Pregnancy and Human Development Flashcards
Define Conceptus
developing offspring
define gestation period
time from last menstrual period until birth ( ~280 days)
Define embryo
conceptus from fertilization to week 8
Define fetus
conceptus from week 9 until birth
Define pregnancy
the events that occur from fertilization to birth
How long can a oocyte live
12-24 hrs
How long can sperm live
24-48 hrs
When must sexual intercourse occur for fertilization
sexual intercourse must occur between 2 days before ovulation to 24 hrs after
Define fertilization
combination of the genome of the sperm with that of the secondary oocytes
What is diploid zygote
haploid sperm and haploid egg
What happens right when ejaculation into the vagina happens
- sperm leaks out of the vagina immediately after
- a lot of sperm are destroyed by the acidic environment of the vagina
- a lot of sperm also fail in through the cervix
- the sperm could also be killed by the phagocytes
- only a few make it to the uterine tubes ( 100- a few thousands)
What are 3 things needed for sperm to make it to the egg?
1) they must be motile
2) they must also be mature( CAPACITATED)
3) membrane of the sperm also weaken by female tract secretions
What 3 things occur when a sperm is mature/ capacitated
making the membrane of the sperm fragile
allows it to release enzymes
which causes penetration through the secondary oocyte
What are the 2 protective covering of the ovum
corona radiata( made of follicle cells; a layer of protection) zona pellucida ( the protective thick membrane around the egg)
What are the 4 steps to sperm penetrating
1) the sperm must breach the secondary oocyte coating
2) sperm squeezes through the corona radiata
3) it then binds to the zona pellucida
4) sperm enzymes digest holes through the zona pellucida( autosomal reaction)
5) fusion happens between sperm and egg membranes
6) sperm’s cytoplasmic contents then enter the secondary oocyte
7) only one sperm can penetrate through the oocyte ( monospermy )
What happens when 1 sperm enters the egg
1) cortical reaction
2) enzymes released ( zonal inhibiting proteins ZIP)
What do ZIPs do?
destroy the sperm receptors that are still on the zona pellucida ( slow block)
What also causes completion of meiosis 2( oogenesis)
Calcium
What forms after completion of meiosis 2 ( female physiology)
ovum and second polar body
Define male pronucleus
sperm chromosomes enter
stays separate from the female pronucleus ( ovum genome)
Define fertilization
when membranes of 2 pronuclei rupture and chromosomes combine
Define cleavage
first mitotic divisions of zygote
while zygote moves toward the uterus
When does the first cleavage happen
36 hrs = 2 daughter cells
What happens at 72 hrs during embryonic development
morula ( 12-15 cell stages)
Define what forms at day 4 or 5 of embryonic development
blastocyst
When does an embryo form (cell wise and location)
100 cells
reaches the uterus
Define blastocyst
fluid filled sphere
What are the 3 parts of the blastocyst and its function
trophoblast cells ( helps with placenta formation) inner cell mass ( ICM): becomes embryonic disc, makes the embryo and 3 embryonic membrane )
When does implantation happen
blastocyst floats around for about 2-3 days
implantation happens 6-7 days after ovulation
Define implantation
inflammatory like response occurs in endometrium
What 2 layers does trophoblasts divide into during inplantation
cellular trophoblast
syncytial trophoblast
During inplantation what does the blastocyst do
burrow into lining
endometrial cells cover the blastocyst and seal it in
When is implantation completed
12 days after ovulations
How does the female body prevent menstruation during pregnancy
regulated byhormones ( progesterone)
Define placentation
placenta formed from both mother and embryo
Define Chorion
outermost fetal membrane that develops
part of the amniotic sac
formed from part trophoblast and part ICM
Define chorionic villi
form from the chorion
- penetrates into endometrium
- barrier and exchange are between embryo and mom blood vessels extend through the chorionic villi
- they extend to the embryo as umbilical arteries and veins
Do maternal and embryonic blood supplies normally mix
no
What membrane create a barrier between mom and fetus through placenta
chorionic villi
aided by endothelia of embryonic capillaries
When is the placenta is fully formed and functional
by the end of the third month
What does the placenta function as
- nutrition
- respiration
- excretion
- endocrine function
What happens if placental hormones are inadequate
pregnancy will be aborted
What hormones increase throughout pregnancy to prepare for mammary glands for lactation
estrogen and progesterone
During the implantation what 3 steps are part of the germ layer
blastocyst converts to gastrula
1) inner cell mass> embryonic disc
2) three primary germ layers from
3) extraembryonic membranes develop
What is the function of the amnion
- transparent sac with amniotic fluid
- provides buoyant environment that protects embryo
- maintains constant temp
- allows freedom of movement
- comes from maternal blood and fetal urine later on
Define the yolk sac
- sac that hangs from the anterior surface of the embryo
- forms part of the digestive tube
- source of earliest blood cells and blood vessels
When does gastrulation occur and what forms
in week 3
embryonic disc
Define embryonic disc
3 layered embryo with primary germ layers
What are the 3 layers of the embryonic disc
ectoderm
mesoderm
endoderm
When does gastrulation occur
begins with primitive streak
establishes the longitudinal axis of the embryo
What cells form the endoderm
cells that move into the groove
What cells form the mesoderm
cells then push laterally from the groove
What are the steps of the formation of the embryonic disc
1) Endoderm
2) mesoderm
3) ectoderm
What is the notochord
a rod of mesodermal cells
Define ectoderm
cells that remain on posterior surface
Do all organs form from the 3 germ layers
yes
What does the ectoderm form
nervous system, skin epidermis
What does the endoderm form (4)
epithelial cells of the digestive,respitatory, urogenital systems and associated glands
