Spermatogenesis. Spermatozoon .

Spermatogenesis

process of the formation of mature/sperm

Spermatocytopoeisis-

In seminiferous tubules of testes

Dividing of spermatogonua by mitosis(spermatocytogenesis)

Growth and maturation by meiosis

Cytodifferentiation of spermatids to spermatozoa(spermiogenesis)

Spermatogenesis

Origin

from spermatogonium

lasts 74 days

300million sperm released daily

Location: seminiferous tubules in testes

Pecularities

4 mature spermatozoa from one spermatogonia

Maturation of sperm begins at puberty

2 meiotic divisions without interphase

Spermatogonia A

First spermatogonia A-stem cells will develop into spermatogonia b or spermatogonia B must directly divide by mitosis into spermatocytes.

Spermatogonia

next to basal lamina of epithelium

12um in diameter

Type A -stem cells

Type Ad cells-divide rarely

Type Ap cells-divide mitotically

Type B -Progenitor cells

(Mitotic division-16 days)

Primary spermatocyte

18-20 um

23 tetrades (2n DNA)

1st mitotic division 22 days-prolonged prophase

Diploid 46 chromosomes

Secondary spermatocyte

12um

Normal amount of DNA 2n

Haploid-23 chromosones

2nd mitotic division-16 days-prespermatids

Spermatid

7-8um

Haploid

Early spermatids-oval shape

Late spermatids-elongated

Connected by cytoplasmic bridges

1n -reduced amount of DNA

Haploid-23 chromosomes

Spermiogenesis -24 days

Spermiogenesis

Spermatid -> spermatozoa 24 days

3 phases

Golgi phase

-Proacrosomal granules

Acrosomal phase

-acrosomal vesicle

-Acrosomal-hydrolytic enzymes

e.g. acid phosphatase,acrosin(zonalysin)

Maturation phase

Residual bodies shed

Formation of spermatozoa

Spermiation

process by which mature spermatozoa are released from sertoli cells into seminiferous tubules lumen

Spermatozoon

58-67 um

Head-acrosomal cap

Length 5um,3um wide,apex 1um

condensed nucleus

acrosomal cap

Neck

Length 0.3 um, diameter 1um

covered by plasmalemma

basal body-proximal centriole

Tail-flagellum

Middle piece

length5-7um ,diameter 1um

axonemal complex

spiral mitochondria

Principle piece-

Length 45-50 um

longitudinal and circumferential fibrous sheaths

End piece

Length 5-7um

axoneme

surrounding plasmalemma

Factors affecting

Cold temperature-usually 2-4 degrees less than body temperature hence the location of scrotum being outside of body

Healthy lifestyle-Avoidance of alcohol and drugs and nutritional diet which promotes sperm production

Hormonal balance-stable testosterone levels produced by Leydig cells and stable fsh produced by Sertoli cells is required

Good blood circulation- to transport minerals and hormones to testes

Non-spermatogenic cells

Sertoli-support and protect developing spermatozoa

Leydig cells-steroid-secreting cells-testosterone from cholestrol