Body Folding & Body Cavities

Question 1

What are the phases of embryonic development?

Answer 1

Growth
Morphogenesis
Differentiation

Question 2

What causes the pulling and pinching of an embryo into new shapes?

Answer 2

Upregulation and downregulation of cell junctions

Question 3

What does the growth phase refer to?

Answer 3

Cell division and elaboration of cell products

Question 4

What does the morphogenesis phase refer to?

Answer 4

Development of shape, size, and other features of a particular organ or part or the whole body

Question 5

What is morphogenesis controlled by?

Answer 5

Gene expression and regulation in an orderly sequence

Question 6

What does the differentiation phase refer to?

Answer 6

Cells organized in precise pattern of tissues and organs capable of performing specialized functions

Question 7

Where does the primordium of the intraembronic coelom first appear?

Answer 7

In the lateral plate mesoderm

Question 8

What is the lateral plate mesoderm divided into?

Answer 8

Somatic (parietal) layer

Splanchnic (visceral) layer

Question 9

What is the somatic (parietal) layer of lateral mesoderm continuous with?

Answer 9

Extramembryonic mesoderm covering amnion

Question 10

What is the splanchnic (visceral) layer of lateral mesoderm continuous with?

Answer 10

Extraembryonic mesoderm covering umbilical vesicle

Question 11

What is the somatopleure?

Answer 11

Somatic mesoderm and overlying embryonic ectoderm that forms the body wall

Question 12

What is the splanchnopleure?

Answer 12

Splanchnic mesoderm and underlying embryonic endoderm that forms embryonic gut

Question 13

When does embryonic head folding begin?

Answer 13

Week 4/day 22

Question 14

What do the neural folds do during head folding?

Answer 14

Project dorsally and overgrow pharyngeal membrane

Question 15

What does overgrowth of the neural folds do with regards to other structures?

Answer 15

Moves septum transversum, primordial heart, pericardial coelom, and oropharyngeal membrane to ventral surface

Question 16

During head folding, what happens with the endoderm?

Answer 16

It is incorporated as the foregut

Question 17

What structures does head folding move into their appropriate locations?

Answer 17

Mouth, heart, and gut tube

Question 18

What causes folding of the caudal end of the embryo?

Answer 18

Growth of the distal neural tube

Question 19

After tail folding, the caudal eminence (tail region) projects over what?

Answer 19

The cloacal membrane (future anus)

Question 20

What germ layer helps form the hindgut and midgut?

Answer 20

Endoderm

Question 21

Where does the primitive streak lie relative to the cloacal membrane before and after folding?

Answer 21

Before: cranial to cloacal membrane
After: caudal to cloacal membrane

Question 22

What is the allantois?

Answer 22

Diverticulum of umbilical vesicle

Question 23

What structures does tail folding reposition?

Answer 23

Hindgut, primitive streak, and cloacal membrane

Question 24

How do the lateral folds create a cylindrical embryo?

Answer 24

R/L lateral folds extend ventrally toward midline, wrapping around embryo to fuse

Question 25

What is the omphaloenteric duct?

Answer 25

Connection between umbilical vesicle and midgut

Question 26

What is gastroschisis?

Answer 26

Protrusion of viscera to the R of the umbilical cord, bowel uncovered and floating in amniotic fluid

Caused by failure of lateral body folds to fuse properly

Question 27

What is a congenital epigastric hernia?

Answer 27

Midline bulge of abdominal wall between xiphoid process and umbilicus, bowel not exposed

Question 28

What is the intraembryonic coelom divided into?

Answer 28

Pericardial cavity
Pleural cavities
Peritoneal cavity

Question 29

What are the pericardial, pleural, and peritoneal cavities lined with?

Answer 29

Mesothelium

Question 30

What is the location of the pericardial cavity after head folding?

Answer 30

Anterior to foregut and cranial to septum transversum

Question 31

What does the pericardial cavity open into?

Answer 31

Pericardioperitoneal canals (x2), lateral/dorsal to foregut and dorsal to septum transversum

Question 32

What is the dorsal mesentery?

Answer 32

Suspends caudal foregut, midgut, and hindgut in the peritoneal cavity

Question 33

What is the septum transversum?

Answer 33

Primordium of central tendon of diaphragm

Question 34

What folds grow from the body wall to separate the cavities?

Answer 34

Pleuropericardial folds (cranial) and pleuroperitoneal folds (caudal)

Question 35

What grows into the pericardioperitoneal canals that cause the cavity to expand?

Answer 35

Bronchial buds

Question 36

When the bronchial buds grow ventrally, what happens?

Answer 36

They push through the mesenchyme separating it into an outer layer (thoracic wall) and an inner layer (fibrous pericardium)

Question 37

When do the pleuroperitoneal membranes fuse with the dorsal mesentery of the esophagus and septum transversum?

Answer 37

Week 6

Question 38

What type of cell migrates into the pleuroperitoneal membrane to complete the closure process?

Answer 38

Myoblasts

Question 39

Which side of the pleuroperitoneal opening closes first?

Answer 39

R slightly before L

Question 40

What makes up the diaphragm?

Answer 40

Septum transversum
Pleuroperitoneal membranes
Dorsal mesentery
Myoblasts

Question 41

How is the phrenic nerve formed?

Answer 41

Myoblasts pull ventral rami (C3-C5) with them and pass through pleuropericardial membranes

Question 42

What is a congenital diaphragmatic hernia (CDH)?

Answer 42

Viscera bulges into pleural cavity, usually on L side. May involve delayed lung maturation of polyhydramnios, can be corrected at birth