Animal Embryology

Question 0

Cleavage

Answer 0

Early embryonic development is characterized by a series of early mitotic divisions known as cleavage
-the divisions lead to an increase in cell number but not an increase in protoplasm(cytoplasm volume stays constant)

Question 1

Embryology is

Answer 1

The study of the development of a unicellular zygote into a complete multicellular organism

Question 2

Cleavage results in

Answer 2

-progressively smaller cells

Question 3

Indeterminate cleavage

Answer 3

-one that results in cells that maintain the ability to develop into a complete organism

Question 4

Identical twins

Answer 4

The result of an intermediate cleavage

Question 5

Determinate cleavage

Answer 5

Results in cells whose future differentiation pathways are detetmined at an early developmental stage

Question 6

Differentiation

Answer 6

Specialization of cells that occurs during development

Question 7

The morula

Answer 7

• solid ball of embryonic cells

- formed after several divisions

Question 8

Blastuation

Answer 8

Begins when the morula develops a blastocoel which becomes a blastila
-it then adheres to the uterine wall

Question 9

GastrulTION

Answer 9

-once implanted in the uterus cell migrations transform the single-cellayer of the blastula into a three layered structure called the gastrula

Question 10

Three layers of the gastrula

Answer 10

Ectoderm- hair nails epithelium, lens of eye, nervous system

Endoderm- epitheleal linings of the digestive and respiratory tracts(lungs, liver etc)

Mesoderm- musculoskeltal system, circ system reprpductive system

Question 11

Types of development

Answer 11

• external development
• nonplacental internal development
• placental internal development

Question 12

External development

Answer 12

-occurs outside the mothers body

Question 13

Membranes that facilitate external development

Answer 13

1 chorion- lines the inside of the shell

2 allantois- involved in respiration and excretion

3 amnion- encloses the amniotic fluid
— amniotic fluid provides an aqueous environment that protects the developing embryo from shock

4 yolk sac- encloses the yolk. Blood vessels in it transfer food to the embryo

Question 14

Nonplacental internal development

Answer 14

• early development within the body of the mother protects the young
• there is no placenta so exchange of food and water between the mother and the young is limited
• offspring born young

Question 15

Placental internal development

Answer 15

• growing fetus recieves oxygen directly from its mother through a circulatory system
• the system supplies oxygen and nutrients and removes carbon dioxide and wastes

Question 16

Two key components of the placental internal development

Answer 16

Placenta and umbilical cord

Question 17

Childbirth is accomplished by

Answer 17

Labor