Digestive System Notes PDF

 FUNCTION Digestion ○ Breakdown of ingested food ○ Absorption of nutrients into the blood Once the nutrients are absorbed by the digestive system they are transported by the blood to the tissues for metabolism. ○ Production of cellular energy (ATP) ○ Constructive and deg...

 FUNCTION Digestion ○ Breakdown of ingested food ○ Absorption of nutrients into the blood Once the nutrients are absorbed by the digestive system they are transported by the blood to the tissues for metabolism. ○ Production of cellular energy (ATP) ○ Constructive and degradative cellular activities TYPES OF DIGESTION MECHANICAL AND CHEMICAL DIGESTION  TYPES OF DIGESTION Digestion is a catabolic process in which large complex molecules (carbohydrates, lipids, proteins, nucleic acids) are broken down into simpler monomers (monosaccharides, glycerol and fatty acids, amino acids, and nucleotides) which can be absorbed by the body. MECHANICAL DIGESTION  MECHANICAL DIGESTION In mechanical there is no chemical change in the food. The food is simply broken down into smaller pieces and mixed with digestive juices secreted in the body. Ex. Mastication (chewing) CHEMICAL DIGESTION  MECHANICAL DIGESTION In chemical digestion the is a chemical change in the food. The polymers are broken down into monomers commonly by hydrolysis reactions carried out by enzymes contained within the digestive juices. SIX PROCESS OF DIGESTION INGESTION - PROPULSION - MECHANICAL DIGESTION CHEMICAL DIGESTION - ABSORPTION - DEFECATION  SIX PROCESS OF DIGESTION 1. Ingestion – getting food into the mouth 2. Propulsion – moving foods from one region of the digestive system to another 3. Mechanical digestion Mixing of food in the mouth by the tongue Churning of food in the stomach Segmentation in the small intestine  SIX PROCESS OF DIGESTION 4. Chemical Digestion Enzymes break down food molecules into their building blocks Each major food group uses different enzymes ➔Carbohydrates are broken to simple sugars ➔Proteins are broken to amino acids ➔Fats are broken to fatty acids and alcohols  SIX PROCESS OF DIGESTION 5. Absorption End products of digestion are absorbed in the blood or lymph Food must enter mucosal cells and then into blood or lymph capillaries 6. Defecation Elimination of indigestible substances as feces SIX PROCESS OF DIGESTION INGESTION PROPULSION MECHANICAL DIGESTION CHEMICAL DIGESTION ABSORPTION DEFECATION  DIVISION OF DIGESTIVE SYSTEM ORGANS ALIMENTARY CANAL - ACCESSORY ORGANS  DIVISION OF DIGESTIVE SYSTEM ALIMENTARY CANAL ACCESSORY ORGANS Mouth Salivary glands Pharynx Teeth Esophagus Pancreas Stomach Liver Small intestine Gallbladder Large intestine Anus DIGESTIVE ORGANS  ALIMENTARY CANAL Mouth - Pharynx - Esophagus - Stomach - Small intestine - Large intestine - Anus MOUTH (ORAL CAVITY)  MOUTH (ORAL CAVITY) Mastication (chewing) of food Mixing masticated food with saliva Initiation of swallowing by the tongue Allowing for the sense of taste  SALIVARY GLAND / SALIVA Salivary Glands Saliva-producing glands Parotid glands – located anterior to ears Submandibular glands Sublingual glands Saliva Mixture of mucus and serous fluids Helps to form a food bolus Contains salivary amylase to begin starch digestion Dissolves chemicals so they can be tasted  TEETH The role is to masticate (chew) food Humans have two sets of teeth - Deciduous (baby or milk) teeth - 20 teeth are fully formed by age two  TEETH Crown – exposed part ○ Outer enamel ○ Dentin ○ Pulp cavity Neck ○ Region in contact with the gum ○ Connects crown to root Root ○ Periodontal membrane attached to the bone ○ Root canal carrying blood vessels and nerves PHARYNX  PHARYNX Serves as a passageway for air and food Food is propelled to the esophagus by two muscle layers ○ Longitudinal inner layer ○ Circular outer layer Food movement is by alternating contractions of the muscle layers (peristalsis) ESOPHAGUS  ESOPHAGUS Runs from pharynx to stomach through the