Physiology Unit 5- Placenta

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The Placenta : 

The Placenta Group 12Cham Choi, ChenelleHeren, Alex Keppel, Alicia Ross, & James Walker http://www.nlm.nih.gov/medlineplus/copyright.html

Placenta: Organ of Exchange : 

Placenta: Organ of Exchange Endometrium nourishes fetus Specialized exchange: maternal & fetal blood Formation of placenta & amniotic sac Placental villi anchor placenta Established & operational after 5 weeks Amniotic cavity, amnion, amniotic fluid

Function of the placenta : 

Function of the placenta Digestive system, respiratory system, & kidneys O2 & nutrients cross the placental barrier Membrane: permeable & 2 types of diffusion Infection, disease, and drugs Placental, maternal, fetal hormones

Syncytialtrophoblast : 

Syncytialtrophoblast The hormones secreted by the syncytiotrophoblast are critical for maintaining pregnancy. Courtesy Yale University School of Medicine

Crucial Placental Hormones : 

Crucial Placental Hormones HUMAN CHORIONIC GONADOTROPIN (hCG) Maintaining the corpus luteum of pregnancy Stimulating secretion of testosterone by the developing testes in XY embryos. HUMAN CHORIONIC SOMATOMAMMOTROPIN (hCS) Reducing maternal use of glucose and promoting the breakdown of stored fat for the fetus Helping prepare the mammary glands for lactation (similar to prolactin) Estrogen Stimulating the growth of the myometrium, increasing uterine strength for parturition Helping prepare the mammary glands for lactation Progesterone Suppressing the uterine contractions to provide a quiet environment for the fetus. Promoting formation of a cervical mucus plug to prevent uterine contamination Helping prepare the mammary gland for lactation

Gestation : 

Gestation Last 38 weeks after conception Physical changes in the mother Uterus expands Breasts enlarge and begin to lactate Increased output required from the cardiovascular, respiratory, & urinary systems Placental Hormones - Human Chorionic Somatomammotropin (hCS) - Parathyroid Hormone-Related Peptide (PTHrp)

Parturition : 

Parturition Two events needed before parturition can occur Cervix Dilates Third Trimester Placental Hormone: Relaxin Uterine myometrium contracts Braxton- Hicks Contraction http://creativegrace.net/wp-content/uploads/2009/03/t012886a.gif

Importance of Placental Hormones : 

Importance of Placental Hormones Placental estrogen rises during gestation Placental secretion rises throughout gestation Connexons are synthesized and inserted in plasma membranes Increases concentration of myometrialoxytocin receptors Promotes production of local prostaglandins Oxytocin Peptide hormone, produced in Hypothalamus, stored in posterior pituitary gland Initiates labor at critical threshold level

Corticotropin-Releasing Hormone : 

Corticotropin-Releasing Hormone CRH secreted by fetal portion of placenta MDrives estrogen synthesis Dictates timing of labor onset Promotes fetal lung development Indirectly stimulates synthesis of pulmonary surfactant CRH leads to DHEA in adrenal cortex Placenta converts DHEA to estrogen CRH threshold ensures labor doesn’t begin before infant has properly developed lungs

Placenta in 3rd stage of labor : 

Placenta in 3rd stage of labor 3rd stage is shortest (15-20 minutes) Separated from myometrium by uterine contractions Expelled through vagina Contractions of myometrium constrict uterine blood vessels to prevent hemorrhage

Hormones Secreted by Placenta : 

Hormones Secreted by Placenta Human chorionic somatomammotropin Contributes to mammary gland development by inducing milk production Stimulates production of insulin growth factors I and II decreased glucose use by mother mobilization of fatty acids

References : 

References Sherwood, Lauralee. Human Physiology: From Cells to Systems. 7th ed. Vol. 1. Belmont, CA: Brooks/Cole, 2007. Print. Kliman, Harvey, Placental Hormone, Departments of Pathology and Obstetrics and Gynecology, Developmental and Perinatal Pathology Unit, Yale University School of Medicine, 2009, New Haven, CT