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explain whole process of spermatogenesis
Occurs inside seminiferous tubules.
Step 1: Spermatogonia (Stem Cells)
Found at basement membrane (outer edge of tubule).
Diploid (2n = 46 chromosomes).
At puberty → begin dividing by mitosis:
Type A daughter cells → stay at basement membrane to keep germ line going.
Type B daughter cells → move toward lumen → become primary spermatocytes (diploid).
Step 2: Primary Spermatocytes
Undergo Meiosis I → form two secondary spermatocytes.
Each secondary spermatocyte = haploid (n = 23 chromosomes).
Step 3: Secondary Spermatocytes
Quickly enter Meiosis II → produce spermatids.
Each secondary spermatocyte → 2 spermatids.
End result: 4 spermatids from 1 spermatogonium.
Step 4: Spermatids
Haploid round cells located near lumen.
Not yet mature sperm → must undergo spermiogenesis (maturation process).
During spermiogenesis:
Spermatids elongate.
Form tail (flagellum).
Cytoplasm is reduced.
Develop acrosome (cap with enzymes to penetrate egg)
state male accessory sex glands
seminal vesicles
prostate gland
bulbourethral glands
explain ovarian cycle
follicular development phase
- FSH + LH stimulate development of several primordial follicles
structure of Primordial Follicle= primary oocyte surrounded by one layer of squamous follicular cells.
Primordial follicles develop into primary follicles
• Directed by primary oocyte to become primary follicle
• Primary oocyte surrounded by granulosa cells
• Forms zona pellucida (glycoprotein-rich layer) between
granulosa cells and primary oocyte
• Stromal cells begin to form theca folliculi
Primary follicles develop into secondary follicles
• Theca differentiates into theca interna secreting estrogens
and theca externa
• Granulosa cells secrete follicular fluid, forming antrum
• Innermost layer of granulosa cells attaches to zona pellucida
forming corona radiata
Secondary follicles develop into graafian follicle. primary oocyte undergo meiosis I, producing a secondary oocyte and first polar body.
ovulation
Secondary oocyte ejected from the ripened Graafian follicle.
Triggered by LH surge.
luteal phase
Immediately after ovulation:
The ruptured follicle fills with blood → Corpus hemorrhagicum (temporary).
Formation of corpus luteum:
Granulosa cells + theca interna enlarge → form Corpus luteum
Secretes progesterone + estrogen.
Function: prepares the endometrium for implantation and supports pregnancy.
If no pregnancy:
Corpus luteum degenerates in ~10 days.
Becomes a scar called Corpus albicans (white body).
If pregnancy occurs:
Corpus luteum persists for 2–3 months.
Maintained by hCG (human chorionic gonadotropin) from embryo.
After 2–3 months, placenta takes over hormone production.