Week 4 Development

Question 0

What are the folding events a result of?

Answer 0

result from differential growth rates in cells in the involved areas

Question 1

Do all the foldings events occur simultaneously?

Answer 1

Yes

Question 2

What happens to the neural folds in the cranial region?

Answer 2

early week 4, neural fold in the cranial region have thickened to form the primordial brain

Question 3

How do the head fold relative position change?

Answer 3

Initially, the primordial brain is oriented “dorsally” toward amniotic cavity

Question 4

How does the changing of position of the head fold affect the position of the heart and oropharyngeal membrane?

Answer 4

As the forebrain enlarges, brain grows cranially beyond the oropharyngeal membrane

- at this point it is hanging over the primordial heart
- a cluster of structure are bing pushed ventrally

Question 5

What will the septum transversum form?

Answer 5

central tendon of the diaphragm

Question 6

Where is the septum transversum located prior to head folding?

Answer 6

primordial heart and developing pericardial cavity

Question 7

Where is the septum transversum after head folding?

Answer 7

now locates between the developing heart and liver

Question 8

How is the foregut formed initially?

Answer 8

as a result of forebrain enlargement, part of the umbilibal vesicle endoderm is incorporated into the cranial embryo
- this cranial endoderm tube becomes the foregut

Question 9

What will the foregut develop into?

Answer 9

pharynx, esophagus, stomach, part of duodenum, liver, pancreas

Question 10

Where is the foregut located at this time?

Answer 10

at this point the foregut is between the primordial brain and the primordial heart

Question 11

What is the stomodeum?

- what will it become?

Answer 11

stomodeum - invagination anterior to oropharyngeal membrane

- becomes the future mouth

Question 12

The tail fold is caused by growth of what structure?

Answer 12

due to rapid caudal growth and extension of the neural tube (primordial spinal cord)

Question 13

What is the caudal eminence?

Answer 13

tail region that projects caudally over the cloacal membrane

Question 14

What is the cloacal membrane?

Answer 14

site of future anus

Question 15

What is the allantois?

Answer 15

• small fingerlike evaginations of the umbilical vesicle into the connecting stalk
• forms around day 16

Question 16

What is the function of allantois in animals?

Answer 16

• develops blood vessels for gas exchange

- stores urine during embryonic development

Question 17

What is the function of allantois in humans?

Answer 17

remains small in humans

Question 18

What is the urachus?

Answer 18

the allantois persists as the urachus extending from urinary bladder to umbilicus

Question 19

Where is the allantois located?

Answer 19

in the median umbilical fold

Question 20

How is the hindgut formed initially?

Answer 20

caudal portion of the umbilical vesicle is incorporated as the hindgut

Question 21

What will the hindgut eventually form?

Answer 21

will become the distal part of the colon

Question 22

What is the cloaca?

- common exit for?

Answer 22

terminal region dilates as the cloaca

- currently the common exit point for the primordial urinary bladder and rectum

Question 23

What is the proctodeum?

Answer 23

external ectodermal invagination

Question 24

What is the connecting stalk?

Answer 24

represents the primordial umbilical cord

Question 25

Where is the connecting stalk located relative to the umbilical vesicle?

Answer 25

located caudal to the remaining umbilical vesicle

Question 26

What is happening to the embryo body wall in lateral folds?

Answer 26

- due to the rapidly growing spinal cord and somites | - lateral edges roll ventrally and form a cylindrical embryo

Question 27

What is happening to the intra- and extraembryonic coelom?

Answer 27

Intraembryonic coelom is sealed off from extraembryonic coelom

Question 28

How does the midgut form?

Answer 28

midgut gets enveloped as central part of umbilical vesicle is enclosed

Question 29

What will the midgut develop into eventually?

Answer 29

forms distal part of duodenum, jejunum, ileum and proximal 2/3 of colon

Question 30

What is the omphaloenteric duct?

Answer 30

connection between midgut and umbilical vesicle gets progressively narrower

Question 31

What happens to the amniotic cavity?

Answer 31

continues enlarging

Question 32

What happens to the umbilical vesicle?

Answer 32

obliterates as amniotic cavity

Question 33

What happens to the amnion?

Answer 33

comes entirely around the embryo - encircles the connecting stalk and the omphaloenteric duct

Question 34

Where is the pericardial cavity?

Answer 34

associated with the heart

Question 35

Where is the peritoneal cavity?

Answer 35

associated with abdominal and pelvic viscera

Question 36

What are the pericardioperitoneal canals?

Answer 36

associated with the lungs

Question 37

What do the pericardioperitoneal canals become?

Answer 37

eventually separate off to form pleural cavities

Question 38

What is the parietal mesothelium?

Answer 38

lining of pericardial, peritoneal and pleural cavities

Question 39

What is the parietal mesothelium derived from?

Answer 39

somatic mesoderm

Question 40

What is the visceral mesothelium?

Answer 40

organs that are associated with each cavity are covered by this mesoderm

Question 41

Where is the visceral mesothelium derived from?

Answer 41

splanchnic mesoderm

Question 42

What is the mesentery? What does it extend between?

Answer 42

- double layered extension of peritoneum | - span between visceral and parietal peritoneum

Question 43

What is the structural function of the mesentery?

Answer 43

connect an organ to the body wall

Question 44

What is the neurovascular function of the mesentery?

Answer 44

conveys nonvasculature from body wall to organ

Question 45

Where is the dorsal mesentery located?

Answer 45

spans from gut tube to dorsal wall of embryo

Question 46

How does the dorsal mesentery appear in adult?

Answer 46

widely variable in adult derivatives along the length of the gut tube

Question 47

Where is the ventral mesentery located?

Answer 47

spans from gut tube to ventral wall of embryo

Question 48

In which parts of the gut is this found?

Answer 48

persists in adult foregut as lesser omentum and falciform ligament

Question 49

How does the ventral mesentery appear in the adult?

Answer 49

breaks down and disappears along midgut and hindgut

Question 50

What will the septum transversum become?

Answer 50

will become the central tendon of the thoracic diaphragm

Question 51

How does the septum transversum partition the intraembryonic coelom?

Answer 51

partially separates the pericardioperitoneal canals from the peritoneal cavity - contributes to the formation of bilateral pleural cavities