Jan 8.26

Anatomy & Physiology

Detachable Penis:

  • Argonaut Octopus: worm-like detachable penis, which can swim off alone to mate with females.

  • Males are 90% smaller than females: in hopes of surviving.

Penile Bones:

  • Baculum/ Penile Bone/ Os penis

  • Common amounst most mammals

  • Seen in some primates but greatly reduced among great apes.

  • Why not present in humans?

    • Common in animals (raccoon penis)

    • Need hydraulic pressure to bring out the Os bone (blood flow)

Diphallia- Double penis

  • 1 in 5-6 million births

  • Variations from partial to complete. True diphallia is very rare (~100 CASES worldwide).

  • Most are born with other congenital malformations (double: bladder, anus).

  • Semi functional

  • Usually taken care of at birth

Spiked Penises?

  • Spikes orient backwards (easy to go in but diffidult ot pull out)

  • Why?

    • In terms of a cat, the spikes would make the vaginal opening want to close, therefore, the male cat’s sperm would have a greater chance at sticking.

    • Similar story with the Eastern Red Bats.

Smooth Penises

  • Our closest living relative (99% shared DNA) - common bonobo chimpanzees have penile spines.

  • Likely vanished from our ancestors 800,000 years ago.

A Versatile Social Cue

  • Erect primate penises symbolize:

    • Male-male aggression

    • Marking territory

    • A sexual invitation

      • If viewed by a competing male may provoke an attack.

A Sign of Trust

  • Savanna baboons engage in the intense greeting of ‘diddling’: fondling the penis and scrotum, which puts one’s genitalia at risk of being seriously damaged by another male.

Human Average Penis

  • Length of flaccid Penis: 3-6 inches

  • Erect Penis: 4-8 inches (avg. 5.6”)

  • Diameter at Base: 1.5 inches

Penish Size: Growers vs. Showers:

  • Cylinders of the penis are a weave of elastin and collagen that, in combination, make the penis stretchy but strong.

    • Collagen: makes the penis tough/durable (like Kevlar)

    • ElastinL makes the skin elastic like a waistband.

    • Growers vs Showers look the same length erect

      • Growers: more elastin and less collagen in the penis

      • Showers: less elastin and more collagen.

  • Problems with measurement

  • A flaccid penis is not correlated with erect penis size (equalizing effect)

  • Height and penisle size (weak positive correlation)

  • Some evidence for ethic differences.

Does Size Matter?

  • The inner two-thirds of the female vagina expand during sexual arousal.

  • The outer third (closest to the vaginal opening) thickens, embracing the penis.

What a Girl Wants:

  • 26,437 sample women

    • 84% content with the size of the partner’s penis

    • 14% wanted it bigger

    • 2% wanted it smaller

  • 21% of sampled women consider penis length very important (girth was rated most important).

How Much Attention Do We Pay To Penises Anyway?

  • Content analysis of romance novels found that descriptive details of penises are rarely offered.

  • Eye-tracking study recorded men and women viewing non-erotic images.

Men are More Interested Than Women In Penises

  • Eye-tracking study recorded men and women viewing non-erotic images.

    • Men consistently directed their gaze to the male crotch

    • Females rarely did so.

Things That Affect Penis Size:

  • Temperature, Fear

  • Obseity

  • Perspective “perception shortening angle”.

Buried or Hidden Penis Syndrome

  • Present at birth (cogenital)

  • Develop later in life (adult acquired)

  • Not common

  • Typically associated with BMI > 40

  • Penis is typical in size and shape, but body tissues and folds of skin hide it:

    • Abdominal (lower belly) fat.

    • Fatty tissue surrounding your penis (mons pubis)

    • Fatty tissue in your upper thighs.

    • Fatty tissues in your scrotum (the sac behind your penis that normally holds your testicles).

  • It can lead to difficulty urinating, keeping the penis clean, and having sexual intercourse.

  • This can lead to inflammation or scar tissue as well as pain, odour and infections.

Treatment:

  • Counselling for anxiety, depression, and stress

  • Dieting

  • Surgery

    • E.g., liposuction, tummy tuck.

Increasing Penis Length

  • Cutting the suspensory ligament disconnects the mooring and extends 2 to 3cm (1 inch) longer in the flaccid state.

