Male+Reproductive+System

=**Objectives**=


 * 1. List the organs and ducts of the male reproductive system.**

The organs and ducts of the male reproductive system include the testis, the duct system, the accessory glands, and the penis. The duct system can be divided into the intratesticular and extratesticular duct systems. The intratesticular duct system includes the straight tubules, rete testis, and efferent ducts. The extratesticular duct system includes the ductus epididymus, ductus deferens, ejaculatory ducts, and urethra. The accessory glands include the seminial vesicles, prostate gland, and Cowper’s (bulbourethral) gland.


 * 2. Describe and integrate the components and their morphology of the testis wth the function of the testis.**

The testis have an endocrine and exocrine function. They are basically a large compound tubular gland, surrounded by a layer of dense irregular CT capsule known as the tunica albuginea, which has infoldings known as septula that divide the testis into lobules. The embryological remnant of the peritoneal outpocketing during descent of the testis into the scrotum is known as the tunica vaginalis, which allows the testis to move freely in the scrotum(usually not patent to the abdominal cavity in adults). Each lobule represents a functional sperm-producing unit of the testis. The parenchymal tissue of the lobule are known as the seminiferous tubules, highly coiled tubes approximately 4m long, representing the exocrine (cytocrine secretion) portion of the organ. The epithelium is a specialized "Stratified seminiferous epithelium": Lined by germinal epithelium (4-8 layers thick) -Basement membrane -Spermatogenic cells-- most prevalent type, undergoing meiosis -Sustentacular(Sertoli) cells


 * 3. Describe the process of spermatogenesis and indicate how it differes from oogenesis. Distinguish "spermatogenesis" from "spermiogenesis."**

Spermatogenesis is the differentiation of spermatogonia into functioning spermatozoa. Spermiogenesis is the final stage of spermatogenesis which sees the maturation of spermatids into mature, motile spermatozoa. Spermatogenesis is different from oogenesis in that it occurs continuously and produces millions of gametes. Spermatogonia are transformed into spermatozoa through 5 stages of developmet woth the first 4 occuring in the testis and the fonal developmet in the epididymis.


 * 4. Describe and identify the adluminal and basal compartments of the seminiferous tubules.**

The basal compartment is adjacent to the basal membrane and contains only spermatogonia. The adluminal compartment is above the lateral processes and contains primary spermatocytes, secondary spermatocytes and spermatids opening onto the lumen of the tubule.


 * 5. Describe, in detail, the morphology and function of the epithelium in the seminiferous tubules including the different germ cells and the Sertoli cell. Identify the phases of spermatogenesis.**

The epithelium of the seminiferous tubules is made up of stratified epithelium, also known as germinal epithelium. It contains 4 to 8 layers and is made up of 2 cell types : spermatogenic cells and sustentacular (or Sertoli) cells. The spermatogenic cells undergo differentation as they migrate to the lumen and are released. 5 stages/phases are recognized here: 1. Spermatogonia: the most primitive //germ cell// that is located on the basement membrane of the tubule. It has stem cells that act as a reservoir of dividing cells (A cells). B cells go on to differentiate as they migrate up. 2. Primary spermatocytes: the most common cell and are undergoing the first meiotic division. They still have diploid # of chromosomes. 3. Secondary spermatocytes: very brief stage not seen on slides. This is when they are undergoing the second meiotic division to have haplod # of chromosomes. 4. Spermatids: are located near the surface apex of Sertoli cells. They have round, solid, dark chromatin and cytoplasmic bridges that still connect daughter cells. 5. Spermatozoa: now have a head and a long tail. They remain connected by intercellular bridges and are still located at the apex of Sertoli cells. The Sertoli cells are made up of tall columnar cells that rest on the basement membrane and have oval shaped nuclei with prominent nucleoli. They are joined together by tight junctions, and they support and organize the epithelium by dividing it into 2 compartments: basal and adluminal compartments. Their structure allows them to form the blood testis barrier ensuring that all materials entering the adluminal compartment must pass through the Sertoli cells before reaching the sex cells.


