Lecture 4

Question 1

stages of developing embryo:

Answer 1

1. Fertilization
2. Cleavage
3. Gastrulation
4. Organogenesis

Question 2

fertilization:

Answer 2

fusion of sperm and egg

Question 3

cleavage:

Answer 3

• series of cell divisions that divined embryo into blastula which evaginates into a gastrula
• Cleavage partitions the cytoplasm of one large cell into many smaller cells called blastomeres

Question 4

blastula:

Answer 4

hollow ball of cells with a fluid-filled cavity called a blastocel

Question 5

gastrula:

Answer 5

multilayered embryo

Question 6

gastrulation:

Answer 6

converts the blastula to a gastrula, which has
a primitive digestive cavity and three germ layers that gives rise to the innermost tissues

Question 7

organogenesis:

Answer 7

rudimentary formation of organs

Question 8

polyspermy:

Answer 8

the entry of multiple sperm nuclei into the egg

Question 9

identical twins =

Answer 9

same placenta

Question 10

fraternal twins =

Answer 10

separate placentas

Question 11

acrosomal reaction:

Answer 11

triggered when the sperm meets the egg
- the tip of the sperm releases hydrolytic enzymes that digest material surrounding the egg

Question 12

cortical reaction:

Answer 12

• the fusion of egg and sperm
• requires a high concentration of calcium ions in the egg
• triggered by a change in calcium concentration
• calcium ions spread across the egg correlates with the appearance of the fertilization envelope
• the rise in calcium ions in the cytosol increases the rates of cellular respiration and protein synthesis by the egg cell

Question 13

fertilization envelope:

Answer 13

• acts as a slow block to polyspermy
• vesicles beneath the egg plasma membrane release their contents and form a fertilization envelope
• gamete contact and/or fusion depolarizes the egg cell membrane and sets up a fast block

Question 14

during internal viviparous fertilization,

Answer 14

a sperm must travel through a layer of follicle cells surrounding the egg before it reaches the zona pellucida, or extracellular matrix of the gg

Question 15

zona pellucida:

Answer 15

extracellular matrix of the egg

Question 16

sperm binding triggers which reaction?

Answer 16

cortical

Question 17

cleavage is symmetric or asymmetric?

Answer 17

asymmetric due to the distribution of yolk - stored nutrients

Question 18

morphogenesis:

Answer 18

the process by which cells occupy their appropriate locations

Question 19

morphogenesis involves which stages?

Answer 19

1. gastrulation
2. organogenesis

Question 20

what are the three layers produced by gastrulation called?

Answer 20

embryonic germ layers

Question 21

archenteron:

Answer 21

newly formed cavity during gastrulation and opens through the blastospore

Question 22

ectoderm:

Answer 22

• forms the outer layer
• epidermis of skin and glands
• nervous and sensory systems
• jaws and teeth

Question 23

endoderm:

Answer 23

• lines the digestive tract
• the epithelial lining of the digestive tract, respiratory, excretory, reproductive
• glands for thymus, thyroid, and parathyroid

Question 24

mesoderm:

Answer 24

• partly fills the space between the endoderm and ectoderm
• skeletal and muscular systems
• circulatory and lymphatic systems
• excretory and reproductive
• dermis of the skin
• adrenal cortex

Question 25

deuterostome =

Answer 25

anus develops from blastopore

Question 26

protosomes =

Answer 26

mouth develops from blastopore