Download Perineum Dr. B. Mantaring Outline General Features of the

Perineum
Dr. B. Mantaring
Outline
I.
II.
III.
General Features of the Perineum
Male Perineum
Female Perineum
*Some details taken from Trans 2008
I.
GENERAL FEATURES OF THE PERINEUM
Perineum and Boundaries of Perineum
- Narrow area between thighs and below pelvic outlet (levator ani)
- Separated from pelvic cavity by pelvic diaphragm (composed of levator ani and coccygeus muscles)
- Narrow diamond-shaped area
- Boundaries
o Anterior: pubic symphysis
o Anterolateral: inferior pubic rami and ischial rami
o Lateral: ischial tuberosities
o Posterolateral: sacrotuberous ligaments
o Posterior: sacrum and coccyx
- Consist of 2 triangles
o Urogenital triangle (superior)
 Enclosed by perineal membrane
 Components
 External genitalia
 Urethra
o Anal triangle (inferior)
 Open
 Components
 Anal canal
 Ischiorectal fossa
Perineal Membrane
- Thin sheet of fascia that covers anterior part of inferior pelvic aperture
- Stretches between two sides of pubic arch
- Perforated by the following – urethra in both sexes, vagina in the female
Superficial Perineal Fascia
- Fatty superficial layer
o Continuous with Camper’s fascia in abdomen
- Membranous layer (Colles’ fascia)
o Continuous with Scarpa’s fascia in abdomen
- Continuous with Dartos fascia of penis and scrotum
Superficial Perineal Space
- Potential space between superficial perineal fascia and perineal membrane
Male
Root of the penis
Bulb
Crura
Superficial perineal muscles
Female
Root of clitoris
Vestibular bulb
Crura
Superficial perineal muscle
Superficial transverse perineal
Bulbospongiosus
Ischiospongiosus
Branches of internal pudendal vessels
Branches of internal pudendal nerve
Proximal part of spongy urethra and scrotal contents
Superficial transverse perineal
Bulbospongiosus
Ischiospongiosus
Branches of internal pudendal vessels
Branches of pudendal nerve
Deep Perineal Space
- Space enclosed by the perineal membrane and inferior fascia of the pelvic diaphragm
- Contents of deep perineal space in males
o Membranous urethra
o Bulbourethral gland
o Urethral sphincter
o Dorsal nerve of penis
 From pudendal nerve
- Contents of deep perineal space in females
o Part of the urethra
o Urethral sphincter
o Dorsal nerve of the clitoris
Superficial Perineal Muscles
- Located in the superficial perineal space
- Innervated by the perineal branch of pudendal nerve
- 3 muscles
o Ischiocavernosus
 Males
 Covers the crus of penis
 Assists in erection
 Females
 Covers the crus of the clitoris
o Bulbospongiosus
 Males
 Muscles of the bulb of penis
 Empties residual urine or semen
 Assists in erection by compressing deep dorsal vein of penis
 Females
 Surrounds vaginal orifice covering the vestibular bulb
 Assists erection of clitoris by compressing deep dorsal vein
o Superficial transverse perineal
 Fe/males
 From ischial tuberosity and ramus
 Inserts into perineal body
Perineal Body
- Fibromuscular mass located between anal canal and vaginal orifice
- Contains the following
o Collagen and elastic fibers
o Skeletal and smooth muscle
- Wedge shaped fibrous tissue in the center of perineum
- Where several muscles converge
o Bulbospongiosus
o Superficial transverse perineal
o Levator ani
o External anal sphincter
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Important structure in childbearing women
Complications
o Cystocele
 Bladder herniating into the vagina due to a tear in the pubocervical fascia
o Rectocele
 Bladder herniating into the vagina due to a tear in the rectovaginal septum
Episiotomy
- Surgical incision to widen vaginal orifice during delivery
- Repaired by episiography
- Types
o Median cut
 Skin, vaginal mucosa, perineal body, superficial perineal muscle
 Danger of tearing external anal sphincter and rectovaginal sphincter, leading to continuation from
vaginal canal into anal canal
 Preferable if perineal body is long
 Recovery is faster
o Mediolateral cut
 Skin, vaginal mucosa, bulbospongiosus
 More difficult to repair, more bleeding due to presence of bulbospongiosus
Anal Triangle
- Boundaries
o Imaginary line joining the ischial tuberosities
o Tip of coccyx
o Sacrotuberous ligament
o Gluteus maximus muscle overlies it
- Contents
o Anal canal
o External anal sphincter
o Ischioanal fossa
Anal Canal
- Terminal and most inferior part of large intestine
- Begins where the rectal ampulla narrows at the level of the U-shaped puborectalis sling
- Surrounded by levator ani muscles
- Structures
o Anal columns (rectal columns of Morgagni)
o Anal valves
o Anorectal junction
o Pectinate line
 Indicates the junction of the superior and inferior half of the anal canal
 Superior half – endoderm, columnar epithelium
 Inferior half – ectoderm, stratified squamous
- Arterial supply of anal canal
o Superior rectal artery
 Supplies anal canal superior to pectinate line
o Inferior rectal artery
 Supplies inferior half of anal canal