diaphragm Conducts food by peristalsis (slow rhythmic squeezing) Passageway for food only (respiratory system branches off after the pharynx) ESOPHAGUS - TISSUE LINING Mucosa Innermost layer Moist membrane - Surface epithelium - Small amount of connective tissue (lamina propria) - Small smooth muscle layer ESOPHAGUS - TISSUE LINING Submucosa Just beneath the mucosa Soft connective tissue with blood vessels, nerve endings, and lymphatics ESOPHAGUS - TISSUE LINING Muscularis externa – smooth muscle Inner circular layer Outer longitudinal layer Serosa Outermost layer – visceral peritoneum Layer of serous fluid-producing cells STOMACH  STOMACH Located on the left side of the abdominal cavity Food enters at the cardioesophageal sphincter Regions of the stomach Cardiac region – near the heart Fundus Body Pylorus – funnel-shaped terminal end  STOMACH Food empties into the small intestine at the pyloric sphincter Rugae – internal folds of the mucosa External regions - Lesser curvature - Greater curvature Rugae  STOMACH Acts as a storage tank for food Site of food breakdown Chemical breakdown of protein begins Delivers chyme (processed food) to the small intestine  STOMACH Simple columnar epithelium Mucous neck cells (goblet cells) – produce a sticky alkaline mucus Gastric glands – secrete gastric juice Chief cells – produce protein-digesting enzymes (pepsinogens) Parietal cells – produce hydrochloric acid Endocrine cells – produce gastrin  STOMACH Gastric pits formed by folded mucosa Glands and specialized cells are in the gastric gland region SMALL INTESTINE  SMALL INTESTINE The body’s major digestive organ all digestion of food is completed in this organ Site of nutrient absorption into the blood Muscular tube extending from the pyloric sphincter to the ileocecal valve Suspended from the posterior abdominal wall by the mesentery  SMALL INTESTINE Duodenum (25cm = 10 inches) “12 finger widths long” - Attached to the stomach - Curves around the head of the pancreas - Where bile and pancreatic juices enter the alimentary canal Jejunum (2.5m = 8 feet) “empty” - Attaches anteriorly to the duodenum Ileum (3.6m = 12 feet) “twisted” - Extends from jejunum to large intestine SMALL INTESTINE  SMALL INTESTINE Duodenum and Accessory Glands Connected  SMALL INTESTINE LINING Villi are small fingerlike structures formed by the mucosa Give the small intestine more surface area for absorption Fold in the intestine are called circular folds or plicae circulares Deep folds of the mucosa and submucosa Do not disappear when filled with food The submucosa has Peyer’s patches (collections of lymphatic tissue)  VILLI Absorptive cells are found on the surface epithelium which are simple columnar microvilliated epithelium  VILLI ◻ Blood capillaries are below the surface epithelium and this is where monosaccharides, amino acids, and nucleic acids enter into the bloodstream and are taken to the liver for processing  VILLI ◻ Lacteals (specialized lymphatic capillaries) where lipids are absorbed and eventually re-enter the blood stream to be taken to the liver for processing. LARGE INTESTINE (COLON)  LARGE INTESTINE (COLON) Larger in diameter, but shorter than the small intestine Frames the internal abdomen Cecum – saclike first part of the large intestine  LARGE INTESTINE (COLON) Appendix ○ Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis) ○ Hangs from the cecum  LARGE INTESTINE (COLON) Colon ○ Ascending ○ Transverse ○ Descending ○ S-shaped sigmoidal Rectum Anus – external body opening  LARGE INTESTINE (COLON) FUNCTIONS Absorption of water Eliminates indigestible food from the body as feces Does not participate in digestion or absorption of digested food Goblet cells produce mucus to act as a lubricant Site of production of Vitamin K by symbiotic bacteria which live off the remains of food that have not been digested or absorbed in the small intestine. These bacteria produce over 50% of fecal matter. ACCESSORY ORGANS