Chapter 28: Pregnancy & Development

pregnancy

events from time of fertilization to birth of baby

conceptus

developing offspring through all stages of development

zygote

from fertilization through implantation

embryo

weeks 3-10

fetus

week 11-birth

infant

after birth

fertilization

fusing of the male (sperm) & female (oocyte) nuclei

capacitation

in order for sperm to successfully fertilize the oocyte, they must be capacitated

cleavage

period of rapid cellular division of the zygote following fertilization

morula

early stage embryo consisting of a solid cluster of 16-32 cells (blastomeres); forms 3-4 days after fertilization

blastocyst

fluid filled sphere composed of flattened cells called trophoblast cells (forms the placenta) with a small cluster of round cells on the side called the inner cell mass (forms the baby)

placentation

placenta is formed by embryonic & maternal tissues

colostrum

highly concentrated, nutrient-dense “first milk” produced by breasts during pregnancy & first few days post birth

length of pregnancy & difference between 38 & 40 weeks of pregnancy

about 40 weeks; the difference between 38 & 40 weeks of pregnancy is the level of maturity

female defenses against sperm

multi layered filtration system to eliminate the majority of ejaculated sperm

monospermy

allowing only 1 sperm to fertilize an egg

what 2 mechanisms make monospermy occur

depolarization & cortical reaction

depolarization

plasma membrane of 1 sperm fuses with the oocyte, Na+ channels open, allows entry of Na+ into oocyte; prevents other sperm from entering the oocyte

cortical reaction

once sperm has entered the oocyte, Ca2+ is released by the endoplasmic reticulum that prepares the oocyte to begin cellular division, the Ca2+ also activates the cortical reaction, releases enzymes that destroy sperm receptors on the oocyte

implantation

6-7 days after ovulation blastocyst implants into uterus; full process of implantation takes 5 days, women may spot thinking it is a period

once implantation has occurred, ______ from the embryo prevents menses

human chorionic gonadotropin (hCG)

3 embryonic membranes

form during the first 4-5 weeks of development (amnion, yolk sac, & allantois)

placenta is fully functional by the end of the __ month

3rd

amnion

sac that fills with amniotic fluid & provides an environment for the embryo to float in

yolk sac

eventually forms part of digestive tract & produces earliest blood vessels & blood cells

allantosis

structural base of umbilical cord that links embryo to placenta & eventually becomes part of urinary bladder

neurulation

ecoderm folds inward to form the neural tube, forming central nervous system

embryonic development: week 5

nervous system develops, muscles form, cartilage model of skeleton begins

embryonic development: week 6

arm & leg buds appear, heart starts beating

embryonic development: week 7

heart divides until R & L chambers, bronchi are present, intestines developing, pancreas present

embryonic development: week 8

eyelids forming, ears forming, valves form in the heart

embryonic development: week 9

fingers & toes, recognizable as human

fetal development: 10 weeks

all organs present and functioning at some level, liver begins to form blood cells, fully functional cardiovascular system, hardening of bone is beginning

fetal development: week 14

skin dermis & epidermis obvious, hair appears, crude facial features present, sex readily detected from genitals

fetal development: week 15

thumb sucking

fetal development: weeks 16-20 “quickening”

baby is strong enough & big enough that mom can feel movement

fetal development: week 18

blinking, sucking lips, kidneys attain typical structure, digestive tract glands have developed

fetal development: week 21

swallow amniotic fluid

fetal development: week 32

eyes open, period of increase in weight, bone marrow becomes sole site of blood cell formation

fetal circulation

once heart is developed we see minor differences, & O2, CO2, waste, & nutrient exchange all in placenta

foramen ovale

allows some blood to pass directly from the right atrium to the left

ductus arteriosus

most blood from pulmonary trunk bypasses lungs & goes straight to aorta; close around time of birth

fetal circulation after ductus arteiosus

other blood vessels connected to umbilical cord close off within 30 minutes of birth & eventually form ligaments

human placenta lactogen (hPL)

helps stimulate breast development & causes mom to use less glucose & more fat for energy

morning sickness

result of high progesterone

crowding of GI tract

heartburn, acid reflux, & constipation

frequent urination

early: hormones & increase in blood volume

late: pressure on bladder

congestion

estrogen & blood volume

trouble breathing

no room (although tidal volume & respiratory rate increase)

when the blood volume increases in the mom by 40%

blood pressure & cardiac output also increase

ligaments stretched due to relaxatin

softens pubic symphysis & causes waddling gait

what stimulates labor

oxytocin is released by fetus & causes the placenta to release prostaglandins

3 stages of birth

dilation, expulsion, & placental

APGAR assessment

a: appearance, p: pulse, g: grimace or reflex irritability, a: activity, r: respiration

if a woman nurses, her body continues to produce

prolactin that maintains milk production as long as it is demanded

lactation

first couple of days the mom produces colostrum which is very high in antibodies, & there are many benefits to the mom & child

temporary forms of birth control

abstinence, condom, coitus interruptus (high failure rate), female condom, spermicides, diaphragm cervical cap, birth control pills, birth control patches, birth control injection, IUDs

permanent forms of birth control

vasectomy, tubule ligation, essure