human sexuality 1

history of research on human sexually

• 350 BC - Aristotles thinking of human sexuality - The female is, as it were, a mutilated male

• da Vinci & the origin of semen - many drawings of male anatomy

• mid 16 century - discovery of the clitoris - Renaldo Columbus

• mid- 17th century - microscope was invented - semen examined -  incorrectly described homunculus in sperm

• 19th century - theoretical idea of ovum

• 1886 deviations in sexual interests - fetishes - Richard von Krafft-Ebing

• 1896: Havelock Ellis published the first thorough study of homosexuality, presenting it an objective and not terrible light

• explanations of homosexuality - bio basis of sexual orientation - Freud & Hershfeild

• 1905 - X & Y chromosomes

• Margret Sanger -birth control]

• roe v wade & clinic 554

what was the vagina once considered due to lagging research

inverted penis

what did  Princess Marie Bonaparte do

• had inability to orgasm

• found correlation between ease of reaching an orgasm & distance between clitoris & vagina

• had her clitoris surgically moved closer to vagina - twice to increase likelihood of orgasm

• Vagina and clitoris = Closer together = more orgasm

Who’s is Alfred C Kinsey

• 1940s

• very popular guy that talked about sex - sex educator

Masters and Johnson - Exploring love, sexuality and well-being

• In the 1950s and 60s, Masters and Johnson did intensive laboratory experiments to measure sexual behavior.

• Had people have sex and measure physiological things - arousal, communication

• They had sex too!

• But also they engaged in conversion therapy to “cure” homosexuality.

Important methods of sexuality research

Case studies

surveys

Penile/vaginal plethysmograph

• RigiScan

experiments

Columbus Renaldo “discovery of clitoris”

described its erectile characteristics and its similarity to the penis, describing it as “pre-eminently the seat of women’s delight.”

who was spermatozoa first observed by

Ham and Hartsoeker

discovery of the anatomy of the clitoris

1998 Helen O'Connell true anatomy

case studies in sexuality research

important

• Double header: double dick dudes - diphalic dude book

• Male multiple ejaculatory orgasms

• Restless genital syndrome should be distinguished from spontaneous orgasms

Surveys in human sexuality

• National survey of sexual health and behavior - center for sexual health promotion 

  • Usually use massive surveys to pick apart data to find answers - to explore specific research question -

  • Used the results of three surveys, including the General Social Survey and one of their own, to examine the association between frequency of sex and relationship satisfaction. (total sample size > 30,000 people!

• More general social surveys like the General Social Survey also have items related to sexual behaviour and relationships.

• Self-report scales target more specific “constructs”

penile plethysmograph

developed by Kurt Freund in 1950s

• initially for identifying Czechoslovakian army recruits pretending to be gay…but, ultimately, a valuable research tool within sexuality research.

• measures penile pulse during erection & penile diameter

• color of penis measured w photoelectric plethysmograph

RigiScan

2020

new methods for the monitoring of nocturnal erections

• Used in predicting recidivism in adolescent sex offenders

what is done/used in experiments on human sexuality

• Vaginal/penile photoplethysmography

• Use Tissue color

• Use Temperature information - labial thermistor

• Meta-analysis - measuring physiological arousal while asking are you aroused

• Eye-tracking 

• Virtual reality erotica - porn on VR and look at sexual desire how integrated they were in the scene

• Neuroimaging technology (e.g., fMRI)

neuro-imaging experiments in human sexuality

revolutionary development - can see what's happening in different areas of brain during different aspects of sex

• The ventral striatum is a brain area linked to all kinds if addictive behaviors including psychoactive drugs

• Magnetic resonance

• People had sex in fMRI machine

in general what 2 areas are important in understanding human sexuality

evolutionary biology and psychology

• Kangaroos have 3 vaginas

• Female ducks have corkscrew vaginas

Anatomy of vulva

the external genital area

• Mons, Clitoral hood, clitoris, vestibule, perineum, anus outer labia, inner labia, urethral opening, vagina opening, openings of Bartholin's glands

• variation in vulva appearance and how that relates to self-perception, self-esteem, and cultural norms

what is a commonly missed term in woman’s anatomy

vagina

 the vagina is actually the canal and only internal not external

average appearance of labia

Labia minora length: 20-100mm

Labia minora width: 7-50mm

labia surgery

labiaplasty

vaginal tightening

labiaplasty

alteration of the labia (labia minora in most cases), is the most common genital cosmetic surgery among women

• barbie labiaplasty: fake ideal single line opening

• controversial topic within medical science

prevalence of labiaplastys

Overall increase includes a striking increase among young people including adolescents.

