A&P II Chapter 11: Pregnancy

the prenatal period of development

Period of time from conception until birth; consists of three phases (pre-embryonic, embryonic, and fetal periods)

the postnatal period of development

Begins at birth and continues through all states of life from newborn/infancy to childhood to adolescence and adulthood 

capacitation

Makes the sperm more motile and modified its membrane so it can fuse with the membrane of the oocyte. Mitochondria are more active to power flagella. It happens after ejaculation when the sperm has come into contact with the female reproductive tract; usually takes around 10 hours and a sperm cannot fertilize an egg until it is complete 

acrosomal reactions

The acrosome is the cap on the sperm head that allows it to penetrate the oocyte and wiggle in between cells. Acrosomal reactions are when the sperm releases enzymes from the acrosome to penetrate the egg's outer layers. It is the fusion of the acrosomes outer membrane with the sperm's plasma membrane exposing enzymes that break down the egg's protective coatings so the sperm can reach the egg. It occurs when the sperm makes contact with the egg's outer membrane (zona pellucida) 

ectopic pregnancy

When a fertilized egg implants outside of the uterus, often in the fallopian tube. It is risky as the uterus is the only thing able to sustain the growing fetus, if it isn't terminated on its own then medical intervention is needed to remove it; otherwise could rupture and result in bleeding/death 

zygote

The first cell formed when a sperm fertilizes an egg which contains a full set of chromosomes from both parents; it is the start of a new organism and carriers all genetic info needed to develop into a baby 

blastomere

A cell produced by rapid cell division (cleavage which is rapid mitotic division) and the overall cells are getting smaller as they divide and are all genetically identical and are called blastomeres 

blastocyst

A clump of cells that forms around 5-7 days after a sperm fertilizes an egg which implants in the uterine wall and eventually becomes the embryo 

implantation

When a fertilized egg attaches to the uterine lining (endometrium) and it usually happens around 6-12 days after ovulation (which is around 14 days before your next period begins) 

difference between identical and fraternal twins

Identical twins come from a single fertilized egg that splits resulting in two embryos with the same DNA. Fraternal twins form when two separate eggs are fertilized by two separate sperm 

artificial insemination

Artificial insemination (IUI) places sperm directly into the uterus to fertilize an egg. Fertilization happens inside the body. 

IVF

IVF combines eggs and sperm in a lab and then transfers the resulting embryo into the uterus. Fertilization happens outside the body 

part of the embryo responsible for producing hCG

The syncytiotrophoblast is responsible for making HCG. This is what creates a positive pregnancy test. It signals the corpus luteum to continue producing progesterone and to prevent menstruation, and supports development of embryo. 

four extraembryonic membranes

yolk sac, amnion, allantois, chorion

function of yolk sac

provides nutrition, gas exchange, blood cell production, immune support 

function of amnion

forms the amniotic sac which holds amniotic fluid to protect the fetus from injury and maintains a constant temp

function of allantois

forms basis of umbilical cord 

function of chorion

outermost membrane, transfer of oxygen, nutrients and waste between mother & fetus by developing into the fetal part of the placenta

timeline of pre-embryonic stage

First two weeks of fertilization, from fertilization to implantation 

timeline of embryonic stage

weeks 3-8

gastrulation

The movement of cells within the embryonic disk to create an embryonic cell composed of three germ layers (ectoderm, mesoderm and endoderm)

3 embryonic germ layers

ectoderm, mesoderm and endoderm

major organs derived from ectoderm

nervous system (Brain, spinal cord), epidermis (outer layer of skin) and sensory organs

major organs derived from mesoderm

circulatory system, musculoskeletal system and urogenital system

major organs derived from endoderm

lining of gastrointestinal and respiratory tracts, liver, bladder, pancreas, glands

organogenesis

It is the processes of developing organs from the three primary germ layers during embryonic development (weeks 3-8) 

timeline of fetal stage

Week 9 until birth 

placentation

The process where the placenta forms, attaches to the uterine wall and establishes a connection between the mother and fetus. It begins after implantation and the placenta grows throughout pregnancy to become an endocrine organ that produces crucial hormones 

