REPRODUCTIVE SYSTEM Vasco Dominic

ORGANISATION

 Reproductive organs which produce gametes and hormones.  Reproductive tract consisting of ducts, store and transport gametes.  Accessory glands and organs that secrete fluids into the ducts of the reproductive system or into other secretory ducts.  Perineal structures associated with the reproductive system, collectively known as external genitalia.

 The male and female systems are functionally different. In the male the gonads are the testes that secrete androgens, principally testosterone and produce a half billion sperms per day.  After storage the sperm travel along a lengthy duct and mixed with secretions of the glands to form semen.  In the female the gonads are the ovaries which produce only one mature gamete per month.  The oocyte travels via a short duct into the muscular uterus. THE MALE REPRODUCTIVE SYSTEM

TESTES

 Each has the shape of a flattened egg rougly 5cm long, 3cm wide and 2.5 cms thick and weighs 10-15 gms.  They hang within the scrotum.  During development the testes form inside the body cavity adjacent to the kidneys.  As the foetus grows they move inferiorly and anteriorly towards the anterior abdominal wall.  The gubernaculum testis is a cord of connective tissue and muscle fibers that extend from the inferior part of each testis to the posterior wall of a small, inferior pocket of the peritoneum.  As growth proceeds the gubernacula do not elongate and the testes are held in position.  During the seventh developmental month: growth continues at a rapid pace, circulating hormones stimulate contraction of the gubernaculum testis.  Over this period the testes move through the abdominal musculature accompanied by small pockets of the peritoneal cavity. This is known as the descent of the testes.  As it moves in the body wall each testes is accompanied by ductus deferens, the testicular blood vessels, nerves and lymphatics bundled together within the spermatic cord.

THE SPERMATIC CORDS

 They consist of layers of fascia, tough connective tissue and muscle enclosing blood vessels, nerves, and lymphatics supplying each testes.  Begins at the deep inguinal ring and extends in the inguinal canal and exits at the superficial inguinal ring, and descends to the testes.

 Each spermatic cord contains the ductus deferens, the testicular artery, the panpiniform, plexus of the testicular vein, and the illioinguinal canal and genitofemoral nerves from the lumbar plexus.  The narrow canal linking the scrotal chambers with the peritoneal cavity are called the inguinal canals.  These canals usually close but are weak points.

THE SCROTUM

 It is divided internally into two chambers.  Each testes occupies a separate compartment , scrotal cavity, with a narrow space separating the inner surface from the outer surface of the testis.  The scrotum consists of a thin layer of skin and the underlying superficial fascia.  The dermis of the scrotum contains a layer of smooth muscle the dartos muscle. Its contraction causes the characteristic wrinkling of the scrotal surface and assists in elevation of the testes.  A layer of skeletal muscle, the cremaster muscle, lies deep in the dermis. Contraction of the cremaster tenses the scrotum and pulls the testes closer to the body.  The cremaster moves the testes away from or towards the body maintaining acceptable temperatures.  Cooling the testes, e.g. in a pool initiates the cremasteric reflex that pulls the testes closer to the body and keep the testicular temperatures from falling.

 Nerve supply to the scrotum: ilioinguinal nerves, genitofemoral nerves and pudendal nerves.  Blood supply: internal pudendal arteries, external pudendal arteries, and the cremasteric branch of the inferior epigastric arteries. STRUCTURE OF THE TESTES

 The tunica albuginea is a dense fibrous layer that surrounds the testis. It is covered by the tunica vaginalis.  The collagen fibers of the tunica albuginea extend into the interior of the testis forming fibrous partitions or septa. The septa converge toward the mediastinum of the testis.  The mediastinum supports blood vessels and lymphatics supplying the testis and ductus. HISTOLOGY OF THE TESTES

 The septa partitions the testis into compartments known as lobules.  About 800 slender tightly coiled seminiferous tubules are distributed among the lobules.  Sperm production occurs in the tubules.  Each seminiferous tubule is U shaped and connected to a single straight tubule that enters the mediastinum of the testis.

 Within the mediastinum straight tubules are extensively interconnected forming a maze of passageway known as rete testis.  15 to 20 large efferent ductules connect the rete testes to the epididymis.  Each tubule is surrounded by a capsule and a loose connective tissue fluid which fills the external spaces between the tubules. The spaces have blood vessels and large interstitial cells known as leydig cells.

