Logan Steele
Peristalsis is a type of intestinal motility that occurs in the gastrointestinal tract. It is characterised by the radially symmetrical contraction and relaxation of muscles that propagate in a wave-like motion, pushing food through the digestive tract. This process involves both the circular muscles that ring the tubes of the digestive tract and the longitudinal muscles that span the walls of the tubes. Peristalsis is an involuntary muscle movement that occurs in progressive wavelike contractions, with the circular and longitudinal muscles contracting together in a coordinated manner.
| Characteristics | Values |
|---|---|
| Definition | A type of intestinal motility, characterised by radially symmetrical contraction and relaxation of muscles that propagate in a wave |
| Direction | Caudal, i.e. towards the anus |
| Muscle Types | Involuntary circular and longitudinal muscles |
| Muscle Movement | Contraction and relaxation |
| Muscle Contraction Type | Wave-like |
| Muscle Contraction Direction | Anterograde |
| Muscle Contraction Timing | Coordinated |
| Muscle Contraction Speed | Slows down in the stomach and intestines |
| Muscle Contraction Frequency | 3 waves per minute in the stomach and large intestine, 16 waves per minute in the small intestine |
| Muscle Contraction Strength | Weak in the oesophagus, strong in the stomach |
| Muscle Contraction Length | Long, continuous contractions that travel the whole length of the organ |
| Muscle Contraction Function | Propulsion of food, fluids, bile, urine, and faeces through the digestive tract |
| Muscle Contraction Initiation | Swallowing, distension of the oesophagus, presence of food particles |
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What You'll Learn
Involuntary circular and longitudinal muscle contractions
Peristalsis is a type of intestinal motility characterised by radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction. It is an involuntary movement that occurs in the longitudinal and circular muscles of the digestive tract, primarily in the oesophagus, stomach, and intestines. Peristalsis moves food through the digestive tract, beginning in the throat when one swallows and continuing through the oesophagus, stomach, and intestines during digestion.
Peristalsis is a progression of coordinated contractions of involuntary circular muscles, preceded by a simultaneous contraction of the longitudinal muscle and relaxation of the circular muscle in the gut lining. The smooth muscle tissue contracts in sequence to produce a peristaltic wave, propelling a ball of food (called a bolus before being transformed into chyme in the stomach) along the digestive tract. The peristaltic movement comprises the relaxation of circular smooth muscles, followed by their contraction behind the chewed material to prevent backward movement, and then longitudinal contraction to push it forward.
The circular muscles squeeze and expand in a synchronised manner to push food through the tube, while the longitudinal muscles propel everything forward. The wave-like pattern is more prominent earlier in the digestive process. Toward the end, only a few contractions are needed to push waste out. Peristalsis is often described as wave-like because the muscles contract and relax in a continuous pattern to move food forward.
Peristalsis is generally directed caudally, toward the anus. This directionality is likely due to the polarisation of the myenteric plexus, a network of nerves containing the interstitial cells of Cajal (ICC), which are considered the pacemaker cells of the gastrointestinal tract. The ICC mediate the process of peristalsis by alternating between distal relaxation and proximal contraction of the muscles. Effective peristalsis requires an active myenteric plexus.
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Peristalsis in the oesophagus
Peristalsis is a series of wave-like muscle contractions that move food through the digestive tract. It is an involuntary process that occurs in the gastrointestinal tract, starting in the oesophagus and continuing through the stomach and intestines. Peristalsis in the oesophagus specifically involves the contraction of both circular and longitudinal muscles in a precisely coordinated way.
The oesophagus is composed of smooth muscle tissue, which contracts in sequence to produce a peristaltic wave. This wave propels a ball of food, called a bolus, along the oesophagus and into the stomach. The bolus is then churned into a liquid mixture called chyme. The circular muscles squeeze and expand in a synchronized way to push the food through the tube, while the longitudinal muscles propel it forward.
The process of peristalsis in the oesophagus can be further divided into primary and secondary peristalsis. Primary peristalsis is induced by swallowing, while secondary peristalsis is evoked by distension of the oesophagus. During primary peristalsis, longitudinal muscle contraction causes oesophageal shortening. This shortening brings together the rings of circular muscles, increasing muscle mass and efficiency. The subsequent increase in muscle thickness reduces oesophageal wall stress, preventing outward bulging.
Studies have shown that the two layers of the oesophagus contract in a coordinated manner, with the longitudinal muscles contracting first and lasting 2-4 seconds longer than the circular muscle contraction. This coordination ensures the efficient propulsion of food through the oesophagus and into the stomach.
Disorders of peristalsis in the oesophagus can lead to conditions such as gastroesophageal reflux disease (GERD), small intestinal bacterial overgrowth (SIBO), and achalasia. Age-related atrophy of the gastrointestinal mucosa and muscles can also result in decreased oesophageal peristalsis.
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Peristalsis in the stomach
Peristalsis is a series of wave-like muscle contractions that move food through the digestive tract. It occurs in the pharynx, oesophagus, stomach, small intestine, large intestine, and rectum. Peristalsis in the stomach involves the thick muscular wall of the stomach churning and mixing the food with gastric juices to produce a semifluid mixture called chyme. The stomach exhibits maximum peristalsis, with the strongest peristaltic waves occurring in the distal regions of the stomach. Peristalsis in the stomach also involves the pyloric sphincter, which opens and closes to allow chyme to pass into the small intestine in instalments.
