Male reproductive system Flashcards
Define puberty
Time at which reproduction by an individual animal becomes possible for the first time
Average male dog puberty age
6-12 months, small breeds at 6 and large at 12
Average tomcat puberty age
6-12 months or at 60-70% adult body weight, oriental breeds early, longhaired and manx later
What can influence onset of puberty
Photoperiod where longer days could influence puberty and also long day breeders
When can spermatozoa be found in ejaculate
6/7-9 months
When are male dogs and cats sexually active
throughout the year
Where does spermatogenesis occurs
seminiferous tubules in testes
2 cell types that makes up seminiferous epithelium
spermatogonia
Sertoli cells
What does spermatogonia do
produce sperm (germ cells)
Where is spermatogonia
basal compartment of seminiferous tubules from which sperms develop
What does Sertoli cells do
support and nourish the sperm and produce hormones
2 phases of spermatogenesis
Spermatocytogenesis
spermiogenesis
Important feature of spermatogenesis
production of sperm and number of spermatogonia is maintained
2 layers/compartments of seminiferous tubules
Adluminal compartment
basal compartment
How does spermatogenesis keep same number of sperm and spermatogonia
mitosis of spermatogonia means 1 kept(primary spermatocyte) and 1 used
What happens after the initial division of spermatogonia
Move across compartments form basal to adluminal
Name process of division from primary spermatocyte to spermatid
Undergo meiosis 1 to become secondary spermatocytes (haploid,n) and then meiosis 2 to become spermatids (haploid,n)
Name the correct sequence of cell development in spermatocytogenesis
Spermatogonia=> primary spermatocytes=> secondary spermatocytes=> Spermatids
What is spermatocytogenesis
The process of division of spermatogonia to spermatids
What is Spermiogenesis
Maturation of spermatids while they are still in the adluminal compartment to create spermatozoa
Where is the basal compartment
Near basement membrane of tubule
Where is the adluminal compartment
Towards Lumen
What is spermiation
Mature spermatids are released into the lumen of the seminiferous tubules as spermatozoa
How long does spermatogenesis in the adluminal compartment approximately take
62 days in dogs and 64 days in bulls
What is the spermatogenic cycle
Time it takes for a specific stage of spermatogenesis to reappear in the same segment
How many stages can be identified of spermatogenesis in each seminiferous tubules
4-5 stages
How is 4-5 stages of spermatogenesis per tubule calculated
Migration of basal to adluminal occurs every 14 days (14days to complete a stage)
So if total is 64 days then 64/14 days per stage then 4.5 cycles at same time
How long does it take for spermatogonia from basal to adluminal compartment/ time to complete stage of spermatogenesis
14 days in bull
What is the spermatogenic wave
It is each part of the tubule is at different stage so across the tubule sperm will be released from different parts each day across 14 days (time for stage compeletion/migration of spermatogonia) then back to start of tubule
Use of spermatogenic wave
so can keep reproducting constantly as sperm released constantly and stored and not all in one go
Why does the spermatogenic wave occur
All seminferous tubules do not contain germ cells at the same stages of the maturation
What creates GnRH
Hypothalamus by two groups of neuroendocrine cells
What are the 2 groups of neuroendocrine cells that make GnRH
Tonic centre and surge centre
GnRH stand for
Gonadotrophin releasing hormone
Tonic centre role for GnRH
Secretes GnRH in regular, brief pulses
Responsible for low-level, basal(tonic) secretion of GnRH in female and male
Surge centre role for GnRH
Inactivated early in foetal life in males and is a surge release
What does GnRH do
Stimulates secretion of both LH and FSH from adenohypophysis
at puberty pulsatile secretion of GnRH increases so FSH and LH increases
What controls the production of testosterone
LH controls the leydig cells via negative feedback system
Role of testosterone in spermatogenesis
Supports the meiotic process and stimulate Sertoli cell support of the germ cells
General roles of testosterone
Development and maintenance of libido
Secretory activity of accessory sex glands
General body feature associated with males
(Bone growth, thicken skin, deeper voice)
FSH role in spermatogenesis
Initiation of spermatogenesis at puberty and not essential for maintenance after it has been initiated (LH is required continuously)
LH role in spermatogenesis
Activate Leydig cells to control release of testosterone via negative feedback system
What does FSH do
Initiation of spermatogenesis and stimulates production of the androgen-binding protein by the Sertoli cells
What does ABP(androgen-binding protein) do
Secreted into the lumen of seminiferous tubules and binds with testosterone and other androgens to stabilize their concentrations and ensure appropriate amount for spermatogenesis
Recall Hormonal controls in spermatogenesis
insert image
What do Sertoli cells produce (FSH)
ABP
Produce Inhibin which inhibits secretion of FSH
