Testicular Function and Sperm Physiology Flashcards
Why are testes outside the body?
Because sperm production is best at 35 degrees
What two cell types are located in the seminiferous tubules?
1) Spermatogonial stem cells
2) Sertoli cells
Where are leydig cells located?
Between seminiferous tubules
What is the function of spermatogonial stem cells?
Sperm production (mitosis and meiosis) continuously from puberty to death
What is the function of sertoli cells?
1) Provide structural support
2) Create 2 compartments - adluminal and basal
3) Provides nutrients for mature sperm
4) Eliminate degenerate germ cells (no apoptosis)
5) Secretes inhibin, ABP, AMH and growth factors
6) Large molecules cannot pass between the basal and adluminal compartment (BTB) - protection
7) Keep integrity of spermatogenesis
What are sertoli cells interconnected by?
Continuous tight junctions
Describe the function of the blood-testicular barrier
- New antigens are produced on mature sperm (outside body) and the body could attack them via anti-sperm antibodies and therefore affect fertility
- The protein barrier between these cells in the testes and the blood (immune system) prevents this
Describe the features of spermatogenesis
- Starts at puberty
- Maintains species
- Mitosis followed by meiosis
- 120 million sperm/day (1500/sec)
- Whole cycle takes 72 days
Describe adaptive features of sperm
1) Nucleus in the head - sperm is carrier of DNA
2) Lysosomal enzymes concentrated at the head of sperm to access the gg
3) Flagella to move away from immune cells in women
What is spermiogenesis?
Re-packaging
What is the acrosome?
The part of the sperm at the tip of the head
What two enzymes does the acrosome contain?
1) Acrosin
2) Hyaluronidase
What is the function of leydig cells?
Secrete and produce androgens, mainly testosterone
What are the actions of testosterone?
1) Male hormone - anabolic (bone and muscle mass)
2) Primary and secondary sexual characteristics
3) Libido and sexual behaviour
4) Stimulates sertoli cells and spermatogenesis
What hormone levels indicate testicular failure and why?
High FSH and LH → not enough testosterone to negatively feedback to the pituitary
What receptors do sertoli and leydig cells have?
FSH and LH
Which cell type does FSH mainly act on?
Sertoli
Which cell type does LH mainly act on?
Leydig
What is the role of PRL in sperm production?
Has a facilitatory action - encourage spermatogenesis
What are the stages of sperm transport?
1) Ejaculation → deposition of sperm in vagina (acidic)
2) Cervix → mucous barrier and crypts act as sperm reservoirs - motility is important
3) Uterus and tubules → mild contraction from uterine and tubule wall to propel the sperm towards the egg
4) Ampullary (outer ⅓) portion of the tube → fertilisation
Describe sperm capacitation
- ‘Switching on’ of sperm
- Takes about 2-4 hours after ejaculation
- Cholesterol loss and calcium influx - more ATP for each egg in outer third of fallopian tube
What is the acrosome reaction?
- Triggered by contact with oocyte
- Interaction with ZP3 protein on oocyte membrane
- Leads to exposure of hyaluronidase and acrosin enzymes
- Facilitates oocyte penetration
Describe oocyte activation
- Release of cortical granules - blocks polyspermic penetration
- Resumption of meiosis
- Formation of the male and female pronuclei (fertilisation)
What hormonal factors affect sperm production?
Recreational anabolics abuse (high testosterone) → problem with using testosterone as a male contraceptive
What non-hormonal factors affect sperm production?
1) Damage to BTB incl. vasectomy → high number of anti-sperm antibodies and increase in intratesticular pressure
2) Environment → heat exposure (34 degrees), radiation, air pollution, food chain pollution (lots of oestrogen in urine of women on pill and animals fed oestrogen to make them bigger), stress, reduced sexual activity
3) Smoking
4) Cancer
What are the different levels in disturbance in regulation of testicular function?
1) Genetic level
2) Hypothalamic level
3) Pituitary level
4) Target tissue level
How do factors affect sperm production?
They cause oxidative stress → protein damage, lipid peroxidation, biomembrane damage, DNA damage → sperm damage → infertility
What syndromes can affect male fertility?
1) Klinefelter syndrome → 47XXY
2) Kallman syndrome → lack of proper anterior pituitary formation and nose/smell formation and look young
→ treatment of FSH and LH → spermatogenesis
What is another cause of male infertility?
Hyperprolactinaemia
What is androgen insensitivity syndrome?
Tissues aren’y responding to testosterone (no or v little testosterone receptors → complete/incomplete)
- Intra-abdominal testicles so high temperature → 25% cancer risk so often get them removed (default female)
- 46XY → female features just amenorrhea bc no uterus or ovaries
Has there been an increase or decrease over the years in sperm concentration?
Decrease
