Spermatogenesis

Front 1

Describe spermatogenesis

Back 1

- produced in seminiferous tubule
- duration: 60-70 days
- 1 spermatogonium -> 64 spermatozoa
(4 mitosis, 1 meiosis)

Front 2

compare gametogenesis between women & men (3)

Back 2

Oogenesis:
- uneven meiotic division: 1 egg, 3 polar bodies
- arrested at 2 stages
- oogonia meiosis before birth -> finite no.

Spermatogenesis
- equal meiotic division: 4 functional spermatozoa
- uninterrupted meiosis
- meiosis at puberty. Some spermatogonia mitosis -> unlimited no. of spermatocytes

Front 3

stages of spermatogenesis (5)

Back 3

1. Mitosis: spermatcytogenesis: spermatogonium (2n)
- proliferating phase

2. Meiosis I: spermatogenesis: 1° spermatocyte (4n)
- production of haploid gamete
3. Meiosis II: spermatogenesis: 2° spermatocyte (2n)

4. Spermiogenesis: spermatid (1n)
- spermatids mature into spermatozoa

5. Spermiation: mature spermatozoa (1n)

Front 4

Describe spermiogenesis' main structural changes (4)

Back 4

1. nuclear condensation
2. cytoplasma shrinkage
3. formation of acrosome
4. development of tail

Front 5

How does the body keep low temp. for spermatogenesis? (4)

Back 5

- testicular temp. 2°C lower
- testes descends at birth
- Musculature of scrotum (dartos, cremaster)
- counter current heat exchange

Front 6

describe sperm maturation in epididymis (3)

Back 6

Transport sperm to epididymis (spermiation) by:
- tubular fluid current, from peritubular myoid cells
- contract testicular capsule

Changes in osmolality & conc. of osmolytes & mol in epididymis

Maturation: gain motility & lose cytoplasm

Front 7

what is capacitation and what happens (3)
what is the acrosome reaction? (3)

Back 7

sperm acquires ability to fertilize ovum in ♀RT
1. Hyperactivation for high motility
2. Acrosome reaction:
- fuse acrosomal & outer sperm membrane
- creation of pores
- release hydrolytic & proteolytic enzymes

Front 8

Sertoli cells (3)

Back 8

- nutrient & environment for spermatogenesis
- blood testis barrier (TJ btwn pre & post meiotic GC)
- Endocrine/paracrine function

Front 9

what hormones do sertoli produce? (4)

Back 9

1. Anti-Mullerian hormone: regress mullerian ducts before puberty
2. Androgen binding protein: high testosterone
3. Plasminogen activator: spermiation
4. Inhibin/activin: regulate testosterone
- FSH (Inhibin↓/Activin↑)
- production of T from Leydig (Inhibin↑/Activin↓)

Front 10

What do peritubular myoid cells do? (2)

Back 10

- modulate function of other testicular cells (Sertoli)
- move spermatozoa to rete testis

Front 11

Leydig cells' function (3)

Back 11

- produce male sex hormone
- Testosterone: circulating prohormone of dihydrosterone (DHT converted from T in tissue)
- under pituitary LH control

Front 12

Function of testosterone (10)

Back 12

With DHT/E2
- sex drive,
- behaviour,
- imprint ♂pattern of gonadotrophins

With DHT:
- intrauterine development of ♂RT
- pubertal dvlpment: beard, penis, seminal vesicle
- gonadotrophin secretion

T:
- Larynx (male voice)
- muscle
- body fat
- skeleton (with E2)

Front 13

describe the steroid pathway:

Back 13

1.cholesterol -> progesterone
2. progesterone -> corticosteroid (cortisol, aldosterone), androgen (T, androstenedione)
3. Estrogen (estradiol, estrone, estriol)

Front 14

Interaction among testicular cells (8)

Back 14

- Germ secrete growth factors for Leydig & Sertoli
- Leydig secrete T to stimulate Peritubular & Sertoli
- Sertoli secrete estradiol, activin to inhibit Leydig
- Sertoli secrete inhibin to stimulate Leydig
- Sertoli: secrete nutrient, growth factor, ABP for Germ
- Peritubular secrete proteins to stimulate Sertoli

- FSH also stimulates Sertoli
- LH stimulates Leydig

Front 15

Male sex act (3)

Back 15

1. Erection (PSNS -> vasodil. -> fill vascular structure)

2. Emission (SNS activated. Contraction of vas deferens & male sex accessory glands. Semen forms in prostatic urethra)

3. Ejaculation (prostatic urethra fills: rhythmical contraction of genital duct, contraction of ischiocavernosus & bulbocavernosus Ms.)
40-80 M sperms in 2-4 mL

emission + ejaculation = orgasm

Front 16

*****typical properties of sperm (6)

Back 16

volume >1.5 mL
pH >7.2
concentration >15 x 10^6 mL
count > 39 x 10^6 ejaculate
motility (<1 hr) > 32% progressive motility
morphology >4%

Front 17

describe seminal plasma (3)

Back 17

(semen = seminal plasma + spermatozoa)
- mainly from ♂sex accessory glands
- alkaline to neutralize acidity of female tract
- most spermatozoa expelled w. prostatic secretion in first 1/3 of ejaculate

Front 18

What do cowper (bulbourethral) glands produce? (4)

Back 18

- 5% ejaculate volume
- clear alkaline mucoid fluid (pre-ejaculate)
- lubricant for semen & tip of penis in intercourse
- neutralizes acidity of urine residue in urethra, and acidity of vagina

Front 19

what do prostate glands produce (4)

Back 19

- 15-30% ejaculate volume
- citric acid (antioxidant)
- zinc: antioxidant, sperm chromatin stabilization
- prostatic acid phosphatase, prostate-specific Ag
(proteolytic cleavage of coagulum-forming proteins semenogelins)

Front 20

seminal vesicles

Back 20

- 50-80% ejaculate volume (last fraction)
- fructose (provide energy)
- ascorbic acid (antioxidant)
- stimulates sperm motility: potassium, bicarbonate, magnesium, prostaglandin
- semenogelin: coagulum formation, inhibits sperm capacitation/motility