The Male Reproductive System Flashcards
spermatogenesis
the synthesis of sperm
androgens
male sex hormones
testes
male gonads (aka testicles)
what are the two roles of the testes?
1) spermatogenesis
2) secretion of male sex hormones (androgens)
seminiferous tubules
sites of spermatogenesis, formed by sustentacular cells
sustentacular cells
make up the seminiferous tubules, protect and nurture the developing sperm both physically and chemically
interstitial cells
makes up the tissue between seminiferous tubules, responsible for androgen synthesis
epididymis
a long coiled tube located on the posterior of each testicle into which the seminiferous tubules empty
ductus deferns
tube in which the epididymis from each testicle empties
urethra
the tube inside the penis
inguinal canal
a tunnel that travels along the body wall toward the crest of the hip bone, path followed by the ductus deferens after it leaves the scrotum and before it joins with the urethra
ejaculatory duct
joining of the seminal vesicle with the ductus deferens, joins from both sides of the body to form the urethra
seminal vesicles
pair of glands located on the posterior surface of the bladder, secrete 60% of the total volume of the semen, secretes mostly fructose (nourishment of sperm)
semen
a highly nourishing fluid for sperm, produced by 3 glands (prostate, seminal, bulbourethral) and 2% of sperm from testes
prostate gland
secretes fructose and a coagulant, functions for nourishment and allows semen to coagulate after ejaculation (35% of semen)
boubourethral gands
secretes thick, alkaline mucus an functions to lubricate urethra and neutralize acids in male urethra and in female vagina (3% of semen)
accessory glands
seminal vesicles, prostate gland, bulbourethral gland, testes (each produces a component of sperm)
erectile tissue
specialized tissue in the penis that allows erection (corpus cavernosum-2 and corpus spongiosum)
what are the 3 stages of the male sexual act?
arousal, orgasm, resolution
arousal
dependent upon parasympathetic nervous input, can be divided can erection and lubrication
erection
involves dilation of arteries supplying the erectile tissue which causes swelling, which in turn obstructs venous outflow which causes erectile tissue to become pressurized with blood
lubrication
a function of the parasympathetic system, bulbourethral glands secrete a viscous mucous which serves as a lubricant
orgasm
requires stimulation by the sympathetic nervous system and can be divided into 2 stages: emission and ejaculation
emission
the propulsion of sperm (from the ductus deferens) and semen (from the accessory glands) into the urethra by contractions of the smooth muscle surrounding these organs
ejaculation
semen is propelled out of the urethra by rhythmic contractions of muscles surrounding the base of the penis
resolution
return to a normal, unstimulated state, controlled by the sympathetic nervous system which causes constriction of the erectile arteries and decreases blood flow to the erectile tissue, which allows the veins to carry away the trapped blood
what are the gametes produced by the male?
spermatozoa
what are the gametes produced by the female?
ova
syngamy
fusion of the sperm with the egg in the female genital tract
syngamy results in:
a zygote
maternal inheritance
where both gametes contribute equally to the genome but the egg provides every other part of the zygote (including the mitochondria)
where is the site of spermatogenesis?
the seminiferous tubule with the aid of sustentacular cells in the walls of the seminiferous tubule
germ cells
the cells that give rise to spermatogonia or oogonia
spermatogonium in the outer region of seminiferous tubule become primary spermatocytes that undergo:
their first meiotic division which then become secondary spermatocytes which undergo the second meiotic division to form spermatids which mature into spermatozoa in the inner region of the seminiferous tubules
spermatozoan finish maturing in:
the seminiferous tubule and then the epididymis
spermatozoa are incapable of motility when they first enter the epididymis, when are they capable of moving?
when they enter the ductus deferens, however they remain inactive due to inhibitory substances secreted by the ductus deferens (can be stored here)
head
contains the haploid nucleus and the acrosome
tail
flagellum
neck region
at the base of the tail, contains many mitochondria which uses fructose contained in semen for energy
acrosome
a compartment on the head of the sperm that contains hydrolytic enzymes required for penetration of the ovum’s protective layer
bindin
a protein on the sperm’s surface that attaches to receptors on the zona pellucida surrounding the ovum
testosterone
stimulates division of spermatogonia
luteinizing hormone (LH)
stimulates the interstitial cells to secrete testosterone which inhibits the anterior pituitary and hypothalamus
follicle stimulating hormone (FSH)
stimulates the sustenacular cells to release inhibin
inhibin
hormone secreted by sustenacular cells that inhibit FSH release
what determines the gender of a developing embryo?
its sex chromosomes
Wolffian ducts
develop into male internal genitalia (epididymis, seminal vesicles, ductus deferens)
Mullerian ducts
develop into female internal genitalia (uterine tubes, uterus, vagina), develop by default in the absence of a Y chromosome and MIF
Mullerian inhibiting factor (MIF)
secreted by testes (which develop due to genetic info on Y chromosome) and prevent female internal genitalia from developing
external male genitalia is determined by:
release of testosterone from testes (that enter the systemic circulation)
internal male genitalia is determined by:
release of testosterone from testes locally, assists in Wolffian duct development
testosterone is converted to _______ in target tissues after entering the systemic circulation
dihydrotestosterone
analogous structures
structures arising from Wolffian and Mullerian ducts that have the same function but that arise from different precursors
homologous organs
testes/ovaries, both derived from the gonads and thus have common origin
what is a homologous organ to the penis?
clitoris, functions in erectile tissue and sensation
what is a homologous organ to the bulbourethral glands?
greater vestibular glands, functions in lubrication
what is a homologous organ to the scrotum?
labia majora, functions as external skin folds
androgen
all hormones involved in the development and maintenance of male characteristics
what is the primary androgen produced by the testes?
testosterone
estrogen
all hormones involved in the development and maintenance of female characteristics
what is the primary estrogen produced in the ovaries?
estradiol
secondary sexual characteristics
maturation of the genitalia, male distribution of facial and body hair, deepening of the voice, and increased muscle mass, maintenance requires elevated levels of testosterone (during puberty)
role of estrogens
required to regulate the uterine cycle and for the development and maintenance of female secondary sexual characteristics (maturation of the genitalia, breast development, wider hips, and pubic hair), also causes fusion of the epiphyses
elevated testosterone during puberty also causes (aside from secondary sexual characteristics):
pubertal growth spurt and fusion of the epiphyses
gonadotropin releasing hormone (GnRH)
hormone released from the hypothalamus that stimulates the pituitary to release gonadotropins (FSH and LH), controls sex steroid production
LH effect in males
acts on interstitial cells to stimulate testosterone production
FSH effect in males
stimulate the sustenacular cells to release inhibin (which inhibit pituitary)
LH effect in females
formation of the corpus luteum and progesterone secretion
FSH effect in females
stimulates the granulosa cells to secrete estrogen
which steroids demonstrate feedback inhibition on the hypothalamus (GnRH) and the anterior pituitary (LH and FSH)
inhibin, steroids (testosterone, estrogen)
