Mouth and Saliva

• Digestion begins in the mouth with saliva.
• Saliva moistens and lubricates food, and contains amylase to break down carbohydrates.

Salivary Glands

• Sublingual glands are the smallest and located under the tongue.
• Submandibular glands are at the lower jaw level, also called submaxillary glands.
• Parotid glands are the largest, found at cheek level.

Saliva Components and Functions

• Saliva consists mostly of water, mucus, and salivary amylase.
• Saliva breaks down starch into maltose.
• It moistens food, turning it into a bolus for easier swallowing.
• Saliva lubricates the food bolus.

Tooth Structure

• Crown: The portion above the gingiva (gums).
• Enamel: The outer layer covering the crown.
• Root: The portion beneath the gingiva.
• Cementum: The outer layer covering the root.
• Dentin: The substance between the enamel or cementum and the pulp cavity.
• Pulp Canal: The cavity containing blood vessels and nerves.

Oral Cavity Components

• Lips

• Gingiva (gums)

• Hard palate (roof of the mouth closer to the incisors)

• Soft palate (roof of the mouth closer to the uvula)

• Uvula

• Palatine tonsil (in the back of the throat)

• Papillae of the tongue (dots)

• Molars, premolars (front molars), canines, and incisors

• Pharynx: connects the oral and nasal cavities.

• Epiglottis: A flap that prevents the bolus from entering the trachea.

• Esophagus: Uses smooth muscle for peristalsis.

Stomach

• The J-shaped stomach is located on the left side of the body.
• Sphincters control the passage of food into and out of the stomach.
• Esophageal/cardiac sphincter: Prevents acid reflux.
• Pyloric sphincter: Controls the amount of food entering the small intestine.
• Rugae of mucosa: Folds that allow for expansion and increased surface area.
• Churning is facilitated by longitudinal, circular, and oblique smooth muscles.
• Pepsin: breaks down proteins.
• HCl: present in stomach
• Bolus becomes chyme in the stomach.

Stomach Lining and Function

• Mucosa: The stomach lining that secretes mucus, HCl, and water (gastric juices).
• Gastric juices break down digested food and kill microorganisms.
• The stomach mechanically digests food and stimulates the secretion of bile and pancreatic enzymes.
• Rugae: Folds within the stomach.
• Chyme: What food is called when it leaves the stomach.

Small Intestine (DJI)

• Duodenum: Connects to the stomach (30cm long).
• Jejunum: 3m long.
• Ileum: Connects to the large intestine (4m long).
• Mesentery membrane: Keeps the small intestine coiled.
• The small intestine is 2.5cm wide and 7m long.
• Most chemical digestion and nutrient absorption occurs here.
• Duodenum receives peptidase, amylase, and lipase (alkaline enzymes).
• Many nutrients enter the bloodstream via the small intestine.
• Fructose moves by facilitated diffusion into the epithelial cells.
• Amino acids, small peptides, vitamins, and most glucose molecules are pumped against the concentration gradient by villi epithelial cells, requiring ATP.
• Chylomicrons: Water-soluble globules transported into the lacteal (villus vessel).
• Ileocecal Valve: The valve between the ileum and cecum.

Large Intestine (Colon)

• Cecum: Connects to the ileum.
• Ascending colon
• Transverse colon: Connects the ascending and descending colon.
• Descending colon
• Sigmoid colon: Connects to the rectum.
• Rectum: Stores faeces.
• Anus: Where faeces exit.
• Water is reabsorbed in the large intestine.
• Bacteria in the large intestine produce fat-soluble vitamin K, which is absorbed and used by the body.

Accessory Organs (Not part of the Alimentary Canal)

Liver

• Secretes bile to break down fats.
• Bile is an emulsifier but does not contain enzymes.
• Bile neutralizes chyme and pancreatic juices.
• The hepatic portal vein carries nutrient-rich blood from the villi to the liver, which regulates nutrient distribution.
• The liver connects to the gallbladder and duodenum via the common bile duct (CBD).
• Glycogen is stored in the liver.

Gallbladder

• Excess bile is stored, then secreted into the duodenum.

Pancreas

• Releases insulin: Regulates blood sugar; excess energy becomes glycogen.
• Secretes enzymes to break down macromolecules.
• Produces lipase to break down lipids.
• Secretes glucagon to break down glycogen and release glucose.
• Releases pancreatic amylase.
• Connects to the common bile duct via the pancreatic duct.
• Sphincter of Oddi connects the CBD to the duodenum.
• Head is closest to duodenum
• Body
• Tail is the furthest

Fat Soluble Vitamins

• A, D, E, K

Water Soluble Vitamins

• B's, C's (flushed from urine and sweat)

Cancer

• Stages 0-IV indicate the size of the tumour.
• At stage IV, cancer cells can break off and spread (metastasize).

