¡Descarga anatomia y fisiologia del sistema digestivo y más Apuntes en PDF de Anatomía solo en Docsity! DIGESTIVE SYSTEM SUMMARY (ANATOMY AND PHYSIOLOGY) ORAL CAVITY, PHARYNX AND ESOPHAGUS ANATOMY PHYSIOLOGY Mouth is formed by cheeks, hard and soft palate, lips, tongue and teeth. Proper oral cavity: a space that extends from the gums and teeth to the fauces (the opening between the oral cavity and the pharynx) It has a roof: hard and soft palate, and uvula; and floor: the tongue Pharyngeal Arches: formed by 2 skeletal muscles: Palatoglossal muscle (1st arch) and palatopharyngeal muscle (2nd arch). Salivary glands secrete saliva: Major salivary glands - Parotid: below your ear and over masseter duct: Stenon’s duct drains into oral cavity close to the 1st upper molar - Submandibular is under lower edge of mandible Wharton’s duct - Sublingual Is deep to the tongue in floor of the mouth 2 ducts: Rivinus (several small rivinus ducts) + Bartholin duct (large duct) There are also several minor glands Tongue: forms the floor of the mouth; composed of skeletal muscle covered with mucous membrane. The lingual frenulum attaches to the undersurface of the tongue Pharynx: is a funnel-shaped tube that extend from the internal nares to the esophagus and larynx Esophagus: muscular tube, in front of vertebrae, posterior to trachea, posterior to the heart and connects the pharynx to the stomach. - When we see or smell food that activates the brain cortex which activates salivary glands by cranial nerves 7 and 9, which increases secretion of saliva - Food enters the mouth and it’s mechanically degraded by teeth and mixed with saliva to form bolus. Enzymes found in the saliva for chemical digestion, amylase for carbohydrates and lipase for triglycerides breakdown. Lipase is secreted by V. Ebner glands and its activity is lower than amylase. - Saliva’s function is to lubricate and dissolve food, to begin the chemical digestion and to keep the mucous membrane of the mouth and throat moist (lubricated) - The bolus is pushed towards the oropharynx by lifting the tongue (voluntary phase) and at the back of the throat there are receptors that send signals to the medulla and the signals are processed there. Then (pharyngeal stage – involuntary), it sends them back and initiate the lifting of the soft palate to close the nasopharynx and the larynx lifts, so epiglottis is bent to cover glottis. During this stage, breathing stops, the airways close by bending of epiglottis and closing of vocal cords. Next, (esophageal stage – involuntary) the upper esophageal sphincter relaxes so the bolus is transported to the stomach through the esophagus by peristalsis. The esophagus secretes mucus for lubrication. STOMACH ANATOMY PHYSIOLOGY - J-Shaped enlargement of GI tract - Begins at bottom of esophagus - Ends at pyloric sphincter - Is connected to liver by Lesser Omentum - Connected to pharynx by Esophagus - Subdivisions: cardia, fundus, body, pylorus - Ability to stretch due to rugae - If empty: mucosa lies in folds (rugae) - Pylorus starts to narrow as approaches pyloric sphincter, where stomach connects with small intestine - Has 2 curvatures: Greater & Lesser - Communicates with esophagus through lower esophageal sphincter and with intestine due to pyloric sphincter - Mixing and holding area for food - Converting bolus to liquid (chyme) by mechanical disruption and chemical digestion. - Mechanical digestion: peristaltic movements (mixing waves) Gentle mixing waves: mixes bolus with gastric juice to turn it into chyme More vigorous mixing waves: travel from body of stomach to pyloric region Intense mixing waves: (near pylorus) open pyloric sphincter and squirt out 1-2 teaspoon full of chyme to duodenum with each wave - Chemical digestion: conversion of proteins into peptides by pepsin; acid secreted by stomachs parietal cells HCI denatures protein molecules Continues digestion of triglycerides Gastric lipase: Splits certain molecules into fatty acids and monoglycerides HCI kills microbes in food Mucous cells protects stomach walls from being digested - Absorbs some substances through stomach lining (water, vitamins, ethanol, aspirin) but actually stomach wall is impermeable to substances - Cephalic phase: Vagus nerve increases stomach muscle and glandular activity in order to prepare stomach for food - Gastric phase: “Stomach working” - Secretion of gastrin by G cells into blood stream increases stomach glandular secretion (more acid) stomach crunching and pyloric sphincter relaxation.
