D2 Digestion Flashcards
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Secretion of Digestive Juices
Gastric pits <3
LAYER FROM TOP TO BOTTOM OF PIT:
Goblet cells - Mucous (protective)
Parietal cells - Gastric acid (juice)
Chief cells - Pepsinogen (breaks down proteins)
D cells - Somatostatin (inhibits acid secretion)
G cells - Gastrin (promotes acid secretion)
Alimentary Canal
Canal that directly transfers food in the body
Endocrine vs Exocrine glands
Exocrine:
- Sweat, Oil, Wax, Enzymes into DUCTS
Endocrine:
- Hormones directly into BLOODSTREAM
Hormonal and Nervous systems that control secretion of digestive juices.
Brain & Stomach signals.
The vagus nerve connects the brain to the stomach
1) Smell & taste receptors (mouth, tongue, and throat) + chewing (mechanical motion) => signals to body “INCOMING FOOD”.
2) Stomach gets big (stretch reflex) stimulates the medulla oblongata.
3) The medulla then signals stomach to release hormone gastrin.
5) Gastrin tells parietal cells to release its juices.
6) The muscular walls of the stomach contract vigorously to mix food with gastric juice, producing a mixture called chyme.
7) When the stomach is full it sends a message to the brain asking it what to do with the food, and it receives more information from the medulla.
Three exocrine glands associated with the alimentary canal.
1) Salivatory Glands
2) Parietal cells in gastric pits
3) Pancreatic duct cells.
Composition of saliva, gastric juice and pancreatic juice.
Saliva => water, mucus, proteins, mineral salts, and amylase.
Gastric Juice => water, HCl, electrolytes and and organic substances (mucus, pepsins, and protein).
Pancreatic Juice => Bicarbonate, lipase, amylase, trypsin
Outline three roles of acid in the stomach.
1) Optimal pH for enzymes (Activates pepsinogen into pepsin)
2) Denatures proteins for digestion
3) Kills pathogens in food
Epithelium of the Villi Structure
Microvilli (surface area)
Tight Junctions (prevents cell food transfer)
Invaginations (increase surface area)
Pinocytic vesicles (bring small particles in MAKE INVAGINATIONs)
Proteins on apical and basal surface (active and facilitated transport)
Benefit of Fibre
Made from cellulose (indigestible)
Provides bulk to food, because it’s undigested
Helps the food move
Helps the person feel full to prevent overweightness
Colour due to bile
Smell due to bacteria
Dietary fibre
Dietary fibre is found in wholegrain cereals and fruit and vegetables
Role of mucuous in stomach
1) Lubrication of food masses in to facilitate movement.
2) Formation of a protective layer over the lining epithelium of the stomach cavity.
if not present then ulcer and acid reflux
Proton Pump Inhibitors
The production of the acidic environment within the stomach is achieved by a proton pump called the H+, K+-ATPase.
Prescribed for gastric diseases.
PPIs bind irreversibly to a single pump. blocks secretion of protons in lumen for HCl
The effect on the overall acid production system is not permanent as the pumps are normally recycled and replaced with new pumps.
The PPIs are consumed in an inactive form. Acid conditions in the vicinity of the parietal cells convert them to the active form
List benefits of fibre in a healthy diet
- slow down the rate of digestion
- helps contraction of intestinal muscles
- improves LDL cholesterol levels
- adds bulk to feces, passes through the colon more easily, preventing constipation
Cholera
Cholera bacterium
Infect intestine, severe dehydration
Toxin binds to surface receptors on mucosal cells of the intestine.
Chlorine ions are pumped out into gut followed by secretion of water, sodium ions, potassium ions, hydrogencarbonate ions into the intestine
The cells lose a lot of water, which causes severe dehydration, and the increased water in the small intestine causes watery diarrhoea and vomiting
Stomach ulcer cause
Helicobacter pylori infection eats up mucous lining
