Abdominal Embryology

Question 1

Gastrulation occurs at week ___ to create three embryonic germ layers: ___, ___, and ___.

Answer 1

week 3; ectoderm, mesoderm, endoderm

Question 2

Cells that displace the hypoblast form the ___

Answer 2

endoderm

Question 3

Cells that remain in the epiblast form the ___

Answer 3

ectoderm

Question 4

Cells that lie between the endoderm and ectoderm form the ___

Answer 4

mesoderm

Question 5

All three germ layers are derived from the ___

Answer 5

epiblast

Question 6

What two places in the developing embryo are not a 3-layer disk, and what do they go on to form? What layer is missing?

Answer 6

Bucopharyngeal membrane –> forms oral cavity

Cloacal membrane –> forms anus

Missing the mesoderm

Question 7

In the middle of week ___, the mesoderm differentiates into three parts: ___, ___, ___.

Answer 7

Week 3; paraxial mesoderm, intermediate mesoderm, lateral plate mesoderm

Question 8

The paraxial mesoderm forms ___ and ___.

Answer 8

Somitomers (striated muscles of face and throat) and somites (dermis, skeletal muscles, vertebrae)

Question 9

The intermediate mesoderm forms the ___

Answer 9

urogenital system

Question 10

The lateral plate mesoderm forms the ___ from fused ___, which is a ___-shaped cavity.

Answer 10

intraembryonic coelom from coelomic spaces; horseshoe-shaped

Question 11

The curve of the intraembryonic coelom horseshoe become the ___, and the lateral extensions become the ___ and ___.

Answer 11

curve - pericardial cavity

lateral extensions - pleural and peritoneal cavities

Question 12

What are the two layers of the lateral plate mesoderm?

Answer 12

Somatic (somatopleure) - parietal

Splanchnic (splanchnopleure) - visceral

Question 13

What four folds does the flat trilaminar disc make to become 3D?

Answer 13

Head/cephalic, tail/caudal, and two lateral folds

Question 14

During embryonic folding, the ___ and ___ grow, but the ___ doesn’t.

Answer 14

Amnion and embryonic disc grow; yolk sac doesn’t

Question 15

During ___ folding, part of the yolk sac is converted into ___, forming the ___, ___, and ___.

Answer 15

lateral folding; gut tube; foregut, midgut, hindgut

Question 16

___ causes the cranial folding

Answer 16

Growth of the forebrain beyond the buccopharyngeal membrane

Question 17

Result of cranial folding

Answer 17

Pushes heart, pericardial coelom, septum transversum, and buccopharyngeal membrane in place

Question 18

___ causes caudal folding

Answer 18

growth of spinal cord

Question 19

Result of caudal folding

Answer 19

cloacal membrane is positioned correctly and part of yolk sac is incorporated as hindgut

Question 20

Somatic mesoderm lines the embryonic ___ and becomes ___, ___, and ___

Answer 20

body cavity; parietal pleurae, pericardium, peritoneum

Question 21

Splanchnic mesoderm covers ___ and becomes ___, ___, ___, and ___

Answer 21

endodermal gut tube; visceral layer of pleurae, pericardium, peritoneum, and smooth muscle of gut tube

Question 22

What are the three divisions of the intraembryonic cavity, and what do they contain?

Answer 22

Pericardial cavity - heart
Pericardioperitoneal canals - lungs
Peritoneal cavity - gut

Question 23

The septum transversum initially starts at ___

Answer 23

C1

Question 24

By week 8, the anterior part of the septum transversum is at ___ and the posterior part is at ___

Answer 24

T7, T12

Question 25

At weeks ___, myoblasts muscularize the septum transversum, bringing along the ___ nerve

Answer 25

weeks 5-6; phrenic nerve

Question 26

What is a congenital diaphragmatic hernia?

Answer 26

Malformation of the diaphragm, usually failure of the pleuroperitoneal membranes to fuse with other diaphragmatic components, allowing abdominal contents to herniate into the thorax

Question 27

Result of congenital diaphragmatic hernia

Answer 27

abdominal contents herniate into pleural cavities, which interferes with lung development

Question 28

What are the four precursors to the diaphragm, and which part(s) do they form?

Answer 28

1. Septum transversum - central tendon and majority of anterior diaphragm
2. Esophageal mesenchyme - right and left crura (and esophageal hiatus)
3. Muscular ingrowth from lateral body wall - posteriolateral part
4. Pleuroperitoneal membranes - posterior diaphragm

Question 29

___ is the downward indentation between the diaphragm and chest wall. That space is called the ___

Answer 29

Costophrenic angle; costodiaphragmatic recess

Question 30

The costophrenic angle is important in detecting ___ on x-rays

Answer 30

small pleural effusions

Question 31

Two types of congenital diaphragmatic hernias

Answer 31

Bochdalek and Morgagni

Question 32

Bochdalek CDH

Answer 32

posteriolateral diaphragmatic defect, usually on the left side; majority of cases

Question 33

Morgagni CDH

Answer 33

anterior, retrosternal, or parasternal diaphragmatic defect; rare

Question 34

What is eventration, what causes it, and how does it appear on an X-ray?

Answer 34

It is when the abdominal cavity contents push up on (but not through) a thin part of the diaphragm; it is due to incomplete muscularization of the diaphragm; On an x-ray, the diaphragm dome/margin is still visible, but is elevated; all intestinal air bubbles are below the diaphragm

Question 35

What separates the pleural and pericardial cavities?

Answer 35

Pleuropericardial folds

Question 36

What are the three layers of the pleuropericardial folds and what do they become?

Answer 36

body wall mesenchyme sandwiched between two layers of somatopleuric mesoderm; one layer of the somatopleuric mesoderm joins the visceral pleura around the lung; the other layer becomes the parietal layer of the serous pericardium

Question 37

Where is the phrenic nerve embedded?

Answer 37

The serous layer of pericardium (in between the fibrous pericardium and mediastinal pleura)

Question 38

Epithelial lining of GI tract is from ___

Answer 38

endoderm

Question 39

Smooth muscle of GI tract is from ___

Answer 39

splanchnic (visceral) mesoderm

Question 40

The yolk sac and midgut are connected via the ___

Answer 40

vitelline duct

Question 41

Endodermal derivatives other than GI tract epithelial lining

Answer 41

Parathyroid glands, thymus, thyroid glands, lungs, liver, pancreas, gallbladder