thoracic embryology

Question 1

septum transversum

Answer 1

a thick plate derived from splanchnic mesodermal tissue between the thoracic cavity and the stalk of the yolk sac, when cranial end grows and curves, it is located between primitive thoracic and abdominal cavity, opening between these cavities are mostly closed with growth of lungs, remaining canals are closed with growth of pleuroperitoneal folds

Question 2

mesenchyme

Answer 2

a type of tissue characterized by loosely associated cells that lack polarity

Question 3

pleuropericardial folds

Answer 3

projections from the thoracic cavity and contain common cardinal veins and phrenic nerves, they grow inwards taking these structures with them (phrenic nerve is brought both to fibrous pericardium and diaphragm) and creating pericardial cavity and two pleural cavities, in the adult they become the fibrous pericardium

Question 4

pleuroperitoneal folds

Answer 4

outgrowths that fuse with mesentery of esophagus and septum transversum closing off peritoneal cavity from pleural cavities

Question 5

formation fo diaphragm

Answer 5

septum transversum forms the central tendon of diaphragm, with components of pleuroperitoneal membranes, myoblasts from C3-5 (phrenic nerve), body wall mesoderm and mesentery of esophagus (cura)

Question 6

congenital diaphragmatic hernia

Answer 6

faliure of one or both pleuroperitoneal membranes to close the pericardioperitoneal canals allowing abdominal viscera into thorax

Question 7

endocaridal tube

Answer 7

is formed by vasculogenic cell clusters found in the lateral plate mesoderm in the caudel region around cranial neuro folds, which induce underlying endoderm to form myoblasts and blood islands (future blood vessels), they unite forming horse-shoe shaped tube surrounded by myoblasts later becoming the pericaridal cavity

Question 8

dorsal aortae

Answer 8

formed at same time as cardiogenic region formation, by other blood islands appear bilateraly, parallel and close to midline

Question 9

formation and position of heart tube

Answer 9

initially cardiogenic area is anterior to oropharyngeal membrane and neural plate, with closure of neural tube and growth of cns causes folding and cardiogenic area moves to thoracic region, lateral folding occurs at same time and caudal region forms paired cardiac tube

Question 10

dorsal mesocardium

Answer 10

initially attaches the developing heart tube to the dorsal side of the pericardial cavity, with further development it disappears creating the transverse pericardial sinus which connects both sides of the pericardial cavity

Question 11

structure of heart tube

Answer 11

1)endocardium forming the internal endothelial lining of the heart 2) myocardium forming the muscular wall, and 3)epicardium forming outside layer of tube and derieved from septum transversum and heart tube mesothelial cells

Question 12

fusing of heart tube

Answer 12

with lateral folding, endocaridal heart tube fuses forming atrium, ventricle, and bulbus cordis, most caudel region does not fold and forms aortic roots

Question 13

formation of cardiac loop

Answer 13

as cardiac tube continues to grow, it begins to bend on day 23, and forms organized regions of primitive r and l ventricles and atriums

Question 14

senus venous

Answer 14

is attached to the atruims and begins to receive venous blood from the vitelline, umbilical and common cardinal veins, later in week 10 when these veins are obliterated, all that is left is coronary sinus draining into right atruim

Question 15

ductus arteriosus

Answer 15

attaches pulmonary artery to aorta, bypassing pulmonary circulation, becomes ligamentum arteriosum

Question 16

foramen ovale

Answer 16

connects l and r ventricle bypassing the pulmonary circulation, becomes fossa ovalis

Question 17

ductus venosus

Answer 17

connects left umbilical vein and right hepatocardiac channel bypassing hepatic portal system, becomes ligamentum venosum

Question 18

umbilical vein

Answer 18

delivers 02 nutrient rich blood from placenta to fetus, becomes round ligament

Question 19

umbilical arteries

Answer 19

the pair delivers blood from fetus to placenta, becomes medial ligaments

Question 20

respiratory diverticulum

Answer 20

at 4 weeks, starts as an outgrowth from ventral wall, therefore inner lining of larynx, trachea, bronchi, and lungs are of epithelium origin; cartiolaginous, muscular, and connective tissue are from splenchin mesoderm; lung bud pinches off of the foregut below the future larynx to seperate it from developing esophagus forming the tracheosophageal septum

Question 21

lung development

Answer 21

lung develops from repeated branching of the respiratory diverticulum, during secondary branching, right bud branches into three; third branching forms 10 tertiary bronchi in the right lung and 8 in the left; terminal brs will differentiate into alveoli

Question 22

pseudoglandular stage

Answer 22

1st stage of lung development, developing lung tissue resembles glands

Question 23

canalicular stage

Answer 23

2nd stage of lung development, terminal sacs start to form but not enough or murture enough for gas exchange

Question 24

terminal sac stage

Answer 24

3rd stage of lung development, increased number of terminal sacs and alveoli form that can perform gas exchange

Question 25

alveolar stage

Answer 25

4th stage of lung development, drastic increase in alveoli

Question 26

Esophageal atresia

Answer 26

Abnormal division of esophagus & trachea, inability to swallow

Question 27

Tracheoesophageal fistula

Answer 27

Incomplete separation of esophagus from trachea, Danger of aspirating stomach acid into lungs