Lecture 17: Establishing the Body Cavities and Formation of the Diaphragm

Question 1

Intraembryonic Coelem

Answer 1

Formed at beginning of fourth week. Vesicles in the lateral mesoderm coalesce, forming a horse-shoe shaped cavity

Question 2

Functions of Intraembryonic Coelem

Answer 2

Continuous with extra-embryonic coelem (the space external to the yolk-sac), gives space for organs to grow into

Question 3

Cranial-Caudal folding

Answer 3

The brain and tail regions grow quicker than the rest of the body, causing the embryo to fold into itself around the yolk sac

Question 4

Lateral folding

Answer 4

The lateral edges of the germ disk fold towards each other, ventrally, caused by rapid growth of amnion and somites. Fuse in the midline. The yolk sac (made of endoderm) pinches off and becomes narrow and more tubular.

Question 5

Regions of yolk sac after lateral folding

Answer 5

Foregut, midgut, hindgut

Question 6

Mesoderm lining periteneal cavity

Answer 6

splanchnic mesoderm layer

Question 7

Periteneal Cavity

Answer 7

What embryonic coelem is called after lateral folding is complete

Question 8

Mesoderm lining the anterior body wall

Answer 8

somatic mesoderm layer

Question 9

Dorsal Mesenteries

Answer 9

Suspends the gut tube (former yolk sac) within the periteneal cavity from dorsal side in caudal, foregut, midgut, hindgut

Question 10

Ventral mesenteries

Answer 10

Suspends the gut tube from ventral side, only present in proximal foregut (stomach and doedunum)

Question 11

Mesentery

Answer 11

A double layer of periteneum that connects organs to the body wall. Vessels and nerves travel through the mesentery, especially those supplying the gut

Question 12

parts of embryonic body cavity

Answer 12

Pericardial cavity, peritoneal cavity, connected by 2 pericardial-peritoneal canals

Question 13

Arterial supply to fore-gut

Answer 13

celiac artery

Question 14

arterial supply to midgut

Answer 14

Superior mesenteric artery

Question 15

Arterial supply to hindgut

Answer 15

Inferior mesenteric artery

Question 16

Physiological herniation of midgut

Answer 16

The midgut sticks into the extraembryonic coelem from the intraembryonic coelem until week 10, at which point the intestine retreats into the intraembryonic coelem. After lateral folding the communication between the two coelems becomes much narrower, and only exists in one cross-section.

Question 17

Parts of the diaphragm

Answer 17

The Septum transversum
Pleuroperitoneal membrane
dorsal mesentery of the esophagus
muscular growth of lateral body wall

Question 18

Septum Transversum

Answer 18

Thick plate of mesodermal tissue, occupies the space between the pericardial cavity and the omphaloenteric duct. Originally were cranial to the developing heart, after cranio-caudal folding migrates to sit to above location.

Question 19

Omphaloenteric duct

Answer 19

After lateral folding, this is the remaining communication between the gut-tube and the yolk sac/amnion vesicle

Question 20

Pleuropericardial folds

Answer 20

Folding in of the tissue between the pleural cavities (where lungs will form) which are inferior and posterior to the pericardial cavity (where heart will form). They separate the former pleuroperitoneal canals from the pericardial cavity, and create the pleural space.

Question 21

Pleuropericardial membrane, origin and what they contain

Answer 21

Pleuropericardial folds become these membranes. These membranes contain common cardinal veins and phrenic nerves

Question 22

What does septum transversum become?

Answer 22

the central tendon of the diaphragm

Question 23

pleuroperitoneal membrane

Answer 23

Originates from pleuroperitoneal folds, grows in from lateral body wall to merge with septum transversum and dorsal mesentery of esophagus. There are small openings closed by migrating myoblasts

Question 24

Crura of diaphragm

Answer 24

pair of muscle bundles that originate from myoblasts that migrate into the dorsal mesentary

Question 25

dorsal mesentary contributes what to diaphragm

Answer 25

Forms median part of diaphragm

Question 26

Lateral Body wall muscular ingrowth contribution to diaphragm

Answer 26

Forms the peripheral edges of the diaphragm

Question 27

Formation of costo-diaphragmatic recesses

Answer 27

Also called costophrenic angles, formed by descending pleural space during development

Question 28

Innervation of diaphragm

Answer 28

2 phrenic nerves (motor&sensory, C3, C4, C5). Spinal nerves migrate with septum transversum, lengthen to 30 cm as diaphragm descends during development.
Intercostal nerves to the body wall (sensory)

Question 29

Congenital Diaphragmatic Hernia

Answer 29

1/2200 newborns, 85% of time on left side bc that side closes later than right side; viscera herniates into thorax