HISTO: Male Reproductive system

Major processes of Spermiogenesis: Describe acrosome formation

*Acrosome formation*: 1. Acrosome is a large specialized lysosome—acrosome contents are rich in carbohydrate and hydrolytic enzymes such as: a. *Hyaluronidase* b. *Acid phosphatase* c. *Acrosin: a trypsin-like protease* 2. Together these substances aid in penetrating the egg's corona radiata and zona pellucida during fertilization

Overview: Hormonal control of Testosterone/Spermatogenesis:

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Accessory genital Glands: Describe the corpora amylacea in the prostate gland

1. *Corpora amylacea* can be found in the lumen of the gland a. Glycoprotein spheres become larger, more numerous, and calcified with age, but their significance is unknown.

Support Cells: What are the two support cells?

1. *Supporting (Sertoli) cells* 2. *Interstitial (Leydig) Cells*

Intratesticular genital ducts: Describe the Rete testis

1. Anastomosing network of tubules lying in the mediastinum testis 2. The rete testis is lined by low cuboidal epithelium

How can cells at different steps in the process of spermatogenesis be identified?

1. Cells at different steps of spermatogenesis can be identified according to their: a. Size b. Nuclear morphology c. Position in the epithelium

Major processes of Spermiogenesis: Describe migration of the centrioles and formation of the flagellum

1. Centrioles migrate to the spermatid's posterior pole 2. Flagellum emerges from one centriole that is perpendicular to the cell surface and forms the tail. 3. The other centriole forms a collar around the base of the flagellum

Penis: Describe the corpus spongiosum of the penis

1. Corpus spongiosum: a single, smaller, ventral cylinder surrounded by a thin connective tissue sheath a. Penetrated along its length by the penile urethra. 2. Expanded distal tip is the glans penis

Major processes of Spermiogenesis: Describe the shift of cytoplasm toward the flagellum during spermiogenesis

1. Cytoplams shifts toward the flagellum 2. Excess cytoplasm forms a *residual body*

General Organization of the Testes: Describe the Tunica albuginea

1. Dense fibrous connective tissue capsule that surrounds and continues into the testes creating septations.

Duct system: What are the major components of the Excretory Genital Ducts?

1. Ductus epididymis 2. Ductus deferens (vas deferens) 3. Ejaculatory duct 4. Urtehra

General Organization of the Testes: Describe the lobules of the testes

1. Each lobule includes 1 - 4 seminiferous tubules (exocrine component) 2. Loose vascular connective tissue between the tubules that contains discrete clumps of testosterone-*secreting interstitial cells of Leydig* (endocrine component)

Accessory genital Glands: Describe the structure that surrounds the prostate gland

1. Entire gland is surrounded by a fibroelastic capsule containing smooth muscle that contracts during ejaculation, expelling the prostatic fluid into the urethra. 2. Extensions of the capsule form septa that penetrate the gland dividing it into indistict lobes: a. Posterior, median, and two lateral lobes 3. Common site of disease in men over 50 years old.

Excretory Genital Ducts: Describe the urethra

1. Genitourinary passageway shared by the urinary and reproductive system 2. Contains small, mucus-secreting *glands of Littre* in its wall.

Penis: Overview of the mechanism of an erection

1. In the flaccid state, arterial vessels are constricted and venous vessels are noncompressed 2. On erection, smooth muscle relaxation in the trabeculae and arterial vasculature results in increased blood flow. a. The increased blood flow rapidly fills and dilates the cavernosal spaces. b. Venous outflow drops as the expanding cavernosal spaces compress the venous plexus and the larger veins passing through the tunica albuginea.