Peristalsis is an involuntary movement of the longitudinal and circular muscles that line the gastrointestinal tract. The circular muscles contract and relax in a synchronised manner to squeeze and expand, respectively, while the longitudinal muscles propel everything forward. Peristalsis in the stomach is preceded by a simultaneous contraction of the longitudinal muscle and relaxation of the circular muscle. This is followed by the contraction of the circular muscles behind the chewed food, preventing it from moving backward. Finally, the longitudinal muscles contract to push the food forward into the small intestine.
The migrating motor complex (MMC) triggers peristaltic waves in the stomach. These waves can be short, local reflexes or long, continuous contractions that travel the entire length of the organ. In the stomach, two to three peristaltic waves are usually present simultaneously in different regions, with about three waves occurring each minute. These waves help to mix the stomach contents and propel food toward the small intestine.
Peristalsis is essential for digestion and excretion. It moves food and fluids through each stage of the digestive process, allowing the gallbladder to move bile into the small intestine and the kidneys to move fluids into the bladder. Problems with peristalsis, known as motility disorders, can lead to either hypermotility or hypomotility. Hypermotility increases peristalsis, resulting in diarrhoea and poor digestion, while hypomotility decreases peristalsis, causing constipation and bacterial overgrowth.
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Peristalsis in the intestines
Peristalsis is a series of wave-like muscle contractions that move food through the digestive tract. It occurs in the smooth muscle oesophagus and the skeletal muscle oesophagus. Peristalsis in the skeletal muscle oesophagus is caused by the activation of neurons at the level of the vagal nucleus, while peristalsis in the smooth muscle oesophagus is mediated by the vagus nerve at the dorsomotor nucleus and myenteric plexus level. The myenteric plexus and ICC mediate the process of peristalsis by alternating between distal relaxation and proximal contraction of the muscles.
Peristalsis occurs in the oesophagus, stomach, and intestines. In the oesophagus, peristalsis begins at the upper portion of the tube and travels its entire length, pushing food into the stomach. Food particles left behind in the oesophagus initiate secondary peristaltic waves that remove leftover substances. Peristalsis in the stomach blends food with gastric juices, producing a mixture called chyme, which is then passed into the small intestine.
In the small intestine, peristalsis mixes and shifts chyme back and forth, allowing the bloodstream to absorb nutrients through the intestinal walls. Peristalsis also allows the gallbladder to move bile into the small intestine to aid digestion. In the large intestine, peristalsis helps to absorb water from undigested food into the bloodstream, and the remaining waste products are excreted through the rectum and anus. Peristalsis in the large intestine is continuous and progressive, steadily pushing waste towards the anal end of the tract.
Peristalsis is generally directed towards the anus, which may be attributable to the polarisation of the myenteric plexus. The myenteric plexus's afferent nerves deliver information to interneurons, which communicate with efferent nerves to stimulate an action potential within smooth muscle cells. The smooth muscle cells responsible for peristalsis include the inner circular and outer longitudinal layers of muscle, collectively called the muscularis propria.
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Tertiary peristalsis
Peristalsis is a type of intestinal motility characterised by radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction. It is the automatic wave-like movement of the muscles that line the gastrointestinal tract, beginning in the throat and continuing through the oesophagus, stomach, and intestines. Peristalsis moves food through the digestive system, propelled by the contraction of the circular and longitudinal muscles that line the gut.
During vomiting, the propulsion of food up the oesophagus and out of the mouth is due to the contraction of the abdominal muscles, not peristalsis. Peristalsis does not reverse in the oesophagus. When a peristaltic wave reaches the end of the oesophagus, the cardiac sphincter (gastroesophageal sphincter) opens, allowing the passage of food into the stomach. This sphincter normally remains closed to prevent the movement of stomach contents back into the oesophagus.
The churning movements of the stomach's thick muscular wall blend food with gastric juices, producing a mixture called chyme. The muscularis layer of the stomach exhibits maximum peristalsis. Peristalsis continues through the intestines, where the process slows down to allow for segmentation. Peristalsis also allows the kidneys to move fluids into the bladder and, at the end of the digestive process, excretes urine and faeces from the body.
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Frequently asked questions
Peristalsis is the wave-like movement of muscles that line the gastrointestinal tract, allowing food to move through the digestive system.
Peristalsis involves the contraction of both longitudinal and circular muscles in the gut.
Peristalsis is characterised by the radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube. The circular muscles squeeze and expand to push food through the tube, while the longitudinal muscles propel it forward.
Peristalsis occurs in the gastrointestinal tract, from the throat to the esophagus, stomach, and intestines. It can also occur in other hollow tubes of the body, such as the lymphatic system and the urethra.
Peristalsis is mediated by the enteric nervous system (ENS), which consists of two networks of nerves: the myenteric plexus and the submucosal plexus. The ICC cells within the myenteric plexus are considered the pacemaker cells of the gastrointestinal tract and play a key role in controlling peristalsis.
