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Health Sciences
HSCI 100
Nienke Van Houten

Chapter 15: digestive system FUNCTION: - Ingests food, digests food - Absorbs nutrients, eliminates wastes Digestive process 1. Ingestion – intake of food via mouth 2. Digestion – mechanically/chemically breaking down food into subunits 3. Movement – food must be moved along the GI tract in order to fulfill all functions 4. Absorptions – movement of nutrients across GI tract wall to be delivered to cells/tissues via blood 5. Elimination – removal of indigestible molecules ORGANS - Mouth o Teeth chew food, tongue positions and tastes food o Begins digestion of carbohydrates - Pharynx o Passage for food and air. Role in swallowing - Esophagus o Muscular tube. Moves food from pharynx to stomach - Stomach o J shaped muscular sac for food storage o Secretes gastric juice (pepsin & HCl) o Churns food with gastric acid  creates chyme o Protein digestion begins - Small intestine o Long, muscular tube o Mixes food with bile + intestinal/pancreatic enzymes o Digests most nutrients – carb/protein/fat digestion completed o Absorbs most nutrients and water - Large intestine o Colon  Muscular tube  Absorbs water and some nutrients  Stores waste materials (feces) o Cecum  Blind pouch @ junction of small/large intestines o Rectum  Region of large intestine, passage for feces  Stretching of wall stimulates defecation reflex o Anal canal  Regulates defecation  Anus – expels feces ACCESSORY ORGANS - Salivary glands o 3 pairs of glands that secrete saliva (moistens food) o Enzyme (amylase) in saliva beings starch digestion - Liver o Secretes bile  emulsifies fat o Plays role in processing and storing certain nutrients - Gallbladder o Small sac stores bile o Release bile into small intestine - Pancreas o Gland behind stomach o Secretes enzymes that digests all major nutrients o Secretes buffers that neutralize HCl from stomach o Releases secretions into small intestine LAYERS OF GI TRACT - Lumen = hollow area of GI tract which food/fluids travel - Mucosa – innermost layer producing mucus (protect lining & produce digestive enzymes) - Submucosa – 2 layer of loose connective tissue (contain blood vessels, lymphatic vessels, nerves) rd - Muscularis – 3 layer made of 2 layers of smooth muscle. Moves food along GI tract - Serosa – outer lining part of peritoneum – covers abdominal organs SWALLOWING: The Mouth – begins mechanical & some chem digestion, monitors food quality, moistens/manipulates food - Salivary glands (sublingual, submandibular, parotid) – secrete salivary amylase enzyme that begins carb digestion - starch - Tonsils - @ back of mouth & other lymphatic tissues important in fighting disease - Tongue – skeletal muscle. Covered in taste buds & assist in MECHANICAL breakdown + movement of food -  bolus (mass of chewed food) moves towards pharynx(throat) - TEETH o function: mechanical digestion – break food into smaller pieces  incisor – clip & slice  canines – puncture & tear  molars + premolars – crush o structure:  regions: crown – above gum, root – below gum  layers: pulp (innermost with blood vessels/nerves), dentin (hard/bonelike), enamel (nonliving, covers crown) SWALLOWING – process - voluntary 1. tongue pushes food bolus toward pharynx/esophagus closed - involuntary 2. reflex movement of soft palate prevents food from entering nasal cavity 3. muscles contract, forcing bolus toward esophagus (peristalsis) 4. epiglottis closes the opening to resp system 5. muscle ring @ top of esophagus relaxes, opening esophagus. Food pushed in – peristalsis THE STOMACH - function: store food/regulate release of food to small intestine, liquefying food, carrying out initial chem digestion of proteins Heartburn - burning sensation in esophagus - occurs when acid from stomach passes into esophagus (acid reflux) - GERD – gastroesophageal reflux disease – chronic heartburn Small intestine - chem digestion + absorption - Averages 6m - Duodenum (liver/gallbladder/pancreas connect)  jejunum, ileum o Bile – secreted by gallbladder into small intestine to emulsify fats o Large SA from villi&microvilli absorb digested food o Amino/sugars enter capillaries while fatty acids & glycerol enter lacteals o Most chem digestion/absorption in 2 and 3 section - Out of small intestine: o Carbohydrate absorption  Salivary amylase (mouth), amylase (pancreas), maltase+sucrose+lactase (Small intestine) o Protein absorption  Pepsin (stomach), trypsin +chymotrypsin+carboxypepidase (pancreas) o Fat absorption  Lipase (pancreas) ORGANS IN DIGESTION (key) - Pancreas – produce digestive enzymes that act in small intestine o Fish shaped spongy organ behind stomach o Functions:  1. Secretes enzymes into small intestine  Trypsin digests proteins  Lipase digests fat  Pancreatic amylase digests carbs  2. Secretes bicarbonate