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Stack #57686

Saladin Digestive System

QuestionAnswer
Digestive Functions 1. Ingestion 2. Digestion 3. Absorption 4. Defecation
Ingestion Food is taken into the mouth, chewed and swallowed
Digestion Involves mechanical & enzymatic breakdown of large food particles into microscopic nutrients that are able to be absorbed into the bloodstream
Absorption Nutrients are pulled across the intestinal wall and enter the bloodstream where they are transported to all cells of the body
Defecation Elimination of undigested/unabsorbed food
Two Parts of Digestive System Mechanical & Chemical
Mechanical The large pieces of food that are ingested have to be broken into smaller particles that can be acted upon by various enzymes.
Chemical Uses water and digestive enzymes to break down the complex molecules.
Two Subdivisions of Digestive System Digestive Tract and Accesorry Organs
Digestive Tract Alimentary canal: Is tube through which food passes. Function = digestion, absorption and elimination.Components = mouth, pharynx, esophagus, stomach, small intestine (bowel), large intestine (bowel, colon). The GI tract consists of the stomach and intest
Accesorry Organs Structures that aid in digestion and absorption. Components = teeth, saliva, gall bladder, pancreas, liver and tongue.
Tissue Layer of the Digestive Tract 1. Mucous 2. Submucosa 3. Muscularis Externa 4. Serosa
Mucosa Innermost layer digestive tract wall. 3 parts: 1)a mucus membrane (stratified squamous epithelium in oral cavity, esophagus & anus, simple columnar epithelium in all other areas) 2) lamina propria (connective tissue w/capillaries 3) thin layer of smooth
Muscularis Externa In most areas of the digestive tract wall this layer consists of two layers of smooth muscle: an inner layer that has the muscle oriented circularly and an outer layer where the muscle is oriented longitudinally.
Relationship to the Peritoneum The stomach and intestines are loosely suspended from the abdominal wall by connective tissue sheets called mesenteries
Serous Membranes of Digestive Tract * Lesser Omentum * Greater Omentum * Beyond the transverse colon, the Great Oment continues as a mesentary called mesocolon.
Motility/Secretion of Digestive Tract controlled by * Neural * Hormonal * Paracrine
Functions of the Mouth Functions in the following: ingestion, taste , mastication, chemical digestion, speech, and respiration.
Mouth Enclosed by the cheeks, lips, palate, and tongue.
Cheeks and Lips Retain food and push it between the teeth for mastication. They are essential for sucking and blowing actions.
The Tongue Manipulates food b/w teeth Surface is covered with nonkeratinized stratified squamous epithelium
Tonsils Digestive & Respiratory
The Palate Separates the oral cavity from the nasal cavity
Two Parts of the Palate * Anterior Portion -> Hard Palate * Posterior Portion -> Soft palate
Teeth An adult normally has 32 teeth, 16 in the mandible and 16 in the maxilla. Collectively, the teeth are called the dentition.
Teeth Teeth can be grouped into incisors, canines, premolars, and molars, based on their shape, location, and function.
Decidious (Baby) Teeth 20 from ages 6 to 30 months
Permanent Teeth Ages 6 to 25, decidious replaced w/ permanent
Basic Anatomy of a Tooth Each tooth is embedded in a socket called an alveolus, forming a gomphosis between tooth and bone. The alveolus is lined by a periodontal ligament. The gum, or gingiva, covers the alveolar bone.
Three Main Regions of the Tooth * Crown * Root * Neck
If damaged the following two can regenerate Dentin and Cementin
If damaged, the following can not regenerate and must be artificially repaired Enamel
Mastication Breaks food into pieces small enough to be swallowed and exposes more surface to the action of digestive enzymes
Functions of Saliva Moistens the mouth, digests a small amount of starch and fat, cleanses the teeth, inhibits bacterial growth,
Contents of Saliva 97% to 99.5% water and following solutes: salivary amylase, lingual lipase, mucus, lysozyme, immunoglobulin A, and electrolytes.
Extrinsic Salivary Glands Situated outside the oral cavity but convey saliva to it through ducts. These are the parotid glands, submandibular glands, and sublingual glands.
Inflamation of the Carotid Mumps
Salivation Food stimulates tactile, pressure, and taste receptors, which transmit signals to the salivatory nuclei in the medulla oblongata and pons.
The Pharynx Has a deep layer of longitudinally oriented skeletal muscle & a superficial layer of circular skeletal muscle. a. The circular muscle is divided into superior, middle, and inferior pharyngeal constrictors, which force food downward during swallowing.
The Esophagus The esophagus is a straight muscular tube extending from the larynx to the stomach at the cardiac orifice.The inferior end of the esophagus is more constricted than the rest, forming a lower esophageal sphincter.
Swallowing Swallowing, or deglutition, is a complex action involving over 22 muscles in the mouth, pharynx and esophagus. They are coordinated by the swallowing center, a nucleus in the medulla oblongata and pons
Swallowing is moderated in two phases Buccal and Pharyngeal-esophageal phases.
Stomach The stomach is a muscular sac in the upper left abdominal cavity immediately inferior to the diaphragm.
Stomach Primary Function It functions primarily as a food storage organ. When empty, is has a volume of 50 mL. When very full, it may hold up to 4L.
Stomach divided into Four Regions The stomach is divided into four regions: the cardiac region, fundic region, body, and pyloric region.
Innervation The stomach receives parasympathetic and sympathetic stimulation.
Circulation It is supplied with blood from the celiac artery. All blood leaving the stomach enters the hepatic portal circulation before returning to the heart.
Stomach Wall * Has tissue layers similar to those of the esophagus * When the stomach is empty, the mucosa and submucosa form conspicuous longitudinal wrinkles called rugae. * The gastric mucosa is pocked with depressions called gastric pits
Cells of the Stomach Glands Mucous cells secrete mucus; regenerative cells divide rapidly & produce cells; parietal cells secrete HCL acid & intrinsic factor; chief cells secrete rennin & lipase in infancy & pepsinogen throughout life; enteroendocrine cells secrete hormones
Gastric Secretions * Hydrochloric acid * Enzymes * Intrinsic factor * Chemical Messengers
Submucosa Connective tissue. Contains blood vessels that supply the digestive tract cells with oxygen and nutrients and large lymphatic vessels that the lacteals drain into. Also contains the nerves of the autonomic nervous system. Neurons from the ANS nerves of th
Serosa Visceral Peritoneum.
Dentin Most of a tooth consists of hard, yellowish tissue that is covered with enamel in the crown and neck and cementum in the root
Intrinsic Salivary Glands Located w/i oral tissues, include the lingual glands embedded in tongue, labial glands on inner aspect of the lips, & buccal glands on the inside of the cheeks. They secrete relatively small amounts of saliva all the time to keep the mouth moist and inhi
Buccal The tongue collects food, forms a bolus, and pushes it back into the oropharynx.
Pharyngeal-esophageal phases. 3 actions are: (1) the root of the tongue blocks the oral cavity, (2) the soft palate rises and blocks the nasopharynx, and (3) the infrahyoid muscles pull the larynx up, the epiglottis covers its opening, and vestib. folds close off the airway
Stomach Mechanically breaks up food particles, liquefies the food, and begins the chemical digestion of proteins and a small amount of fat, producing a mixture of semidigested food called chyme.
Tongue Muscles Intrinsic & Extrinsic
Intrinsic Speech
Extrinsic Food Manipulation
Created by: littlemina74