GIT Flashcards
What is long reflex?
Occurs when there is an outside presence of food. I.e. food is seen or smelt which begins the digestive process through salivation
What is the short reflex?
Occurs when there is food or substance present IN the GIT tract
What are the four functions of the oral cavity?
- ingestion and sensory analysis
- mastication
- lubrication
- limited digestion
What are the functions of saliva?
- chemical ad mechanical digestion beginning in the mouth
- exocrine secretion
- under autonomic control
Describe what salivary secretion does?
- softens and lubricates food
- chemical digestion: salivary amylase and some lipase
- saliva has a protective function
What is the protective function of saliva?
It is the first defense we have against bacteria
What is another name for swallowing?
deglutition
What is deglutition?
the swallowing reflex
- Tongue pushes bolus against soft palate and back of mouth, triggering swallowing reflex
- Breathing is inhibited as the bolus passes the closed airway
- Food moves down into the eosophagus, propelled by peristaltic waves and aided by gravity
What are the three functions of the stomach?
- storage
- digestion: lipids and proteins
- defense against swallowed pathogens
How does digestive activity begin in the stomach?
the long vagal reflex of the cephalic phase
What are the three exocrine cells in the stomach?
- mucus cells
- parietal cells
- chief cells
What are the endocrine/paracrine cells of the stomach?
- enterochramaffin-like (ECL) cells
- D cells
- G cells
What are the two most imprtant cells for stomach digestion?
parietal and chiief cells
Explain the steps of HCL secretions
Parietal cells pump H+ (from carbonic acid breakdown) into stomach lumen via H+/K+/ATPase (proton pumps)
- H+ requires active transport
- K+ can diffuse across the membrane
What are the two roles of HCl in the stomach?
- activates pepsinogen (zymogen) - converts it into active pepsin
- contributes to nonspecific disease resistance by destroying most ingested pathogens
What can be some negative side effects of HCl in the stomach?
Damage to the mucosa lining, breaking down protective measures resulting in erosion of the stomach wall, inflammation and peptic ulcer
What are the two types of control of gastric secretion?
neural and hormonal control
Explain neural control of the regulation of gastric secretion
- Acetylcholine (ACh) - released by intrinsic nerve plexuses within the stomach, under the control of short local reflexes and vagal stimulation