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The Digestive System Hepatitis from Salsa?! What is Digestion? Mechanical and Chemical breakdown of foods and absorption of resulting nutrients Mechanical Digestion – breaks down larger pieces of food into smaller ones without changing chemical composition Chemical Digestion – Breaks down food to simpler chemicals Digestion Digestive system consists of the Alimentary canal Mouth, pharynx, esophogus, stomach, small intestine, large intestine, rectum, anus Aprox. 8 meters long Accessory organs Salivary glands, liver, gallbladder, pancreas Alimentary Canal Structure Mucosa – innermost layer, protection, secretion and absorption Surface epithelium, underlying connective tissue, some smooth muscle In some regions, folded with tiny projections into the lumen increases absorptive area Alimentary Canal Submucosa Loose connective tissue, glands, blood vessels, lymphatic vessels, nerves Nourish surrounding tissues, carry away absorbed materials Alimentary Canal Muscular layer Produces movement 2 coats smooth muscle and some nerves Inner muscular layer encircles tube When this layer contracts, diameter of tube decreases Outer muscular layer run lengthwise When these contract, tube shortens Alimentary Canal Serosa or serous layer Outer covering of tube Protect underlying tissues, secrete serous fluid Lubricates tube’s outer surface Prevents friction from other organs Movements of Alimentary Canal 2 basic types Mixing movements Propelling movements Mixing occurs when smooth muscles in small segments of tube contract rhythmically Full stomach waves of muscular contraction move along walls from one end to the other, mixing food with digestive juices Movements of Alimentary Canal Propelling movements – wavelike motion called peristalsis Ring of contraction appears in wall of tube, simultaneously, muscular wall just ahead of ring relaxes ???? Which organs make up the digestive system? Describe the wall of the alimentary canal. Name the 2 types of movements that occur in the alimentary canal. The Mouth Receives food and begins digestion by mechanically breaking down food Mixes food with saliva Cheeks & Lips Cheeks – outer layers of skin, pads of SQ fat, muscles, inner linings of moist stratified squamous epithelium Lips – highly moveable structures that surround mouth opening. Have skeletal muscles and sensory receptors. Useful for detecting temperature & texture of foods Tongue Nearly fills oral cavity when mouth is closed, covered by mucous membrane Frenulum connects midline of tongue to floor of mouth Body is mostly skeletal muscle, mix food particles with saliva, move food toward pharynx, move food underneath teeth for chewing Papillae – rough projections that provide friction, also have taste buds Root of tongue anchored to hyoid bone Covered with masses of lymphatic tissue – lingual tonsils Palate Forms roof of oral cavity Anterior part – hard palate Posterior part – soft palate Soft palate forms muscular arch which connects to uvula During swallowing, soft palate is drawn upward, closing off nasal cavity Palate In back of mouth, closely associated with palate are the palatine tonsils Help protect against infection Other masses of lymphatic tissue – pharyngeal tonsils (adenoids) are on the border of soft palate and pharynx May swell and block airway/swallowing ???? How does the tongue function as part of the digestive system? What is the role of the soft palate in swallowing? Teeth 2 different sets of teeth during development Primary teeth – deciduous Secondary teeth – permanent Deciduous teeth usually appear at 6 months of age through 2 to 4 years 20 Deciduous teeth, 10 in each jaw Teeth Pressure from secondary teeth push deciduous teeth out of their sockets May begin to appear at 6 years, but not fully develop until 3rd molars (wisdom teeth) appear between 17 – 25 32 teeth in total, 16 in each jaw Teeth Each tooth consists of 2 main portions Crown – projects beyond gum Root – anchored to alveolar process of jaw Enamel covers crown, consists of calcium salts, hardest substance in body Damaged enamel does not regenerate Teeth Dentin – bulk of tooth beneath enamel, similar to bone Surrounds tooth’s central canal (pulp cavity) Pulp cavity contains blood vessels, nerves, connective tissue Blood vessels and nerves reach this cavity through tubular roots canals that extend to root Cementum & periodontal ligament enclose root and firmly attach tooth to jaw ???? How do primary teeth differ from secondary teeth? Describe the structure of a tooth. Explain how a tooth is attached to the bone of the jaw. Salivary Glands Saliva Moistens food particles Helps to bind Begins chemical digestion of carbs Solvent: allows food to be tasted Cleanses mouth & teeth Salivary Secretions Serous cells – produce watery fluid that contains amylase Mucous cells – secrete mucus, help lubricate during swallowing Parasympathetic nerve impulses trigger salivary glands to secrete saliva Mouth waters when thinking about Chipotle Major Salivary Glands 3 main pairs (parotid, submandibular, sublingual) Many minor glands in cheeks, tongue, palate Major Salivary Glands Parotid – largest salivary glands Anterior and inferior to each ear, between skin of cheek and masseter muscle Secretes clear, watery fluid rich in amylase Major Salivary Glands Submandibular – found on floor of mouth, inside surface of lower jaw Secretions are mainly serous with few mucus