Anatomy of Faecal continence Flashcards
What are the anatomical requirements and innervation needed for faecal continence?
- A holding area- rectum
- Normal visceral afferent nerve fibres
- Functioning muscle sphincters
- Normal cerebral function
The pelvic cavity lies between the _ and _
Pelvic inlet and Pelvic floor
Rectum is found withiin the pelvic cavity
Openings in the pelvic floor allow structures to move from the pelvic cavity into the _
Perineum
The sigmoid colon becomes the rectum anterior to _, also known as the _ junction.
S3
Recto-sigmoid
Rectum becomes the anal canal anterior to the tip of the coccyx. T/F
True
The walls of the rectal _ can relax to accomodate faecal matter.
Ampulla
What are the pouches found in the rectum in males and females?
Males- Rectovesical pouch
Females- Rectouterine and vesicouterine pouch
What anterior structures are found to the inferior rectum
Males- Prostate gland
Females- Vagina and cervix
Which muscle forms most of the pelvic diaphragm?
Label the muscle parts.
Levator Ani muscle- forms most of the floor of the pelvis and the roof of the perinuem.
The levator ani muscle is tonically contracted. T/F?
The ani muscle reflexively contracts further with increase in intra-abdominal pressure. T/F?
The levator ani muscle must _ to allow defecation.
True
True
Relax
Puborectalis is a part of the Levator ani muscle. What is its signifance?
Skeletal muscle- Under voluntary control
Anorectal angle reduced when it contracts, acts as a sphincter
When the rectal ampulla is relaxed and filled with faeces, contraction of the Puborectalis maintains continence
What are the two types of anal sphincters?
Internal & external
Internal- smooth
External- skeletal
Main differences between the muscle of the two anal sphincters?
Internal
- Smooth muscle
- Superior 2/3rds of anal canal
External
- Skeletal muscle
- Inferior 2/3rds of anal canal
Contraction in the Internal sphincter is stimulated and inhibited by the _ and _
Contraction in the external sphincter is stimulated by the _ nerve.
Internal = Contration stimulated by Sympathetics and inhibited by Parasympathetics
External = Contraction stimulated by the Pudendal nerve
The internal sphincter is contracted all the time and relaxes as a _ action, in response to distension of the rectal ampulla.
The external sphincter is _ contracted in response to rectal ampulla distension and internal sphincter relaxation.
Reflex
Voluntarily
What is the difference in nerve supply between the pelvis and the perinuem?
- Pelvis- Smpya, parasympa & Visceral afferent. Supplies body cavity.
- Perineum- Somatic & Motor sensory. Supplies body wall
What are the two important levels from which the nerves innervate the rectum/anal canal?
- T12-L2
- S2-S4
S2,3,4 KEEPS YOUR GUT OFF THE FLOOR
The Sympathetic nerve fibres which supply the _ anal sphincter, arise from which level of the Spinal cord?
T12-L2
The parasympathetic nerve fibres supplying the internal anal sphincter arises from which spinal cord level? What is its effect?
S2-S4
Inhibits anal sphincter- Stimulates peristalsis
The visceral afferent nerves run back to which level of the spinal cord?
S2-S4, Runs along parasympathetics
Somatic motor sense from the pudendal nerve and the “nerve to levator ani” leave at which levels? What are their effects?
- S2-S4 and S3-S4 respectively
Effects- Contraction of external anal sphincter and puborectalis
The pudendal nerve supplies which sphincter in the rectum?
External anal sphincter
When can the pudendal nerve or the anal sphincter get damaged?
During labour- damage to pudendal nerve
Fibres of levator ani or external anal sphincter damage- Weakened muscle
What is the significance of the Pectinate line?
The arterial, venous, lymphatic and nervous supply is very different above and below the Pectinate line-
The line is a junction between the part of the Embryo which formed the GI tract- Endoderm, and the part that formed the skin- Ectoderm
