Chapter 12: Bird Development

Question 1

fertilization of chick egg occurs in the hen’s ___, before ___ and shell are secreted over it.

Answer 1

fertilization of chick egg occurs in the hen’s OVIDUCT, before ALBUMIN and shell are secreted over it.

Question 2

chick egg is telolecithal, meaning:

Answer 2

there is a small blastodisc of cytoplasm, sitting on top fo a lot of yyolk.

Question 3

the cytoplasm on the chick egg is known as the

Answer 3

blastodisc

Question 4

the yolky eggs of birds undergo ____ ___ cleavage. What is this?

Answer 4

discoidal meroblastic cleavage: meaning the whole egg doesn’t divide. Cleavage only occurs on the non yolk blastodisc.

Question 5

the ___ is a shock absorber and provider of hydration is the:

Answer 5

amnion

Question 6

the ___ ___ provides nutrients and allows for development of circulatory system

Answer 6

yolk sac

Question 7

the ___ stores wastes products

Answer 7

allantois

Question 8

the chorionis:

Answer 8

a blood vessel network allowing for gas exchange with the external environment.

Question 9

where does cleavage and development of the chick embryo take place?

Answer 9

blastodisc: small yolk-free area of cytoplasm that sits on top of the yolk.

Question 10

by the time the egg is laid, what stage is it at?

Answer 10

the late blastula stage.

Question 11

in the blastodisc (early cleavage before laying), the first cleavage is central, and the early cleaved cells are in contact with each other via ___ ___ and also are in contact with the yolk. ____ and ____ cleavages create a 4-layered ____

Answer 11

in the blastodisc (early cleavage before laying), the first cleavage is central, and the early cleaved cells are in contact with each other via tight junctions and also are in contact with the yolk. EQUITORIAL and VERTICAL cleavages create a 4-layered BLASTODERM

Question 13

What is the SUBGERMINAL CAVITY? When is it created?

Answer 13

space between the blastoderm and yolk. it is created when the blastoderm cells absorb water from the albumin and secrete the fluid beween themselves and the yok.

Question 14

What is the area pellucida?

Answer 14

the ONE LAYER of cells that remain in the blastoderm. The deep cells in the center of blastoderm shed and die.

remaining Area pellucida later forms the embryo.

Question 15

What is the area opaca?

Answer 15

the peripheral ring of blastoderm cells that have not shed their deep cells. the area pellucida is the remenants (1-cell-thick) after shedding occurs.

Question 16

What is the marginal zone

Answer 16

the area between the area pellucida and the area opaca

Question 17

before gastrulation, the blastoderm will form these two broad structures while laying:

Answer 17

1) the epiblast: forms the embryo, amnion, chorion, and allantois
2) hypoblast: yolk sac and stalk that attaches the yolk, the endodermal digestive tube, and secretes signals that directs epiblast migration.

Question 18

by the time the egg is laid, the blastoderm contains 50,000 cells and are usually on the surface of the egg as an ____ ____, forming an upper layer called the ____.

Answer 18

by the time the egg is laid, the blastoderm contains 50,000 cells and are usually on the surface of the egg as an AREA PELLUCIDA, forming an upper layer called the EPIBLAST

Question 19

shortly after being laid, the epiblast of the area pellucida thickens to form a ___ ___ at the posterior edge. What is the posterior marginal zone?

Answer 19

shortly after being laid, the epiblast of the area pellucida thickens to form a KOLLER’S SICKLE at the posterior edge. the Posterior marginal zone is the marginal zone between the area opaca and the koller’s sick of the epiblast in the area pellucida.

Question 20

A sheet of cells (PRECURSORS OF SECONDARY HYPOBLAST) at the posterior boundary between the area pellucida and the marginal zone migrates anteriorly beneath the surface of the epiblast. In the meantime, the anterior cells of the epiblast have delaminated and stayed attached to the epiblast, to form ___ ___

Answer 20

hypoblast islands.

Question 21

the hypoblast cells (islands) formed from the anterior regions of delaminated epiblast cells form the ____ __, and posterior cells from the posterior Koller’s sickle region migrate ANTERIORLY to combine with these islands to form the complete hypoblast layer, known as the __ ___, or ____.

Answer 21

the hypoblast cells (islands) formed from the anterior regions of delaminated epiblast cells form the PRIMARY HYPOBLAST, and posterior cells from the posterior Koller’s sickle region migrate ANTERIORLY to combine with these islands to form the complete hypoblast layer, known as the SECONDARY HYPOBLAST or ENDOBLAST.

Question 22

The epiblast is formed on the top of the area pellucida, and underneath the epiblast, the complete hypoblast layer forms by some epiblast cells (secondary hypoblast precursors) delaminating to form hypoblast islands and joining with a second layer of cells that are migrating anteriorly. This results in a 2-layered ____ (epiblast + hypoblast), joined together at the ___ ___ of the area opaca, and the space between the layers form a blastocoele like cavity that will later form the ___ ___

Answer 22

The epiblast is formed on the top of the area pellucida, and underneath the epiblast, the complete hypoblast layer forms by some epiblast cells (secondary hypoblast precursors) delaminating to form hypoblast islands and joining with a second layer of cells that are migrating anteriorly. This results in a 2-layered BLASTODERM (epiblast + hypoblast), joined together at the MARGINAL ZONE of the area opaca, and the space between the layers form a blastocoele like cavity that will later form the PRIMITIVE STREAK

Question 23

T/F: THE HYPOBLAST HELPS FORM THE EMBRYO

Answer 23

false. the hypoblast does not contribute any cells to the developing embryo .The hypoblst forms portions of the extraembryonic membranes and provides chemical signals that specify the migration of the epiblast cells. The 3 germ layers of the embryo are formed solely from the epiblast.