Lecture 9: Perineum Flashcards
What structures form the pelvic outlet?
- Pubic symphysis
- Ischiopubic ramus
- Ischial tuberosity
- Sacrotubous ligament
- Coccyx
What are the three major divisions of the levator ani? and what nerves supply it?
- Ischiococcygeus
- Iliococcygeus
- Pubococcygeus
Pudendal nerve (S2-4) Levator ani nerve (S3-4)
What can the pubococcygeus be further divided into?
Puborectalis (sling around rectum)
Levator prostate
Where is the iliococcygeus located and what does it do? and again what are them nerves?
Attatches to fascia of obturator internus, prevents prolapse of pelvic viscera
Pudendal nerve (S2-4) and n. to levator ani (S3-4)
What is the perineal body?
What we classically think is the perineum
- Composed of fibrous CT
- Attaching: Levator ani, bulbospongiosus, external anal sphincter, perineal muscles
At what point does the rectum become the anal canal?
When rectum pierces the pelvic floor it becomes the anal canal
What is the anal canal and what are some distinguishing features?
Transitional region b/w true gut and outer skin
Features:
- Pectinate line / anal columns
- Ext. anal sphincter
- Hiltons white line
What is the external anal sphincter and what is it attached to? what innervates it?
- Skeletal muscle
- Attached b/w perineal body to anococcygeal ligament (ACL)
- Closes anus (rectal control aided by puborectalis)
- Pudendal nerve (S2-4) -> inf. rectal branch
What are the landmarks of the anal triangle?
- Ischial tuberosity (laterally)
- Coccyx (posteriorly)
- Perineal body
Be wary of the lateral apex….
What could be an issue with ischioanal ulcers?
- Hitting pudendal nerves/vessels may lead to impotence of incontinence
Thus surface anatomy is important
What is the function of the perineal membrane in the urogenital triangle?
Support urogenital organs esp. at site of urogenital hiatus in levator ani muscle.
What structures exist in the deep perineal pouch for males?
- Membranous urethra
- Bulbourethral glands
- Dorsal nerves and arteries of the pneis
What structures exist in the deep perineal pouch for females?
- Vagina
- Compressor urethrae and urethrovaginalis muscle
- Dorsal nerves/arteries of the clitoris
NB: Greater vestibular glands are in the superficial pouch
What is the superficial perineal pouch?
Structures b/w perineal membrane and the skin
What structures are found in the superficial perineal pouch?
- nerves and vessels
- Erectile tissues
- Perineal muscles
- Greater vestibular glands (females only)
For males how does the fascia of the genitals communicate with other structures in a trauma sense?
Scarpas fascia of the abdomen is continuous with dartos fascia of the penic/scrotum which is continuous with perineal (colles) fascia.
This means that trauma here can result in blood pooling elsewhere.
What are the main branches of the internal pudenal art. in males?
- Inf. rectal
- Perineal
- Dorsal art. of penis
What are the main branches of the internal pudenal art. in females?
- Inf. rectal
- Perineal
- Dorsal art. of clitoris
Describe the process of defaecation, muscles and nerves involved:
- Relaxation of puborectalis (pudendal and n. to lev ani) to straighten anorectal angle
- Relaxation of sphincters (internal = PNS via Pelvic splanchnic, External (pudendal, conscious))
- PNS pelvic splanchnic causes contraction of rectal muscles
- Increased abdo pressure via abdo wall and diaphragm contraction. Stabilised by closure of the larynx
Describe Micturation (urination) // sacral stretch reflex:
ANS mostly:
- PNS (pelvic splanchnic) -> sacral spinal reflex results in detrusor muscle contraction
- SNS (L1-2 fibres) contracts internal urethral spincter (PNS overcomes this to cause relaxation)
- Somatic -> Pudendal, external urethral sphincter relaxation
- CNS can facilitate or inhibit.
What are the nerves involved in sex?
- PNS: Pelvic splanchnic from inf. hypogastric plexus. (vasodilation and thus erection)
- SNS: From ingerior hypogastric plexus; Ejaculation (SM contraction) and contraction of internal urethral sphincter (prevents backflow into bladder)
- Pudendal nerve; Sensory of penis or clitoris and cyclical contraction in orgasm
What can pudendal nerve damage/entrapment result in?
- Pain
- Numbness
- Altered sensation of ejaculation
- Fecal incontinence
- Urinary incontinence
Describe the determatomes of the perinium
Draw a diagram relating all the compartments of the pelvis