Glycogen

• A form of glucose stored in the liver and muscles.
• It is not consumed but made from excess glucose.

Glucagon

• A hormone that increases blood sugar by releasing it from cells.

Gastric Glands

• Gastric juice: Produced by gastric glands.
• Mucus cells: Secrete mucus to lubricate and protect the stomach lining.
• Chief cells: Secrete pepsinogen, an inactive form of pepsin.
• Parietal cells: Secrete hydrochloric acid (HCl).
• Located in the stomach.

Cell Types in Gastric Glands

• Lumen: Openings in the body.
• Mucous neck cell: Secretes mucus and bicarbonate.
• Parietal cells: Secrete HCl and intrinsic factor (Ca++ absorption).
• Enterochromaffin-like cell: secretes Histamine (stimulates acid).
• Chief cells: Pepsin (ogen) and gastric lipase
• D cells: Somatostatin (inhibits acid).
• G cells: Gastrin (stimulates acid).

Role of HCl

• Disrupts the extracellular matrix that binds cells together in meat and plant material.
• Creates a low pH (2) in gastric juice, killing most bacteria and denaturing proteins.
• Converts pepsinogen to active pepsin.
• HCl and pepsin form within the stomach lumen, not within the cells of the gastric glands.

Pepsin

• Pepsin is a protein-digesting enzyme (protease) that works best in an acidic environment.
• Produced by chief cells.
• Breaks peptide bonds and cleaves proteins into smaller polypeptides.
• Can also clip pepsinogen to pepsin (positive feedback).
• The stomach lining protects against self-digestion with mucus.
• Pepsin cell division creates a new epithelial tissue layer every three days.

Helicobacter Pylori and Ulcers

• Helicobacter pylori: An acid-tolerant bacterium that can cause stomach ulcers.

• Stomach ulcer: An opening in the stomach lining.

• Herbivores have the longest digestive tracts, with cellulase to break down cellulose.

Fats

• Composed of fatty acids.
• Emulsified by bile salts to form micelles.

Fatty Acids

• Enter epithelial cells and link to form triglycerides.

Triglycerides

• 3 fatty acids are attached to a glycerol.
• Combine with proteins in the Golgi body to form chylomicrons.

Chylomicrons

• Enter the lacteal and are transported away from the intestine.

Appetite-Regulating Hormones

• Leptin:

• produced by adipose tissue and suppresses appetite.

• Decreasing body fat causes leptin levels to fall, increasing appetite.

• Insulin: moves glucose into cells

• Triggered by increased blood-glucose levels and reduces hunger.

• PYY Hormone:

• Secreted by the small intestine after meals.

• Suppresses appetite and counters ghrelin stimulus.

• Ghrelin:

• Secreted by the stomach wall.

• Triggers feelings of hunger as mealtimes approach.

• Cow stomachs have four chambers.

• Rumination: The process of fermenting and regurgitating food before swallowing.

Liver Cirrhosis

• Liver cirrhosis is a condition where it slowly deteriorates and malfunctions due to chronic injury.
• Scar tissue progressively replaces healthy tissue, partially blocking blood flow.
• Impairs the liver's ability to fight infection, remove bacteria and toxins, process nutrients, hormones, drugs, and make proteins that regulate blood clotting, produce bile to absorb fat, including cholesterol and FS vitamins.
• A healthy liver can regenerate most of its own cells when damaged, with end-stage cirrhosis, the liver can no longer effectively replace damaged cells, a healthy liver is necessary for survival
• Destroys liver via growth of connective tissue
• Causes weakness, fatigue, loss of appetite, nausea, vomiting, weight loss, abdominal pain, bloating from accumulating fluid, itching, spider-like blood vessels on the skin
• Fatty liver → fibrosis → cirrhosis

Alcohol-Related Liver Disease

• For women, consuming two to three drinks—including beer and wine—per day and for men, three to four drinks per day, can lead to liver damage and cirrhosis.

Chronic Hepatitis C

• Results from contact with an infected person’s blood.
• Causes inflammation and damage to the liver over time, leading to cirrhosis.

Chronic Hepatitis B and D

• Chronic Hepatitis B and D: viral liver infections
• The hepatitis B virus is a liver infection that is spread by contact with an infected person’s blood, semen, or other body fluid. The hepatitis B vaccine is given to all infants and many adults to prevent the virus. Hepatitis D is another virus that infects the liver and can lead to cirrhosis, but it occurs only in people who already have hepatitis B.

