Fisiologi Defekasi

Mass Movement

Physiology of Defecation

Defecation Reflex

Relaxation of Internal Anal Sphincter

Stimulus: Distention in rectum

Contraction in Rectum, Sigmoid Colon

Responses:

Contraction of External Anal Sphincter

Increased Pressure in Rectum

Defecation

Delay Contraction of external anal sphincter Reverse peristaltic in rectum

Contraction of puborectalis muscle

Relaxation of external anal sphincter

Relaxation of Puborectalis muscle

Forward peristaltic in rectum, sigmoid & colon

Valsava maneuver (increased abdominal pressure)

Physiology of Defecation Autonomic Nervous System

Intrinsic Myenteric Defecation Reflex Parasympathetic Defecation Reflex

Under control of: Somatic Nervous System

External Anal Sphincter

Intrinsic Defecation Reflex

Feces enter rectum

Defecation

Distention of Rectal Wall

Relaxed External Anal Sphincter

Initiates Signal Through Mesenteric Plexus

Internal Anal Sphincter Inhibit from Closing

Initiate Peristaltic Waves in Descending Colon, Sigmoid, and Rectum

Anus

Parasympathetic Defecation Reflex: (Involves Sacral Segments of the Spinal Cord Afferent Signals

Defecation

Parasympathetic Fibers (in Pelvic Nervous)

Relaxed Internal & External Anal Sphincter

Sacral Spinal Cord (Cause Intense Peristaltic Contraction)

Colon Descendent

Rectum

Colon Sigmoid

External Anal Sphincter External Anal Sphincter (Voluntary Controlled)

Relaxed: Defecation Occurs; Feces Expelled Through Anus

Contricted: Defecation can Postponed

Physiology of Defecation

When Feces enter Rectum from Sigmoid Colon

Stretch Receptor (in Rectal Wall) Send Nerve Impulse

Sacral Spinal Cord

Physiology of Defecation Motor Impulse from Cord Travel along Parasympathetic Nerve back to

Voluntary Contraction of Diaphragm

Internal Anal Sphincter Open

Colon Ascendens, Sigmoid, Rectum, Anus

Resulting Contraction of Longitudinal Rectal Muscle

Pressure in Rectum

Rectum Shortens

Physiology of Defecation

Voluntary Contraction of Diaphragm + Abdominal Muscle

↑ Pressure within Abdomen

Pushes wall of Sigmoid Colon & Rectum Inward

Physiology of Defecation If Defecation not Occur

Create the Urge of Defecate

Feces back up into Sigmoid Colon

Until the Next Wave of Mass Peristaltic again Stimulates the Stretch Receptors