Spermatogenesis and Spermiogenesis

Question 1

What are found in between the seminiferous tubules?

Answer 1

Peritubular compartments (leydig cells found here)

Question 2

What are the 2 major compartments of the testes?

Answer 2

• Seminiferous tubules

- Interstitial spaces

Question 3

Why are the seminiferous tubules and interstial spaces seperate?

Answer 3

Create a blood-testis barrier

• Prevents immune reaction to spermatozoa
• Separates fluids of different composition

Question 4

What do the interstitial spaces contain?

Answer 4

• Leydig cells

- Blood and lymph vessels

Question 5

Where is the blood-testis barrier made?

Answer 5

Formed through interactions between tight junctions, zonular junctions and filament bundles between neighbouring sertoli cells, spermatogonia reside on one side of the blood-testis barrier, as development procedes it travels through it

Question 6

What are the 3 stages to produce a mature spermatozoa?

Answer 6

• Mitotic proliferation
• Meiotic divisions
• Cell modeling (spermiogenesis)

Question 7

What are the undifferentiated germ cells called which spermatozoa are derived from?

Answer 7

Primordial germ cells

Question 8

What are the names of all the cells from primordial germ cell to spermatozoa?

Answer 8

• Primordial germ cell
• Spermatogonia
• Primary spermatocyte
• Secondary spermatocyte
• Spermatid
• Spermatozoa

Question 9

What does the primary spermatocyte do?

Answer 9

Enters meiosis 1

Question 10

How long is the spermatogenic cycle?

Answer 10

~ 74 days (from 1st mitotic division to release of spermatozoa)

Question 11

How many days does it usually take to initiate spermatogenesis?

Answer 11

16 days (occurs in waves)

Question 12

How long does it take for the spermatogonium to develop into the primary spermatocyte?

Answer 12

25 days

Question 13

How long does the meiotic division 1 take (primary to secondary spermatocyte)?

Answer 13

9 days

Question 14

How long does it take for the secondary spermatocyte to develop into a spermatozoa?

Answer 14

21 days

Question 15

What is spermiogenesis?

Answer 15

Process that remodells the spermatid into the spermatozoa, during this period where the sperm develops the machinary required for sperm motility

Question 16

How much sperm is made in 1 day roughly?

Answer 16

200 million

Question 17

What structures surround the middle piece?

Answer 17

Sheathes of ring shaped mitochondria

Question 18

What is the acrosome fprmed by?

Answer 18

The golgi

Question 19

What does fluid secreted by sertoli cells do?

Answer 19

Flushes spermatozoa from seminiferous tubules, through the rete testis into the epididymis:

• Capacity for motility by the time they reach the tail of the epididymis
• Motility is suppressed by epididymal fluid
• Instead movement through reproductive tract is aided by perstaltic muscle contractions

Question 20

Why would ejaculated sperm not fertilize an oocyte in vitro immediately?

Answer 20

• Need to undergo capacitation (normally occurs in reproductive tract (2-6h)
• Glycoprotein coat gained in the epidymis is stripped
• Head then aquires the capacity to initiate the acrosome reaction
• Hyperactivation (increased flagellar beats)

Question 21

What percentage of sperm show normal morphology under a microscope?

Answer 21

~ 4 - 14%

Question 22

If normal morphology drops below what level does fertilisation rates obtained with IVF reduced?

Answer 22

4%

Question 23

Infertility in men is primarily diagnosed by semen analysis comprising of what?

Answer 23

• Determination of sperm concentration/total count
• Motility
• Morphology

Question 24

What level of sperm count would make a man sub-fertile?

Answer 24

Below 15 million

Question 25

What is oligozoospermia?

Answer 25

Reduced sperm count (< 15 million/ml)

Question 26

What is azoospermia?

Answer 26

Absence of sperm in ejaculate

Question 27

What is asthenozoospermia?

Answer 27

Reduced sperm motility (<50% moving)

Question 28

What is teratozoospermia?

Answer 28

Reduced percentage of sperm with normal morphology

Question 29

What is antisperm antibodies?

Answer 29

Abnormal immune response to sperm (combinations of these abnormalities afre common)

Question 30

What cells in the testicles does mumps affect?

Answer 30

Sertoli cells

Question 31

How much lower is the temperature of the scrotum in relation to the rest of the body?

Answer 31

2-3 degrees lower

Question 32

What stimulates the anterior pituitary gonadotropins?

Answer 32

Pulsatile secretion of Gonadotropin-releasing hormone (GnRH) from the hypothalamus

Question 33

What are the pituitary gonadotrophins?

Answer 33

- Lutenizing hormone (LH) - Follicle stimulating hormone (FSH) - They control testicular function

Question 34

What cells have LH receptors?

Answer 34

Leydig cells (stimulate synthesis and secretion of testosterone)

Question 35

What happens to testosterone if LH secretion is low?

Answer 35

Testosterone is low (spermatogenesis halts)

Question 36

What does FSH do?

Answer 36

Acts on Sertoli cells and maximises sperm production

Question 37

WHat are the functions of FSH on Sertoli cells?

Answer 37

- Increased RNA and protein synthesis - Increased energy metabolism - Increased inhibin secretion - Increased cAMP - Increased ABP secretion - Increased fluid secretion - Increased androgen receptors - Increased FSH receptors

Question 38

What is more important for sperm production FSH or LH?

Answer 38

LH

Question 39

What can testosterone be converted into?

Answer 39

Dihydrotestosterone or estrogens

Question 40

What are estrognes made by?

Answer 40

Sertoli and Leydig cells

Question 41

What is are inhibins produced by?

Answer 41

Peptide hormone released by Sertoli cells (feedback loop to control hormone levels)

Question 42

WHat is oxytocin (peptide hormone) produced by?

Answer 42

Leydig cells

Question 43

What does oxytocin do?

Answer 43

Contraction of Smooth muscle of the genital tract

Question 44

Where will spermatogenesis fail if testosterone is blocked?

Answer 44

When primary spermatocyetes enter meiotic prophase

Question 45

What will happen if blood testosterone is low?

Answer 45

Fewer stem cells will begin cell division but the whole process will still take 74 days

Question 46

Where does testosterone act on to negatively feedback?

Answer 46

Hypothalamus and anterior pituitary

Question 47

What perecentage of infertile men are actually provided a causal diagnosis?

Answer 47

~ 28%

Question 48

What are the causes of male infertility that can often be diagnosed?

Answer 48

- Gonadotoxic chemo or radio therapy (10%) - Testosterone abuse or other chronic diseases (e.g diabetes) (14%) - Genetic disorders (Klinfelter, Karyotype 47, XXY or microdeletions on the Y chromosome) (4%)

Question 49

What is thought to be one of the causes of congenital hypogonadotrpic hypogonadism?

Answer 49

Mutated genes involved in the migration and function of GnRH neurons or their upstream regulators, can include anosmia