Physiology Flashcards
How long after ovulation must fertilisation occur?
within 24 hours
What does the ovum differentiate into after fertilisation?
blastocyte
what are the two parts of the blastocyst?
- trophoblast - accomplishes implantation and develops into the fetal portion of the placenta
- inner cell mass - destined to become the foetus
where is the site of implantation?
the endometrium of the uterus
what feature of the blastocyst penetrates the endometrium?
cord of the trophoblastic cells
the inner mast cells give rise to what?
the developing embryo
what are the 3 most important placental hormones?
- human chorionic gonadotropin (hCG)
- estrogen
- progesterone
what is the role of human chorionic gonadotropin (hCG)?
acts to prolongue the life span of the corpus luteum
what hormones does the corpus luteum produce increasingly greater amounts of (for 10 weeks post implantation)?
progesterone and oestrogen
what hormone does pregnancy tests detect?
hCG
In a male foetus, hCG stimulates what cells which masculinise the developing reproductive tract?
Precursor leydig cells in the fetal tests to secrete testosterone which masculinises the developing reproductive tract
What secretes oestrogen and progesterone in the 1st semester and the 2/3rd semester?
1st semester = corpus luteum
2nd and 3rd = the placenta
what is the role of oestrogen?
- stimulates growth of the myometrium, which increases in size throughout pregnancy. The stronger uterine musculature is needed to expell the fetus during labour
- also promotes development of mammary gland ducts, through which milk will be ejected during lactation
what is the role of progesterone during pregnancy?
- main role - to prevent miscarriage by supressing contractions of the uterine myometrium
- also promotes formation of a mucus plug in the cervical canal to prevent vaginal contaminants from reaching the feotus
- progesterone stimulates development of the milk glands in the breast in preparation for lactation
what is required for parturition (labour)
- dilation of the cervical canal
- contraction of the uterine myometrium
what hormone largely causes cervical softening?
relaxin
what is it called when any part of the body but the head approaches the birth canal first
a breech birth
after deliver, the uterous shrinks to its pregestational size, what is this called?
involution
what induces involution?
a fall in oestrogen and progesterone when the placenta is lost at delivery
what hormone promotes myometrial contractions that help maintain uterine muscle tine, inhancing involution?
oxytocin
what is the third stage of labour
delivery of the placenta
what is the second stage of labour?
delivery of yhe baby
what is the first stage of labour?
cervical dilation
what is oestrogens role in development of the breast during pregnancy?
promotes extensive duct development
what is progesterones role in development of the breast during pregnancy?
stimulates abundant alveolar-lobular formation
what induce the synthesis of enzymes needed for milk production?
prolactin (anterior pituitary hormone) and human chorionic somatomammotropin (hCSl placental hormone)
prolactin also stimulates milk production after parturition, how does it not stimulate during pregnancy?
stimulatory action of prolactin is blocked in later stages of pregnancy by oestrogen and progesterone but after parturition oestrogen and progesterone levels dropping allowing prolactin to induce milk production
where is prolactin produced?
anterior pituitary gland
where is oxytocin produced?
posterior pituitary gland
what is the role of prolactin?
stimulates milk production
what is the role of oxytocin?
stimulates milk ejection
how does oxytocin stimulate milk ejection?
oxytocin stimulation contraction of myoepithelial cells in the mammary ducts
what is the breast milk in the first 5 days called?
colostrum
