Reproductive System Chapter 19

Introduction Connected system of organs and gland that produce and nurture sex cells and transport them to sites of fertilization Male sex cells are sperm Female sex cells are oocytes Sex cells have one set of genetic instructions carried on 23 chromosomes

Organs of the Male RS (1)Produce and maintain sex cells, (2) transport them and supporting fluids to the outside, and (3)secrete male sex hormones Primary Two testes Accessory Internal and external organs

Testes Ovoid structures about 5 cm in length and 3 cm in diameter Within the cavity of the scrotum Contains seminiferous tubules, each 70 cm long uncoiled Form channels which give rise to ducts that join a tube called the epididymis Coils on the outer surface of the testis and continues to become the vas deferens

Lining the seminiferous tubules is stratified epithelium with spermatogenic cells which give rise to sperm cells Interstitial cells lie in the spaces between the seminiferous tubules and produce and secrete male sex hormones

Formation of Sperm Cells Process called spermatogenesis In male embryo, spermatogenic cells are undifferentiated and are also called spermatogonia Each spermatogonia contains 46 chromosomes During embryonic development, hormones stimulate spermatogonia to undergo mitosis At puberty, they reproduce by meiosis and are then haploid

Sperm Cells Produced continually throughout their reproductive lives Produced continually throughout their reproductive lives Collect in the lumen of each seminiferous tubule, and then pass to the epididymis, where they accumulate and mature Tiny, tadpole-shaped structure about 0.06 mm long Flattened head (chromatin, acrosome), a cylindrical midpiece(mitochondria), and an elongated tail

From the epididymis sperm travel through the vas deferens Just outside the prostate gland it unites with the duct of a seminal vesicle to form an ejaculatory duct, which passes through the prostate gland and empties into the urethra The seminal vesicle secretes: A slightly alkaline fluid (regulate pH) Fructose (energy) Prostaglandins (stimulate contractions)

The prostate gland secretions neutralize fluid, enhance motility, and neutralize secretions of vagina Two bulbourethral glands secrete mucuslike fluid to lubricate end of penis Semen consists of sperm cells and secretions of the seminal vesicles, prostate gland, and bulbourethral glands Volume of semen: 2-5 mL; 120 million per mL

External Accessory Organs Scrotum – pouch of skin and tissue which encloses and protects testes; helps regulate temp. Penis – conveys urine and semen through the urethra to the outside; contains erectile tissue Glans penis – sensitive, cone-shaped, bears urethral opening Prepuce – begins posterior to the glans and extends anteriorly to cover the glans as a sheath; often removed surgically (circumcision)

During sexual stimulation… Parasympathetic nerve impulses from the sacral portion of the spinal cord release the vasodilator nitric oxide, dilating the arteries leading to the penis Veins of the penis are compressed reducing flow of venous blood away Blood accumulates in erectile tissues, and the penis swells and elongates, producing an erection

The culmination of sexual stimulation is orgasm, a pleasurable feeling of physiological and psychological release Accompanied by emission (movement of semen into the urethra) and ejaculation (force of semen through urethra to outside)

Organs of the Female Reproductive System Produce and maintain oocytes Transport oocytes to site of fertilization Provide a favorable environment for a developing offspring Produce female sex hormones

Primary Sex Organs (ovaries) Solid, ovoid structures about 3.5 cm long, 2 cm wide and 1 cm thick During prenatal development, small groups of cells in the outer region of the ovarian cortex form several million primordial follicles Each follicle contains a single, large cells called a primary oocyte

Early in development, primary oocytes begin to undergo meiosis, but soon halts, until puberty Over 400,000 are present at puberty, but only 400 are released during a female’s reproductive life Oogenesis is the process of egg cell formation

Beginning at puberty, some primary oocytes are stimulated to continue meiosis When a primary oocyte divides, the distribution of cytoplasm is unequal One of the resulting cells, called a secondary oocyte, is large and the other, called the first polar body is small Large secondary oocyte can be fertilized by a sperm cell Upon fertilization, the secondary oocyte divides unequally to produce a tiny second polar body and a large fertilized egg cell, also called a zygote

