human digestive system anatomy and physiology pdf

Human digestive system anatomy and physiology pdf

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questions on digestive system in anatomy and physiology pdf

Overview of the Digestive System

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Digestive System

questions on digestive system in anatomy and physiology pdf

NCBI Bookshelf. The digestive system comprises the gastrointestinal tract and accessory organs. The gastrointestinal tract consists of the oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine.

The accessory organs are the teeth, tongue, and the glandular organs such as salivary gland, liver, gallbladder, and pancreas. The digestive system functions to provide mechanical processing, digestion, absorption of food, secretion of water, acids, enzymes, buffer, and salt, as well as excretion of waste products.

Each of these organs plays a specific role in the digestive system. The lingual lipase has a broad pH and breaks down lipids mainly triglyceride. The pH of 3. Within the oral cavity, there are three pairs of salivary glands. The sublingual glands produce a mucous secretion that serves as both a buffer and lubricant. They function by secreting a mixture of buffers, glycoproteins called mucins, and salivary amylase.

Altogether, these glands produce 1. These function to lubricate the mouth to prevent friction between the mucosa of the oral cavity and the food material; moisten the food material for easy swallowing process; and initiation of lipid and carbohydrate complex digestion. The teeth provide a mechanical breakdown of food materials; for instance, the connective tissue of meat and plant fibers in vegetables. This process also saturates the salivary secretions and enzymes within the food material for better digestion.

The pharynx serves as a passageway of food material to the esophagus although it also has a respiratory function for air movement into the lung. During swallowing, closure of nasopharynx and larynx occur to maintain proper direction of food. From the pharynx, food material goes to the esophagus. The esophagus's primary function is to empty food materials into the stomach via waves of contraction of its longitudinal and circular muscle known as peristalsis.

The upper one-third of the esophagus is predominantly skeletal muscle. The middle one-third is a mixture of both the skeletal muscle and smooth muscle. The lower one-third is mainly smooth muscle. However, during the act of deglutition, the buccal phase is the only voluntary phase where one can still control the swallowing process. The skeletal muscles found in the pharynx and upper esophagus are all under the control of the swallow reflex; hence the pharyngeal and esophageal phase of swallowing are under involuntary control with the help of afferent and efferent fibers of glossopharyngeal and vagus nerves.

Once the food material arrives in the stomach, it can be temporarily stored and mechanically and chemically broken down by the actions of stomach acids and enzymes. The secretion of intrinsic factor produced by the stomach helps with proper absorption of B On average, the lesser curvature of the stomach has a length of approximately 10cm and the larger curvature has a length of approximately 40cm. The stomach typically spans from vertebrae T7 and L3 giving it the ultimate ability to hold on to a large amount of food.

The stomach's function in breaking down food materials mechanically is due to its sophisticated muscular dimensions. The stomach has 3 muscular layers: an inner oblique layer, a middle circular layer, and an external longitudinal layer. The contraction and relaxation of these 3 muscular layers of the stomach assist in the mixing and churning activities essential in the formation of chyme.

The parietal cells secrete intrinsic factor and hydrochloric acid. The intrinsic factor produced is essential in the absorption of vitamin B It binds to B12 allowing for proper absorption at the ileum of the small intestine. The acidity of the stomach brought on by hydrochloric acid destroys most of the microorganisms ingested with food; denatures protein and breaks down plant cell walls; and is essential for the activation and function of pepsin, a protein-digesting enzyme secreted by chief cells.

The chief cells produce a zymogen called pepsinogen, which gets activated at pH between 1. Pepsin is a protein digesting enzyme. The foveolar cells and mucous neck cells produces mucous, which protects the gastric epithelium from acidic corrosion [7]. The G cells are abundant within the pyloric section of the stomach.

They produces gastrin which stimulates secretions from the parietal and chief cells. Within the pyloric section of the stomach, D cells produces somatostatin, which inhibits the release of gastrin. The small intestine is the next location where digestion take place.

The small intestine has three segments: the duodenum, the jejunum, and the ileum. The duodenum receives chyme from the stomach as well as digestive material from the pancreas and the liver.

The jejunum is where the bulk of chemical digestion and absorption occur. The ileum also has digestion and absorption function. The ileum is the last segment of the small intestine and has the ileocecal valve, a sphincter that controls the flow of material from the ileum to the cecum of the large intestine.

