Lecture 17: Development II

Question 1

Morphogenesis

Answer 1

process by which animals takes shape

Question 2

gastrulation

Answer 2

embryonic tissue layers

- reorganization of hollow blastula into gastrula

Question 3

what are the embryonic germ tissue layers

Answer 3

ectoderm -> outer layer
endoderm > lines embryoynic digestive tract
mesoderm -> line between ecto & endo

Question 4

` migration in sea urchin

Answer 4

mesenchyme cells migrate from vegetal ppole into blastocoel

Question 5

invaginaton takes place at the

Answer 5

vegatol pole

Question 6

filopodia in sea urchin

Answer 6

mesenchyme cells produce filopodia which extend toward blastocoel wall

Question 7

contraction in sea urchin

Answer 7

filopodia contract and drag archenteron across blastocoel archenteron ( future digestive tube) forms from endodem cells

Question 8

fusion in sea urchin

Answer 8

archenteron fuses with blastocoel wall

Question 9

frog germ layers turn into

Answer 9

distinct set of stuructures

Question 10

frog grastulation begins at

Answer 10

dorsal side of blastula at gray cresent ( opposite side of sperm entry)

Question 11

what determines axis of development

Answer 11

sperm entry

Question 12

invagination in frogs

Answer 12

• cells on dorsal side invaginate to form blastopore producing dorsal lip

Question 13

involution in frogs

Answer 13

as a blastosphere forms , a sheet of cells spreads out of animal hemisphere ->

• rolls over dorsal lip & inward
• moves into interior
• forms endoderm and mesoderm

Question 14

what is the second step of gastrulation in frogs

Answer 14

archenteron forms and blastocoel shrinks

Question 15

3 germ layers in gastrulation

Answer 15

ectoderm - from cells remaining on surface
- endoderm - innermost layer
mesoderm - inbetween the two

Question 16

blastocyst in humans consists of

Answer 16

• trophoblast - outer layer of cell
• inner cell mass
• blastocoel - central cavity

Question 17

blostocyst reaches uterus after

Answer 17

6 days after fertilization

Question 18

what happens when the blastocyst implants

Answer 18

• trophoblast secretes enzymes
• erodes area of penetraion
• thickens and extends projections into endometrium
• 7 after fertilization

Question 19

what layers are formed by the inner mass cells

Answer 19

hypoblast (inner)

epiblast (outer layer): embryo proper, source of embryonic stem cells

Question 20

chorion

Answer 20

• sourronds embryo & all other membranes

Question 21

amnion

Answer 21

• encloses embryo in fliud filed amniotic cavity

Question 22

yolk sac

Answer 22

forms blood cells

Question 23

allantois

Answer 23

incorperated into umbilical cord -> forms blood vessels

Question 24

gastrulation in humans

Answer 24

• takes one week ( during 2nd and 3rd week)

Question 25

involution of epiblast cells

Answer 25

- form primative streak -> start of gastrulation - some epiblast cells form w mesoderm, some mix with hypoblast ( forms endodemr) , some remain on surface ( form ectoderm)

Question 26

what are the 4 extraembryonic membranes

Answer 26

amnion, chorion, yolk sac, and allantois

Question 27

seq steps of human embryonic development

Answer 27

1. ovulation 2. ferritization 3. cleavages 4. implantation 5. gastrulation

Question 28

organogenesis

Answer 28

- process of organ formation | - 1st time ebryo begins to incease in size

Question 29

nervous system

Answer 29

1st system to develop in most vertebrate embryos

Question 30

neurulation

Answer 30

neurala -> embryo at state where neurotization occurs

Question 31

neurula

Answer 31

- embryo at stage when neurulation occurs

Question 32

during neurulation

Answer 32

1. cells from dorsal mesoderm form notochord 2. induction 3. neural plate 4. neural tube develops into central nervous system 5. birth defects

Question 33

induction

Answer 33

- process by which certain cells stimulate differentiation of neighboring cells

Question 34

what happens during induction

Answer 34

developing notochord sends signal to overlying ectoderm -> thickens and forms neural plate

Question 35

neural plate

Answer 35

- embryonic region that becomes nervous system | - neural plate rolls up and forms neural tube -> chordate nerve chord is hollow

Question 36

what are the two main parts of the central nervous system

Answer 36

anterior -> brain | remainder -> spinal chord

Question 37

anencephaly

Answer 37

neural tube fails to fuse at anterior -> no forebrain

Question 38

spina bifida

Answer 38

neural tube fails to fuse in posterior region

Question 39

neural tube defect incidence decreases if

Answer 39

preggo woman gets adequate folic acid

Question 40

neural crest cells ( cell migration)

Answer 40

- develops at the neural tube - migrate in embryo - variety of tissues : nerves, parts of teeth, skull bones

Question 41

somites

Answer 41

- role in organizing segmented structure of vertebrate body

Question 42

somites contribute to

Answer 42

formation of serially repeating structures ex: vertebrae, ribs, associated muscles

Question 43

1st trimester ( 3 months)

Answer 43

1. implanted embryo secrets human chorionic gonadotropin (hCG) - main process of organogenesis

Question 44

(hCG)

Answer 44

- Functions like LH from ant pit | - maintains secretion of Progesterone's and estradione

Question 45

what happens during the first 2-4 weeks of first trimester

Answer 45

- embryo obtains nutrients directly from endometrium

Question 46

what happens with the trophoblast during the first trimester

Answer 46

mixes with endometrium -> forms placenta

Question 47

placenta

Answer 47

- organ of exchange between mother and embryo - provides nutrients and oxygen for fetus - removes waste -> excreted by mother

Question 48

umbilical cord

Answer 48

- connects embryo to placenta

Question 49

what sometimes splits during the first month

Answer 49

- inner cell mass - 2 groups of cells which develop independently - if mass doesn't separate completely = conjoined twins

Question 50

fraternal twins

Answer 50

- result from release & fertilization of two eggs = generally distinct

Question 51

at 8 weeks

Answer 51

all major structures have formed: embryo is a fetus

Question 52

end of first trimester

Answer 52

- 2 inches long & weighs 1/2 oz

Question 53

2nd trimester ( 4-6)

Answer 53

- fetus grows - uterus grows - can tell ur preggo - fetus is active

Question 54

3rd trimester (7-9)

Answer 54

- rapid growth and final differentiation of tissues and organs

Question 55

premature

Answer 55

birth before 37 weeks

Question 56

postnatal care in mammals

Answer 56

- lactation