Function of Digestive System: Break down carbohydrates, lipids, and proteins (polymers) into small molecules. Allows absorption of nutrients (ions and molecules) into bloodstream.

Alimentary canal Accessory glands

Mouth Mechanical digestion: teeth! Chemical digestion: saliva amylase (salivary glands) mucin (mucins + H 2 O = mucous) Saliva also regulates pH in mouth. pH: 7.0

Esophagus Peristalsis: wave of muscular contractions (reflex)

Stomach Mechanical & chemical: reduce food to uniform consistency and osmolarity. Gastric juice = HCl (parietal cells) + pepsin (chief cells) Mucus (goblet cells) protects stomach from HCl pH: 2.0

Small intestine Functions: Digestion of lipids and carbohydrates Protein processing Absorption of nutrients and water. pH: 7.8

Starts in oral cavity with salivary amylase (ptyalin). Continues in small intestine with pancreatic amylases. Polysaccharides / disaccharides >> monosaccharides. Types of carbs? Plants >> starch, cellulose Animals >> glycogen Carbohydrate digestion

Starts in stomach: –Chief cells secrete pepsinogen –Pepsinogen + HCl = pepsin –Proteins denatured by HCl; broken down by pepsin Then small intestine: –digested by trypsin and other pancreatic enzymes Proteins >> peptide chains >> amino acids Protein digestion

Lipid digestion Small intestine: –bile salts from gall bladder emulsify lipids. –pancreatic lipase digests smaller droplets. –NaHCO 3 from pancreas increases pH. Lipids >> glycerol, fatty acids, & glycerides.

Hormones Molecules (e.g. peptide or steroid) produced in one part of an organism that trigger a specific cellular reaction in target tissues.

Exocrine glands: secrete enzymes that are transported through ducts. (e.g. sweat glands, salivary glands) Endocrine glands: secrete hormones into circulatory system (no ducts). (e.g. pituitary gland, adrenal gland)

Pancreas: “mixed” gland Exocrine products: sodium bicarbonate (NaHCO 3 ) digestive enzymes (acinar cells) –lipase – lipids –trypsin – proteins –amylase – starches

Pancreas: “Islets of Langerhans” Regulate carbohydrate metabolism (glucose levels in blood). vascularized clusters of endocrine cells.

Islets of Langerhans: alpha cells = glucagon beta cells = insulin

Glucagon: Promotes the release of glucose from glycogen stores. This causes blood glucose levels to increase (hyperglycemia). Typically released during fasting.

Insulin: Glucose is stored in liver (hepatic tissue) and fat (adipose tissue) as glycogen. When insulin is released, these tissues uptake glucose from the bloodstream. This causes blood glucose levels to decrease (hypoglycemia). Typically released after feeding.

Diabetes mellitus characterized by hyperglycemia million people, or 7% of US population

Type I Diabetes Insulin deficiency Autoimmune disorder Islet cells destroyed by immune system Treat by injection Not hereditary

Insulin resistance “adult-onset” diabetes Over 90% of diabetes Gradual onset Hereditary Associated with age, obesity, physical, ethnic background and inactivity Treated by diet Type II Diabetes

CarbohydratesLipidsProteins Mouth Esophagus AmylaseLipase StomachPepsin (Polypeptides) Lumen of small intestine Amylase (Monosaccharides) (Disaccharides, Trisaccharides) Bile salts & lipase (Monoglycerides & Fatty acids) Trypsin, et al.! (Short peptides & amino acids) Epithelium Monoglycerides & Fatty Acids of smallMonosaccharidesTriglyceridesAmino acids intestineChylomicrons

CarbohydratesLipidsProteins Mouth Esophagus AmylaseLipase StomachPepsin (Polypeptides) Lumen of small intestine Amylase (Monosaccharides) (Disaccharides, Trisaccharides) Bile salts & lipase (Monoglycerides & Fatty acids) Trypsin, et al.! (Short peptides & amino acids) Epithelium Monoglycerides & Fatty Acids of smallMonosaccharidesTriglyceridesAmino acids intestineChylomicrons

CarbohydratesLipidsProteins Mouth Esophagus AmylaseLipase StomachPepsin (Polypeptides) Lumen of small intestine Amylase (Monosaccharides) (Disaccharides, Trisaccharides) Bile salts & lipase (Monoglycerides & Fatty acids) Trypsin, et al.! (Short peptides & amino acids) Epithelium Monoglycerides & Fatty Acids of smallMonosaccharidesTriglyceridesAmino acids intestineChylomicrons

CarbohydratesLipidsProteins FACILITATED DIFFUSION & TRANSPORT Mouth Esophagus AmylaseLipase StomachPepsin (Polypeptides) Lumen of small intestine Amylase (Monosaccharides) (Disaccharides, Trisaccharides) Bile salts & lipase (Monoglycerides & Fatty acids) Trypsin, et al.! (Short peptides & amino acids) Epithelium Monoglycerides & Fatty Acids of smallMonosaccharidesTriglyceridesAmino acids intestineChylomicrons

CarbohydratesLipidsProteins Mouth Esophagus AmylaseLipase StomachPepsin (Polypeptides) Lumen of small intestine Amylase (Monosaccharides) (Disaccharides, Trisaccharides) Bile salts & lipase (Monoglycerides & Fatty acids) Trypsin, et al.! (Short peptides & amino acids) Epithelium Monoglycerides & Fatty Acids of smallMonosaccharidesTriglyceridesAmino acids intestineChylomicrons

CarbohydratesLipidsProteins BLOODSTREAM Mouth Esophagus AmylaseLipase StomachPepsin (Polypeptides) Lumen of small intestine Amylase (Monosaccharides) (Disaccharides, Trisaccharides) Bile salts & lipase (Monoglycerides & Fatty acids) Trypsin, et al.! (Short peptides & amino acids) Epithelium Monoglycerides & Fatty Acids of smallMonosaccharidesTriglyceridesAmino acids intestineChylomicrons