Also, there is a vast quantity of lymphatic capillaries called lacteals that aid in chylomicron transportation to the venous circulation. The intestine has both endocrine and exocrine glands that produce hormones, enzymes, and alkaline mucinous material. The hormones released by the small intestine include [10] [11] :. The enzymes produced by the small intestine include lipase for fats digestion; peptidase for peptide breakdown; sucrase, maltase, and lactase for sucrose, maltose, and lactose breakdown respectively.

Then there are the Brunner glands mostly found in the duodenum that produce bicarbonate for acid neutralization. Within the duodenum of the small intestine, accessory digestive organs such as the liver and the pancreas release digestive secretions. The liver is the largest internal organ and the largest gland in the human body. It has numerous functions; but as an accessory organ of the digestive system, it produces bile which emulsifies fats and various kinds of lipids for optimal digestion.

The gallbladder contracts to release bile into the duodenum when fat containing food is present. The exocrine glands of the pancreas produce multiple enzyme precursors and enzymes which includes trypsinogen, chymotrypsinogen, and procarboxypeptidase which are activated by enteropeptidase in the small intestine; active alpha amylase; lipases and colipase which act on triglycerides and phospholipids; and several other enzymes like ribonuclease, elastase and collagenase.

The unabsorbed and undigested food material progresses to the large intestine. The large intestine is about 6 feet long and starts with the cecum, ascending colon, transverse colon, descending colon, and sigmoid colon. The large intestine absorbs water and electrolytes.

In the rectum, there are stretch receptors that signal for the defecation process to start which includes a reflexive relaxation of internal anal sphincter smooth muscle and conscious relaxation of the external anal sphincter skeletal muscle. Diseases of the gastrointestinal system can be one of many causes, affecting anywhere from the mouth to the anal canal. Abnormalities of the oral cavity include salivary gland tumors such as pleomorphic adenoma, mucoepidermoid carcinoma, and Warthin tumor, all of which affect proper salivary content and production.

Within the esophagus is a wide range of pathologies: scleroderma, esophageal dysmotility, esophageal strictures, esophagitis, achalasia, and esophageal varices; these diseases can affect the movement of food into the stomach.

Further along the gastrointestinal tract, gastritis involves inflammation of the stomach. This condition can vary, depending on the duration of symptoms. Chronic causes of gastritis are typically due to Helicobacter pylori or autoimmune disease. Diseases of the small and large bowel include celiac disease, tropical sprue, Whipple disease, Crohn's disease, and ulcerative colitis, which impact digestion and absorption of food material.

In addition to pathologic conditions, congenital diseases such as Hirschprung, biliary atresia, intestinal atresia, malrotation of the intestine, and pyloric stenosis occur in infancy and may be life-threatening as adequate nutrients cannot be absorbed. Within the accessory organs of the gastrointestinal tract, there are hereditary hyperbilirubinemia disorders such as Gilbert syndrome, Dublin-Johnson syndrome, and Crigler-Najjar syndrome.

The commonality among these conditions is the impairment of normal processes that allow proper uptake, conjugation, and excretion of bilirubin waste products to take place.

Other accessory organ pathologies include hemochromatosis, Wilson's disease, biliary tract diseases, and pancreatitis. Diseases of the gallbladder prevent proper storage of bile from the liver, leading to malabsorption in the gut.

Examples of these conditions include cholelithiasis, choledocholithiasis, and cholecystitis. All of these diseases warrant proper work-up starting with a thorough history and physical exam. Obtaining a history of present illness is essential to the diagnosis of gastrointestinal system disease and clarification of questions regarding the location and duration of the pain, radiation or changes in intensity, precipitating factors, associated symptoms such as fever, chills, nausea, vomiting, changes in bowel habitus, and stool color.

A proper and thorough physical examination is imperative in working up gastrointestinal system diseases. All four quadrants of the abdomen must be inspected to appreciate the general abdominal contour. Patients may be asked to cough to check for abdominal herniation. After inspection, auscultation is performed to detect any abnormal bowel sounds, such as rubs and bruits.

It is necessary to take into account the anatomical location of the different abdominal organs, as this determines the sounds heard, along with the pathologies that correlate. For example, auscultating the right upper quadrant checks for liver rubs and bowel sounds, while listening to the left upper quadrant examines rubs or bruits within the splenic region. Pitch, intensity, and duration of the sounds should also be appreciated during auscultation.

