Chapter 29: Embryonic and fetal development

capacitation of the sperm

activating the sperm
- acrosome reaction to erode corona radiata

capacitation of sperm: step 1

sperm become motile after mixing with seminal gland secretions

capacitation of sperm: step 2

sperm become capable of fertilization after exposed to the female reproductive tract

what in the female reproductive tract make sperm capable of fertilization

peg cells
- expose the enzymes in the sperm that can penetrate the oocyte (gets rid of cholesterol cap)

zona pellucida

glycoprotein membrane that contains sperm receptors

corona radiata

follicular cells that protect secondary oocyte

what phase is the oocyte stuck in before it is fertilized by the sperm

metaphase II

how long will the ovum last once ovulation is occuring

24 hours

how long can sperm survive in th uterine tubes

3-5 days

how long does the journey of sperm from vagina into uterine tubes take

couple of hours

when does fertilation occur

within the first 24 hours

fertilization: step 1

- sperm rubbing against the corona radiata releases hyaluonidase
- sperm binds to zona pellucida
- sperm enters egg
- completion of metaphase Ii

Hyaluonidase

has the ability to break down corona radiata

what does the sperm binding to the zona pellucida do

acrosome releases hyaluronidase and acrosin

what do hyaluronidase and acrosin do

digest zona prllucida

what happens to the zona pellucida after the sperm has made it into the egg

it hardens so nothing else can get in

what is formed from the egg completing meiosis II

second polar body

fertilization: step 2

- sperm is absorbed into cytoplasm
- female pronucleus develops
- sperm breaks down to create male pronucleus
- see first mitotic cell division (mitosis)

first mitotic (mitosis) cell division

- chromosomes from male and female align at center
- becomes normal mitotic division

gestation

time spent in prenatal development

first trimester

pre-embryonic development
- organ begin to grow

first trimester major stages

- cleavage
- implantation
- placentation
- embryogenesis

cleavage

cells division that lead to formation of blastocyst

cleavage more in depth

rapid cell division (16 cells within 3 days)
- will reorganize itself into a blastocyst

what is the 16 cell zygote referred to as

morula

trophoblasts

outer layer of cells on the blastocyst
- will eventually become the placenta

implantation

embryo implant itself into uterus

implantation more in depth

trophoblast divide rapidly and create...
- cytotrophoblasts
- syncytial trophoblast

syncytial trophoblast

a bunch of cells that fused together to create a multinuclear structure (egg into uterine wall)

syncytial trophoblast function

- erodes uterine wall
- release hyaluronidase
- goes INSIDE uterine wall

what does the trophoblast secrete

HCG

what does HCG do

talks to ovary and tells it to not shut down corpus lutetium

why don't we want the corpus lutetium to shut down during the implantation phase

estrogen and progesterone
- helps to continue the functional layer of the embryo

placentation

formation of placenta
- connects mother and baby

embryogenesis

development of tissues and organs

second trimester

development of fetal organs and organ system

third trimester

rapid growth
- deposition of fat/adipose tissue
- organs become fully functional

Q: Process required for spermatozoa to become motile and functional

Capacitation

Q: Fusion of a sperm with the secondary oocyte results in ___ of the secondary oocyte

Activation

Q: Sperm receptors become inactive and the zona pellucida hardens after

Activation

Q: Follicular cells surrounding the secondary oocyte when it is released at ovulation

Corona radiata

Q: Process of fusion of male and female pronuclei

Amphimixis

Q: Structure formed after fusion of male and female pronuclei

Zygote

Q: Series of cell divisions after zygote formed

Cleavage

Q: Solid ball of blastomere cells formed from first few cleavages

Morula

Q: Hollow ball of cells

Blastocyst

Q: Meiosis II is completed after

Activation

Q: Regions that secrete substances that stimulate sperm motility and cause it to become functional

