UNIT B: Human Body Systems Chapter 8: Human Organization Chapter 9: Digestive System Chapter 10: Circulatory System and Lymphatic System Chapter 11: Respiratory System Chapter 12: Nervous System Chapter 13: Urinary System Chapter 14: Reproductive System: Section 14.1
Chapter 14: Reproductive System UNIT B Chapter 14: Reproductive System TO PREVIOUS SLIDE What different events must occur before fertilization? What is the function of the umbilical cord? Cord blood banking. Cord blood can be used to treat diseases such as leukemia, lymphoma, and other blood and immune system disorders. After an umbilical cord blood sample is collected, it is stored in a cord blood bank. There are both private and public banks. In this chapter you will learn about the male and female reproductive systems, the ovarian and uterine cycles, and disorders of the reproductive systems.
14.1 Male Reproductive System Organisms that carry out sexual reproduction produce gametes, haploid sex cells that are united during fertilization. In the male reproductive system, the sperm are gametes that are produced in paired testes (male gonads) o Seminal fluid: a nutrient-rich fluid in which sperm leave the penis during ejaculation o Semen: combination of sperm and seminal fluid UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System
UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System Figure 14.1 The male reproductive system. The testes produce sperm. The seminal vesicles, the prostate gland, and the bulbourethral glands provide a fluid medium for the sperm, which move from the vasa deferentia through the ejaculatory ducts to the urethra in the penis.
Genital Tract Testes: paired structures that produce sperm and sex hormones Epididymides: ducts outside the testes where sperm mature and are stored Vas deferens: stores sperm; empties into an ejaculatory duct UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System
Urethra: connected to the ejaculatory duct Seminal vesicles: contribute nutrients and fluids to semen Prostate gland: contributes basic solution to semen (sperm are more viable in a basic solution) Cowper’s glands: secrete a mucus-rich fluid that helps lubricate the penis UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System
Penis: male organ of sexual intercourse o Circumcision: surgical removal of the foreskin UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System Figure 14.2 Penis anatomy. a. Beneath the skin and the connective tissue lies the urethra, surrounded by erectile tissue. This tissue expands to form the glans penis, which in uncircumcised males is partially covered by the foreskin (prepuce). b. Two other columns of erectile tissue in the penis are located dorsally.
UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System
Erection and Orgasm in Males Erection Erectile tissue extends throughout the shaft of the penis Sexual excitement causes the arteries in the penis to relax and widen Increased blood flow causes the penis to enlarge and become erect UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System Figure 14.2 Penis anatomy. b. Two other columns of erectile tissue in the penis are located dorsally.
Ejaculation and Orgasm When sexual stimulation intensifies, sperm enter the urethra from the vasa deferentia and the accessory glands contribute secretions to the semen Rhythmic muscle contractions cause semen to be ejaculated from the penis o These contractions are part of male orgasm (climax of sexual stimulation) A refractory period occurs after ejaculation, where sexual stimulation does not cause an erection More than 400 million sperm are expelled in 2 to 6 mL of semen during ejaculation UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System
Male Gonads, the Testes Testes Lie within the scrotum The scrotum helps regulate testicular temperature by holding the testes closer or farther away from the body Increases in temperature may decrease sperm production UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System Figure 14.3 Testis and sperm. a. The lobules of a testis contain seminiferous tubules.
Seminiferous Tubules A testis is composed of lobules, each of which contains tightly coiled seminiferous tubules Intersitial cells that lie between the tubules secrete male sex hormones (androgens) Seminiferous tubules contain cells undergoing spermatogenesis (production of sperm) UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System Figure 14.3 Testis and sperm. b. Light micrographs of a cross section of the seminiferous tubules, where spermatogenesis occurs. Note the location of interstitial cells in clumps among the seminiferous tubules.
UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System Figure 14.3 Testis and sperm. a. The lobules of a testis contain seminiferous tubules. b. Light micrographs of a cross section of the seminiferous tubules, where spermatogenesis occurs. Note the location of interstitial cells in clumps among the seminiferous tubules.
Spermatogenesis Occurs in the walls of the seminiferous tubules Spermatogonia become primary spermatocytes that undergo meiosis I to produce secondary spermatocytes Secondary spermatocytes undergo meiosis II to produce four haploid spermatids Spermatids differentiate into sperm Sertoli cells support, nourish, and regulate the spermatogenic cells UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System
UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System Figure 14.3 Testis and sperm. c. Diagrammatic representation of spermatogenesis, which occurs in the walls of the tubules.
Sperm Mature sperm (spermatozoa) have a head, middle piece, and a tail Mitochondria in the middle piece is the site of ATP production for the movement of the tail The acrosome is a cap that stores enzymes needed to penetrate the egg The nucleus of the sperm has the male’s DNA as 23 chromosomes Sperm usually do not live more than 48 hours in the female genital tract UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System Figure 14.3 Testis and sperm. d. A sperm has a head, a middle piece, tail, and an end piece. The nucleus is in the head, which is capped by the enzyme-containing acrosome.
Hormonal Regulation in Males Hypothalamus controls secretions of the pituitary gland by secreting gonadotropin-releasing hormone (GnRH). GnRH: stimulates the pituitary gland to release follicle- stimulating hormone (FSH) and luteinizing hormone (LH) o FSH: promotes sperm production in the seminiferous tubules (which secrete inhibin, a hormone which inhibits FSH synthesis) o LH: also called interstitial-cell-stimulating hormone (ICSH) because it promotes the production of testosterone by interstitial cells UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System
UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System Figure 14.4 Hormonal control of testes. GnRH stimulates the anterior pituitary to produce FSH and LH. FSH stimulates the testes to produce sperm, and LH stimulates the testes to produce testosterone. Testosterone from interstitial cells and inhibin from the seminiferous tubules exert negative feedback control over the hypothalamus and the anterior pituitary, and this ultimately regulates the level of testosterone in the blood.
Testosterone The main sex hormone in males Essential for normal development and functioning of male reproductive structures Maintains male secondary sex characteristics that develop at puberty (body hair, deeper voices, greater muscular development) UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System
Check Your Progress 1.Compare the functions of the seminiferous tubules, interstitial cells, epididymis, vasa deferentia, and urethra. 2.List the three glands that add secretions to semen. 3.Explain the roles of GnRH, FSH, ICSH and testosterone in male reproduction. UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System
UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System
UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System
UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System
UNIT B TO PREVIOUS SLIDE Section 14.1 Chapter 14: Reproductive System