Biology (Christian) Respiration

• Gut microorganisms


  • Vast majority of the body's microorganisms live in the gut
  • Species vary among individuals and populations
• Helicobacter pylori


  • Resides in more than half the worldwide population
  • 5 to 20 percent of infected people develop peptic ulcers
  • Infection also increases the risk of stomach cancer sixfold
  • Infected people less likely to have GERD
• Irritable bowel syndrome (IBS)


  Caused by shift in diversity and proportions of intestinal bacteria
• Probiotic


  • Food or supplement containing beneficial living organisms
  • Example: Bifidobacterium
• Four tasks of processing food

  • Ingestion
  • Mechanical and chemical digestion
  • Absorption
  • Elimination
• Saclike gastrovascular cavity


  • Functions for both digestion and gas exchange
  • Found in flatworms and cnidarians

  
• Complete digestive tract


  • Tubular gut with two openings
  • Food travels through regions specialized for food storage, food breakdown, nutrient absorption, and waste elimination

  
• Esophagus

  Tube with enlarged part called the crop stores food
• Stomach


  • Muscular digestive organ
  • Chemically and mechanically breaks down food
• Gizzard


  • Grinds up food
  • Present in earthworms, birds, and other animals lacking teeth
• Multiple-chambered stomach


  1. Ingestion, regurgitation, reswallowing of food through esophagus

  2. To small intestine

  
• Intestine


  • Place where most chemical digestion happens
  • Nutrients are absorbed from the intestine

  
• Carnivores vs Herbivores

  • Carnivores have a shorter intestine than herbivores
  • Meat is easier to digest than plant material
• Cloaca


  Some animals have a multipurpose opening for waste
• Digestive tract


  • Also known as alimentary canal
  • Features coiling and folding to allow lengthy tube to fit
  • Lined with mucus-secreting epithelium

  
• Accessory digestive organs

  • Salivary glands
  • Liver
  • Pancreas

  
• Peristalsis


  • Process by which food moves through the esophagus and digestive tract
  • Smooth muscles contract and relax in rhythmic waves

  
• Sphincters


  • Rings of muscle that can relax to open or contract to close
  • Control flow of substances through a passage
• Humans


  • Omnivores
  • Eat both meat and plant material
  • Have all four kinds of mammalian teeth

  
• Tooth types


  • Incisors
  • Canine
  • Premolars
  • Molars

  
• Teeth


  Consist of dentin, a bonelike material
• Tongue


  Skeletal muscle covered by a membrane
• Salivary glands


  • Open into the mouth
  • Enzyme in saliva begins process of chemical digestion by breaking starch into disaccharides
• Swallowing reflex


  Triggered by the presence of food at back of throat
• Empty stomach


  • Inner surface is highly folded
  • Folds smooth out as it fills with food
• Adult stomach


  Can expand to hold as much as one liter of fluid
• Mucosa


  • Lines the stomach's inner wall
  • Secretes gastric fluid into the stomach
• Gastric fluid


  Mixture of mucus, hydrochloric acid, and pepsinogen
• Stomach functions


  1. Stomach wall rhythmically contracts about three times a minute

  2. Gastric fluid mixes with food to form chyme

  3. Chyme's acidity denatures proteins

  4. Further broken down by pepsin, converted from pepsinogen

  
• Gastrin


  Hormone secreted upon arrival of food in the stomach
• Ghrelin


  • Hormone secreted when stomach is empty
  • Stimulates the appetite
• Gastric bypass surgery


  • Reduces the size of the stomach
  • Removes Ghrelin-secreting cells
• Duodenum


  First portion of the small intestine
• Small intestine


  • Small in diameter (about one inch)
  • Would stretch to five to seven meters uncoiled
  • Villi cover the surface of each intestinal fold
  • Epithelial cells at the surface of a villus have microvilli (also called brush border cells)
• Digestion and absorption in the small intestine

  1. Small intestine's lumen receives chyme from the stomach, enzymes and bicarbonate from the pancreas, and bile from the gallbladder

  2. Carbohydrate digestion and absorption: Pancreatic amylase and enzymes on brush border cells split disaccharides into monosaccharides which move into brush border cells, then into the interstitial fluid, and finally into the blood

  3. Protein digestion and absorption: Pepsin breaks proteins into polypeptides, pancreatic proteases cut the polypeptides into smaller fragments, brush border cell enzymes break them into smaller peptides and then into amino acids which are transported into brush border cells, then into interstitial fluid and into the blood

  4. Fat digestion and absorption: Bile aids in fat digestion by dispersing fat droplets, small droplets can then be broken down by lipases

  
• 80 percent of water is absorbed in the small intestine
• Large intestine


  • Wider and shorter than the small intestine
  • Only about five feet long
  • Waste materials travel from small intestine to the large intestine
  • Wastes concentrated by pumping sodium ions across the wall of the large intestine, with water following the gradient
• Feces


  Compacted digested waste
• Appendicitis


  Infection in the appendix, requires prompt surgical treatment to avoid appendix bursting and dispersing bacteria into the abdominal cavity
• Macronutrients


  • Carbohydrates, fats, and proteins
  • Body needs in large quantities
  • Function as energy sources and raw materials