o Middle rectal artery
 Form anastomoses with superior and inferior rectal arteries
- Venous drainage of anal canal
o Superior rectal vein
 Drains anal canal superior to pectinate line
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Inferior rectal veins
 Drains anal canal inferior to pectinate line
o Middle rectal vein
 Forms anastomoses with superior and inferior rectal veins
Lymphatic drainage
o Superior to pectinate line
 Lymph drains into internal iliac then to common iliac and lumbar lymph nodes
o Inferior pectinate line
 Lymph drains into superficial inguinal lymph node
Innervations
o Superior to pectinate line
 Inferior hypogastric plexus
 Sensitive only to stretching
o Inferior to pectinate line
 Inferior rectal nerves (branch of pudendal nerve)
 Sensitive to pain, touch, and temperature
Ischioanal Fossa
- Located between skin of anal region and pelvic diaphragm
- Apex: where levator ani arise from obturator fascia
- Base: formed by perianal skin
- Contents
o Ischioanal fat
o Pudendal canal
 Internal pudendal vessels – inferior rectal vessels
 Pudendal nerve
o Cutaneous nerves – perforating branch of S2 and S3
- Bounded by sacrotuberous ligament posteriorly, levator ani and anal canal medially, obturator internus laterally
- Obturator internus muscle covered by obturator fascia
o Splitting of fascia forms pudendal or Alcock’s canal on lateral aspect of canal
 Contains pudendal artery, vein, nerve
- Mainly contains fat (to allow for distention of rectum) aside from pudendal canal
Pudendal Nerve
- Responsible for innervations of perineum
- Branches
o Dorsal nerve to penis (clitoris) – sensory nerve
o Perineal branch – supplies UD(?) muscles; gives of scrotal or labial branches
o Inferior rectal nerve
- Pudendal block
o Injection of local anesthesia into tissues surrounding the pudendal nerve
o Block sensation in perineal area because perineal nerve is a terminal branch
o Bony landmark is ischial spine
o Can be used to repair lacerations in perineum, not to eradicate labor pains
II.
MALE PERINEUM
- Urethra
o Membranous
o Spongy
- Scrotum
o Develops from 2 outpocketings of anterior abdominal wall
o Skin is dark and wrinkled
o Layers of scrotum
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Testes
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 Skin
 Superficial fascia – Dartos fascia; contains thin sheet of muscle called Dartos muscle
United in middle by scrotal raphe
Covered externally by skin, followed by Dartos fascia and muscle
 Dartos muscle is responsible for temperature regulation of scrotal sac and testes inside to
facilitate spermatogenesis
Main male reproductive organs
Paired ovoid glands
Suspended in scrotum by spermatic cord
Descent of testes
 Abdominal organ in early gestation
 Descent of testes through inguinal canal into scrotum
Cryptorchidism – a condition where testes failed to descend; can result to male infertility or cancer
Abdominal muscles and coverings continue into the testes covering
Contents of Spermatic Cord
- Ductus deferens – lies in posterior part of spermatic cord
- Arteries
o Testicular artery
 Supply testes and epididymis
 Arise from aorta inferior to renal artery
 Anastomose with the artery of the ductus deferens
- Veins – pampiniform plexus; ends in testicular veins
o Pampiniform plexus is a venous drainage which also functions as part of thermoregulation
 Surrounds the testicular artery
 Drains into the testicular vein
 Varicocoele (“bag of worms”) – a condition that may develop when thermoregulation is no longer
effective; leads to increased temperature and eventually, infertility
o Testicular vein
 Left – drains to left renal vein
 Right – drains to IVC
- Nerves and lymph vessels
Epididymis
- Parts of epididymis
o Head – lobules which are coiled ends of the efferent ductules
o Body – consist of duct of epididymis
o Tail
- Functions
o Storage of sperms
o For maturation of sperms
Membranous urethra
- Shortest, thinnest and narrowest portion of urethra – sphincter urethrae muscle
- Located deep in perineal space
- Bulbourethral glands – located posterolateral of urethra
Penis
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Male organ of copulation
Common outlet for both semen and urine
Skin of penis consists of a root (radix) and body (shaft)
Outer covering of penis
o Deep fascia of the penis (Buck’s fascia)
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o Tunica albuginea
Erectile bodies
o Corpora cavernosa
 On dorsal or posterior side of penis
 Composed of two fused bodies
o Corpora spongiosum
 On ventral or urethral side of penis
 Contains spongy urethra
 Distally expands to form the glans penis
Cross-section
o Interlacing and intercommunicating spaces within erectile tissue
o Deep fascia of the penis (Buck’s Fascia)
 Common covering for the three erectile bodies
Root of penis
o Attached portion of penis
o Located in superficial perineal space
