Human Reproductive Systems
Functions of the Reproductive System
• Produces and nurtures sex cells
• Transports sex cells to site of fertilization
• Secretes hormones vital to the development and maintenance of sexual characteristics
• Regulates reproductive physiology
Testes - Location
• Primary sex organs in which sperm cells and male sex hormones are formed
• Located within scrotum
Testes - Structure• Surrounded by white
fibrous capsule that divides testis into about 250 lobules
• Each lobule contains seminiferous tubules
• Interstitial cells secrete sex hormones
• Tubules unite to form epididymis vas deferens
Spermatogenesis
M atu re S p erm C e lls
S p erm atid s
S econ d ary S p erm atocytes
P rim ary S p erm atocytes
S p erm atog on ia • Process of producing sperm cells
• Produced throughout reproductive life
• Collect in seminiferous tubules and pass to epididymis to mature
Sperm Structure
• Flattened head, cylindrical midpiece, and elongated flagellum
• Head contains nucleus (23 chromosomes)
• Acrosome• Many mitochondria in
midpiece
Epididymis
• Tightly coiled, threadlike tube
• Connects to ducts of testis
• Becomes the vas deferens
• Sperm cells are initially nonmotile here
Vas Deferens• Aka ductus deferens• Muscular tube that
passes from the testis into the abdominal cavity
• Ends behind the urinary bladder
• Unites with duct of seminal vesicle to form ejaculatory duct– Ejaculatory duct passes
through prostate– Empties into urethra
Seminal Vesicles• Convoluted sac-like
structures• Attach to the vas
deferens near base of urinary bladder
• Secrete slightly alkaline fluid:– Helps regulate pH
– Contains fructose to supply sperm with energy
– Contains prostaglandins that trigger contractions within female
Bulbourethral Glands
• Aka Cowper’s glands• Pair located posterior
to the prostate• Produces mucus-like
fluid in response to sexual stimulation
• Fluid lubricates end of penis
Semen
• Fluid conveyed by the male urethra to the outside of the body during ejaculation
• Consists of sperm and secretions of the seminal vesicles, prostate, and bulbourethral glands
• pH = 7.5• Volume varies – 2-6 ml• Average sperm count = 120 million / ml• Sperm are nonmotile until they mix with glandular
secretions
Scrotum• Pouch of skin that hangs from lower abdominal
region behind the penis• Medial septum• Holds the testes
Penis
• Conveys urine and semen through the urethra to the outside
• Erection• Shaft contains 3
columns of erectile tissue:– Corpora cavernosa
– Corpus spogiosum
Penis Structure
• Enlarges at distal end to form glans penis
• Prepuce• Emission• Ejaculation• Circumcision
Male Sex Hormones
• Most changes during puberty are controlled by the hypothalamus (begins around age 10)
• Luteinizing hormone (LH) – promotes development of testicular cells that secrete male sex hormones
• Follicle-stimulating hormone (FSH) – stimulates cells of seminiferous tubules to respond to testosterone spermatogenesis
• Androgens – testosterone; stimulates enlargement of testes and development of secondary sexual characteristics
Male Secondary Sexual Characteristics
• Growth of body hair on face, chest, axillary, and pubic regions
• Larynx enlarges and vocal cords thicken lower pitch to voice
• Skin thickens• Muscular growth increases, shoulders broaden,
waist narrows• Bones thicken and strengthen• Increased rate of cellular metabolism and RBC
production
Functions of Female Reproductive System
• Production and maintenance of ova
• Transportation of ova to site of fertilization
• Provision of favorable environment for developing offspring
• Movement of developed offspring to the outside
• Production of female sex hormones
Ovaries - Structure
• Solid, ovoid structures• Lie in shallow
depressions in lateral wall of pelvic cavity
• Inner medulla• Outer cortex
Oogenesis
Z yg ote(if oocyte is fe rt ilized )
P o la r B od ies
S econ d ary O ocytes P o la r B od ies
P rim ary O ocytes
P rim ord ia l F o llic les
• Primordial follicles formed during prenatal development
• Each follicle consists of single primary oocyte
• Meiosis begins in primary oocyte and halts until puberty
• At puberty, meiosis continues in some primary oocytes
• Polar bodies
Follicle Maturation
• During maturation of primordial follicle, surrounding follicular cells proliferate, organize into layers, and form fluid-filled cavity around the oocyte.
• Follicle cavity presses oocyte to one side, forming “blister” on the surface of the ovary.
• 20 primary oocytes may begin maturing, but usually one outgrows the others.
Ovulation
• Release of the secondary oocyte and first polar body from the follicle
• Hormones cause mature follicle to swell rapidly and its walls weaken
• After ovulation, secondary oocyte and 1-2 layers of follicular cells surrounding it are propelled into the uterine tube.
• If not fertilized, the oocyte degenerates.
Uterine Tubes
• Aka fallopian tubes or oviducts
• Open near the ovary and pass medially to the uterus
• Infundibulum• Fimbriae
Uterus - Functions
• Hollow, muscular organ shaped like an inverted pear
• Receives the embryo from the uterine tube and sustains its development
• Muscles contract during intercourse to help transport sperm
• Size changes greatly during pregnancy
Uterus - Structure• Located in anterior
portion of pelvic cavity, above the vagina, and over the bladder
• Body – upper 2/3• Cervix – bottom 1/3;
surrounds cervical orifice
Layers of Uterine Wall
• Endometrium• Myometrium• Perimetrium• Endometrium and
myometrium change extensively during pregnancy
• Endometriosis
Vagina• Extends from the uterus
to the outside of the body• Conveys uterine
secretions• Receives the penis during
intercourse• Provides a channel for
offspring during birth• Extends up and back into
pelvic cavity, posterior to bladder and urethra, anterior to rectum
• Hymen
Vulva - Structure• External accessory structure of the female
reproductive system• Surrounds openings of urethra and vagina• Labia majora• Mons pubis• Labia minora• Clitoris• Vestibule• Vestibular glands
Female Sex Hormones• Estrogen – produced by the ovaries to stimulate
enlargement of accessory organs and external reproductive structures, develops and maintains secondary sexual characteristics:– Development of breasts and ducts of mammary glands– Increased deposition of adipose in breasts, thighs, and buttocks– Increased skin vascularity
• Progesterone – produced by ovaries to promote uterine changes during reproductive cycle, affects mammary glands, and helps regulate release of FSH and LH
• Androgens – increase hair in pubic and axillary regions; formed by adrenal cortex in females
Female Reproductive Cycle
• Aka menstrual cycle• Consists of regular, recurring changes in the
uterine lining• Culminates in menses, or menstrual
bleeding• Begins around age 13 and continues until
middle age• Menopause
Mammary Glands
• Accessory organs specialized to secrete milk following pregnancy
• Modified sweat glands• Found in breasts over
the pectoralis major muscles