Over view of the digestive system
Two groups of organs compose the digestive system:
-The gastrointestinal tract and the acessory igestive organbs
the gi tract is a continous tube that extends form the mouth to the anus,
the gi tract contains food from the mouth to the anus
the gi tract contains food from the time it is eaten until it is digested and abosrbed or eliminated from the body
orangs in this tract: mouth pharynx asophogus stomach small intestine and large intestine.
Acessory digestive system: the teeth tongue, salivary glands, liver, gallbladder and pancreas
teeth: brerak down food
tongue: chewing and swallowing
6 basic processes of the digestive systemL
ingestiuon- the process involves taking foods and liquids into the mouth
secretion: each day cells within the walls of the gi tract and acessory organs secrete a total of 7 liters of water, acid, buffers and enzymes into the lumen of the tract.
Mixing and propulsion: alternating contraction and relaxation of smooth muscle in the walls of the gi tract mix food and secretiion and propel them toward the anus.
Mobility: the aBILITY OF THE GI TRACT TO MIX AND move material along its length
digestioin: mechanical digestion- the teeth cut and grind foof before it is swallowed and then smooth muscles of the stomach and small intenstine churn the food.
... on exocrine and endocrine secretions and controlled movement of food through the digestive tract. Conclusion The digestion system is truly one of the ... digestive system is a series of hollow organs joined in a long tube that starts at the mouth and ends at the anus ... . Inside the tube is a lining called the mucosa. In the mouth, stomach, and ...
Chemical digestion- the large carbohydrate, lipid, protein and nucleic acid molecules in food are broken down into smaller molewcules by digestive enzymes.
Absorbtion: the entrance of ingested and secreted fluids, ions and small molecules that are products of digestion into the epithelial cells lining the lumen of the gi tract is called absorbtion. The absorbed substances pass into interstitial fluid and then into blood or lymph and circulate to cells throughtout the body.
Defecation: wastes, indigestible substances, bacteria, cells cshed from the lining of the gi tract and digested materibals that were not absorbed leave the body through the anus .
THE LAYERS OF THE GI TRACT AND THE OMENTUM.
layers from inside out: mucos, submucose muscularis and serosa
mucosa-inner lining, mucous membrane.
It is composed of a layer of areolar ct called the lamina propria and a thin layer of smooth muscle called the muscularis mucosae. The muscularis mucose create folds in the mucosaa that increase the surface area for digestion and absorbtion.
Submucosa- the submucosa consisits of areolar t that binds the mucosa to the muscularis. It contains many blood and lymphatic vessels that receive absorbed food molecules. Also located in the submucoses are networks of neurons that are part of the enteric nervous system. They control the the secretions of the organs in the gi tract.
Muscularis: as its name implies the muscularis of the gi tract is a thick layer of muscle. In the mouth the pharyn and upper esophogus it consists of muscle. In the mouth pharyn and upper esophogus it consits in part of the skeletal muscle that produces voluntary swallowing. Skeletal muscle also forms the external anal sphincter, which permits voluntary control of defecation. Ens neurons in the muscularis control the frequ4ency of the contraction
serosa: the outermost layer around the organs of the gi tract below the diaprhram is a membrane composed of simple squamos epithelium and areolar ct the serosa secreted a slippery watery fluid that allows the tract to glide easily againt other organs. The serosa is also called the visceral pwritoneum. The greater omentum drapes over ther transverse colon and small intestine like a fatty apron
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the mesentry binds the small intestine to the posterior of the abdominal wall.
Peritonitis: the acute inflamation of the perioneum by infectious microbes.
cheeks and lips are covered with mucous memebrane on the inside.
The hard palate which consists of maxille and palatine bones forms most of the roof of the mouth. The rest is formed by the muscular soft palat. Hanging down from the soft palate is a projection called the uvula. During swallowing the uvula moves upward with the soft palate which prevents entry of swalloed foods and liquids into the nasal cavity.
the tongue forms the floor of the oral cavity. It is and acessory digestive organ composed of skeletal muscle covvered with mucous membrane.
Maneuver food, shape and force it to the back of the mouth for later swallowing.
