Lecture 1 – Reproductive Tract of Males

where do the testes originate in the embryo, and what is the name of the key cord of tissue that guides their descent?

• they originate from the gonadal ridges in the upper lumbar region

• the key cord is the gubernaculum

explain the ‘relative shortening’ theory of how the gubernaculum helps the testes descend

• gubernaculum doesn’t elongate as the fetus grows

this fixed length effectively shortens relative to the body, pulling the testes downwards through the inguinal canal into the scrotum

what is cryptorchidism, and what is its most significant consequence for male reproduction?

• cryptorchidism is the failure of one or both testes to descend into the scrotum

consequence: endocrine function remains intact, but spermatogenesis is arrested due to the abdomen’s temperature being too high

name the three specific mechanisms the scrotum uses to maintain a temperature 4–7°C lower than the body

• high density of sweat glands for evaporative cooling

• spermatic artery is coiled in close proximity to the spermatic cord and the venous blood supply which is returning cooled peripheral blood to the heart

  • contracts in cold (pulls testes up) and relaxes in warmth (lets them hang low)

what’s the tough, fibrous capsule that encases the testis called?

• the tunica albuginea

  • composed of collagen and elastic fibres

  • provides high tensile strength and elasticity

name the major glands of the male reproductive system

• seminal vesicles

  • located behind the bladder

  • produces the fluid that makes up semen, rich in fructose for energy, prostaglandins for motility, and nutrients for sperm survival

• prostate gland

  • small, walnut-sized gland

  • located below the bladder and surrounding the urethra

  • produces alkaline fluid that nourishes, protects, and transports sperm

• bulbourethral glands (Cowper’s glands)

  • two small, pea-sized exocrine glands

  • located beneath the prostate gland

  • functions during arousal to secrete an alkaline, mucous-rich fluid lubricating the urethra and neutralises acidic urine residue

what’s the specific site of sperm production within the testis, and how many of these structures are there per testis?

• the seminiferous tubules

  • highly coiled tubes located within the testes responsible for spermatogenesis and supporting male reproductive cells through Sertoli cells

    • ~800 per testis

    • each seminiferous tubules are ~80 cm long`

explain the ‘spermatogenic wave’

why does the testis use this mechanism?

spermatogenesis takes a fixed time with a new cycle every 16 days.

• the wave means different segments along a single seminiferous tubule are at different stages of development

  • this ensures a continuous supply of mature sperm is always being produces and released

what’s the primary function of the epididymis, and how long do sperm spend there?

primary function is sperm maturation (not long-term storage)

• sperm spends ~12 days transiting the epididymis

match the three regions of the epididymis with their key characteristics:

1. head (caput)

2. body (corpus)

3. tail (cauda)

• head (caput) – receives sperm, lined with stereocilia that absorbs fluid (concentrates sperm 100x). sperm is immotile

• body (corpus) – tubule becomes less convoluted; fluid continues to decrease

• tail (cauda) – muscular wall thickens. sperm are motile & fertile but kept quiescent until ejaculation

what are the muscular wall of the vas deferens?

thick, comprising of three distinct layers of smooth muscle that facilitates rapid sperm transport via peristalsis during ejaculation:

• inner longitudinal layer

• middle circular layer

• outer longitudinal layer

what’s the major site of sperm storage in men? describe its structure

• the vas deferens

  • muscular tubule ~45 cm long with three muscular layers

  • the lumen becomes folded and enlarged near the prostate to form the ampulla (additional storage)

what’s the clinical significance of congenital absence of the vas deferens?

it affects ~1 in 1000 men and accounts for 1–2% of male infertility

most commonly found in men with cystic fibrosis due to genetic mutations

what ultimately happens to sperm that aren’t ejaculated?

they’re broken down and reabsorbed by the body or are lost in the urine