Animal Physiology-Reproduction Flashcards
There are risks to the mother during viviparous birth. For humans, which country has the fewest deaths from childbirth and which two have much higher rates of mortality for the mothers?
Italy has very few; 3.9 out of every 100 000. Nigeria and Afganistan have much higher rates (608-1575)
Mammalian reproduction is sexual, viviparous and is followed by a long period of nurturing and feeding the young. These are life threatening strategies for the mother so why do they use them?
The offspring is more likely to survive which is good for the fitness/evolution of the species
The hypothalamic-pituitary-gonadal axis is what drives sex. Describe the process and which hormones are involved.
The hypothalamus produces Gonadotropin-releasing hormone (GnRH) which travels to the anterior pituitary stimulating the production of LH and FSH. This then goes to the gonads. In females, this stimulates the production of oestrogens and progesterone which in turn stimulates the development of mammary glands and the uterus, whereas in males, production of androgens is stimulated which builds up muscles and secondary sex characteristics
In reference to boar and bull fertility, which one produces the largest volume of sperm? Which one has more dilute sperm? Which one has more ejaculates per week?
Boar produces more semen but has a lower sperm count (more dilute than bull) and also ejaculates fewer times per week than the bull. So the boar is less productive. In addition, as his sperm count is lower it is harder to freeze than a bull’s semen that is often used to impregnate multiple females in the future
Why is the conception rate for boars (>80%) so different to that of the bull (~40% dairy)?
It is due to the fertility status of the cow. Dairy cows produce so much milk that they are in a catabolic state in early lactation which is when they should get pregnant (so they are not ready to mate again basically) whereas the boar is no longer lactating by the time she should get pregnant again so this can occur
For the sperm to impregnate a female, what must it be?
Viable, high concentration, highly motile and with few abnormalities
The production of ova by the female is essential. These are all present at birth. Describe the state they’re present in.
Present in primordial follicles (egg surrounded by a group of cells that nourish and regulate it) arrested in late prophase or diplotene stages of meiosis
Describe the pattern of ova production from pre-birth to death of a female.
Peaks at around 7 million before birth! Then reduces to around 2 million and further to about 400 000 by puberty. This seems like a huge reduction but a female will only ovulate 500 times in her life so there are still plenty. Ovulation stops at menopause and no more eggs are present. There is an end point to females most probably because older females are incapable of looking after their child. (The female also has to undergo ovulation and be able to receive the egg-so antibodies must not kill them)
What needs to happen to the fertilised egg during pregnancy?
Embryo must migrate into uterus, to implant into the wall, for the plancenta to develop successfully and then for it all to be maintained by progesterone (pro-gestation hormone!) produced by the corpora lutea
Parturition (giving birth) needs to be done at term (the right time). What switch in hormones occur?
Reduction in progesterone and increase in cortisol. This is to stimulate birth and lactation
The first milk from lactation is called colostrum. What does it contain? What occurs after the colostrum?
Immunoglobulins which help with the offspring’s immunity. Lactogenesis (start of lactation) occurs which is initiated and maintained by prolactin
Apart from prolactin, which other hormone helps with milk ejaculation?
Oxytocin from the posterior pituitary (this stage is very nutrient demanding). It stimulates a sudden release of milk- only takes 2 mins to empty breast in humans
