The gut is a muscular tube about eight metres long with its own nervous system. This page explains how it mixes and moves food, how swallowing, gastric emptying and defecation are controlled, and how physiotherapists help with post-operative ileus, constipation and bowel emptying.
12Sections
5Figures
2Tables
10Questions
Part 7 · Digestion and Metabolism · Chapter 30 of 47
Learning objectives
By the end of this page you should be able to:
Describe the layers of the gut wall and the enteric nervous system.
Explain peristalsis, segmentation and the migrating motor complex.
Describe swallowing, gastric emptying and colonic movement.
Explain the defecation reflex and how posture affects it.
Summarise evidence on chewing gum after surgery and exercise for constipation.
Recognise motility problems relevant to physiotherapy.
Why it matters
After abdominal surgery the gut often stops moving for days, delaying eating and discharge. Immobile patients, opioid users and people with spinal cord injury or Parkinson disease commonly have constipation.
Physiotherapists influence gut motility through mobilisation, exercise, positioning, breathing and pelvic floor work. Swallowing problems after stroke also need to be recognised early.
The gut wall and its nerves
Figure 1 · Layers of the gut wall
A gut with its own brain. The enteric nervous system can run motility and secretion on its own; autonomic nerves adjust it.
Two layers of smooth muscle move the contents: an inner circular layer that narrows the tube and an outer longitudinal layer that shortens it. The enteric nervous system, between and beneath these layers, contains hundreds of millions of neurons and runs local reflexes.
Parasympathetic nerves, mainly the vagus and sacral nerves, generally increase motility and secretion. Sympathetic nerves reduce them, which is one reason stress, pain and surgery slow the gut.
Patterns of movement
Figure 2 · Peristalsis
Squeeze behind, relax ahead. Peristalsis moves contents along; segmentation mixes them without much forward movement.
Pattern
What it does
Where
Peristalsis
Propels contents forward
Oesophagus, small intestine, colon
Segmentation
Mixes contents with secretions; slows transit
Small intestine
Migrating motor complex
Sweeps the empty gut between meals
Stomach and small intestine (fasting)
Mass movements
Moves colonic contents a long way, often after meals
Colon
Smooth muscle has a slow wave of electrical activity set by pacemaker cells, the interstitial cells of Cajal. Contractions occur when slow waves reach threshold, under nervous and hormonal influence (Chapter 9).
Swallowing and the stomach
Swallowing begins voluntarily as the tongue pushes food back, then becomes a reflex coordinated by the brainstem. The airway closes, the upper oesophageal sphincter relaxes, and peristalsis carries the bolus to the stomach in seconds.
The stomach relaxes to receive food, grinds it into chyme and releases it slowly into the duodenum. Fat, acid and high calorie content slow emptying through nerve and hormone feedback from the duodenum.
Red flags
Coughing or choking with meals, a wet voice after swallowing or repeated chest infections after stroke suggest unsafe swallowing. Refer for swallowing assessment before oral intake is increased.
Transit through the gut
Figure 3 · How long food takes
Most of the time is spent in the colon. Inactivity, opioids, dehydration and low fibre slow colonic transit and cause constipation.
The colon absorbs water and salt and stores waste. Slow transit gives more time for water absorption and harder stool. Physical activity, adequate fluid and fibre, and regular toilet routines speed transit; opioids, inactivity and dehydration slow it.
Post-operative ileus
After abdominal surgery, handling of the bowel, inflammation, sympathetic activity and opioids temporarily stop coordinated motility. Short and colleagues reviewed 81 trials of chewing gum after surgery, which mimics eating and stimulates vagal activity to the gut [1].
Figure 4 · ‘Sham feeding’ speeds recovery of the gut
The cephalic phase in action. Chewing stimulates vagal activity to the gut. Many trials were small and of low quality, and benefit is smaller within enhanced recovery programmes [1].
Gum shortened time to first flatus and bowel movement and slightly reduced hospital stay [1]. Effects were largest after colorectal surgery and smaller within enhanced recovery programmes, which already include early feeding and mobilisation [1].
Defecation and constipation
When the rectum fills, stretch triggers a reflex that relaxes the internal anal sphincter and creates the urge. Voluntary control of the external sphincter and puborectalis decides when to go. Emptying uses a gentle rise in abdominal pressure with relaxation of the pelvic floor.
Figure 5 · Posture for emptying the bowel
Posture is a simple treatment. A footstool, forward lean and relaxed abdominal breathing help patients with straining and constipation. Schematic angles.
Gao and colleagues pooled nine trials of exercise for constipation, most using aerobic activities such as walking and Qigong. Exercise roughly doubled the chance of symptom improvement, though the trials had a high risk of bias [2].
Practical skill · helping a patient open the bowels
Encourage walking and active exercise as able [2]. Teach sitting with feet on a footstool, leaning forward with straight back, and relaxed ‘belly breathing’ rather than breath-holding and straining. Coordinate with the team on fluids, fibre and medication.
Clinical relevance for the physiotherapist
After surgery. Early mobilisation supports gut recovery; chewing gum may add a little [1].
Constipation. Aerobic exercise and good toileting posture help [2].
Spinal cord injury. Neurogenic bowel needs a regular programme coordinated with nursing.
Parkinson disease. Slow transit is common; activity and fluids help.
Stroke. Screen swallowing before oral intake progresses.
