GI Flashcards
GI tract contains two things?
- Continuous hollow tube- 8m long.
- Acessory organs: teeth tongue salivary glands etc.
What does the continuous hollow tube do?
- Mechanical process and moves food thrkifh tract.
- Chemical process and digests food.
- Absorbs nutrients and water.
What do the accessory organs do?
Control secretions and breakdown food.
Neural control mechanism? ANS.
Autonomic nervous system.
Parasympathetic and sympathetic.
- Extrinsic nerves, long reflexes and external stimuli.
Involves CNS.
Causes changes in motility and secretion.
Parassymthetic nerves do what to digestion?
Stimulate digestion.
Sympathetic nerves?
Inhibit digestion.
Enteric nervous system?
- All elements of nervous system.
- Intrinsic control, short reflex and internal stimuli.
- Communicates with para and sympathetic but autonomous.
Enteric nervous system- 2 organised neural plexuses.
- Myentric.
- Submicosal.
What is a plexus?
Branching network of vessels and nerves.
Myenteric plexus (Auerbachs)?
Between longitudinal and circular layers of muscle in control of digestive tract motility.
Submucosal (Meissners)
Between circular and luminal mucosa.
Senses environment of lumen and regulates gi blood flow and epithelial cell function.
Criteria to meet as a GI hormone?
- Substance must be secreted in response to physiologic stimulus.
- Function must be independent of any neural activity.
- Must have been isolated purified.
Gastrin?
Found in stomach.
Secreted by G cells.
Stimulates HCL production (stimulated pepsinogen in stomach) stimulates gastric contraction.
Secretin?
Found in small intestine.
Produced by S cells.
Stimulates water and bicarbonate secretion in pancreatic juice.
Gastric inhibitory peptide (GIP)?
Found in small intestine.
Produced by K cells.
Somatostatin?
Founded in small intestine stomach and pancreas.
Produced by D cells.
Motilin ?
Found in Small intestine.
Produced by M cells.
Cholecystokinin? CCK,
Small intestine.
Produced by I cells.
Enteroendocrine cells (EEC)?
- Single cells scattered through GI tract.
- Densley packed secretory vesicles.
- Sness chemical osmotic and ph.
Release hormones and oaracrines.
Motility= 2 types?
Phasic contractions.
Tomic contractions.
Phasic contractions?
Short lasting contractions.
Movement of material in small intestine.
- Peristalsis: Waves of contractions 20cm.
- Segmented contractions: 10cm.
Tonic contractions?
Long lasting contractions.
Closing of sphincter.
- Controlled movement of material through tract.
- Maintains ordered sequence of events.
- Compartmentlaisation ensures processes are complete before moving on to next area.
Peristalsis?
Mediated by neurones in myentric plexus.
ICC stands for?
Interstitial cells of cajal.
Like pacemakers of gut.
Found in myenteric plexus.
- Electrical activity spread through gap junctions from ICC to muscle.
Produce slow waves.
Differs in regions of GI tract.
Slow waves?
Don’t cause contraction until threshold -40 reached.
Activated by:
- Distension- bolus of food stimulates stretch receptors local reflex. Oral contraction and aboral relaxation.
- Parasympathetic nerves. (Acetylcholine).
The colon 99% of the time?
Retains material like water and fermentation.
Mixing contents.
Mass movement of material into aboral end of colon?
Gastro colic response.
2-3 times a day.
Hirschprungs disease- toxic mega colon?
Surgical removal of colon.
All or part of colon has no innervation.
Presents shortly after birth.
Can’t move stool, is blocked. (Without enteric nerve cells stimulating gut).
To start journey with mouth?
- Mastication: Breakdown food.
- Taste: Inform brain about edibility and duration.
- Saliva production: Lunrication, protection and digestion.
- Swallowing: Moveemnt of digested macromolecules to stomach.
Taste?
Papillae (taste organs).
Located on tongue- soft hard palate palate epiglottis and larynx.
- Contains taste buds.
Each taste bud has 3 kinds of cells?
- Epithelial cells.
- Support cells.
- Gustatory receptor cells (taste cells).
Unnerved by gustatory affront nerves.
