Review of Thr Mechanical Digestion in the Gastrointestinal Tract
Affiliate sixteen
Digestive System Processes and Regulation
OpenStax, Digestive System Processes and Regulation. OpenStax CNX. Jun 28, 2013 http://cnx.org/contents/afe83b13-0c1c-4d09-aa0b-4a0590580358@4. © Jun 28, 2013 OpenStax. Textbook content produced past OpenStax is licensed nether a Artistic Commons Attribution License three.0 license.
Past the terminate of this section, yous will exist able to:
- Discuss six fundamental activities of the digestive organization, giving an case of each
- Compare and dissimilarity the neural and hormonal controls involved in digestion
The digestive arrangement uses mechanical and chemical activities to break food down into absorbable substances during its journey through the digestive organization. Table 1 provides an overview of the basic functions of the digestive organs.
Table 1: Functions of the Digestive Organs
| Organ | Major functions | Other functions |
|---|---|---|
| Mouth |
|
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| Pharynx |
|
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| Esophagus |
|
|
| Stomach |
|
|
| Small intestine |
|
|
| Accessory organs |
|
|
| Large intestine |
|
|
Watch the video linked to below for an overview of digestion of nutrient in different regions of the digestive tract. Note the route of not-fat nutrients from the small intestine to their release equally nutrients to the body.
Digestive Processes
The processes of digestion include six activities: ingestion, propulsion, mechanical or physical digestion, chemical digestion, absorption, and defecation.
The commencement of these processes, ingestion, refers to the entry of nutrient into the alimentary canal through the rima oris. There, the food is chewed and mixed with saliva, which contains enzymes that begin breaking downward the carbohydrates in the food plus some lipid digestion via lingual lipase. Chewing increases the surface area of the food and allows an appropriately sized bolus to exist produced.
Nutrient leaves the mouth when the tongue and pharyngeal muscles propel it into the esophagus. This act of swallowing, the last voluntary act until defecation, is an example of propulsion, which refers to the motion of food through the digestive tract. It includes both the voluntary process of swallowing and the involuntary process of peristalsis. Peristalsis consists of sequential, alternate waves of contraction and relaxation of alimentary wall smooth muscles, which human activity to propel nutrient along (Effigy 1). These waves as well play a role in mixing food with digestive juices. Peristalsis is so powerful that foods and liquids you swallow enter your stomach even if y'all are standing on your head.
Peristalsis
Figure one: Peristalsis moves food through the digestive tract with alternating waves of muscle wrinkle and relaxation.
Digestion includes both mechanical and chemic processes. Mechanical digestion is a purely concrete procedure that does non change the chemic nature of the nutrient. Instead, information technology makes the food smaller to increase both surface area and mobility. Information technology includes mastication, or chewing, every bit well as tongue movements that help suspension food into smaller $.25 and mix nutrient with saliva. Although there may be a trend to call back that mechanical digestion is limited to the first steps of the digestive process, it occurs after the food leaves the mouth, as well. The mechanical churning of food in the breadbasket serves to further interruption it autonomously and expose more of its surface expanse to digestive juices, creating an acidic "soup" chosen chyme. Segmentation, which occurs mainly in the minor intestine, consists of localized contractions of circular musculus of the muscularis layer of the alimentary canal. These contractions isolate pocket-size sections of the intestine, moving their contents dorsum and along while continuously subdividing, breaking up, and mixing the contents. By moving food dorsum and along in the abdominal lumen, segmentation mixes food with digestive juices and facilitates absorption.
In chemic digestion, starting in the mouth, digestive secretions intermission downwards complex nutrient molecules into their chemical edifice blocks (for example, proteins into dissever amino acids). These secretions vary in composition, only typically contain h2o, diverse enzymes, acids, and salts. The procedure is completed in the modest intestine.
Nutrient that has been broken down is of no value to the body unless it enters the bloodstream and its nutrients are put to work. This occurs through the process of absorption, which takes place primarily within the small-scale intestine. There, most nutrients are captivated from the lumen of the alimentary culvert into the bloodstream through the epithelial cells that make up the mucosa. Lipids are absorbed into lacteals and are transported via the lymphatic vessels to the bloodstream (the subclavian veins near the heart). The details of these processes volition be discussed later.
In defecation, the final step in digestion, undigested materials are removed from the trunk as feces.