 * 6. Explain what is meant by the "cycle of seminiferous epithelium."**

The five stages that sequentially follow each other down the tube 6 complete cycles occurring with one spermatogentic wave in each quarter (24 total). Waves in one section are not in phase within other quarters of tube


 * 7. Describe and integrate the hormonal secretions that control the development and maintenance of the normal male reproductive system.**

GnRH from the hypothalamus stimulates the anterior pituitary to secrete LH and FSH. LH secretion binds to receptors on Leydig cells which stimulate them to produce testosterone. FSH stimulates Sertoli cells to produce androgen-binding protein which binds testosterone and raises levels high enough to stimulate proliferation and differentiation of spermatogenic cells. Testosterone is also required for the normal functioning of seminal vesicles, prostate, and bulbourethral glands as well as the appearance and maintenance of male secondary sexual characteristics. High levels of testosterone inhibit the release of LH. Sertoli cells produce inhibit which inhibits FSH secretion.


 * 8. Describe the specific epithelial lining of the tubuli recti, rete testis, efferent ductules, epididymis, ductus deferens, and ejeculatory duct. Identify examples of each and be able to integrate their morphology with their function.**


 * Duct: || Epithelium Type || Function ||
 * Tubuli recti || Sertoli cells to simple cuboidal epithelium || Short, transport spermatozoa from apex of sertoli cells to rete testis ||
 * Rete Testis || simple cuboidal epithelium || multiple interconnecting channels, transport sperm to efferent ductules ||
 * Efferent Ductules || Alternating tall ciliated columnar with low cuboidal epithelium-- "Sawtooth" || Ciliated cells move sperm, nonciliated cells resorb testicular fluid. Only motile cilia in male reproductive tract. ||
 * Epididymus || Psuedostratified columnar epithelium, Basal(Stem) and Principal(stereociliated) cells || Resorption of 90% of testicular fluid, has a layer of SMC to move sperm by peristalsis (thickens towards tail). Store sperm in tail, and produce glycerophosphocholine to inhibit capacitation of sperm. "Quality Control" checkpoint. ||
 * Ductus Deferens || Large stellate lumen, very thick muscularis, and psuedostratified columnar epithelium (no cilia) || Designed to quickly propel sperm from epididymus to Ejaculatory Duct during emission. ||
 * Ejaculatory Duct || Simple columnar epithelium with no muscularis || Designed to receive secretions of seminal vesicle and ductus deferens-- propulsion is achieved via contraction of the prostate gland surrounding the duct. ||


 * 9. Describe and integrate the morphology and function of the seminal vesicles, prostate and bulbourethral glnds. Be able to list characteristics necessary to distinguish one from the other. Explain the clinical significance of the mucosal glands, submucosal, and main glands of the prostate.**

The seminal vesicles are large saccular convoluted tubes, with numerous cavities of various sizes. The epithelial surface is pseudostratified columnar, with SMC's in the walls, and a distinctive ridged mucosa with a "honeycomb" appearance.

The prostate is the largest accessory gland, and surrounds the prostatic urethra and ejaculatory ducts. It has a thin CT capsule, with thick fibromuscular septae between its glands. Its glands consist of 30-50 branched tubuloalveolar glands in three regions: -Small Mucosal Glands (nearest to urethra, responsible for urethral constriction in Benign Prostatic Hyperplasia), -Larger Submucosal Glands, and -Most common/Largest Main Glands(Most common site for prostate cancer). The alveolar lumens of the glands will be of varying sizes and shapes, and there will be no visible ductwork. A young prostate will have columnar epithelium, but as the prostate ages, it developes cuboidal epithelium and concretions (red, layered bodies).

The bulbourethral glands have compound tubuloalveolar glands, and secrete mucous.

