Reproductive Systems

Male Reproductive System• Testes• Epididymides• Ductus Deferentia• Seminal Vesicles• Prostate Gland• Bulbourethral Glands• Scrotum• Penis

Female Reproductive System• Ovaries• Uterine Tubes• Uterus• Vagina• Labia Majora• Labia Minora• Clitoris• Vestibule• Mammary Glands

Male Reproductive System

Male Reproductive Organs• Testes

– Primary sex organs– Sperm cells & male sex hormones formed here– 2 testes w/in cavity of scrotum– Tough, white, fibrous capsule encloses each testis– Connective tissue thickens & extends into testis forming 250 lobules

– Each lobule contains 1-4 seminiferous tubules– Tubules unite to form complex network of channels that give rise to ducts

that join tube called epididymis– Specialized stratified epithelium called spermatogenic cells line the

seminiferous tubules & give rise to sperm cells– Interstitial cells lie in space between seminiferous tubules &

produce/secrete male sex hormones

Fig. 19.02a

Structure of the testis

Sperm Cell Anatomy• Tiny tad-pole shaped cell• 0.06 millimeters long• Oval Head

– Nucleus w/ compacted chromatin consisting of 23 chromosomes

– Acrosome contains enzymes to help penetrate egg cell

• Midpiece– Many mitochondria organized in

a spiral

• Tail– Flagellum– Allows for movement to propel

sperm through fluid

Spermatogenesis• Occurs continually starting at puberty

• During embryonic development, hormones stimulate spermatogonia (undifferentiated spermatogenic cells) to undergo mitosis

• Each cell division gives rise to 2 new cells– Type A maintains supply of undifferentiated cells– Type B differentiates becoming a primary spermatocyte

• Spermatocytes reproduce by cell division called meiosis

• Meiosis contains 2 successive divisions: 1st & 2nd meiotic divisions

Spermatogenesis• Before Meiosis I, each homologous chromosome is replicated• Meiosis I separates homologous chromosome pairs• Haploid: each cell undergoing meiotic division begins w/ 1 member

of each homologous pair– Haploid cell has 1 set of chromosomes

Spermatogenesis• Meiosis II separates chromatids,

producing cells whose chromosomes are no longer in replicated form

• After meiosis II, each chromatid is independent chromosome

• For each primary spermatocyte undergoing meiosis, 4 sperm cells w/ 23 chromosomes result

• Each primary spermatocyte divides to form 2 secondary spermatocytes; each of these divide to form 2 spermatids (mature into sperm cells)

Male Internal Reproductive Organs• Specialized to nurture & transport sperm

• Epididymides (2)– Tightly coiled, threadlike tubes 6 meters long– Each connected to ducts w/in a testis– Emerges from top of testis, descends along posterior surface, & comes upward to

become ductus deferens• Ductus Deferentia (2)

– Muscular tubes 45 cm long– Pass upward in lower abdominal wall, enter pelvic cavity, & end behind urinary

bladder– Unite w/ duct of seminal vesicle to form ejaculatory duct, which passes through

prostate gland & empties into urethra• Seminal Vesicles (2)

– Convoluted, saclike structures 5 cm long– Attach to ductus deferens near base of urinary bladder– Lining secretes alkaline fluid to regulate pH of tubular contents– Secretes fructose – provide energy to sperm– Secretes prostaglandins – stimulate muscular contractions w/in female

reproductive organs

Male Internal Reproductive Organs• Specialized to nurture & transport sperm

• Prostate Gland– Chestnut shaped structure that surrounds part of urethra, inferior to bladder– Secretes thin, milky fluid w/ alkaline pH– Secretion neutralizes fluid containing sperm cells– Enhances motility of sperm cells & helps neutralize acidic secretions of vagina

• Bulbourethral Glands (2)– Inferior to prostate gland– Secrete mucus-like fluid in response to sexual stimulation– Fluid lubricates end of penis in preparation for sexual intercourse

