Overview
This lab focuses on male-specific muscles associated with the testes, their anatomy, development, and function, including how they regulate temperature for optimal sperm production.
Anatomy of the Testes and Associated Structures
- The testes are housed in the scrotum, a skin pouch located behind and below the penis.
- Each testis is surrounded by the epididymis (C-shaped structure) and attached to the spermatic cord.
- The spermatic cord contains arteries, veins, nerves, and the vas (ductus) deferens, which transports sperm to the prostate.
- The vas deferens is cut during a vasectomy (male sterilization).
Embryological Development and Descent
- Gonads develop near the kidneys and descend into the pelvis; testes move further into the scrotum in males.
- Testes travel through the inguinal canal, dragging blood vessels, nerves, and muscle fibers along.
- Problems with descent can lead to cryptorchidism (undescended testicle), increasing the risk of cancer, infertility, and testicular torsion.
Temperature Regulation and Muscle Function
- Sperm production requires temperatures 2–4°C below core body temperature.
- Testes hang outside the body in the scrotum to maintain a cooler temperature.
Cremaster Muscle
- The cremaster muscle is derived from the internal oblique muscle (skeletal, voluntary control).
- This muscle raises and lowers the testes in response to temperature or conscious effort.
- Reflexive contraction typically occurs due to cold, pulling testes closer for warmth.
Dartos Muscle
- The dartos muscle is smooth muscle within the subcutaneous layer of the scrotum (involuntary control).
- Contraction tightens the scrotal skin, reducing heat loss in cold conditions.
- Relaxation loosens the skin, allowing heat dissipation when warm.
Cremaster Reflex Test
- Stroking the inner thigh triggers the cremaster muscle to contract, elevating the testis on that side.
- Absence of this reflex can help diagnose testicular torsion in clinical settings.
Key Terms & Definitions
- Testes/Testicles — Male reproductive organs producing sperm and testosterone.
- Scrotum — External skin pouch housing the testes.
- Spermatic cord — Bundle containing blood vessels, nerves, and vas deferens.
- Vas (ductus) deferens — Tube carrying sperm from testes to prostate.
- Cryptorchidism — Condition of undescended testicle(s).
- Cremaster muscle — Skeletal muscle elevating and lowering the testes.
- Dartos muscle — Smooth muscle tightening or relaxing the scrotal skin.
- Cremaster reflex — Involuntary elevation of the testis after stroking the inner thigh.
Action Items / Next Steps
- Review the anatomy and function of the cremaster and dartos muscles.
- Practice identifying these structures and their roles in temperature regulation.
- Prepare for possible lab demonstration of the cremaster reflex test.