The penis consists of three erectile bodies, each encased in their own sheath of tunica albuginea: -2x Corpus Cavernosum( trabeculated tissue with lacunae, occupued by helicine arteries and one deep artery of the penis per body of tissue), - Corpus Spongiosum (looser tunica albuginea, carries penile urethra inside it, widens superiorly to form glans of penis and fossa navicula)
 * 10. Describe the morphology of the penis including the fascial layers, erectile tissue, blood vessels, as well as, the site and epithelial lining of the penile urethra. Be able to relate and integrate the morphological components of the penis in the flaccid and erect condition.**

On the dorsal aspect of the penis, between the tunica albuginea and the Buck's fascia (Deep fascia of penis), are paired arteries and nerves, and a single Deep Dorsal Artery of the Penis(drains the body of the penis), and outside the Buck's fascia is the Dorsal Vein of the Penis, which drains the skin of the penis.

In the flaccid condition, the coiled helicine arteries of the penis are constricted by sympathetic innervation to the SMC's in their walls. The blood drains through AV shunts to the deep dorsal vein. When sexually stimulated, the parasympathetic nervous system allows the coiled arteries to relax, and the AV shunts close, allowing the erectile tissue to swell against the tunica albuginea and become turgid.

The normal pathway of sperm secretion is as follows: Spermatozoa leave the seminiferous tubules via the straight tubules (tubuli rectii) and traverse the labrynthine rete testis to the efferent ductules, where they are drained of a majority of the testicular fluid surrounding them and propelled via cilia to the Epididymus. In the Epididymus, glycerophosphocholine is secreted to prevent capacitation of the sperm, and they are stored in the tail of the epididymus until emission. During emission, the peristaltic contractions of the Epididymus and the Vas Deferens rapidly propel the sperm towards the ejaculatory duct, where they combine with nutritive secretions from the seminal vesicles and pass through the prostatic urethra on their way to the membranous urethra, then on to the penile urethra and out they go.
 * 11. Be able to trace the normal pathway of sperm secretion. Be able to describe the morphology of the pathway and how it relates to the specific function of each part.**

Ejaculation involves two distinct phases, emission and ejaculation proper. An erection is achieved through parasympathetic stimulation. Emission caused by sympathetic nervous system stimulation. During emission the ductous defrens contract to expel sperm into the ejaculatory ducts where it is mixed with secretions of the seminal vessicles, bulbourethral glands and prostate to form semen. The semen is then expelled by rhythmic contrations of the prostate and bulbospongiosus which compress the urethra.
 * 12. Describe the process of ejaculation and integrate it with the function of the various male reproductive componenents.**


 * Terms:**

__Tunica Albuginea (testis & penis)__ The tunica alburginea of the testis is a thick layer of dense irregular connective tissue that forms a capsule around the testis. It contains the mediastinum testis on the posterior side.

The tunica alburginea of the penis is a dense layer of connective tissue that surrounds each of the the corpus cavernosum and corpus spongiosum erectile bodies.

__Tunica Vaginalis__ A serous cavity that partially surrounds the anterior surface of the testis. The tunica vaginalis is a remnant of a peritoneal outpocketing during development as the testis descends through the inguinal canal into the scrotum. It is lined by simple cuboidal epithelium and allows the testis to slide around freely within the scrotum. It has a visceral and parietal layer.

__Mediastium Testes__ Part of the tunica albuginea CT capsule that surrounds the posterior surface of the testis. It is basically a thickened CT region on the posterior aspect. Radiating from the mediastium testis is the connective tissue septula that subdivide each testis into lobules.

__Germinal Epithelium__ 4-8 layers of stratified epithelial cells on the seminiferous tubule. They are surrounded by a thin CT layer and have a basement membrane located in between. It is composed of spermatogenic cells and sustentacular cells. Spermatogenic cells are the most prevalent and undergo meiosis. Sustentacular cells or Sertoli cells (a.k.a. nurse cells) and are supportive in nature, organizing the structure of the tubule.

