Chapter 23 General Structure and the Stomach
Chapter 23 General Structure and the Stomach KNR 182
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Date Created: 09/21/15
HUMAN ANATOMY amp PHYSIOLOGY KNR 182 Digestive System Chapter 23 Digestive System Two groups of organs 1 Alimentary canal gastrointestinal or GI tract Digests anol absorbs food Mouth pharynx esophagus stomach small intestine and large intestine Long tube that goes from mouth to anus Digestive System 2 Accessory digestive organs Teeth tongue gallbladder Digestive glands Salivary glands Liver pancreas IMPORTANT Parotid land Mouth oral caVIty Subling a gland Samar Tongue Submandibular y glands gland h Esophagus Pharynx Stomach Pancreas Liver Sp39een Gallbladder Transverse colon Duodenum 39 Descending colon Small Jejunum quot Ascending colon intestine quotGum Cecum Large Sigmoid colon intestine Rectum Vermiform appendix Anus Anal canal Figure 231 Digestive Processes Six essential activities 1 lnges on 1 The act of putting food into your mouth 2 Propulsion 1 The act of moving food through the alimentary canal 3 Mechanical Digestion 1 Physically breaking down preparing it food for chemical digestion increases surface area of food for enzymes to act on 4 Chemical Digestion 1 Enzymatic chemical reactions break down food into the monomers 5 Absorption 1 The process by which the products of digestion pass through the alimentary tube mucosa into the blood or lymph 6 Defecation 1 Elimination of the contents of the bowels Food Mechanical digestion Pharynx Chewing mouth Esophagus Churning stomach 391 PVOPUISiO Segmentation Swauowing small intestine 39 oropharynx Chemlpal Peristalsis dlgestlon t maCh esophagus stomach small intestine large intestine Absorption Lymph vessel intestine 1 Large f n Blood intestine Y vessel Malnly H20 Feces yr Anus Figure 232 From mouth a Peristalsis Adjacent segments of b Segmentation Nenadiaeent segments alimentary tract organs alternately contract at alimentary traet organs alternately and relax which moves food along the tract contract and retaX moving the feed distally forward then backward Food mixing and slow food propulsion occurs Figure 233 General Characteristics of the Alimentary Canal The alimentary canal is a muscular tube about 8 meters Vquot long Histology of the Alimentary Canal Four basic layers tunics Mucosa Submucosa Muscularis externa Serosa Lumentheopening Where 3quot can ow and Intrinsic nerve plexuses Where f d 9 95 Myenteric nerve plexus Submucosal nerve plexus Glands in submucosa E Mucosa Epithelium Lamina propria quot Muscularis mucosae g Submucosa 39 Muscularis x i externa 9quot 5quot Longitudinal a 5 3 I musce 5 4 Clrcular muscle a Serosa f quot Epithelium f Connective g y o tissue Gland in mucosa Lumen Lymphatic Duct of gland outside Mucosaassociated Mesentery vessel alimentary canal lymphoid tissue Figure 236 Mucosa Lines the lumen Epithelial tissue Very smooth no friction Func ons Secretes mucus digestive enzymes and hormones Absorbs end products of digestion Protects against infectious disease Submucosa anol Muscularis Externa Submucosa The layer above the mucosa layer Dense connective tissue Blood and lymphatic vessels lymphoid follicles and submucosal nerve plexus Aids in absorption so cells can make ATP Submucosa and Muscularis Externa Muscularis externa aka muscularis Responsible for segmentation and peristalsis Inner circular and outer longitudinal layers Circular muscle that influences the size and diameter of the tube Aids in moving food along the GI tract Nerve plexus Sphincters in some regions Serosa Visceral peritoneum Replaced by the fibrous adventitia in the esophagus Retroperitoneal organs have both an adventitia and serosa Outermost layer lines the outer layer of the alimentary canal Strong fibrous tissue Produces a lubricant that reduces friction Intrinsic nerve plexuses Myenteric nerve plexus Submucosal nerve plexus Glands in submucosa Mucosa Epithelium Lamina propria J Muscularis 39 1 mucosae I Submucosa quot I Muscularis a externa lt 4 I Longitudinal l muscle 5 Circular muscle Serosa Epithelium Connective 39 tissue y Y Gland in mucosa Lumen Lymphatic Duct of gland outside Mucosaassociated Mesentery vessel alimentary canal lymphoid tissue Figure 236 57 1 I o a sit2 39 rm vmu a i x 39 I 3 J Mucosa v contains a stratified squamous epithelium Submueosa areolar connective tIssue Lumen Muscularis externa Longitudinal layer 3 935 Circular layer newtquot f lg Adventltlaflbrous z connective