Male Sexual Anatomy, Physiology, and Response

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Male Sexual Anatomy, Physiology, and Response
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Male Sex Organs

• Sex organs serve a reproductive function
• Also serve other functions
• Bringing pleasure to self
• Giving pleasure to others
• May serve to attract potential sexual partners
• Sharing of genital sexuality can play a bonding
  role in relationships

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External Structures

• Penis, Scrotum

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The Penis

• Penis from Latin word for tail
• organ through which sperm and urine pass
• Contains urethra for urine and semen transport
• Becomes erect to better penetrate the vagina and
  deposit sperm near the os
• No bone, little muscle

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The Penis

• Myths about the penis abound
• Penis size not linked to body size or weight,
  muscular structure, race or ethnicity or sexual
  orientation. Determined by heredity.
• No relationship between penis size and ability to
  have sexual intercourse or satisfy a partner.

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The Penis

• Three main sections
• Root attaches penis within the pelvic cavity
• Shaft body of the penis (hangs free)
• Contains 3 parallel columns of erectile tissue
• corpora cavernosa 2 columns along the front
  surface
• corpus spongiosum runs beneath corpora
  cavernosa, also forms the glans

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The Root of the Penis

• Extends into the body below the pubic bone
• Attached to internal pelvic muscles and can be
  felt in the perineum

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• Figure 6.1 The internal structure of the penis.

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The Penis Cross-Section of the Shaft
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The Penis

• Glans penis head of penis most sensitive
• Corona rim at base of the glans
• Frenulum on underside of penis triangle of
  sensitive skin attaches glans to foreskin.

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The Penis

• Foreskin sleeve-like covering of the glans
• Often surgically removed in infancy circumcision
• Crura (pl.) formed by the corpora cavernosa
  anchored by muscle to public bone
• Urethra a tube that transports urine semen
• Runs from bladder through penis. Opens at tip of
  glans.
• When penis erect, urinary duct is blocked

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• Figure 6.2 The male reproductive organs.

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The Scrotum

• Scrotum a pouch of skin that holds the two
  testicles
• Scrotum skin more heavily pigmented
• Sparsely covered with hair
• Divided in the middle by a ridge of skin
• During sexual arousal or cold conditions, scrotum
  retracts to keep testicle temperature consistent
  (about 93F) Cremaster muscle moves the scrotum
  closer to or farther from the body (protects)

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Internal Structures

• Testes
• Two major functions sperm and hormone production
• Shaped like olives 1.5 long and 1 diameter.
• Size and weight decrease as men age
• Not usually symmetrical in the way they hang
• Suspended by spermatic cord
• Within each testicle, there are about 1000
  Seminiferous tubules tiny compressed tubes 1-3
  feet long
• Production of sperm takes place in these tubes

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Internal Structures Cross-Section of a Testis
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Internal Structures

• Epididymis Vas Deferens
• The ducts that carry sperm from testicles to
  urethra for ejaculation
• Sperm mature in epididymis, which joins with vas
  deferens
• Vas deferens joins the ejaculatory duct within
  prostate gland
• Vas deferens can be felt within scrotal sac

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Internal Structures

• Seminal vesicles
• Secrete fluid that makes up 60 of semen
• Prostate gland
• Secretes fluid that makes up 30-35 of semen
• Can be stimulated in anal play
• Cowpers (bulbourethral) glands
• Secrete thick clear mucus prior to ejaculation

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Male Sexual Physiology

• Reproductive processes of the male body include
• production of hormones
• production and delivery of sperm

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Male Reproductive Hormones

• Testosterone
• Acts on seminiferous tubules to produce sperm
• Regulates sex drive
• Is responsible for development of secondary sex
  characteristics in puberty
• Influences growth of bones and muscle mass
• May affect personality

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Testosterone Production

• Testosterone is the most important male hormone
• Interstitial, or Leydig, cells in the testicles
  produce testosterone out of cholesterol

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Testosterone Fluctuations in a Day
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Spermatogenesis

• Ongoing process from puberty onward
• Sperm produced within seminiferous tubules of
  testicles (64-72 days)
• Several 100 million sperm produced daily
• 20 days for sperm to travel through epididymis
• During this time they become fertile motile
• Upon ejaculation, sperm expelled through urethra
  by muscular contractions

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Spermatogenesis

• Seminiferous tubules produce and store sperm
• Sertoli cells (in the tubules) provide nutrition
  for the development of sperm
• This process begins with spermatogonium on the
  outer wall of the tubules they move toward the
  center during development as primary
  spermatocytes, then divide to form secondary
  spermatocytes, and divide again into spermatids

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Spermatogenesis (Cont.)

• Spermatids form the compact head covered by an
  acrosome that contains enzymes to penetrate the
  egg
• The midpiece is formed and serves as the energy
  source
• The flagellum propels the mature sperm
• Sperm production takes 72 days, but is constant
  and each male produces about 300 million sperm a
  day

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• Figure 6.5 Spermatogenesis is continually taking
  place with various levels of sperm development
  throughout the testis.

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Spermatogenesis

• Immature sperm travel from the tubules to the
  epididymis organ that rests atop the testicle
• Old and faulty sperm are reabsorbed here
• They mature in 10-14 days in the epididymis
• Upon maturity they are transferred to the vas
  deferens for storage

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Male Sexual Response

• Erection
• Blood vessels expand and increase blood in penis
• Veins that normally carry blood out are
  compressed, leading to engorgement of penis
• Secretions from Cowpers glands appear at tip

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The Ejaculatory Pathway

• Ejaculation physiological process where seminal
  fluid is powerfully expelled from the penis
• Pathway organs
• Vas deferens
• Seminal vesicles
• Prostate gland
• Cowpers glands

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Ejaculation

• Begins in the spinal cord once a threshold is
  reached, and proceeds until the conclusion

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Ejaculation (Cont.)

