2.1 Gut Function Flashcards
What is the purpose of digestion and what does the solution comprise of?
Converts food to a: Sterile, Neutral, Isotonic solution containing:
Small sugars, amino acids, small peptides, lipids, other small molecules
Digestion is accomplished by the action of what 3 things?
1) HCl
2) bile
3) enzymes secreted by exocrine glands
What is Absorption
Specific active or passive uptake of nutrient molecules, water and electrolytes
Purpose of Excretion
To process, store and release: residues from food, gut debris, materials specifically excreted via liver to gut
List the accessory digestive organs
teeth, tongue, gallbladder, salivary glands, liver, spleen, pancreas,
Histological layers of the Ailmentary canal (4)
Mucosa
Submucosa
Muscular Externa
Adventitia/Serosa
Describe the Mucosa
lining epithelium, connective tissue, thin layer of smooth muscle
Describe the Submucosa
fibro-elastic tissue, vessels, nerves from Meissner’s plexus, fat and leukocytes
Describe the Muscularis externa
Inner circular and outer longitudinal layer of muscle
with Auerbach’s plexus located between layers
Describe the Adventitia/ Serosa
thin outer covering of connective tissue
Nerve plexuses are made up of post-ganglionic neurones of the _____ NS
Parasympathetic
List 4 properties of saliva that provide protection to the mouth
1) Wet
2) Bacteriostatic
3) Alkaline
4) High Calcium
Give an example of an enzyme found in saliva?
What does this do?
Amylase ➞ begins digestion of starch
What is Barett’s esophagus? (incl the epithelial change)
A pre-malignant shift from stratified squamous epithelia to simple columnar usually due to constant acid reflux (GERD)
Barett’s esophagus is often seen in patients who already have ______
GERD
What’s achalasia?
Absence of esophageal peristalsis and failure of the LES to relax in response to swallowing ➞ leads to impaired emptying of food from oesophagus into stomach
What is Dysphagia
difficulty swallowing
List 4 enzymes contained in pancreatic secretions
amylase
lipase
protease
nuclease
Where does dilution and neutralisation of chyme take place?
Duodenum and Jejunum
Where does storage, initial disruption and disinfection of food take place?
The stomach
Where does absorption of nutrients and and electrolytes take place
small intestine
List 3 features that provide a large SA for absorption in the small intestine
1) Plicae circulars - folds of mucosa and submucosa
2) villi - extensions of mucosa on plicae circularis
3) microvilli - enterocytes covering villi
What is a lacteal?
A lacteal is an enlarged lymphatic contained within the centre of each villus which aids absorption of fats
Where does final absorption of water and electrolytes take place
The large intestine ➞ faeces accumulate in the defending and sigmoid colon
What is meant by the term “controlled excretion”
The faeces are propelled periodically into the rectum
The urge to defecate occurs leading to controlled relaxation of of sphincters
Results in expulsion of faces
Which Nervous systems play a part in controlling the GI tract?
Somatic motor system for ingestion and excretion
Autonomic NS for everything else ➞ PNS is the most significant + Enteric nervous system, responsible for local control of secretion and motility
What are paracrine hormones? Give two examples
Chemical messengers diffusing locally:
1) Histamine in stomach
2) Vasoactive substances
What two structurally related groups do hormones in the gut come from?
Gastrin group
Secretin group
What is a bolus?
A mass of chewed food formed in the mouth from the Initial physical and chemical disruption
