Unit One: Introduction to Physiology: The Cell and General Physiology

Unit Fourteen: Endocrinology and ReproductionChapter 80: Reproductive and Hormonal Functions of the Male (and Function of the Pineal GlandGuyton and Hall, Textbook of Medical Physiology, 12 editionPhysiologic Anatomy of the Male Sexual Organs

Fig. 80.1 Male reproduction systemSpermatogenesis Steps of Spermatogenesis and Meiosis

Fig. 80.2 A: Cross-section of a seminiferous tubule B: Stages in the development of sperm from spermatogoniaSpermatogenesis Steps of Spermatogenesis and MeiosisFig. 80.3 Cell divisions during spermatogenesis

Spermatogenesis Sex Chromosomes

In each spermatogonium, one of the 23 pairs ofchromosomes carries the genetic informationthat determines the sex of each eventualoffspring

The pair consists of one X chromosome and oneY chromosomeSpermatogenesis Formation of Sperm

Fig. 80.4 Structure of the human spermatozoanSpermatogenesis Formation of Sperm

Composed of a head and tail; acrosome coversthe head (contains enzymes like hyaluronidase)

Tail is the flagellum made up of microtubules

Back and forth motion provides motility forthe sperm

Spermatogenesis Hormonal Factors That Stimulate Spermatogenesis

Testosterone secreted by Leydigs cells in the interstitium of the testes; essential for growth anddivision 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 tosperm

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 testesSpermatogenesis Maturation of Sperm in the Epididymis

After 18-24 hours in the epididymis, the sperm acquirethe capability of motility

Storage of sperm in the testes-form about 120 million sperm per day in the two testes; most are stored in thevas deferens and can remain viable for about one month

After ejaculation, the sperm become motile and capableof fertilizing the ovum (called maturation); Sertoli cellsand the epididymis secrete a fluid with the sperm that contains nutrients, enzymes, and hormonesSpermatogenesis Maturation of Sperm in the Epididymis

Physiology of the mature sperm-move at a velocity of1-4 mm/min

Movement is greatly enhanced in neutral or slightlyalkaline media; depressed in mildly acidic and highlyacidic is rapidly fatal

Life expectancy of ejaculated sperm in the femalegenital tract is 1-2 daysSpermatogenesis Function of the Seminal Vesicles

Secretes a mucoid material containing fructose, citricacid, prostaglandins, and fibrinogen

Prostaglandins (1) react with cervical mucus to make itmore receptive to sperm movement, and (2) possiblycause a reverse backward peristalsis in the uterus andFallopian tubes to move the sperm toward the ovariesSpermatogenesis Function of the Prostate Gland

Secretes a thin milky fluid that contains calcium, citrate ion, phosphate ion, a clotting enzyme, anda profibrinolysin

Slightly alkaline prostatic fluid helps to neutralizethe acidity of the other seminal fluids during ejaculationSpermatogenesis Semen

Ejaculated during the male sexual act, is composed offluid and sperm from the vas deferens (10% of the total),fluid from the seminal vesicles (60%), fluid from theprostate gland (30%), and small amounts from the bulbourethral glands.

Average pH is 7.5

Clotting enzymes help form a weak coagulum that holdsthe semen in the deep recesses of the vagina

Eventually lyses due to the fibrinolysin; becomes very motile then

Spermatogenesis Capacitation

Although sperm are said to be mature when theyleave the epididymis, their activity is held in checkby many inhibitory factors

Upon contact with the female genital tract, multiplechanges occur that activate the sperm for the finalprocesses of fertilization

c.Changes are referred to as capacitation

Spermatogenesis Capacitation

Uterine and fallopian tubes fluids wash awaythe inhibitory factors from the male genitalductsThe membrane head of the acrosome becomesweakerMembrane of the sperm becomes more permeable to calcium; activates the flagellar movement and allows the acrosome to releaseits enzymes more readilySpermatogenesis Acrosome Enzymes

When the sperm reaches the zona pellucida of theovum, the anterior membrane of the sperm bindswith specific receptor proteins in the zonapellucidaThe entire acrosome then rapidly dissolves and the acrosomal enzymes are releasedThe enzymes open a passageway for the sperm and the sperm and ovum nuclei fuse within 30 minutes Spermatogenesis Abnormal Spermatogenesis and Fertility

Bilateral orchitis (mumps infection)Excessive temperature of the testesCryptorchidism-failure of descent of the testesEffect of sperm count (