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The human body is composed of different types of muscles, each with its own unique function. One such muscle is the intestinal muscle, which is a part of the gastrointestinal wall of the gastrointestinal tract. The gastrointestinal wall is made up of four layers of specialised tissue, namely the mucosa, the submucosa, the muscular layer, and the serosa or adventitia. The innermost layer of the gastrointestinal tract is the mucosa, which is made up of three layers, the outermost of which is the muscularis mucosae, a thin layer of smooth muscle. The muscular layer, which surrounds the submucosa, is composed of layers of smooth muscle in longitudinal and circular orientations. The coordinated contractions of these layers help with continued bowel movements and the movement of digested material out of and along the gut.
| Characteristics | Values |
|---|---|
| What lines the intestines | The mucosa, a mucus-secreting membrane, is the innermost layer of the gastrointestinal tract. It surrounds the lumen of the tract and comes into direct contact with digested food. |
| Number of layers in the mucosa | 3 |
| Layers of the mucosa | The epithelium, the lamina propria, and the muscularis mucosae |
| Description of layers | The epithelium is the innermost layer where most digestive, absorptive, and secretory processes occur. Goblet cells in the epithelium secrete mucus, which lubricates the passage of food and protects the intestinal wall from digestive enzymes. The lamina propria is a layer of connective tissue composed of structural protein molecules, nerves, and veins. The muscularis mucosae is a thin layer of smooth muscle that varies in thickness throughout the digestive tract and is most active in the stomach. |
| Other layers of the gastrointestinal wall | The submucosa, the muscular layer, and the serosa or adventitia |
| Abdominal muscles | Five main abdominal muscles hold organs in place and support the body during movement. |
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What You'll Learn
The mucosa is the innermost layer of the gastrointestinal tract
The gastrointestinal wall of the gastrointestinal tract is made up of four layers of specialised tissue. The mucosa is the innermost layer of the gastrointestinal tract. It surrounds the lumen of the tract and comes into direct contact with digested food (chyme).
The mucosa is made up of three layers: the epithelium, the lamina propria, and the muscularis mucosae. The epithelium is the innermost layer of the mucosa and is where most digestive, absorptive, and secretory processes occur. Goblet cells in the epithelium secrete mucus, which lubricates the passage of food and protects the intestinal wall from digestive enzymes. The lamina propria is a layer of connective tissue within the mucosa. It carries blood supply to the epithelium while holding the cells in place and binding them to the smooth muscle below. The deepest layer of the mucosa is the muscularis mucosae, a thin layer of smooth muscle. It varies in thickness throughout the digestive tract and is most active in the stomach. The muscularis mucosae provides a perpetual motor function that keeps the mucosa in flux, allowing it to stretch and contract along with the various organs of the digestive system.
The mucosa functions primarily as part of the body's immune system. It provides a protective barrier against foreign particles, capturing them in its sticky mucus and clearing them out. The mucus also lubricates and protects the organs and cavities from abrasive particles, bodily fluids, and invasive pathogens. The mucosa is designed to defend against abrasion and infection, but sometimes viruses, fungi, and bacteria can breach its defences, causing mucosal diseases.
The submucosa is the layer directly outside the mucosa. It contains nerves, blood vessels, and elastic fibres with collagen that stretch with increased capacity but maintain the shape of the intestine. The muscular layer surrounds the submucosa and comprises layers of smooth muscle in longitudinal and circular orientations that help with continued bowel movements (peristalsis) and the movement of digested material out of and along the gut.
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The muscularis mucosae is a thin layer of smooth muscle
The gastrointestinal wall of the gastrointestinal tract is made up of four layers of specialised tissue. The innermost layer is the mucosa, which is made up of three layers: the epithelium, the lamina propria, and the muscularis mucosae.
The muscularis mucosae is the deepest layer of the mucosa. It varies in thickness throughout the digestive tract and is most active in the stomach. It appears to provide a perpetual motor function that keeps the mucosa in flux, allowing it to stretch and contract along with the various organs of the digestive system.
The muscularis mucosae is an important part of the intestine clinically. It defines the border between the mucosa and the submucosa. Smooth muscle branches within the villus lamina propria enable the shortening and lengthening movements of the villi.
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The submucosa contains nerves and elastic fibres
The gastrointestinal wall of the gastrointestinal tract is made up of four layers of specialised tissue. The mucosa is the innermost layer, which surrounds the lumen of the tract and comes into direct contact with digested food. The mucosa is made up of three layers: the epithelium, the lamina propria, and the muscularis mucosae. The submucosa is the second layer of the gastrointestinal wall, located between the outermost layer of the mucosa and the muscularis externa.
