1. Unit Fourteen: Endocrinology and Reproduction
Chapter 80: Reproductive and Hormonal
Functions of the Male (and Function of the
Pineal Gland
Guyton and Hall, Textbook of Medical Physiology, 12 edition

2. Physiologic Anatomy of the Male Sexual Organs
Fig Male reproduction system

3. Steps of Spermatogenesis and Meiosis
Fig A: Cross-section of a seminiferous tubule
B: Stages in the development of sperm
from spermatogonia

4. Steps of Spermatogenesis and Meiosis
Fig Cell divisions during spermatogenesis

5. Spermatogenesis
Sex Chromosomes
In each spermatogonium, one of the 23 pairs of
chromosomes carries the genetic information
that determines the sex of each eventual
offspring
The pair consists of one X chromosome and one
Y chromosome

6. Spermatogenesis Formation of Sperm Fig. 80.4 Structure of the human
spermatozoan

7. Spermatogenesis
Formation of Sperm
Composed of a head and tail; acrosome covers
the head (contains enzymes like hyaluronidase)
Tail is the flagellum made up of microtubules
Back and forth motion provides motility for
the sperm

8. Spermatogenesis
Hormonal Factors That Stimulate Spermatogenesis
Testosterone secreted by Leydig’s cells in the
interstitium of the testes; essential for growth and
division of the testicular germinal cells, the first
stage of forming sperm
Leutinizing hormone (LH)-stimulates the Leydig cells
Follicle stimulating hormone (FSH)-stimulates the
Sertoli cells; stimulates the conversion of spermatids to
sperm

9. Spermatogenesis
Hormonal Factors That Stimulate Spermatogenesis
Estrogens-formed from testosterone by the Sertoli
cells when stimulated by FSH
Growth hormone-necessary for controlling
background metabolic functions of the testes

10. Spermatogenesis
Maturation of Sperm in the Epididymis
After hours in the epididymis, the sperm acquire
the capability of motility
Storage of sperm in the testes-form about 120 million
sperm per day in the two testes; most are stored in the
vas deferens and can remain viable for about one month
After ejaculation, the sperm become motile and capable
of fertilizing the ovum (called maturation); Sertoli cells
and the epididymis secrete a fluid with the sperm that
contains nutrients, enzymes, and hormones

11. Spermatogenesis
Maturation of Sperm in the Epididymis
Physiology of the mature sperm-move at a velocity of
1-4 mm/min
Movement is greatly enhanced in neutral or slightly
alkaline media; depressed in mildly acidic and highly
acidic is rapidly fatal
Life expectancy of ejaculated sperm in the female
genital tract is 1-2 days

12. Spermatogenesis
Function of the Seminal Vesicles
Secretes a mucoid material containing fructose, citric
acid, prostaglandins, and fibrinogen
Prostaglandins (1) react with cervical mucus to make it
more receptive to sperm movement, and (2) possibly
cause a reverse backward peristalsis in the uterus and
Fallopian tubes to move the sperm toward the ovaries

13. Spermatogenesis
Function of the Prostate Gland
Secretes a thin milky fluid that contains calcium,
citrate ion, phosphate ion, a clotting enzyme, and
a profibrinolysin
Slightly alkaline prostatic fluid helps to neutralize
the acidity of the other seminal fluids during
ejaculation

14. Spermatogenesis
Semen
Ejaculated during the male sexual act, is composed of
fluid and sperm from the vas deferens (10% of the total),
fluid from the seminal vesicles (60%), fluid from the
prostate gland (30%), and small amounts from the
bulbourethral glands.
Average pH is 7.5
Clotting enzymes help form a weak coagulum that holds
the semen in the deep recesses of the vagina
Eventually lyses due to the fibrinolysin; becomes very
motile then

15. Spermatogenesis
Capacitation
Although sperm are said to be mature when they
leave the epididymis, their activity is held in check
by many inhibitory factors
Upon contact with the female genital tract, multiple
changes occur that activate the sperm for the final
processes of fertilization
c. Changes are referred to as capacitation

16. Spermatogenesis
Capacitation
Uterine and fallopian tubes fluids wash away
the inhibitory factors from the male genital
ducts
The membrane head of the acrosome becomes
weaker
Membrane of the sperm becomes more
permeable to calcium; activates the flagellar
movement and allows the acrosome to release
its enzymes more readily

17. Spermatogenesis
Acrosome Enzymes
When the sperm reaches the zona pellucida of the
ovum, the anterior membrane of the sperm binds
with specific receptor proteins in the zona
pellucida
The entire acrosome then rapidly dissolves and
the acrosomal enzymes are released
The enzymes open a passageway for the sperm and
the sperm and ovum nuclei fuse within 30 minutes

18. Abnormal Spermatogenesis and Fertility
Bilateral orchitis (mumps infection)
Excessive temperature of the testes
Cryptorchidism-failure of descent of the testes
Effect of sperm count (<20,000,000/ml)
Sperm morphology and motility
Fig Abnormal infertile sperm, compared
with a normal sperm on the right

19. Male Sexual Act
Neuronal Stimulus for Performance of the Male
Sexual Act

20. Male Sexual Act
Psychic Element
Integration in the Spinal Cord

21. Male Sexual Act
Stages of the Male Sexual Act
Penile erection
Lubrication
Emission and ejaculation

22. Testosterone and Other Male Hormones
Secretion, Metabolism, and Chemistry
Secretion of testosterone by the interstitial cells of
Leydig in the testes (also produce dihydrotestosterone,
androstenedione)
Leydig cells are numerous in the newborn and after
puberty

23. Testosterone and Other Male Hormones
Secretion, Metabolism, and Chemistry
Fig Interstitial cells of Leydig, the cells that secrete
testosterone

24. Testosterone and Other Male Hormones
Secretion, Metabolism, and Chemistry
Androgens elsewhere in the body-adrenal secrete
about 5 androgens
d. All androgens are steroid compounds
Fig. 80.8

25. Testosterone and Other Male Hormones
Functions of Testosterone During Development
During fetal development-secreted by the genital
ridges and later by the fetal testes is responsible
for the development of male body characteristics
(regulated by the SRY gene) while suppressing the
development of female genital organs
At 2-3 months of gestation, causes the descent of
the testes into the scrotum

26. Testosterone and Other Male Hormones
Functions of Testosterone During Development
of the Adult Primary and Secondary Sexual
Characteristics
Distribution of body hair-over the pubis, upward
along the linea alba, chest, and other areas
Decreases hair growth on the top of the head
Causes hypertrophy of the laryngeal mucosa and
enlargement of the larynx-masculine voice
Increases the thickness of the skin and can contribute
to acne
Increases protein formation and muscle development
Increases bone matrix and causes calcium retention

27. Testosterone and Other Male Hormones
Functions of Testosterone During Development
of the Adult Primary and Secondary Sexual
Characteristics
Increases the BMR
Increases the number of erythrocytes
Minor effect increasing the reabsorption of
sodium b y the distal tubules of the kidneys

28. Testosterone and Other Male Hormones
Intracellular Mechanism of Action
Most of the effects result basically from increased rate
of protein synthesis in the target cells
Control of Male Sexual Functions
Begins with the secretion of GnRH by the hypothalamus
Pituitary releases LH and FSH for testosterone release
or spermatogenesis

29. Testosterone and Other Male Hormones
Fig Feedback regulationof the hypothalamic-pituitary-
testicular axis in males

30. Abnormalities of Male Sexual Function
Male Climacteric
Prostate Gland
Hypogonadism
Hypergonadism and Testicular Tumors
Erectile Dysfunction