General Features of the Male Reproductive System: Describe intra-testicular ducts

1. Located within the testes, these are continuous with the seminiferous tubules and include the: a. *Tubuli recti* b. *Rete testis* c. *Ductuli efferentes* (efferent ductules)

Describe the general structure of the seminiferous tubules:

1. Long narrow tubules that are highly convoluted and packed into a small space 2. Walls of each tubule, from the exterior to the lumen, composed of 3 layers: a. Tunica propria b. Well-defined basal lamina c. Stratified seminiferous epithelium

General Features of the Male Reproductive System: What is the role of temperature in spermatogenesis and how do the testes control this process?

1. Normal production of spermatozoa occurs only at *35 degrees C.* 2. Maintenance of ideal temperature is aided by the pampiniform plexus of veins that surround each testicular artery a. It contains cooler blood returning from the scrotum and cools the blood supply traveling towards the testes before it reaches them through a counter-current heat exchange.

General Features of the Male Reproductive System: What are the glands of the male reproductive system?

1. Paired testes 2. Accessory glands a. Seminal vesicles b. Prostate gland c. Bulbourethral gland

Penis: Describe the parasympathetic innervation of the penis

1. Parasympathetic stimulation causes erection by relaxing smooth muscle within the trabecula and dilating the *helicine arteries*. 2. This leads to increased blood flow into the cavernous spaces and *closes off the arteriovenous shunts*

Describe the process of spermiogenesis included the major steps:

1. Process of differentiation by which spermatids become spermatozoa 2. Includes the following processes: a. Acrosome formation b. Migration of the centrioles and formation of the flagellum c. Shift of cytoplasm toward flagellum—excess cytoplasm forms a *residual body* d. Migration of mitochondria

Blood-Testis Barrier: Why is the blood-testis barrier important?

1. Spematogenesis involves the appearance of new sperm-specific proteins and glycoproteins on the differentiating spermatogenic cells. 2. These surface molecules may be recognizes as non-self antigens by the immune system 3. Blood-testis barrier *protects the developing sperm from damage by an autoimmune response.*

Describe spermatocytogenesis of spermatogonia:

1. Spermatocytogenesis: the production of primary spermatocytes from spermatogonia through a series of standard mitotic divisions 2. Division of these cells produce 2 types of spermatogonia, a new germ cell and committed cell. a. Spermatogonia A: remain undifferentiaed stem cells that are able to produce more A & B cells b. Spermatogonia B: undergo a final mitotic division to produce two cells that become *primary spermatocytes which will each enter into meiosis*

What are the phases of spermatogenesis?

1. Spermatogenesis can be divided into three phases a. Spermatocytogenesis b. Meiosis c. Spermiogenesis Note: Spermatogenesis is testosterone dependant

Describe spermatogenesis:

1. Spermatogenesis is a multi-step process of differentiation that begins with the cells lying closes to the basal lamina (spermatogonia) and ends with the release of spermatozoa into the lumen of the seminiferous tubules. 2. The process is a testosterone dependent.

What process do spermatogenic cells undergo?

1. Spermatogenic cells undergo spermatogenesis

Overview: The process of Spermatogenesis

1. Spermatogonia (Undergo spermatocytogenesis) -> Primary Spermatocytes (Undergo Meiosis I) -> Secondary Spermatocytes (Undergo Meiosis II) -> Spermatids (undergo spermiogenesis) -> Spermatozoa

Penis: Describe the sympathetic innervation of the penis

1. Sympathetic discharge accompanying ejaculation stimulates constriction of the helicine arteries *decreasing blood flow into the cavernous spaces*. 2. This alllows the veins to become uncompressed and open back up to drain blood from the penis and return to the flaccid state

Penis: The blood supply of the penis is dependent upon...

1. The blood supply of the penis depends on its functional state. It can be either *flaccid* or *erect*

Blood-Testis Barrier: Describe the structure of the blood-testis barrier

1. The blood-testis barrier: consists of a continuous belt of junctional complexes joining the Sertoli cells at their lateral surfaces—seperating the seminiferous tubule into 2 functionally different compartments. a. *Basal compartment* houses the *spermatogonia*—lies between the basal lamina and the junctional belt and is accessible to any blood-born substance that can penetrate the basal lamina b. *Adluminal compartment* extends from the junctional belt inward to the lumen. i. Inaccessible to blood-borne substances except those taken up by the supporting cells and passed through their cytoplasm.