into small intestine to neutralize stomach acid  3. Secrete insulin in blood to keep blood sugar levels under control when blood glucose is rising  Release glucagon when blood sugar is low - Liver & Gallbladder – produces bile (Stored in gallbladder) releases into small intestine o Filters blood from GI tract (removes poison/detox blood) o Removes iron, vitamin A D E K B12 from blood & stores o Stores glucose as glycogen & breaks down to retain blood glucose levels o Makes plasma proteins & regulates cholesterol by making bile salts o Bile used to emulsify fat o Breaks down hemoglobin  bilirubin (part of bile)  HDL = cholesterol used to make bile (good cholesterol) Liver disorders - Jaundice o Bile pigments build up and leak into blood (yellow colour) o In newborns: due to change in haemoglobin forms o Result of haemolytic disease where mothers antibodies attack baby’s Rh + RBC - Hepatitis o Inflammation of the liver. From hep A,B,C - Cirrhosis o Liver becomes fatty & tissue replaced by fibrous scar tissue  Alcoholics + obese ppl  = liver failure cuz liver cannot regenerate as fast as it is being damaged LARGE INTESTINE - Cecum, colon, rectum, anal canal - Appendix = projection that plays minor role in fighting infections - Functions: o Absorb remaining h2o to prevent dehydration o Absorbs vitamins (b & K ) produced in intestinal flora (bacteria) o Forms and rids of body feces through anus Colon & rectum disorders - Diarrhea: increased peristalsis & water is not reabsorbed due to infection/nervous stimulation - Constipation: condition where feces dry and hard. Can be controlled by water & fiber - Hemorrhoids: enlarged/inflamed blood vessels of anus due to chronic constipation, pregnancy, aging, anal intercourse - Diverticulosis: occurrences of pouches of mucosa from weak spots in muscularis layer (often in colon) - Irritable bowel syndrome (IBS): muscularis layer contracts with power but without its normal coordination == chronic diarrhea/ ab pain - Inflammatory bowel disease/colitis (IBD): group of inflammatory disorders = ulcerative colitis, crohn’s disease - Polyps & cancer – small growth in epithelial lining that is either benign/malignant (tend to be large intestine/colon) Hormonal control in digestion - Gastrin: in stomach o Digestion of stomach by food, presence of partially digested proteins in stomach - Vasoactive intestinal peptide o Presence of acid chime in small intestine - Secretin o Presence of acidic chime in small intestine (target pancreases) - Cholecystokinin o Arrival of chime-containing lipids (target = pancreas, gallbladder) Iclickr: Where does the chemical digestion of PROTEINS begin? Stomach Which of the following is true? Although protein digestion begins in stomach pancreatic enzymes break final polypeptide chains in amino acids CHAPTER 16: URINARY SYSTEM Functions: - 1. Excretion of metabolic wastes o Lungs – heat, water, co2 o Skin – heat, water, bicarbonate ions, salts, urea, uric acid o Organs of GI – solid wastes/some metabolic waste o Kidneys – form urine (mix of water and solutes), h2o, bicarbonate ions, inorganic salts, H+, urea, uric acid, creatinine - 2. Maintenance of water-salt balance - 3. Maintenance of pH - 4. Hormone secretion – renin & erythropoietin Organs involved - Kidney o Produce urine, conserves water, regulates pH, stimulates production of RBC, transforms vitamin D into active form - Ureter o Transports urine from kidneys to bladder o Urinary bladder – stores urine - Urethra – transports urine from urinary bladder to outside body EXCRETION - Mostly of nitrogenous wastes o Urea – breakdown of aminos in liver. Need to get rid of ammonia  Ammonia + co2 = urea + water o Uric acid – breakdown of nucleotides  Crystallized uric acids in joints cause gout o Creatinine – made by muscle cells from breakdown of creatine phosphate KIDNEYS: - Covered by connective tissue - Structure: outer region, renal cortex, renal medulla, renal pelvis nephrons = filters of kidneys structure: - Renal corpuscle = portion where fluid is filtered from blood o Consist of glomerular capsule (bowman’s capsule) o Glomerulus – knot of capillaries inside glomerular capsule (bowman’s capsule) o Pores produce blood filtrate – special cells, podocytes, connect epithelium to capillary endothelium - Blood enters glomerulus through afferent (incoming) arteriole, leaves out of efferent - Renal tubule = substances removed and added to filtrate o 1 – proximal convoluted tubule – lots of microvilli for reabsorption of substances in filtrate  epithelial layer with brush border of microvilli to allow reabsorption of filtrate components in tube lumen o 2 – loop of the nephron (loop of henle)  U shaped structure with descending limb to allow water to leave & ascending limb that pushes out salt o 3
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