Module 3 Lesson 1 - 2
Lesson 1 — The Human Male Reproductive System
The Anatomy of the Male Reproductive System
Read pages 478 - 481
Your own reproductive health is important not only to you but to your future partner, also. Therefore, both males and females must understand the structure (anatomy) and function (physiology) of the male reproductive system, including its primary reproductive organs, ducts, and accessory glands.
Reproduction ensures the continuity and survival of the species. The reproductive system is different from other body systems in that it becomes functional at the time of puberty under the influence of hormones. Reproduction accounts for the major differences between males and females, and it serves more than the individual by perpetuating the species. Several factors have led to increased survival rates of offspring in vertebrates. Internal fertilization resulted in protection of the developing embryo. Producing fewer eggs also meant that offspring could be nurtured for longer periods after birth.
The male reproductive system has three major functions:
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to produce sperm (gamete - sex cells)
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to release hormones (androgens)
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to deposit sperm into the female reproductive system
Structures and Functions of the Male Reproductive System
A sperm cell is the smallest human cell. The female gamete, the egg, is about 85 000 times larger than a sperm cell is. The difference between the size of the sperm and the egg is due to the amount of cytoplasm within each cell.
Each sperm has half the genetic material (23 chromosomes) necessary for reproduction. A normal somatic (body) cell has 46 chromosomes. From 200 to 400 million sperm are released in one ejaculation. However, only one sperm can fertilize an egg. Each sperm has a tail (flagellum) that it uses to mobilize itself for fertilization.
The sperm are produced in the seminiferous tubules inside the testes, which are paired organs. The sack that holds the testes is called the scrotum.
The ideal temperature for producing sperm is 3°C below body temperature. Therefore, the testes are outside the body to control the temperature of the developing sperm. In a cold environment, the scrotum muscles contract, pulling the testes closer to the body and decreasing their surface area. In a warm environment, the scrotum muscles extend, lowering the testes away from the body and increasing their surface area.
The sperm takes about 64 to 72 days to develop in the seminiferous tubules and another 10 to 14 days to mature and become mobile in the epididymis, a coiled tube that sits on top of the testis.
Sperm leave the testes through the vas deferens. The surgical procedure called vasectomy is performed by cutting and sealing a section of the vas deferens. The vasectomy blocks the pathway of the sperm, thus preventing it from leaving the testis. This is an effective form of birth control to prevent conception.
As the sperm exit the testes through the vas deferens, the sperm is mixed with seminal fluid from the accessory glands. Seminal fluid is alkaline (basic) to protect the sperm and counteract the acidic environments. Acidic conditions are present in two places: the urethra through which urine and sperm pass, and the female vagina. Seminal fluid contains food for sperm so that they can survive for 2 to 3 days. Typically, sperm can survive at normal body temperature for 24 to 72 hours.
The three accessory glands that produce the seminal fluids are the seminal vesicles, the prostate gland, and the Cowper’s gland. The seminal vesicles produces yellowish fluid, which is rich in nutrients, including fructose, to sustain sperm.
The prostate
gland and Cowper's gland secrete mucus and alkaline fluid to neutralize the acidic environments of the urethra and the vagina, and to act as a lubricant prior to ejaculation. Thus, semen is a mixture of various components, all designed
to protect and nurture the sperm it carries.
Sperm Pathway
Sperm do not enter the accessory glands (seminal vesicles, prostate gland, and Cowper’s gland). The accessory glands secrete fluid to form the semen that carries the sperm.
Watch and Listen
Watch the video clip "BiologiX 14: The Male Reproductive System: Perpetuating the Species" to further your understanding of the Male Reproductive structures.
Try This
Test your knowledge of the location and function of various structures in the male reproductive system by completing this Male Reproductive System Drag and Drop. Drag the text to the appropriate place on the diagram. The answer box you are dragging a term to needs to be outlined before you "drop" the term. Only correct terms will stay in an answer box.
