GI Flashcards
What is the name of the muscular wave-like movements that move food along the GI tract
Peristalsis
What are the functions of tight junctions?
Hold cells together They block the movement of molecules and ions between the cells They block the movement of integral proteins between the apical and basolateral surfaces
Give the 4 main layers of the GI wall
Mucosa Submucosa Muscularis externa Serosa
GI wall: give the name of the loose connective tissue just below the epithelium through which pass vessels, nerves and lymph vessels
Lamina propria
Give the 3 layers of the mucosa
Epithelium Lamina propria Muscularis mucosa (thin layer of smooth muscle)
Contraction of which muscle in the submucosa is responsible for the moving and mixing of luminal contents?
Muscularis externa
The muscularis external has 2 muscles except in one organ where it has 3. Which organ is this?
The stomach
What are the two plexuses found in the GI wall?
The submucosal plexus (superficial) and the myenteric plexus
What 3 features are present on the surface of the small intestine to increase the SA?
Circular folds (mucosa & submucosa) Villi Micro villi
Where in the small intestine do new epithelial cells arise from?
New cells arise from division of the cells at the base of the villi. They differentiate as they move up the villi and replace those that die and are discharged into the lumen
Roughly, how many epithelial cells are replaced each day? a) 5 million b) 5 billion c) 17 billion d)23 billion
c) 17 billion
Roughly, how many epithelial cells are replaced each day? a) 5 million b) 5 billion c) 17 billion d)23 billion
c) 17 billion
At the centre of each intestinal villus, is a blind ended lymphatic vessel. What is it called?
Lacteal
What type of epithelium is in the small intestine?
Simple columnar with microvilli
What is the name of the regions of immune tissue which can be found in the small intestine?
Peter’s factors - these secrete factors that alter intestinal motility and kill microorganisms
Give the 4 main functions of saliva
Moistens and lubricates food Initiates small amounts of digestion of polysaccharides by amylase Dissolves small amounts of food which facilitates taste Kills bacteria
What are the functions of the stomach?
Store, dissolve and partially digest the macromolecules in food. Regulate the rate at which food is released into the duodenum.
Give the main food components which are not broken down by the stomach acid
Polysaccharides and fat
What molecules make up chyme?
Protein fragments, polysaccharides, fat droplets, salt and water and other molecules in ingested food.
How does the acidic environment in the gastric lumen aid digestion?
Alters the ionisation of polar molecules. Denatures proteins. Creates more sites for digestive enzymes. Disrupts the extracellular connective tissue proteins, reducing structural integrity of food.
Give the 3 parts of the small intestine
Dueodenum Jejunum Ilium
What are the 2 major organs which produce secretions that enter the small intestine?
Liver and pancreas
How is the pH of the chyme increased as it enters the small intestine?
The pancreatic fluid is rich in HCO3- to neutralise the acid preventing the pancreatic enzymes being denatured
What does bile contain?
Cholesterol HCO3- Phospholipids Bile pigments Bile salts Organic waste molecules
What is the role of the HCO3- produce from the liver?
HCO3- from the liver solubilises fats. The solubilisation of fats increases the rates at which they are digested and absorbed
In the small intestine, how do fats enter cells?
By diffusion
What are the 3 functions of the motility of the small intestine?
- Mixes luminal contents and secretions 2. Brings the contents into contact with the epithelium 3. Slowly moves the contents towards the large intestine
What is the ampulla of Vater?
The union of the common bile duct and the pancreatic duct
Where do the common bile duct and the pancreatic duct empty their contents in the small intestine?
The sphincter of Oddi.
What is important about the position of the sphincter of Oddi?
It is a landmark half way along the duodenum which marks the transition from the foregut to the midgut. The point where the celiac artery stops supplying the gut and the superior mesenteric artery takes over.
Which enzyme is responsible for up to 95% of starch digestion?
Pancreatic amylase
How does fructose enter the epithelial cells?
Fructose - facilitated diffustion with glucose via GLUT (GLUcose Transporter)
How do glucose and galactose enter the epithelial cells?
Active transport with Na+ via SGLT (Sodium GLucose Transporter)
How do fructose, glucose and galactose leave the epithelial cell at the basolateral membrane to enter the interstitial fluid?
Facilitated diffusion via GLUT
Where is the energy for absorption derived from from?
Na+/K+ - ATPase pumps on the basolateral membrane of the epithelial cells
Give the boundaries and the main artery of the midgut
3rd part of duodenum to 2/3rds along the transverse colon Celiac axis
Give the boundaries and the main artery of the foregut
Pharynx to 2nd part of the duodenum Superior mesenteric artery
Give the boundaries and the main artery of the hindgut
2/3rds along the transverse colon to the anus Inferior mesenteric artery
Which of the following does not have a ventral mesentery? a) foregut b) midgut c) hindgut
The midgut has no ventral mesentery (all have a dorsal mesentery)
What are the actions of the buccinator and supra hyoid muscles associated with?
They are the muscles of mastication
Which muscle depresses the mandible?
Mylohyoid
Which nerve and its branches passes through the parotid gland but does not innervate it?
The facial nerve
What type of secretion is produced from the parotid gland?
Serous secretion rich in amylase
What structures run through the parotid gland?
Facial nerve - gives rise to 5 branches within the parotid gland
External carotid artery
Retromandibular nerve
Nerve, artery & vein (Nerve to face, artery to external head and vein at the back of the mandible)
