REPRO - Male Flashcards
What is the normal volume of the testes, measured using?
- 15-25ml
- Orchidometer
Where in the testis does spermatogenesis occur?
-Semineferous tubules
Sperm develop between the Sertoli cells, what happens to the spermatogonium (1ry germ cells) at the inner edge of the tubule?
- They divide by mitosis to increase in number lots
- Some commit to meiosis to develop into sperm, and enter lumen to rete testis-epidid-release
What do the leydig cells outside the tubule produce?
Testosterone
What type of cell are Sertoli Cells?
Tall, columnar endothelial cells that make up the wall of the sn. tubules
What makes the adluminal compartment in the sn lobule?
-tight junctions between sertoli cells that keep developing sperm in confined compartments
The luminal compartment, interstitial space on outside and adluminal compartment form what immunity structure?
- blood-testis barrier
- so immune system never contacts gametes
What may compromise the blood-testis barrier leading to subfertility?
-Vasectomy as testis leaks into circulation, antibodies against own sperm
What are A vs B spermatogonia?
A divide mitotically to replenish themselves
B are commited to meiosis
Spermatogenesis goes through a new cycle every 16 days, how many days does the process take
apporx 74
What are the 3 stages of spermatogenesis?
- mitotic proliferation of spermatogonia
- meiosis and development of spermatocytes
- spermiogenesis, elongation, loss of cytoplasm
Each cell division of a spermatogonium makes an incomplete spermatid, -how?
-cells remain connected to each other by cytoplasmic bridges forming a syncytium allowing synchronous development
LH binds to Leydig cells which makes testosterone which circulates peripherally bound to what?
ABP - androgen binding protein
What effect does FSH have when binding to Sertoli Cells?
maintains their population and converts androgens to oestrogens via aromatase
Why do anabolic steroids cause testicular atrophy?
-Neg feedback on hypothal so less FSH
What 3 changes occur to make an erection?
- cavernosal arteries dilate so BF increases
- venous return of penis constricts
- higher BP in c.cavernosum
approx 120million sperm in ejaculate of 1.5-6ml. Which part of the ejaculate is the most sperm rich?
-The initial part of the ejaculate
In the vas defs, the small amoun of sperm in the epidymal fluid is mixed with other secretions from where to make “seminal fluid”? 3
- seminal vesicles
- prostate
- bulbourethral gland
What is the bulbourethral glads clear viscous secretion AKA? 2 Functions?
- Pre-ejaculate
- rich in salt
- lubricates urethra for spermatozoa to pass
- neutralises traces of acidic urine
What 5 things are in the seminal vesicle secretions which join at the ejac. duct? This makes up 50-70% of ejaculate. pH = high (protects vs acidic vagina)
- proteins
- enzymes
- fructose
- mucus
- vit C
- prostoglandins
The prostate contributes 30% of ejaculate. What 4 things are in this milky fluid and why?
-proteolytic enzymes
-prostatic acid phosphotase
-prostate specific antigen (PSA)
Liquefaction/more runny
-high zinc conc
What is the acrosome of the mature spermatazoom for?
-bursts near egg and enzymes cut through the outer layer of the egg
What is capacitation (reason a fresh ejaculated sperm cant fertilise an egg)?
-4-18hr time requirement for acrosome properties to change as you dont want it bursting before it reaches egg
What coagulates the ejaculated sperm and why?
- the prostatic and seminal vesicle secretions
- so semen stays together and helps target ejaculate to cervix entrance
Sperm may travel due to uterine/tubal cilia or by chemoattractants (unknown) what 3 changes happen as they undergo capacitation near target?
- become hyperactive
- tail beats more forcefully and more amplitude
- by influx of Ca2+ via Cat Sper channels (alkaline pH change triggers it)
What does the acrosomal membrane on the sperm head contact with for the acrosomal reaction to occur?
-zona-cumulus complex
What does acrosin cound to the inner acrosmal membrane do?
Digests the zona pellucida so sperm can enter
NB: sperm binding is species specific. What does redendency refer to?
Redendency = sperm may bind multiple ZP proteins
What 2 enzymes are released in the acrosome reaction?
- Hyaluronidase
- Acrosin - cuts through ZP
What happens as the sperm nucleus enters the egg (via phagocytosis) in terms of Ca2+?
- huge Ca2+ spike via PLC..
- phospholipase zeta is activated by basal Ca2+ in egg
- PIP2 –> IP3 + DAG so big Ca2+ rise and spike
What does the massive Ca2+ rise wave in the egg caused by the sperm nucleus entering signal/cause?
- signals fertilisation
- causes completion of meiosis II (+ 2nd polar body is extruded, oocyte is truly haploid)
The Ca2+ wave in egg at ferlitsation also causes cortical granules under oocyte membrane to release enzymes into perivitelline space..name 3 enzymes and what is this process called?
-mucopolysaccarides
-proteases (cleave adhesion molecules that sperm bind to)
-peroxidases (cause cross linkage in ZP–> V. hard)
this is the CORTICAL REACTION
What term refers to the fusion of 2 cells/their nuclei in reproduction?
-Syngamy
The 2 sets of haploid chromosomes become surrounded by distinct membranes 4-7hrs post fertilisation, what are these? What happens to them?
- pronuclei, each starts to replicate its DNA preparing for the first mitotic division
- The 2 pronuclei fuse, chromosomes align on the mitotic metaphase spindles
After the 2 pronuclei fuse, what do each daughter cell have? What does the 1 cell zygote become?
- they each recieve the chromosomes with their homologous pairs (23 materal, 23 paternal)
- mitosis is completed. 1 cell zygote –> 2 cell embryo
