II. Physiology

  1. Stool propelled via colon to Rectum
    1. Reaches cecum 4 hours after ingestion
    2. Reaches Rectum 7-8 hours after ingestion
  2. Stool enters Rectum
    1. Stool distends Rectum
    2. Rectum contracts reflexively
    3. Stool forced into anal canal
    4. Stool crosses 90 degree angle
      1. Canal straightened with hip flexion (squatting)
  3. Stool enters anal canal
    1. Internal anal sphincter (involuntary control)
      1. Automatically relaxes on stool entrance
      2. Stretch receptors (S2-4) signal stool in anal canal
    2. External anal sphincter (voluntary control)
      1. Voluntary relaxation results in Defecation
  4. Defecation
    1. External anal sphincter opens
    2. Intra-abdominal pressure increases with valsalva
    3. Stool moved out
  5. Results of chronically ignoring urge to defecate
    1. Sensory Receptor reflex arc less responsive
    2. Stool collects in distal colon
    3. Rectosigmoid colon dilates
    4. Stool desiccates and worsens Constipation

III. References

  1. Sartor in Dornbrand (1992) Ambulatory Care, p. 221-5
  2. Arce (2002) Am Fam Physician 65(11):2283-90 [PubMed]

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Related Studies

Ontology: Defecation (C0011135)

Definition (ICF) Functions of elimination of wastes and undigested food as faeces and related functions.
Definition (ICF-CY) Functions of elimination of wastes and undigested food as faeces and related functions.
Definition (OMS) Transporting food through the gastrointestinal tract to eliminate wastes.
Definition (MEDLINEPLUS)

A bowel movement is the last stop in the movement of food through your digestive tract. It is made of what is left after your digestive system (stomach, small intestine, and colon) absorbs nutrients and fluids from what you eat and drink. It's also called stool or feces. Stool passes out of the body through the rectum and anus.

Sometimes a bowel movement isn't normal. Diarrhea happens when stool passes through the large intestine too quickly. Constipation occurs when stool passes through the large intestine too slowly. Other abnormalities with bowel movements may be a sign of a digestive problem.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases

Definition (NCI_NCI-GLOSS) Movement of feces (undigested food, bacteria, mucus, and cells from the lining of the intestines) through the bowel and out the anus.
Definition (NCI) The normal process of elimination of fecal material from the rectum.
Definition (NCI_NCI-GLOSS) The way the intestines work in terms of how often there are bowel movements, the ability to control when to have a bowel movement, and whether the stools are hard and dry as in constipation or watery as in diarrhea.
Definition (MSH) The normal process of elimination of fecal material from the RECTUM.
Definition (GO) The expulsion of feces from the rectum. [GOC:mah]
Concepts Organism Function (T040)
MSH D003672
SnomedCT 9272000, 39211005, 111989001
LNC LP172749-6
English Defecations, Normal defecation, Bowel habits, Defecation functions, bowel action, bowels movements, defaecation, bowel habits, defecation, bowel habit, bowel functioning, bowel movements, stool passing, bowels movement, Bowel Function, Defecation, Bowel Movement, BM, poop, Poop, bowel movement, bowel function, Bowel function, Defaecation, Bowel action, Bowel habit, Bowel motion - function, Bowel movements, Passes stool completely, Bowel action (observable entity), Passes stool completely (finding), Defecation, NOS, Bowel habits, NOS, Defecation (function), Defecation (observable entity), Defecation, function (observable entity)
Swedish Tarmtömning
Czech defekace
Finnish Ulostaminen
Polish Wypróżnianie, Defekacja
Norwegian Defekasjon
Spanish acción intestinal (entidad observable), acción intestinal, defecación (entidad observable), defecación (función), defecación normal (hallazgo), defecación normal, defecación, función intestinal, hábitos intestinales (entidad observable), hábitos intestinales, movimiento intestinal - función, Defecación
French Défécation
German Stuhlentleerung, Defäkation
Italian Defecazione
Dutch Defecatie
Portuguese Defecação

Ontology: Fecal analysis procedure (C0202010)

Definition (CSP) examination of fecal matter for diagnostic purposes by chemical, physical, or microscopic means; includes performing chemical screening tests and screening for microorganisms or parasites.
Concepts Laboratory Procedure (T059)
SnomedCT 144823005, 144817000, 167698008, 144818005, 167598000, 167696007, 144921006, 167592004, 167593009, 83033005
English Faeces exam. - general NOS, Faeces examination NOS, Feces exam. - general NOS, Feces examination NOS, feces analysis, fecal analysis (lab test), fecal analysis, analysis stool, examination of feces, stool analysis, stool test, faeces analysis, feces examination, Faeces exam. - general NOS (procedure), Examination of faeces (procedure), Feces NOS (procedure), Feces NOS, Faeces NOS, Faeces examination - general (procedure), Faeces examination NOS (procedure), Feces examination - general NOS (procedure), Feces examination - general NOS, Feces examination NOS (procedure), Examination of faeces, Examination of feces, Faeces examination - general, Feces examination - general, Stool analysis, Examination of feces (procedure), Faeces analysis, Fecal analysis (procedure), Fecal analysis, Feces analysis, Feces examination - general (procedure), Faecal analysis, Fecal analysis, NOS, Feces analysis, NOS, Stool analysis, NOS, Faecal analysis, NOS, Faeces analysis, NOS, Fecal analysis procedure
Italian Analisi delle feci
Japanese 便検査, ベンケンサ
Spanish examen de materia fecal, SAI, examen fecal - general, SAI (procedimiento), Faeces examination NOS, materia fecal, SAI, Feces exam. - general NOS, Faeces exam. - general NOS, examen fecal - general, SAI, examen de heces, SAI (procedimiento), Feces examination NOS, heces, SAI, examen de heces, SAI, materia fecal, SAI (procedimiento), análisis de excrementos, análisis de heces, análisis de materia fecal (procedimiento), análisis de materia fecal, examen de heces, general, examen de heces, examen de materia fecal, SAI (procedimiento), examen fecal (procedimiento), examen fecal, general (procedimiento), examen fecal, general, examen fecal, Análisis de heces
Czech Analýza stolice
Hungarian Széklet elemzés
Portuguese Análise das fezes
Dutch ontlastingsanalyse
French Analyse de selles
German Stuhlanalyse