T2 L9: The tests and spermatogenesis

Question 1

What happens in seminiferous tubules?

Answer 1

Spermatogenesis but androgens are needed for this

Question 2

What is testosterone synthesised from?

Answer 2

Acetate and cholesterol

Question 3

Where and how is testosterone converted into dihydrotestosterone?

Answer 3

Converted by 5a-reductase in Sertoli cells

Question 4

What does LH stimulate Leydig cells to do?

Answer 4

To secrete testosterone (androgens)

Question 5

What does FSH stimulate Sertoli cells to do?

Answer 5

Produce sperm

Question 6

How are the seminiferous tubules organised histologically?

Answer 6

There are peripheral myoid cells and then a basement membrane. Sertoli cells and spermatogenic cells are within the tubules

Question 7

What is the significance of the gap and tight junctions complexes between Sertoli cells?

Answer 7

It creates a basal compartment and a separate adluminal compartment

Question 8

What happens in the first stage of spermatogenesis?

Answer 8

Mitosis to produce lots of cells

Germ cells of the prospermatognia are reactivated at puberty to undergo rounds of mitosis in the basal compartments of the tubule. This regenerating population undergoes a series of divisions to form a clone of cells. These will finally divide and form resting primary spermatocytes which inhabit cavities formed in Sertoli cell cytoplasm

Question 9

What is prospermatognia?

Answer 9

Immature testes

Question 10

Why are primary spermatocytes linked by cytoplasmic bridges?

Answer 10

Because although nuclear division is complete, cytoplasmic division isn’t

Question 11

What happens in the seconds stage of spermatogenesis?

Answer 11

Meiosis to generate genetic diversity

The resting primary spermatocytes push through Sertoli cell junctions into adluminal compartments and enter meiotic prophase. The chromosomes swap DNA and then secondary spermatocytes are formed which quickly turn into haploid spermatids

Question 12

What happens in the third stage of spermatogenesis?

Answer 12

Cell modelling to package chromosomes for delivery to the oocyte

• The acrosome forms to penetrate the ooctye
• Cap region forms for sperm-oocyte fusion
• Nucleus with packaged chromosomes forms
• Midpiece with mitochondria forms
• Tail forms for forward propulsion

Question 13

Describe the spermatogenic cycle

Answer 13

Spermatogenesis is complete after 64 days and the process in continuous

Question 14

Is spermatogenesis done in waves?

Answer 14

Yes. Adjacent clones of spermatogenesis are seen

Question 15

What happens to sperm in the epididimus?

Answer 15

Fluid is absorbed and sperm in concentrated

This process is dependent on androgen stimulation

Question 16

How does sperm get into the epididimus?

Answer 16

Spermatozoa wash into the rete through the vasa efferentia into the epididymis

Question 17

Secretions from which structures make up semen?

Answer 17

Secretions from the:

• Seminiferous tubules
• Epididymis

At time of ejaculation:

• Prostate
• Seminal vesicles
• Bulbourethral glands

Question 18

What are the cellular components of semen?

Answer 18

Spermatozoa
Epithelial cells from tract
Spermatogenic cells
Leucocytes

Question 19

What does the endocervix offer sperm?

Answer 19

• It’s receptive to sperm at time of ovulation
• Protection from hostile vagina
• Supplementation of energy requirements
• Sperm selection by differential motility and morphology
• Short-term reservoir within endocervical crypts
• Initiation of the capacitation

Question 20

What is Capacitation?

Answer 20

In the uterus, the sperm will strip off glycoproteins from the sperm surface which accumulates in the epididymis. This causes hyperactivity and makes sperm responsive to signs from the oocyte

Question 21

What does a high volume of ejaculate indicate?

Answer 21

Abstinence or accessory gland inflammation

Question 22

What is the normal volume of ejaculate?

Answer 22

1.5-6ml

Question 23

What is the normal sperm concentration?

Answer 23

15million per mil

Question 24

What does Normozoospermia mean?

Answer 24

Normal values when semen is analysed

Question 25

What does Oligozoospermia mean?

Answer 25

Low concentration of sperm

Question 26

What does Asthenozoospermia mean?

Answer 26

Too little motility of sperm

Question 27

What does Teratozoospermia mean?

Answer 27

Too many abnormalities of sperm

Question 28

What does Oligoasthenoteratozoospermia mean?

Answer 28

When the semen has a low concentration, low motility, and too many abnormalities

Question 29

What does Azoospermia mean?

Answer 29

No spermatozoa

Question 30

What does Aspermia mean?

Answer 30

No ejaculate