function of the placenta

It is a temporary organ that provides oxygen, nutrients and waste removal for the fetus via the umbilical cord. Also produces hormones to regulate pregnancy and protects the fetus from certain infections as it transfers maternal antibodies to provide passive immunity 

what allows blood flow to and from the fetus

umbilical cord & placenta

placenta previa

When the placenta implants low in the uterus and covers the cervix. Most cases result in live births but some can result in premature birth or spontaneous abortion. It is dangerous to the mother as it causes the uterus to stretch to make room for growth and can cause the placenta to rupture and cause internal bleeding & infection, oftentimes doctors will do C-sections 

function of lanugo and vernix caseosa

Lanugo is the fine hair on a fetus which holds the vernix caseosa (a waxy coating) in place to protect the baby's skin from amniotic fluid and help with thermoregulation. Also acts as a moisturizer and protects against bacteria 

how long is gestation

40 weeks

definition of premature birth

if born before completion of 37 weeks

systems likely to be underdeveloped in a premature baby

Lungs, brain, digestive system and immune system. Lungs are vulnerable if surfactant is not produced, other difficulties like sucking and swallowing, hypothalamus not developed all the way so can't maintain temperature (must be kept in incubator), underdeveloped livers 

changes to mother’s reproductive system during pregnancy

uterus enlarges, gap junctions between uterine muscle cells that make the contractions regular and not chaotic, size of abdomen makes the spinal column adjust and gives back pain, breasts are sore with enlargement

changes to mother’s cardiovascular system during pregnancy

planta needs blood, fetus produces more waste as it grows, heart rate and blood pressure will rise in pregnancy, lower number of erythrocytes helps to thin the blood and can bring the blood pressure down, uterus puts pressure on blood vessels and can result in swelling 

changes to mother’s respiratory system during pregnancy

more oxygen is needed and more carbon dioxide is produced, uterus can prevent diaphragm from contracting all the way and expanding completely, nasal congestion

changes to mother’s digestive system during pregnancy

need an extra 300 calories a day with high protein, prenatal vitamins, weight gain

changes to mother’s urinary system during pregnancy

fetus produces wase and mothers kidneys must excrete and filtration rate can rise by up to 50%, progesterone signals relaxation of muscle so women have a hard time with bladder control

changes to mother’s integumentary system during pregnancy

changes in skin, pigmentation around eyes and cheekbones, stretch marks, progesterone & estrogen can decrease normal rate of hair loss in some women, their hair and nails can get thicker, nails can also get thinner

preeclampsia

Pregnancy complication with high blood pressure (hypertension) and protein in the urine that develops after 20 weeks. Leads to fetus being deprived of oxygen and the mother develops edema, can be fatal, only treatment is to deliver the baby; otherwise can result in stroke, seizures 

hormone that suppresses contraction

Progesterone, it relaxes the uterus and prevents it from contracting prematurely to allow for the baby's development 

where does initial stimulation for labor come from

The fetus body that releases hormones that trigger a hormonal surge in the mother which causes the uterus to begin contracting and the cervix to start dilating. Fetal and maternal hypothalamus secret oxytocin which stimulates placenta to secrete prostaglandins to dilate the cervix and increase strength of contractions through positive feedback loop 

3 phases of parturition

dilation, expulsion and placental state

dilation phase

regular contractions until the cervix is fully dilated at 10cm, takes around 8-24 and is the longest stage, fetus head is pushed against the cervix, at some point the amniotic sac breaks and the fluid leaks out which is the water breaking, toward the end of the state the fetus head enters the true pelvis so its head can pass through pelvic outlet

expulsion phase

time from full dilation to delivery of newborn, crowning is when the fetus head pushes through vagina, pushing happens here

placental state phase

time after delivery of newborn when placenta and attached fetal membranes (afterbirth) are delivered, takes about 30 minutes without assistance; the uterus contracts to compress blood vessels to limit bleeding and pulls placenta away from uterine wall which is key to stop bleeding (retaining the placenta can lead to blood loss for mother and increased risk of infection)

what is responsible for the dilating of the cervix

Hormonal changes – oxytocin and prostaglandins 

What hormone is responsible for the contraction of the uterus during parturition

oxytocin

What position should the fetus be in prior to delivery? 

