Lab 8 - observation of 4-5 day old chick whole mounts and sections

Question 1

Whys is it better to use somite stage to define development rather than time post fertilization?

Answer 1

development can be sped up or down by manipulating temperatures and other conditions

Question 2

What is omphalomesenteric vein?

Answer 2

bring blood from the yolk to the embryo and back

Question 3

Do veins or arteries develop first?

Answer 3

veins

Question 4

What are some characteristics of the myelncephalon?

Answer 4

• otic vesicle
• highly myelinated

Question 5

What are the four embryonic movements, describe each movement?

Answer 5

1. torsion
   - moves onto left side
2. cervical flexure
   - spinal column bends (hunches)
   - seperates hindbrain and midbrain
3. cephalic flexure
   - forms the midbrain
4. caudal flexure
   - posterior end curls in

Question 6

What are the four extraembryonic tissues in chicks, what is the role of each one, and what tissues develop each extraembryonic tissue?

Answer 6

1. chorion
   - gas exchange, transparent, close to shell
   - ectoderm + somatic mesoderm = somatopleure
2. amnion
   - prevents dessication, shock absorption
   - ectoderm + somatic mesoderm = somatopleure
3. yolk sac
   - nutrition source
   - splanchnic mesoderm + endoderm = splanchnopleure
4. allantois
   - waste disposal
   - planchnic mesoderm + endoderm = splanchnopleure

Question 7

What is the importance of calcium transport from the shell to a developing chick embryo?

Answer 7

• helps embryo develop
• makes the shell softer –> makes hatching easier

Question 8

What extramembryonic membranes are missing from mammals, where did they go?

Answer 8

• allantois is vestigal
• chorion evolved into the placenta

Question 9

Describe the heart to yolk (nutrient depleted) blood circulation in 4-5 day old chicks

Answer 9

truncus arteriosus –> omphalomesenteric artery –> yolk sack –> omphalomesenteric vein –> heart

Question 10

Describe the heart to allantois (oxygen depleted) blood ciruculation in 4-5 day old chicks

Answer 10

sinus venosus –> allantoic artery –> chorioallontoic membrane –> allantoic vein –> heart

Question 11

Describe the heart to tissue (somatic circulation) blood circulation in 4-5 day only chicks

Answer 11

ventricle –> dorsal aorta –> somatic circulation (tissues) –> heart

Question 12

What are the functions of the placenta?

Answer 12

1. endocrine
2. immune
3. respiration