there is also activin
Where is sperm storage
tail of the epididymis
What happens to most of the spermatozoa formed in the testes
Phagocytized in the excurrent duct system
Lost into the urine (85% sperm in urine in sexually inactive rams)
Stages of Sperm maturation to facilitate fertilisation
Development of unidirectional motility
Changes in nuclear chromatin (DNA-protein complex)
Changes in plasma membrane
loss of cytoplasmic droplet
Where do spermatozoa gain their fertilizing ability
Progressively during transit through epididymis
When do spermatozoa gain motility
mix with secretion from accessory glands at ejaculation
How long is epididymal transit
about 12 days dogs
What is an erection
increase in turgidity of the penis
How does erection occur
Increase in blood pressure in cavernous sinuses of penis
result from greater blood inflow than outflow
How does Inflow and outflow change for erection
Inflow increase through vasodilation of arteries by parasympathetic stimulation
Outflow decrease through compression of dorsal veins of penis against the pelvis when the ischiocavernosus muscles contract
What is intromission
Introduction of penis into the vagina and its maintenance within the vagina during coitus
facilitated by presence of os penis
Stages for dogs
First stage coitus-mounting
The turn- 180 degrees and dismount whilst penis remains within vagina
Second stage coitus- copulatory tie/lock
What is a copulatory tie/ lock
Stand tail to tail where the enlargement of bulbus glandis keeps penis within vagina
How long is copulatory tie
20 minutes but can be 5-60 minutes doesnt occur in cats
Stages for cats
Posture of queen in oestrus
Tomact holds queen during intromission
postcoital roll by queen
cats in occur rapidly compared to dogs
What is period of sexual inactivity after mating completed called
Refractory period
What is emission
precedes ejaculation, results from sympathetic innervation whereby semen is emptied into the urethra and provides peristaltic movement for transport from testes to urethra and contracts neck of bladder to minimize reflux of semen into the bladder
Describe ejaculation
After emission, semen is forced through urethra by reflex strong, frequent and rhythmic contraction of (urethral and bulbospongious) muscles and forceful expulsion of semen from urethra to exterior
Describe 3 fractions of dog ejaculate
1st- small volume of clear fluid ejaculated during the play period or whilst trying to locate vulva (does not contain sperm and from prostate gland used to fluid urine/cellular debris form urethra
2nd- sperm rich fluid ejaculated after intromission and during coitus
3rd clear fluid of prostatic origin ejaculated during copulatory tie and used to flush the sperm forwards through cervix into the uterus
Define ejaculation
forceful expulsion of semen from urethra to exterior
How many fractions of ejaculate for cats
one
What causes movement of sperm through female reproductive tract (3)
Contractions of female reproductive tract
sperm flagella activity(unidirectional)
Flushing mechanism(volume of ejaculate)
3 changes to spermatozoa within female tract
capacitation
acrosomal exocytosis/reaction
expression of hyperactive motility
Describe capacitation
removal of cholesterol and glycoproteins
appears reversible but after time in female tract and triggers are not present then will de-capacitate
What do capacitated sperm penetrate
corona radiata
Describe acrosome reaction
penetration of zona pellucida and sperm binding and then
–ZP3 triggers the reaction where release of enzymes needed to penetrate zona pellucida
Describe hyperactive motility
sperm and oocyte membranes fusion facilitated by sperm (hyperactive motility) combined with AR, which allows to enter perivitelline space of oocyte to be available for fertilization
3 oocyte responses to sperm
cortical and zona reaction
resumption of 2nd meiotic division
metabolic activation of fertilised ooxyte
main result of fertilisation
restoration of diploid number of chromosomes
determination of sex of neonate animal
initiation of cleavage
Paraphimosis
Inability to retract either erect or non penis into the prepuce
Phimosis
inability to protrude penis out of the preputial orifice
Priapism
Abnormally prolonged erection of penis not associated with sexual desire
uncommon in small animals
GnRH secreted by
hypothalmus
GnRH target organ
anterior pituatiary
GnRH activity
release of FSH and LH
FSH secreted by
Anterior pituitary
FSH target organ
testis (seminiferous tubules and sertoli cells)
FSH activity
Initiation of spermatogenesis
production of ABP
LH secreted by
Anterior pituitary
LH target organ
Testis (leydig cells)
LH activity
production and release of testosterone
Testosterone secreted by
leydig cells
Testosterone target organ
Testis, body, Adenohypophysis, hypothalamus
Testosterone activity
Spermatogenesis(meiosis), libido, secondary sex characteristics
Negative feedback on LH,FSH, GnRH
ABP secreted by
sertoli cells
ABP target organ
Seminiferous tubules
ABP activity
regulate concentration of testosterone
Inhibin secreted by
sertoli cells
Inhibin target organ
Adenohypophysis
Inhibin activity
Inhibit FSH secretion
