anatomy and physiology of the male. topics anatomy physiology spermatogenesis hormonal regulation...
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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
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
Hypothalamic-Pituitary-Gonadal Axis
• Anterior Pituitary• LH – luteinizing
hormone• Released in response
to GnRH• Stimulates interstitial
cells (Leydig cells) to secrete testosterone
Hypothalamic-Pituitary-Gonadal Axis
• Anterior Pituitary• FSH – follicle
stimulating hormone• Released in response
to GnRH• Stimulates Sertoli
cells• ABP – androgen-
binding protein: Keeps concentration of testosterone high
Hypothalamic-Pituitary-Gonadal Axis
• Testosterone• meiosis of
spermatogenic cells• development and
maintenance of secondary sex characteristics
• Libido• Feed back to
pituitary and hypothalamus
Hypothalamic-Pituitary-Gonadal Axis
• Inhibin• Secreted by Sertoli
cells• produced in
response to sperm count
• Inhibits release of GnRH and FSH
Hypothalamic-Pituitary-Gonadal Axis
• 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
Reproductive System Development
7 weeks – ductus deferens forms•Seminiferous tubules form in gonadal ridges•Join the Wolffian ducts
•Testes secrete MIF – Mullerian Inhibitory factor•Mullerian ducts degenerate
Reproductive System Development
8 weeks – presence of testosterone•Genital tubercle enlarges
• forms penis•Urethral folds fuse
• Forms spongy urethra•Labioscrotal swellings fuse
• Form scrotum
Reproductive System Development
•• At 7 months G stops growing and becomes fibrous• Rapid growth of fetus causes G to pull testis into the
scrotum
Gubernaculum (G) (blue) – connects testis to floor of scrotum
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