c. Erection, orgasm, and ejaculation
(1) During erection, vascular spaces in the erectile
tissue become engorged with blood as arteries
dilate and veins are compressed.
(2) Orgasm is the culmination of sexual
stimulation and is accompanied by emission
and ejaculation.
(3) Semen moves along the reproductive tract
as smooth muscle in the walls of the tubular
structures contract, stimulated by a refl ex.
(4) Following ejaculation, the penis becomes
1. Hypothalamic and pituitary hormones
The male body remains reproductively immature until
the hypothalamus releases GnRH, which stimulates
the anterior pituitary gland to release gonadotropins.
a. FSH stimulates spermatogenesis.
b. LH (ICSH) stimulates the interstitial cells to
produce male sex hormones.
c. Inhibin prevents oversecretion of FSH.
2. Male sex hormones
a. Male sex hormones are called androgens.
b. Testosterone is the most important androgen.
c. Testosterone is converted into dihydrotestosterone
in some organs.
d. Androgens that fail to become ±
xed in tissues are
metabolized in the liver and excreted.
e. Androgen production increases rapidly at puberty.
3. Actions of testosterone
a. Testosterone stimulates the development of the
male reproductive organs and causes the testes to
b. It is responsible for the development and
maintenance of male secondary sex characteristics.
4. Regulation of male sex hormones
a. A negative feedback mechanism regulates
testosterone concentration.
(1) As the concentration of testosterone rises, the
hypothalamus is inhibited, and the anterior
pituitary secretion of gonadotropins is
(2) As the concentration of testosterone falls, the
hypothalamus signals the anterior pituitary to
secrete gonadotropins.
b. The concentration of testosterone remains
relatively stable from day to day.
The primary female sex organs are the two ovaries, which
produce female sex cells and sex hormones. Accessory
organs are internal and external.
1. Ovaries
a. Ovary attachments
(1) Several ligaments hold the ovaries in position.
(2) These ligaments include broad, suspensory,
and ovarian ligaments.
2. Male internal accessory organs
a. Epididymides
(1) Each epididymis is a tightly coiled tube on the
outside of the testis that leads into the ductus
(2) It stores and nourishes immature sperm cells
and promotes their maturation.
b. Ductus deferentia
(1) Each ductus deferens is a muscular tube that
forms part of the spermatic cord.
(2) It passes through the inguinal canal, enters
the abdominal cavity, courses medially into
the pelvic cavity, and ends behind the urinary
(3) It fuses with the duct from the seminal vesicle
to form the ejaculatory duct.
c. Seminal vesicles
(1) Each seminal vesicle is a saclike structure
attached to the ductus deferens.
(2) It secretes an alkaline fl
uid that contains
nutrients, such as fructose, and prostaglandins.
(3) This secretion is added to sperm cells entering
the ejaculatory duct.
d. Prostate gland
(1) This gland surrounds the urethra just below
the urinary bladder.
(2) It secretes a thin, milky fl
uid, which
enhances sperm motility and neutralizes the
uid containing the sperm cells and acidic
secretions of the vagina.
e. Bulbourethral glands
(1) These glands are two small structures inferior
to the prostate gland.
(2) They secrete a fl
uid that lubricates the penis in
preparation for sexual intercourse.
f. Semen
(1) Semen consists of sperm cells and secretions
of the seminal vesicles, prostate gland, and
bulbourethral glands.
(2) This fl
uid is slightly alkaline and contains
nutrients and prostaglandins.
(3) Sperm cells in semen swim, but cannot
fertilize egg cells until they enter the female
reproductive tract.
3. Male external reproductive organs
a. Scrotum
(1) The scrotum is a pouch of skin and
subcutaneous tissue that encloses the testes.
(2) The dartos muscle in the scrotal wall causes
the scrotal skin to wrinkle and the testes to
move closer to the pelvic cavity or the ±
relax and the scrotum hangs loosely, regulating
the temperature for sperm production and
b. Penis
(1) The penis conveys urine and semen.
(2) It becomes erect for insertion into the vagina
during sexual intercourse.
(3) Its body is composed of three columns of
erectile tissue surrounded by connective tissue.
(4) The root of the penis is attached to the pelvic
arch and membranes of the perineum.
previous page 900 David Shier Hole's Human Anatomy and Physiology 2010 read online next page 902 David Shier Hole's Human Anatomy and Physiology 2010 read online Home Toggle text on/off