Group 2 - Sperm to Establishment of Preg - COMPLETE*** Flashcards
What is Spermatogenesis?
a process where spermatozoa are formed
Spermatogenesis: How long generally does it take?
- Where does it take place?
5-9 weeks
in the seminiferous tubules
Spermatogenesis: State the names of the spermatozoa starting with the earliest one 7
A spermatogonia
Intermediate spermatogonia
B spermatogonia
primary spermatocytes
secondary spermatocytes
spermatids
spermatozoa
Spermatogenesis: State the 3 general stages and explain what happens in each
proliferation - A spermatogonia undergo mitotic divisions to produce B spermatogonia
meiosis - this produces haploid spermatids and crossing over ensures their genetic heterogeneity
differentiation - this forms a cell capable of fertilisation
Spermatogenesis: Where in the seminiferous tubules does it start?
- what happens first?
- What is maintained?
- What are the cells connected by and what does this enable them to do?
at the most lateral edge
A spermatogonia undergo mitosis
a pool of stem cells
intercellular bridges enabling them to divide in unison towards the lumen
Spermatogenesis: Why do some spermatogonia not have intercellular bridges?
to replenish the pool of germ cells so continuous sperm production can occur
Spermatogenesis: What do Primary spermatocytes undergo to give secondary spermatocytes?
- What about secondary spermatocytes to give spermatids?
meiosis 1
meiosis 2
Spermatogenesis: State the 4 phases of differentiation
Golgi phase
cap phase
acrosomal phase
maturation phase
Spermatogenesis: What happens in the Golgi phase? 6
vesicles inside Golgi apparatus fuse to form proacrosomal granules
these granules fuse to form an acromic vesicle
the acrostic vesicle contains an acrostic granule
centrioles move the the base of the nucleus
the proximal centriole anchors the tail to the nucleus
the distal centriole forms the central flagellum
Spermatogenesis: What happens in the Cap shape? 3
the acrostic vesicle forms a cap structure over the top of the nucleus
the Golgi apparatus migrate and disappear
the primitive flagellum forms
Spermatogenesis: What happens in the Acrosomal phase?
the acrosome spreads and the nucleus elongates
manchette tubules are formed
the neck and annulus are formed
Spermatogenesis: What happens during the Maturation phase?
the manchette form the post nuclear cap
the mitochondria form in a spiral assembly in the middle piece
Spermatogenesis:
- What is contained within there acrosome?
- What 4 sections is the tail composed of?
hydrolytic enzymes for penetrating the zona pellucida
capitum
middle piece
principle piece
terminal piece
Spermatogenesis: What is ‘one cycle of the seminiferous epithelium’?
- How long is it?
progression through a complete series of stages at one location along a seminiferous tubule
it varies between species
Spermatogenesis: How many different sections are there on the seminiferous epithelium?
- Do the intercellular bridges extend between sections?
8
no
Spermatogenesis: How many cycles does it take for spermiation to occur?
4.5 cycles
Spermatogenesis: How long does it take primary spermatocytes to become secondary spermatocytes?
- How long does it take secondary spermatocytes to become spermatids?
21 days
1.7 days
Spermatogenesis: What is a Spermatogenic wave?
the differences at any given instant in time along the seminiferous tubule
Spermatogenesis: What is spermatogenesis dependent on? 3
GnRH secretion from the hypothalamus
FSH and LH secretion from the anterior pituitary
Testosterone and Oestradiol secretion from the gonad
Spermatogenesis: What does LH do when released from the anterior pituitary?
it binds to receipts on Leydig cells
this stimulates Leydig cells to secrete testosterone
Spermatogenesis: What does FSH do when released? 4
it binds to receptors on Sertoli cells
this enables them to function
this stimulates Sertoli cells to convert testosterone to oestradiol
and they secrete inhibin
Spermatogenesis: After Leydig cells secrete testosterone, what happens to the testosterone?
some of the testosterone is converted in oestradiol by Sertoli cells under the influence of FSH
oestradiol has a negative feedback effect on the hypothalamus
some of the testosterone diffused into the seminiferous cords
it is converted into dihydrotestosterone
dihydrotestosterone has a negative feedback effect on the hypothalamus
Spermatogenesis: Which part of the Sperm contain the mitochondria needed to generate ATP for the flagellum to propel the sperm?
the middle piece
Spermatogenesis: Once the spermatids have differentiated into Spermatozoa, what happens?
- When in the head of the epididymis, explain whether or not they can fertilise an oocyte
spermatozoa are released into the seminiferous tubule lumen
they enter rete tubules
they travel through efferent ducts into the head of the epididymis
no they cannot as they are not fully mature or motile
Spermatogenesis: how long does it take for sperm to progress through the head, body and tail of the epididymis to become fully mature?
- What is happening to the sperm as they move further down the tubule? 2
2 weeks
they become more mature and motile
the cytoplasmic droplet is moving down the sperm
Spermatogenesis:
- Is the time taken to travel through the head and body variable?
- what about to go through the tail and why?
no it is fixed
yes because the tail has limited storage capacity
What is the function of seminal plasma? 6
it provides a transport medium for sperm
it contains fructose which provides nutritional support for sperm
it has a buffering capacity to protect sperm against the acidic conditions in the vagina
it contains antioxidants to get rid of free radicals formed by sperm during ATP production
it contains proteins which bind to the sperms head
prostaglandins produced from the prostate gland causes the muscles in the female tract to contract and helps sperm progress
Semen: Where is semen deposited in the cow?
- How much is deposited?
- how long is copulation?
in the cranial aspect of the vagina
1ml
1-3 seconds
Semen: Where is semen deposited in sheep?
- How much is deposited?
- how long is copulation?
in the vagina
8ml
1-2 seconds
Semen: Where is semen deposited in the sow?
- How much is deposited?
- how long is copulation?
in the cervix and leaks into uterus
250ml
5-20 minutes
Semen: Where is semen deposited in Camelids?
- How much is deposited?
- how long is copulation?
in the vagina and leaks into cervix and uterus
8ml
5-20 minutes
Semen: Where is semen deposited in the Horse?
- How much is deposited?
- how long is copulation?
in the cranial vagina and leaks into the cervix and vagina
100ml
60 seconds
Semen: Where is semen deposited in the dog?
- How much is deposited?
- how long is copulation?
in the vagina
3ml
5-45 minutes
Post Copulation: For species where sperm are not deposited in the cervix, the sperm need to cross the cervix to enter the uterus.
- Which species form a vaginal plug?
- What is it made from?
- What is its purpose? 2
rodents
coagulated semen
to prevent further mating
to prevent retrograde transport of sperm
Post Copulation: Why must fertilisation happen quickly after copulation?
because the sperm will be recognised as foreign by the immune system and destroyed
Post Copulation: when are sperm activated?
- Describe how they move 3
- what assists the transport of sperm?
after ejaculation
they swim in a straight line
their head rotates
their flagellum moves in a wave motion
contractions of the female tract
Post Copulation: State some tail abnormalities in sperm that would result in abnormal movement and lead to lower fertility 4
coiled tail
folded tail
detached head
double mid piece
Post Copulation: Cervix
- Via which pathway do sperm cross the cervix?
- Describe the journey of sperm across the cervix 2
- What is the purpose of the barrier this mucus presents? 2
the privilege pathway
the cervix secretes sulphomucin which is a highly viscous mucus secretion which the sperm cannot swim through
the cervix also secretes sialomucin which is a low viscosity mucus secretion which the sperm can swim through
to slow down the sperm to ensure there is a sperm reservoir
to remove any non-motile sperm