SPERMIOGENESIS

 During spermiogenesis, spermatids are embedded within the cytoplasm of sertolli cells which: . Maintain blood testis barrier: tight junctions between the extensions of sertolli cells isolate the luminal portion of the seminiferous tubule from the surrounding interstitial fluid. This regulates transport of materials across the sertolli cells. The lumen of the seminiferous tubules contains fluid rich in androgens, oestrogen, potassium, and amino acids. . Support of spermatogenesis: it depends on the stimulation of the sertolli cells by circulating FSH and testosterone. . Support of spemiogenesis: maturation . Secretion of inhibin which depress the pituitary production of FSH and GnRH. The faster the rate of sperm production the greater the amount of inhibin produced. . Secretion of androgen binding proteins: useful in elevating the conc of androgens in the tubules. ANATOMY OF THE SPERMATOZOON

 Three regions:  Head: flattened oval disc containing densely packed chromosomes. The tip contains acrosomal cap containing enzymes.  Neck: attaches to the middle piece and contains centrioles whose microtubules are continuous with those of the middle piece and tail. It has mitochondria which provide energy needed to move the tail.  The tail: is a flagellum which moves the cell. It has complex corkscrew motion and its microtubules are surrounded by a dense fibrous sheath.

CONCEPT CHECK

 What structures make up the body of the spermatic cord?  Why are inguinal hernias relatively common in males?  How is the location of the testes important in production of viable sperms?  What is the function of the blood testis barrier? THE MALE REPRODUCTIVE TRACT

 Epididymis: lies along the posterior border of the testis.  Consists of a tubule almost 7m long, coiled and twisted so as to take very little space.  Has a head, body and tail.  Head: receives spermatozoa via efferent duct of the mediastinum of the testis.  The body: begins distal to the last efferent duct and extends inferiorly along the posterior margin of the testis.  The tail: its start is marked by the decrease in number of convolutions at the inferior border of the testes. It is the principal region for sperm storage.

FUNCTIONS OF EPIDIDYMIS

 Monitors and adjusts the composition of the fluid produced by the seminiferous tubules. It has pseudostratified epithelium which has cilia which increases SA available for absorption and secretion of tubular fluid.  It acts as a recycling center for damaged spermatozoa.  Stores spermatozoa and facilitates their functional maturation. To become active the spermatozoa undergo capacitation.  Capacitation: spermatozoa become motile when mixed with secretions of the seminal fluid. DUCTUS/VAS DEFERENS

 Begins at the end of the tail of the epididymis and ascends into the abdominopelvic cavity through the inguinal canal as part of spermatic cord.  Inside the abdominal cavity the ductus deferens passes posteriorly curving inferiorly along the lateral surface of the urinary bladder towards the superior and posterior margin of the prostate gland.  Just before joining the prostate it enlarges in an expanded portion known as the ampulla.  The walls have a thick layer of smooth muscle whose peristaltic contractions propel spermatozoa and fluid along the duct.  It is a passageway for spermatozoa and can also store sperm for several months THE URETHRA

 Extends from the urinary bladder to the tip of the penis.  Divided into prostatic, membranous and spongy regions.  Passageway for both urine and reproductive systems.

ACCESSORY GLANDS

 Function to activate and provide nutrients to the spermatozoa and to produce buffers to neutralise the acidity of the urethra and vagina.  Seminal glands: active secretory gland which contributes about 60% of the volume of semen.  Its secretions are high in fructose which is easily used to produce ATP by spermatozoa.  The spermatozoa become highly active after mixing with the secretions of the seminal glands.

 Prostate gland: secretes a weakly acidic fluid (prostatic fluid) that accounts for 20-30% of the volume of the semen. These secretions contain seminal plasmin, which may help prevent urinary tract infections in men.  Bulbourethral (cowper’s) glands: secrete alkaline mucus which has lubricating properties. PROSTRATE GLAND

 The prostate (approximately 3 cm long, 4 cm wide, and 2 cm in AP depth) is the largest accessory gland of the male reproductive system  The glandular part makes up approximately two thirds of the prostate; the other third is fibromuscular.  The firm, walnut-size prostate surrounds the prostatic urethra.  The fibrous capsule of the prostate is dense and neurovascular, incorporating the prostatic plexuses of veins and nerves. LOBES OF THE PROSTRATE GLAND

 Isthmus of the prostrate: lies anterior to the urethra. It is fibromuscular, and contains little glandular tissue.  Posterior lobe: lies posterior to the urethra and inferior to the ejaculatory ducts; it is readily palpable by digital rectal examination.  The right and left (lateral) lobes on either side of the urethra form the major part of the prostate.  The middle (median) lobe lies between the urethra and the ejaculatory ducts and is closely related to the neck of the bladder