Thje lingiual frenelum a fold of mucous membrane in the midline of the undersurface of the tongue, limits the movement og the tongue posteriorly. The upper surface and sides of the tongue are covered with projections called papillae, some of which contain taste buds.
the three pairs of salivar glands are acessory organs of digestion that lie outside of the mouth and release their secretions into ducts emptying into the oral cavity.
The paotid glands are located inferior and anterior to the ars nbetween the skin and the masseter muscle.
The submadibular glands are found in the floor of the mouth they are medial and partly inferior to the mandible
the subligual glands are beneath the tongue and suprior to the submandiular glands
fluid secreted by salivary glands: saliva. 99.5 percent water ..5 percent sol;utes
–salva helps disolve food so that they can be tasted and digestion can begin.
One of saliva’s solutes, salivary amylase begins the digestions of starches in the mouth. Mucus in saliva lubricates food so it can be easily swallowed . The enzyme lysozyme kills bacteria thereby protecting the moith’s mucous membrane from infection and teeth from decaty.
... hold our food, meat or vegetable, with the chopsticks, send them to the mouths ... chopsticks cannot be used to cut food, so we usually use our teeth to act as knives. We ... the tables. Food should be cut by knives to fit into the mouths. Of course your mouth cannot touch ... like salt. Chinese cook should decorate the food, so the food which is not delicious becomes more delicious ...
Sympathetic stimulation during stress causes dry mouth.,.
the teeth are located in the mandible and the maxille and the sockets are covered by the gingivae.
Pulp- the ct containg blood vessels, nerves and lymphatic vessels. Narrow extensions of the pulp cavity run through the root of the tooth and are called root canals. Each root canal has an opening at its base through which blood vessels bring nourishment, lymphatic vessels ofer protection and nerves provide sensation. Humans have two sets of teeth: permanent teeh which appear btwn 6 and adulthood
and deciuous teeth , there are twent and are generally replaced btwn 6 and 12 years of age.
There are 32 teeth in a complete permanent set.
Teeth types: incisors cut food, cuspids tear and shed foodpremolars crush and grind food, molars crush and grind food(dull)
root canal therapy- traces of pulp tissue are removed from cavity. Root canals are filed out and irrigated to remove bacteria. The canals are medicated and sealed and then the crown is repaired.
Digestion in mouth
mastication = chewing, fod is manipulated by tongue, gorund up by teeth and mixed with saliva. In result the food is reduced to a soft flexible easily swallowed mass called a bolus
PHARYNX AND ESOPHAGUS
when food is swallowd it passes in to a funnel called the pharynx that is composed of skeletal muscle and lined with mucous membrane.
-helps propell food into the esophogus
-the esophagus is amuscular tube lined with stratified squamos epithelium that oies posterior to the trachea. It transports food to the stomach and secretes mucus. At the end of the esophogus the muscularis forms to sphincters the upper esophageal sphincter which consists of the skeletal muscle and the lower esophageal sphincter which consists of smooth muscle the upper esophageal sphincter regulates the movement of food from the pharyn into the eophagus the mlower esopheageal sphincter regulates the movement of food from the pharyn into the esophagus, the lower esophageal sphincter regulates the movement of food from the esophagus intot the stomach
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• swallowing, the movement of food from the mouth to th stomach, iswallowing is divided into three stages: the voluntary, pharyngeal and esophageal stages.
-voluntary stage of swallowing, the bolus is forced tot the back of the mouth cavity and into the oropharynx by the mvement of the tongue upward and backward against the palate,
-the passahe of the bolus into the oropharynx the epiglottis seals off the laryn and the vocal cords come toghther
-the esophageal stage, food is pushed through the esophagus by a process called peristalsis
the stomach c connects the esophagus to th duodenum, the first part of the small inestine.
The stomach also serves as a mixing and holding resevoir
structure of the stomach
the stromach has four regions: cardia, fundus,body and pylorus.
The cardia surrounds the superior opening of the stomach
-the stomach curves upward into the fundus
inferior to the fundus is the body
the narrow most inferior region is the plyorus]
betweem the plyorus and duodneum is the plyoric sphincter
when the stomach is empty the mucosa lies in large falds
the surface of the mucosa is a layer of nonciliated simple columnar epithelial cells called surface mucous cells.
-epithel;ial ccells also extenb p.481