Overview of the duct system:

1. The duct system has roles in the maturation, storage, and transport of spermatozoa. 2. All parts require adequate circulating testosterone for maintenance of normal function. 3. The secretory epithelial lining provides spermatozoa with nutrients. 4. Two complete sets of ducts (one per testis) empty into urethra.

General Features of the Male Reproductive System: Describe the external genitalia

1. The external genitalia consists of the *penis* and the *scrotum*. 2. The penis contains the most distal element of the duct system, the penile urethra. 3. The scrotum contains the testes.

General Features of the Male Reproductive System: What does the system consist of?

1. The male reproductive system consists of the external genitalia and a series of glands and ducts that produce and transport the male gametes (spermatozoa) and the seminal fluid. 2. Together the seminal fluid and spermatozoa constitute the semen.

Penis: Describe the general organization of the penis

1. The penis consists of 3 cylindrical bodies of spongy erectile tissue surrounded by a common loose connective tissue sheath. 2. Cylindrical bodies include: a. Two Corpora cavernosa b. One Corpus spongiosum 3. The penis is covered by hairless thin skin.

General Features of the Male Reproductive System: Are the testes an endocrine or exocrine gland?

1. The testes contain both endocrine and exocrine components a. Exocrine component: Seminiferous tubules b. Endocrine component: Testosterone secreting interstitial cells

Accessory genital Glands: Describe the secretion of the Seminal Vesicles

1. Thick, yellowish liquid rich in: a. Fructose b. Citrate c. Inositol d. Ostaglandins e. Several proteins 2. Secretions make up 70% of human ejaculate

Duct system: What are the major components of the intratesticular genital ducts?

1. Tubuli recti (straight tubules) a. Not located within our slide set. 2. Rete testis 3. Ductuli efferentes (efferent ductules)

General Organization of the Testes: What are the external coverings of the testes?

1. Tunica vaginalis 2. Tunica albuginea

Accessory genital Glands: Describe the Bulbourethral Glands (Cowper's glands)

Bubourethral Glands (Cowper's Glands) 1. Paired spherical tubuloalveolar glands 2. Lie within the deep perineal space 3. Lined by cuboidal epithelium 4. Ducts empty *clear lubricating mucus* into the urethra.

General Features of the Male Reproductive System: Accessory glands - Describe the bulbourethral glands and glands of Littre

Bulbourethral glands and glands of Littre: 1. Mucous glands that help to lubricate the distal part of the duct system to aid in semen transport

Three distinct histological zones of the prostate: Describe the Central zone

Central Zone: 1. Submucosal glands 2. 25% of prostate

Penis: Describe the corpora cavernosa of the penis

Corpora Cavernosa: 1. Two Dorsal erectile cylinders penetrated by a deep artery 2. *Tunica albuginea*: Thick dense connective tissue sheath that surrounds both corpora cavernosa

Intratesticular genital ducts: Describe the Ductuli efferentes (efferent ductules)

Ductuli efferentes (efferent ductules) 1. 10 to 20 short ducts connecting the rete testis with the epididymis 2. Walls contain smooth muscle 3. Epithelium has alternating groups of simple *cuboidal and ciliated columnar cells* a. Cuboidal cells absorb much of the fluid secreted by seminiferous tubules b. *Cilia sweep the spermatozoa toward the epididymis.* 4. Together the efferent ductules form the head of the epididymis a. Converge to form a single ductus epididymis

Excretory Genital Ducts: Describe the ductus deferens (vas deferens)

