The Reproductive System

•Reproductive system functions in gamete

•Production

•Storage

•Nourishment

•Transport

•Fertilization

•Fusion of male and female gametes to form a zygote

Introduction to the Reproductive System

Reproductive system includes:

•Gonads (testes, ovaries)

•Ducts

•Accessory glands and organs

•External genitalia

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Males and Females

•Males

•Testes produce spermatozoa

•Expelled from body in semen during ejaculation

•Females

•Ovaries produce oocytes

•Immature ovum

•Travels along uterine tube toward uterus

•Vagina connects uterus with exterior of body

The Reproductive System of the Male

Male Reproductive System

•Pathway of spermatozoa

•Epididymis

•Ductus deferens

•Ejaculatory duct

•Accessory organs

•Seminal vesicles

•Prostate gland

•Bulbourethral glands

•Scrotal sac encloses testes

•Penis

The testes

•Descent of the testes

•Movement of testes through inguinal canal into scrotum

•Occurs during fetal development

•Testes remain connected to internal structures

•Spermatic cords

Male Anatomy

•Musculature of scrotal sac

•Dartos muscle wrinkles scrotal sac

•Cremaster muscle pulls sac close to body

•Testes anatomy

•Tunica albuginea surrounds testis

•Septa extend from tunica albuginea to epididymus

•Lobules

Sperm production

•In seminiferous tubules

•Interstitial cells between seminiferous tubules

•Secrete sex hormones

•Sperm pass through rete testis

•Efferent ductules connect rete testis to epididymus

Spermatogenesis

•Seminiferous tubules

•Contain spermatogonia

•Stem cells involved in spermatogenesis

•Contain sustentacular cells

•Sustain and promote development of sperm

Spermatogenesis

•Spermatogenesis involves three processes

•Mitosis

•Meiosis

•Spermiogenesis

Anatomy of spermatozoon

•Each spermatozoon has:

•Head

•Nucleus and densely packed chromosomes

•Middle piece

•Mitochondria that produce the ATP needed to move the tail

•Tail

•The only flagellum in the human body

Male reproductive tract

•Testes produce mature spermatozoa

•Sperm enter epididymus

•Elongated tubule with head, body and tail regions

•Monitors and adjusts fluid in seminiferous tubules

•Stores and protects spermatozoa

•Facilitates functional maturation of spermatozoa

Ductus deferens AKA vas deferens

•Begins at epididymus

•Passes through inguinal canal

•Enlarges to form ampulla

•Ejaculatory duct at base of seminal vesicle and ampulla

•Empties into urethra

Urethra

•Urinary bladder to tip of penis

•Three regions

•Prostatic

•Membranous

•Penile

Accessory glands

•Seminal vesicles

•Active secretory gland

•Contributes ~60% total volume of semen

•Secretions contain fructose, prostaglandins, fibrinogen

Accessory glands

•Prostate gland

•Secretes slightly acidic prostate fluid

•Bulbourethral glands

•Secrete alkaline mucus with lubricating properties

Contents of Semen

•Typical ejaculate = 2-5 ml fluid

•Contains between 20 – 100 million spermatozoa per ml

•Seminal fluid

•A distinct ionic and nutritive glandular secretion

External genitalia

•Male external genitalia consist of the scrotum and the penis

•Skin overlying penis resembles scrotum

•Penis

•Contains three masses of erectile tissue

•2 corpora cavernosa beneath fascia

•1 corpus spongiosum surrounding urethra

•Dilation of erectile tissue produces erection

Hormones and male reproductive function

•FSH (Follicle stimulating hormone)

•Targets sustentacular cells to promote spermatogenesis

•LH (leutinizing hormone)

•Causes secretion of testosterone and other androgens

•GnRH (Gonadotropin releasing hormone)

•Testosterone

•Most important androgen

The Reproductive System of the Female

Principle organs of the female reproductive system

•Ovaries

•Uterine tubes

•Uterus

•Vagina

Support and stabilization

•Ovaries, uterine tubes and uterus enclosed within broad ligament

•Mesovarium supports and stabilizes ovary

The ovaries

•Held in position by ovarian and suspensory ligaments

•Blood vessels enter at ovarian hilus

•Tunica albuginea covers ovary

•Ovum production

•Occurs monthly in ovarian follicles

•Part of ovarian cycle

•Follicular phase (preovulatory)

•Luteal phase (postovulatory)

The ovarian cycle

•Steps in the ovarian cycle

•Formation of primary, secondary, and tertiary follicles

•Ovulation

•Formation and degeneration of the corpus luteum

•Degradation of the corpus luteum

The Uterine tubes

•Uterine tubes (Fallopian tubes or oviducts)

•Infundibulum

•End closest to the ovary with numerous fimbriae

•Ampulla

•The middle portion

•Isthmus

•A short segment connected to the uterine wall

Each uterine tube opens directly into uterine cavity

•Fertilization occurs in uterine tube

•12-24 hours after ovulation

•During passage from infundibulum to uterus

The uterus

•Muscular organ

•Mechanical protection

•Nutritional support

•Waste removal for the developing embryo and fetus

•Supported by the broad ligament and 3 pairs of suspensory ligaments

Uterus

•Major anatomical landmarks

•Body

•Isthmus

•Cervix

•Cervical os (internal orifice)

•Uterine cavity

•Cervical canal

•Internal os (internal orifice)

Uterine wall consists of three layers:

•Myometrium – outer muscular layer

•Endometrium – a thin, inner, glandular mucosa

•Perimetrium – an incomplete serosa continuous with the peritoneum

•Repeating series of changes in the endometrium

Uterine cycle

•Repeating series of changes in the endometrium

•Continues from menarche to menopause

•Menses

•Degeneration of the endometrium

•Menstruation

•Proliferative phase

•Restoration of the endometrium

•Secretory phase

•Endometrial glands enlarge and accelerate their rates of secretion

The vagina

•Major functions

•Passageway for elimination of menstrual fluids

•Receives the penis during sexual intercourse

•Forms the inferior portion of the birth canal

External genitalia

•Vulva

•Vestibule

•Labia minora and majora

•Paraurethral glands

•Clitoris

•Lesser and greater vestibular glands

Mammary glands

•Pectoral fat pad

•Nipple surrounded by the areola

•Function in lactation under control of reproductive hormones

Hormones of the female reproductive cycle

•Control the reproductive cycle

•Coordinate the ovarian and uterine cycles

Hormones of the female reproductive cycle

•Key hormones include:

•FSH

•Stimulates follicular development

•LH

•Maintains structure and secretory function of corpus luteum

•Estrogens

•Have multiple functions

•Progesterones

•Stimulate endometrial growth and secretion

The Physiology of Sexual Intercourse

Male sexual function

•Arousal

•Leads to erection of the penis

•Parasympathetic outflow over the pelvic nerves

•Emission and ejaculation

•Occur under sympathetic stimulation

•Results in semen being pushed toward external urethral opening

•Detumescence

•Subsidence of erection

•Mediated by the sympathetic nervous system

Female sexual function

•Stages are comparable to those of male sexual function

•Arousal causes clitoral erection

•Vaginal surfaces are moistened

•Parasympathetic stimulation causes engorgement of blood vessels in the nipples

Aging and the Reproductive System

Menopause

•The time that ovulation and menstruation cease

•Typically around age 45-55

•Accompanied by a decline in circulating estrogen and progesterone

•Rise in GnRH, FSH, LH

Male climacteric

•Levels of circulating testosterone begin to decline

•FSH and LH levels rise

•Gradual reduction in sexual activity