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