tissue Figure 2312a Mouth Oral buccal cavity Bounded by lips cheeks palate and tongue Oral orifice is the anterior opening Lined with stratified squamous epithelium Allows for ingestion to take place Somewhere for you to put food Your lips are pinkred because there are a lot of blood vessels there This is a way for your body to protect itself ie if something is too hot when it touches your lips you will not put it in your mouth Preventing you from burning yourself further Soft palate Palatoglossal arch Uvula Hard palate 4 Oral cavity Palatine tonsil Tongue Oropharynx Lingual tonsil Epiglottis Hyoid bone Laryngopharynx Esophagus Trachea a Sagittal section of the oral cavity and pharynx Figure 237a Gingivae gums Palatine raphe Hard palate Soft palate Uvula Palatine tonsil Sublingual told with openings of sublingual ducts Vestibule Lower lip b Anterior View Upper lip Superior labial frenulum Palatoglossal arch Palatopharyngeal arch Posterior wall of oropharynx Tongue Lingual frenulum Opening of submandibular duct Gingivae gums Inferior labial frenulum Figure 237b Palate Palate Forms the roof of your mouth and is composed of two parts Hard palate palatine bones and palatine processes of the maxillae Slightly corrugated to help create friction against the tongue Corrugated bumpy has ridges which helps to break down food Tongue pushed food up onto the palate while chewing Soft palate mobile fold formed mostly of skeletal muscle Closes off the nasopharynx during swallowing Uvula projects downward from its free edge Tongue Functions include Repositioning and mixing food during chewing Forms food into a bolus Initiation of swallowing speech and taste Composed of interwoven muscular fibers Epiglottis Palatopharyngeal a arch Palatine tonsil Lingual tonsil Palatoglossal arch Terminal sulcus FOliate Circumvallate papilla Midline groove of tongue Dorsum of tongue 7 Fungiform papiH Filiform papilla Figure 238 Salivary Glands Buccal salivary glands are scattered in the oral mucosa Secretion saliva Cleanses the mouth Moistens and dissolves food chemicals Aids in bolus formation Contains enzymes that begin the breakdown of starch Begins carbohydrate digestion Enzyme Salivary amylase Starts in mouth Tongue Teeth Ducts of suangual gland Frenulum of tongue Suangual gland Mylohyoid muscle cut Anterior belly of digastric muscle a Submandibular gland Parotid gland Parotid duct Masseter muscle Body of mandible cut Posterior belly of digastric muscle Submandibular duct b Mucous cells Serous cells forming demilunes Figure 239 Teeth Primary and permanent dentitions are formed by age 21 20 deciduous teeth erupt 6 24 months of age Roots are resorbed teeth fall out 6 1 2 years of age as permanent teeth develop Baby teeth deciduous receiving upon maturity 32 permanent teeth All except third molars erupt by the end of adolescence Ex Pizzamechanical to break apartdown food making it easier to swallow and to fit into the mouth Chemical increases surface area for enzymes to work on allowing digestion to happen more readily You position food when biting for each kind of tooth hard foods in back and soft foods up front Incisors Central 6 8 mo Lateral 8 10 max Canine eyetook Y I 16 20 mo Molars A I quot its I J 1 rst molar 39 10 15 mo about 2 yr Incisors Central 7 yr Lateral 8 yr Canine eyetooth 11 yr Premolars bicuspids l A First remolar 3 39 Deciduous V39 p Second molar milk teeth 11 W Second premolar 12 13 yr Molars First molar 6 7 yr 1 12 13 yr Third molar if wisdom tooth f I 17 25 yr quot 39 t 39 1 I t I i 39 Ye LCM r 39 I v I 39 A 7 l J Second molar 6 eg I L I Permanent teeth Figure 2310a Pharynx Oropharynx and laryngopharynx Allow passage of food fluids and air Food and fluid esophagus Air trachea Stratified squamous epithelium lining Smooth to reduce friction Skeletal muscle layers inner longitudinal outer pharyngeal oonstriotors Outer oonstriotor move food by peristalsis down esophagus Pharynx Nasopharynx Oropharynx Laryngopharynx b Regions of the pharynx Figure 223b Esophagus Flat muscular tube from laryngopharynx to stomach Posterior to trachea Pierces diaphragm at esophageal hiatus Muscle Allows for breathing in and out Domeshaped muscle by lower ribs Joins stomach at the cardiac orifice Gastroesophageal sphincter Regulates movement of food into and out of stomach Gastric reflux when contents of stomach move into the esophagus because gastroesophageal sphincter is not closing all of the way Digestive Processes Mouth nges on Putting food into mouth