• Some link the rise in cosmetic labiaplasties (and, thus, labiaplasties overall) to cultural influences, specifically perceived cultural norms regarding appearance.

2 reasons woman seek out labiaplastys

1. Medical/function reasons

2. Cosmetic/psychological reasons

medical/ functional reasons for labiaplasty

most common

pain and discomfort associated with protruding labia minora

(avg: 2.8 +/- 1.8)

Chinese study: 38.4% of labiaplastys = functional discomfort

cometic/psychological reasons for labiaplastys

self esteem, perceived attractiveness

(avg: 3.2+/- 1.4)

Chinese study: 22.2% of labiaplasys = cosmetic + 4.2% = psychological

playboy effects

pornography effects

perceived norms

how has playboy effected cosmetic labiaplastys

analyzed Playboy photographs from a ~60-year period assessing trends in the visibility of breasts and pubic areas.

• Increased visibility of v-line = increase visibility of vulva

• They proposed that the increase in visibility of female genitalia, represented here in Playboy, has contributed to increases in cosmetic genital surgeries

how has pornography effected cosmetic labiplastys

There was an association between porn consumption (past 5 years) and openness to labiaplasty - though it wasn’t overwhelmingly strong, suggesting there are other factors.

• Pornography influences some woman to seek labiaplasty but relative to other motivating factors its role is minor

the effect of percieved norms on cosmetic labiaplastys

female participants viewed a series of photos of either

• a) non-modified vulvas

  b) modified vulvas,

  c) no photos (control).

• Then, each rated 10 non-modified and 10 modified vulvas.

  • The women who had viewed non-modified vulvas ranked those as being more ‘normal’ than modified vulvas.

  • For those who had viewed modified vulvas, the opposite was true. I.e., whatever they were exposed to, they deemed normal!

  • All women ranked modified vulvas as being closer to ‘society’s ideal’… this was more pronounced in those that had viewed the modified vulvas.

Research on  psychosexual outcome after labiaplasty - post surgical satisfaction

• Satisfaction: High

• Risk of complications = low

• Sharp et al. (2017) found that those with functional/sexual motivations for surgery were more likely to be satisfied with the results - In statistical terms, those motivations were better predictors of post-op satisfaction.

woman’s public hair norms for 18-24

Another aspect for which cultural norms have clearly been influential

• total removal: 58.5%, partial removal: 29.1% no removal 12.4%

pubic hair norms in Woman 25-49

Another aspect for which cultural norms have clearly been influential

• total removal 22.5%, partial removal: 49.7%%, no removal 27.8%

anatomy of the clitoris

glans and erectile tissue that leads to erection and to increased sensitivity in response to sexual arousal.

• Most of the clitoris is internal; the crura extend approximately three inches

• Clitoral stimulation is the most commonly perceived form of stimulation contributing to orgasm 

• Bonaparte: highlights importance of the clitoris

3 most commonly perceived form of stimulation contributing to female orgasms

1. clitoris stimulation

2. vaginal stimulation

3. cervical tapping

what is the g-spot

hypothesized to be an area of heightened sensitivity to arousal located on the front wall of the vagina.

• Critically, it often presented as the mechanism for orgasms that result from vaginal/penetrative intercourse.

• Different studies systematically agreed of the existence of the g-spot there is no proof, and no agreement on location, size or nature

anatomical evidence for vaginal orgasm

there is no anatomical evidence of the vaginal orgasm which was invented by Freud

• Bonaparte would agree that vaginal intercourse-associated orgasms occur to the degree that they also stimulate the clitoris

measurement for female sexuality

Female sexual function index: 19 items

• developed by Reed et al 2014

do woman believe in the g-spot

• About half the female participants in this study believe that the G-spot exists.

  • Higher rate of belief among those report higher arousal rates

• 2012 study: 83-year-old female cadaver and claims to have, for the first time, documented its anatomical existence, characterizing it as a neurovascular bundle.

• In 2023: many believe g-spot is an idea formulated to more strongly link female orgasm to vaginal intercourse (an therefore reproduction) and have it less associated with pleasure on its own)

Female genital mutilation

Female genital cutting, sometimes referred to as female genital mutilation or female circumcision.

