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Chapter 21: Reproductive System

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Title: Chapter 21: Reproductive System


1
Chapter 21 Reproductive System
2
Male Reproductive System
  • Genital Tract
  • In males the testes, held outside the body in the
    scrotum (optimum temp of about 350C), produce
    sperm.
  • Sperm mature in coiled tubes atop each testis,
    called the epididymis (plural, epididymides).
  • At ejaculation, sperm leave the testes through
    the vas deferens (plural, vasa deferentia), and
    pass through the ejaculatory ducts to the
    urethra.

3
  • Along the way, secretions (seminal fluid) are
    added from three glands two seminal vesicles,
    the donut-shaped prostate gland at the base of
    the urinary bladder, and paired bulbourethral
    glands.
  • These glands add fructose (SV) for energy so
    sperm can swim, and prostaglandins (SV) that
    cause uterine contractions the secretions are
    slightly basic (prostate)
  • Sperm with secretions from these glands is called
    semen.

4
The male reproductive system
5
Orgasm in Males
  • The penis, the organ of sexual, intercourse,
    becomes erect from sexual arousal that stimulates
    cGMP in smooth muscle cells to allow erectile
    tissue to fill with blood arterioles dilate and
    veins are compressed.
  • Orgasm involves ejaculation and muscular tension
    followed by muscular contractions and relaxation.
  • Over 400 million sperm may be in each ejaculate.

6
Penis anatomy
7
Male Gonads, the Testes
  • The testes, which produce sperm and male sex
    hormones, contain Seminiferous tubules
    (Spermatogenesis) surrounded by Interstitial
    cells (Testosterone)
  • Testes originate in the abdominal cavity but
    descend into the scrotum where it is cool enough
    for sperm development.

8
Testes
Interstitial cells that lie between the
seminiferous tubules within testes produce
testosterone.
9
Seminiferous Tubules
  • Seminiferous tubules inside the testes produce
    haploid sperm through spermatogenesis.
  • Sustentacular cells (Sertoli cells) support,
    nourish, and regulate the cells during
    spermatogenesis.
  • Sperm have a head, middle piece, and tail.

10
  • The head of the sperm is covered by a cap called
    the acrosome which stores enzymes needed to
    penetrate the egg.
  • Sperm do not live more than 48 hours in the
    female genital tract.

11
Hormonal Regulation in Males
  • In both males and females, gonadotropin-releasing
    hormone, or GnRH, secreted by the hypothalamus
    stimulates the anterior pituitary to release two
    Gonadotropin Hormones from the Anterior Pituitary
    Gland. - Follicle-Stimulating Hormone (FSH) -
    Spermatogenesis and Luteinizing hormone (LH) -
    Testosterone.
  • FSH stimulates the seminiferous tubules to
    produce sperm and the hormone Inhibin.

12
  • LH stimulates interstitial cells to produce
    testosterone.
  • Testosterone brings about and maintains the male
    secondary sex characteristics.
  • Testosterone exerts feedback control over the
    hypothalamus and anterior pituitary resulting in
    a constant amount of hormones and sperm
    production over time.

Lutenizing Hormone Testosterone
Follicle Stimulating Hormone (FSH)
Spermatogenesis
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