BL - Digestive System Flashcards
Give some examples of “accessory organs” to the digestive system.
Salivary glands, liver, gallbladder, pancreas
What is the gut mesentery?
The double fold of peritoneum that attaches the intestines to the gut wall.
What are the four layers of the gut wall?
The mucosa, submucosa, external muscle layers and serosa.
True of false - Peyer’s patches are often present in the lamina propria of the gut wall?
True
What three components make up the muscosa (innermost component of gut wall)?
Epithelium, lamina propria, muscularis mucosae
What is the function of the muscularis externa?
It creates successive peristaltic waves to move luminal contents along the gut.
How many layers of muscle make up the muscularis externa?
2 - outer longitudinal layer and inner circular layer.
The serosa is an example of what type of membrane?
A serous membrane.
Where is connective tissue found in the gut wall?
Within the serosa
How can the muscularis externa be identified in pictures?
In the same image, there will be an inner layer of smooth muscle where the muscle cells have been cut through the middle, and an outer layer where they have been cut longitudinally.
What is the definition of digestion?
The conversion of what we eat, by physical and chemical disruption, into a solution from which we can absorb our nutrients
Give some functions of saliva
Starts digestion (amylase and lipase), bacteriostatic, high calcium to protect teeth, assists swallowing, protects mouth
Is the oesophagus under voluntary or involuntary control?
Upper is voluntary (striated skeletal muscle), lower is involuntary (just smooth muscle)
What is “chyme”?
Chewed up, partially digested stomach contents
How many layers of smooth muscle surround the stomach?
3 layers
Give examples of substances that can damage the mucous cells in the gastric pits. What happens after they are damaged?
Alcohol or aspirin; they are replaced via mitosis.
What is the function of surface mucous cells in the gastric pits?
They secrete mucus which contains HCO3- ions, which neutralise the effect of H+ ions and protect the stomach lining.
What is the isthmus of a gastric gland?
The region in which stem cells divide to populate the gland by upward or downward migration.
What is the name of the first portion of the small intestine?
The duodenum
The liver releases bile. What does it contain?
Water, alkali, bile salts (to emulsify fat)
How is hypertonic chyme rendered isotonic in the duodenum?
It is diluted by water from the ECF.
Which three sections make up the small intestine?
Duodenum, jejunum, ileum
What does the duodenum absorb?
Iron
What does the jejunum absorb?
Most of sugars, amino acids and fatty acids
What does the ileum absorb?
Vitamin B12, bile acids and remaining nutrients
Which comes first, the ascending colon or the descending colon?
Caecum -> ascending colon -> transverse colon -> descending colon -> sigmoid colon
What is a crypt of Lieberkühn?
An intestinal gland.
Where is most of the GI tract’s bacteria found?
The colon
What are the two neuronal plexuses of the gut wall?
Submucosal plexus and myenteric plexus
Which paracrine substances are released for gut control?
Histamine (controls acid production) and vasoactive substances (affect blood flow to gut)
What is the function of secretin?
Promotes bicarbonate secretion by duct cells of pancreas, promotes bile production by liver, inhibits secretion of acid by parietal cells of stomach.
What are the functions of cholecystokinin (CCK)?
Promotes release of digestive enzymes from pancreas, promotes release of bile from gall bladder, is a hunger suppressant
What is the function of gastrin?
Promotes production of HCl by parietal cells of the stomach
