Spermatogenesis Flashcards
What are the 3 requirements for spermatogenesis to occur?
1- continuos secretion of GnRH
2- FSH & LH secretion
3- gonadal secretions
Lh is secreted in which type of section?
Pulsatile ( 4-8/24 hrs)
LH goes to which cell that is like a Theca interna cell?
Leydig
Leydig cells secrete?
Testosterone ( P4 converted into T)
Why must LH be pulsatile?
To prevent refractory from Leydig cells
Concentration of testosterone is 100-500x higher where?
In the testes compared to levels in blood
Sertoli cells depend on what?
FSH
FSH stays how much longer than LH?
3x
Sertoli cells are like which type of cell?
Granulosa
Testosterone is converted in Sertoli cells into what?
E2 and DHT
Where does spermatogenesis occur?
Seminiferous tubules
Why is spermatogenesis consistent?
Because of the constant and consistent pulses from FSH & LH
What are the 3 phases of spematogenesis?
Proliferation, meiotic, differentiation
The phase in which synchronized mitotic divisions take place in the basal membrane and results in a diploid cell is?
Proliferation
What must happen for new spermatogonia to develop in the basal membrane?
Continuos stem cell renewal
What happens in the meiotic phase?
Number of chromosomes is reduced, crossing over and DNA synthesis
How long does it take in the bull for meiosis to occur?
18-19 days
In meiosis 1, what is the main characteristic?
Genetic diversity
What is the result of meiosis 2?
A haploid cell
In the bull, how long does it take for the spermatid to move from basal to luminal?
61 days
What’s the 3rd phase of spermatogenesis?
Differentiation
What are some things that take place in differentiation?
Transformation into spermatozoa, packaging, nucleus condensation, acrosome formation
What makes cells potentially motile?
Mitochondria
The first phase in differentiation is?
Golgi
The acrosomic vesicle formation and packaging of contents (enzymes) are events that occur in which phase?
Golgi
The acrosomic vesicle contained the granules. Where do these granules derive from?
Golgi apparatus
What centriole is responsible for implantation of tail apparatus?
Proximal
The distal centriole gives rise to what?
Axoneme
What is the 2nd phase of Differentiation?
Cap phase
In the Cap phase, what happens to the acrosomic vesicle ?
It spreads over the nucleus into and inner, outer membrane and has enzymes
The phase of Differentiation characterized by cell elongation is?
Acrosomal
The acrosome covers how much of the nucleus in the Acrosomic phase?
2/3
What 3 things form in the acrosomal phase?
Neck, annulus, manchette
The phase in which mitochondria migrate and form a spiral, the post nuclear cap forms and you can see a head, middle and principle piece is?
Maturation
What is the annulus?
The juncture between the middle and principle piece
What is spermiation?
The release of spermatozoa from Sertoli cells into lumen
Why would we package DNA in the sperm head?
To protect it during ejaculation and transport
What does the head of the spermicide contain?
The nucleus, the acrosome, and the post nuclear cap
In mammals, what shape is the nucleus of the sperm?
Oval and flat
What is kertatinized?
Chromatin
What does the tail of the sperm contain?
Middle, principle, and terminal piece
What piece of the tail is the helix?
Midpiece
The principle piece contains what?
9 microtubule pairs and 2 central fibers
What part of the tail fits into the implantation pocket?
The capitulum
What are some difference between female and male gamete production?
Females: gametes in utero, gametes every 3-4 weeks, pulsatile maturation, meiosis, and release
Males: maturation, meiosis, and release is continuous
How long does it take for negative effects to be observed in a sperm ejaculate?
2-4 weeks
How long does it take for a complete restoration of spermatogenesis to occur?
6-12 weeks
What are some causes for observing negative effects in the ejaculate?
Heat stress, fever, shipping, toxin exposure
What is the term for the release of spermatozoa in stages throughout lanes of the seminiferous tubules?
Spermatic wave
Why is there a constant supply of male gametes?
Because of the spermatic wave release
How many stages are there in the spermatic wave and in which one does the sperm actually gets released?
There are 8 stages and sperm are released in lanes in stage 8
What is the limiting factor in reproduction?
Ovulation
Male fertility, assuming no issues with copulation, can be potentially determined by ?
Morphology, motility, livability, # of normal
What are 3 ways we can evaluate sperm production?
1- Daily Sperm Production (total # sperm produced/day)
2- Production Efficiency (# sperm/day/gram of testicular parenchyma)
3- Scrotal Circumference
Which way of evaluating sperm is non-invasive ?
Scrotal circumference measures
What is the unit for SC?
cm
What is directly correlated to scrotal circumference?
Longevity in heifers as dictated by age at puberty
Which beef breeds are higher in SC measurement?
Maternal
What is the minimum SC for bulls?
34 cm
Sperm viability is described with?
Motility (ability to move progressively forward)
What leads to abnormal sperm?
Errors in production
What percent of abnormal sperm indicates that fertility is affected?
> 20%
Where are the two locations that abnormal sperm may originate from?
Testes or epididymis
A spermatozoa that has head or tail abnormalities is most likely derived from?
The testes because of faulty differentiation
What abnormalities may be observed in a sperm that underwent faulty maturation or transit?
Cytoplasmic droplets
What are some advantages to AI?
Accelerates Genetic improvement, preserves genetic diversity, and species conservation
Preservation and dilutions creates what for spermatic to survive?
A protective environment
Some properties of extender are:
Isotonic, buffer
What are two ways we can preserve sperm?
1- extend for use soon
2- frozen (may affect viability)
What is added to the extender or ejaculate to minimize ice crystal formation within the cells?
Cryoprotectant
A cryoprotectant can be ?
Permeable or non permeable
DMSO and glycerol are what type of cryoprotectant?
Permeable
An example of a Non permeable cryoprotectant is
Milk protein
What 3 things may differ between species that should be taken into consideration for preservation?
Lipid composition of membrane, decline rate, holding temps (boars@18, bulls/stallion@5 C)
Sperm depend on what entirely to survive ?
The environment
An extender provides nutrients such as?
Glucose and fructose
Are ejaculated sperm sterile?
No
Where can bacteria reside?
Sheath, Penis, urethra, glands
What antibiotics can be added to an extender?
Penicillin, liquamycin
___________ should be poured into __________
Extender poured into semen
To obtain sexed semen, how can we identify X bearing sperm?
By adding fluorochrome dye and observing those who have more dye
How much more percent of DNA is present in X vs Y sperm?
2.8-4.2% more DNA in X bearing sperm