Pancreas - Liver - Gallbladder PANCREAS  PANCREAS Produces a wide spectrum of digestive enzymes that break down all categories of food Enzymes are secreted into the duodenum Alkaline fluid introduced with enzymes neutralizes acidic chyme Endocrine products of pancreas ○ Insulin ○ Glucagon LIVER & GALLBLADDER  LIVER & GALLBLADDER Largest gland in the body Located on the right side of the body under the diaphragm  LIVER & GALLBLADDER Consists of four lobes suspended from the diaphragm and abdominal wall by the falciform ligament Connected to the gall bladder via the common hepatic duct Produced by cells in the liver  LIVER & GALLBLADDER Composition ○ Bile salts ○ Bile pigment (mostly bilirubin from the breakdown of hemoglobin) ○ Cholesterol ○ Phospholipids ○ Electrolytes  LIVER & GALLBLADDER Sac found in hollow fossa of liver Stores bile from the liver by way of the cystic duct Bile is introduced into the duodenum in the presence of fatty food Gallstones can cause blockages NUTRITION  NUTRITION Categories of nutrients ○ Carbohydrates ( macro) ○ Lipids (macro) ○ Proteins (macro) ○ Vitamins (micro) ○ Mineral (micro) ○ Water A lack of the proper nutrients or an imbalance in the correct amounts of each is called malnutrition. Even though a person is obese they often suffer from malnutrition!  NUTRITION Carbohydrates ○ Most are derived from plants ○ Exceptions: lactose from milk and small amounts of glycogens from meats Lipids ○ Saturated fats from animal products ○ Unsaturated fats from nuts, seeds, and vegetable oils ○ Cholesterol from egg yolk, meats, and milk products  NUTRITION Proteins ○ Complete proteins – contain all essential amino acids Most are from animal products ○ Legumes and beans also have proteins, but are incomplete Vitamins ○ Most vitamins are used as cofactors and act with enzymes many are produced by plants ○ Found in all major food groups  NUTRITION Minerals ○ Play many roles in the body ○ Most mineral-rich foods are vegetables, legumes, milk, and some meats DISEASES OF DIGESTIVE SYSTEM HEART BURN - ULCER - CROHN’S DISEASE - COLON CANCER HEART BURN  HEARTBURN (ACID REFLUX) This is due to acid from the stomach entering into the esophagus which results in a burning sensation. In chronic severe cases this can lead to damage, ulceration, scarring, and possibly cancer of the esophagus if not treated.  ULCER Ulcers occur when the lining of the stomach or the duodenum becomes weakened and exposed to the effects of digestive enzymes and stomach acid. It eventually will digest a hole through the mucosa and may cause severe bleeding if a blood vessel of the stomach is involved. It is now known that ulcers are closely associated with infection by a bacteria called Helicobacter pylori.  CROHN’S DISEASE Crohn's Disease is an inflammatory disease of the bowel. It can cause fever, pain, diarrhea and significant loss of weight. Crohn's Disease can affect any part of the bowel, but most typically affects the lower end of the small intestine, where it joins the large intestine. The intestinal wall becomes thick and inflamed, producing ulcers and fissures. The intestinal space becomes so narrow.  COLON CANCER Cancer starts in the inner layer and can grow through some or all of the other layers. Knowing a little about these layers is helpful because the stage (extent of spread) of a cancer depends to a great degree on which of these layers it affects.  COLON CANCER Cancer that starts in the different areas may cause different symptoms. Colon and rectum cancers probably develop slowly over a period of several years. Polyps are also known as adenomas. Removing the polyp early may prevent it from becoming cancer.  COLON CANCER Over 95% of colon and rectal cancers are adenocarcinomas. These are cancers of the cells that line the inside of the colon and rectum. Colon and rectal cancer have many features in common and are often referred to together as colorectal cancer. NEXT TOPIC: CIRCULATORY SYSTEM