Assessment and application
Situation
Interpretation
Action
Day 2 after bowel surgery, no flatus, bloated
Post-operative ileus
Mobilise; discuss chewing gum with team [1]
Older inpatient on opioids, no bowel movement for 4 days
Opioid and immobility constipation
Walking programme [2]; toileting posture; inform team
Coughing during drinks after stroke
Possible aspiration
Stop oral intake; swallowing assessment
Straining with breath-holding on the toilet
Poor defecation technique
Teach posture and relaxed breathing
Common mistakes
Keeping post-operative patients in bed until bowel sounds return.
Assuming constipation is purely a diet problem [2].
Teaching patients to strain with a held breath.
Overstating chewing gum benefits within enhanced recovery programmes [1].
Missing swallowing problems in neurological patients.
Exam preparation
Long answer
Describe the movements of the small and large intestine and their control.
Gut wall and enteric nervous system (Figure 1).
Peristalsis, segmentation, migrating motor complex (Figure 2).
Colonic movements and transit (Figure 3).
Defecation reflex (Figure 5).
Clinical: ileus [1] and constipation [2].
Short notes
Enteric nervous system.
Deglutition.
Gastric emptying.
Defecation reflex.
Viva and practical
“What is the law of the gut?” — contraction behind, relaxation ahead.
“How might chewing gum help after surgery?” — vagal stimulation [1].
“Does exercise help constipation?” — probably, especially aerobic [2].
OSCE: teach toileting posture.
Current evidence
Exam and traditional teaching
Wait for bowel sounds before feeding or mobilising after surgery; treat constipation with laxatives.
What the evidence adds
Sham feeding with chewing gum speeds gut recovery after surgery, mainly outside enhanced recovery programmes [1].
Aerobic exercise may improve constipation [2].
What the student should understand
The gut responds to movement, posture and routine. Physiotherapy is part of bowel care.
Check yourself
10 questions on this page. Tap one to see the answer and the reasoning.
Q1. Chewing gum after surgery is thought to speed gut recovery by:
(A) Adding calories
(B) Cephalic-vagal stimulation of the gut
(C) Neutralising acid
(D) Blocking opioids
Answer: (B) Chewing gum is hypothesised to act through cephalo-vagal stimulation [1].
Q2. In the Cochrane review, chewing gum reduced time to first flatus by about:
(A) 1 hour
(B) 10 hours
(C) 3 days
(D) No change
Answer: (B) Overall reduction was about 10.4 hours [1].
Q3. Chewing gum reduced hospital stay by about:
(A) 0.7 days
(B) 7 days
(C) 70 days
(D) It increased stay
Answer: (A) Length of stay fell by about 0.7 days [1].
Q4. Within enhanced recovery (ERAS) programmes, the effect of chewing gum on length of stay was:
(A) Larger
(B) No difference between groups
(C) Harmful
(D) Not studied
Answer: (B) Sensitivity analysis of ERAS studies showed no difference in length of stay [1].
Q5. Which surgical group showed the largest benefit from chewing gum?
(A) Caesarean section
(B) Colorectal surgery
(C) Eye surgery
(D) Dental surgery
Answer: (B) Effect sizes were largest in colorectal surgery [1].
Q6. In the meta-analysis of exercise for constipation, exercise:
(A) Worsened symptoms
(B) Improved symptoms (RR about 1.97)
(C) Had no effect
(D) Was not studied
Answer: (B) Exercise improved symptoms with a relative risk of about 1.97 [2].
Q7. Most exercise programmes in that review were:
(A) Heavy resistance training
(B) Aerobic, such as walking and Qigong
(C) Swimming only
(D) Stretching only
Answer: (B) Eight of nine trials used aerobic exercise [2].
Q8. A limitation of the constipation evidence is:
(A) Very large high-quality trials
(B) High risk of bias and heterogeneity
(C) No outcomes measured
(D) Only children studied
Answer: (B) Results carried a high risk of bias [2].
Q9. The myenteric plexus mainly controls:
(A) Gut movement
(B) Taste
(C) Saliva only
(D) Bone growth
Answer: (A) It coordinates motility; vagal input, as stimulated by chewing, modulates it [1].
Q10. Practical advice to help a constipated, immobile patient includes:
Enteric nervous system: myenteric (motility) and submucosal (secretion) plexuses.
Peristalsis propels; segmentation mixes.
Transit: stomach hours, small intestine hours, colon days.
Post-operative ileus: chewing gum speeds recovery a little [1].
Exercise may improve constipation [2].
Footstool, forward lean, relaxed breathing aid emptying.
Further reading
Source
Why it earns its place
Short V et al. — Cochrane Review, 2015
Chewing gum after surgery [1]
Gao R et al. — Scand J Gastroenterol, 2019
Exercise for constipation [2]
Johnson LR — Gastrointestinal Physiology
Concise GI physiology
References
Short V, Herbert G, Perry R, et al. Chewing gum for postoperative recovery of gastrointestinal function.Cochrane Database of Systematic Reviews. 2015;(2):CD006506.
doi:10.1002/14651858.CD006506.pub3PMID 25914904Cochrane review
Gao R, Tao Y, Zhou C, et al. Exercise therapy in patients with constipation: a systematic review and meta-analysis of randomized controlled trials.Scandinavian Journal of Gastroenterology. 2019;54(2):169–177.
doi:10.1080/00365521.2019.1568544PMID 30843436Systematic review and meta-analysis
