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Digestive (Downstream (bile is continuously being released since gall…

- - - - Salivary amylase
        
        Pancreatic amylase
        
        Oligosaccharides & disaccharides
        
        brush border enzymes in SM intestine
        
        Lactose
        
        Galactose
        
        Maltose
        
        Glucose
        
        Sucrose
        
        Fructose
  - - - Pepsin (stomach glands in presence of HCI)
        
        Large polypeptides
        
        Pancreatic proteases
        
        SM polypeptides, Sm peptides
        
        Brush border enzymes
        
        Amino Acids
  - - - Lingual lipase
        
        Gastric lipase
        
        Emulsification by the detergent action of bile salts ducted in the liver
        
        Pancreatic lipases
        
        Monoglycerides & fatty acids
  - - - Pancreatic ribonuclease & deoxyribonuclease
        
        Brush border enzymes
        
        Pentose sugars, N-containing bases, phosphate ions
- - - - Eating
    - - Swallowing
      - Peristalsis
        
        Altering waves of contraction & relaxation
    - - Chewing
      - mixing food with saliva by the tongue
      - churning food in the stomach
      - Segmentation
        
        rhythmic local constrictions of SM intestine
        
        mixes food with digestive juices
        
        makes absorption more efficient
    - - steps that involve enzymes that break down complex food molecules
    - - passage of digested end products
      - includes vitamins, minerals, water
      - travels through lumen of GI tract into blood or lymph
    - - elimination of indigestible substances
      - via anus in from of feces
- - - - Fat-soluble vitamins (A, D, E, K)
        
        absorbed by diffusion
      - Water-soluble vitamins (C, B)
        
        absorbed by passive or active transport
      - Vitamin B12
        
        binds with intrinsic factor
        
        absorbed by endocytosis
    - - Vitamin (K, B)
        
        absorbed from bacterial metabolism
  - - - exception
      - absorbed as needed
      - Ionic iron is stored in mucosa cells with protein FERRITIN
      - transported in blood by plasma protein TRANSFERRIN when needed
    - - absorption is regulated by Vitamin D & PTH hormone
      - PTH stimulates activation of Vitamin D
      - absorbed as needed
      - exception
  - - - 95% is absorbed in SM intestine
      - rest is absorbed in LG intestine
    - - we use absorption of water to help move & absorb other molecules
- - - - Sight, smell, taste
      - Salivation
        
        Stimulates production of gastric juices
        
        gastric contractions
        
        prepare GI system for arrival of food
  - - - distension activates stretch receptors
      - long and short reflexes intiated
      - chemical stimuli activates G cells to produce Gastrin
        
        initiates HCL release from parietal cells
        
        Binding to receptors
        
        stimulates entreroendocrine cells to release histamine
  - - - intestinal gastrin release to blood
        
        brief release of intestinal gastrin secretions
        
        secretion of biocarbonate, digestive enzymes, and bile
- - - - bite and chew
      - Buccal phase- voluntary contraction of tongue
        
        mixes food with saliva which contains enzymes
        
        pushes bolus into the oropharynx
      - major functions include Ingestion, propulsion, Mechanical breakdown, Digestion
      - starts the digestion of polysaccharides
    - - Swallows food by reflex action
      - Propulsion moves it into esophagus
      - conduit to pass food from mouth to stomach
        
        Pharyngeal-Esophageal phase
        
        involuntary phase controlled by swallowing center in the stem brain
        
        food enters esophagus
        
        respiration is momentarily inhibited
    - - CONT. of Pharyngeal-Esophageal phase
        
        upper esophageal sphincter contracts after food enters
        
        peristalsis moves food through the esophagus into stomach
      - function- Propulsion
    - - Stores food
      - churns to mix food with water and digestive juices
        
        creates paste like form - CHYME
      - Rugae- stomach mucosa folds
        
        allow distension (to stretch when needed)
        
        can expand from 50ml up to 4 L
      - CONT. of Pharyngeal-Esophageal phase
        
        the gastroesophageal sphincter surrounding the cardial orifice opens
        
        sphincter closes to prevent regurgitation
      - contains 4 tunics
        
        MUSCULARIS
        
        has a 3 layer
        
        OBLIQUE layer
        
        smooth muscle allows stomach to churn, mix, move chyme
        
        breaks down into smaller fragments
        
        responsible for SEGMENTATION
        
        contains inner circular muscle layer- outer longitudinal layers
        
        Sphincters
        
        acts as valves
        
        prevent backflow
        
        MUCOSA
        
        consists of Simple columnar epithelium
        
        composed of mucous cells
        
        secrete alkaline mucus
        
        helps protect cells from acids
        
        Gastric pits
        
        lead to Gastric glands
        
        Produce gastric juice
        
        types of Gastric gland cells
        
        Parietal cells
        
        2 more items...
        
