HISTO Lec Chap 12 : Male Reproductive System

MTY1208 Lab and Lec

EXTERNAL GENITALIA

• PENIS

• TESTES suspended in a fibroelastic sac, the SCROTUM

EXCRETORY DUCTS OF THE TESTES

• Tubuli Recti

• Rete Testis

• Ductuli Efferentes

• Ductus Epididymis

• Ductus Deferens

ACCESSORY GLANDS

• Seminal Vesicles

• Prostate

• Bulbourethral Glands

TESTES

• Ovoid, 4-5 cm x 2.5 cm

• Average weight of 14 g each

• Develop early in embryonic life within the abdominal cavity

• Later descend into the scrotum, each carrying an outpocketing of the peritoneum, the tunica vaginalis testis

• Both exocrine and endocrine

  • EXOCRINE : production of spermatozoa

    • Sperm cells

  • ENDOCRINE : synthesis of testosterone

Exocrine Portion of Testes

• Responsible for the production and transport of sperm.

• Consists of seminiferous tubules, where spermatogenesis (sperm production) occurs.

• Lined with Sertoli cells, which support and nourish developing sperm cells, and germ cells that undergo meiosis to form sperm.

• The sperm produced in the seminiferous tubules is transported through the rete testis, then into the efferent ducts and epididymis for maturation and storage.

• This portion is involved in the spermatogenic process and the initial stages of sperm maturation.

Endocrine Portion of Testes

• Responsible for the production of testosterone and other hormones.

• Located in the interstitial space between the seminiferous tubules, it contains Leydig cells.

• Leydig cells secrete testosterone in response to luteinizing hormone (LH) from the pituitary gland.

• Testosterone plays a crucial role in the development of male secondary sexual characteristics, such as facial hair, deep voice, and muscle mass.

• The endocrine portion also supports spermatogenesis indirectly by regulating the function of Sertoli cells within the seminiferous tubules.

TESTOSTERONE

• Synthesized  by interstitial cells of Leydig which are found in the interstitium in between seminiferous tubules 

• Production of testosterone depends on the luteinizing hormone (LH) secreted by the anterior pituitary gland

  • Secretion of LH surges during puberty

FUNCTIONS OF TESTOSTERONE

• To sustain spermatogenesis in the seminiferous tubules

• Maintenance of the function of the accessory glands of male reproduction : 

  • Seminal Vesicles

  • Prostate

  • Bulbourethral Glands

• Maintenance of the male secondary characteristics

  • Male pattern of pubic hair 

  • Growth of beard

  • Low-pitched voice

  • Muscular body build

Tunica Vaginalis Testis, Tunica Albuginea

COVERING OF THE TESTIS

TUNICA VAGINALIS TESTIS

• Forms an independent serous cavity surrounding the testis.

• The visceral layer is tightly adherent to the capsule of the testis, known as the tunica albuginea.

• Separated by a narrow cavity from the outer parietal layer of the tunica vaginalis.

• Provides a lubricating fluid to reduce friction between the testis and the scrotum during movement.

• Helps in maintaining the testis' position and movement within the scrotum.

TUNICA ALBUGINEA

• A thick fibrous capsule that encloses the testis.

• Forms fibrous partitions (septae) that extend inward, dividing the testis into approximately 250 pyramidal compartments, known as lobuli testis.

• Each lobule contains 1-4 seminiferous tubules, where spermatogenesis (sperm production) takes place.

• Provides structural support and protection to the internal testicular structures.

• Serves as the connective tissue framework that organizes the testis into functional units for sperm production.

SEMINIFEROUS TUBULES

• 30-70 cm long and 150-250 u in diameter

• Extremely tortuous, majority forms highly convoluted loops

• Lined by complex stratified epithelium containing spermatogenic cells (Germ cells) and supporting cells (Sertoli cells)

Spermatogenic Cells

• Germ cells that proliferate near the base and slowly move upward toward free surface as they differentiate into spermatozoa

• The precursor cells responsible for the production of sperm in the testes.

• Located within the seminiferous tubules, they undergo a series of developmental stages to form mature sperm cells.

