Lesson 1, Topic 1
In Progress

Anatomy of the Male Reproductive System

April 11, 2024

Learning Objective: Examine the anatomy of the male reproductive system.
      The male reproductive system is responsible for producing, transporting, and sustaining sperm cells. The sperm cells are called sex cells or gametes. A sperm cell contributes half of the genes of the new offspring. The gametes are produced in organs called gonads. Gonads are considered primary or essential sex organs. They are also responsible for producing hormones. The other organs in the reproductive system are secondary or accessory organs.

Testis
Learning Objective: Describe the testis, including the location and the role in the male reproductive system.
      The primary reproductive organs in the male are the testes. Each testis is oval and measures about 1.6 inches (4 cm) long and 1 inch (2.5 cm) wide. The testes are surrounded by a white, fibrous capsule and are suspended together in a sac outside the body called the scrotum. Testes produce the gametes called spermatozoa. Spermatozoa are made up of three parts (FIGURE 27.14):
                • Head: Contains the chromosomes in the nucleus; the acrosome covers the head of the sperm and contains enzymes to help penetrate the ovum.
                • Midpiece: Contains mitochondria, which produce energy for movement.
                • Tail or flagellum: Used for movement.

Spermatogenesis
Learning Objective: Describe spermatogenesis and the structures involved.
    The formation of sperm is called spermatogenesis. The spermatozoa are formed in a series of tightly coiled tiny tubes in each testis called the seminiferous tubules. From the seminiferous tubules, the formed spermatozoa travel to the epididymis, where they mature and are stored. The epididymis is a coiled tube almost 20 feet (6 meters) long and rests on top of and behind each testis.

FIGURE 27.14  Sperm.

From the epididymis, the spermatozoa move into the vas deferens or ductus deferens (FIGURE 27.15). Each vas deferens is a muscular tunnel about 18 inches (45 cm) long that connects to the base of the epididymis and passes along the side of the testis. The vas deferens travels into the pelvic cavity to just behind the bladder. Spermatozoa can stay in the vasa deferentia for several months in an inactive state.
      The prostate gland is the size of a walnut and is found below the bladder in males. It surrounds part of the urethra. The prostate is considered a reproductive organ but it also affects the urinary system. When the prostate increases in size (as with benign prostatic hyperplasia [BPH]), it can obstruct the urethra, blocking the urine flow.
     The prostate gland, seminal vesicles, and Cowper glands (or bulbourethral glands) provide fluid either to nourish or aid in motility and lubrication. The sperm and the fluid together make up a substance called semen. The ejaculatory duct begins where the seminal vesicles join the vas deferens, and this “tube” joins the urethra.


27.8 Critical Thinking Application
To review the anatomy of the male reproductive system, Hannah is writing down the process of spermatogenesis, including all the structures needed from the formation of the sperm until it leaves the body in semen. Can you do the same?


Urethra and Penis
Learning Objective: Describe the structures of the penis.
      The urethra is found within the penis and transports the semen to the outside of the body. The urethra also transports urine to the outside of the body.
      The body is the shaft of the penis. The penis is composed of three columns of highly vascular erectile tissue. There are two columns of corpora cavernosa and one of corpus spongiosum that fill with blood through the dorsal veins during sexual arousal. During ejaculation, the sperm exit through the glans penis, the tip of the penis. At birth, the glans penis is surrounded by a fold of skin called the prepuce or foreskin, which can be removed by circumcision.