Mind map

Gastrointestinal and digestion

Caroline Oxford Physiology bacalaureat English

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GI Tract
- Digest
  - Absorb
    - Metabolism
      - Excretion
        Secretion
Liver
- 1.Processing of nutrients
  - Lipid break down
    - Triglycerides + cholestorel
    - Lypoproteins
- Carb breakdown, glycogenisis
  - Eat, high levels of insulin (From pancreas) Low levels of Glucagon
- Stores Glycogen
  - Turns to glucose
- Protein breakdown
  - Gut breaks down protein to Amino acids
    - Liver puts them back to either functional proteins or pre-hormone proteins
- 2. Synthetic function of liver
  - Albumin
  - Coagulation Factors
    - Fibrinogen
      - Vit K dependent factors 7, 9 + 10 and prothrombin
  - Transport and binding proteins
    - eg Transferrin for Iron
  - Immunologic proteins
    - Complement proteins CD4 etc
  - Bile Salts
- Stores Vitamins/minerals
- 3. Protection and clearence
  - Portal Vein collects crap from Intestine/colon
  - Protection from Bacteria
  - Sinusoids, lined with Kuppfer cells(macrophages)
  - Breakdown of toxins
    - By oxidisation or cleaving proteins
    - Breaksdown Amino acids into Urea
  - Produces anti-oxidants to stop too much breakdown by oxidisation
Pancreas
- Drains into Dueodenum
  - Secretes Bicarb to increase pH
    - Produces pancreatic enzymes
- Pancreas
  - Drains via the pancreatic duct into Duodenum
    - Acini Cells, secrete pancreatic juices
      - Islet of Langerhan cells
        Endocrine part
      - Contains Zymogin granules
      - Contains Bicarb, higher than plasma (150)
        pH 8.4
        Which increase pH in duodenum from the high pH of stomach (7.4)
      - Acini cells contain Lipase (breaks lipids), Amalyse (Cleves starch), Pro-Proprotease(inacctive protein breaking enzyme)
      - Makes Tripsinogen
        Acctivated by brush boarder enzymes in duodenum
        Turns into Tripsin
        Turns Pro-Proprotease into Protease
        Only happens in Duodenum
Mouth
- Oesophagus
  - Stomach
    - Dueodenum
      - Jejunum
        Illium
        Colon
Gallbladder
- Produces bile acids
  - Secretes bile salts into Dueodenum to break down fat
    - Drains via the common bile duct, with the pancreatic duct
Peristalsis
- Cajal Cells (pacemaker cells of the gut)
  - Produce action potentials
    - Causes muscle cells to move
    - Baseline Rhythm
- Myenteric plexus
  - Afferent sensory nerves
    - Above muscle layer
      - decending efferent nerves, stimulate spike wave/ action potential
        Stimulated by
        Reflexive (stretch/chemo recptors) Enteric system
        Parasympathetic system Acetycholin
        Inhibited by sympathetic system
        Epinephrin/norepinephrin
        Fight or flight
    - Stretch receptors + chemoreceptors
  - Enteric nervous system Gut's own nerves
    - doesn't go to spinal cord
Bilirubin Pathway
- RBC breakdown
  - Macrophage 'eats RBC
    - Globin
      - Gets recycled
    - Haem
      - Iron gets reused to make RBC
        Leaves a Porphryin Ring
        Ring gets broken into chain, (Bilirubin)
        Bright yellow
        Toxic, can't break down easily in water
        Attaches to Albumin molecule
        Goes to Liver
        Glucoroltransferase
        Makes Bilirubin more water soluble
        Turns into conrgigated billirubin
        Drains into intestine
        Through oxidation, turns to Steribolinogen
        Gets excreted
        Urobilinogen gets back in blood
        Filtered in kidneys
        Oxidises to Urobilin
        Colour of Urine
Breakdown of Fats
- Begins in the stomach
  - Catalised by Lipase
    - Lingual and Gastro Lipases
      - Gastro- Stomach epitelial cell secretion
        Cholecystokinin, secreted in Duodenum (small intestine) By endocrine cells
        Cholecystokinin Release pancreatic enzymes
        Cholecystokinin also releases bile salts from gall bladder
        Stops stomach mortility, to give time for fatty acid digestion
        Secretin, release Bicard into duodenum to raise pH
        By contrating the gall bladder and squeezing it out
- Triacylgycerol
  - Colesterol
    - Free fatty acids
      - Short and Medium chained fatty acids
  - Breaks down into
- Emulsification
  - Bile salts make fat partly water soluble
    - Breaks down into 2 fatty acids +monoglycerides, vit A or K etc
      - 80% of bile salts recycled back to liver
      - Micelles
- no breakdown will result in no absorbtion of fat, calcium, vit D, K etc
  - Can happen from pancreas probs-no lipase, no bicarb to change pH. From liver- no bile salts (from hepatocytes)
Absorbtion
- Bicarb in the Jigunum
- Iron in the duodenum
- Illlium
  - B12 absorbtion+ bile salts
- Colon excretes no digestion
  - K+, excreted
  - Sodium/water uptake
    - Aldosterone helps this (lower blood preesure trigger)
  - Enter text here
Acid secretion
- Phase 1
  - Sight, smell, thought
    - Cerebral cortex
      - Stimulates a condition responce
        In Hypothalamus, the Medula Obongata
        Stimulates Vagus
        Which stimulate Acetycholine
        Parasympathetic
  - Cephalic phase
- Phase 2, gastric
  - Physical stretching of Bolus
    - stimulate vasovagus, which stimulates Medula Obongata
    - Local reflex
      - Stimulates Acetycholin
  - Chemical receptors
    - H+ buffers released from food, carbs etc, increase pH
      - Activate G cells
        Secrete Gastria
      - Inhibits D cells
        Secrete Somatistat
        Higher than pH2 will activate
- Phase 3, intestinal
  - Gastrin secretion from epithelial mucosa
    - secretes Interagastrin
      - Histamine is also produced
      - All act on PARIETAL Cells to produce acid

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Description: bacalaureat Physiology Mind Map on Gastrointestinal and digestion, created by Caroline Oxford on 29/05/2013.
Created by: Caroline Oxford
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Tags: physiology
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Gastrointestinal and digestion

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