Male Sexual Anatomy, Physiology and Behaviour

Andre Sookdar

Class of 2013

Objectives

• Anatomy – External and Internal• Physiology and Behaviour

External Anatomy

Penis• Male Sexual Organ for intercourse• Pathway for Semen and Urine• Corpus Cavernosum – spongy tissue

that engorge with blood, stiffening penis• Corpus Spongiosum – contains urethra,

runs along the length, ending and dilating to form Glans

External Anatomy

• Root – Base of the penis• Shaft – Body of penis, which expands

on excitation• Foreskin – Loose collection of skin

covering the GlansSkin is attached just proximal to the head on the shaftCircumcision may be done based on choice, religion or culture.

External Anatomy

• Glans – Highly sensitive tip• Corona – rim that separates the Glans

from the shaft• Frenulum – strip of tissue connecting

the glans to the shaft

External Anatomy

Scrotum• Pouch containing the testes• Provides the ideal temperature for

spermatogenesis (2 degrees lower)• Left testis usually lower than right• Size, shape and surface area changed

by Dartos muscle

Internal Anatomy

Testes• Suspended in scrotum by spermatic

cord• Produces sperm and male sex

hormones• Highly innervated and sensitive• Moved by Cremasteric muscle

Internal Anatomy

• LH Stimulation of Testosterone secretion by Leydig interstitial cells

• FSH regulation of sperm production

• Negative feedback

Internal Anatomy

• Epididymis – lie against the back side of the testis and stores sperm

• Vas Deferens – tube that connects the epididymis to the ejaculatory duct

• Seminal Vesicles – small glands beneath the bladder that secrete seminal fluid

Internal Anatomy

• Prostate Gland – walnut sized gland that secretes prostatic fluid.

• Cowper’s Gland (Bulbouretheral Glands) – pea-sized glands at the base of the penis below the prostate that secrete fluid during sexual arousal

Male Anatomy

Semen

• 70% from seminal vesicles, 1% sperm, the rest from the Prostate and Cowper’s gland

• Typically has 200-400 million per ejaculate

• Over 15 million per ml is normal• Other parameters include motility,

morphology and volume.

Sexual Function

• Erection• Emission• Expulsion

Erection

• Engorgement of the penis with blood• Affected by physical and psychological

factors• Possible throughout the entire lifespan• During REM sleep• Stimulation may be from sensation via

the pudendal nerve or psychological stimuli via the limbic system

Erection

• Parasympathetic response to stimulation exits the spinal cord at S2-4 and reaches the penis via Nervi Erigentes

• These are believed to release nitric oxide and vasoactive intestinal peptide in addition to acetylcholine

• Results in relaxation of the penile arteries, hence vasodilation and expansion of the penis

• Parasympathetic impulses also stimulate the urethral and Cowper’s glands.

Emission

• Sympathetic impulses from T12 to L2 travel via hypogastric and pelvis nerve plexuses to initiate emission

• Contraction of vas deferens and ampulla, expelling sperm in to the internal urethra.

• Followed by contraction and fluid addition by the prostate, seminal vesicles and Cowper’s glands

• This is now semen and the formation of this in the internal urethra is emission

Journey of the Sperm

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Expulsion

• Expulsion or ejaculation• Filling of the internal urethra stimulates the pudendal

nerve contractions of the genital organs, the ischiocavernosus and bulbocavernosus muscles expulsion of semen

• The external urethral sphincter relaxes while Internal urethral sphincter contracts to prevent retrrograde ejaculation

• This may be accompanied by movement of the pelvic and trunk muscles

• Emission and ejaculation together make up the male orgasm, which lasts 1-2 minutes

Case 1

• A patient presents with the request to enlarge his penis….

Penis Enlargement

• Many cultures are obsessed with penis size

• No medication or device has ever been approved for penis enlargement

• Stretching & Squeezing• Penile Weights• Vacuum Pumps• Pills and lotions

Surgical Enlargement

• Lengthened by cutting the suspensory ligament that attaches penis to pubic bone

• Thickened by injecting body fat from another area

• Cosmetic, not medically indicated, safety an issue

Case 2

• 19 yo man presents with bumps on the glans and corona of his penis. He says he has had it as long as he can remember.

Pearly Penile Papules

• Benign lesion, not genital warts or HSV• Unknown etiology• Occurs more in uncircumcised• Requires no treatment

Conclusion

• Anatomy• Physiology• Sexual cycle

THANK YOU

References

1. Allyn, Bacon [Internet] 2008Available from :spot.pcc.edu/~gtinker/PSY_231/Chapter%204.ppt

2. Moore, KL. Clinically Oriented Anatomy 3rd Ed. Williams and Wilkins 1992

3. Guyton, Hall. Textbook of Medical Physiology 12th Ed. Saunders 2010