Sexual Reproduction

Male Reproductive System

GonadsTestis:• Seminiferous tubules: coiled

ducts (~ long), where (male sex cell) made (several 100 million/day)

• Intestitial cells (Leydig cells): between tubules & secrete

• Scrotum: sac that holds testis outside , which provides lower temperature (°C) needed for sperm production

Duct SystemEpididymis:• coiled tubes in sac

(~6m long), where sperm mature over days & stored for weeks

Ductus deferens (Vas Deferens):• tube that sperm from

testes to by peristalsis during ejaculation

• curves around & empties into urethra

Accessory OrgansSeminal Vesicles:• produces thick,

secretion into vas deferens that:1. has pH (basic):

protects sperm from low pH (acidic) in vagina

2. contains : provides energy for sperm

3. contains : causes uterine contractions, which sperm towards egg

• located at of urinary bladder

Prostate Gland:• produces thin, white

secretion into deferens that:

1. has alkaline pH to:i. neutralize pH in

vaginaii. increases pH to activate

sperm ( at pH 7.5)

2. helps sperm • located below urinary bladder

& top of urethra

Cowper’s gland (bulbourethral gland)• produces secretion into

urethra that:1. has alkaline to protect

sperm from urine (acidic) in urethra2. provides during

sexual intercourse

• pea–sized located below prostate

• NOTE: sperm become motile (capable of ) after maturing in epididymis, but not active exposed to secretions from seminal vesicles & prostate gland in vas

Penis

• external structure that delivers sperm into

• erectile tissue: sponge–like with many that fill with blood by constricting veins during

• glans penis: head that contains many endings for sexual excitement

• force of ejaculation provided by of smooth muscle in vas deferens, then skeletal in pelvis

SPERM:

1. head: contains 2. acrosome: enzymes

to help sperm penetrate egg3. midpiece: contains mitochondria

to provide energy for tail4. tail: flagellum for movement

• continuously made in seminiferous of testes through

Spermogensis

spermatogonia (46 chromosomes) →

meiosis & differentiation →

sperm cell (23 chromosomes)

Route of Sperm

• during , 200–500 million sperm ejaculated in 3–4mL of seminal

• sphincter at of bladder before ejaculation

SEMINAL FLUID (SEMEN)• fluid expelled from penis

that secretions from , seminal vesicles, prostate gland, & Cowper’s gland

• sperm in fluid survive only 24–48 h

Functions1. provides medium for of

sperm2. provides for sperm3. activates sperm by alkaline pH4. neutralizes urine in urethra5. neutralizes acidic environment of vagina6. provides which cause uterus

to contract (sperm to egg)7. provides lubrication intercourse

Testosterone: male sex hormone• produced by testes in males & adrenal medulla

in females (in lower conc.)

Functions in males:1. before puberty, development of penis &

testes (sex organs)2. at puberty, stimulates:

A. spermatogenesisB. sex driveC. development of male sex

characteristics,i. facial, , & pubic hairii. products from oil & sweat glands

in skin, which causes acneiii. enlargement of larynx, which

causes voiceiv. increased strengthv. aggressionvi. baldness (if gene present)

Function in females:• body (muscle & bone), sex

drive, & pubic hair growth

• leutenizing hormone (LH): stimulates secretion of

• follicle hormone (FSH): stimulates spermatogenesis– NOTE: testosterone also required for

spermatogenesis

• secretion from pituitary gland stimulated by secretion of gonadotropin hormone (GnRH) from hypothalamus

• secretions from hypothalamus & anterior gland regulated by testosterone in blood plasma through negative – NOTE: LH, FSH, & testosterone secreted into

blood plasma

By the End of this Section You should be able to :

• identify and give functions for each of the following:– testes (seminiferous tubules and interstitial cells)– scrotum– epididymis– ductus (vas) deferens– prostate gland– Cowper’s glands– seminal vesicles– penis– urethra

• describe the path of sperm from the seminiferous tubules to the urethral opening• List the components seminal fluid (as contributed by the Cowper’s glands, prostate gland, and

seminal vesicles), and describe the functions of each component• identify the tail (flagellum), midpiece, head, and acrosome of a mature sperm and state their

functions• describe the functions of testosterone• describe the homeostatic regulation of testosterone levels by the hypothalamus, anterior pituitary,

and testes