• Semen– Fluid secreted by male urethra during ejaculation– Consists of sperm & secretions of seminal vesicles, prostate gland, &

bulbourethral glands– Slightly alkaline & includes prostaglandins & nutrients

Male External Reproductive Organs• Scrotum

– Pouch of skin & subcutaneous tissue hanging from lower abdominal region posterior to penis

– Contains 2 chambers each of which hold a testis– Chambers contain serous membrane to cover testis & allow for

smooth movement– Protects & helps regulate temperature of testes

• Penis– Cylindrical organ that conveys urine & semen through urethra– Shaft of penis has 3 columns of erectile tissue– Urethra extends through glans penis which is cone shaped sensitive

end of penis

Hypothalamic & Pituitary Hormones• Hypothalamus secretes gonadotropin-releasing hormone (GnRH)

• Stimulates anterior pituitary gland to release gonadotropins, luteinizing hormone, & follicle-stimulating hormone

• Luteinizing Hormone– Promotes development of interstitial cells of testes– In turn, testes secrete male sex hormones

• Follicle-Stimulating Hormone– Stimulates seminiferous tubules to respond to effects of testosterone– FSH & testosterone stimulate spermatogenic cells to undergo

spermatogenesis– Seminiferous cells also secrete hormone inhibin, which inhibits anterior

pituitary gland by negative feedback

Male Sex Hormones = Androgens• Testosterone

– Most important androgen

• Actions:– Increased growth of body hair– Enlargement of larynx & thickening of vocal folds– Thickening of skin– Increased muscular growth, broadening of shoulders, & narrowing of

waist– Thickening & strengthening of bones– Increases rate of cellular metabolism & RBC production– Stimulates sexual activity by affecting certain parts of brain

Regulation of Testosterone• Hypothalamus regulates

through negative feedback• Increasing Concentration

– Inhibits hypothalamus– stimulation of anterior

pituitary gland decreases– As secretion of LH falls,

testosterone release from cells decreases

• Decreasing Concentration– Hypothalamus stimulates

anterior pituitary gland to release LH

– Secretion causes interstitial cells to release testosterone

Female Reproductive System

Female Reproductive Organs• Ovaries (2)

– Solid, ovoid structures– Lie in shallow depressions in lateral wall of pelvic cavity– Divided into 2 regions – inner medulla & outer cortex– Ovarian medulla composed of loose connective tissue w/ many blood vessels,

lymphatic vessels, & nerve fibers– Ovarian cortex consist of compact tissue & granular appearance due to tiny

masses of cells called ovarian follicles– Layer of cuboidal epithelium covers ovary’s free surface– Beneath layer of epithelium is layer of dense connective tissue

Primordial Follicles• During prenatal development, small group of cells of ovarian

cortex form several millions primordial follicles

• Each follicle = single, large cell called primary oocyte

• Each primary oocyte surrounded by epithelial cells called follicular cells

• Once primordial follicles appear, no new ones form

• Number of ooyctes in ovary steadily decline over time

Oogenesis• Beginning at puberty, some primary oocytes stimulated to continue

meiosis

• When primary oocyte divides, cytoplasm distributed unequally

• One of resulting cells, secondary oocyte, is large

• Other resulting cell, first polar body, is small

• Secondary oocyte represents future egg cell– If fertilized by sperm, divides unequally to produce a 2nd polar body & a

large fertilized egg cell called a zygote

• Polar bodies degenerate

Oogenesis

Follicle Maturation• w/ each reproductive cycle, some primordial follicles mature into primary

follicles

• During maturation, primary oocyte enlarges & surrounding follicular cells proliferate by mitosis

• Follicular cells organize into layers & a cavity appears in the cellular mass

• Clear follicular fluid fills cavity & bathes primary oocyte

• Enlarging fluid filled cavity presses primary oocyte to one side

• Mature follicle buldges outward on ovary surface

• Secondary oocyte w/in mature follicle is large, spherical cell, surrounded by glycoprotein called zona pellucida & attached to mantle of follicular cells

