Spermatogenesis

Question 1

Testes have two major compartments:

Answer 1

Seminiferous tubules

Interstitial spaces

Question 2

Seminiferous tubules

Answer 2

• ~250 m total length
• Developing germ cells
• Sertoli cells

Question 3

Interstitial spaces

Answer 3

• Leydig cells (synthesize androgens)

* Blood and lymph vessels

Question 4

what separates the two compartments

Answer 4

“Blood-testis barrier”
• Prevents immune reaction to spermatozoa
• Separates fluids of different composition

Question 5

Spermatogenesis

Answer 5

Production of mature spermatozoa from undifferentiated germ

cells (primodial germ cell)

Question 6

what re the three stages of spermatogenesis

Answer 6

1) Mitotic proliferation
2) Meiotic divisions
3) Cell modeling (spermiogenesis)

Question 7

The Spermatogenic cycle is

Answer 7

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

Question 8

when is spermatogenesis initiated

Answer 8

every 16 days and occurs waves

Question 9

Rate of each developmental stages is not uniform:

Answer 9

• Spermatogonium > 1 ̊ spermatocytes = 25 days
• Meiotic division 1 > 2 ̊ spermatocytes = 9 days
• Development > spermatids = 19 days
• Differentiation > spermatozoa = 21 days

Question 10

At end of differentiation: in spermiation

Answer 10

• Cytoplasmic links are broken
• Spermatozoa released into tubule lumen
• Sperm virtually immobile

Question 11

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

Answer 11

Fluid secreted by Sertoli cells

Question 12

what happens when the fluid flushes spermatozoa from seminiferous tubules, through the rete testis into the epididymis:

Answer 12

• 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 peristaltic muscle contractions

Question 13

capacitation:

Answer 13

• Normally occurs in the female reproductive tract (2-6h)

Glycoprotein coat gained in the epididymis is stripped

Question 14

what changes occur in capacitation

Answer 14

• Head acquires the capacity to initiate the acrosome reaction
• Hyperactivation (increased flagellar beats)

Question 15

Infertility in men is primarily diagnosed by semen analysis comprising of:

Answer 15

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

Question 16

Oligozoospermia

Answer 16

• Reduced sperm count (< 15 million/ml)

Question 17

Azoospermia

Answer 17

• Absence of sperm in the ejaculate

Question 18

Asthenozoospermia

Answer 18

• Reduced sperm motility (< 40% moving)

Question 19

Teratozoospermia

Answer 19

• Reduced percentage of sperm with normal morphology

Question 20

Anti-sperm antibodies

Answer 20

• Abnormal immune response to sperm

–

Question 21

where are the hormones released from

Answer 21

Hormones released by the hypothalamus, pituitary and testes are regulated by complex feedforward and feedback loops

Question 22

Hypothalamic secretion of Gonadotrophin-releasing hormone (GnRH) stimulates

Answer 22

the release of gonadotropins from ant. Pit.

Question 23

Pituitary gonadotrophins, luteinizing hormone (LH) and follicle stimulating hormone (FSH) control what

Answer 23

control testicular functions

Question 24

High GnRH pulse amplitude and frequency preferentially stimulates

Answer 24

LH synthesis and secretion whereas low GnRH pulse frequency stimulates FSH synthesis and secretion

Question 25

1) | Anterior pituitary

Answer 25

``` Gonadotrophs – Secrete LH and FSH (glycoproteins) – Most cells secrete one or other, but some secrete both Lactotrophs – Secrete prolactin (protein) ```

Question 26

Posterior pituitary

Answer 26

Neurosecretory neurones | – Secrete arginine vasopressin (AVP) andoxytocin (peptides)

Question 27

Leydig cells

Answer 27

in the testes have receptors for LH | – stimulates synthesis and secretion of testosterone

Question 28

If LH secretion is too low

Answer 28

testosterone is low | – spermatogenesis halts

Question 29

FSH is required for

Answer 29

FSH is required for maximum sperm production – acts on Sertoli cells

Question 30

Testosterone (steroid) by Leydig cells

Answer 30

• In some tissues do not exert direct effects, but are converted to dihydrotestoterone or estrogens

Question 31

2) Estrogens (steroid)

Answer 31

) by Sertoli and Leydig cells

Question 32

3) Inhibins (peptide hormone)

Answer 32

by Sertoli cells | • feedback loop to control hormone levels

Question 33

4) Oxytocin (peptide hormone)

Answer 33

by Leydig cells | • contraction of smooth muscle of the genital tract

Question 34

Role of testosterone

Answer 34

– If production prevented spermatogenesis ceases | – Blocked when primary spermatocytes enter meiotic prophase

Question 35

If blood [testosterone] is low

Answer 35

hen fewer stem cells will begin cell division but the whole process will still take 74 days.