What does the mesoderm form
everything else
Define organogenesis
formin the organs and systems of the body
starts at the 8th week ( end of embryonic period)
During organogensis what happens in the endoderm
folding the endoderm: primitive gut
forms the epithelial lining of the gi tract
organs of the gi tract start to from
oral and anal opening form
then mucosal of the respiratory tract form
development of the glands
During organogenesis what forms in ectoderm
the first big even of organogenesis
leads to development of brain and spinal cord
notochord sends out chemicals to start the process
neural pate forms from the ectoderm thickening then fold inward to form neural folds
What happen at day 22 of organogenesis
neural folds fuse together
leads to the formation of neural tube
Describe the neural tube
the anterior end becomes the brain the rest ( beside the anterior end) = spinal cord
Define the neural crest cell (4 body component it forms)
move far around cranial, spinal, and sympathetic ganglia nerves adrenal medulla pigment cells of skin some connective tissue
What happens at 3 months
first brain wave
What happens to the mesoderm during organogenesis
first appears with notochord
3 clumps of cells appear to the sides of notochord
somites
lateral plate
What 3 clumps of cel appear side of notochord
1) somites
2) intermediate mesoderm ( gonards and kidneys)
3) lateral plate mesoderm
Define somites
40 pairs that create the following
vertebra and ribs
skin
skeletal muscles ( neck,trunk,limbs)
Define lateral phase of the mesoderm during organogenesis
ventral side dermis most tissue within limbs parietal serosa heart and blood vessels connective tissues almost entire wall of digestive and respiratory organs
When does fetal circulation develops
first blood cells are within yolk sac
by the end of the 3rd week: embryo has system of paired vessels. two vessels fuse form the heart which bends into S shape, heart beats start at 3.5 weeks
How does the mom change during pregnancy
1) reproductive organs are full of blood
2) chadwick’s sign: vagina has purplish hue
3) breast enlarge and areolae darken
4) facial skin pigmentation can increase
5) weigh gain about 28 lbs
6) 300 additional calories needed each day
7) multivitamins recommended i.e folic acid
8) gi tract: morning sickness from high levels of estrogen and progesterone, heartburn and constipation common)
9) urinary system( high urine production from higher material metabolism and fetal wastes,frequent, urgent urination
How does respiratory system of the mother change during pregnancy
- estrogens cause nasal edema and congestion
- tidal volume increases ( heavier normal breathing)
- difficult breathing may happen later in pregnancy
How does pregnancy affect the cardiovascular system of the mother
blood volume increases ( 25-40%)
helps protect from blood loss during childbirth
cardiac output increase 35-40%
varicose veins could form from increased pooling of blood and impaired ability for venous blood to return from lower limbs
What initiations labor
positive feedback loop
Who determines the birth date
the fetus because it gets stressed and releases cortisol
cortisol causes drop in estrogen and progesterone in placenta
What causes uterine contractions
prostaglanains secreted from placenta
leads to Braxton Hicks contractions in uterus
What stimulates oxytocin during initiation of labor
stretch receptors ( from the induced contractions)
What causes greater uterine contractions and more prostaglandins release from uterus
oxytonin and prostaglandins
What causes an increase in cervical distension during labor
the uterine contractions and more prostaglandins release from uterus
this creates a loop of increasing contractions
What happens after cervical distension
more oxytocin and prostaglandin release> greater contracrions > greater distention of cervix
What occurs during dilation of labor
longest stage of labor: 6-12 hrs ( or more)
contraction start off weak ( 15-30 min apart and 10-30 sec long) and become more vigorous and rapid
cervix dilates fully to 10 cm
the amnion ruptures and releases amniotic fluid
head enters the true pelvis ( engagement)
What happens during birth phase of labor
full dilation> delivery of infant
strong contractions every 2-3 mins and 1min long
urge to push increases ( w/o anesthesia)
define crowning
largest dimension of head at the vulva
Define vertex position
head first
skull dilate cervix
breathing starts before complete delivery ( from early suctioning)
Define breech position
butt first
delivery more difficult
often requires forceps or c-section
What occurs during the placental phase of labor
strong contracts cont
causes placenta to detach and uterine blood vessels to compress
limits the bleeding
and allows placenta to detach
delivers “ afterbirth” placenta and membrane delivery
happens 30 mins after birth
all of placenta must be expelled to prevent postpartum bleeding
Describe the baby first breath
needs tremendous efforts because airways are tiny and lings are collapsed
increase of carbon dioxide starts process of “ needing to breathe”
What is the respiratory rate of new born
45/min first 2 weeks then decline
How is premature infants breathing different
need respiratory assistance until lungs are mature ( surfractants not fully developed)
What produce milk
mammary glands
what hormone is released for lactation
prolactin
takes about 2-3 days to start
What happens the first 2-3 days of lactation
production of colostrum
less lactose but more protein,vitamin A,mineral, and almost no fat
yellowish and full of antibiodies
When does true milk is created
after production of colostrum
When does prolactin declines
after birth of baby
What continues lactation
continued from sucking of nipples
suckling> more prolactin release> then stimulates more mild production
What are 4 benefits of breastmilk
1) natural laxative
2) helps woth bacterial colonization of large intestine in baby
3) women can lose bone calcium but it is replaced after weaning ( so long as diet is healthy)
4) women can also start ovulating again during breast-feeding