• Once the threshold is reached
• Epididymis, seminal vesicles, and prostate empty
  their fluids into the urethral bulb
• A sphincter closes off the bladder
• 5-15 contractions at the base of the penis
  squeeze the urethral bulb
• Ejaculate is expelled
• Orgasm
• Return to flaccid state

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Ejaculation Orgasm

• Emission stage
• Sperm sent into vas deferens
• Rhythmic contractions begin
• Feeling of ejaculatory inevitability
• Expulsion stage
• Rapid contractions
• Semen spurts from urethral opening
• Orgasm
• Intensely pleasurable physical sensations that
  usually accompany ejaculation
• Followed by refractory period

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Ejaculate/Semen

• 2-5 milliliters of fluid
• 50-150 million sperm per milliliter
• Few sperm reach the ovum
• Sperm work together in order to fertilize the egg
• Semen coagulates upon ejaculation this helps it
  remain in the vagina and travel into the uterus
• 5-20 minutes later it thins out

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The Breasts and Anus

• Male anatomical structures that do not serve a
  reproductive function but may be involved in
  sexual activities include
• Breasts
• Urethra
• Buttocks
• Rectum
• Anus

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The Male Maturation Cycle

• Male puberty
• Andropause

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Male Puberty

• Around 10 years of age, the hypothalamus starts
  to release gonadotropin releasing hormone (GnRH)
  which signals the pituitary to release FSH and LH
• At the testes, LH stimulates testosterone
  production the two combine and FSH stimulate
  sperm production (around 12 years)
• Negative feedback loop

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• Figure 6.6 The cycle of male hormones.

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Male Puberty (Cont.)

• Many organs and glands increase in size
  testicles, penis, epididymis, prostate, seminal
  vesicles, Cowpers glands
• Growth spurt initiated by testosterone levels
• Testosterone and DHT develop the secondary sex
  characteristics larger muscles and bones, pubic
  hair, thick and tough skin, deep voice, facial
  and chest hair, increased sex drive

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Andropause

• Testosterone levels decrease about 1 per year
  after 40 years of age
• In the 70s and 80s, andropause occurs
• Andropause symptoms decreased spermatogenesis,
  thinner ejaculate, less ejaculatory force, libido
  decreases, fatigue, mood disturbances, decreased
  strength
• Controversy over hormone treatments

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Male Reproductive and Sexual Health

• Diseases of the male reproductive organs
• Other conditions that affect the male
  reproductive organs
• Cancer of the male reproductive organs

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Diseases of the Male Reproductive Organs

• Cryptorchidism testes do not descend into the
  scrotum surgery necessary to correct

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Male Reproductive and Sexual Health

• Diseases of the male reproductive organs
• Other conditions that affect the male
  reproductive organs
• Cancer of the male reproductive organs

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Diseases of the Male Reproductive Organs

• Cryptorchidism testes do not descend into the
  scrotum surgery necessary to correct

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• Figure 6.7 Although the testicles of a fetus
  begin high in the abdomen, they must descend into
  the scrotum during fetal development. If they do
  not, the male may become infertile.

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Diseases of the Male Reproductive Organs

• Testicular torsion testis is twisted on its
  spermatic cord many causes (sex, exercise,
  sleep) symptoms are pain and swelling immediate
  surgery is required to maintain the testicle

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• Figure 6.8 Testicular torsion can occur after
  exercise, sexual intercourse, and even while
  sleeping.

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Diseases of the Male Reproductive Organs

• Priapism persistent, painful erection not
  related to sexual excitement blood is trapped in
  erectile tissue common causes are drug use and
  unknown treatment is cessation of drug use and,
  possibly, surgery
• Peyronies disease painful curvature of the
  penis making penetration impossible cause is
  unknown may disappear within 2 years, or require
  drugs or surgery

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Other Conditions that Affect the Male
Reproductive Organs

• Anabolic-androgenic steroid use synthetic
  testosterone can increase muscle mass and
  endurance there are also numerous physical,
  psychological, and emotional side effects,
  including erectile problems

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Other Conditions that Affect the Male
Reproductive Organs (Cont.)

• Inguinal hernia intestine goes through an
  abdominal opening into the scrotum, creating a
  bulge can be due to heavy lifting and straining
  surgery may be required
• Hydrocele fluid accrues forms a scrotal mass

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Cancer of the Male Reproductive Organs

• Testicular
• Penile
• Prostate

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Testicular Cancer

• Most common cancer in men 15-44 years
• Few early symptoms, early detection important
  testicular self-exam
• Symptoms painless mass or hardness in the
  testes pain or increase in size of the testes,
  lower back pain, gynecomastia, shortness of
  breath, urethral obstruction
• High cure rate radiation, chemotherapy, removal
  of testicle

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Penile Cancer

• Lesions on the penis may be benign or malignant
  and are usually treatable may also be a STI
• Penile cancer is not common

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Prostate Cancer

• Prostate glands enlarge with age and this is
  typically unproblematic, other than interfering
  with urination
• Prostate cancer is one of the most common in
  American men, typically in men over 50 years
• Risk factors age, high fat diet, race, genetics
• Symptoms pain in the lower back, pelvis, or
  upper thigh, and urinary abnormalities
• Detected through rectal exam and blood test

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Prostate Cancer (Cont.)

• Treatments watchful waiting, radical
  prostatectomy, radiation, cryosurgery, drugs that
  attack cancerous cells