Follicle Maturation At puberty, the anterior pituitary gland secretes increased amounts of FSH and ovaries enlarge in response Primary oocyte enlarges and surrounding follicular cells proliferate by mitosis In time, the mature follicle reaches a diameter of 10 mm or more and bulges outward on the ovary surface like a blister As many as 20 may begin maturing at any one time, but one usually outgrows the others

After oogenesis, ovulation releases the secondary oocyte and first polar body which are surrounded by follicular cells Hormones from the anterior pituitary gland trigger ovulation, rapidly swelling the mature follicle and weakening its wall Wall ruptures and follicular fluid and the secondary oocyte ooze from the ovary’s surface Propelled to the opening of a nearby uterine tube

Internal Accessory Organs Uterine tubes Epithelium secretes mucus and the cilia beat toward the uterus Muscles help transport secondary oocyte down uterine tube Uterus If secondary oocyte is fertilized in uterine tube, becoming an ovum, the uterus receives the embryo and sustains its development

Lower third called the cervix Opens to the vagina Wall has three layers Endometrium (glands) Myometrium (muscles) Perimetrium (serosa) Vagina Conveys uterine secretions Receives erect penis Provides an open channel during birth

Female External Reproductive Organs Labia majora enclose and protect the other external organs; correspond with scrotum in males and are composed of adipose tissue Labia minora are flattened, longitudinal folds between the labia majora; composed of connective tissue richly supplied with blood vessels

Clitoris is a small projection at the anterior end of the vulva between the labia minora; 2 cm long; corresponds to penis in males; erectile tissue; glans penis Vestibule contains glands that correspond to the bulbourethral glands in males

Response to sexual stimulation Parasympathetic nerve impulses release vasodilator, causing arteries associated with the erectile tissues to dilate Vagina expands and elongates Vestibular glands secrete mucus into vestibule Culmination of local stimulation of clitoris is orgasm Walls of uterine walls and uterine tube contract rhythmically

Hormonal Control Reproductively immature until about age 10 Hypothalamus secretes GnRH which stimulates anterior pituitary gland to release FSH and LH (control sex cell maturation and production of female sex hormones)

Estrogen Stimulate enlargement of vagina, uterus, uterine tubes, ovaries, mammary glands, breasts Increases deposition of adipose tissue in breasts, thighs, and buttocks Increases vascularization of the skin

Progesterone Promotes changes in the uterus during the female reproductive cycle Affects mammary glands Helps regulate the secretion of gonadotropins from the anterior pituitary

Androgen Increases hair growth in the pubic and axillary regions Response to low amts. is narrow shoulders and broad hips

Reproductive Cycle Regular, recurring changes in the uterine lining, which culminate in menstrual bleeding Changes in the ovary constitute the ovarian cycle

Menopause Late 40s or early 50s, cycles become increasingly irregular Within a few months or years, they cycles cease occurs when a woman's ovaries run out of functioning eggs

Mammary Glands Specialized to secrete milk following pregnancy Nipple located near the tip Circular area of pigmented skin, called the areola, surrounds each nipple Composed of lobes each

Complications in female reproductive system Ectopic pregnancy Cervical cancer Endometriosis

Birth Control Coitus interruptus Rhythm method Mechanical barriers Male condom Female condom Diaphragm Cervical cap Chemical barriers spermicide Combined hormone contraceptives Monthly injection Chemical ring Patch Oral contraceptive (“the pill”) Medroxyprogesterone acetate Medroxyprogesterone acetate IUD Surgical methods

Sexually Transmitted Diseases Six most common AIDS (virus) Chlamydia (bacterium) Genital herpes (virus) Genital warts (HPV) Gonorrhea (bacteria) Syphilis (bacteria) Symptoms Burning sensation during urination Pain in the lower abdomen Fever or swollen glands in the neck Discharge from vagina or penis Pain, itching, inflammation in genital or anal area Pain during intercourse Sores, blisters, bumps, or a rash Itchy, runny eyes

Fertilization