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Circular muscles are those that form a circle around the body, with fibres that encircle it. The muscular layer is a region of muscle in many organs in the vertebrate body, and it is responsible for gut movement such as peristalsis. The muscularis externa is responsible for segmental contractions and peristaltic movement in the GI tract, and consists of an inner circular layer and a longitudinal outer muscular layer. The inner circular layer is helical with a steep pitch, and the outer longitudinal layer is helical with a much shallower pitch.
| Characteristics | Values |
|---|---|
| Location | Between the submucosa and the outer longitudinal muscular layer |
| Function | Prevents food from traveling backward along the intestinal tract |
| Blood supply | Arterial blood supply from permeating capillaries coming from the submucosal arteriolar network |
| Innervation | Innervated by the myenteric plexus |
| Structure | The layers are helical with different pitches; the inner circular layer has a steep pitch |
| Equation | Relative intraluminal pressure (Pclosure - Pthorax) = hoop stress (Shoop) x (Rcirc/Tmuscle) |
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What You'll Learn
- The inner circular muscle is part of the muscularis externa
- Its role is to prevent food from travelling backward
- It works with the longitudinal layer to facilitate excretion
- The Auerbach's nerve plexus is found between the circular and longitudinal muscle layers
- The inner circular muscle is helical with a steep pitch
The inner circular muscle is part of the muscularis externa
The inner circular muscle is indeed part of the muscularis externa. The muscularis layer is responsible for the peristaltic movements and segmental contractions in the alimentary canal. The muscularis externa, in particular, is responsible for segmental contractions and peristaltic movement in the GI tract, causing food to move and churn together with digestive enzymes.
The muscularis externa consists of an inner circular layer and a longitudinal outer muscular layer. The inner circular muscle layer prevents food from travelling backward, while the outer longitudinal layer shortens the tract. The layers are not truly longitudinal or circular, but rather helical with different pitches. The inner circular layer is helical with a steep pitch, while the outer longitudinal layer has a much shallower pitch.
The muscularis layer is also known as the muscular coat, muscular fibres, muscularis propria, or muscularis externa. The muscularis propria refers to the region of muscle in many organs in the vertebrate body, adjacent to the submucosa. The muscularis externa is not to be confused with the muscularis mucosa, a thin layer of muscle within the submucosa, which is made up of smooth muscle and is most prominent in the stomach.
The Auerbach's nerve plexus (myenteric nerve plexus) is found between the longitudinal and circular muscle layers, initiating muscle contractions that start peristalsis. The myenteric plexus is located specifically between the circular and longitudinal muscular layers of the muscularis externa.
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Its role is to prevent food from travelling backward
The inner circular muscle is part of the muscularis layer, which is responsible for gut movement, including peristalsis and segmental contractions in the alimentary canal. The muscularis layer consists of an inner circular layer and a longitudinal outer muscular layer. The inner circular muscle is located between the submucosa and the outer longitudinal muscular layer.
The inner circular muscle plays a crucial role in preventing food from travelling backward in the GI tract. This is due to the structure of the circular layer, which impairs the luminal contents from travelling backward. The inner circular muscle works in conjunction with the longitudinal layer to facilitate peristaltic contractions, propelling intestinal contents toward the anus for excretion.
Peristalsis refers to the wavelike contractions of the muscles that propel food through the oesophagus and intestine. These contractions are initiated by the Auerbach's nerve plexus (myenteric nerve plexus), which is located between the longitudinal and circular muscle layers. The pressure at the mucosal-fluid interface required to maintain closure is known as closure pressure (Pclosure).
Mathematical modelling has been used to understand the function of longitudinal versus circular muscle fibres in oesophageal peristalsis. These models consider factors such as closure pressure, hoop stress, muscle thickness, and radius to the inner surface of the circular muscle. The Laplace law, derived from these equations, describes the relationship between intraluminal pressure and hoop stress in fully contracted regions of the gut.
In summary, the inner circular muscle is an essential component of the muscularis layer, responsible for preventing food from travelling backward and facilitating peristaltic contractions in the GI tract. Its structure and coordination with other muscle layers ensure the efficient and unidirectional movement of intestinal contents.