SEMEN

 A typical ejaculation releases 2-5mls of semen (an ejaculate) which contains a sperm count of 20 to 100 million sperm per milliliter.  The seminal fluid is a specific mixture of secretions of the accessory glands and contains important enzymes. THE PENIS

 Has a body, shaft (body) and glans.  The skin overlying the penis resembles that of the scrotum.  The prepuce (foreskin) surrounds the tip of the penis.  Preputial glands on the inner surface of the prepuce secrete smegma, a waxy susbstance  Most of the body of the penis consists of three masses of erectile tissue  Beneath the superficial fascia, there are two corpora carvenosa and a single corpora spongiosum that surround the urethra.  When the smooth muscles in the arterial walls relax the erectile tissue becomes engorged with blood producing an erection.

FEMALE REPRODUCTIVE SYSTEM

ANATOMY

 The structures are ovaries, uterine tubes, uterus, vagina and external genitalia.  The ovaries, uterine tubes and uterus are enclosed within an extensive mesentry known as the broad ligament.  A thickened fold of the broad ligament, the mesovarium, supports and stabilizes the position of each ovary.  The broad ligament attaches to the side of the pelvic cavity where it becomes continuous with the parietal peritoneum.

 The pocket formed between the posterior wall of the uterus and the anterior surface of the colon is the rectouterine pouch while the pocket between the anterior wall of the uterus and the posterior wall of the urinary bllader is the vesicouterine pouch. THE OVARIES

 They are held in position by the ovarian ligament and the suspensory ligament.  The ovarian artery and vein enter the ovary at the ovarian hilum.  Each ovary is covered by a tunica albuginea.  Oogenesis occurs monthly in the ovarian follicles as part of the ovarian cycle.  A primordial ovarian follice develop into primary ovarian follicle . Thecal cells surrounding the oocyte release esrogens.  Follicular fluid encourages rapid growth and maturation of only a few secondary ovarian follicles.  Finally one mature ovarian/graafian follicle develops.  The primary oocyte undergoes meiotic division producing a secondry oocyte.  At ovulation a secondary oocyte, surrounded by follicular cells (corona radiata) is released though the ruptured ovarian wall.

 They are among the first organs to be formed as a female baby develops in the uterus.  At the 20-week mark, the structures that will become the ovaries house roughly 6 to 7 million potential egg cells. From that point on, the number begins to decrease rapidly.  A newborn infant has between 1 million to 2 million egg cells. By puberty the number has plummeted to 300,000. For every egg that matures and undergoes ovulation, roughly a thousand will fail, so that by menopause, only a few thousand remain.  During the course of an average reproductive lifespan, roughly 300 mature eggs are produced for potential conception.  The ovaries produce these hormones throughout the fertile period of a woman's life.  It is the hormones that control the menstrual cycle. As you get older and menopause approaches, the ovaries make less and less of these hormones and the periods eventually stop altogether.  So the normal ovaries cannot usually be felt in a clinical examination except in young, thin women.  The ovaries are the main source of female hormones (estrogen and progesterone). These hormones control the development of female body characteristics, such as the breasts, body shape, and body hair. They also regulate the menstrual cycle and pregnancy.

UTERINE TUBES

 Each tube is a hollow muscular tube measuring 13cm in length. Each tube has four regions:  The infindibulum: area closest to the ovary and forms an expanded funnel, with fingerlike projections called fimbriae.  The cells in the infindibulum have cilia that beat towards the middle segment.  The ampulla: is the intermediate portion and the thickness of the smooth muscle layers in its wall increases greatly as it approaches the uterus.  The isthmus: a short segment adjacent to the uterine wall.  The uterine part: opens into the uterine cavity.

 The tubes are the site for fertilisation. For fertilisation to occur the ovum must encounter the spermatozoa during the first 12-24 hrs of its passage from the infindibulum to the uterus. THE UTERUS

 It proves mechanical protection and nutritional support to the developing embryo.  Normally the uterus bends anteriorly near its base (anteflexion).  It is stabilized by broad ligament, uterosacral ligament, round ligament and the cardinal ligaments.  The gross division of the uterus includes the body, fundus, isthmus, cervix, external os, uterine cavity,cervical canal, and internal os.

