Chapter 29 Human Development

Front 1

what are the three stages from conception to birth and when do they occur?

Back 1

Germinal period
First 2 weeks of development during formation of primitive germ layers
Embryonic period
2nd to end of 8th week, organ systems develop
Fetal period
Last 30 weeks, organ systems grow and mature

Front 2

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Back 2

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Front 3

what happens once the sperm head contacts the zona pellucida?

Back 3

the perivitelline space developes, the male and female pronucleus merge to form a singe nucleus withing a zygote

Front 4

what develops in the first two weeks after fertilization?

Back 4

3 germ layers
1. endoderm
2. mesoderm
3. ectoderm

Front 5

what develops from the endoderm?

Back 5

G.I. tract

Front 6

what develops from the mesoderm?

Back 6

bones, muscle, connective tissue

Front 7

what develops from the ectoderm?

Back 7

skin and nervous system

Front 8

what happens during the embryonic period?

Back 8

2 months
organ systems develop including cardiovascular and nervous system
Fetus remains small - not much growth here

Front 9

what happens during the fetal period?

Back 9

last 30 weeks
growth
differentiation/maturation of organ systems

Front 10

what prevents polyploidy?

Back 10

after sperm's acerzome penetrates, the perivitelline space develops, which is a new protective barrier that prevents other sperm from entering

Front 11

when does the first division occur?

Back 11

Zygote divides to form 2 cells about 18-39 hours after fertilization

Front 12

describe the cells of the morula

Back 12

Pluripotent: Ability to develop into wide range of tissues

Solid ball of 12 or more cells

Front 13

what comes after the morula?

what is significant about it?

Back 13

blastocyst on day 6

first stage of differentiation occurs now

Front 14

describe the blastocyst

Back 14

hollow sphere of cells with trophoblast cells making up the outer layer of the sphere
Contains an inner cell mass that will become the embryo
With Blastocele - the empty space

Front 15

from what cells does the placenta develop?>

Back 15

the trophoblast cells

Front 16

Back 16

Front 17

what is the purpose of the placenta?

Back 17

protects the zygote

Front 18

what are the 2 layers of the placenta formation?

Back 18

cytotrophoblast
syncytiotrophoblast

Front 19

describe the cytotrophoblast

Back 19

fetal side - connects fetus to the placenta

Front 20

describe the syncytiotrophoblast

Back 20

maternal side - protects the zygote fro maternal immune cells

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Back 21

Front 22

Back 22

Front 23

the embryonic disc is composed of what?

Back 23

the ectoderm and endoderm

Front 24

how does the neural tube form?

Back 24

ectoderm develops a neural groove, a neural fold, and a notochord (together called the neural plate)
the neural groove deepens and the crest of the neural fold eventually joins forming the neural tube

Front 25

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Back 25

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Front 26

describe the gut formation

Back 26

Developing digestive tract pinches off from yolk sac as a tube but remain attached by yolk stalk
Oropharyngeal membrane
Cloacal membrane
Evaginations
Celom or body cavity development

Front 27

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Front 28

when endodermal tissue pinches off toward the front, it develops the _________

Back 28

oropharyngeal membrane = early mouth

Front 29

when endodermal tissue pinches off toward the rear, it develops the _________

Back 29

cloacal membrane = early rectum

Front 30

in what stage does the limb bud and face develop?

How does it occur

Back 30

embryonic stage (at about 28 days)

limb tissue laid down in proximal to distal sequence

Front 31

what is the epidermis derived from?

Back 31

Epidermis derived from ectoderm

Front 32

what is the dermis derived from?

Back 32

Dermis derived form mesoderm or neural crest cells as in face

Front 33

what is the skeleton derived from

Back 33

mesodermal cells

Front 34

what is muscle derived from?

Back 34

mesoderm

Front 35

what is nervous system derived from?

Back 35

ectoderm

Front 36

what is circulatory derived from

Back 36

mesodermal

Front 37

describe what happens in the heart when the baby is born and begins to breathe

Back 37

there is a decrease in pressure in the right atria, causing the septum primum and septum secundum to stick together, thus closing the foramen oval

Front 38

what does the respiratory system develop from?

urinary?

reproductive?

Back 38

endoderm

mesoderm

mesoderm

Front 39

what are the three parts of a developing kidney?

which ones are vestigial?

Back 39

pronephros, mesonephros, meetanephros

pronephros and mesonephros are vestigial (degrades from primitive stages)

Front 40

describe kidney development

Back 40

pronephros is the first urinary structure to develop, it degrades and the mesonephros takes over, then the metanephorse takes over and becomes the permanent kidney

Front 41

describe reproductive system development in females

Back 41

E2 causes mesonephric ducts to degrade and the paramesonephric duct to develope which becomes the uterine tube

Front 42

describe reproductive system development in males

Back 42

gonadal ridge releases testosterone causing the paramesonephric duct to develop into the vas deferens

Front 43

what is the vernix caseosa?

Back 43

waxy coat of protection that protects the fetus from amniotic fluid containing fetal wastes

Front 44

what happens at 60 days?

Back 44

embryo becomes a fetus

Front 45

describe the stages of parturition

Back 45

first stage - getting ready to expel fetus - minimal uterine cxn and cervix dliation
second stage - maximal uterine cxn and cervix dilation - fetus expelled
third stage - placenta expulsion

Front 46

why is it important that the placenta be expelled?

Back 46

because it dies and it would cause infection if it remained in the mother

Front 47

why does parturition start?

Back 47

in response to stress b/c of the small space, the Fetus pituitary releases ACTH which influences adrenal cortex to release adrenal steroids which changes the hormonal levels of the placenta including P4 synthesis decreases and E2 synthesis increases, and prostaglandin synthesis increases, which causes cxn to begin.

Front 48

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Front 49

What type of feedback occurs in the parturition process?

Back 49

positive feedback
the uterine cxn stimulate maternal hypthalamus to stimulated oxytocin release from anterior pit. Oxytocin increases uterine cxn, which causes more oxytocin to be released, more and more and more

Front 50

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Front 51

what are the structures that cause the foramen ovale to close after birth?

Back 51

primum on the left, secundum on the right,
stick together, closing the f.o.

Front 52

define genotype

Back 52

Actual set of alleles a person has for a given trait

Front 53

define phenotype

Back 53

Person’s appearance or expression of the trait caused by the genes

Front 54

gene

Back 54

a piece of DNA that controls a trait

Front 55

sex-linked traits are...

Back 55

Traits affected by genes on sex chromosomes

Front 56

incomplete dominance

give i.e.

Back 56

Dominant gene doesn’t completely mask effects of recessive gene
Sickle-cell disease

Front 57

polygenic traits are determined by....

give i.e.

Back 57

expression of multiple genes on different chromosomes
Person’s height, eye and skin color, intelligence

Front 58

define homozygous

Back 58

alleles are the same
i.e. TT

Front 59

define heterozygous

Back 59

alleles are different
ie. Tt

Front 60

define dominant-recessive:

Back 60

dominant allele masks a recessive allele

Front 61

define codominance or incomplete dominance

Back 61

each allele exerts an effect on the phenotype, one allele does not mask the other, the two alleles blend

Front 62

if a Tt mother and a TT father combined, what would you get in a incomplete dominance situation?

Back 62

add Punnett Square

Front 63

if a homozygous dominant mother combined with a heterozygous father, what would you get in a dominant-recessive situation?

Back 63

add Punnett Square