All flavours encoded by 5 taste modalities?
- Sweet, sour, salt, bitter , umami(savor).
One taste cells responds to one modality .
Salt- H+.
Sour- K+.
Metabotropic: Sweet bitter umami.
Saliva function?
- Hypotonic solution contains more 99% water and 1% dry matter such as proteins.
- alpha amylase- from parotid gland initiates carb digestion.
- lipase- secreted within glands of mucosa of tongue (lingual).
Multi functional:
Anti bacterial fungal viral etc.
Swallowing? Phases?
- Oral phase (voluntary).
- Pharyngeal phase (involuntary).
- Oesophageal phase.
Oral phase?
- Prep phase: chew and bite.
- Transfer phase: respiration inhibited and tongue forces bolus(mix of saliva and food) into pharynx.
Pharyngeal phase?
Movement of bolus from pharynx into oesophagus.
Oesophageal phase?
Delivers bolus to stomach.
Espohagal manometer?
Measures oesophageal motility and problems swallowing (dysphagia).
Stomach functions?
- Motility
Gastric accommodation
Trituration (gastric juices)
Gastric emptying. - Digestion.
- Protection.
- Absorption.
Gastric juice made of?
- Water and ions.
- HCL- low ph catalyse pepsiongwn to pepsin.
- Pepsinogens - pro enzyme of pepsin.
- Intrinsic factor. Glycoprotein binds to b12 allllwing digestion in ileum.
- Mucus. Protects gastric mucosa.
- Gastrin- regulates acid secretion.
Parietal chief and endocrine cells?
Parietal- HCl and intrinsic factor.
Chief- Pepsinogen.
Endocrine- G cells (Gastrin stimulate acid secretion).
And D cells (somatostatin to inhibit acid secretion).
HCL secretion?
CO2 in parietal cells reacts with oxygen to form bicarbonate then hydrogen ions catalysed by enzyme carbonic anhydrase.
Acid secretion?
- Neuroendocrine (acetylcholine).
- Endocrine (Gastrin).
- Paracrine (Histamine).
Motility phases?
Cepahlic- 30%
Gastric- 60%
Intestinal- 10%
Gasteic/ peptic ulcers?
Mucus entraps alkali.
Break in mucosal barrier.
Bacteria- Helicobacyer pylori.
Symptoms- abdominal pain, bloating, vomitjng bleeding.
Cause of peptic ulcer?
- Excess section of acid and pepsin by gastric mucosa.
- No ability of gastroduodenal to protect against properties of stomach acid pepsin section.
Duodenum?
First loop of small intestine (25-40cm).
Brunner gland- Secrete alkaline fluid.
Received secretions from gall bladder (liver) and pancreas.
Site of metal ion absorption.
Acinus is?
Exocrine gland.
Endocrine glands?
Islets of langerhans?
Alpha- Glucagon.
Beta- Insukin.
In the duodenum?
Secretion of pancreatic juice under hormonal control.
CCK acts as acinar cells causes production of pancreatic juice.
Secretin acts on ducts to cause secretion of alkaline.
Ensure juice is washed to intestine.
Liver structure?
- Hepatic artery: Oxygenated blood.
- Helatic vein: Deoxygenated blood from liver.
- Bile: Produced by liver stored in gall bladder. (Biliary system).
- Portal vein- Nutrint rich blood from liver.
Why do we need to eat?
- Maintenance of body: repair, growth, function.
There is a need to supply nutrients that cannot be made by the body.
Essential nutrients that need to be part of the diet?
Carbs.
Amino acids (proteins).
Fatty acids.
Vitamins.
Minerals and water.
Imbalances may result in?
Disease and deficiency disorders.
Macro nutrients?
Essential for survival and growth.
- Carbs.
- Proteins.
- Fats.
- Water.
Micro nutrients?
Essential for growth and enhance function and usability of macro nutrients.
- Vitamins.
- Minerals.
Around 50% of the diet should be from?
Carbs.
35% should be from?
Fats.
About 15% from?
Proteins.
If our diet has a combination of macronutrients, what does our body do?
Metabolism.
- This is chemical reaction in body’s cells that changes food to energy.
- Anabolic or catabolic.