Physiology Flashcards
what are the early stages of development?
fertilisation and implantation
where is the site of fertilisation?
upper 3rd of oviduct
when does fertilisation occur?
24 hours after ovulation
what happens if fertilisation doesnt occur 24 hours after ovulation?
the ovum starts to disintegrate
how long do sperm survive in the reproductive tract?
48 hours to 5 days
how many sperm reach site of fertilisation?
0.0001%
what does the fertilised ovum divide and differentiate to become?
blastocyst
where is the site of implantation?
endometrium in the uterus
what happens during implantation of the blastocyst?
blastocyst adheres to endometrial lining
trophoblastic cells begin to penetrate endometrium
what happens after implantation?
inner cell mass differentiation which gives rise to start of amniotic cavity
what happens when implantation ends?
blastocyst is buried in the endometrium
when is the feotus in position at full term?
placentation
what does the placenta form?
kidneys
digestive system
respiratory system
how do nutrients and O2 reach the foetus?
maternal blood
acquired by mothers digestive and respiratory system
how does CO2 and waste dispose from the feotus?
transferred into maternal blood
eliminated by mothers kidneys and lungs
what travels across placenta by simple diffusion?
CO2
O2
H20
electrolytes
what travels across placenta by facilitated diffusion?
glucose
what travels across the placenta by secondary active transport?
amino acid
what travels across the placenta by receptor mediated endocytosis?
cholesterol
what are the 3 endocrine systems that interact and support the growth and devlopment of feotus?
placental hormones
maternal hormones
foetal hormones
what are the 3 most important placental hormones?
HCG
oestrogen
progesterone
what is HCG?
Human chorionic gonadotropin
- peptide placental hormone
what is the role of HCG?
prolongs lifespan of corpus luteum
stimulates secretion of testosterone
what is the CL of pregnancy?
ovarian endocrine unit
- produces oestrogen and progesterone for 10 weeks post implantation
in males, what does HCG stimulate?
precursor Leydig cells in testes
where is HCG eliminated?
urine
what does synthesis of oestrogen require?
complex interaction between placenta and foetus
what is the role of oestrogen?
stimulate growth of myometrium
- stronger uterine muscle
- mammary gland ducts
where is progesterone made?
placenta soon after implantation
when does progesterone increase to reflect placental growth?
last 7 months of gestation
what is the role of progesterone?
prevent miscarriage by supressing contractions of uterine myometrium
promotes mucus plug in cervical canal
milk glands
what is the job of the mucus plug in cervical canal?
prevent contaminants reaching foetus
what secretes both oestrogen and progesterone?
CL of pregnancy - trimester 1
placenta - trimester 2
how long is the gestation period?
38 weeks from conception
40 weeks from end of last period
what are physical changes that happen to mother during pregnancy?
- Uterine enlargement
- Breasts enlarge and develop ability to produce milk.
- Blood volume increase by 30%
- Weight gain
- Increased respiratory activity 20%
- Increased urinary output.
- Kidneys excrete additional waste from foetus.
what does parturition require?
- Dilation of cervical canal
- Contractions of uterine myometrium
what are contractions called in the last trimester, preparing for birth?
braxton-kicks
what causes cervix to soften?
dissociation of cervical collagen fibres
caused by relaxin
what is the role of relaxin?
dissociation of cervical collagen fibres
relaxes birth canal by loosening connective tissue between pelvic bones
what is relaxin?
peptide hormone produces by CL of pregnancy and placenta
what is a breech birth?
any part of body other than head approaches the birth canal first
when is oxytocin secreted?
once parturition has begun
what does oxytocin secretion do?
increases uterine secretions
where is oxytocin secreted from?
posterior pituitary
what happens during cervical dilation?
the membrane of surrounding amniotic sac ruptures. Amniotic fluid escapes out of vagina and helps lubricate the birth canal
how much can the cervix dilate?
up to 10cm
when does delivery occur?
once cervical dilation is complete - 30-90 minutes
how is the baby pushed out?
- Stretch receptors in vagina activate a neural reflex that triggers contraction of abdominal wall in synchrony with uterine contractions.
- Mother can also voluntarily contract abs.
what happens 15-30 minutes after delivery?
delivery of placenta
what is involution?
After delivery, the uterus shrinks to its pregestational size – takes 4-6 weeks
what is involution induced by?
Fall in oestrogen and progesterone when the placenta is lost at delivery
what enhances involution?
mothers who breast-feed their infants as oxytocin promotes myometrial contractions that help maintain uterine muscle tone
what do breasts develop during pregnancy?
- Develop glandular structure.
- Each duct terminates in a lobule.
- Lobule made of milk producing glands – alveoli.
- Milk is secreted from epithelial cells into lumen
what promotes duct development?
oestrogen
what stimulates alveolar-lobular formation?
progesterone
what induce synthesis of enzymes needed for milk production?
prolactin
hCS
What stimulates milk production?
prolactin
how is action of prolactin blocked in later stages of pregnancy?
high levels of oestrogen and progesterone
how can prolactin induce milk immediately after parturition?
oestrogen and progesterone levels fall
what does suckling trigger?
a neuroendocrine reflex that leads to secretion of:
- prolactin
- oxytocin
what is prolactin for?
milk production
what is oxytocin for?
milk ejection
what nutrients does breast milk contain?
water, triglyceride, lactose, proteins, vitamins, calcium. and phosphate.
In addition; immune cells and antibodies
other than nutrients, what else does breast milk contain?
immune cells and antibodies
what is the colostrum?
milk produced in first 5 days post delivery
what does colostrum contain?
lower concentrations of fat and lactose but higher concentrations of immunoprotective agents
what are advantages of breastfeeding to the mother?
- Oxytocin release triggered hastens uterine involution.
- Prolactin inhibits GnRH, suppressing FSH and LH secretion.
- Prevents ovulation, decreasing likelihood of another pregnancy