Follicle Maturation

Ovulation• As follicle matures, primary oocyte undergoes oogenesis giving rise to

secondary oocyte & 1st polar body

• Ovulation: releases secondary oocyte & 1st polar body w/ 1 or 2 surrounding layers of follicular cells from mature follicle

• Release of LH triggers ovulation

• Eventually mature follicle’s wall ruptures & follicular fluid & secondary oocyte ooze from ovary surface

• After ovulation, secondary oocyte & surrounding follicular cells propelled to uterine tube

• If not fertilized, oocyte degenerates

Female Internal Reproductive Organs• Uterine Tubes aka Fallopian Tubes (2)

– 10 cm long passing medially to uterus, penetrates its wall & opens into uterine cavity

– Near each ovary, expands to form infundibulum, which partially encircles ovary– Simple columnar epithelial cells line uterine tubes– Epithelium secrete mucus which cilia move towards uterus– Ciliary action & peristaltic contractions help transport secondary oocyte down

uterine tube– Fertilization occurs in uterine tube

• Uterus– Receives embryo that develops from fertilized egg in uterine tube– Hollow, muscular organ located medially in anterior part of pelvic cavity,

superior to vagina– Uterine tubes enter at top of uterus– Lower third of uterus, cervix, extends downward into upper part of vagina– Cervix surrounds opening through which uterus opens to vagina

Female Internal Reproductive Organs• Uterus (Cont.)

– Thick wall w/ 3 layers– Endometrium (inner mucosal layer) – covered w/ columnar epithelium &

contains tubular glands– Myometrium (thick, middle layer) – consist of bundles of smooth muscle fibers– Perimetrium (outer serosal layer) – covers body of uterus & part of cervix

• Vagina– fibromuscular tube extending from uterus to outside of body– Conveys uterine secretions, receives penis during sexual intercourse, &

provides open channel for birth– Wall has 3 layers

• Inner mucosal layer of stratified squamous epithelium• Middle muscular layer consisting of smooth muscle• Outer fibrous layer consists of dense connective tissue interlaced w/ elastic fibers

Female External Reproductive Organs• Labia Majora

– Rounded folds of adipose tissue & thin layer of smooth muscle, covered by skin

– Enclose & protect other external reproductive organs

• Labia Minora– Flattened, longitudinal folds between labia majora– Composed of connective tissue richly supplied w/ blood vessels

• Clitoris– Small projection at anterior end of vulva between labia minora– Richly supplied w/ sensory nerve fibers

• Vestibule– Enclosed space by labia minora– Vagina opens into posterior portion of vestibule & urethra open in the

midline– Pair of vestibular glands lie on either side of vaginal opening

Female External Reproductive Organs

Female Sex Hormones• Hypothalamus, anterior pituitary gland, & ovaries secrete

hormones

• Hypothalamus secretes gonadotropin-releasing hormone

• Anterior pituitary secretes FSH & LH which play role in controlling female sex cell maturation & in producing female sex hormones

• Female Sex Hormones = Estrogen & Progesterone

Female Sex Hormones• Estrogen

– Ovaries are primary source– Development of breasts & ductile system of mammary glands in

breasts– Increased deposition of adipose tissue in subcutaneous layer, breasts,

thighs, & buttocks– Increased vascularization of skin

• Progesterone– Ovaries are primary source– Promotes changes in uterus during female reproductive cycle– Affects mammary glands– Helps regulate secretion of gonadotropins from anterior pituitary

gland

Female Reproductive Cycle

Mammary Glands• Accessory organs specialized to secrete milk following

pregnancy• Located in subcutaneous tissue of anterior thorax w/in

elevations called breasts• Mammary gland composed of 15-20 lobes

Mammary Glands• Each lobe contains alveolar glands & an alveolar duct which

leads to lactiferous duct

• Dense connective tissue & adipose tissue separate lobes

• Tissues support glands & attach them to fascia of underlying pectoral muscles

• Other connective tissue which forms dense suspensory ligaments, extends inward from dermis to fascia, helping support breast

• Ovarian hormones stimulate development of glands in females