Ductus deferens (vas deferens): 1. Single straight tube with thick muscular walls a. Three layers of smooth muscle in the wall: inner and outer longitudinal and middle circular layers b. Capable of powerful peristaltic contractions during ejaculation 2. *Pseudostratified columnar epithelial lining has fewer stereocilia* than the epididymis. 3. Begins at the termination of the epididymis. 4. Diameters of the ductus deferens increases near the termination to form the *ampulla*, which is characterized by a highly folded mucosa. 5. Lumen is narrowed by longitudinal mucosal folds

Excretory Genital Ducts: Describe the ductus epididymis

Ductus epididymis 1. Single, highly coiled 4-6 m long tube for storage and final maturation of sperm—*spermatozoa* 2. Lined by *pseudostratified columnar epithelium with abundant apical stereocilia.* a. Secrete *glycerophosphocholine* (Possible capacitation inhibitor). b. Phagocytose and digests residual bodies sloughed during spermatogenesis 3. Sheath of circular smooth muscle underlies the basal lamina, gradually thickening along the length of the tube. a. Peristaltic contraction of this muscle propel sperm toward the ductus deferens. b. Sperm move slowly through this long coiled tube and are often seen in its lumen in tissue sections.

Excretory Genital Ducts: Describe the Ejaculatory duct

Ejaculatory duct: 1. Formed by the junction of the ductus deferens and the duct of the seminal vesicle 2. Penetrates the prostate to empty into the prostatic urethra 3. Short duct, lined by pseudostratified columnar epithelium.

Penis: Describe the blood supply of the penis during the erect state

Erect: 1. The arteriovenous shunt closes down. 2. The deep arteries in the corpora cavernosa force blood through the dilated *helicine arteries* and into the vascular space in the erectile tissue a. The sudden filling of the lacunae may block the veins draining them. b. The filled spaces compress the veins against the dense tunica albuginia, blocking outflow of the blood.

Penis: Describe the erectile tissue of the penis

Erectile Tissue 1. Within each of the cylinders is an irregularly arranged network of fibrous connective tissue trabeculae containing smooth muscle fibers. 2. The trabeculae form the supporting framework between the numerous lacuna (vascular sinuses) that are lined by endothelium.

General Features of the Male Reproductive System: Describe Excretory genital ducts

Excretory genital ducts: 1. Located outside the testes and include the: a. *Epididymis* b. *Ductus (vas) deferens* c. *Ejaculatory duct* d. *Urethra* 2. Within these larger ducts, the secretions of the testes and the accessory glands combine to form the *semen*

Penis: Describe the blood supply of the penis during the flaccid state

Flaccid: 1. Peripheral dorsal arteries in the loose connective tissue sheath supply much if the arterial blood, which is drained by the superficial veins. 2. In the flaccid state, arteriovenous shunts between the deep arteries in the corpora cavernosa and the superficial veins are open a. The *helicine arteries:* branches of the deep arteries that feed the vascular spaces b. Closed in the flaccid state

Describe the layers of walls of the seminiferous tubules from the exterior to the lumen:

From exterior to the lumen: 1. Tunica propria a. Thin layer of fibrous connective tissue containing fibroblasts b. Innermost layer includes *contractile myoid cells* 2. Well-defined basal lamina 3. Stratified seminiferous epithelium a. *Spermatogenic cells* and *Supportive Sertoli cells*

Support Cells: Describe the function of supporting (sertoli) cells

Function of supporting (Sertoli) cells: 1. Provide physical support for the spermatogenic cells 2. Nutritional regulation of the developing spermatozoa, which are isolated from the blood supply by the occluding junctions between the supporting (sertoli) cells—forming the blood-testis barrier. a. Developing spermatozoa therefore depend on these cells to mediate the exchange of nutrients and metabolites 3. Protection from autoimmune attack by immunoglobulins in the blood. 4. Phagocytosis of residual bodies shed by the maturing spermatozoa.