Aging and the…
Digestive System : From Appetite Suppression to Constipation
Age-related changes in the digestive system brainstorm in the mouth and can impact virtually every attribute of the digestive organisation. Taste buds go less sensitive, so food isn't as appetizing as it one time was. A slice of pizza is a challenge, not a treat, when you lot have lost teeth, your gums are diseased, and your salivary glands aren't producing plenty saliva. Swallowing can be difficult, and ingested food moves slowly through the alimentary culvert because of reduced strength and tone of muscular tissue. Neurosensory feedback is also dampened, slowing the transmission of messages that stimulate the release of enzymes and hormones.
Pathologies that affect the digestive organs—such as hiatal hernia, gastritis, and peptic ulcer disease—can occur at greater frequencies as you historic period. Problems in the small intestine may include duodenal ulcers, maldigestion, and malabsorption. Problems in the large intestine include hemorrhoids, diverticular disease, and constipation. Conditions that touch on the function of accessory organs—and their abilities to deliver pancreatic enzymes and bile to the small intestine—include jaundice, acute pancreatitis, cirrhosis, and gallstones.
In some cases, a single organ is in charge of a digestive process. For example, ingestion occurs only in the mouth and defecation only in the anus. Nonetheless, most digestive processes involve the interaction of several organs and occur gradually as food moves through the gastrointestinal tract (Figure 2).
Digestive Processes
Figure two: The digestive processes are ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation.
Some chemical digestion occurs in the oral cavity. Some absorption can occur in the mouth and stomach, for example, alcohol and aspirin.
Regulatory Mechanisms
Neural and endocrine regulatory mechanisms piece of work to maintain the optimal weather in the lumen needed for digestion and absorption. These regulatory mechanisms, which stimulate digestive activity through mechanical and chemic action, are controlled both extrinsically and intrinsically.
Neural Controls
The walls of the alimentary canal comprise a diversity of sensors that help regulate digestive functions. These include mechanoreceptors, chemoreceptors, and osmoreceptors, which are capable of detecting mechanical, chemical, and osmotic stimuli, respectively. For example, these receptors can sense when the presence of food has caused the tummy to aggrandize, whether food particles take been sufficiently broken down, how much liquid is present, and the type of nutrients in the food (lipids, carbohydrates, and/or proteins). Stimulation of these receptors provokes an advisable reflex that furthers the process of digestion. This may entail sending a message that activates the glands that secrete digestive juices into the lumen, or information technology may mean the stimulation of muscles within the gastrointestinal tract, thereby activating peristalsis and segmentation that movement nutrient along the abdominal tract.
The walls of the entire gastrointestinal tract are embedded with nerve plexuses that interact with the central nervous system and other nerve plexuses—either within the same digestive organ or in different ones. These interactions prompt several types of reflexes. Extrinsic nerve plexuses orchestrate long reflexes, which involve the central and autonomic nervous systems and work in response to stimuli from outside the digestive system. Brusque reflexes, on the other hand, are orchestrated by intrinsic nerve plexuses within the alimentary canal wall. These 2 plexuses and their connections were introduced earlier as the enteric nervous arrangement. Brusk reflexes regulate activities in one area of the digestive tract and may coordinate local peristaltic movements and stimulate digestive secretions. For example, the sight, smell, and taste of nutrient initiate long reflexes that brainstorm with a sensory neuron delivering a signal to the medulla oblongata. The response to the signal is to stimulate cells in the tummy to begin secreting digestive juices in training for incoming food. In dissimilarity, food that distends the stomach initiates short reflexes that cause cells in the tum wall to increase their secretion of digestive juices.
Hormonal Controls
A variety of hormones are involved in the digestive process. The principal digestive hormone of the tum is gastrin, which is secreted in response to the presence of nutrient. Gastrin stimulates the secretion of gastric acid by the parietal cells of the breadbasket mucosa. Other GI hormones are produced and act upon the gut and its accessory organs. Hormones produced by the duodenum include secretin, which stimulates a watery secretion of bicarbonate by the pancreas; cholecystokinin (CCK), which stimulates the secretion of pancreatic enzymes and bile from the liver and release of bile from the gallbladder; and gastric inhibitory peptide, which inhibits gastric secretion and slows gastric emptying and move. These GI hormones are secreted by specialized epithelial cells, called endocrinocytes, located in the mucosal epithelium of the tummy and small-scale intestine. These hormones then enter the bloodstream, through which they can reach their target organs.
Affiliate Review
The digestive system ingests and digests nutrient, absorbs released nutrients, and excretes food components that are indigestible. The six activities involved in this process are ingestion, motility, mechanical digestion, chemical digestion, absorption, and defecation. These processes are regulated by neural and hormonal mechanisms.
Source: https://guides.hostos.cuny.edu/bio140/5-16