Male Reproductive System Chapter 17 Male Reproductive System

FIGURE 17.1 part 1 The male reproductive system

FIGURE 17.1 part 2 The male reproductive system

Each testis contains about 250 meters of seminiferous tubule FIGURE 17.2 The internal structure of the testis and epididymis Each testis contains about 250 meters of seminiferous tubule

Two Major Functions of Testes Testes: produce sperm (spermatogenesis) Production Site: seminiferous tubules About 250 meters of tubule/testis 100 – 300 million sperm/day produced Testes also produce male hormones (testosterone)

Delivery of Sperm to the Egg The duct system stores and transports sperm Delivery through reproductive tubules: epididymis  vas deferens  urethra  penis

Delivery of Sperm to the Egg The seminal vesicles and prostate gland (accessory glands) produce most of the volume of semen The penis transfers sperm to the female

The organ where sperm are produced is Testes Prostate gland Seminal vesicle Penis

Sperm Production Sperm development involves reduction in the number of chromosomes and in the structure of sperm cells Several cell divisions of mitosis and meiosis Purpose: produce a large number (> 100 million/day) of sperm with half the number of chromosomes of somatic cells (haploid)

Figure: 19-11 Title: Comparison of spermatogenesis and oogenesis. Caption: Meiosis results in haploid cells that differentiate into mature gametes. Spermatogenesis produces four sperm cells that are specialized to transport the male’s genetic information to the egg. Oogenesis produces three polar bodies and one ovum that is packed with nutrients to nourish the early embryo.

FIGURE 17.3 The stages of spermatogenesis in the wall of a seminiferous tubule. As the cells that will become sperm develop, they are pushed from the outer wall of the tubule to the lumen, or central canal.

(Leydig cells)

FIGURE 17.4 The structure of a mature sperm (spermatozoan)

The organ where sperm are produced is Prostate gland Testes Seminal vesicle Ovary

Mature sperm contain: 46 chromosomes The same number of chromosomes as the father 23 chromosomes Half the number of chromosomes as the father

Male Reproductive Hormones Testosterone Source: Interstitial (Leydig) cells in testes LH: stimulates production of testosterone in interstitial (Leydig) cells FSH: enhances sperm formation by Sertoli cells

Testosterone secretion is regulated by a negative feedback loop (see in class worksheet)

The Male Reproductive System The hypothalamus (neurosecretory cells) releases gonadotropin-releasing hormone (GnRH) GnRH stimulates the anterior pituitary gland to secrete luteinizing hormone (LH) LH stimulates the production of testosterone by the testes

The rising testosterone level inhibits the release of GnRH to complete the loop

Actions of Testosterone on Target Tissues Controls growth and function of male reproductive tissues (e.g., prostate & seminal vesicles) Secondary sexual characteristics: muscle, auxiliary hair, larynx, balding pattern Stimulates aggression and sexual behavior

Testosterone has effects on: Male secondary sexual characteristics, e.g., muscle, beard growth Prostate gland Sex drive

TABLE 17.2 REVIEW OF HORMONES IMPORTANT IN THE REGULATION OF MALE REPRODUCTIVE PROCESSES

TABLE 17.1 REVIEW OF MALE REPRODUCTIVE SYSTEM

The function of the prostate gland is to: Produce sperm Produce testosterone Produce secretions (semen) that make sperm mobile Store sperm