Nonalcoholic Fatty Liver Disease (NAFLD)

• Fat builds up in the liver and eventually causes cirrhosis
• Associated with obesity, diabetes, protein malnutrition, coronary artery disease, and corticosteroid medications

Autoimmune Hepatitis

• Caused by the body’s immune system attacking liver cells and leading to inflammation, damage, and cirrhosis.
• About 70 percent of those with autoimmune hepatitis are female

Inherited Diseases

• Cystic fibrosis, hemochromatosis, Wilson disease, galactosemia, and glycogen storage diseases.
• These interfere with how the liver produces, processes, and stores enzymes, proteins, metals, and other substances the body needs to function properly.

Other Liver Disease Factors

• Drugs, toxins, and infections.
• Other causes of cirrhosis include drug reactions, prolonged exposure to toxic chemicals, parasitic infections, and repeated bouts of heart failure with liver congestion.

Wilson Disease

• Wilson Disease: a genetic disorder that prevents the body from removing excess copper
• A small amount of copper obtained from food is necessary for health, too much is poisonous
• Copper builds up in the liver, brain, eyes, and other organs
• Causes the outer iris to become coppery

Galactosemia

• Galactosemia: a hereditary disorder that prevents the body from metabolising galactose
• If a galactosemic baby is given milk, unmetabolized milk sugars builds up in the brain, liver, kidneys and eyes
• Causes brain damage, cataracts, jaundice, enlarged liver, kidney damage

Hemochromatosis

• Hemochromatosis: buildup of iron

Cystic Fibrosis

• Cystic Fibrosis: buildup of mucus in lungs

Diabetes

• Glycemic index
• Half vegetables, quarter grains, quarter meat and alternatives

Organic Molecules

• Organic Molecules: carbon bonded to hydrogen, oxygen, sulfur and nitrogen

Macromolecules

• Macromolecules: larger, more complex assemblies of organic molecules needed to provide energy, to regulate cellular activities and to build and repair tissues
• Needed for energy
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids (DNA & RNA)

Carbohydrates

• Provide materials to build cell membranes
• Provide quick energy for use by cells
• Contain carbon and water.
• Can be simple or complex.
• Monosaccharides; sacchar means sugar (glucose, fructose, galactose) C6H12O6
• Disaccharide; double sugars, always contains a glucose (sucrose, maltose, lactose) C12H22O11
• Polysaccharides; made up of glucose sub-units (starch, cellulose, glycogen, chitin, peptidoglycan)
• Glucose, fructose, lactose, maltose, starch, glycogen, cellulose
• Maltose = glucose + glucose (beer sugar or malt sugar)
• Lactose = glucose + galactose (milk sugar)
• Sucrose = glucose + fructose (table sugar)
• Sugars are carbs, lots of sugars and in ose

Fructose

• Fructose: C6H12O6
• Pentagon shape
• Carbons are counted counter-clockwise, start at top left
• Moves by facilitated diffusion down its concentration gradient from the lumen of the small intestine into the epithelial cells

Glucose

• Glucose: C6H12O6
• Found in every saccharide
• Hexagon shape
• 4th carbon has OH on the BOTTOM (1st carbon is on the very right, go clockwise)

Galactose

• Galactose: C6H12O6

• Hexagon shape

• 4th carbon has OH on the TOP

• Maltose: enzyme is maltase

• Lactose: enzyme is lactase

• Sucrose: enzyme is sucrase

Lipids

• Lipids: store energy reserves for later use by cells
• Cushion and insulate internal organs
• Used for lubrication also
• Provide materials to build cell membranes
• Insoluble in water
• Structure is a glycerol (an alcohol) consisting of 3 carbon atoms, each attached to a fatty acid chain (an acid with a long tail of carbon and hydrogen atoms)
• Store 2.25 times more energy per gram than other biological molecules
• Some functions as energy-storage molecules an phospholipids from the membrane that separates a cell from its external environment
• Fats, oils, waxes, butter, lard, steroids, triglycerides, phospholipids

Triglycerides and Fatty Acids

• fats that are made of 3 fatty acid chains linked to a glycerol.
• Triglyceride is formed from dehydration synthesis with a glycerol and 3 fatty acid chains, therefore 3 water molecules are removed
• Saturated Fat; all carbons within the fatty acid chain have only single bonds (solids)
• Unsaturated Fat; a double bond within the fatty acid chain (oils)
• Monounsaturated Fat; one double bond is present within the fatty acid chain
• Polyunsaturated Fat; more than one double bond is present within the fatty acid chain
• Trans Fat; hydrogens are on the opposite side of the double bond (manufactured via hydrogenation)

