Amniotes 1 - Birds

Question 1

What are amniotes?

Answer 1

vertebrates who embryos form an amnion

Question 2

What is an amnion?

Answer 2

one of the extraembryonic membranes that enable the embryos to survive on land

Question 3

Where does fertilization of an egg begin?

Answer 3

in the infundibulum within the reproductive tract

Question 4

Describe the journey of an egg through the reproductive tract?

Answer 4

1. Fertilization occurs within infundibulum
2. Albumen and egg white proteins are added at the magnum
3. Shell membrane are added at the isthmus
4. Shell added in uterus

Question 5

What is ovalbumin?

Answer 5

Possibly a storage protein that serves as another source of nutrition for development

Question 6

What is lysozyme?

Answer 6

An enzyme that serves as antibiotics and protects the egg from infection during development

Question 6

Shell membrane vs shell?

Answer 6

shell membrane protects the egg from bacterial infection

shell is a porous calcium carbonate that allows air and moisture to pass through

Question 6

Where does the embryo develop in the egg?

Answer 6

the blastodisc region

Question 7

What are the three subregions of the blastodic?

Answer 7

1. Area pellucida (where initial cell divisions take place)
2. Area opaca
3. Marginal zone (intersection between 1 and 2)

Question 7

What does the area pellucida sit on top of?

Answer 7

Subgerminal cavity (fluid-filled)

Question 8

Do birds embryos have complete or incomplete cleavage?

Answer 8

Incomplete (meroblastic)

Question 9

What is the yolk distribution in bird embryos?

Answer 9

Telolecithal

Question 10

What happens before gastrulation can occur?

Answer 10

1. Hypoblast delaminates (migrate) from the epiblast, forming a second layer
2. A secondary hypoblast will form from the Koller’s sickle
3. Secondary hypoblast will grow anteriorly and displace the primary hypoblast
4. Gastrulation occurs in the epiblast anterior to the PMZ

Question 11

Hypoblast inhibits the epiblast from _______

Answer 11

gastrulation

Question 12

How is inhibition of epiblast stopped?

Answer 12

secondary hypoblast displaces primary hypoblast

Question 13

What happens during gastrulation in birds?

Answer 13

1. Epiblast cells will move to the midline and converge to the posterior end
2. Formation of a primitive streak
3. Epiblast cells move into the embryo through the primitive groove and become germ layers
4. Anterior end of primitive streak becomes Hensen’s node

Question 14

How do epiblast cells become germ layers?

Answer 14

Endoderm: epiblast that displace the hypoblast
Mesoderm: epiblast that go inside of embryo and go sideways
Ectoderm: epiblast that stay outside of the embryo

Question 15

What happens if you transplant Hensen’s node in a recipient?

Answer 15

You get two neural tubes which develop into two heads.

Question 16

What happens during gastrulation after ingression?

Answer 16

5. Primitive streak regresses to the posterior end
6. Embryo will form from the anterior end to the posterior end

Question 17

What are the four germ layers?

Answer 17

1. Ectoderm
2. Somatic mesoderm
3. Splanchnic mesoderm
4. Endoderm

Question 18

What are the extraembryonic membranes?

Answer 18

A. Amnion
B. Chlorion
C. yolk sac
D. Allantois