Cephalic (head down and the back of head is facing the mother's back, the chin is tucked to the chest 

afterbirth

The placenta and fetal membranes that come from the uterus after baby is born 

apgar score

Test given to newborns at one and five minutes after birth to evaluate physical condition on a scale of 0-2 with 5 categories 

what causes postpartum depression

Rapid drop in estrogen and progesterone levels after childbirth 

hormone responsible for milk production

prolactin

hormone responsible for milk letdown

Oxytocin – milk letdown is the release of oxytocin, a hormone that causes the milk ducts in the breasts to contract and expel milk 

developmental biology

studying changes in form and function from fertilized egg through old age

embryology

study of events that occur during approx. 38 weeks of development in mother’s womb 

Prostaglandins

causes smooth muscle of uterus to contract to move the sperm deeper into the reproductive tract

secondary oocyte

large and provides the cellular machinery needed for the first week of development, is non-motile and relies on the cilia lining and uterine tubes & contractions to propel the oocyte toward the uterus; this oocyte is stuck in meiosis 2, the ovulated secondary oocyte can only be fertilized for about 24 hours

Polyspermy

when more than once cell makes it in and this is always fatal; usually additional sperm are rejected once the initial sperm makes it in

trophoblasts

outer layer of the blastocyst that facilitates implantation and forms the placenta

embryoblasts

inner group of cells of the blastocyst that will develop into the embryo itself

when implantation occurs

approx. 4-7 days after fertilization when the blastocyst begins to attach to the uterine lining

fetal development in month 3

body lengthens and growth of head slows down, ossification begins in most bones (turning cartilage into bone), bridge of nose develops, eyes are fused shut, genitals are distinguishable 

fetal development in month 4

lower ribs lengthen, nipples and hair develop, kidneys are well formed, heartbeat can be heard, develops reflexes 

fetal development in month 5

growth slows down a bit, hair is growing called lanugo on skin to help protect fetus from amniotic fluid, develops brown fat to help with heat production, mother can feel movement and skeletal muscles are contracting

fetal development in month 6

fetus gains weight, eyebrows and eyelashes, skin is wrinkled, eyelids are partially open, lungs begin to produce surfactant which is key to survival

fetal development in month 7

eyelids open completely, fat is deposited and skin is smoother, fetus turns upside down, testes are starting to descend down

fetal development in month 8 & 9

neural networks are forming, blood cells form in bone marrow, digestive and respiratory system complete development, fetal skin is less wrinkled and lanugo is shed, testes complete descent into scrotum

first trimester effects

all major organ systems are present making it most critical stage of development, also why miscarriages occur often, many women find this phase to be plagued with morning sickness, fatigue and other symptoms like breast tenderness; some do not suffer from typical symptoms  

second trimester effects

pregnancy is visible, changes in hormones as some women feel relieve from morning sickness, some feel more energetic by this time, many women movements of growing fetus 

third trimester effects

profound uncomfortable effects like abdomen enlarging, backaches, pressure on internal organs, makes breathing difficult, etc.

changes in newborn

breathing is inflating lungs for the first time, respiratory 120-140 beats per minute, changes in connective tissue as newborns lose heat so they are born with brown fat to produce heat which is metabolized and disappears over time which then makes regular fat then acts as an insulator, newborns have higher rate of water loss and require more fluid intake, neurons developing rapidly, skeleton is cartilaginous and will be converted to bone over time

postpartum period

• Immediately after birth endorphins released by pituitary gland allow mother to ignore fatigue and pain to take care of infant, and then the levels of estrogen and progesterone drop no longer needed to maintain uterine lining 

• Postpartum depression  

• Respiratory and digestive systems start to return to normal function 

• Excess fluid is removed through various ways 

• Altered pigmentation in skin usually returning to pre-pregnancy state