Week 2 Content

Question 1

What does endoderm form?

Answer 1

The lining of the digestive tract which covers the entire length of the body. It buds off the liver, gall bladder, pancreas and lungs. The cranial part becomes the pharynx with budding of the thyroid, thymus and parathyroid.

Question 2

During body folding, there is the formation of an endodermal tube. What does the tube form?

Answer 2

The gut tube.

Question 3

The mesodermal layer of the gut tube consists of what type of mesoderm?

Answer 3

Splanchnic mesoderm.

Question 4

What type of mesoderm lines the body cavity?

Answer 4

Somatic mesoderm.

Question 5

What does the septum transversum do?

Answer 5

It separates the coelom into thoracic and abdominal cavities and develops into part of the diaphragm and ventral mesentery of the stomach and duodenum.

Question 6

What does the allantois help with?

Answer 6

Gas exchange and excretion.

Question 7

What does the allantois become?

Answer 7

The urachus (connects fetal bladder to yolk sac).

Question 8

Which artery supplies the foregut?

Answer 8

The celiac artery.

Question 9

Which artery supplies the midgut?

Answer 9

The superior mesenteric artery.

Question 10

Which artery supplies the hindgut?

Answer 10

The inferior mesenteric artery.

Question 11

Which part of the stomach grows the fastest?

Answer 11

The dorsal part.

Question 12

While growing, the stomach undergoes what degree of rotation?

Answer 12

90 degree clockwise rotation.

Question 13

A smaller/lesser curvature is found on which side of the stomach?

Answer 13

The right side. (Ventral border).

Question 14

A greater curvature is found of which side of the stomach?

Answer 14

The left side. (Dorsal border).

Question 15

As well as 90 degree rotation, the stomach undergoes what type of rotation?

Answer 15

Superior (upwards) rotation to form characteristic ‘c’ shape.

Question 16

List the three general steps of development for other endodermal organs.

Answer 16

1. Endodermal thickening.
2. Cells proliferate to form bud.
3. Continuous lengthening and bifurcation/branching.

Question 17

Briefly outline lung development.

Answer 17

1. Budding of endoderm (will form trachea).
2. Ventro-caudal growth. Bifurcates to form left and right trachael buds (will form bronchi).
3. Next bifurcation forms bronchial buds (3 on right, 2 on left).
4. Third bifurcation gives tertiary bronchial buds.
5. There are 14 more branchings to give terminal bronchioles.

Question 18

The four pharangeal arches have an outer covering of ectoderm, a core of mesenchymal cells and an inside lining of endoderm. They also have a cartilage (skeletal), muscle and nerve element. What do they give rise to?

Answer 18

Skeletal, muscle and nerve elements in the head of the embryo.

Question 19

Where do the primordial germ cells migrate?

Answer 19

Along the hindgut, through the dorsal mesentery to left and right genital ridges (to gonads).

Question 20

When are the various structures of the embryo most susceptible to birth defects upon exposure to harmful agents?

Answer 20

The first 2 to 3 months.

Question 21

Classify a human.

Answer 21

Kingdom: Animalia 
Superphylum: Coelomate
Phylum: Chordata
Subphylum: Vertebrate
Class: Mammalia
Order: Primate
Family: Hominidae 
Genus: Homo
Species: Homo sapiens

Question 22

What is a coelom?

Answer 22

A coelom is a body cavity which is

completely lined with mesoderm.

Question 23

Where is a human’s gut tube suspended?

Answer 23

In their coelom.