Pregnancy Flashcards
describe foetal circulation
The fetal circulatory system uses 3 shunts. These are small passages that direct blood that needs to be oxygenated. The purpose of these shunts is to bypass certain body parts — in particular, the lungs and liver — that are not fully developed while the fetus is still in the womb. The shunts that bypass the lungs are called the foramen ovale. These shunts move blood from the right atrium of the heart to the left atrium. The ductus arteriosus moves blood from the pulmonary artery to the aorta.
describe changes to foetal circulation after birth
At birth, the umbilical cord is clamped and the baby no longer receives oxygen and nutrients from the mother. With the first breaths of life, the lungs begin to expand. As the lungs expand, the alveoli in the lungs are cleared of fluid. An increase in the baby’s blood pressure and a significant reduction in the pulmonary pressures reduce the need for the ductus arteriosus to shunt blood. These changes promote the closure of the shunt. These changes increase the pressure in the left atrium of the heart. They also decrease the pressure in the right atrium. The shift in pressure stimulates the foramen ovale to close.
The closure of the ductus arteriosus and foramen ovale completes the transition of fetal circulation to newborn circulation.
describe the physiological effects of fertilisation and events leading to ovulation
during follicular phase, 1 dominant follicle emerges- produces oestradiol which stimulates FSH/LSH surge and inhibits “sister” follicles.
this surge stimulates granolas cells of follicle to produce prostaglandin leading to pseduoinflammatory reaction that causes follicle to rupture and be extruded into peritoneal cavity. progesterone causes vascularisation and secretion from uterine glands.
oocyte leaves the ovary and is captured by fallopian tube. oocyte produces progesterone and oestradiol, inhibits FSH and LH production
oocyte is viable for 12-24 hours and must meet sperm in the fallopian tube within 48 hours of ejaculation
describe the process of implantation
the oocyte is in the fallopian tube for approx 3 days, reaches the uterus and implants. the oocyte trophoblast cells differentiate into 2 types, inner cytotrophoblast and outer syncytiotrophoblasts
describe decidualisation
cells near to the uterine blood vessels enlarge and store glycogen and lipid in a process called decidualisation. on embedding, maternal spiral arteries loose smooth muscle and endothelium becomes simple vascular ducts
describe human chorionic gonadotrophin (HCG)
the syncytiotrophoblasts produce HCG which is similar to LH and maintains the corpus luteum progesterone production. ventrally placenta takes over this funtion.
describe physiological affect of progesterone as pregnancy proceeds
inhibits prostaglandin production, decreases sensitivity to oxytocin, prevents premature expulsion of the foetus
inhibits immune response to the foetus
stimulates maternal ventilation so CO2 is vented off
describe changes in hormones as pregnancy proceeds
combination of foetal and placenta (foeto-placental unit) begins to produce various hormones. Oestradiol and oestrogen are eventually produced by the placenta as this develops- causes breast duct growth
HCG produced by the placenta to maintain progesterone production
prolactin from maternal pituitary increases milk production
Relaxin from the corpus luteum relaxes pelvic ligaments and dilates the cervix to prevent spontaneous abortion
Inhibin surpasses FSH production
Aldosterone production increases to enhance blood volume
Thyroid hormones increase and there is 50% reduction in PTH to maintain bone sturdiness during pregnancy
how does mother’s metabolism change during pregnancy
there is insulin peripheral resistance by HCS to maintain glucose for the foetus
the mother makes greater use of ketoacids for maternal metabolism
describe increased foetal function during late pregnancy
lung maturation occurs and surfactant production
liver glycogen is formed
development of intestinal functions
describe physiological effects associated with the transition to birth
exact initiating event remains unclear but it may be an increase in the oestradiol to progesterone concentartion ratio. also an increase in prostaglandin production. there is increased pulse frequency of oxytocin production of possible foetal origin. these signals led to uterine contractions and simultaneously mother’s oxytocin production from the posterior pituitary is enhanced. stretch of the cervix acting via spinal pathways causes further oxytocin release. at the time of birth there is closure of the foramen oval and atrophy of the ductus arterioles to complete the change from foetal to neonatal circulation
