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

Male Reproductive System

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

Female Reproductive System

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