the Male Genitourinary System

Components of the Male Genitourinary System
Paired gonads or testes
Genital ducts
Accessory organs
Penis
Functions of the Male Genitourinary System
Testes
Produce male sex androgens, mainly testosterone
Spermatozoa (male germ cells)
Internal accessory organs
Produce the fluid constituents of semen
Ductile system aids in the storage and transport of spermatozoa
Penis
Urine elimination and sexual function
Embryonic Development of the Reproductive System
Fertilization
Sex chromosomes determine the sex
Early stages
The tissues from which the male and female reproductive organs develop are undifferentiated
By the seventh week
Two wolffian ducts determine male genitalia and two müllerian ducts determine female genitalia
Embryonic Development of the Reproductive System (cont.)
Sixth to eighth week of gestation
The testes begin development under the influence of the Y chromosome
The testicular cells of the male embryo begin producing an anti-müllerian hormone (AMH) and testosterone
AMH suppress development or uterus and fallopian tubes in the male; stimulates development of male structures

Systems Maintaining Temperature of Testes
Pampiniform plexus of testicular veins
Surrounds the testicular artery
Absorbs heat from the arterial blood, cooling it as it enters the testes
Cremaster muscles
Respond to decreases in testicular temperature by moving the testes closer to the body
Male Accessory Organs
Seminal vesicles
Prostate gland
Bulbourethral glands
Component Glands of the Prostate
Small mucosal glands
Associated with the urethral mucosa
Intermediate submucosal glands
Lie peripheral to the mucosal glands
Large main prostatic glands
Situated toward the outside of the gland
Composition of the Penis
Three masses of erectile tissue held together by fibrous strands and covered with a thin layer of skin
Corpora Cavernosa: Two lateral masses of tissue
Corpus Spongiosum: Third ventral mass
Both are cavernous sinuses that normally are relatively empty but become engorged with blood during penile erection

Spermatogenesis
The generation of spermatozoa or sperm
Begins at an average age of 13 years and continues throughout the reproductive years of a man’s life
Occurs in the seminiferous tubules of the testes
For spermatogenesis to occur, FSH binds to specific receptors in Sertoli’s cells
Testosterone is also required (the intra-testicular concentration of testosterone is 100-fold greater than serum levels)

Male Sex Hormones (Androgens)
Testosterone
Dihydrotestosterone
Androstenedione
Main Actions of Testosterone
Induce differentiation of the male genital tract during fetal development
Induce development of primary and secondary sex characteristics
Create anabolic effects
Promote spermatogenesis and maturation of sperm
Primary and Secondary Sex Characteristics
Agonadal function
External genitalia and accessory organs
Male voice timbre
Male skin characteristics
Male hair distribution
Anabolic Effects of Testosterone
Promotes protein metabolism
Promotes musculoskeletal growth
Influences subcutaneous fat distribution
Drugs Used to Enhance Performance
Androgen
Stimulants
Erythropoietin
Growth hormone
Insulin
Creatine
Gonadotropic Hormones Secreted by the Pituitary Gland
FSH
Luteinizing hormone (LH)
Diagnosis of Androgen Deficiency
Appearance of certain clinical features
Fatigue, depression, decreased libido
Confirmation by appropriate laboratory testing
A measure of ‘free testosterone’ (testosterone not bound [especially to SHBG], and therefore available for binding to, and activating, androgen receptors)
Free Testosterone is low in hypogonadism

Neural Control of the Sex Act
The glans penis contains a highly organized sensory system
Afferent impulses from sensory receptors in the glans penis pass through the pudendal nerve to ascending fibers in the spinal cord by way of the sacral plexus
Stimulation of other perineal areas can transmit signals to higher brain centers, adding to sexual satisfaction
Erection
Involves
The shunting of blood into the corpus cavernosum
Controlled by
Sympathetic systems
Parasympathetic systems
Non-sympathetic—non-parasympathetic systems
Effect of Aging on the Male Reproductive System
Degenerative changes occur as a result of the aging process
It becomes less efficient with age
The declining physiologic efficiency of male reproductive function occurs gradually
Involves the endocrine, circulatory, and neuromuscular systems
Diseases Affecting Potency
Cardiovascular disease
Respiratory diseases
Hormonal disease
Neurologic and hematologic disorders