Male Reproductive System Overview

Study Notes

The male reproductive system is comprised of testes, duct system, glands, and external genitalia.
The testes are egg-shaped structures located in the scrotum.
The testes contain seminiferous tubules where spermatogenesis (sperm production) takes place.
The epididymis is the first part of the duct system, where sperm mature and are stored.
The ductus deferens (vas deferens) stores sperm and contracts to propel semen.
The ejaculatory duct merges the vas deferens and seminal vesicle, emptying into the urethra.
The urethra carries urine and semen out of the body.
The accessory glands (seminal vesicles, prostate, and bulbourethral glands) produce fluids that mix with sperm to form semen.
The scrotum and penis are external genitalia, involved in temperature regulation and sperm delivery.

Spermatogenesis is the process of sperm development within the seminiferous tubules.
It has four stages: spermatogonia (stem cells), spermatocytes (undergo meiosis), spermatids, and spermatozoa (sperm).
Spermatogenesis takes place within the walls of the seminiferous tubules.
Spermatozoa are motile and mature sperm. They have parts including a tail, a middle piece, and a head.

Sertoli cells support sperm development by providing nutrients and chemical stimuli.
They're stimulated by follicle-stimulating hormone (FSH).
These cells form a blood-testis barrier. This barrier is necessary to protect sperm from the body's immune system which could otherwise recognize them as foreign cells and attack them.

Leydig cells are located in the interstitial tissue surrounding the seminiferous tubules.
They produce testosterone, and this hormone is stimulated by luteinizing hormone (LH).
Testosterone influences spermatogenesis, promotes libido, and helps maintain male secondary sex characteristics and organs of reproduction.

FSH stimulates Sertoli cells.
LH stimulates Leydig cells to produce testosterone.
Testosterone in turn promotes spermatogenesis, libido, and male secondary sex characteristics.

The epididymis is the first part of the duct system, storing and maturing sperm.
The ductus deferens (vas deferens) is responsible for storing sperm for several months.
The ductus deferens' smooth muscle propels semen.
The ductus deferens is part of the spermatic cord, encased by structures such as the cremasteric muscle and fascia.
The spermatic cord encloses associated structures near the testes.

The epididymis is the initial part of the duct system, and is involved in sperm storage and maturation.
It protects sperm, and damaged spermatozoa are recycled.
Sperm leaving the epididymis are still immature.

The ejaculatory duct is formed from the convergence of the vas deferens and seminal vesicle.
It extends through the prostate, and then empties into the urethra.

The urethra carries urine and semen out of the body.
A portion of the urethra passes through the prostate, and then through the penis to exit.

The penis is an external structure.
The penis releases urine and semen. Erection is a result of blood flow to the erectile tissue in the penis.
The scrotum is a pouch-like structure holding the testes, and plays an important role in temperature regulation.
The cremaster muscles and dartos muscles of the scrotum are involved in temperature regulation.

Erection, emission, and ejaculation are the coordinated events making up the male sex response.
Erection depends on increased blood flow to the penis (parasympathetic nervous system).
Emission involves the movement of semen into the urethra (sympathetic nervous system).
Ejaculation pushes semen out of the body (somatic nervous system).