• Includes several stages: spermatogonia (stem cells), primary spermatocytes, secondary spermatocytes, spermatids, and finally, spermatozoa.

• Spermatogonia divide mitotically to produce primary spermatocytes, which undergo meiosis to form haploid spermatids.

• Spermatids undergo spermiogenesis, a process where they develop into mature sperm cells (spermatozoa), acquiring a tail for motility.

• Supported and nourished by Sertoli cells throughout their development in the seminiferous tubules.

Sertoli Cells

• These are somatic cells located within the seminiferous tubules of the testes.

• Act as nurse cells, providing structural support and nourishment to developing spermatogenic cells (sperm cells).

• Facilitate spermatogenesis by creating a blood-testis barrier and secreting inhibin, which regulates FSH secretion.

• Maintain the seminiferous tubule environment by phagocytosing excess cytoplasm during sperm development.

• Secrete androgen-binding protein (ABP) to maintain high local concentrations of testosterone, which is essential for sperm production.

SPERMATOZOA

• These are the mature, motile sperm cells produced at the end of spermatogenesis.

• Characterized by a head, midpiece, and tail:

  • The head contains the nucleus with haploid DNA, responsible for fertilization.

  • The midpiece contains mitochondria that provide energy for motility.

  • The tail (flagellum) enables movement through the female reproductive tract.

• Developed from spermatids after undergoing spermiogenesis, where they gain their distinctive shape and function.

• Stored in the epididymis for maturation and later ejaculation.

• Essential for fertilizing an egg during reproduction.

HEAD OF SPERMATOZOA

• Ovoid or pyriform, tapered toward the tip 

• Consist of the condensed nucleus that contains the genetic traits that the father transmit to offsprings

• Anterior part covered by acrosome 

  • A membrane-bound cap-like organelle containing enzymes

TAIL OF SPERMATOZOA

• Provides the motility necessary to transport sperm cells to site of fertilization and in penetration of the coatings of the ovum

• Core is made up of axonemes

Axonemes

• Core structural components of cilia and flagella, including the sperm tail.

• Composed of a 9+2 arrangement of microtubules: nine outer doublet microtubules surrounding two central single microtubules.

• Provide the structural foundation that allows for the movement of cilia and flagella through dynein motors that produce bending forces.

• In sperm, the axoneme is crucial for the motility of the tail, enabling the sperm to swim towards the egg for fertilization.

• Ensures the proper flexibility and propulsion necessary for sperm to navigate the female reproductive tract.

Tubuli Recti, Rete Testis, Ductuli Efferentes

Ducts of the Male Reproductive System

Tubuli Recti

• Short straight duct that arise from each pyramidal lobule which converge on the rete

• These are straight tubules located at the junction between the seminiferous tubules and the rete testis.

• They serve as the pathway for sperm cells to move from the seminiferous tubules to the rete testis for further transportation to the epididymis.

• Lined with a combination of Sertoli cells and cuboidal epithelium.

• Function to transport immature sperm and fluid from the seminiferous tubules towards the rete testis, where sperm continue their maturation process.

• Act as a conduit in the early stages of sperm transport within the testicular system.

Rete Testis

• A plexus of epithelium-lined spaces located in the mediastinum testis.

• Functions as a network for collecting sperm from the tubuli recti and transporting it to the efferent ductules.

• Lined with cuboidal to columnar epithelium and contains stereocilia, which aid in the absorption of fluid from the sperm.

• Acts as a conduit for sperm before they move into the epididymis for further maturation.

• Helps in the concentration of sperm by reabsorbing excess fluid, making the sperm more concentrated as they move towards the efferent ductules.

Ductuli Efferentes

• Series of 12 or more small ducts that arise from the rete testis.

• They traverse the tunica albuginea and emerge at the postero-superior portion of the testis.

• These ducts become confluent with the ductus epididymis, forming the epididymal duct.

• Function to transport immature sperm from the rete testis to the epididymis for further maturation.

• Lined with ciliated epithelium that helps propel sperm and non-ciliated cells that assist in fluid absorption.

