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 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 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