal pleura b/w it and ant thoracic wall,

2. Mediastinal surfaces – faces the pericardial sac, and vertebral bodies

  • Has a # of impressions on this surface made by structures b/w lungs
  • R Lung has 10 impressions: R subclavian a, Brachiocephalic truck, 1st rib, Thymus, Groove for azygos v, cardiac impression, groove for IVC, trachea, esophagus, partially the aorta
  • L Lung has 7 impressions: L subclavian a, L Brachiocephalic v, 1st rib, Trachea, Esophagus, Thymys, arch of Aorta,
Impressions of R lung

Impressions of R lung

Impressions on L Lung

Impressions on L Lung

3. Diaphragmatic surfaces – inf surface, rest upon the diaphragm

  • The R lung has deeper impression, due to the dome of diaphragm on R side being higher w/ liver underneath it.

R Lung has 3 lobes, and L lung has 2 lobes
The 3 lobes of R are made of the horizontal and oblique fissure, and the L has just the oblique fissure

The anatomical, functional and structural unit of the Lung = BronchoPulmonary Segment
each BP segment has:

  • a tertiary bronchus,
  • segmental br of pul a/v,
  • bronchiol a
  • pyramid structure w/ apex facing root, and base facing external surface
  • surgically removable w/o disrupting surrounding tissue

Pul acinus – structural unit w/ alveolar sac of 1 terminal bronchiole

Blood Supply of Lung:
Vasa Publica – pul a/v, called the respiratory circuit = CO2/O2 exchange

  • Pul Trunk = BP < aorta, covered by pericardium, extends from infundibulum of R ventricle = conus arteriosus
  • R pul a – behind asc aorta & SVC and ant to R bronchus
  • L pul a – connected to aorta via ligamentum arteriosum, remnant of ductus arteriosus, & shorter, narrower than R pul a
  • Pul v – intersegmental in drainage, leave lung as 5 pul v (1 for each lobe), but R upper & middle join so only 4 –> heart

Vasa Privata – bronchiol a/v, called the systemic circuit = supply viscera of lung itself

  • Bronchiol a – O2 –> visceral lungs & pleura,
  • connects to pul a that arises from aorta,
  • L bronchiol a from thoracic aorta
  • R bronchiol a from sup/post IC a, thoracic aorta, or L bronchiol a
  • Bronchiol v – rec blood from larger subdivisions of bronchi
    • drains to azygos v on R side, and acc hemiazygos, and hemiazygos on L side.
    • Acc hemiazygos –> hemiazygos v
    • The azygos system drains into SVC

Lymph Drainage:
Drains in 2 directions:
1. Superficial (Subserosal) lymph vessels = Superficial lymph plexus

  • drain surface and regions close to surface
  • runs on surface, deep to visceral pleura
  • –> bronchopul lymph nodes

2. Deep (Pericanalicular) lymph vessels = Deep lymph plexus

  • drain lymph from deep parts of lung
  • run along bronchiol tree
  • drain –> (Intra)pulmonary l.n. –> bronchopul lymph nodes

1. Pulmonary nodes –> 2 Bronchopulmonary –> 3. Sup/Inf tracheobronchiol nodes –> 4. Paratracheal nodes –> 5. Bronchomediastinal nodes & trunks @ birfucation of trachea

On R side –> R lymph duct
On L side –> Thoracic duct
Both empty in respective angulus venosus

Nerve Supply:
Pulmonary plexus – aff/eff fibers (PNS pre ggl) from CN X br, SNS post ggl fibers from SNS trunk, & cardiac plexus
Ant pul plexus = in front of root of lung
Post pul plexus = lies behind root of lung
br w/ blood vessesl & bronchi into lung

PNS – Eff = VM to bronchiol smooth m = Broncho-constrictor, bronchiol glands = secretomotor, Inhibitory to pul a/v = VD
Runs to:

  • Bronchiol mucosa – cough reflex
  • Bronciol m – stretch receptors
  • Interalveolar CT – Herring -Breuer reflex
  • Pul a as baroreceptors
  • Pul v as chemoreceptors

SNS – from SNS trunk
(-) Inhibitory for bronchiol m = broncho dilators
motor to pul a/v – VC
(-) Inhibitory for glands of bronchiol tree (type II epith cells)

Histology of the trachea and lung.

Development of the respiratory tract.


  • Int lining from endoderm, as well as the laryngeal epithelium & glands
  • musc & cartilage from 4th & 6th pharyngeal arch = thyroid, cricoid, arytenoid cartilages – therefore innervated by CN X
    • superior laryngeal n – above the vocal fold
    • recurrent laryngeal n = below the vocal fold
  • @ wk 4, on the ventral side of the primitive gut, a pocket forms that bulges out from the gut = laryngotracheal diverticulum
  • distal end of diverticulum to form lung bud
  • then, 2 folds of tracheo-esophageal folds, push medially and push together to midline to form a wall “septum”
    • ant (ventrally) = laryngealtracheal tube
    • post (dorsally) = esophageal tube


  • endoderm = epith + glands
  • mesoderm = smooth m, CT , cartilage

Bronchial/ Lung development:

  • from the lung bud –> forms 2 bronchiol buds
  • wk 5 = primary bronchi
  • primary bronchi –> branch into secondary (3 on R, 2 on L) –> branch into tertiary (10 on R, 8-9 on L), which become bronchopulmonary segment
  • these branches will expand into area  on either side of the foregut = primitive pleural cavity (or before that, pericardiocanal)
  • visceral mesoderm = visceral pleura
  • somatic mesoderm = parietal pleura

Phases of Development:

1. Glandular phase (5-16 wk)

  • branching continues
  • no respiratory bronchioles or alveoli
  • future airways are narrow with little lumens and a pseudostratified squamous epithelium.
  • embedded within a rapidly proliferating mesenchyme.
  • The structure has a glandular appearance.

2. Canalicular phase (13/16 – 26 wk)

  • beginning of respiratory bronchiole formation
  • primitive alveoli begin to form (terminal sacs)
  • Increased # a/v & capillaries start forming =extensive angiogenisis within the mesenchyme to form a dense capillary network.
  • Diameter of the airways increases with a consequent decrease in epithelial thickness to a more cuboidal structure.
  • Terminal bronchioles branch to form several orders of respiratory bronchioles.
  • Differentiation of the mesenchyme progresses down the developing respiratory tree, giving rise to chondrocytes, fibroblasts and myoblasts.

3. Terminal Sac phase (wk 24/26 – birth)

  • terminal sacs form
  • capillaries branching forming around terminal sac
  • # sacs and a/v increased enormously
  • Continued thinning of the stroma brings the capillaries right next to alveoli
  • Functional type-II pneumonocytes differentiate via several intermediate stages from pluripotent epithelial cells in the prospective alveoli.
  • Type I pneumonocytes differentiate from cells with a type-II like phenotype.
  • These cells then flatten, increasing the epithelial surface area by dilation of the saccules, giving rise to immature alveoli.
  • Type I & II pneumocytes seen – beginning of Blood brain barrier

4. Alveolar phase (wk 28/29 – 8 yrs)

  • mature alveoli continue to form till well developed
  • continue into childhood
  • Mature Blood Air Barrier forms