Chapter 29.
Answers B, C, D and E are true statements, whereas A is false.
1. The menstrual cycle:
FSH stimulates the ovary ---- Ovary secretes oestrogen ---- Oestrogen in low concentration inhibits release of FSH (and some LH) by negative feedback ---- Rising oestrogen above a certain concentration threshold stimulates release of LH (and some FSH) by positive feedback ---- ovulation ---- Corpus luteum develops as a mini-endocrine organ ---- It secretes progesterone (and some oestrogen).
2. Fertilisation:
Spermatozoa arrives in time ---- One is selected ---- The zygote is formed in the uterine tube ---- Implantation in uterus ---- Placenta assumes its endocrine role as a gigantic hormone plant ---- Corpus luteum persists for some time ---- Pregnancy continues ---- Placenta releases hCG with a peak around the 10. week - Placenta releases large quantities of progesterone toward the end of pregnancy ---- At the very end of pregnancy the progesterone secretion falls ---- The uterus is sensitised by oestrogen ---- Oxytocin is released from the neurohypophysis store ---- Oxytocin is possibly the final trigger for parturition ---- The fall in progesterone allows the adenohypophysis to release prolactin (LTH) ---- This turns on the milk production ---- The milk discharge is due to oxytocin ---- Oxytocin is reflexly released by the baby’s suckling.
1. Foetal haemoglobin (F) has an oxyhaemoglobin dissociation curve to the left of the Adult haemoglobin. Accordingly, the P 0.5 is low or the standard affinity between oxygen (O2) and haemoglobin is high.
The high affinity increases the loading of foetal blood with O2 during its passage of the placenta.
At a given O2 tension in the intervillous spaces, the foetal blood leaving these villi will have a higher O2 saturation than the blood of the mother.
2. FSH stimulates spermatogenesis, and LH stimulates the Leydig interstitial cells thereby stimulating their testosterone production.
3. Suckling liberates oxytocin, which stimulates the myometrium.