DIGEST PPT NI MAAM

• Nutrition


  Any substance required for the growth and maintenance of an organism

  
• Types of organisms based on mode of nutrition


  • Autotrophs - organisms that obtain energy from sunlight & chemicals to produce their own food
  • Heterotrophs - organisms that cannot make their own food & obtain their energy from other organisms
• Autotrophs


  • plants, chemosynthetic bacteria
• Heterotrophs


  • fungi, animals
• Plant nutritional requirements


  • water
  • carbon dioxide
  • essential macro & micronutrients/elements

  
• Plant specialized absorptive structures


  • root hairs
  • root nodules (where N-fixing bacteria thrive)
  • mycorrhizae (a symbiotic interaction between a young root & a fungus)

  
• Plant nutritional adaptations


  • symbiosis of plants & soil microbes
  • symbiosis of plants & fungi
  • parasitism
  • predation

  
• Animal nutritional requirements


  • carbohydrates
  • proteins
  • fats
  • essential nutrients (amino acids, fatty acids, vitamins, trace elements)
• Types of animal feeding mechanisms


  • substrate-feeders
  • filter feeders
  • fluid feeders
  • bulk-feeders

  
• Types of animal digestive compartments


  • food vacuoles
  • incomplete digestive tract
  • complete digestive tract

  
• Digestion


  1. ingestion

  2. peristalsis

  3. digestion

  4. absorption

  5. defecation

  
• Mechanical digestion


  Ingested food is physically broken down into smaller pieces by chewing or mastication and peristalsis
• Chemical digestion


  Food is acted upon by catalytic enzymes to be broken down into its absorbable forms
• Parts of the digestive system


  • Digestive tract - mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus
  • Accessory organs - teeth, tongue, salivary glands, liver, gall bladder, pancreas

  
• Oral/Buccal cavity or mouth


  • Taste
  • Mechanical breakdown of food
  • Chemical digestion of carbohydrates by ptyalin or salivary amylase in saliva secreted by 3 pairs of salivary glands
• Teeth


  • For mechanical digestion thru biting, grinding, cutting, chewing
• Tongue and salivary glands

  • Functions of tongue - food manipulation, taste, speech
  • 3 pairs of salivary glands - Parotid, Sublingual, Submandibular
  • Saliva (99.5% H2O) lubricates food and begins digestion
• Pharynx


  • Common passageway for food and air
  • Where swallowing begins
• Esophagus


  • 25 cm or 10 in long
  • Secrete mucus
  • Transport food thru peristalsis - smooth muscle contractions propel food thru a sphincter (Upper Esophageal Sphincter & Lower Esophageal Sphincter)

  
• Stomach


  • Mixes & stores ingested food with HCl into chyme
  • Chemical and mechanical breakdown of food
  • Secretes hydrochloric acid & digestive juices that break down proteins and fats and may kill bacteria
  • Peristalsis
• Small intestines


  • Where most enzymatic hydrolysis of macromolecules from food occurs and absorption of digested food by its villi
  • Duodenum - 25cm/10in; complete digestion of food by enzymes
  • Jejunum - 8 ft; absorb H2O & products of digestion into bloodstream
  • Ileum - 12 ft; absorption of end products, with villi & mirovilli

  
• Large intestines/colon


  • Concentrates & stores undigested matter by absorbing Na, Vit K & water
  • Doesn't have villi nor coils
  • Many bacteria live, thrive & process undigested material into feces
  • Cecum – pouch-like area
  • Colon - ascending, transverse, descending, sigmoid; w/ haustrae = pouches

  
• Rectum and anus


  • Rectum – short extension of the large intestine, final segment of the digestive tract where compacted undigested food from the colon are pushed via peristalsis
  • Anus – terminal opening of the digestive system thru which feces are expelled, controlled by internal and external sphincters

  
• Pancreas


  • Acini – secrete digestive enzymes that break down all major food molecules
  • Islets of Langerhans or pancreatic islets – secrete insulin and glucagon that control glucose metabolism
• Liver and gall bladder


  • Liver produces bile salts that emulsify fats and bile is stored in the gall bladder
• Anatomy of the liver


  • 4 lobes: right, left, quadrate, caudate
  • Hepatocyte – basic structural component
  • Hepatic vein – for blood circulation
  • Portal vein – carries nutrients, chemicals, drugs, etc in the blood absorbed by the intestines into the liver
• Functions of the liver


  • Neutralizes & eliminates toxins in the blood thru portal vein
  • Stores vitamins, iron and glucose
  • Synthesizes proteins like albumin & fibrinogen
  • Converts highly toxic ammonia (accumulates from breakdown of proteins) into urea
  • Produces bile that contains cholesterol, bile acids, bilirubin which aids in lipid digestion which is stored in the gallbladder
• Anatomy of the gallbladder


  • Hepatobiliary tree: Canaliculi from Liver form bile ducts or intrahepatic ducts drain to R & L hepatic ducts merge to form common hepatic duct. Gallbladder's cystic duct & CHD form common bile duct. CBD & pancreatic duct/duct of wirsung form ampulla of vater that drains into duodenum
• Pancreas


  • Endocrine; Islets of Langerhans secrete insulin & glucagon
  • Exocrine: acinar glands secrete digestive enzymes like trypsinogen, chymotrypsinogen, carboxypeptidase into duodenum by the pancretic duct and ampulla of vater