cells Thicker fluid than parotid Major Salivary Glands Sublingual – smallest Floor of mouth inferior to tongue Primarily mucus cells Secretions are thick and stringy ???? What is the function of saliva? What are the 3 major salivary glands? Where are they located? What stimulates salivary glands to secrete saliva? Pharynx Pharynx connects nasal and oral cavities with larynx and esophagus Nasopharynx Oropharynx Laryngopharynx Swallowing Mechanism • 3 main stages • 1st is voluntary; tongue forms bolus of food, forces it into pharynx • 2nd begins as food stimulates sensory receptors around pharyngeal opening. This triggers a swallowing reflex with the following steps… Swallowing Mechanism Soft palate raises, preventing food from entering nasal cavity Hyoid bone and larynx are elevated. Epiglottis closes off trachea Tongue is pressed against soft palate, closing off oral cavity Swallowing Mechanism Longitudinal muscles in pharyngeal wall contract, bringing pharynx upward towards food Muscles in lower pharynx relax, opening esophagus Peristaltic wave beings in pharyngeal muscles, forces food into esophagus Swallowing Mechanism 3rd stage, peristalsis transports food in the esophagus to stomach Esophagus Straight, collapsible tube, 25cm long Food passageway from pharynx to stomach Penetrates diaphragm at the esophageal hiatus Mucous glands scattered throughout submucosa Esophagus Just above where esophagus joins stomach is the cardiac sphincter Prevents regurgitation of stomach contents Stomach J-shaped, pouchlike organ in upper left quadrant Has capacity of about 1liter or more Has Rugae – thick folds of mucosal and submucosal layers that disappear when stomach is distended Mixes food with gastric juice, starts protein digestion, minimal absorption, moves food to small intestine Stomach Divided into cardiac, fundic, body, and pyloric regions Cardiac: Small area near esophageal opening Fundic: Balloons superior to cardiac region, temporary storage area Stomach Body: Main part of stomach btwn fundic and pyloric Pyloric: Narrows and becomes pyloric canal as it approaches small intestine Pyloric Sphincter: Muscle valve at end of pyloric area that controls gastric emptying Gastric Secretions Mucous membrane that forms lining of stomach is thick and contains many gastric pits which lead to gastric glands Gastric glands have 3 types of cells: Mucous cells - goblet cells Chief cells – digestive enzymes Parietal cells – hydrochloric acid Together, these form gastric juice Gastric Secretions Component Source Function Pepsinogen Chief cells Inactive form of pepsin Pepsin Pepsinogen + HCl Protein splitting enzyme digests nearly all dietary protein Hydrochloric Acid Parietal cells Provides acidic environment needed for conversion of pepsinogen pepsin and for action of pepsin Mucus Goblet cells and mucous Provides viscous, alkaline glands protective layer on inside of stomach wall Intrinsic Factor Parietal cells Aids in Vit B12 absorption https://study.com/academy/lesson/digestive-system-i-theupper-gastrointestinal-tract.html ???? What are the secretions of chief and parietal cells? Which is the most important digestive enzyme in gastric juice? Why doesn’t the stomach digest itself? Mixing and Emptying Following a meal, the mixing movements of the stomach wall form chyme – a semifluid paste of food particles and gastric juices Peristaltic waves push chyme to pyloric region As chyme accumulates near pyloric sphincter, this muscle starts to relax Stomach contractions push chyme into small intestine a little at a time Mixing and Emptying Rate of emptying depends on consistency and type of food Liquids pass faster than solids Fatty foods – remain in stomach for 3-6 hrs Proteins move through quicker than fats Carbohydrates move the fastest As chyme enters small intestine, accessory organs begin to add their secretions Pancreas Closely associated with small intestine Near C-shaped curve of duodenum Pancreatic acinar cells secrete pancreatic juice and make up bulk of organ Pancreatic duct extends length of pancreas Hepatopancreatic sphincter controls movement of juices into duodenum Pancreas Pancreatic juice contains many enzymes to digest fats, carbs, nucleic acids and proteins Pancreatic amylase – splits molecules of starch or glycogen into disaccharides Pancreatic lipase – breaks down triglycerides into fatty acids and glycerol Trypsin, chymotrypsin, carboxypeptidase – split bonds in proteins Liver Heaviest organ in body – about 3lbs Located in upper right quadrant, just below diaphragm Partially surrounded by the ribs Reddish-brown in color Well supplied with blood vessels Liver Functions General Function Specific Function Carb Metabolism Polymerizes glucose glycogen, breaks down glycogen to glucose, converts non-carbs to glucose Lipid Metabolism Oxidizes fatty acids, synthesizes lipoproteins, phospholipids and cholesterol; converts portions of carbs and proteins into fats Protein Metabolism Deaminates amino acids, forms urea, synthesizes plasma proteins; converts amino acids Storage Stores glycogen, iron, Vit A, D, B12 Blood Filtering Removes damaged RBC and foreign substances Detoxification Removes toxins from blood Secretion Secretes Bile Bile Yellowish – green liquid, continuously secreted from hepatic cells Contain: Water, bile salts, bile pigments (bilirubin & biliverdin), cholesterol, electolytes Affect fat globules by breaking them down into smaller droplets = emulsification Gallbladder Pear shaped sac on livers inferior surface Connects to cystic duct common hepatic duct common bile duct duodenum Stores bile between meals, reabsorbs water to concentrate bile, contracts to release bile to small intestine Hepatopancreatic sphincter guards exit Gall stones may block this sphincter Small Intestine Consists of 3 main parts: Duodenum – most fixed part, C-shaped Jejunum Ileum Jejunum and ileum lie free in peritoneal cavity Small intestine in lined with intestinal villi – increase surface area, increase absorption Small Intestine Most important absorbing organ of alimentary canal Breaks down molecules into most basic form to be absorbed Uses peristaltic movements Small Intestine Chyme moves slowly, taking 3-10hrs to pass through If small intestine wall becomes irritated a strong peristaltic rush may force contents through small intestine without absorbing water, nutrients or electrolytes = diarrhea Large Intestine 1.5 meters long Begins in lower right quadrant of abdominal cavity where ileum joins cecum From there, ascends on right side, crosses to left, and descends into pelvic cavity Opens to outside of body as the anus Large Intestine Absorbs water and electrolytes from remaining chyme Forms and stores feces Made up of: Cecum Colon Rectum Anal canal Large Intestine Cecum – closed end has the appendix Colon – divided into 4 portions Ascending colon – begins at cecum and travels upward Transverse colon – longest, most moveable part Descending colon – transverse colon turns abruptly downward Sigmoid colon – S-shaped curve that becomes the rectum Large Intestine Lacks villi Longitudinal muscle fibers form 3 distinct bands lengthwise (teniae coli) that extend the length of colon Exert tension lengthwise creating haustra, series of pouches Large Intestine Mucus is the only significant secretion Mucus protects wall of large intestine from abrasive action of material passing through it Diseases & Disorders Appendicitis Acute inflammation of appendix May be caused by obstruction of intestinal lumen Generalized abdominal pain that localized to right lower abdomen Nausea, vomiting, anorexia Rebound tenderness Cirrhosis Chronic disease of liver that causes destruction of liver cells Late signs: Bleeding gums, anemia, enlarged liver, jaundice, ascites Can only be confirmed with liver biopsy Causes: malnutrition associated with alcoholism, hepatitis Colitis Inflammation of the colon Signs: tenderness, discomfort Can be acute(bacterial) or chronic (allergy, emotional distress, or other disease) Colostomy Artificial opening of colon, allowing fecal material to be excreted through abdominal wall Named for area of colon involved (ascending, transverse, descending, sigmoid) Big emotional/physical adjustment Crohn’s Disease Inflammation of any portion of GI tract, but most common in ileum Involves all layer of intestinal wall edema, ulceration, narrowing, formation of abscesses/fistulas Symptoms: Diarrhea (4-6x daily), bloody stools, weight loss, difficulty handling stress Gastroenteritis Inflammation of stomach and intestines (traveler’s diarrhea, food poisoning) Symptoms: fever, nausea, abdominal cramping, diarrhea Treatment: Bedrest, increased fluid intake, antibiotics, IV fluids Gastroesophageal Reflux Disease (GERD) Backflow of gastric contents back through cardiac sphincter Symptoms: heartburn, angina-like pain, morning hoarseness, coughing Treatment: OTC antacids, H2 blockers (Pepcid AC) Hepatitis Inflammation and infection of liver than can result in destruction of liver cells and possibly death A,B, and C are the most common types Hepatitis A Transmits through fecal matter Symptoms: abdominal pain, jaundice, loss of appetite, nausea, fever Liver will heal over a few weeks - months Hepatitis B Transmitted through blood and body fluid Can cause chronic infection Has flu-like symptoms May cause liver damage Easily prevented with vaccine Hepatitis C May present without symptoms Spread through blood and body fluids 75-80% of people develop long-term infection and will need liver transplant In recent years, a medication called Harvoni has been developed than may cure the infection in 8-12 weeks Hernia Protrusion of internal organ through natural opening Types: Hiatal – stomach protrudes through diaphragm Inguinal – hernia of inguinal rings (near groin) Pancreatitis Inflammation of pancreas can be acute or chronic Symptoms: Epigastric pain not relieved by vomiting, a severe attack may cause severe pain, vomiting, rigid abdomen, tachycardia, fever Treatment: Complicated, decrease pancreatic secretions, relieve pain, maintain adequate fluids Peptic Ulcer Encircled lesion in mucous membrane lining of stomach, lower esophagus, duodenum, jejunum Duodenal - Heart burn, epigastric pain relieved by food, attacks occur when stomach is empty Gastric – heartburn, indigestion, pain in left epigastric area, feeling of fullness, cause pain after eating Ulcerative Colitis Inflammatory disease, often chronic, that affects mucosa of colon Produces congestion edema, mucosal lining breaks down, ulcers form Primarily affects young adult females Symptoms – frequent bloody stool, often containing mucus Ulcerative Colitis Causes: Family history, bacterial infection, emotional stress, autoimmune reaction Treatment: Controlling inflammation, maintaining nutrition and blood volume, preventing complications Bed rest, IV fluid, clear liquid diet, pain medication