Unsaturated Fats

• As double bonds are added, the molecules kink (bend)
• These kinks make it more fluid
• This is why unsaturated fats are better for circulatory health, as saturated fats are solid which clog arteries
• Omegas are unsaturated fats

Carboxyl Groups

• Carboxyl Groups: carbon bonded to a hydroxyl (hydroxide)
• Found in fatty acids

Omega Fatty Acids

• From the methyl side, count the carbons (including the one in the methyl)
• If a double bond occurs on the 3rd carbon, it is an omega 3, and so on
• Omega 9’s can be produced in your body

Proteins

• Provide structure and support for blood cells, body tissues, and muscles
• Aide in muscle movements, such as contraction
• Act as catalysts to speed up chemical reactions in cells (enzymes)
• Provide immunity against infection and diseases (antibodies)
• Transport ions in cell membranes (protein channels)
• Insulin, hemoglobin, collagen, antibodies, enzymes
• Small subunits are known as amino acids
• Most enzymes and antibodies are proteins
• Help build and repair muscles and cell membranes

Amino Acids

• Joined by peptide bonds
• Dipeptide: two amino acids joined together
• Polypeptide: three or more amino acids joined together
• Are composed of an amino group, essential hydrogen, R side chain and carboxyl group
• The R side chain or R group is different in every amino acid

All Amino Acids

• Glycine
• Alanine
• Valine
• Leucine
• Isoleucine (muscle recover and repair)
• Methionine
• Phenylalanine (fee-knull-ala-neen)
• Tryptophan (found in turkey, makes you tired)
• Proline
• Serine
• Threonine
• Cysteine
• Tyrosine
• Asparagine
• Glutamine
• Aspartate (acidic)
• Glutamate (acidic)
• Lysine (basic)
• Arginine (basic)
• Histidine (basic)

9 Essential Amino Acids

• Valine
• Leucine
• Isoleucine
• Methionine
• Phenylalanine
• Tryptophan
• Threonine
• Lysine
• Histidine

9 EAA For Vegans

• nuts/seeds
• Grains
• Legumes (beans)

Digestive Enzymes

• Carbohydrase breaks down carbohydrates into simple sugars.
• Lipase breaks down lipids into glycerol.
• Protease breaks down proteins into amino acids.
• Nuclease breaks down nucleic acids into nucleotides.

Factors That Affect Enzyme Action

• Temperature and pH
• More energy is added at higher temperature, so the enzyme activity increases. Chemical bonds become too weak to maintain the enzyme’s shape. Enzymes become denatured, their molecular shape and structure changes. The optimal temperature range for human enzymes to work is 37 degrees.
• Denaturing proteins is caused by breaking hydrogen bonds (around 50℃)
• Different enzymes have different optimal pH environments
• Salivary amylase - 7 pH
• Pancreatic amylase - 8 pH
• Carbohydrates - 8 pH
• Pancreatic lipase - 8
• Pepsin - 1 or 2 pH
• Trypsin - 8 pH
• Chymotrypsin - 8 pH

Nucleic Acids

• Contain the organism’s genetic information
• Direct growth and development of all organisms using a chemical code
• Deoxyribonucleic acid, ribonucleic acid

Dehydration Synthesis

• Dehydration Synthesis: a chemical reaction that involves the loss of a water molecule from the reacting molecule.
• Two monosaccharides, such as glucose and fructose, can be joined together (to form sucrose) using dehydration synthesis. The new molecule, consisting of two monosaccharides, is called a disaccharide.

1-2 Glycosidic Linkage

• Results from glucose and fructose undergoing dehydration synthesis (sucrose)
• 1 and 2 are the carbon numbers, 1 from glucose and 2 from fructose

1-4 Glycosidic Linkage

• Results from galactose and glucose undergoing dehydration synthesis (lactose)
• Results from glucose and glucose undergoing dehydration synthesis (maltose)

Diabetes Mellitus

• Diabetes Mellitus: simple diabetes
• Type I; pancreas doesn’t produce enough insulin
• Type II; used to be considered “adult onset”, due to diet/lack of exericse
• Gestational; happens during pregnancy

Diabetes Insipidus

• Diabetes Insipidus: rare condition that has nothing to do with pancreas or blood sugar
• Kidneys produce 3-20 quarts of pee rather than 1-2
• Causes dehydration

Cancer

• Often does not cause any signs or symptoms in its early stages
• The pancreas lies deep in the abdomen and has no nerves
• A pancreatic tumour can grow very large without causing symptoms
• Symptoms; abdominal pain or discomfort, unexplained weight loss, bloating from eating, loss of appetite, nausea and vomiting, jaundice