Untitled Notes

Identify the structures and functions of the male external genitalia and internal genitalia.
Outline fetal descent of the testes and describe the structures related to the scrotum and testes.
Summarize the events of spermatogenesis and describe the functional anatomy of a mature sperm.
Explain meiosis and early spermiogenesis within the seminiferous tubules.
Explain the roles played by the male reproductive tract and accessory glands in the functional maturation, nourishment, storage, and transport of sperm.
Describe the structure and function of the penis.
Explain the roles of testosterone and other regulatory hormones in establishing and maintaining male sexual function.

Scrotal cavities: Two compartments that house one testis each.
Scrotal septum: A partition that divides the left and right scrotal cavities.
Raphe of scrotum: A raised, seam-like line on the scrotum's surface.
Dartos muscle: A muscle that wrinkles the scrotal surface and elevates the testes.
Cremaster muscle: Contracts to pull the testes closer to the body during heat or cold.
Spermatic cords: Connect testes to abdominopelvic cavity, containing blood vessels, nerves, and ductus deferens.
Superficial inguinal ring: The entrance to the inguinal canal.
Inguinal canal: Extends from the inguinal ring to the scrotal cavity; potential site for inguinal hernias.

Tunica vaginalis: A serous membrane that lines the scrotal cavity, reducing friction.
Tunica albuginea: A tough, fibrous capsule covering each testis; continuous with septa that divide the testes into lobules.
Seminiferous tubules: Coiled structures within the lobules, the actual sites of sperm production.
Rete testis: A network where seminiferous tubules merge into straight tubules.
Efferent ductules: Tubes connecting the rete testis to the epididymis.

Mitosis of Spermatogonium:
- Stem cells located in seminiferous tubules.
- Result: Two daughter cells, each diploid (23 pairs of chromosomes).
- One cell remains in contact with the basement membrane; the other becomes a primary spermatocyte.
- Duration: Approximately 16 days to progress to primary spermatocyte.
Meiosis (Two Cycles):
- Meiosis I:
  - Begins with a primary spermatocyte (diploid).
  - Daughter cells produced: secondary spermatocytes (haploid, each with 23 chromosomes).
  - Each chromosome consists of two sister chromatids.
  - Duration: About 24 days to secondary spermatocyte.
- Meiosis II:
  - Each secondary spermatocyte divides to produce spermatids.
  - Meiosis II yields four haploid spermatids; duration only a few hours.
Spermiogenesis:
- The final maturation of spermatids into spermatozoa.
- Each spermatid matures into a single sperm cell; duration: approximately 24 days from spermatid to mature sperm.

Specialized for delivering chromosomes to the female gamete.
Lacks most organelles to maximize efficiency.
Acrosome: A membranous compartment containing enzymes important for fertilization.
Head: Contains the nucleus that carries genetic information.
Neck: Connects the head to the middle piece.
Middle Piece: Contains mitochondria to generate ATP, necessary for sperm motility.
Tail (Flagellum): A whip-like organelle that propels the sperm.

Characteristics: Tightly coiled structures where spermatogenesis occurs; spermatogenic processes together take approximately 9 weeks.
Each segment of the tubule is at a different phase of spermatogenesis.
Interstitial spaces contain:
- Areolar tissue
- Blood vessels
- Large Leydig cells (interstitial endocrine cells) producing androgens like testosterone and androstenedione (dominant male hormones).

Path of Sperm: Sperm travels from the testis to the epididymis, along the ductus deferens, then through the ejaculatory duct to the urethra.
Accessory Glands:
- Seminal glands, prostate, and bulbo-urethral glands secrete fluids into the reproductive tract.
Urethra: Passes through the penis to exit the body for sperm delivery and urine excretion.

Types of cells:
- Spermatogonia (stem cells)
- Spermatocytes (developing cells undergoing meiosis)
- Spermatids (undergoing spermiogenesis)
- Nurse Cells (Sertoli Cells): Extend from the tubular capsule to the lumen; surround and support developing spermatogenic cells.
Spermiation: The process where a spermatozoon detaches from nurse cells and enters the tubule lumen.

Sperm released from the testes are mature but immobile and incapable of fertilization.
Capacitation: A two-step process enabling sperm to become motile and capable of fertilization:
1. Sperm mix with seminal gland secretions becoming motile.
2. Sperm become capable of fertilization when exposed to the female reproductive tract.

The initial segment of the male reproductive tract; coiled tube attached to the posterior of each testis.
Lined with pseudostratified columnar epithelium with long stereocilia to increase surface area for absorption and secretion.
Regions of Epididymis:
- Head: Receives sperm from efferent ductules.
- Body: Middle region.
- Tail: Segment near the testis's inferior border, where the number of coils decreases.

Length: 40-45 cm; transports sperm from epididymis and can store sperm for several months.
Ampulla: The expanded distal portion of the ductus deferens.
Ejaculatory Duct: Carries fluids from the seminal gland and ampulla to the urethra.

Located at the base of the penis; secrete thick, alkaline mucus to neutralize urethral acid and lubricate the tip of the penis.

Root: The part that attaches to the body.
Body (Shaft): The long cylindrical part.
Glans Penis (Head): The sensitive tip of the penis.
Neck of Glans: Area surrounding the glans.
Foreskin (Prepuce): A fold of skin surrounding the glans; secretes smegma—a waxy material.

In resting state, the arteries are constricted, restricting blood flow into the erectile tissue.
Corpora Cavernosa: Two columns of erectile tissue.
Corpus Spongiosum: Surrounds the penile urethra; expands at the tip to form the glans.
Other Tissue Layers:
- Outer skin: Has smooth muscle and elastic tissue allowing movement.