Ch. 28 - Male reproductive system Flashcards
primary reproductive organs male
testes
accessory reproductive organs male
ducts and tubules leading from testes to penis, male accessory glands, penis
Testes
relatively small organs housed within scrotum that produce sperm and androgens. Covered anteriorly and laterally by a serous membrane called tunica vaginalis.
tunica vaginalis
a serous membrane that covers the testes. It is derived from abdominal peritoneum and has outer parietal layer and inner visceral layer that are separated by each other by a cavity filled with serous fluid
Tunica albuginea
thick fibrous capsule covering testis; deep to visceral layer of tunica vaginalis
mediastinum testis
thickening of tunica albuginea projecting into interior testis. Blood vessels, lymph vessels, and nerves enter or leave through here.
Septa
internal projections of tunica albuginea, subdivide internal space into 250 lobules.
seminiferous tubules
convoluted and elongated tubes that contain nondividing support cells called sustentacular cells. There are up to 4 tubules in each lobule. The cells nourish developing sperm, release inhibin when sperm count is high, and inhibits FSH secretion and regulates sperm production. Tubules also contain dividing germ cells continuously producing sperm
blood-testis barrier
protects developing sperm from material in blood, including leukocytes. Formed from tight junctions between sustentacular cells.
interstitial spaces
spaces surrounding seminiferous tubules
interstitial cells
reside in interstitial spaces. Stimulated to produce androgens by LH; particularly testosterone. Majority of testosterone is released from interstitial cells; small amounts through adrenal cortex.
Hormonal regulation of Spermatogenesis
- Hypothalamus secretes GnRH which stimulates pituitary to secrete FSH and LH.
- FSH and LH stimulate spermatogenesis and androgen production. LH stimulates interstitial cells while FSH stimulates sustentacular cells
- Increased testosterone facilitates spermatogenesis, inhibits GnRH and pit. sensitivity to GnRH and negative feedback effect
- Sustentacular cells release inhibin to inhibit FSH due to rising sperm.
- Testosterone stimulates libido and secondary sex characteristics
role of FSH in spermatogenesis
stimulates sustentacular cells to secrete androgen-binding protein. This binds to testosterone and ensures high levels in testes.
role of LH in spermatogenesis
stimulates interstitial cells to secrete testosterone.
spermatogenesis
process of sperm development; occurs in seminiferous tubule. Begins during puberty with significant levels of FSH and LH
Spermatogonia
primordial germ cells from which all sperm develop. They are diploid cells near base of seminiferous tubule; surrounded by cytoplasm of sustentacular cell. Divide by mitosis into new spermatogonium and primary spermatocyte.
Primary spermatocyte
diploid cells that undergo meiosis
Secondary spermatocytes
two cells produced by primary spermatocyte from meiosis I. Haploid cells, 23 chromosomes only. Relatively closer to seminiferous tubule lumen.
Spermatid
formed when secondary spermatocytes complete meiosis II. Haploid cell near seminiferous tubule lumen with circular appearance.
spermiogenesis
final stage of spermatogenesis where spermatid becomes mature spermatozoa (sperm). excess cytoplasm shed and nucleus elongates. Acrosome cap forms over nucleus that contain digestive enzymes to help penetrate secondary oocyte. Tail forms from organized microtubules in cell and attach to midpiece region containing mitochondria and centriole.
acrosome cap
forms over sperm nucleus and contains digestive enzymes to help penetrate secondary oocyte.
tail
forms from microtubules in sperm
midpiece
contains mitochondria and centriole. mitochondria produces energy to move tail
female vs. male gametogenesis
single viable secondary oocyte produced in females while 4 produced in males. female oocytes arrested in meiosis prior to birth while male spermatogonia starts spermatogenesis at puberty. Females can only reproduce until menopause while men can forever.