• At  least 200 million woman and girls have undergone FGM in 30 countries where representative data is available

• In most of these countries the majority of girls were cut before age 5

• Human rights concern - concern of world health association

• Concentrated in certain areas of world and associated with different religious & cultural differences

• Mali passed laws against FMG around 1997 - large decrease in FMG practices

types of female genital mutilation

Type 1: clitoridectomy

Type 2: excision

Type 3: infibulation

Type 4: All other procedures

Type 1: clitoridectomy

• partial or total removal of the clitoris (a small sensitive & erectile part of female genitals) and in very rare cases, only the prepuce (the fold of skin surrounding the clitoris)

• Extremely painful & distressing, damages sexual sensitive skin and  is an risk for infection

Type 2: excision

partial or total removal of the clitoris and the labia minora with or without excision of the labia majora (the labia are the libs surrounding vagina)

• Extremely painful & distressing, damages sexual sensitive skin and  is an risk for infection

Type 3: infibulation

narrowing of the vaginal opening through the creation of a covering seal

• the seal Is formed by cutting and sewing over the outer labia with or without removal of the clitoris or inner labia

Type 4: All other procedures

includes all other harmful procedures to the female genitalia for non-medical purposes - pricking, piercing, incising, scraping, cauterizing the genital area

effects of female genital mutilation

studies have found psychological effects including post-traumatic stress disorder and affective disorders that include anxiety, depression, and phobia.

• 44.3 PSTD 33.57 depression 21.61 self esteem - much higher than those uncircumcised

• Association between lifetime trauma and PTSD symptoms is stronger in those with more severe procedures. I.e., greater vulnerability

• associated with an elevated stress response measured via cortisol

female genital anatomy

• The introitus (entrance to vagina)

• Annular hymen

• Septate hymen

• Cribriform hymen

• An imperforate hymen

• The clitoris

The introitus

entrance to vagina

• is initially covered by the hymen, a membranous fold of skin that varies in structure, usually with some sort of opening for menstruation / tampons.

An imperforate hymen

hymen which lacks openings and thus interferes with menstruation, requires surgical intervention.

long standing belief about hymens

the state of the hymen is an indicator of one’s virginity

• not correct but holds strong with serious implications within some cultures.

• Virginity testing: a white bedsheet - a bride wedding night

• Hymen can be broken by many things

hymenoplasty

reconstruction of the hymen

The clitoris

• pre-eminently the seat of women’s delight.” -Renaldo Columbus

• erogenous zone - areas associated with sexual arousal/pleasure

nerves in the clitoris

10,280!

• The dorsal nerves of the clitoris, branching off the aforementioned pudendal nerve, are thought to be the key sensory nerve tissue associated with arousal.

• Just like any other sensory information, stimulation of the clitoris leads to a signal being created and sent to the brain and researchers have used fMRI to determine the exact part within the brain where the sensory info is received and processed

vaginal photoplethysmography.

vasocongestion and engorgement of the genitals is what causes the color change detectable

history is female sex research

the finding of 10,280 nerves in the clitoris

vaginal photoplethysmography

Laser imaging, a fancier approach from a recent study

transudation of fluid"

Studies typically measure lubrication using litmus paper.

transduction of fluid

Arousal also causes vaginal lubrication, primarily via passage of fluid from Bartholin’s glands through the vaginal wall

• Studies typically measure lubrication using litmus paper.

the breasts in human sexuality

Like other aspects of sexual anatomy (in both women and men), size and other breast characteristics can be a source of anxiety and an influence upon self-perceived attractiveness and self-esteem

woman vs men breast satisfaction

woman are usually harder on self & less satisfied then there partners - woman typically desire to have larger breasts

• Self esteem studies pre & post breast augmentations

is there specialized innervation of nipples

there is no specialized innervation of nipples

• there is however greater sensitivity

Skene's gland

The Skene’s glands, are one of the many proposed physical identities of the G spot.

• homologous to the male prostate

• also known as the paraurethral or vestibular glands

• key to female ejaculation

Shubach 2001 - Skenes gland

demonstrated by recruiting squirters and carefully collecting two distinctly different fluids during orgasm

• a phenomenon that is not the same as squirting - low volume (pearly) ejaculate emerged outside the catheter and was probably secreted by the skenes glands

•  high volume (watery) ejaculate emerged via the catheter from urine from bladder 

are female ejaculaton ad squirting the same thing

2 different phenomenon's

• The real female ejaculation = low volume (pearly) very scanty, thick and whitish fluid 

innervation of penis

The penis and especially the glans is heavily innervated by dorsal nerves of the penis.

