Lecture 10 - Phases of Embryonic Development

Question 1

Six steps in embryonic development

Answer 1

1. gametogenesis
2. fertilization
3. cleavage
4. blastulation
5. gastrulation
6. neurulation/organogenesis

Question 2

process by which the diploid germ cells undergo a number of chromosomal and morphological changes to form mature haploid gametes

Answer 2

gametogenesis

Question 3

where are gametes produced

Answer 3

gonads

Question 4

the pole (end) of the egg where yolk is least concentrated

Answer 4

animal pole

Question 5

the hemisphere of the egg where animal pole is located

Answer 5

animal hemisphere

Question 6

the pole (end) of the egg where yolk is the most concentrated

Answer 6

vegetal pole

Question 7

the hemisphere of the egg where vegetal pole is located

Answer 7

vegetal hemisphere

Question 8

process whereby two sex cells fuse together to create a new individual with genetic potentials derived from both parents

Answer 8

fertilization

Question 9

two separate activity of fertilization

Answer 9

1. combining of genes derived from two parents
2. creation of new organism

Question 10

first function of fertilization

Answer 10

transmit genes from parents to offspring

Question 11

second function of fertilization

Answer 11

1. initiate reactions in egg cytoplasm that proceed development
2. restoration of diploid no. of chromosome

Question 12

Four major steps of fertilization

Answer 12

1. sperm contacts the egg
2. sperm or its nucleus enters the egg, and regulation of sperm entry
3. sperm and egg nuclei fuse
4. egg becomes activated and developmental changes begin

Question 13

process of repeated rapid mitotic cell divisions of the zygote to form the blastula

Answer 13

cleavage

Question 14

produced cell in cleavage

Answer 14

blastomeres

Question 15

blastomeres in animal pole

Answer 15

micromers

Question 16

blastomeres in vegetal pole

Answer 16

macromeres

Question 17

size of embryo during cleavage

Answer 17

does not change, blastomeres become smaller

Question 18

ball of 32 cells

Answer 18

morula

Question 19

• hollow with up to several hundred cells
• after morula

Answer 19

blastula

Question 20

cavity of blastula

Answer 20

blastocoel

Question 21

result (end period) of cleavage

Answer 21

blastulation

Question 22

mass of cells within the blastocyst in the early development of human embryo, which will eventually give rise to the definitive structures of the fetus

Answer 22

inner cell mass (ICM), or embryoblast

Question 23

outer layer which give rise to the placenta

Answer 23

trophoblast cells

Question 24

morphogenetic process that rearranges the cells of a blastula into a three-layered embryo

Answer 24

gastrulation

Question 25

three-layered embryo

Answer 25

gastrula

Question 26

gastrulation is characterized by what

Answer 26

cell movement

Question 27

cavity of gastrula

Answer 27

gastrocoel

Question 28

affects pattern of gastrulation

Answer 28

amount of yolk

Question 29

what happens to the cells at vegetal pole during gastrulation

Answer 29

invaginate

Question 30

fomrtion of a dorsal, hollow neural tube

Answer 30

neurulation

Question 31

flattened ectodermal cells during neurulation

Answer 31

neural plate

Question 32

sunken center of neural plate

Answer 32

neural groove

Question 33

elevated edge of neural plate

Answer 33

neural folds

Question 34

fusion of neural folds

Answer 34

neural tube

Question 35

fate of anterior end of neural tube

Answer 35

brain

Question 36

fate of posterior end of neural tube

Answer 36

spinal cord

Question 37

- critical structure that guides formation of several systems - form on either side of the point of fusion during neurulation

Answer 37

neural crest

Question 38

what do the neural crest cells form

Answer 38

1. dorsal root ganglia 2. postganglionic sympathetic neurons 3. many sense organs 4. all pigment-forming cells

Question 39

formation of organs

Answer 39

organogenesis

Question 40

- innermost layer - goes on to form the gut

Answer 40

endoderm

Question 41

- middle layer - goes on to form the muscles, circulatory system, blood and many different organs

Answer 41

mesoderm

Question 42

- outermost layer - goes on to form the skin and nervous system

Answer 42

ectoderm

Question 43

when does organogenesis begin

Answer 43

development of the nervous system

Question 44

first organ system to develop

Answer 44

nervous system

Question 45

induces overlying ectoderm to form the neural plate

Answer 45

notochord

Question 46

what does the ectoderm form

Answer 46

- skin and associated glands - nervous system

Question 47

what does the mesoderm form

Answer 47

1. muscles 2. skeleton 3. gonads 4. excretory system 5. circulatory system

Question 48

what does the endoderm form

Answer 48

1. lining of digestive tract 2. liver 3. pancreas 4. lungs

Question 49

- found in all body tissues except gonads - contain diploid numbers of chromosomes - replacement of dead cells - reproduce by mitotic division

Answer 49

somatic cells

Question 50

functions of somatic cells

Answer 50

1. responsible for formation of different system and organs 2. have other specific function

Question 51

somatic cells in muscular system

Answer 51

myoplast for contraction and relaxation

Question 52

somatic cells in nervous system

Answer 52

neurons for transmission of impulses

Question 53

somatic cells in digestive system

Answer 53

secretory cells for secretion of enzymes for digestion

Question 54

somatic cells of bones

Answer 54

osteoplast make hardening of bone

Question 55

- found only in gonads - contain haploid number of chromosomes - reproduce by meiotic division

Answer 55

germ cells

Question 56

function of germ cells

Answer 56

formation of gametes

Question 57

- apperas in the wall of endodermal layer of the yolk sac due to their large size and high content of alkaline phosphatase - migrate by amoeboid movement toward hind gut epithelium and then through dorsal mesentery to reach to the primordia of gonads

Answer 57

primordial germ cells

Question 58

how do the primordial germ cells migrate

Answer 58

amoeboid movement

Question 59

where do the primordial germ cells migrate to

Answer 59

- hind gut epithelium then - through dorsal mesentery to reach - primordia of gonads (primitive sex glands)

Question 60

when are primordial germ cells recognizable

Answer 60

24 days post-fertilization

Question 61

when do primordial germ cells invade the genital riges

Answer 61

6th week of development

Question 62

what does the primordia of the gonads give for the germ cells

Answer 62

chemostatic attractant

Question 63

what happens to the gonads if they fail to reach the ridges

Answer 63

will not develop