Spermatogenesis

Question 1

What is the blood testes barrier?

Answer 1

Tight junctions form between adjacent Sertoli cells which divide the germinal epithelium into basal and luminal components

Function is to limit free exchange of water-soluble molecules and avoids sperm passing into the interstitium to protect them from the immune system

Question 2

How long does spermatogenesis take in humans?

Answer 2

74 days

Question 3

What is the spermatogenic cycle?

Answer 3

The time it takes for reappearance of the same stage within a given section of the tubule - in humans this is 16 days

Question 4

What are the 3 sequential phases of spermatogenesis?

Answer 4

1 - Mitotic proliferation
2 - Meiotic division
3 - Cytodifferentiation

Question 5

Function of the mitotic proliferation stage of spermatogenesis?

Answer 5

Produce large numbers of cells

Question 6

What happens at the mitotic proliferation stage of spermatogenesis?

Answer 6

Spermatogonial stem cells develop into spermatogonia

Spermatogonia undergo mitotic divisions and eventually produce primary spermatocytes

Note that the nuclear division is complete but cytoplasmic division so cytoplasm is still linked together = syncytium

Question 7

What is the syncytium?

Answer 7

During mitosis in spermatogenesis, nuclear division is complete but cytoplasmic division isn’t

This means the cytoplasm is still linked together which is known as the syncytium

Question 8

Function of meiotic division stage of spermatogenesis?

Answer 8

Generates genetic diversity and halves chromosome number

Question 9

What happens in the meiotic division stage of spermatogenesis?

Answer 9

Primary spermatocytes undergo meiosis I to yield 2 secondary spermatocytes with full DNA (2n)

Secondary spermatocytes undergo meiosis II and produce haploid early round spermatids (n)

Question 10

Function of the cytodifferentiation stage of speramtogenesis?

Answer 10

Package chromosomes for effective delivery to the oocyte

Question 11

What happens in the cytodifferentiation phase of spermatogenesis?

Answer 11

Spermiogenesis - spermatids become elongated

As soon as the acrosome forms, the acrosome and nucleus polarise to one side of the cell and a tail grows out of the opposite side

Spermatid nucleus compacts by protamine replacing histones

Spermatozoa are formed - syncytium ruptures and cells are released into the lumen of the tubule

Question 12

What is spermiogenesis?

Answer 12

Cytoplasmic remodelling of spermatids to form spermatozoa

Question 13

What is spermiation?

Answer 13

When the syncytium ruptures and spermatozoa are released into the lumen of the seminiferous tubule

Question 14

How is the nucleus compacted in spermatogenesis?

Answer 14

Protamines replace histones

Question 15

Where do spermatogonial stem cells arise from?

Answer 15

gonocytes from primordial germ cells during foetal development

Question 16

What cells support spermatogenesis?

Answer 16

Sertoli cells

Question 17

Name the male germ cells from PGCs to spermatozoa?

Answer 17

Primordial germ cells
Gonocytes
Spermatogonial stem cells
Spermatogonia
Primary spermatocytes
Secondary spermatocytes
Spermatids
Spermatozoa

Question 18

LH stimulates what cells in males? What do the cells produce?

Answer 18

Leydig cells which produce testosterone, oestrogens and oxytocin

Question 19

FSH stimulates what cells in males? What do the cells produce?

Answer 19

Sertoli cells which produce AMH, androgen binding protein, inhibin B

Question 20

What is azoospermia?

Answer 20

Nearly absent or absent sperm in the ejaculate

Question 21

Types of azoospermia?

Answer 21

Non-obstructive or obstructive

Question 22

What is non-ibstructive azoospermia?

Answer 22

Problem is with spermatogenesis, not the ducts

Question 23

Causes of non-obstructive azoospermia?

Answer 23

Primary hypogonadism i.e. defect with the testes e.g. genetics, infections, iatrogenic

Secondary hypogonadism i.e. hormonal imbalance in normal testes e.g. Kallmann syndrome, pituitary tumours

Question 24

Treatment options for non-obstructive azoospermia?

Answer 24

Gonadotrophin therapy
Testicular sperm extraction for IVF and ICSI

Question 25

What is obstructive azoospermia?

Answer 25

Occlusion of testicular and genital ductal system causing azoospermia

Question 26

Causes of obstructive azoospermia?

Answer 26

infection, congenital abnormalities, iatrogenic injury, vasectomy

Question 27

Treatment options for obstructive azoospermia?

Answer 27

Surgical reconstruction e.g. vasectomy reversal
Testicular sperm extraction for IVF or ICSI

Question 28

Normal semen parameters?

Answer 28

Volume = 1.5ml of ejaculate
Concentration = >15 million sperms per ml
Progressive motility = 32%
Morphology - 4%

Question 29

What things can have adverse effects on human spermatogenesis?

Answer 29

heat
alcohol
smoking
chemotherapy or radiotherapy