The submucosa contains nerves, including the submucous plexus (also called Meissner's plexus), blood vessels, and elastic fibres with collagen. The collagen allows the intestine to stretch with increased capacity while maintaining its shape. The submucosa is a dense, irregular layer of connective tissue with large blood vessels, lymphatics, and nerves that support the mucosa. The submucosa has a rich vascular supply and lymphatic drainage and supports the absorption of electrolytes, fluids, and nutrients.
The submucosa is a layer of loose connective tissue located between the muscularis mucosa and the muscularis propria. It contains numerous plexuses of nerves, arteries, veins, and lymphatics. The submucosa primarily functions as a secretory layer, with glands that secrete mucus, bicarbonate, and epidermal growth factor. The submucosa is comparably thick in the stomach of most species, while it is thinner or even regarded as absent in the intestine.
The submucosa consists of a heterogeneous population of cells, including lymphocytes, plasma cells, macrophages, eosinophils, fibroblasts, and mast cells within a connective tissue matrix. An intricate network of blood vessels, nerve fibres, ganglia, and interstitial cells of Cajal (Meissner plexus) supply the mucosa and muscularis. The submucosal plexus is divided into two networks: Meissner's plexus, which lies closer to the mucosa, and Schabadasch's plexus, which lies adjacent to the inner circular muscle.
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The muscular layer surrounds the submucosa
The gastrointestinal wall of the gastrointestinal tract is made up of four layers of specialised tissue. The innermost layer is the mucosa, which is surrounded by the submucosa. The muscular layer, in turn, surrounds the submucosa.
The submucosa contains nerves, blood vessels, and elastic fibres with collagen. The collagen in the submucosa allows it to stretch while still maintaining the intestine's shape. The muscular layer that surrounds the submucosa is composed of layers of smooth muscle in longitudinal and circular orientations. The thickness of the muscular layer varies depending on its location in the gastrointestinal tract. For example, the muscular layer in the colon is thicker than in other parts of the tract because faeces are large and heavy and require more force to push along.
The coordinated contractions of the inner circular and outer longitudinal layers of muscle are called peristalsis. Peristalsis propels food through the gastrointestinal tract and helps with continued bowel movements. Peristalsis also prevents food from travelling backward in the gastrointestinal tract, as the circular muscle layer contracts to prevent retrograde movement of food.
The muscular layer surrounding the submucosa is essential for the movement of digested material out of and along the gut. This layer of muscle is also involved in the churning of food in the small intestine, where it mixes food with digestive juices. The muscular layer surrounding the submucosa is supplied with blood by the lamina propria, a layer of connective tissue within the mucosa.
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Abdominal muscles hold internal organs in place
The gastrointestinal wall of the gastrointestinal tract is made up of four layers of specialised tissue. The innermost layer is the mucosa, which is made up of three layers: the epithelium, the lamina propria, and the muscularis mucosae. The muscularis mucosae is a thin layer of smooth muscle that surrounds the submucosa, which contains nerves, blood vessels, and elastic fibres. The submucosa is surrounded by the muscular layer, which comprises layers of smooth muscle in longitudinal and circular orientations that help with continued bowel movements (peristalsis) and the movement of digested material out of and along the gut.
The abdominal muscles are located between the ribcage and the pelvis on the front of the body. They consist of five pairs of muscles, two of which are vertical muscles located towards the middle of the body, and three are flat muscles stacked on top of each other, situated towards the sides of the trunk. The rectus abdominis is the pair of muscles that go down either side of the middle of the abdomen from the ribs to the front of the pelvis. They hold internal organs in place, including the intestines, and keep the body stable during movement.
A hernia is a health issue that can affect the abdominal muscles. This occurs when an internal organ pushes through a weak spot in the muscle. For example, the small intestines may push through a weakened abdominal muscle in the groin area, causing an inguinal hernia. Prune belly syndrome is another condition that can affect the abdominal muscles. This rare condition causes a newborn's abdomen to look wrinkled due to absent or weak abdominal wall muscles.
The small intestine is a long coil of tissues and muscle that looks like a very long, thin, pink or red tube with many folds. It is located inside the lower abdominal cavity, where it lays in many coils. The small intestine has muscles that churn food back and forth and mix it with digestive juices. Peristalsis, an involuntary muscle movement, keeps food moving towards the ileum, the last and longest section of the small intestine.
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Frequently asked questions
The muscularis mucosae, a thin layer of smooth muscle, lines the intestines.
The muscularis mucosae provides a perpetual motor function that keeps the mucosa in flux, allowing it to stretch and contract along with the various organs of the digestive system.
The mucosa is the innermost layer of the gastrointestinal tract. It surrounds the lumen of the tract and comes into direct contact with digested food. It is made up of three layers: the epithelium, the lamina propria, and the muscularis mucosae.
The mucosa is a mucus-secreting membrane that lubricates and protects the organs and cavities from abrasive particles, bodily fluids, and invasive pathogens.
The abdominal muscles consist of five pairs of muscles that help hold organs in place and provide core support.