Palpation of the abdomen starts at the right upper quadrant, to outline the size of the liver and detect signs of tenderness. The left upper quadrant, periumbilical, left and right lower quadrants are subsequently palpated to identify any unusual masses or signs of discomfort. The liver and spleen are solid organs that, when percussed, elicit a dull sound. Percussing the abdomen in the areas overlying these organs serves the purpose of assessing the size of the liver and spleen, in addition to determining whether tenderness is present.

Percussion of the abdomen can also identify any abnormal gas collection or ascites. The principle behind this technique is to compare the sounds elicited over a particular area with the normal, expected findings.

Careful palpation of the anal wall may help identify any hypertrophic papillae, inflamed crypts, strictures, and abnormal sphincter tone that might affect the normal passage of stool.

This book is distributed under the terms of the Creative Commons Attribution 4. Turn recording back on. National Center for Biotechnology Information , U. StatPearls [Internet]. Search term. Affiliations 1 University of the East Ramon Magsaysay.

Introduction The digestive system comprises the gastrointestinal tract and accessory organs. The oral cavity functions to provide: sensory analysis of food material before swallowing. Gastric inhibitory peptide GIP produced by K-cells in the upper small intestine in response to fat, amino acids, and glucose.

Overview of the Digestive System

The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital digestive organ. In the digestive system the stomach is involved in the second phase of digestion, following chewing. It performs a chemical breakdown by means of enzymes and hydrochloric acid. In humans and many other animals, the stomach is located between the oesophagus and the small intestine. It secretes digestive enzymes and gastric acid to aid in food digestion.


tract (mainly in the oral cavity and stomach) physically break down food Organs of the digestive system are divided into 2 main these teeth follow the human.


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Human digestive system , system used in the human body for the process of digestion. The human digestive system consists primarily of the digestive tract , or the series of structures and organs through which food and liquids pass during their processing into forms absorbable into the bloodstream. The system also consists of the structures through which wastes pass in the process of elimination and other organs that contribute juices necessary for the digestive process. The digestive tract begins at the lips and ends at the anus. It consists of the mouth , or oral cavity, with its teeth , for grinding the food, and its tongue , which serves to knead food and mix it with saliva ; the throat, or pharynx ; the esophagus ; the stomach ; the small intestine , consisting of the duodenum , the jejunum, and the ileum ; and the large intestine , consisting of the cecum , a closed-end sac connecting with the ileum, the ascending colon, the transverse colon, the descending colon, and the sigmoid colon , which terminates in the rectum.

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Digestive tracts vary considerably because animals have evolved different processes to convert foods to essential molecular building blocks. Differences in digestive strategies distinguish, for example, foregut and hindgut fermenters, and animals utilising different dominant food types, for example herbivores, carnivores, and folivores. Neither the modern human diet nor the size and proportions of the human gut resemble those of other primates. The human digestive system has evolved and diverged in response to introduction of new food types and food preparation techniques. For example, persistence of lactase activity into adulthood occurred in populations that maintained cattle to harvest milk.

Human digestive system

The easiest way to understand the digestive system is to divide its organs into two main categories.

Digestive System

The function of the digestive system is to break down the foods you eat, release their nutrients, and absorb those nutrients into the body. Although the small intestine is the workhorse of the system, where the majority of digestion occurs, and where most of the released nutrients are absorbed into the blood or lymph, each of the digestive system organs makes a vital contribution to this process [link]. As is the case with all body systems, the digestive system does not work in isolation; it functions cooperatively with the other systems of the body. Consider for example, the interrelationship between the digestive and cardiovascular systems. Arteries supply the digestive organs with oxygen and processed nutrients, and veins drain the digestive tract. These intestinal veins, constituting the hepatic portal system, are unique; they do not return blood directly to the heart. Rather, this blood is diverted to the liver where its nutrients are off-loaded for processing before blood completes its circuit back to the heart.

NCBI Bookshelf. The digestive system comprises the gastrointestinal tract and accessory organs. The gastrointestinal tract consists of the oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine.

Function of the Digestive System

The digestive system is a group of organs working together to convert food into energy and basic nutrients to feed the entire body. Food passes through a long tube inside the body known as the alimentary canal or the gastrointestinal tract GI tract. The alimentary canal is made up of the oral cavity, pharynx, esophagus, stomach, small intestines, and large intestines. In addition to the alimentary canal, there are several important accessory organs that help your body to digest food but do not have food pass through them. Accessory organs of the digestive system include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

This presentation was prepared using draft rules.

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