Mechanical digestion Mastication aka chewing is partly voluntary partly reflexive Don t think about chewing but you control how you chew fast slow vigerousetc Chemical digestion Salivary amylase begins carb digestion in the mouth Propulsion Deglutition swallowing moves food from mouth to esophagus to the next stage Swallowing Mechanism Swallowing can be divided into three stages 1 Voluntary stage where saliva is mixed with chewed food 2 Swallowing begins and the swallowing reflex is triggered 3 Peristalsis transports food in the esophagus to the stomach YOUTUBE Swallowing Deglutition from Anatomv thsiologv online wmv1 Pharynx Epiglottis Glottis Trachea CD Upper esophageal sphincter is contracted During the buccal phase the tongue presses against the hard palate forcing the food bolus into the oropharynx where the involuntary phase begins Figure 2313 step 1 Uvula Bolus Epiglottis Esophagus 1 The uvula and larynx rise to prevent food from entering respiratory passageways The tongue blocks off the mouth The upper esophageal sphincter relaxes allowing food to enter the esophagus Figure 2313 step 2 n r 7 5quot b Bolus 36 The constrictor muscles of the pharynx contract forcing food into the esophagus inferiorly The upper esophageal sphincter contracts closes after entry Figure 2313 step 3 Relaxed muscles Circular muscles contract Food is moved through the esophagus to the stomach by peristalsis Bolus of food Longitudinal muscles contract Gastroesophageal sphincter closed Figure 2313 step 4 i ReIaxed The gastroesophageal muscles sphincter opens and food enters the stomach Gastroesophageal sphincter opens Figure 2313 step 5 Bolus of food Tongue Pharynx Epiglottis Glottis Trachea Bolus Esophagus lt1 Upper esophageal sphincter is The uvula and larynx rise to prevent food The constrictor muscles of the contracted During the buccal phase the from entering respiratory passageways The pharynx contract forcing food tongue presses against the hard palate tongue blocks off the mouth The upper into the esophagus inferiorly The forcing the food bolus into the oropharynx esophageal sphincter relaxes allowing food upper esophageal sphincter where the involuntary phase begins to enter the esophagus contracts closes after entry Relaxed muscles ReIaxed The gastroesophageal muscles sphincter opens and food enters the stomach Food is moved through the esophagus to the stomach by peristalsis i i 39 Circular muscles contract 39 Bolus of food Longitudinal muscles contract Gastroesophageal sphincter closed Gastroesophageal sphincter opens Figure 2313 Stomach Functions Temporary storage tank Empty holds 17 oz Full can hold 4 liters1 gallon Initiates chemical breakdowns of protein Converts bolus to chime A much more liquidy consistency than bolus because it is mixed with gastric juices Stomach Gross Anatomy Cardiac region cardia Surrounds the cardiac orifice Fundus Domeshaped region beneath the diaphragm Body Midportion Stomach Gross Anatomy Pyloric region Pylorus is continuous with the duodenum through the pyloric valve sphincter Greater curvature Convex lateral surface Large curve outside Lesser curvature Concave medial surface Small curve inside Cardia Muscularis w H eXtema K Serosa Longitudinal layer quot r Fundus Circular layer Body Oblique layer L Lesser me curvatur Rugae of 1 J mucosa Greater 3quot curvature I lloric Pyloric canal antrum Pyloric sphincter a valve at pylorus Duodenum Figure 2314a Stomach Gross Anatomy Muscularis Externa Oblique layer for mixing churning and breaking food down Muscle fibers run longitudinal circular and oblique Helps to mix contents of stomach so that chemical and mechanical digestion can occur Gives stomach a great ability to expand and contract Third layer oblique adds structure and support Mucosa Gastric pits Mucous parietal and chief cells Capacity Speed eating Is it gastric distension expanding or are they able to empty the contents of their stomach further Answer Distension Long term health lmplications unknown you will have to monitor your diet because your body can t tell when you are full anymore Rugae Longitudinal folds Changes in size When stomach is empty the folds wi fold on each other When you eat to capacity the stomach and folds will stretch out Allow for massive changes in size Stomach Size Bariatric Surgery for Weight loss Gastric bypass Bypassing part of the stomach so it is not digested Gastric band Put a band to different sizes so that the stomach cant expand like it normally would just