Upper GI Tract Flashcards
What is digestion?
Breaking down of macromolecules to allow for absorption.
What is absorption?
Process of moving nutrients and water across a membrane.
What are the 3 salivary glands?
Parotid, sublingual and submandibular.
What are the 4 layers of the gut wall?
Mucosa, submucosa, muscularis and serosa.
What does the mucosa layer of the gut wall contain?
Epithelium, lamina propria (connective tissue) and muscularis mucosae (muscle).
What does the submucosa layer of the gut wall contain?
Connective tissue.
What does the muscularis layer of the gut wall contain?
Smooth muscle.
What does the serosa layer of the gut wall contain?
Connective tissue.
How many teeth do you have in total?
32 teeth.
How many of each type of teeth do you have?
8 incisors, 4 canines, 8 premolars and 12 molars.
What enzyme digests lipids in the mouth?
Lingual lipase.
What enzyme digests carbohydrates in the mouth?
Salivary amylase.
What are the intrinsic muscles in the tongue responsible for?
Fine motor control.
What are the extrinsic muscles in the tongue responsible for?
Gross movement of tongue.
At what vertebrae does the oesophagus start and end?
C5 to T10.
Where is the oesophagus constricted?
Cricoid cartilage (C6), Aortic arch (T4), left main bronchus (T5), and Oesophageal hiatus (T10).
Function of oesophagus?
To transport food, drink and swallowed secretions from pharynx to stomach.
Structure of oesophagus?
Non keratinising stratified squamous epithelium.
What is peristalsis?
Peristalsis is the alternate contraction and relaxation of smooth muscles in the GI tracts in a wave-like manner to propel food in a direction
Describe swallowing
Pharyngeal musculature guide bolus towards oesophagus. Both oesophageal sphincters open. Upper sphincter closes. Superior circular muscles contract and inferior rings dilate. Sequential contractions of longitudinal muscle moves food. Lower sphincter closes as food moves through.
How is the gastro oesophageal junction adapted to prevent acid reflux?
Angle of his. Movement of diaphragm.
What is the epithelial transition from oesophagus to stomach?
Stratified squamous to simple columnar.
Where does epithelial transition occur in the upper GI tract?
Gastro-oesophageal junction.
Function of gastric folds
These ridges allow the stomach to expand as it fills.
Functions of the stomach?
Breaks food down. Holds food, releasing it in a controlled steady rate into duodenum. Kills parasites and certain bacteria.
What does the cardia and pyloric region of the stomach contain?
Mucus only.
What does the body and fundus of the stomach contain?
Mucus, HCL and pepsinogen.
What does the antrum of the stomach contain?
Gastrin.
What layer of the stomach wall are tubular glands present in the stomach?
Mucosa.
What in mucus makes it protective towards acid?
Bicarbonate ions.
Peristalsis vs segmentation?
Peristalsis is faster and more powerful.
What nervous system is responsible for peristalsis?
Autonomic nervous system.
What nervous system is responsible for segmentation? What activates it?
Stretching of muscle activates enteric nervous system.
What type of stomach contractions are mostly done?
Segmentation.
What is a gastric chief cell?
Protein secreting epithelial cell.
How is a gastric chief cell adapted?
Contains RER, Golgi apparatus and apical secretion granules.
Example of a protein secreted by gastric chief cells?
Pepsinogen.
Parietal cell function?
Secretion of acid and intrinsic factor (Vitamin B12).
How are parietal cells adapted?
Contain lots of mitochondria as they require lots of ATP. Intercanaliculi that increases surface area for secretion.
What do the cytoplasmic tubulovesicles in the parietal cells contain? What do they do?
H+/K+ATPase. Fuse with canaliculi.
What does carbonic anhydrase in parietal cells do?
Catalyse reaction to produce carbonic acid, bicarbonate and H+ ions.
How do parietal cells secrete acid.
Bicarbonate ions pumped out into interstitial fluid and chloride ions pumped into parietal cells from interstitial fluid. Sodium pumped out into interstitial fluid and potassium from interstitial fluid pumped in to parietal cell. H+ and chloride pumped into gastric lumen.
What is the alkaline tide?
Efflux of bicarbonate into the blood after acid secretion can be detected and is known as the alkaline tide.
Why would you give someone who is vomiting potassium chloride?
Producing lots of stomach acid and so losing lots of potassium and chloride.
What does potassium do in parietal cells?
Activates H+/K+ ATPase
What does HCL do to pepsinogen?
Converts it to pepsin. Activates autocatalysis (production of pepsin catalyses pepsinogen to pepsin).
How does gastrin released from pyloric antrum G cells reach parietal cells?
Systemic circulation.
What stimulates release of gastrin?
Vagus nerve (cephalic phase), Stretch distention activate stretch receptors, food molecules activate chemoreceptors.
What does gastrin act on?
Receptors on parietal cell and Enterochromaffin-like cells.
What does gastrin do when it binds to receptors on Enterochromaffin-like cells?
Stimulate histamine release.
Function of gastrin?
Gastric motility, and secretion of hydrochloric acid (HCl) into the stomach.
What receptor on parietal cells does histamine released from Enterochromaffin-like cells act on?
H2 receptor.
What are the 3 molecules that bind to parietal cells and stimulate acid release? What are the corresponding receptors?
Acetylcholine, histamine and gastrin.
M3, H2 and G receptors.
What are highly effective drugs that reduce acid secretion?
Parietal cell proton pump inhibitors.
How does acid release from parietal cells act on a negative feedback system?
Inhbits gastrin release to prevent further acid release.
What does distention of duodenum do?
Triggers enterogastric reflex which results in inhibition of gastric motility and reduced rate of emptying of the stomach.
What hormones are released when distention of duodenum and presence of fatty acidic food enters the duodenum?
Secretin, gastric inhibitory peptide, cholecystokinin, vasoactive intestinal peptide.