- Female reproductive tract
- Seminal glands (seminal vesicles)

gastrulation

the blastocyts develops layers
- ectoderm
- mesoderm
- endoderm

(will eventually form the different parts of the embryo)

extra-embryonic membranes

- yolk sac
- amnion
- allantois
- chorion

(not part of embryo)

what forms the chorion at 2 weeks

migration of mesoderm around the inner surface of the cytotrophoblast
- mesoderm and cytotrophoblast

what forms the amnion at 2 weeks

mesodermal migration around the outside of the amniotic cavity
(between ectodermal cells and trophoblast)
- mesoderm and ectoderm

what forms the yolk sac at 2 weeks

mesodermal migration around the endodermal pouch
- mesoderm and endoderm

purpose of the extra-embryonic membranes

support embryo

allantois at three weeks

endoderm and mesoderm
- connects to trophoblast

what forms at week 3

beginning of head, spinal column, and tail

chorionic villi

embryonic parts of placenta
- fetal cells

week 4

- tail fold
- head fold

week 5

- uterine cavity begins to form placental layer that interacts with villi

capsular decidua

- modified endometrial lining

what stimulates the capsular decidua

progesterone

decidua function

- exchange of nutrients, gas, and waste
- protects fetus from mom's immune system

week 10

- mucus plug
- fully formed placenta

mucus plug purpose

prevent bacteria from getting in

Q: Structure that embeds in the endometrium

Blastocyst

Q: Names of cells and cavity making up the blastocyst

Trophoblast, inner cell mass, blastocoele

Q: Structure/cells that secretes hyaluronidase to digest through endometrium

Syncytial trophoblast

Q: Process results in migration of cells to form third germ layer

Gastrulation

Q: Germ layers

- Mesoderm
- Endoderm
- Ectoderm

Q: Structure formed by germ layers

Embryo

Q: Name the extra-embryonic membranes

- Yolk sac
- Chorion
- Amnion
- Allantois

fetal: ductus venosus

bypass to allow blood go directly to inferior vena cava
- need to provide blood and nutrients
- not needed for liver function

when does the ductus venosus close

when the fetus is born

foramen ovale

bypass of lungs
- allows blood to flow from RA → LA

ductus arteriosus

lung bypass
- allows blood to flow from the pulmonary truck → aorta

Q: Transports blood from fetus to placenta

Umbilical arteries

Q: Transports blood from placenta to fetus

Umbilical vein

Q: Carries blood from umbilical vein and liver to vena cava

Ductus venosus

Q: Opening between two atria

Foramen ovale

Q: Transports blood from pulmonary trunk to aorta

Ductus arteriosus

Q: Components of placenta

- Chorion and chorionic villi
- Blood filled space between chorionic villi and decidua baslis

human chorionic gonadotropin (hCG) synthesis

by syncytial trophoblast cells / placenta
- occurs shortly after implantation

hCG function

tell corpus lutetium to keep producing estrogen and progesterone to keep the endometrium
- prevents menses

progesterone and estrogen secretion

intitally produced by corpus luteum and later by placenta
- large amount of progesterone produced after first trimester
estrogen increases near ens of 3rd trimester

what does progesterone do after the first trimester

maintain endometrial lining of uterus

estrogen end of third trimester function

stimulate labor and delivery
- once it gets high enough

relaxin secretion

by corpus luteum and plancent

what other hormone does relaxin work with

estrogen

relaxin function s

- ↑ flexibility of public symphysis so pelvis can expand
- dilates cervix (to pass fetus)
- ↓ oxytocin by hypothalamus to prevent contractions

where is oxytocin produced

hypothalamus

hormones that prepare mammary glands for milk production

- human placental lactogen
- placental prolactin
- estrogen
- progesterone

progesterone in the 2nd and 3rd trimesters

- released by placenta
- inhibitory effect of uterine smooth muscle (prevent labor)
- prevent extensive, powerful contractions

oppositions to progesterone

- ↑ estrogen
- ↑oxytocin
- prostaglandin production

(all promote labor and delivery)

what hormone makes the body more sensitive to oxytocin

estrogen
- 100x more sensitive

what hormone increases excitability of myometrium

estrogen

what hormones stimulate contraction of myometrium

- oxytocin
- prostaglandins

what hormone promotes stretch of the myometrium

relaxin

what hormones stimulate production of prostaglandin

- estrogen
- oxytocin

what does the baby do to promote contractions of the myometrium

growth and increase weight

what hormone does the fetus produce

oxytocin
- in response to estrogen