EPIDIDYMIS

• Highly convoluted ; 4-5 m long

• Runs along the posterior surface of the testis from its upper to its lower pole with stereocilia

• Duct lined by pseudostratified columnar epithelium 

• Site of accumulation, maturation, and storage of spermatozoa

DUCTUS DEFERENS ( VAS DEFERENS )

• The distal end of the epididymis straightens out to form this structure, which ascends within the spermatic cord.

• Travels through the inguinal canal and joins the ejaculatory duct in the pelvic cavity.

• This structure, along with the spermatic artery, nerves, and veins, forms the spermatic cord.

• Serves as the pathway for sperm during ejaculation, transporting sperm from the epididymis to the urethra.

• The duct is commonly cut during a vasectomy, a procedure for male sterilization, preventing sperm from entering the ejaculate.

EJACULATORY DUCT

• This structure is formed by the union of the ductus deferens and the ducts of the seminal vesicles.

• It passes through the prostate gland and opens into the posterior wall of the prostatic urethra.

• Serves as the passageway for sperm and seminal fluid during ejaculation.

• It facilitates the mixing of sperm with seminal fluid from the seminal vesicles, contributing to the formation of semen.

SEMINAL VESICLE

• Pair of diverging saccular structures about 5 cm in length

• Located behind the neck of the urinary bladder above the prostate gland

• Coiled or convoluted tubes

• Produce secretions that contribute to the greater volume of the ejaculate

• Produces seminal fluid

  • Made up of fructose

PROSTATE GLAND

• The largest of the accessory glands weighing 20 grams

• Its secretion together with seminal vesicles contribute to the ejaculate

• Encircles the neck of the urinary bladder and the urethra

• Compound tubuloacinar glands surrounded with fibromuscular tissue

• Spherical bodies called corpora amylacea are often found in the lumen of these glands

• Releases acid phosphatase 

• Diagnostic tool used for the forensic investigation of rape

BULBOURETHRAL GLAND

• Paired glands measuring less than 1 cm in diameter, located in the urogenital diaphragm below the prostate.

• Secrete a clear, mucus-like, viscous fluid that acts as a lubricant.

• The secretion helps to neutralize acidic urine residues in the urethra and provides lubrication for sexual activity.

• Opens into the penile urethra, facilitating the secretion’s release during ejaculation.

• Commonly referred to as Cowper’s glands, these are important in preparing the urethra for the passage of sperm during ejaculation.

PENIS

Consist of 3 cylindrical bodies : 

• 2 Corpora Cavernosa which consist of cavernous erectile tissue

• The unpaired Corpus Spongiosum (corpus cavernosum urethrae)

• Forms the shaft of penis, surrounded by a thick fibrous capsule, tunica albuginea, covered by skin

CORPORA CAVERNOSA

• Form the dorsal two-thirds of the shaft of the penis.

• Composed of erectile tissue with a sponge-like structure of irregularly shaped vascular spaces.

• These spaces fill with blood during sexual arousal, causing the penis to become rigid and erect.

• Play a key role in achieving erection by accommodating blood flow during sexual stimulation.

• Surrounded by a fibrous capsule (tunica albuginea) that helps maintain rigidity.

CORPORA SPONGIOSUM

• Occupy a shallow groove between the lower surface of the corpora cavernosa.

• Contains the penile urethra, which runs longitudinally through it.

• The urethra ends in the meatus at the glans penis.

• Functions to prevent urethral compression during erection, allowing for the passage of urine and semen.

• The tissue is less rigid than the corpora cavernosa, allowing for the expansion of the urethra during erection.

GLANS PENIS

• Composed of dense connective tissue containing a plexus of large anastomosing veins.

• Features both circular and longitudinal smooth muscle fibers in the walls of these veins.

• The veins in the glans play a role in maintaining erection by trapping blood within the area.

• Highly sensitive, contributing to sexual pleasure and stimulation during intercourse.

• It forms the distal end of the penis, with the urethral meatus at its tip.

PREPUCE

• The skin covering the glans penis.

• Composed of thin skin with a subcutaneous layer containing smooth muscles.

• Lacks adipose tissue, which distinguishes it from other skin areas.

• This structure is folded and forms the foreskin, which can be retracted to expose the glans.

• The smooth muscles allow for movement and retraction of the foreskin, contributing to sexual function and protection of the glans.