        Chief cells
        
        1 more item...
        
        Enteroendocrine cells
        
        1 more item...
        
        innermost layer- lines with the lumen
        
        functions: SECRETION, ABSORPTION, PROTECTION
        
        SUBMUCOSA
        
        consists of areolar connective tissue
        
        contains blood & lymphatic vessels
        
        abundant elastic tissues that help regain shape after storing large meal
        
        SEROSA
        
        outermost layer
        
        dense connective tissue
      - major functions include Mechanical breakdown, propulsion, digestion, & absorption
    - - receives secretions from the accessory organs
      - site of most digestion and absorption of nutrients that go into circulation.
        
        length provides huge surface area for nutrient absorption
        
        Circular folds
        
        permanent folds force chyme to spiral slowly
        
        allows for more time to absorb nutrients
        
        Villi
        
        fingerlike projections of mucosa
        
        core contains dense capillary bed & lymphatic capillary called LACTEAL
        
        Microvilli
        
        also called brush border
        
        contains membrane-bound enzymes (brush border enzymes)
        
        used for final digestion of proteins, carbohydrates, & nucleic acids
        
        Intestinal crypts
        
        types of cells
        
        Enterocytes
        
        In VILLI-absorb nutrients & electrolytes
        
        In Crypts- produce intestinal juice
        
        Goblet cells
        
        mucus secreting cells
        
        Enteroendocrine cells
        
        source of enterogastrones
        
        Paneth cells
        
        secrete antimicrobial agens
      - 3 subdivisions
        
        Duodenum
        
        duodenal glands secrete alkaline mucus
        
        neutralize acidic chyme
        
        Jejunum
        
        Ileum
      - major functions include Mechanical break down, Propulsion, digestion, & absorption
    - - Forms, stores and eliminates undigested waste material
      - unique features only found in the LG intestine
        
        Teniae coli
        
        Haustra
        
        beneficial bacteria outnumber and suppress pathogenic bacteria
      - contains simple columnar epithelium
      - deep crypts with mucus-producing goblet cells
      - Metabolic functions
        
        Fermentation of some indigestible carbohydrates and mucin
        
        Vitamin synthesis- synthesize B & some Vitamin K needed by liver to produce clotting factors
      - Major functions include digestion & absorption
    - - eliminates feces from the body
      - 2 sphincters
        
        Internal (smooth muscle)
        
        External (skeletal muscle)
      - major functions include Propulsion & Defecation
  - - - gripping and repositioning food
      - mixing food with saliva
        
        forming a BOLUS
      - Initiation of swallowing
      - composed of interlacing bundles of skeletal muscle & Stratified squamous epithelium
      - slightly kerotinized
      - Intrinsic muscle helps change shape
      - Extrinsic muscle helps with the movement
    - - Mastication- process of chewing
      - Grinds and tears food into smaller fragments
      - teeth are classified according to shape
        
        Incisors
        
        chisel shaped for cutting
        
        Canines
        
        fanglike teeth that tear or pierce
        
        Premolars (bicuspids)
        
        broad crowns used to grind or crush
        
        Molars
        
        best grinders
    - - Stores and releases bile needed for lipid digestion
    - - release mixture of water, mucus and enzymes
      - cleanses the mouth
      - begins break down of starch with enzyme amylase
        
        contains salivary amylase- break down of carbohydrates
      - Minor (intrinsic) glands
        
        scattered throughout the oral cavity
        
        keeps mouth moist all day
      - Major (extrinsic) glands
        
        located outside of oral cavity
        
        composed of 2 types of secretory cells
        
        Serous cells
        
        watery secretion, enzymes, ions, & mucin
        
        Mucous cells
        
        mucus
        
        lubricates oral cavity
        
        hydrates foodstuff
      - Saliva 97-99% water
    - - produces bile- alkaline solution
        
        contains
        
        bile salts- cholesterol derivatives
        
        function in fat emulsification & absorption
        
        bilirubin- pigment formed from heme
        
        broken down by bacteria to form Stercobilin
        
        gives feces brown color
        
        cholesterol, triglycerides, phospholipids, and electrolytes
      - Enterohepatic circulation- recycling mechanism
        
        conserves bile salts
        
        reabsorbs into blood
        
        returned to liver via hepatic portal blood
    - - Releases pancreatic juice that neutralizes chyme
      - composition of pancreatic juice
        
        electrolytes, digestive enzymes
        
        Proteases- for proteins
        
        Amylase- for carbohydrates
        
        Lipases- for lipids
        
        Nucleases- for nucleic acids
      - both bile and pancreatic secretions are stimulated by neural and hormonal controls
        
        hormonal
        
        Cholecystokiin (CCK)
        
        duodenal mucosa cell's response to fatty chyme
        
        Secretin
        
        duodenal mucosa cell's response to acidic chyme
      - Bile is released to SM intestine only with contraction