Tag Archives: extraembryonic coelem

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