Support Cells: Describe the Interstitial (Leydig) cells

Interstitial (Leydig) Cells: 1. Occurs as nests of pale acidophilic cells in the loose connective tissue between the seminiferous tubules. 2. Large pale nuclei contain one or 2 prominent nucleoli 3. Cytoplasm contains the extensive SER typical of steroid-secreting cells, a well developed Gogli complex, and lipid droplets 4. *Secrete testosterone upon stimulation by pituitary LH*

Major processes of Spermiogenesis: Describe the migration of mitochondria during spermiogenesis

Migration of mitochondria: 1. Mitochondria move toward the flagellum and form a spiral collar around the proximal part of the tail (middle piece) a. Concentrating at the future site of high energy consumption. 2. The *fructose* and *citric acid* in semen aid in sperm motility, serving as mitochondrial metabolites

Three distinct histological zones of the prostate: Describe the peripheral zone

Peripheral zone: 1. Main prostatic glands a. 70% of prostate 2. Most prevalent site of *inflammation and cancer* a. 2nd most common cancer in men and 3rd leading cause of cancer deaths b. Prostate Specific Antigen (PSA) test measures blood levels of a normal glycoprotein made by the prostate which may be higher due to a prostatic tumor.

Describe the DNA/chromosomes of primary spermatocytes:

Primary Spermatocytes: 1. Primary spermatocytes replicate their DNA, so each chromosome consists of duplicate chromatids 2. Primary spermatocytes are diploid for chromosome number (46) and *tetraploid for DNA (4N)* in preparation for the first meiotic division 3. First meiotic division involves the production of two secondary spermatocytes from one primary spermatocytes

Describe the structural identifications of primary spermatocytes:

Primary spermatocytes: 1. Lie closer to the lumen than the spermatogonia 2. The largest germ cells present 3. Large round nucleus with dark strands of heterochromatin 4. Usually seen in prophase of meiosis I—longest phase of meiosis (up to 22 days)

General Features of the Male Reproductive System: Accessory glands - Describe the prostate gland secretions

Prostate gland secretions: 1. Rich in *citric acid* (another nutrient) and *acid phosphatase*

Accessory genital Glands: Describe the secretions of the prostate gland

Prostate gland: 1. Produces and secretes prostatic fluid 2. Prostatic fluid contains: a. Rich in citric acid & acid phosphatase b. Contains amylase c. Fibrinolysin d. Lipids

Accessory genital Glands: Describe the structure of the prostate gland

Prostate gland: 1. Surround the urethra at its origin below the bladder. 2. Consists of 30-50 compound tubuloalveolar glands whose ducts empty into the urethra. 3. Epithelium varies from tall cuboidal to pseudostratified columnar.

Describe secondary spermatocytes:

Secondary spermatocytes: 1. Migrate closer to the lumen than the primary spermatocytes 2. Product of the first meiotic division a. They are about half the size of the primary spermatocytes that divide to form them. 3. Rare in histologic section because they undergo the second meiotic division almost immediately after formation 4. *Haploid for chromosome number (23) and diploid for DNA (2N)* Note: Won't be able to be identified in our slide set

Describe Semen

Semen: 1. Contains fluid and sperm from the testes and secretory products from the epididymis, ductus deferens, seminal vesicles, prostate, and bulbourethral gland a. This fluid contains nutrients for spermatozoa 3. Alkaline; may help neutralize the acidic environment of urethra and vagina. 4. Also contain chemicals/hormones that protect and activate sperm.

Accessory genital Glands: Describe the structure of the Seminal Vesicles

Seminal Vesicles: 1. Paire seminal vesicles consist of highly coiled tube that develops as outgrowths of the vas deferens 2. Mucosa is highly folded 3. Pseudostratified columnar epithelium forms the secretory product 4. Smooth muscle underlying the lamina propria contracts during ejaculation. 5. In each gland, the tubes convert to form a *single duct* that joins with the *ductus deferens* of each side to form the *ejaculatory duct*

General Features of the Male Reproductive System: Accessory glands - Describe the seminal vesicles

Seminal vesicles: 1. Paired glands; secretions increase the volume of the seminal fluid and raise its pH 2. Also add *fructose*; a source of nourishment and energy for the spermatozoa

General Organization of the Testes: Describe the Septa that separates the internal testes into lobules

Septa: 1. Extensions of the tunica albuginea 2. Divide testes into about 250 compartments, or lobules.

