Ch28 Pregnancy & Development

phases of development

prenatal: fertilization → birth

neonatal: birth → 28 days

perinatal: around birth

postnatal: 28 → year

embryology

study of embryonic development

first 2 months after fertilization

fetal development

start of ninth week → birth

prenatal development

embryonic + fetal development stages

postnatal development

birth → maturity

gestation

time in prenatal development

divided into 3 three month trimesters

teratogens

cause malformations by affecting embryo during periods of rapid growth, development, or specialization

drugs, viruses, radiation

first trimester

rudiments of major organ systems appear

second trimester

body shape and proportions start to change

development of organs and organ systems

third trimester

rapid fetal growth and adipose tissue deposition

organ systems are fully functional

four stages of 1st trimester

cleavage

implantation

placentation

embryogenesis

1st trimester: cleavage phase

sequence from immediately after fertilization until contact with the uterine wall

zygote → pre-embryo → blastomere → blastocyst

1st trimester: implantation

blastocyte attaches to endometrium of uterus

1st trimester: placentation

blood vessels form around blastocyst

placenta develops

1st trimester: ebryogenesis

formation of viable embryo

establishes foundation for all major systems

differentiation

selective changes in gene activity result in different types of cells

induction

chemical substances released from cells to affect differentiation of other embryonic cells

inheritance

transfer of genetically determined characteristics from one generation to the next

fertilization

fusion of haploid gametes to produce diploid gamete

in uterine tube

vehicles of chromosome delivery

spermatazoon and oocyte

capacitation

increases motility of spermatozoa

thinned head of sperm to release digestive enzymes in acrosome

FPP fertilization promoting peptide

produced by prostat gland to control capacitation

relationship of capacitation and female reproductive system

conditions in female reproductive tract facilitate capacitation

acrosome

contains enzymes hyalurodinase (follicle bond breaker) and acrosin (proteolytic)

layers sperm penetrate moving into oocyte

corona radiata

zona pellucida

acrosomal reaction

calcium dependent exocytosis of sperm when it releases enzymes and fuses with plasma membrane of egg

fast block to polysomy

plasma membrane is depolarized so that no more sperm can fuse with the egg

slow block to polyspermy

calcium released from ER stimulate cortical granules to fuse with egg plasma membrane and release enzymes

enzymes destroy sperm binding proteins and harden plasma membrane

female pronucleus

nuclear material remaining in ovum after occyte activation

male pronucleus

swollen pronucleus of spermatozoon

migrates to center of cell

amphimixis

fusion of male and female pronucleus

fertilization // conception

meiosis II finishes

cleavage

series of cell divisions resulting in daughter cells

after fertilization

name of cells from day 0 - day 3

blastomere

identical cells produced by cleavage divisions

name of cells from day 3 - 6

morula

pre-embryo is solid ball of cells

uterus reached on day 4

blastocyst

formed by blastomeres

hollow inner cavity called blastocoel

trophoblast

outer cells that separate blastocoel and outer world

provide nutrients to developing embryo

inner cell mass

clusters at one end of the blastocyte and will later become the embryo

implantation

7 days after fertilization

blastocyte adheres to uterine lining

trophoblast divides rapidly to form many layers

cellular trophoblast

cells closest to interior of blastocyst

syncytial trophoblast

outer layers of cells that fuse together while they burrow into endometrium

secrete hyaluronidase to erode through uterine epithelium

how is amnion and amniotic cavity formed

epiblast (inner disc) cells and hypoblast (outer disc) separate

yolk sac

supplies nutrients and primitive blood circulation in first 2-3 weeks before placenta is formed

becomes part of embryonic digestive

incorporated into umbilical cord

chorion

outermost extraembryonic membrane

chorionic cavity

space between chroion and embryo

chorionic vili

projections that grow out of syntotrophoblast and invade endometrium via enzyme degradation

embryonic blood vessels

form along connecting stalk which attaches embryo to developing placenta

umbilical cord

forms from folding amnion which envelops connecting stalk

allantois

finger like projection that forms during 3^rd week between yolk stalk and connecting stalk