• sexual stimulation of the genitals results in signals going to the brain

• yet, physical genital arousal (erection) is to a good degree a spinal reflex

physiology of erection

Sensory info from the glans travels via sensory nerve fibers (dorsal nerves of the penis) to the spinal cord.

• They synapse, via interneurons, with output neurons, which travel back towards the genitals via the parasympathetic nerve fibers to the erectile tissue.

• The erectile tissue is also innervated by sympathetic nerve fibers

what is the state of the penis controlled by

sympathetic and parasympathetic signals that oppose each other.

• The flaccid state

• The erect state

• The key consequences of these different activations relates to the state of the arterioles and veins

The flaccid state

actively maintained by sympathetic nerve fibers that release the neurotransmitter norepinephrine

the erect state

the parasympathetic nerve fibers (reflex) release nitric oxide and acetylcholine

• sympathetic activity decreases

penis state & state of the arterioles and veins

When PNS is winning, the open arterioles allow an influx of blood while the occluded veins keep it from leaving. The blood fills the space and loses it oxygen, turning purple (a visible color change)

vasocongestion

associated with erection causes a pressure increase that induces higher transudation of fluid from Bartholin’s gland,

• i.e., lubrication!

Can you get turned on / hard / wet by just thinking about something?

nocturnal erections/orgasms/emissions are great example of the power of the mind

• circling back even further, sexual stimulation does go beyond the spinal cord and reach the brain, so… it’s complicated

hydraulic mechanism of penis erection

Muscle activity mirrors blood flow, under control of the same opposing forces

• contraction of the bulbospongiosus and ischiocavernosus muscles makes the glans bigger and, for males, pulls the penis upwards.

steps of an erection

1. Stimulation on the genital skin

2. Activation of sensory fibers in the punendal nerve

3. Signals pass to the dorsal horn of the sacral spinal cord

4. Activation of interneurons

5. These in turn activate motor neurons in a portion of the ventral horn know as Onufs nucleus

6. The motor neuron axons pass on through the pudendal nerve and innervate the bulbosongious muscles, similar  reflexes involve the ischicavernousus 

7. When the muscles contract, they pull of and squeeze the corpus spongiosum and corpora cavernosa causing the penis to stick out from the body and become more engorged

8. The erect penis can be moved voluntarily by contraction of these same muscles

timespan of erections

should not last more than a couple hours

Priapism = Erection lasting more than a few hours - it can cause tissue damage.

• It can happen in both men and women

treatment for priapism

Norepinephrine given to relieve pain 

• Treatment may involve

  • administration of norepinephrine

  • draining of blood from the penis using a needle.

Spermatogenesis

occurs within the seminiferous tubules of the testis and sperm become more concentrated and mobile as they pass through the epididymis (over the course of a week)

traveling of sperm

Sperm travels up the vas deferens towards the ejaculatory duct, with additions (seminal plasma) from the prostate gland and seminal vesicle, which contributes most of the volume of the semen that will be ejaculated.

• During the 2-3 second emission stage, all the components of semen merge and are loaded into the urethra.

• The bulbourethral gland produces a clear mucus (pre-cum) that is often emitted earlier during sexual arousal

• After that, ejaculation is mostly inevitable, and results from contraction of the urethra and assorted pelvic muscles.

• Contractions – and their associated ejaculations – occur once every 0.8 seconds or so

• The refractory period

how much sperm is in semen

semen ends up being only 1% sperm

• the other stuff serves various functions. E.g., fructose for energy, buffers to keep pH alkaline, ascorbic acid for antioxidant protection. Things required for the journey.

the refractory period

happens in males may relate to feedback mechanisms involving systems or from the release of hormones such as oxytocin (love hormone)

• it remains somewhat unclear

• Typically, the urethral sphincter closes during this period (this is why they don’t pee and cum at same time)

what happens is the urethral sphincter doesn’t close during refractory period

semen may enter the bladder rather than being ejaculated. Sometimes experienced as a dry orgasm

what is the male bulbourethral gland homologous with in females

Bartholin gland

• vaginal lubrication

semen quailty

Semen quality = sperm count

varies inversely with scrotal temperature.

