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The Reproductive System


Reproductive system functions in gamete






Fusion of male and female gametes to form a zygote


Introduction to the Reproductive System

Reproductive system includes:

Gonads (testes, ovaries)


Accessory glands and organs

External genitalia


Males and Females


Testes produce spermatozoa

Expelled from body in semen during ejaculation


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


Ductus deferens

Ejaculatory duct

Accessory organs

Seminal vesicles

Prostate gland

Bulbourethral glands

Scrotal sac encloses testes



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



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



Seminiferous tubules

Contain spermatogonia

Stem cells involved in spermatogenesis

Contain sustentacular cells

Sustain and promote development of sperm



Spermatogenesis involves three processes





Anatomy of spermatozoon

Each spermatozoon has:


Nucleus and densely packed chromosomes

Middle piece

Mitochondria that produce the ATP needed to move the 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



Urinary bladder to tip of penis

Three regions





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


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)


Most important androgen

The Reproductive System of the Female

Principle organs of the female reproductive system


Uterine tubes




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


Formation and degeneration of the corpus luteum

Degradation of the corpus luteum


The Uterine tubes

Uterine tubes (Fallopian tubes or oviducts)


End closest to the ovary with numerous fimbriae


The middle portion


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



Major anatomical landmarks




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


Degeneration of the endometrium


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



Labia minora and majora

Paraurethral glands


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:


Stimulates follicular development


Maintains structure and secretory function of corpus luteum


Have multiple functions


Stimulate endometrial growth and secretion

The Physiology of Sexual Intercourse

Male sexual function


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


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


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