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It works with the longitudinal layer to facilitate excretion
The inner circular muscle is part of the muscular layer, which is a region of muscle in many organs in the vertebrate body. The muscular layer is responsible for gut movement, such as peristalsis, and segmental contractions in the alimentary canal. The inner circular muscle works in conjunction with the longitudinal layer to facilitate excretion.
The inner circular muscle is located between the submucosa and the outer longitudinal muscular layer. The Auerbach's nerve plexus (myenteric nerve plexus) is found between the longitudinal and circular muscle layers, and it initiates muscle contractions that begin peristalsis. The structure of the circular layer impairs the luminal contents from travelling backward along the intestinal tract.
The inner circular muscle and the longitudinal layer provide peristaltic contractions, facilitating the passage of intestinal content toward the anus for excretion. This process is known as esophageal peristalsis, and it involves the closure pressure at the mucosal-fluid interface and the average hoop stress across the circular and longitudinal muscle layers.
Mathematical modelling has been used to understand the relationship between closure pressure and hoop stress. The inner circular muscle radius is fixed, and muscle thickness does not change with variations in hoop stress. Changes in pressure indicate changes in circular muscle tone, and these measurements are made alongside quantifications in local shortening of longitudinal muscle fibres.
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The Auerbach's nerve plexus is found between the circular and longitudinal muscle layers
Circular muscles are a type of muscle fibre that encircles the body. The body's contents can be deformed into different shapes but maintain a constant volume. If longitudinal muscles contract and the body shortens, it must widen to accommodate its new volume.
The Auerbach's nerve plexus, also known as the myenteric plexus, is a group of ganglia that run throughout the entire gastrointestinal tract and innervate its multiple layers of smooth muscle. This collection of nerves is sandwiched between two layers of the muscularis externa, the inner circular muscle layer, and the outer longitudinal muscle.
The myenteric plexus originates in the medulla oblongata as a collection of neurons from the ventral part of the brain stem. The vagus nerve then carries the axons to their destination in the gastrointestinal tract. The plexus provides motor innervation to both layers of the muscular layer of the gut, having both parasympathetic and sympathetic input. It is found in the muscles of the oesophagus, stomach, and intestine.
The Auerbach's plexus is one of two significant components of the enteric nervous system. It is a collection of interconnected neurons that spans from the oesophagus to the rectum. Structurally, axons start over 100 nm away from the smooth muscle cells they innervate. According to preclinical studies, 30% of myenteric plexus' neurons are enteric sensory neurons, thus Auerbach's plexus also has a sensory component.
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The inner circular muscle is helical with a steep pitch
The inner circular muscle is part of the muscularis externa, which is responsible for segmental contractions and peristaltic movements in the gastrointestinal (GI) tract. The muscularis externa consists of two layers of muscle: an inner circular layer and an outer longitudinal layer. These layers work together to facilitate the passage of intestinal contents through the tract. The inner circular layer contracts to prevent food from travelling backward, while the outer longitudinal layer shortens the tract.
The muscularis externa is not the only muscular layer in the body. The muscularis layer, for example, is another region of muscle in many organs in the vertebrate body, adjacent to the submucosa. The muscularis layer is also responsible for gut movement, specifically peristalsis. The muscularis layer has an Auerbach's nerve plexus (myenteric nerve plexus) between the longitudinal and circular muscle layers, which starts muscle contractions to initiate peristalsis.
The muscularis layer can be found in the upper oesophagus, where part of the externa is skeletal muscle rather than smooth muscle. The muscularis layer can also be observed in the stomach, where there are three layers: an inner longitudinal layer, a middle circular layer, and an outer longitudinal layer.
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Frequently asked questions
The inner circular muscle is a layer of muscle that is present in many organs in the vertebrate body, adjacent to the submucosa. It is responsible for gut movement such as peristalsis.
The inner circular muscle is located in the muscularis externa, which is a region of muscle in many organs in the vertebrate body, including the alimentary canal, the upper esophagus, the stomach, and the ureter.
The inner circular muscle works with the longitudinal layer to provide peristaltic contractions, which facilitate the passage of intestinal content to the anus for excretion. It also prevents food from traveling backward in the GI tract.