THE UTERINE WALLS

 The uterine wall has an outer muscular myometrium and inner glandular endometrium or mucosa.  The fundus and anterior and posterior surfaces of the uterine body are covered by a serous membrane continuous with the peritoneal lining. It is know as perimetrium.  The endometrium contributes to 10% of the mass of the uterus. Vast numbers of glands open onto endometrial surface.  Myometrium is the thickest portion of the wall. HISTOLOGY OF THE UTERUS

 The endometrium is divided into an inner functional layer, the layer closest to the uterine cavity and an outer basilar layer adjacent to the myometrium.  The functional layer contains most of the uterine glands and contributes to most of the endometrial thickness.  The basilar layer attaches the endometrium to the myometriumand contains terminal branches of the tubular glands. BLOOD SUPPLY TO THE UTERUS

 The uterus receives blood from the uterine arteries which arise from the internal iliac arteries and ovarian arteries which arise from abdominal aorta.  Within the myometrium, branches of uterine arteries form arcuate arteries that encircle the endometrium.  The radial arteries branch from the arcuate arteries and supply both straight arteries that deliver blood to the basilar layer of the endometrium and spiral arteries that supply the functional layer.

 A typical 28 day uterine cycle begins with the onset of menses and the destruction of the functional layer of the endometrium.  After menses the proliferative phase begins and the functional layer undergoes repair and thickens. RELATIONS TO THE UTERUS

 Anteriorly: the vesicouterine pouch and superior surface of the bladder; the supravaginal part of the cervix is related to the bladder and is separated from it by only fibrous connective tissue.  Posteriorly: the rectouterine pouch containing loops of small intestine and the anterior surface of rectum; only the visceral pelvic fascia uniting the rectum and uterus here resists increased intra- abdominal pressure  Laterally: the peritoneal broad ligament flanking the uterine body and the fascial transverse cervical ligaments on each side of the cervix and vagina; the ureters run anteriorly slightly superior to the lateral part of the vaginal fornix and inferior to the uterine arteries, usually approximately 2 cm lateral to the supravaginal part of the cervix.

BLOOD SUPPLY TO THE UTERUS

THE VAGINA

 Is an elastic muscular tube extending between the uterus and the external genitalia.  It serves as a passageway for menstrual fluids, receives the penis during intercourse and forms the lower portion of the lower canal.  A thin epithelia fold, the hymen, partially blocks the birth canal.  It is lined by stratified squamous epithelium which when relaxed forms rugae (folds).

BLOOD SUPPLY TO THE UTERUS

 From the uterine arteries and some collaterals from the ovarian arteries.  Drained by the uterine veins.

EXTERNAL GENITALIA

 vulva—which runs from the pubic area downward to the rectum.  Mons pubis or "mound of Venus" is the V-shaped area covered with hair  Labia majora or "greater lips" are the part around the vagina containing two glands (Bartholin’s glands)which helps lubrication during intercourse.  Labia minora or "lesser lips" are the thin hairless ridges at the entrance of the vagina, which joins behind and in front. In front they split to enclose the clitoris  The clitoris is a small pea-shaped structure (equivalent to penis in males ) It plays an important part in sexual excitement in females. EXTERNAL GENITALIA

 The urethral orifice or external urinary opening is below the clitoris on the upper wall of the vagina and is the passage for urine  The introitus or opening of the vagina is separate from the urinary opening (unlike males) and located below it.  The hymen is a thin cresentic fold of tissue which partially covers the opening of the vagina. medically it is no longer considered to be a 100% proof of female virginity.

MAMMARY GLANDS [ BREASTS]

 Present in both sexes - normally only functional in females  Developmentally they are derived from sweat glands  Contained within a rounded skin-covered breast anterior to the pectoral muscles of the thorax  Slightly below center of each breast is a ring of pigmented skin, the areola - this surrounds a central protruding nipple  Internally - they consist of 15 to 25 lobes that radiate around and open at the nipple  Each lobe is composed of smaller lobules- these contain alveoli that produce milk when a women is lactating  non-pregnant women - glandular structure is undeveloped - hence breast size is largely due to the amount of fat deposits

 Large sebaceous glands in the areola make it slightly bumpy & produce sebum that reduces chapping and cracking of the skin of the nipple  Autonomic NS controls smooth muscle fibers in the areola and nipple cause the nipple to become erect when stimulated by tactile or sexual stimuli & when exposed to the cold  Lobes are padded & separated from each other by fibrous connective tissue and fat  The connective tissue forms suspensory ligaments that attach the breast to the underlying muscle fascia

GLANDS

 Lesser Vestibular (Paraurethral, Skene's) located on the upper wall of the vagina, around the lower end of the urethra. They drain into the urethra and near the urethral opening  Function - mucus production to aid lubrication during intercourse  Greater Vestibular (Bartholin's):located slightly below and to the left and right of the opening of the vagina.  They secrete mucus to provide lubrication, especially when the woman is sexually aroused. CONCEPT REVIEW

 How could scarring of the uterine tubes cause infertility?