Spermiogenesis Process Image

The fluid expelled during orgasm is called semen,32 or seminal fluid. A typical ejaculation discharges 2 to 5 mL

Saladin: Anatomy & Physiology: The Unity of Form and Function, Third Edition

1036 Part Five Reproduction and Development

Spermiogenesis Sperm
Figure 27.17 Spermiogenesis. In this process, the spermatids discard excess cytoplasm, grow tails, and become spermatozoa.

Acrosome Nucleus

Basal body

Mitochondria-

Axoneme

-Head

Axoneme

Cervical Mucus And Seminal Fluid

Midpiece (body)

Principal piece

Endpiece

-Head

Midpiece (body)

Principal piece

Endpiece

Tail

Male Reproductive Structures Mcgraw

Acrosome

Nucleus

Midpiece of tail Mitochondria

Axoneme

Principal piece of tail

Acrosome

Nucleus

Midpiece of tail Mitochondria

Axoneme

Principal piece of tail

Figure 27.18 The Mature Spermatozoon. (a) Structure. (b) Head and part of the tail of a spermatozoon (TEM).

Saladin: Anatomy & I 27. The Male Reproductive I Text I © The McGraw-Hill

Physiology: The Unity of System Companies, 2003 Form and Function, Third Edition

Chapter 27 The Male Reproductive System 1037

Table 27.1

Composition of Semen

Spermatozoa

Serve to digest a path through cervical mucus and to fertilize egg.

Fructose

Provides energy for sperm motility. Secreted by seminal vesicles.

Fibrinogen

Causes semen to clot when acted upon by prostatic clotting enzymes. Secreted by seminal vesicles.

Clotting Enzymes

Convert fibrinogen to fibrin after ejaculation, causing semen to clot and adhere to vagina and cervix.

Fibrinolysin

Dissolves fibrin and liquefies semen about 15 to 30 minutes after ejaculation, thus liberating sperm from the clot.

Prostaglandins

Stimulate peristaltic contractions of female reproductive tract; may help draw sperm into uterus or spread it through the uterus. Reduce viscosity of cervical mucus, making it easier for sperm to travel up cervical canal into uterus. Secreted by prostate and seminal vesicles.

Spermine

A base that gives the semen a pH of 7.2 to 7.6. Helps to neutralize vaginal acidity (pH 4-5) and thus activate sperm (sperm motility is poor below pH 6) and protect them from vaginal acid.

of semen, composed of about 60% seminal vesicle fluid, 30% prostatic fluid, 10% sperm and spermatic duct secretions, and a trace of bulbourethral fluid. The semen usually has a sperm count of 50 to 120 million sperm/mL. A sperm count any lower than 20 to 25 million sperm/mL is usually associated with infertility (sterility), the inability to fertilize an egg (see table 27.2). The major constituents of semen are listed in table 27.1.

Insight 27.3 Clinical Application

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