Testicular Function and Sperm Physiology

Question 1

Why are testes outside the body?

Answer 1

Because sperm production is best at 35 degrees

Question 2

What two cell types are located in the seminiferous tubules?

Answer 2

1) Spermatogonial stem cells

2) Sertoli cells

Question 3

Where are leydig cells located?

Answer 3

Between seminiferous tubules

Question 4

What is the function of spermatogonial stem cells?

Answer 4

Sperm production (mitosis and meiosis) continuously from puberty to death

Question 5

What is the function of sertoli cells?

Answer 5

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

Question 6

What are sertoli cells interconnected by?

Answer 6

Continuous tight junctions

Question 7

Describe the function of the blood-testicular barrier

Answer 7

• 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

Question 8

Describe the features of spermatogenesis

Answer 8

• Starts at puberty
• Maintains species
• Mitosis followed by meiosis
• 120 million sperm/day (1500/sec)
• Whole cycle takes 72 days

Question 9

Describe adaptive features of sperm

Answer 9

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

Question 10

What is spermiogenesis?

Answer 10

Re-packaging

Question 11

What is the acrosome?

Answer 11

The part of the sperm at the tip of the head

Question 12

What two enzymes does the acrosome contain?

Answer 12

1) Acrosin

2) Hyaluronidase

Question 13

What is the function of leydig cells?

Answer 13

Secrete and produce androgens, mainly testosterone

Question 14

What are the actions of testosterone?

Answer 14

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

Question 15

What hormone levels indicate testicular failure and why?

Answer 15

High FSH and LH → not enough testosterone to negatively feedback to the pituitary

Question 16

What receptors do sertoli and leydig cells have?

Answer 16

FSH and LH

Question 17

Which cell type does FSH mainly act on?

Answer 17

Sertoli

Question 18

Which cell type does LH mainly act on?

Answer 18

Leydig

Question 19

What is the role of PRL in sperm production?

Answer 19

Has a facilitatory action - encourage spermatogenesis

Question 20

What are the stages of sperm transport?

Answer 20

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

Question 21

Describe sperm capacitation

Answer 21

• ‘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

Question 22

What is the acrosome reaction?

Answer 22

• Triggered by contact with oocyte
• Interaction with ZP3 protein on oocyte membrane
• Leads to exposure of hyaluronidase and acrosin enzymes
• Facilitates oocyte penetration

Question 23

Describe oocyte activation

Answer 23

• Release of cortical granules - blocks polyspermic penetration
• Resumption of meiosis
• Formation of the male and female pronuclei (fertilisation)

Question 24

What hormonal factors affect sperm production?

Answer 24

Recreational anabolics abuse (high testosterone) → problem with using testosterone as a male contraceptive

Question 25

What non-hormonal factors affect sperm production?

Answer 25

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

Question 26

What are the different levels in disturbance in regulation of testicular function?

Answer 26

1) Genetic level
2) Hypothalamic level
3) Pituitary level
4) Target tissue level

Question 27

How do factors affect sperm production?

Answer 27

They cause oxidative stress → protein damage, lipid peroxidation, biomembrane damage, DNA damage → sperm damage → infertility

Question 28

What syndromes can affect male fertility?

Answer 28

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

Question 29

What is another cause of male infertility?

Answer 29

Hyperprolactinaemia

Question 30

What is androgen insensitivity syndrome?

Answer 30

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

Question 31

Has there been an increase or decrease over the years in sperm concentration?

Answer 31

Decrease