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.
Semen
formed from seminal fluid and sperm. Called ejaculate when released during intercourse. Ejaculate contains 200 to 500 million spermatozoa and transit time from seminiferous tubules to ejaculate is about 2 weeks.
Rete testis
meshwork of interconnected channels in mediastinum testis. Receive sperm from seminiferous tubules. It is lined by simple cuboidal epithelium with short microvilli covering luminal surface. Merge to form efferent ductules.
efferent ductules
connect rete testis to epididymis. lined with ciliated columnar to propel sperm towards epididymis and nonciliated columnar to absorb excess fluid secreted by seminiferous tubules.
epididymis
comma-shaped structure. Composed of internal duct and external covering of CT. Has a head, body, and tail. It contains a 4-5 meter long duct of the epididymis. Stores sperm until mature. If it is ejected too early it is not motile and if too late, it degenerates and is reabsorbed.
ductus (vas) deferens
sperm enters here after leaving epididymis. This thick-walled tube is located within spermatic cord, extending through inguinal canal. Separates from other cord components in pelvis. Enlarges and eventually forms ampulla that unites with proximal seminal vesicle to form ejaculatory duct.
ductus wall
inner mucosa lined by pseudostratified ciliated columnar. The middle muscularis has 3 layers of smooth muscle: inner longitudinal, middle circular, and outer longitudinal that is necessary for moving sperm through vas deferens. sperm is not motile until ejaculation from penis. It also has an outer adventitia.
ejaculatory duct
each duct is between 1-2 cm long. pseudostratified ciliated columnar epithelium that conducts sperm and a component of seminal fluid towards urethra.
urethra
transports semen from ejaculatory ducts to outside of body. has 3 components prostatic urethra, membranous, and spongy urethra.
male sexual response
excitement phase: erectile bodies of penis composed of venous space that fills and becomes rigid. Parasympathetic innervation causes local release of nitric oxide responsible for increased blood flow and erection. increases hr, bp, and resp. rate.
Orgasm: intense pleasure, tension release, expulsion of semen. ductus deferens moves sperm towards urethra and gland secretions combine to form semen. internal urethral sphincter contracts to prevent urine entry into urethra
Ejaculation: end of orgasm where semen is expelled from contraction of muscles in urethra due to sympathetic innervation.
Resolution: sympathetic division stimulated to contract central artery of penis to help expel engorged blood. Followed by refractory period (minutes to hours)
Male climacteric
decrease in testosterone levels in 50s. Due to decreased number of interstitial cells and declines more gradually than women’s hormones drop. Most men have few symptoms but can have hot flashes, mood swings, and decreased sex drive.
Prostate enlargement
experienced by most men with age; can interfere with sexual and urinary functions
Erectile dysfunction
inability to achieve or maintain erection associated with aging and other risk factors.
