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You are watching: Which of these is not an accessory organ of digestion

StatPearls . Treasure Island (FL): StatPearls Publishing; 2021 Jan-.


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Introduction

The digestive system comprises the gastrointestinal tract and also accessory organs. The cradle tract consists of the oral cavity, pharynx, esophagus, stomach, tiny intestine, and big intestine. The accessory organs are the teeth, tongue, and glandular offal such together salivary glands, liver, gallbladder, and pancreas.

The cradle system features to administer mechanical processing, digestion, absorb of food, secretion of water, acids, enzymes, buffer, salt, and excretion of garbage products.


Function

The role of the digestive device is come digest and absorb food and also then excrete the waste products with the assist of the liver, gallbladder, pancreas, tiny intestine, big intestine, and rectum. Each of this organs dram a specific duty in the digestive system.

The dental Cavity features to Provide


sensory analysis of food material prior to swallowing
mechanical handling via the action of the teeth, tongue, and also palatal surfaces
lubrication by mixing food material with mucus and salivary gland secretion
limited cradle of carbohydrates and lipids

Starting through the oral mucosa, which is lined by both keratinized (seen in the remarkable surface the the tongue and also the hard palate) and also nonkeratinized squamous epithelial cell (seen in cheeks, lips, and also inferior surface of the tongue), these cells are not well-known to absorb molecules except for the mucosa worse to the tongue.

Functions of the tongue include mechanical processing by compression, abrasion, and distortion; manipulation to aid in chewing and prepare material for swallowing; sensory analysis by touch, temperature, and also taste receptors; and secretion of mucins and lingual lipase. The lingual lipase has a vast pH and also breaks under lipids (mainly triglyceride). The pH that 3.5 to 6 allows lingual lipase to work even in the acid atmosphere of the stomach.<1>

Within the dental cavity, there room three pairs of salient glands. The first pair is the parotid outstanding glands located inferior to the zygomatic arch and also posterolateral to the mandible. The parotid glands produce serous secretions containing a huge amount of salient amylase, i beg your pardon breaks under carbohydrate complexes. Following are the sublingual outstanding glands located on the floor of the mouth. The sublingual glands produce a mucous secretion that serves together both a buffer and also lubricant. The 3rd is the submandibular outstanding glands, located at the floor the the mouth in ~ the mandibular groove. They function by secreting a mixture of buffers, glycoproteins dubbed mucins, and salivary amylase.

Altogether, this glands develop 1.0 to 1.5 liters the saliva each day.<2> Close come 99.4% the the saliva produced is water, and also the remaining 0.6% consists of electrolytes, buffers, glycoproteins (mucins), antibodies, enzymes, and also waste products. These role to lubricate the mouth to stop friction between the mucosa the the oral cavity and the food material; moisten the food material for straightforward swallowing process; and also initiation the lipid and carbohydrate complex digestion.

The teeth provide a mechanical failure of food materials; for instance, the connective organization of meat and also plant yarn in vegetables. This process also saturates the salient secretions and enzymes within the food material for far better digestion.

The pharynx serves as a passageway that food product to the stomach although it likewise has a respiratory function for waiting movement into the lung. Throughout swallowing, closure that the nasopharynx and also larynx wake up to keep the proper direction the food. This process is achieved by cranial nerves IX and X. Indigenous the pharynx, food material goes to the esophagus.

The esophagus"s primary duty is to north food materials right into the stomach via tide of convulsion of that is longitudinal and also circular muscle well-known as peristalsis. The upper one-third of the stomach is primarily skeletal muscle. The center one-third is a mixture of both the bones muscle and also smooth muscle. The lower one-third is greatly smooth muscle. However, during the action of deglutition, the buccal phase is the just voluntary phase wherein one deserve to still control the swallowing process. The skeletal muscles uncovered in the pharynx and also upper esophagus room all under the regulate of the sloop down reflex; hence the pharyngeal and esophageal phases of swallowing space under involuntary control aid of afferent and efferent yarn of glossopharyngeal and vagus nerves. The smooth muscle of the esophagus space arranged in a circular and also longitudinal fashion and help in peristaltic movement during swallowing.<3><4>

Once the food material arrives in the stomach, it have the right to be temporarily stored and also mechanically and chemically damaged down by the action of stomach acids and also enzymes. The secretion of intrinsic factor produced by the stomach helps through the proper absorption that vitamin B12.<5> The capability of the stomach to store food stems native its compliance and ability to adjust size. Top top average, the lesser curvature of the stomach has a size of around 10cm, and the bigger curvature has a length of roughly 40cm. The stomach frequently spans native vertebrae T7 and L3, giving it the ultimate ability to organize on come a huge amount of food.

The stomach"s role in breaking down food materials mechanically is as result of its advanced muscular dimensions. The stomach has actually 3 muscular layers: an inner oblique layer, a middle circular layer, and also an external longitudinal layer. The contraction and also relaxation of these 3 muscular great of the stomach help in the mixing and churning tasks essential in the formation of chyme. Climate the chemical breakdown of food material in the stomach is propagated by the gastric glands developed majorly through the parietal cells, the chef cells, G-cells, the foveolar cells, and the mucous neck cells. The parietal cells secrete intrinsic factors and also hydrochloric acid. The intrinsic factor developed is vital in the absorption of vitamin B12. It binding to B12, enabling for ideal absorption at the ileum of the tiny intestine.<6> The hydrochloric acid developed by the parietal cabinet keeps the stomach pH between 1.5 to 2.0. The acidity of the stomach brought on through hydrochloric mountain destroys most of the microbe ingested v food, denatures protein and breaks under plant cabinet walls, and is necessary for the activation and role of pepsin, a protein-digesting enzyme secreted by cook cells. The chef cells create a zymogen dubbed pepsinogen, i m sorry gets set off at pH in between 1.5 to 2 to come to be pepsin. Pepsin is a protein-digesting enzyme. The foveolar cells and mucous neck cells create mucous, which protects the gastric epithelium native acidic corrosion.<7> The G cells are abundant within the pyloric section of the stomach. They create gastrin i beg your pardon stimulates secretions from the parietal and also chief cells. Within the pyloric ar of the stomach, D cells create somatostatin, i beg your pardon inhibits gastrin release.<8>

The little intestine is the next location where cradle takes place. However unlike the stomach, which has actually minor absorptive property, 90% of food absorption occurs in the little intestine. The little intestine has three segments: the duodenum, the jejunum, and also the ileum. The duodenum obtain chyme from the stomach and digestive material from the pancreas and also the liver. The jejunum is whereby the mass of chemistry digestion and also absorption occur. The ileum likewise has digestion and also absorption functions. The ileum is the critical segment the the small intestine and also has the ileocecal valve, a sphincter that controls the flow of material from the ileum come the cecum of the big intestine. The little intestine mucosa has villi, and also each villus has actually multiple microvilli; thereby increasing the surface area significantly for optimal absorption.

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<9> over there are comprehensive networks the capillaries within the villi the carry soaked up nutrients to the hepatic portal circulation. Also, a substantial quantity that lymphatic capillaries called lacteals aid in chylomicron transportation to the venous circulation.

The intestine has both endocrine and exocrine glands that develop hormones, enzymes, and also alkaline mucinous material. The hormones exit by the small intestine include<10><11>: