Spermatogenesis, heat cycle Flashcards
Production of normal numbers of fertile
spermatozoa requires: (4)
– Endocrine regulation of the testis
– Mitotic divisions of spermatogonia
– Meiotic divisions resulting in haploid
spermatids
– Morphologic transformation of spermatids into
spermatozoa
where is GnRH recreted from
gondaotropin releasing hormone from the hypothalamus
FSH and LH secretion from
the anterior lobe of the pituitary / adenohypophysis
what cells produce spermatozoa?
leydig cells
testes are composed largely of
seminiferous tubules—coiled tubes, the walls of which contain cells that produce sperm, leydig cells.
Seminiferous tubules may constitute up to 90 percent of the testis.
precursor to testosterone in the testes
progesterone
Steps of Development of primary gametes in males (5)
Prespermatogenesis
Spermatogenesis
Spermatocytogenesis
Meiosis
Spermiogenesis
duration of spermatogenesis
approx. 30- 75 days dependent upon species
so roughly 2-3 months
what do the sertoli cells protect spermatozoa from?
the bodies own immune system
Semen ingredients
Spermatozoa & Seminal plasma/fluid
Seminal plasma is produced by (3)
Accessory sex glands
Epididymis
Ampullary gland
What are the accessory organs of the male?
paired ampullary glands
vesicular glands
prostate gland
bulbourethral glands
another name for bulbourethral gland and in which species missing and in which, well-developed
Cowper’s glands
absent in ca, well developed in su
seminal plasma purposes (5)
Optimal osmotic pressure
Constant pH
Dilution of spermatozoa
Transport media
Stimulates sperm transport in female reproductive tract
Not important for fertility.
in which species is the prostate absent and in which, well developed
absent in eq, well developed in car
paired vesicular glands contribute what percentage of seminal plasma and contains what?
60%, fructose, ascorbic acid,
prostaglandins
what stimulates sperm to begin to swim?
mixing with seminal plasma enzymes
Prostate gland contributes what percentage to seminal plasma and contains what imporant component?
5-6 % for bulls
33% enzymes for sperm activation
what component of seminal plasma do the Paired bulbourethral glands contribute?
viscous secretion for lubricating female reproductivetract and provides gel fraction in the boar
duration of spermatogenesis
man 75 days
bull 61 days
stallion 55
ram 47
boar 39
estrus cycle is divided into either
2 or 4 parts
luteal/follicular or
pro-, estrus, met-, di-
when estrus is divided into two, what are the two parts:
which one takes up a larger portion of the cycle?
luteal or follicular phase
follicular phase is shorter (approx. 20%)
(corpus luteum development and follicular development)
name the stages of the estrus cycle
proestrus 18-21 days
estrus 1-2 days
metestrus 2-5 days
diestrus 5-18 days
(anestrus e.g. during pregnancy)
the days here apply to bovine
how quickly after calving does a cow begin to cycle again
2-3 months
“Mature cows usually take about 60 days to come on heat again after calving; young cows may take 90 days or more.”
how quickly after foaling do mares begin to cycle again
Postpartum mares will have a “foal heat” 7 to 14 days following foaling, and a second cycle approximately 30 days later. Breeding on foal heat is still somewhat of a controversial practice.
how quickly after farrowing do sows begin to cycle again
sows experience lactation anestrus
factory farmed piglets are weaned at approx. 21-28 days old
after weaning the sows typically come into heat again in 3-5 days
how quickly after lambing do sheep begin to cycle again
the following autumn
Ewes are seasonally polyestrous, cycling every 16–17 days during the breeding season.
in which month of gestation does the CL regress in equine
3-5 months as the placenta begins to produce progesterone
“Individual CL appear to regress at different times in the same ovaries of individual pregnant mares after Day 100 of gestation.”
features of proestrus (3)
growth of preovulatory follicles
increase in estrogen, estradiol peak at end of proestrus
endomtetrial development
features of metestrus (5)
in cows ovulation occurs during metestrus, not estrus like in other species
estrogens go low
corpus hemorrhagicum develops
uterine contractions and some vaginal bleeding can occur
fsh stimulates follicular growth
features of diestrus (4)
is longest period of cyclicity.
progesterone is high
FSH develops 2nd wave follicles
no uterine contractions
involution of CL if no pregnancy -> release of PGF2alfa
why do bovine experience some vaginal bleeding during metestrus
estrogen withdrawl’s effect on blood vessel permeability, is considered physiological.
17-18 days post bleeding, heat should occur again (full cycle is 21 days)
how long does a CL persist in bitches?
2 months ish
length of estrus in dog
five to nine days
many sources say up to 2 weeks but that includes proestrus which is difficult to diffrentiate from estrus
dogs ovulate an immature oocyte
what estrus phase is unique to cats?
“postestrus”
because cats are induced ovulators
cat gestation duration
58-60 days
other sources say 63-65 days
How soon after giving birth can a cat go into heat?
Most queens will return to estrus about 4 weeks after weaning their kittens if it is still the breeding season.
However, it is entirely possible for a queen to return to estrus while still nursing.
horse gestation
11 months
(10-12)
name 3 polyestrus animals
sow
cow
cat (or seasonally)
name seasonally polyestrus long day breeder
horses begin to come intro estrus as days grow longer in the springtime.
(so foals are typically born the following spring)
name a seasonally polyestrus short day breeder
sheep begin to come into estrus as days grow shorter in the autumn
(so lambs are born the following spring, approx. 5 months later)
name 3 monoestrus animals
dog wolf bear
(even thought some dogs may cycle twice per year)
what percentage of spermatozoa is typically ‘imperfect’
approx. 20%
how are spermatozoa defects classified
primary
secondary
tertiary
seasonally polyestrus species cycles are regulated by what hormone
melatonin
ewe estrus cycle length?
duration of heat?
17 days
24-36 hours
mare estrus cycle length?
duration of heat?
21 days
3-8 days
sow duration of heat?
48-72 hours
bitch duration of heat?
9 days
(same goes for queen)
when might cows experience bloody vulvar discharge?
1-4 days after heat and approx. 18 days before next ovulation (?)
due to estrogen’s effects on vaginal membrane permeability.
when are cows typically inseminated afetr parturition?
50-55 days after parturition
some variation can occur of course, but 3 months is considered too long and insemination at the first post-parturition heat is a bit too soon.