Describe spermatids:

Spermatids: 1. Second meiotic division involves the production of spermatids from secondary spermatocytes 2. During this division the chromosome number in each cell remains haploid, but the amount of DNA is halved resulting in spermatids that are haploid for both chromosome number (23) and amount of DNA (1N) 3. Spermatids are located next to the lumen 4. Small cells with dark heterochromatic nuclei 5. May exhibit range of nuclear morphology, depending on stage of spermiogenesis. a. May or may not have long flagella depending on how much they have matured

Describe Spermatogonia:

Spermatogonia: 1. The only spermatogenic cell type present before puberty 2. Poorly differentiated; small round cells near the basal lamina 3. Round nucleus with patchy heterochromatin 4. Cells are diploid for chromosome number (46) and diploid for DNA (2N) until they are stimulated to divide. a. Spermatogonia undergo *spermatocytogenesis*

Describe spermatozoa:

Spermatozoa: 1. Located in the lumen a. In our slide set we generalize it and say that *spermatozoa are only found in the epididymus* 2. Are the end result of spermiogenesis, the differentiation of spermatids. 3. Recognizable by their long flagella 4. Haploid for both chromosome number (23) and DNA (1N) 5. Do not undergo final maturation until transported to the epididymis.

Support Cells: Describe the structure of supporting (sertoli) cells

Structure of supporting (Sertoli) cells: 1. Elongated, branched, pyramidal epithelial cells 2. Extend from the basal lamina to the luminal surface of each seminiferous tubule 3. Deep cytoplasmic infolding that embrace developing spermatogenic cells 4. Large pale nuclei are ovoid and indented and contain a prominent nucleolus 5. Well-developed SER, Golgi complex, numerous mitochondria, and some RER. 6. Margins of the cells are bound tightly to neighboring supporting cells by occluding junctions, forming a continuous sheath around the tubule lumen. a. Forming the Blood-testis barrier.

Function of supporting (sertoli) cells: What do supporting (sertoli) cells secrete?

Supporting (sertoli) cells secrete: 1. Fluid for sperm transport 2. Androgen-binding protein (ABP) a. Combine with testosterone produced by *interstitial cells* and is released into the tubule lumen 3. Inhibin: a. Acts on pituitary to decrease FSH production 4. Estrogen 5. *Anti-Mullerian Hormone*

Accessory genital Glands: What are the three distinct histological zones that the prostate is subdivided into?

Three Histological zones: 1. Peripheral zone - main prostatic gland 2. Central Zone - Submucosal glands 3. Transition Zone - Mucosal glands

Three distinct histological zones of the prostate: Describe the Transition zone

Transition Zone 1. Mucosal Glands a. 5% of prostate 2. Surround the urethra 3. Most common site of *benign prostatic hyperplasia* which occurs in men over 50 yrs old. a. Can sometimes cause obstruction of the urethra.

Intratesticular genital ducts: Describe the tubuli recti

Tubuli recti (straight tubules) 1. Connect the seminiferous tubules to the rete testis 2. Begin with epithelium similar to that of the seminiferous tubules, gradually losing the spermatogenic cells until only Sertoli cells remain. 3. Main segment lined by simple cuboid epithelium supported by a dense connective tissue sheath.

General Organization of the Testes: Describe the Tunica Vaginalis

Tunica Vaginalis 1. Double-layered mesothelial sac that covers the anterior surface of each testis 2. Extension of *peritoneum* picked up during the descent of testes through the inguinal canal and into the scrotum 3. The visceral layer is continuous with the tunica albuginea on the anterior and lateral sides, but is absent on the posterior surface where the epididymis exits the testes.