__Androgen-Binding Protein__ Synthesized by Sertoli cells to facilitate in increasing the concentration of testosterone in the seminiferous tubule germinal epithelium by binding to it and preventing it from leaving the tubule. High levels of testosterone is necessary to stimulate proliferation and differentiation of spermatogenic cells. FSH stimulates Sertoli cells into producing androgen-binding protein. High levels of testosterone inhibits LH release.

__Spermatogonia__ The most primitive male germ cell that is loced on the basement membrane of the seminiferous tubule. It is a stem cell that acts as a reservoir for dividing A (dark) cells, which make new generations of A (dark) cells and B (light) cells. B (light) cells undergo differentiation as they migrate upward towards the lumen.

__Primary and Secondary Spermatocytes__ Primary spermatocytes are the most commoncell in the germinal epithelium. They have clumped chromosomes as they are undergoing their first meiotic division. They still have a diploid number of chromosomes.

Secondary spermatocytes are a very brief stage where the spermatocytes undergo their second meiotic division. They have a haploid number of chromosomes.

__Spermatids__ Spermatidshave around, solid dark chromatin patterns and are located near the surface apex of Sertoli cells. They still maintain cytoplasmic bridges connecting daughter cells.

__Spermatozoa__ Spermatids are transformed into spermatozoa. They have a head with dark, flattened nuclei, and long tails. They are still connected by intercellular bridges and are located at the apex of the Sertoli cell and still embedded in the cell. //Spermiogenesis// refers to the transformation of spermatids into mature spermatozoa.

__Seminal Colliculus__ A bump formed on the posterior side of the prostatic urethra where the two ejaculatory ducts, and the prostatic utricle open.

__Cowper's Glands__ Also known as bulbourethral glands and are accessory sex glands located in the UG diaphragm. They are compound tubuloalveolar glands with a simple cuboidal epithelium. It secretes a viscus mucus that acts as a lubricant.

__Utricle__ The prostatic utricle or utriculus masculina is a blind end pouch located in the seminal colliculus, between the two openings of the ejaculartory ducts. The paramesonephric (Müllerian) duct obliterates in the male, forming the prostatic utricle; it is a homologue to the uterus and part of the vagina.

__Pampiniform Plexus__ A venous plexus that surrounds the vas deferens and the spermatic artery. Blood returning from the testis cools off the warmer blood going into the testis via the spermatic artery through countercurrent theory.

__Blood Testis Barrier__ Sertoli cells form the blood testis barier by extending their lateral processes to meet adjacent Sertoli cells. Tight junctions hold these cells together to form an irregular membrane or sheet around the circumference of the seminiferous tubule, dividing the epithelium into the basal and adluminal compartments. Material entering the adluminal compartment to must pass through the Sertoli cell to reach the sex cells. This prevents immune reactions with sex cells of different genetic type than the body.

__Leydig Cells__ Also known as interstitial cells because they are found in the connective tissue of the testes. They consist of clumps of endocrine secreting cells between the tubules in the lobules of the testes. They are the target cell of LH from the anterior pituitary which causes them to secrete testosterone via merocrine secretion oduce

__Vasectomy__ Consists of bisecting the vas deferens and typing off the ends as a from of birth control. Can be reversed within a year or two, before the sex cells die.

__Prostatic Hypertrophy__ Benign prostatic hypertrophy occurs in older men and bloc the urethra. Occurs in 40% of males 50 years old and 95% of males 80 years old.

__Prostatic Concretions__ Red-staining, layered bodies located in the lumen of the tubuloalveolar glands of the prostate that increase in size and number with age. These concretions are composed of calcified glycoproteins, but the significance of these concretions is not understood.

__Impotence__ Impotence is the inability to achieve and erection; this can be caused by a vascular problem, nerve damage, or psychological problems.

__Sterile__ A normal male has 50-100 million sperm/mL of semen. If there are less than 20 million sperm/mL of semen, that male is considered sterile.

__Ejaculation__ The forceful expulsion of semen from the penile urethra. The bulbospongiousus muscle contracts around the corpus spongiosum to force the semen out of the penile urethra.