St A - Spermatogenesis

Question 1

Name and describe the two major compartments of the testes

Answer 1

1) Seminferous tubules which contain developing germ cells and sertoli cells.
2) Interstitial cells which contain leydig cells and blood and lymph vessels.

Question 2

What separates the seminiferous and interstital spaces?

Answer 2

Blood-testes barrier. It prevents immune reaction to spermatozoa and separates fluids of different composition

Question 3

What are the three stages involved in production of mature spermatozoa?

Answer 3

1) Mitotic proliferation,
2) Meiotic divisions,
3) Cell modelling (spermiogenesis)

Question 4

How long is the spermatogenic cycle?

Answer 4

74 days. It occurs in waves every 16 days

Question 5

Describe the features that are present at the end of differentiation

Answer 5

• Cytoplasmic links are broken,

- Spermatozoa are released into tubular lumen and the sperm is virtually immobile

Question 6

Describe how sperm move if they are initially immobile

Answer 6

• Sertoli cells secrete fluids which flushes spermatozoa from seminiferous tubules through the rete testies to epididymis.
• Epididymis fluid then supresses motility so instead sperm are movement is aided by peristaltic muscle contraction.

Question 7

After ejaculation what must first occur before the sperm can fertilise an oocyte

Answer 7

CAPACITATION.

• The glycoprotein coat which is gained in the epididymis is stripped,
• Head acquires the capacity to initiate the acrosome reaction,
• Hyperactivation (increased flagellar beats)

Question 8

How is infertility in men diagnosed?

Answer 8

Semen analysis comprising of;

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

Question 9

What is Oligozoospermia?

Answer 9

Reduced sperm count (<15million/ml)

Question 10

What is Azoospermia?

Answer 10

Absence of sperm in ejaculate

Question 11

What is asthenozoospermia?

Answer 11

Reduced sperm motility (<40% moving)

Question 12

What is teratozoospermia?

Answer 12

Reduced percentage of sperm with normal morphology

Question 13

What are anti-sperm antibodies?

Answer 13

Abnormal response to sperm

Question 14

What is the role of the hypothalamus and pituitary gland?

Answer 14

Hypothalamus secreted GnRH which binds to gonadotrophic cells on the anterior pituitary. This causes release of lutenizing hormone and follicle stimulating hormone

Question 15

Describe the control of gonadotrophin secretion

Answer 15

High GnRH pulse amplitude and frequency preferentially stimulates LH synthesis and secretion whereas low GnRH pulse frequency stimulates FSH synthesis and secretion

Question 16

What else does the anterior and posterior pituitary glands secrete?

Answer 16

Anterior - Lactotrophs (secretes prolactin) as well as the gonadotrophs.
Posterior - Neurosecretory neurones (arginine vasopressin and oxytocin)

Question 17

What is the function of LH anf FSh

Answer 17

Leydig cell have receptors for LH, and the binding of LH stimulates synthesis and secretion of testosterone so if LH secretion is low then so is testosterone so spermatogenesis halts.
FSH is required for maximum sperm production and it acts on Sertoli cells

Question 18

What occurs when FSH binds to sertoli cells?

Answer 18

• Increased RNA and protein synthesis,
• Increased energy metabolism,
• Increased inhibin secretion,
• Increased cyclic AMP,
• Increased ABP secretion,
• Increased fluid secretion,
• Increased androgen receptors

Question 19

What are the hormones synthesised by the testes?

Answer 19

• Testosterone by leydig,
• Oestrogen by sertoli and leydig,
• Inhibits by sertoli,
• Oxytocin by leydig