Ideal range is 4 – 7 degrees below body temperature (37).

how does body regulate sperm tempurature

There’s a fine balance of involuntary muscle control that keeps the testes – and sperm – at an ideal temperature.

• The cremaster muscles contract to lift the testicles closer to the body.

• The dartos muscles contract to make the scrotal skin more wrinkly, reducing heat loss.

are sperm counts declining? why

last few decades have featured abundant research (and some debate) over the possibility of declining sperm counts (and quality/mobility

• One study documented tight-fitting underwear as a cause of higher scrotal temperatures, which lead to lower sperm quality and fertility

• Another oft-discussed culprit is exposure to electromagnetic radiation through the use of laptops, phones,

• Change over 11 years in sperm count - all counts went down - declining sperm counts

• sedentary lifestyle is also a factor.

circumcision

Non-surgical techniques such as PrePex are prominent in relation to adult circumcision, increasingly common in some African countries.

Surgical techniques = Gomco clamp

• circumcision is thought to date back at least 15,000 years!

• In Canada, the prevalence of newborn circumcision is about 32%.

Steps of PrePex circumcision

non surgical technique

1. Make the circumcision line based on WHO guidelines

2. Place the placement ring at the base of penis

3. Insert the inner ring onto the foreskin

4. Align the elastic ring with the inner ring

5. Release the elastic ring onto the inner ring

pros of circumcision

• Reduced occurrence of UTI - evidence supports

• some protection against certain STIs (including HIV) - evidence support - might contribute to a reported lower rate of prostate cancer.

• Some protection against cervical cancer (in female partners)

• Less smegma

cons of circumcision

• Possible hemorrhage

• infection

• damage - deformation - cut of the gland

• Deaths occur, though usually not with sanitary conditions

• Sensitivity is reduced…. or is it?

circumcisions affect on sensitivity

People have believed sensitivity is decreased with circumcision

• recent study assessed sensitivity in circumcised and uncircumcised men.

• They found no difference.

Is circumcision an adverse childhood event

Different attachment style if circumcised or not

• Higher anxious and avoidant attachment if circumcised

• Sensation seeking behavior in circumcised 

Penis Diorders

Pyronnies disease

Dorsal Pyronnies plaque

Balanitis

Phimosis

Paphimosis

Pyronnies Disease

excessive curvature is caused by the formation of plaques that result from inflammation within the penis.

The causes are not fully clear, although physical trauma seems to be one

• Fibrous plaque on corpus restricts symmetrical erection - acts like a tether causing curvature

• Firm outer casing where plaque forms

Dorsal pyronnies plaque

Plaque located within tunica albuginea

• in Peyronie’s disease, excessive curvature is caused by the formation of plaques that result from inflammation within the penis.

• The causes are not fully clear, although physical trauma seems to be one.

Balanitis

involves inflammation of the glans area due to infections and buildup of environmental substances.

• Associated with poor hygiene; more common in uncircumcised males.

Phimosis

The foreskin cannot be retracted over the glans.

• Common in childhood, rare in adulthood.

• Causes include skin conditions and infections (e.g., UTIs, yeast infections)

Paraphimosis

Trying to deal with phimosis can lead to paraphimosis, as can infections and physical trauma.

Possible results: swelling and necrosis (cell death)

Treatment for penis disorders

One effective treatment is Collagenase clostridium histolyticum (Xiaflex), an enzyme that breaks down the collagen plaques.

• Collegen

average penis size

14 cm - 5.5 inches

are shoes size and penis size correlated

the supposed association of penile length and shoe size has no scientific basis

Micro-penis:

Stretched penile length of 2.5 or more standard deviations below mean penile length.

• Works out to a bit under 3 inches.

• Buried penis can result from excessive fatty tissue.

does penis size matter?

Association between penis size and self-rated attractiveness

• Overall, way more women (85%) were satisfied with their partner’s penis than were the males themselves (55%).

• researchers frequently employ the recently developed Male Genital Self-Image Scale

• Loehle et al. (2017) found genital self-image significantly associated only with other issues related to self-perception

• Body image = highly associated genital satisfaction/self image

• Some studies, have found evidence supporting an effect of porn on genital dissatisfaction.

Does underestimated size effect erectile function

erectile disfunction did not vary with actual penis length but was associated with perceived small penis