Chapter 21: Reproductive System
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.
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.
The male reproductive system
21-4
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.
Penis anatomy
21-6
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.
21-7
Testes
Interstitial cells that lie between the seminiferous tubules within testes
produce testosterone.
21-8
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.
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.
21-10
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. - FollicleStimulating Hormone (FSH) - Spermatogenesis and Luteinizing hormone (LH) Testosterone.
FSH stimulates the seminiferous tubules to produce sperm and the hormone
Inhibin.
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