Placental Physiology and Disorders Flashcards
List functions of placenta.
- Diffusion of oxygen and carbon dioxide. PCO2 is 2-3x higher than maternal blood
- Diffusion of foodstuffs, facilitated diffusion of glucose via trophoblast cells, slower diffusion of fatty acids.
- Excretion of wastes such as urea, uric acid, and creatine to maternal blood
Compare early and late placenta.
- Early: thick, low permeability, small surface area, total diffusioin conductance is miniscule
- Late: thin, high permeability, large surface area, large increase in placental diffusion
Describe the oxygen pressure gradient near the end of pregnancy and why can adequate oxygenation occur with such a low pressure gradient?
- The mother has a PO2 of 50 mmHg and the fetus has a PO2 of 30mmHg.
- Even with a low pressure gradient adequate oxygenation can still occur due to fetal hemoglobin having higher affinity for oxygen than adult hemoglobin.
- Also due to Bohr effect.
Describe the Bohr effect.
Hemoglobin can carry more oxygen at a low PCO2, excess CO2 diffuses into maternal blood causing fetal blood to become more alkaline and maternal more acidic. Acidic gives up oxygen more easily and alkaline has higher affinity for it.
What is meant by the double Bohr effect?
Double Bohr effect refers to the double shift in the maternal blood and in the fetal blood.
Describe timing, secretion, effects and targets of HCG.
- Secreted: syncytial trohpoblast cells into maternal fluids, maximal secretion during 10th-12th week.
- Targets: CL and Interstitial cells.
- Function: Prevents involution of corpus luteum
- causes CL to increase progesterone and estrogen secretion
- increased CL growth
- exerts interstitial cell stimulating effects on testes of male fetus.
Describe timing, secretion, and targets, and effects of Estrogen.
- Secreted:synctiotrophoblast cells of placenta, 30X normal by end of pregnancy
- Targets and Effects:
- Uterine and Breast enlargement
- growth of breast ductal structures
- enlargement of external genitalia
- relaxation of pelvic ligaments and aspects of fetal development.
Describe timing, secretion, targets, and effects of progesterone.
- Secreted in small quantities by CL, Secreted large quantities by placenta.
- Effects/Targets:
- Causes decidual cells to develop into endometrium
- decreases contractility of uterus
- increases secretions of fallopian tubes and uterus
- may work with estrogen to prepare breasts for lactation.
Describe timing, secretion, targets, and effects of Human chorionic somatomammotropin.
Secreted: placenta during 5th week of pregnancy
Effects/Targets: Causes decreased insulin sensitivity and decreased utilization of glucose by mother, general metabolic hormone.
Describe theories as to why mothers immune system doesn’t recognize fetus as foreign.
- Lack of expression of MHC by syncytiotrophoblast and cytotrophoblast. (part of placenta)
- Paralysis of mothers immune system during pregnancy.
- Decidual immune barrier, essentially hides the baby, most likely best answer***
- Inactivation of mothers immune system components by molecules formed on fetal placental surface.
Review general principals on page 136.
2-3% of all newborns show at least one recognizable congenital malformation, and doubles when kids are diagnosed after birth.
Know causes of fetal alcohol syndrome and symptoms.
FAS
Causes and symptoms of erythroblastosis fetalis.
E
Placenta previa causes and symptoms.
d
Hydatidiform mole causes and symptoms.
d
What is Teratology?
Teratology
What is a Teratogen?
T
What is Malformation?
Primary errors of morphogenesis usually multifactorial involving a number of etiological agents including genetics and environmental factors.
Disruptions?
Disturbances in normal morphogenetic processes. For example amniotic bands, bands that get wrapped around limbs
Deformations?
Disturbances in normal developmental processes typically caused by abnormal biomechanical forces such as uterine constraints. Ex clubfoot.
Dysplasia?
D