REPRODUCTION SYSTEM - TESTES

What is a gonad?

Testes (sperm + testosterone production)

Where are ducts in the reproductive system of those with testes?

Epididymis, vas deferens, ejaculatory duct, urethra

What structures an accessory sex glands?

Seminal vesicles, prostate, bulbourethral glands

What structures an external genitalia?

Penis, scrotum

What are the functions of the vas deferens?

Propels sperm from epididymis toward urethra via peristalsis; travels in spermatic cord through inguinal cord

Where is the ejaculator duct?

Formed by vas deferens + seminal vesicle duct; located inside the prostate; opens in urethra

What problems are associated with enlargement of the prostate with age?

Compresses urethra → weak stream, urinary retention, frequency

Describe the function of the bulbourethral gland prior to ejaculation?

Secretes alkaline mucus before ejaculation→ neutralizes acidic urine in urethra, lubricates urethra for sperm passage

What is the pathway of sperm through the reproductive ducts

testes > epididymis > vas deferens > ejaculatory duct > urethra

How does blood flow into the penis produce an erection? What regulates this?

Parasympathetic stimulation → release NO → relaxes smooth muscle in penile arterioles → ↑ blood flow into corpora cavernosa → compression of venous outflow → erection maintained

Which preventable risk factor is associated with erectile dysfunction?

Smoking, obesity, diabetes, physical inactivity, hypertension, excess alcohol

What variables affect blood flow to the penis?

Arterial diameter, blood viscosity, systemic BP, endothelial nitrogen oxide availability, venous outflow resistance

Describe the function of the scrotum

Holds testes 2-3°C below core body temp (optimal for spermatogenesis `35°C)

Explain how counter-current blood flow in the scrotum keeps the testes cool

Counter-current heat exchange

What is the function of the cremaster?

elevates/lowers testes toward/away from body to regulate temperature

What is the function of dartos muscles?

Wrinkles scrotal skin to reduce surface area (cold) or relaxes to increase surface area (warm) → both are thermoregulatory

Describe the functions of the interstitial cells (leydig cells)

Produce testosterone in response to LH

Describe the functions of sertoli cells (sustentacular/nurse)

Nourish & support developing sperm, secrete inhibin, from blood-testes barrier, respond to FSH

Describe the function of spermatogonia

Stem cells lining seminiferous tubules; divide by mitosis then enter meiosis to become sperm

Describe meiosis of a spermatogonium.

Spermatogonium (2n) → mitosis → primary spermatocyte (2n) → meiosis I → 2 secondary spermatocytes (n) → meiosis II → 4 spermatids (n) → spermiogenesis (maturation) → 4 mature sperm

How many mature sperm cells can be made from 1 spermatogonium that begins meiosis?

1 spermatogonium = 4 mature sperm (all functional, unlike oogenesis)

Describe the function of these parts of a sperm: mid-piece

Packed with mitochondria → ATP for motility

Describe the function of these parts of a sperm: head

Contains haploid nucleus

Describe the function of these parts of a sperm: acrosome

Cap over nucleus; contains enzymes to penetrate egg

Describe the function of these parts of a sperm: flagellum

Propels sperm; powered by mid-piece ATP

What damages sperm DNA?

Heat, radiation, ROS (reactive oxygen species), smoking, alcohol, toxins

What maturation event from sperm occurs in epididymis?

Sperm gain motility (learn to swim) and ability to fertilize egg - they are non-functional when they leave the testes

Which hormones are important for sperm production? Which glands produce each hormone?

GnRH (hypothalamus), FSH & LH (anterior pituitary), testosterone (leydig cells), inhibin (sertoli cells)

What is the function of GnRH?

Stimulates anterior pituitary to release FSH + LH

What is the function of FSH?

Stimulates sertoli cells → support spermatogenesis

What is the function of LH

Stimulates leydig cells → produces testosterone

Stimulates leydig cells → produces testosterone

Negative feedback loop → inhibits FSH when sperm count is high

What is sex?

Biology attributes - exists on a spectrum, not strictly binary, influenced by genetics, hormones, development

What is gender?

Internal identity + social role - distinct from biological sex, influenced by culture

What are the functions of the wolffian ducts?

Develop into male reproductive ducts when testosterone is present; degenerate in females

What are the functions of mullerian ducts?

Develop into fallopian tubules, uterus, upper vagina when MIF is absent; degeneral in males