Increasing Penis Girth

  • Penile fat injections

Concerns about Size:

  • Sushruta Samhita (3rd-4th century AD)

    • “…through practice of getting the penis abnormally elongated by pricking the bristles of a water parasite (Suka) into its body… [and] a man who foolishly resorts to the practice of getting it abnormally elongated and swollen by plastering it with Suka and not in the usual official way.” (pp. 81)

    • Made an infection that creates a wart-like layer on top.

Penile Enlargement

  • With penis pumps or other cosmetic surgical techniques, injury is possible.

  • Surgery should not be considered unless the erect penis size falls below 2.8.”

  • Studies have found that post-operation, many men are unhappy with the results.

Small Penis Syndrome:

  • Body Dysmorphic Disorder (BDD)

    • Psychiatric disorder.

    • A preoccupation wiht an imagined defect of appearance with an imagined defect of appearance or an excessive concern over a physical anomaly.

    • Must cause clinically significant distress or impairment in social or occupational functioning.

  • People with BDD

    • May develop major depressive episodes

    • At risk of suicide

  • Treatment

    • Combination of cognitive-behavioural therapy and SSRIs (antidepressant meds).

    • Sex education with standard penile measurement.

Penile Shaft: Problems with Foreskin

  • Phimosis: too much foreskin

  • Paraphimosis: Not enough foreskin

    • When the foreskin is pulled back behind the head of the penis, it cannot be returned

    • The tight ring causes the rest of the foreskin to swell, compounding the problem.

    • If not corrected immediately progressive immediately progressive swelling and an enormous collection of fluid.

Penile Shaft:

  • Urethra:

    • Thin, unicellular walls approx. 8 inches

  • Corpus Spongiosum (spongy body): It contains the urethra, and at the tip, it enlarges to become the penile glans.

  • Corpora Canvernosa: cylinders that fill up with blood and stiffen

Hypospadiasis

  • The urethra is opening in the wrong spot

  • Very common (1 of 125 male births)

  • Surgically corrected

  • Genetic, environment (chemical disrupts hormone balance).

Scar Tissue on Penile Shaft

Peyronie’s Disease:

  • A flaccid penis looks normal

  • Upon erection penis curves dramatically

  • Caused by scar tissue

  • Treatment:

    • Surgery

    • Oral Medication: Increases collagen levels.

    • Physical Therapy: The use of ultrasound “extracorporeal shockwave therapy” has proven effective in reducing penile curvature and pain.

    • Low-dose radiotherapy: used for long-term painful Peyronie’s disease with good results; however, the risks of radiation exposure must be considered.

Erectile Dysfunction: Fracturing The Penis:

  • If an erect penis is suddenly bent, it can break just like a bone.

  • You may even hear a loud snap or tear.

    • The snapping noise is the fibrous tissue surrounding the penis.

  • Cause: strenuous intercourse.

Erections

  • An erection is a hydraulic event involving the vascular and nervous systems.

  • Possible within 10-15 seconds to:

    • Double in length

    • Become firm

    • Closing off the bladder so that semen and not urine pass

  • Nocturnal erections occur every ~90 minutes and generally during REM sleep.

Erectile Process:

  • Parasympathetic nerve endings release NO onto smooth muscle cells.

  • NO blocks calcium from entering and sweeps up calcium, allowing smooth muscle to relax and allowing blood to flow in.

Erection:

  • Nitric Oxide (NO)… a chemical gas… is released from nerve endings within the penis upon stimulation (sight, smell or erotic thought).

  • NO works on an enzyme within the blood vessels of the erectile tissues, causing cyclic GMP (guanosine monophosphate) to accumulate.

  • Accumulation of GMP causes calcium to leave the blood vessel walls, and they relax.

  • Blood fills the relaxed vessels, and they become engorged, causing them to act as a flap valve closing off the outflow of blood.

  • An erection is the result.

No Erection If You Have Too Little ‘NO"‘

  • Men producing too little amounts of NO will suffer from erectile dysfunction.

    • The small amount of cGMP they produce is broken down at the same rate and therefore doesn’t have the time to accumulate and cause a prolonged vasodilation effect.

Post-Erection:

  • The body releases the chemical:

    • phosphodiesterase-5

  • Which reverses the process… specifically, it reduces the accumulation of cyclic GMP and brings erection to an end.

Sildenafil (Viagra)

  • Viagra works by inactivating phosphodiesterase-5 (the erection ending chemical).

  • By inactivating the ‘inactivato.r’

    • NO lasts longer

    • More blood flows to the oenis

    • Allows and prolongs an erection.