o Consists of the crura, bulb, and muscle covering it
Body of penis
o Free part of penis
o Has no muscle covering it except near the root of penis
o Glans penis – consists entirely of corpus spongiosum; higher concentration of sensory nerve endings
Arterial supply of penis
o Supplied by the internal pudendal arteries
 Dorsal arteries – supplies fibrous tissue around the corpora and penile skin
 Deep arteries – supply and enter erectile tissue
 Artery of the bulb of penis – supply posterior part of corpus spongiosum and Cowper’s gland
Venous drainage of penis
o Blood from cavernous spaces → venous plexus → deep dorsal vein → joins prostatic plexus
Innervations of penis
o Dorsal nerve of penis
 Branch of pudendal nerve
 Passes into the deep perineal space
 Runs in dorsum of penis lateral to the arteries
Erection
o Deep to helicine artery (define helicine artery) fills with blood after parasympathetic stimulation
o Engorged vessels cause turgid consistency
o Compression of venous plexuses by bulbospongiosus and ischiocavernosus impedes return of blood flow
Clinical considerations
o Hypospadia
 External urethral meatus opens on ventral aspect of penis
o Phimosis
 Prepuce or foreskin fits tightly over the glans and cannot be retracted easily
o Circumcision
 Surgical removal of the prepuce
Spongy urethra
- External urethral meatus – narrowest part of urethra
- Two expanded areas
o Intrabulbar fossa
o Navicular fossa
- Opening of ducts
o Ducts of bulbourethral glands
o Ducts of mucus secreting urethral glands
Rupture of Urethra
- Common site of rupture is in the bulb of the penis
- Secondary to straddle injury or incorrect passage of catheter into the urethra
- Extravasation of urine into the superficial perineal space
III.
FEMALE PERINEUM
Female Perineum
- Aka pudendum or vulva
- Female external genital organs
- Consists of the mons pubis, labia majora, labia minora, vestibule of the vagina, clitoris, bulb of vestibule, and
greater vestibular glands
Mons Pubis
- Rounded fatty elevation anterior to pubic symphysis
- Consists mainly fatty of connective tissue
- Becomes covered with hair during puberty
Labia Majora
- Two symmetrical folds of skin situated on each side of the pudendal cleft
- Anterior and posterior labial commissure
- Contains subcutaneous fat
- Homologous to scrotum
- Round ligament insertion
o Enters inguinal canal and attaches to the labia majora
o Homologous to the vas deferens
Labia Minora
- Folds of fat-free hairless skin located between labia majora
- Core of spongy tissue with blood vessels
- Encloses the vestibule of the vagina
- Clitoral hood or prepuce
- Frenulum of clitoris
- Union of two labia minora forms frenulum or fourchette
o Disappears after childbirth
Vestibule of Vagina
- Space between the labia minora
- Structures that open into vestibule
o Urethra
o Vagina
o Ducts of greater vestibular glands
External Urethral Meatus
- Located 2-3 cm posterior to clitoris
- Ducts of paraurethral gland (Skene’s glands)
o Open on each side of external urethral meatus
o Homologous to prostate
- May become easily infected
Vaginal Orifice
- Located inferior and posterior to urethral orifice
- Size and appearance varies with condition of hymen
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Hymen
o Fold of mucous membrane surrounding the vaginal orifice
o Should not normally fully cover the vaginal opening
o Amenorrhea – abnormal situation wherein hymen is absent and menstrual blood cannot flow out
Great Vestibular Glands/Bartholin’s Glands
- Located on each side of the vestibule
- Ducts open on each side of the vaginal orifice
- Secrete lubricating mucus into the vestibule during sexual arousal
- Homologous to bulbourethral glands
- Infection results in enlargement
Clitoris
- Located posterior to anterior labial commissure
- Parts of clitoris
o Crura
o Corpora cavernosa
o Glans
- Suspensory ligament
- Homologous to penis
o Prepuce of clitoris – homologous to male prepuce
o Frenulum of clitoris – homologous to male frenulum
- Composed of erectile tissue
- Highly sensitive to touch, pressure, and temperature
- Contains many nerve endings
Sexual Arousal
- Under parasympathetic stimulation
- Increased secretions from paraurethral glands and greater vestibular glands
- Erection of clitoris
- Enlargement of vestibular bulbs
Bulbs of Vestibule
- Two elongated masses of erectile tissue
- Lies along the side of the vaginal orifice
- Covered by bulbospongiosus muscle
- Homologous to bulb of penis
Urinary Tract Infection (UTI)
- Common in females usually due to hygienic practices (and structure of urethra and vagina)
- Easily treated with antibiotics
- If present in males, investigate the cause before treating
REMINDER
Coverage for first exam
- Gross anatomy and histology (male and female) lectures
- Anatomy lab and radiology
- GI Health and nutrition
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