smaller so you feel fuller faster Can over eat with it Not permanent Less of a long term health risk Need to have counseling so that people can make a long term commitment to healthy eating don t use food as a coping mechanism Mucosa I Surface epithelium 1 it WWJSMMW39 Lamina propria Muscularis Submucosa contains submucosal plexus Muscularis externa contains myenteric plexus mucosae rOblique layer Circular layer Longitudinal layer Stomach wall Serosa a Layers of the stomach wall ls Figure 2315a Gastric pits Surface epithelium mucous cells a s quotquot immnmlm Gastric pIt j mmwmlmm U l a N 39 Mucous neck cells Parietal cell Chief cell H V 1 2 MW ftplll39l 39 11 m v Gastric gland K 1 5 a 1 quotKquot l JJI A 3 1 1H3 NI39K V a 39 on b 9 5 39 rs 1quot 39 um zv1avnmgxmrwwm u If Vzi ylz ijjl s llassgt quot v39v x Enteroendocrine cell b Enlarged View of gastric pits and gastric glands Figure 2315b Gastric Gland Secretions Glands in the fundus and body produce most of the gastric juice Each type of cell has a certain function secretion Parietal cell secretions HCI 6 most important secretion in parietal cells Enzyme is only activated when in the presence of HCI Drastically increases the acidity of the stomach Defense mechanism to kill microbes entering your system via food and cross contamination gt pH 15 35 denatures protein in food activates pepsin and kills many bacteria Breaks protein down in order to get to the monomers Intrinsic factor Glycoprotein required for absorption of vitamin B12 in small intestine f Pepsmogen H ClgtPepsm Mitochondria Parietal cell Chief cell Enteroendocrine cell c Location of the HClproducing parietal cells and pepsinsecreting chief cells in a gastric gland Figure 2315c Gastric Gland Secretions Chief cell secretions Pepsinogen inactive enzyme Activated to pepsin by HCI and by pepsin itself a positive feedback mechanism Pepsin digestive enzyme Function protein digestion Can also activate pepsinogen to change its form to pepsin Only want pepsin active when there is food present Otherwise it will start breaking down your stomach Mucosal Barrier Mucus cells secrete mucus Layer of bicarbonaterich mucus Helps to increase pH Tight junctions between epithelial cells Provides protection of stomach mucosa from digestion from pepsin Gastric Secretions The mucous membrane of the stomach has tubular gastric glands that secrete Pepsinogen From the chief cells Inactive form of pepsin Pepsin From pepsinogen in the presence of hydrochloric acid Is a protein splitting enzyme Hydrochloric acid From the parietal cells Needed to convert pepsinogen to pepsin Mucus From the goblet cells and the mucous glands Protective to stomach wall Intrinsic factor From the parietal cells s required for vitamin B12 absorption Gastric Absorption Gastric enzymes begin breaking down proteins but the stomach is not welladapted to absorb digestive products The stomach does absorb Some water Certain salts Certain lipidsoluble drugs Why you need to take some medications with or without food Alcohol Drinking on an empty stomach you can tell the affects much more quickly CD Propulsion Peristaltic gt Grinding The most gt vigorous peristalsis and mixing action occur close to the pylorus waves move from the fundus toward the pylorus Pyloric valve slightly opened 65 Retropulsion The pyloric end of the stomach acts as a pump that delivers small amounts of chyme into the duodenum simultaneously forcing most of its contained material backward into the stomach Figure 2319 Regulation of Gastric Emptying As chyme enters the duodenum Receptors respond to stretch and chemical signals Stretch receptors receptors that respond to a filling of chyme Chemo receptorsreceptors that are sensitive to chemical changes that occur ie the low pH of the contents of the stomach is not suitable for other parts of the body So it sends signal to the brain to slow down release of chemicals and enzymes Enterogastric reflex and enterogastrones inhibit gastric secretion and duodenal mng How fast something is broken down and absorbed depends on the contents of the stomach Carbohydraterich chyme moves quickly through the duodenum because it started digestion in the mouth Fatty chyme remains in the duodenum 6 hours or more Nerve impulses inhibit peristalsis in stomach wall From CNS quot 3 Vagus nerve To CNS Duodenum fills with chyme Sensory nerve impulses travel to central nervous system Sensory stretch receptors are stimulated
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