2011 Lab 1 - Spermatogenesis

Human Spermatozoa Development

Spermatogenesis process of spermatagonia mature into spermatazoa (sperm).
Continuously throughout life occurs in the seminiferous tubules in the male gonad- testis (plural testes).
At puberty spermatagonia activate and proliferate (mitosis).
about 48 days from entering meiosis until morphologically mature spermatozoa
about 64 days to complete spermatogenesis, depending reproduction time of spermatogonia
follicle stimulating hormone (FSH) - stimulates the spermatogenic epithelium
luteinizing-hormone (LH) - stimulates testosterone production by Leydig cells

Mature human spermatozoa

60 µm long, actively motile
divided into 3 main regions (head, neck and tail)
head - (flattened, 5 µm long by 3 µm wide) the nucleus and acrosome. Posterior part of nuclear membrane forms the basal plate.
neck - (1 µm) attached to basal plate, transverse oriented centriole, contains nine segmented columns of fibrous material, continue as outer dense fibres in tail.
tail - 3 parts a middle piece, principal piece and end piece
- middle piece - (5 µm long) axonema and dense fibres surrounded by mitochondria
- principal piece - (45 µm long) fibrous sheath interconnected by regularly spaced circumferential hoops
- end piece - (5 µm long) axonema surrounded by small amount of cytoplasm and plasma membrane

Links: Spermatozoa Development | MBoC - Sperm | MBoC - Highly simplified drawing of a cross-section of a seminiferous tubule in a mammalian testis | MBoC - Cytoplasmic bridges in developing sperm cells and their precursors

In humans at puberty, hormonal and morphological changes occur within the gonad and other systems (secondary sex characteristics).
Within the testis the immature Sertoli cells cease to proliferate and differentiate.
Spermatogonium proliferate and spermatogenesis begins.
It takes about 70 days for cells to mature from the diploid spermatogonium to a primary spermatocyte.
This maturation occurs in waves along the seminiferous tubules.

Azoospermia - Non-obstructive azoospermia (NOA) and Obstructive azoospermia (OA)

release of spermatozoa and accessory gland secretions from the male genital tract (3.5 ml)
200-600 million sperm, by volume less than 10 % spermatozoa
Accessory Gland secretions - 60 % seminal vesicle, 30 % prostate and 10 % bulbourethral

Oligospermia - (Low Sperm Count) less than 20 million sperm after 72 hour abstinence from sex
Azoospermia - (Absent Sperm) blockage of duct network
Immotile Cilia Syndrome - lack of sperm motility