Placenta Physiology and Development Flashcards
Functions of the Placenta
Metabolic- metabolizes glycogen, cholesterol, and fatty acids for energy
Endocrine- uses precursor molecules such as cholesterol, estrogen, or protein to synthesize both peptide and steroid hormones
Peptide hormones produced by placenta
hCG human placental lactogen (HPL) ACTH corticotrophin releasing hormone relaxin inhibin
Steroid hormones produced by placenta
estrogen
progesterone
What does relaxin do?
quiets the myometrium facilitates decidual reaction remodels collagen helps soften cervix affect cartilage of maternal skeletal system
What does DHEA-S do?
essential precursor to placental synthesis of estrogen
What role does estrogen play in gestation?
- Prepares the endometrium for pregnancy
- stimulates phospholipid synthesis
- enhances prostaglandin production
- promotes uterine vasodilation
- prepares breasts for breastfeeding
- increases fetal lung surfactant production
What role does progesterone play in gestation?
- Essential for preparation of the endometrium for implantation
- maintains quiescent uterus
- inhibits prostaglandin development
- inhibits maternal cell-mediated immune system
- reduces CO2 sensitivity in maternal resp. center
- Inhibits prolactin secretion
- relaxes maternal smooth muscle
- causes increase in maternal temp
- increases cervical mucus and formation of mucus plug
role of hCG
maintain corpus luteum
promotes vasodilation and relaxation of uterus
stimulates the male testicle to secrete testosterone
stimulates maternal thyroid
promotes secretion of relaxin
role of hPL
maternal lipolysis
increases maternal insulin resistance
angiogenesis
increases synthesis of lipids
role of Human Chorionic Adrenocorticotropin (ACTH)
promotes fetal lung maturation
plays role in timing of labor
role of corticotrophin-releasing hormone
- Acts to increase ACTH secretion from trophoblast
- causes smooth muscle relaxation in blood -vessels and uterus
- facilitates maternal immunosuppression
- near term contributes to genesis of labor
role of inhibin
acts with other hormones to decrease release of FSH, which stops ovulation
role of syncitiotrophoblast
the outer layer of blastocyst. sends out fingerlike extensions that take in uterine cells as it invades the endometrium
The syncytiotrophoblast cells secrete both peptide and steroid hormones important to the maintenance of pregnancy
role of cytotrophoblast
inner layer, secretes peptide hormones need for the pregnancy;
In early development, contains the embryo, amnion, and yolk sac
After the end of the 2nd wk, small projections of the cytotrophoblast extend into the syncytiotrophoblast to form primary chorionic villi
what are villous trophoblasts?
they give rise to the chorionic villi, which primarily transport oxygen, nutrients, and other compounds between the fetus and mother
what are extravillous trophoblasts?
migrate into the decidua and myometrium and also penetrate maternal vasculature, thus coming into contact with various maternal cell types
Four main modes of transport for substances across the placental membrane
simple diffusion
facilitated diffusion
active transport
pinocytosis
simple diffusion
movement from higher to lower concentration
- gases
- drugs
- steroids
- electrolytes
facilitated diffusion
movement that needs a transporter but no energy
- glucose
- cholesterol
active transport
movement against a concentration gradient that requires energy
- amino acids
- vitamins
- transferrin
- calcium
- iodine
pinocytosis
carrier molecule is required to engulf the molecule and move it across the placental barrier
igG
Immunological status of placenta
Fetal semi-allograft survival may be explained by immunological neutrality
immunologically inert and therefore unable to create a maternal immune response
Villous trophoblast cells lack MHC class I and II antigens
utero-placental circulation
two arteries and a vein
umbilical cord goes from fetus umbilicus to placenta
Deoxygenated venous-like fetal blood flows to the placenta through two umbilical arteries
Umbilical vein brings oxygenated blood, nutrients back to the fetus from the placenta
The umbilical vessels are contained with the cord and surrounded by wharton’s jelly, a gelatinous connective tissue
What is aerobic metabolism?
energy production in the presence of oxygen
fetus uses glucose to convert to ATP
