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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

 

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