Spermatogenesis and Semen Evaluation Flashcards
What cells do you start and end with in spermatogenesis
START - Spermatogonia 2. primary spermatocyte 3. secondary spermatocyte 4. spermatids Finish Spermatozoa
Goals of spermatogenesis
- Produce spermatozoa
- Replenish supply of primordial stem cells spermatogonia so can continue process
- Genetic diversity
NAme the phases of spermatogenesis
- Proliferation phase
- Meiotic phase
- Differentiation Phase
Talk about the 1st phase of spermatogenesis
- Proliferation Phase (mitosis) (spermatocytogeneis) to create spermatocytes!
a. Begins with spermatogonia (v boring primordial stem cells)
b. Finishes with spermatocytes
Talk about the 2nd phase of spermatogenesis
- Meiotic Phase (spermatidogenesis) - creates spermatids
Talk about the final phase of spermatogenesis
- Differentiation Phase (spermiogenesis) - NO cell division occurring or replication. All that occurs is round spermatids undergo amazing transformation to the sperm we know = spermatozoa
Where does the process of spermatogenesis occur?
- Across the wall of the seminiferous tubule
2. Ends with release of final spermatozoa into lumen of SIT
Once spermatozoa are in the lumen of the seminiferous tubule, where do they go?
- lumen of seminiferous tubule to rete testis
- Rete testis to efferent ductules
- ED to head of epididymis
- Head to body, body to tail of epididymis
Once spermatozoa and in lumen of seminiferous tubule how are the spermatozoa presented?
- Heads buried in cytoplasm of sertoli cells, tails in lumen
TALK ABOUT SERTOLI CELLS!
- Spermatozoa head buried within, tails in lumen in seminiferous tubule
- NERVE cells.
- Span from basement membrane all the way across the lumen
- Sertoli cell role: provide support of spermatogenesis, nutrition for cells and clean up any dead cells
- They produce fluid in lumen of seminiferous tubule and helps move spermatozoa along
- Involved in hormonal regulation
- Provide nutrition for cells
- Sertoli hold hands v tightly with eachother (TIGHT JUNCTIONS) which physically divides wall of seminiferous tubule into 2 compartments, SPERM TESTIS BARRIER
- Compartment adjacent to lumen - adlumenal compartment
- Compartment nearest basal membrane = basal compartment
Name the cell types and where it is located during spermatogenesis
- ## Spermatogonia - basal compartmentSperm testes barrier
———————
Spermatocyte
Spermatids
(Spermatozia) in Adlumenal compartment
What kind of cell division occurs during from spermatogonia to Spermatids
- Proliferation = divisions, number depending on species, all mitosis, genetically Identical cells. = spermatogonia and in basal membrane of seminiferous tubule
- Spermatogonia - primary spermatocyte - secondary spermatocyte = meiosis. X over, random assortment- haploid genetically unique daughter cells.
SPERMATIDS
How long does spermatogenesis take?
Roughly 1-2 months Man - 64 Bull - 61 Stallion - 58 Ram - 49 Boar - 34
What stage is the longest in spermatogenesis?
- Primary spermatocyte to secondary.
1. primary 18-19 days! secondary 1- 1.7 days
Final phase (HH doesn’t want us to know but generally
- Differentiation from round spermatid to cell that:
- has enzymes that can hydrolyse through the egg cell zona pellucida to enable fertilisation
- is motile
Anatomy of spermatozoa head
from tip to start of tail: 1. Acrosome - contains hydrolytic enzymes required for penetration of zona pellucida 2. Nucleus 3. Post nuclear cap 4. Centriole NOTE shape varies between species
How to know the daily sperm output?
- Look at testical size
2. Correlation between size adn output
Tail
- Self powered flagellum
Composed of middle piece, principle piece, terminal piece
Things to remember
– Stage of spermatogenic cycle differs in adjacent regions of tubule.
– Finite region of tubules releasing sperm at a given time
– NOT a wave in the sense that the cells travel down the tubules. But rather, in the sense that each section contains different stages of development
Location of spermatozoa at any one time after made!
- Spermatozoa produced in testes
- Mature in HEAD and BODY of epididymis
- STORED in TAIL of epididymis until ejaculation
Endocrine regulation of spermatogenesis. What structures involved
- Hypothalamus
2. Anterior Pituitary
Endocrine regulation of spermatogenesis - what happens in hypothalamus
- Release of GnRH which acts of Anterior pituitary
Endocrine regulation of spermatogenesis- what happens in AP
- The release of GnRH from Hypo produced 2 hormones LH and FSH
- LH acts of leydig cells between the seminiferous tubule, produce TESTOSTERONE
- T acts on sertoli cells, helping function
- FSH acts on sertoli cells, for function and they secrete inhibin
Importance of testosterone
T is crucial for spermatogenesis to occur. SIT bathed in T.
It is produced from LH acting o Leydig cells
Negative feedback mechanisms of endocrine regulation
- Testosterone released from Leydig cells, negatively feeds back to acts on HYPO and AP
- Inhibin released from Sertoli cells negatively feed backs to act on AP
How long does transport through the epididymis take?
Head- body - tail
1-2 weeks
When spermatozoa mature what is a key process that happens?
- Mature - develop motile capacity!
Clinical relevance with regard to time taken for spermatozoa to be produced
presented with infertile male, examine and fine, could be that because takes between 1-2 months, animal suffered transient insult to spermatogenesis 1-2 months ago (freezing temp or fever). Now just seeing affects. Give time and fertility will increase again as takes 1-2 months for spermatozoa to be produced again!
Clinical relevance of the sperm testis barrier
immune cells would destroy the genetically different cells otherwise. Downside is certain pathogens that are small enough can pass barrier into testis without being destroyed by immune system – can invade system from there – immunologically privileged site
• if animal has a temperature then sperm can be fried, if weather is cold – sperm will die takes 1-2 months to recover
Semen evaluation
- Record volume, colour, appearance
- NB EEJ (electric ejaculation) sample cf. natural service - more dilute accessory gland secretion
- VERY careful with collection and handling!!!! Because little sperm are easily destroyed
- water, pH changes, cig smoke, temperature (keep at 37 DC), bright light can kill them all
Mass motility or wave motion score: 0-5
Score 5 / 5 (billowing clouds!) Very good – in bull but never in stallion
Score 4 / 5 (clouds!) Good 70-80% alive
Score 3 / 5 Fair 45-65% alive – more grainy
Score 2 / 5 Poor 20-40% alive, slower
Score 1 / 5 Poor <20% alive
Score 0/5 Nothing is moving
What is progressive motility?
looks at individual spermatozoa in a population to see whether they move in a straight line/circles.
Semen is the collective name for the fluids released at ejactulation:
Name the different fractions
– Pre-spermatozoal fraction (watery).
– Spermatozoa rich fraction (creamy).
– Post-spermatozoal fraction (gelatinous).