structure that develops into urinary bladder

allantois

structures that combine to form the umbilical cord

yolk sac and stalks of allantois

structures that make up the extra-embryonic membranes

chorion

amnion

yolk sac

allantois

support and nourish developing embryo

placenta

disc shaped area where chorion contacts developing uterine wall

connects embryo to maternal blood

structures in the umbilical chord

2 umbilical arteries

1 umbilical vein

allantois and yolk sac

portions of the placenta

embryonic and maternal portions

placental membrane

separates embryonic blood from maternal blood

allows gas exchange between embryo and mom

what filters waste of the fetus

capillaries in chorionic villi

prevent maternal cytotoxic T cells from destroying fetus

summary of first trimester

summary of first trimester

gastrulation

primitive streak forms along 2 layered embryo to form a three layered structure

forms primary germ layers

endoderm

becomes digestive, liver, pancreas, inner lungs

adjascent to yolk sac

mesoderm

becomes circulatory system, lungs, epithelium, skeletal, and muscular system

NOTOCHORD

middle layer

ectoderm

hair, nails, skin, nervous system

cells of epiblast that remain

embryogenesis

body of embryo separates from embryonic disc

organs form

folding and differential growth of embryonic disc projects into amniotic cavity

2 projections that form the body during embryogenesis

head fold

tail fold

neurulation

nervous system develops from ectoderm

tissues along length of embryo form neural plate

neural folds converge to form neural tube

neural tube divides into brain structures at week 4-5

organogenesis

organ formation

second trimester

fetus grows faster than surrouding placenta

third trimester

organ systems are ready

growth rate slows

weight gain

mothers organs are displaced

maternal adaptations

increased respiratory and tidal volume

increased blood volume

increased GFR

increased nutrient and vitamin intake

enlarged uterus and mammary glands

progesterone

released by the placenta

inhibitory effect on uterine smooth muscle to prevent extensive, powerful contractions

oppositions to progesterone

rising estrogen levels

rising oxytocin levels

prostaglandin production

false labor

occasional spasms in uterine musculature cause not regular or persistent contractions

true labor

results from biochemical and mechanical factors

continued due to positive feedback

where do labor contractions start

begin in myometrium (muscular layer of uterine wall)

partution

forcible expulsion of the fetus

contractions

begin at top of uterus and sweep in wave toward cervix

occur at strong, regular intervals and increase in force and frequency

change position of fetus to move it toward cervical canal

stages of labor

dilation - 8 hours

expulsion - 2 hours

-delivery-

placental - 1 hour

dilation stage of labor

begins with onset of true labor

cervix dilates to 10 cm

fetus moves toward cervical canal

amniochorionic membrane ruptures

contractions increase steadily

expulsion stage

cervix dilation is complete

contractions reach maximum intensity

continues until fetus is emerged from vagina

placental stage

muscle tension builds in walls of partially empty uterus to tear connection between endometrium and placenta

afterbirth, expulsion of placenta

loss of blood

episiotomy

incision thorugh perineal musculature in the case where vaginal canal is too small to pass fetus

cesarean section

removal of infant through incision in abdominal wall

needed when complications arise

premature labor

true labor begins before fetus has finished developing

newborns chances of survival directly correlate to body weight at delivery

immature delivery

refers to fetuses born at 25-27 weeks of gestation

most die despite intensive neonatal care

survivors have high risk of developmental abnormalities

premature delivery

refers to birth at 28-36 weeks

newborns have a good chance of surviving and developing normally

neonatal period

transition from fetus to neonate

neonate

newborn

systems begin functioning independently

colostrum

initial secretion from mammary glands during first 2-3 days after birth

mostly proteins and antibodies to aid neonate until immune system is functional

mucins to inhibit rotaviruses

hormones involved in hormone requirement

prolactin: milk production from myoepithelial cells

oxytocin: moves milk to lactiferous ducts via contraction

contents of breast milk

water, proteins, amino acids, lipids, sugars, salts

lysozymes with antibiotic properties

milk let-down reflex

mammary gland secretion triggered when infant sucks on nipple

continues until weaning (1-2 years)