Reproductive System: Male Flashcards
The common purpose of the male and female reproductive systems is
To produce offspring
Four tasks of reproduction are:
◦ Form gametes – sperm (♂) & ova (♀)
◦ Bring gametes together via sexual intercourse (♀♂)
◦ Combine genetic information via fertilization to form a zygote (♀)
◦ Support fetal development (gestation) & birth of baby (parturition)(♀)
Ovaries & testes are
The primary sex organs (gonads)
◦ Produce gametes (sex cells: ova & sperm)
◦ Secrete steroid sex hormones (development of secondary sex characteristics: androgens/testosterone and estrogens/progesterone
Accessory reproductive organs are
Ducts, glands
& external genitalia
Gonadotropin releasing hormone (GnRH) from hypothalamus stimulates
release of gonadotropin from
The anterior pituitary
Gonadotropins that stimulate gamete production & sex
hormone secretion
◦ luteinizing hormone (LH)
◦ follicle-stimulating hormone (FSH)
Target tissue effects & negative feedback control of sex hormones is regulated by
Hypothalamus & anterior pituitary
◦ ♂: testosterone;
◦ ♀: estrogen & progesterone
Males produce
4 sperm
Nuclear division in the gonads that forms gametes:
Meiosis: haploid cells introduce genetic variation
Females produce
1 ovum (+ 3 polar bodies; allows conservation of other cell components)
Accessory ducts of male reproductive system are:
epididymis, ductus (vas) deferens, ejaculatory duct, urethra
Accessory glands of male reproductive system are:
seminal vesicles, prostate gland, bulbourethral glands
Testes are housed by the
Scrotum: a sac of skin & superficial fascia that hangs outside the abdominopelvic cavity at root of penis –
◦ Provides an environment 3°C below body temp for sperm production
◦ Responds to temperature changes (shorter & wrinkled when too cold; flaccid & loose when too hot to increase heat loss)
Testes are each divided into
~ 250 lobules containing 1–4 seminiferous tubules
◦ Converge into a tubule that conveys sperm into
the rete testis
In seminiferous tubules: cells that give rise to sperm are
Spermatogenic cells
In seminiferous tubules
cells that support cells that nourish & protect spermatogenic cells are
Sertoli cells (sustentocytes; nurse cells)
◦ Promote sperm production by germ cells
◦ Form blood-testis barrier to protect sperm cells
Seminiferous tubules are surrounded by 3-5 layers of
Smooth muscle-like myoid cells smooth
◦ May help move sperm & fluids out of the testes
◦ Within connective tissue
surrounding the seminiferous tubules
◦ Produce androgens (testosterone)
Interstitial endocrine (Leydig) cells
Absorbs heat from the testicular artery to maintain temperature homeostasis around testes
Pampiniform venous plexus
◦ testicular veins surrounding the testicular artery
◦ Blood sitting outside of main body structures: cool down before it reaches the testes
◦ Exchange in temp as flows into the testes
Contains autonomic nerve fibres, blood vessels, & lymphatics; passes through the inguinal canal to each testis
Spermatic cord
In males luteinizing hormone (LH) stimulates
Testosterone synthesis by interstitial endocrine (Leydig) cells
In males follicle-stimulating hormone (FSH) indirectly stimulates spermatogenesis by
Stimulating Sertoli cells to release androgen-binding
protein to keep testosterone levels high around spermatogenic cells
The final trigger for spermatogenesis is
Testosterone
High blood testosterone inhibits
Hypothalamic release of GnRH & resulting anterior pituitary release of gonadotropins (FSH & LH)
◦ Negative feedback control
The FSH-inhibiting protein released by Sertoli
cells when sperm count is high
Inhibin
Testosterone is a steroid hormone synthesized from
Cholesterol
Testosterone must be converted to
Other hormones in some cells:
◦ Dihydrotestosterone (DHT) in prostate
◦ Estradiol (a form of estrogen) in some neurons
Other function of testosterone:
Targets accessory organs (ducts, glands, & penis) causing them to grow to adult size & function (secondary sex characteristics)
Testosterone level of male infants before birth:
two-thirds that of an adult
◦ for reproductive system development
◦ levels recede after birth & remain low until puberty
Male secondary sex
characteristics induced by testosterone:
◦ Pubic, axillary, & facial hair
◦ Deepening of the voice, thickening of the skin & increase in oil production
◦ Increase in bone/skeletal muscle size & mass
◦ ↑ basal metabolic rate
◦ Coiled tube that provides place for immature sperm
to develop until ejaculation (gain ability to swim)
◦ 1 connected to each testis
◦ 6 m long (longer than a bus)
Epididymis
Immature sperm take how long to pass through the epididymis
2-6 days
Extends as part of the spermatic cord from epididymis, through the inguinal canal, into the pelvic cavity, over the bladder, into the ejaculatory duct, and through the prostate gland to join the urethra
Ductus deferens (vas deferens)
◦ Terminal portion of the testis-associated duct
system
◦ Carries both urine & sperm to exterior
Urethra
Semen is
◦ A milky white, sticky mixture of sperm & accessory gland secretions
◦ The transport medium for sperm; supports & protects
Seminal glands produce
Seminal fluid
◦ 60% of semen
◦ Alkaline: ↑ sperm motility & fertilization ability (coagulating enzyme)
Function of the prostate gland
◦ 25% of semen
◦ Role in sperm activation
Bulbo-urethral glands produce
A thick, clear mucus prior to ejaculation to neutralize acidic urine left over in urethra
3 erectile tissue bodies (connective tissue & smooth muscle riddled with vascular spaces) of the penis:
◦ 1 corpus spongiosum surrounding the urethra
◦ 2 corpora cavernosa making up most of the
penis
An erection is
The engorgement of erectile tissues when blood fills vascular spaces during sexual arousal
During arousal, parasympathetic activity promotes
Release of nitric oxide (vasodilator), causing dilation of penile arterioles
◦ Engorgement of corpora cavernosa compresses
penile veins, ↓ blood flow out of penis to maintain erection
Ejaculation of semen is triggered by the
Sympathetic nervous system
