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. 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

Anatomy: Lymphatic dranaige of thoracic organs. The diaphragm.

Lymph Drainage of Thoracic Organs:

Lung:

• 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

Thymus:
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

Diaphragm:

• 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

Topography:
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

Diaphragm:

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
  

Topography:

• central tendon attaches to pericardium via pericardiophrenic ligaments
  

Origin:

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

Insertion:

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

Function: major musc of inspiration/expiration

Actions:
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

Histology: The histology of the skin.

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

Implantation

• 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

Trophoblast

• 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)

Placenta

• @ 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

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

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

Flash cards:

Pleura 1

Pleura 2 - reflections

Pericardium 1

Pericardial reflections

Anatomy:  The pleura and pericardium.

Pleura:

• 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

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

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

Pericardium.
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

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

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

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

1. @ arterial end – Transverse 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

Histology: Bone formation.

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

Blastocyst

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