anatomy and physiology of the male

Anatomy and Physiology of the

Male

Topics

● Anatomy● Physiology● Spermatogenesis● Hormonal regulation● Development

Anatomy

● Scrotum● Testes● Penis● Glands

Scrotum

● Maintains 34°C (93.2°F)● Dartos muscle –

wrinkles the skin● Cremaster muscles –

draw scrotum toward abdomen

Testes● Coverings

● Tunica vaginalis● Tunica albuginea

● Lobules● Seminiferous

tubules● Tubulus rectus

● Rete testis● Epididymis

Testes Blood Supply

● Countercurrent heat exchange● Testicular artery● Pampiniform

venous plexus

Testes Blood Supply

● Varicocele● Varicose vein like condition● 15-20% of males● 40% of infertile males

Penis external anatomy

● Foreskin● 60% in US

are circumcised

● 15% worldwide

● Shaft● Glans penis

Penis internal anatomy

● Corpus spongiosum● Bulb of penis

● Corpora cavernosum● Crura of the

penis

Male Duct System

● Epididymus● 20 feet!● 20 days for

sperm to mature

● Smooth muscles expel sperm during ejaculation

● Cells have microvilli

Male Duct System

● Epididymus● Smooth

muscles expel sperm during ejaculation

● Cells have microvilli

Male Duct System

● Ductus (vas) deferens● 18”● Very muscular● Ampulla

Male Duct System

● Vasectomy● Almost 100%

effective● Reversal about

50% success rate

Male Duct System

● Ejaculatory duct● Urethra

● Conveys both urine and semen

● Prostatic● Membranous ● Penile

● Urethral glands secrete mucus prior to ejaculation

Glands● Seminal vesicles● Size of little

finger● Surrounded by

smooth muscle● Seminal fluid

● Fructose● Ascorbic acid● Coagulating

enzyme● Prostaglandins● Other factors

that enhance sperm mobility

Glands● Prostate● Size of peach pit● Several ducts into the

prostatic urethra● Surrounded by

smooth muscle● Secretions

● Citrate● Enzymes (fibrinolysin,

hyaluronidase, acid phosphatase)

● Prostate specific antigen (PSA)

● activate sperm

Glands

● Bulbourethral glands● Pea sized● Mucus

● Lubrication● Neutralizes

acidic urine prior to ejaculation

Semen

● 2-5ml● Composed of

● Sperm (10%)● Testicular fluid● Gland secretions

Semen● Functions

● Transport, activation and protective medium● Nutrients for sperm (fructose)● Neutralizes vaginal tract● Prostaglandins reduce viscosity of mucus at

cervix● Enzymes enhance motility● Antibiotics● Chemicals that suppress the female immune

system● Clotting factors that coagulate semen so it

sticks to vagina● Fibrinolysin then dissolves that mass

Physiology

● Erection● NO (nitric oxide) released (in penis

tissue)● Causes arterioles (normally constricted)

to relax/dilate● Blood flows into the corpora cavernosa● Compresses veins to prevent flow out● Corpus spongiosum also expands but

maintains open urethra● Bulbourethral glands secrete lubricant

Physiology● Ejaculation

● Spinal reflex● Bladder sphincter muscle constricts● Reproductive ducts and glands contract

● Contents enter urethra● Muscles around the blub of penis –

series of rapid contractions● Other systemic changes

● Rapid heartbeat● Elevated blood pressure● Generalized muscle contraction

Erectile dysfunction● Deficient NO release

● Viagara, Cialis and Levitra increase effects of NO

● Possible factors● Psychological factors● Alcohol or drugs

● Antihypertensives, Antidepressants● Diabetes mellitus● Arteriosclerosis● Varicose veins● Nervous system issues

● Stroke, Penile nerve damage, MS

Spermatogenesis

● Meiosis● Sertoli cells

● Nourish and “clean”

● Secrete testicular fluid

● androgens● Tight junction

● Blood-testis barrier

● prevents sperm antigens from the immune system

Spermatogenesis

Spermatogenesis

● Spermatogenic cell● 64-72 days

Infertility● 1/7 of Americans; most due to sperm

issues● Estrogen-like compounds● Antibiotics (tetracycline)● Compounds that lead to abnormal sperm

● Radiation, marijuana, lack of selenium, alcohol

● Lack of a specific Ca++ channel (for motility)

● Anatomical obstruction● Hormonal imbalance● Oxidative stress (damages DNA)● overheating

Hormonal Regulation● Hypothalamic-

Pituitary-Gonadal Axis● Hypothalamus● Anterior pituitary● Testes

Hypothalamic-Pituitary-Gonadal Axis

● Hypothalamus● GnRH –

gonadotropin releasing hormone

● Stimulates the anterior pituitary


● Anterior Pituitary● LH – luteinizing

hormone● Released in response

to GnRH● Stimulates interstitial

cells (Leydig cells) to secrete testosterone


● Anterior Pituitary● FSH – follicle

stimulating hormone● Released in response

to GnRH● Stimulates Sertoli

cells● ABP – androgen-

binding protein: Keeps concentration of testosterone high


● Testosterone● meiosis of

spermatogenic cells● development and

maintenance of secondary sex characteristics

● Libido● Feed back to

pituitary and hypothalamus


● Inhibin● Secreted by Sertoli

cells● produced in

response to sperm count

● Inhibits release of GnRH and FSH


● Absence of GnRH, FSH and LH● Testicular atrophy● Accessory organs

atrophy● Testosterone

production declines (or ceases)

Secondary sex characteristics● Pubic and axillary hair● Facial and chest hair● Larynx enlarges● Skin thickens and becomes

oilier● Bones grow and increase

density● Skeletal muscle increases● Basal metabolic rate increases● Development of libido● Brain development

Reproductive System Development

5 weeks● gonadal ridges● Mullerian ducts –

female● Wolffian duct – maleGerm cells migrate to gonad


7 weeks – ductus deferens forms● Seminiferous tubules

form in gonadal ridges● Join the Wolffian ducts

● Testes secrete MIF – Mullerian Inhibitory factor

● Mullerian ducts degenerate


8 weeks – presence of testosterone● Genital tubercle enlarges

● forms penis● Urethral folds fuse

● Forms spongy urethra● Labioscrotal swellings fuse

● Form scrotum


● Gubernaculum (G) (blue) – connects testis to floor of scrotum

● At 7 months G stops growing and becomes fibrous● Rapid growth of fetus causes G to pull testis into the

scrotum

anatomy and physiology of the male

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