human development and aging

when must an egg be fertilized

within 12-24hrs of ovulation

how long does it take the egg to reach the uterus

72 hrs

how long does sperm remain viable after ejaculation

6 days

where does fertilization typically occur

distal uterine tube

what is the most likely chance for fertilization

intercourse a few days prior to up to 14 days after ovulation

about how many sperm actually reach the egg

200

how long does it take for the sperm to reach the distal uterine tube

30 mins

why wont the sperm be able to fertilize the egg for about 10 hours

must undergo capacitation and acrosomal reaction

changes that occur to sperm to allow them capable of penetrating an egg

capacitation

why must the sperm undergo capacitation first

they have a tougher outer plasma membrane that prevents the premature release of acrosomal enzymes

how does capacitation of the sperm occur

fluids in female reproductive tract thin plasma membrane and dilute other inhibitory factors within semen so the head becomes more fragile and permeable to calcium ions which stimulates the lashing of the tail

why does fertilization require more than 1 sperm

takes multiple to clear the path of granulosa cells and zona pellucida

when does the acrosomal reaction occur

once sperm encounters the egg

the release of penetration enzymes such as hyaluronidase and acrosin

acrosomal reaction

digests the hyaluronic acid that binds granulosa cells together

hyaluronidase

digests proteins in the zona pellucida

acrosin

why is only the maternal mitochondria passed on to the baby

egg destroys the sperm’s

what portions of the singular sperm actually enter the egg

head and middle piece

occurs right after the sperm enters egg and prevents polyspermy by causing depolarization of the cell membrane to prevent another sperm from binding to the egg; cortical granules just below the membrane release substances to push sperm away from egg (fertilization membrane)

cortical reaction

once the egg is fertilized, what is completed

meiosis II and discarding of second polar body for the chromosomes of both to mix and create a diploid set of chromosomes

first 16 days after fertilization where the zygote divides by mitosis into hundreds of cells and organized into primary germ cell layers through three main phases: cleavage, implantation, and embryogenesis

pre-embryonic stage

mitotic divisions between 30-72hrs as it travels down the uterine tube and forms blastomeres

cleavage

by the time the fertilized egg reaches the uterus, how many cells are there that resemble a mulberry called a morula

16

how long does the morula liee free in the uterine cavity and continues to divide

4-5 days

what signifies the egg being called a blastocyst

zona pellucida degrades

what are the parts of a blastocyst

trophoblast, embryoblast, and blastocoele

what part of the blastocyst eventually becomes part of the placenta

trophoblast

what part of the blastocyst becomes the embryo and develops germ layers

embryoblast

what part of the blastocyst is fluid filled space

blastocoele

when does implantation occur

6 days after fertilization

during implantation, what attaches to the endometrium and starts to grow into the uterus like roots and the endometrium reacts by growing over the blastocyst and covering it

trophoblast

during implantation, what eventually secretes HCG which stimulates the corpus luteum to continue to secrete estrogen and progesterone before eventually becoming chorion to secrete their own

trophoblast

occurs at the same time as implantation of the trophoblast where the embryoblast starts to separate from the trophoblast to create a space called the amniotic cavity; embryoblast flattens into the embryonic disc (epiblast and hydroblast)

embryogenesis

during gastrulation, what transforms into the 3 germ layers: ectoderm, mesoderm, and endoderm

epiblast

becomes the outer parts of the body, NS, and facial features

ectoderm

forms the inside parts of the body like bones, cartilage, kidneys, blood, muscles, etc

mesoderm

forms the lining of GI, respiratory, bladder, parathyroid and thyroid glands

endoderm

when is the cell called an embryo

once all three germ cell layers are complete around day 16

germ cell layers are formed and start wrapping around the yolk sac; formation of neural tube and primitive gut

embryonic stage

by the end of what week should all organs be formed

8

fraternal twins that form from two separate oocytes that were ovulates and fertilized by two separate sperm; each embryo implants separately into uterus (two placentas and amniotics sacs)

dizygotic

identical twins with same DNA due to a single fertilized egg spliti=ing into two embryos during early development

monozygotic

transparent sac that encloses the embryo and filled with amnionic fluid that protects the embryo/baby

amnion

for the first 8-9 weeks, where is the amnionic fluid within the amnion made from

mother’s placenta

after 9 weeks, what does the fetus start doing with the amnionic fluid

swallowing and urinating in it

small sac suspended from anterior side of embryo that helps form digestive tract and produces the first blood cells and future eggs/sperm

yolk sac

forms foundation of umbilical cord and becomes part of the fetal bladder

allantois

outermost membrane that contains shaggy outgrowths that penetrate the placenta called chorionic villi

chorion

development starts day 11 and ends by week 12; disc shaped organ attached to uterine wall on one side and attached to fetus via umbilical cord and is the source of oxygen, nutrients, and means of waste disposal

placenta

the way blood flows between fetus and placenta

umbilical cord

how does blood go from the fetus to placenta and contains deoxygenated blood

2 umbilical arteries

how does blood come into the fetus and contains oxygenated blood

one umbilical vein

filled with fetal blood and is surrounded by maternal blood but the two do not mix unless ruptured

chorionic vili

thin membrane that allows exchange of wastes, nutrients and oxygen but is also permeable to alcohol, nicotine, drugs

umbilical cord

by the end of the fourth week of fetus development, what should be developed

heart beginning to beat around day 22

when is the fetus’s body covered with fine downy hair and cheeselike sebaceous secretions called vernix caseosa; quickening occurs

week 20

when does the fetus begin producing surfactant

24 weeks

what are the three fetal shunts

ductus venosus, foramen ovale, and ductus arteriosus.

fetal shunt where blood from the umbilical vein bypasses the liver and continues into the inferior vena cava

ductus venosus

after birth, what does the ductus venosus close to become

ligamentous venosum

fetal shunt where most blood entering the RA bypasses pulmonary circuit before entering LA

foramen ovale

after birth, what does the foramen ovale become

fossa ovalis

fetal shunt where blood is pumped from RV to pulmonary artery which goes back to aorta to bypass the pulmonary circuit again

ductus arteriosus

after birth, what does the ductus arteriosus close to become

ligamentum arteriosus

first four weeks after birth

neonatal period

what are the respiratory physiological adaptations of a newborn

CO2 accumulates in blood during birthing process which stimulates the respiratory chemoreceptors to cause spontaneous breathing

what are the circulatory physiological adaptations of a newborn

once breathing, resistance and blood pressure in pulmonary circuit and right heart drops whihc signals closure of foramen ovale and ductus arteriosus; clamping of cord causes collapse and fibrosis of umbilical arteries and veins

what are the immunological physiological adaptations of a newborn

born with near adult levels of IgG from mom placenta which breaks down quickly after birth but baby starts to make their own soon after; lower total amounts of IgG exists around 5-6 months old so respiratory infections common; IgA in colostrum gives newborn boost against gastroenteritis

what is defined as being premature

born before week 37 with avg weight of 5.8lbs

when is age of viability

22 weeks gestation

what is one of the most common issues with premature babies

infant respiratory distress syndrome (RDS)

lack of pulmonary surfactant which causes alveolar collapse during expiration; productiion begins around 20-24 wks and there isnt enough for adequate lung function; steroids given to mom if at risk for preterm delivery

infant respiratory distress syndrome (RDS)

degeneration that occurs in an organ system after peak functional efficiency

senescence