Gastrointestinal physiology structure and function Flashcards
(20 cards)
What are the main components of the gastrointestinal (GI) tract?
The GI tract consists of the mouth, esophagus, stomach, small intestine, and large intestine.
What are the accessory organs of the GI tract and their functions?
The liver processes nutrient-rich blood from the stomach, the gallbladder releases bile, and the pancreas releases hormones for GI function.
What are the four layers of the GI tract wall?
Mucosal layer, submucosal layer, muscularis layer, and serosal layer.
What are the five primary functions of the GI tract?
Directionality of digestion, absorption of nutrients, secretion of digestive substances, excretion of waste, and protection against pathogens and toxins.
Why is smooth muscle important in the GI tract?
Smooth muscle enables directional motility, helping to move contents from mouth to anus efficiently.
What structures increase surface area in the gastric mucosa?
Gastric pits and glands.
What protects epithelial cells in the stomach from acid damage?
A mucus layer with a pH of around 7 buffers the acidic environment (pH ~1.5).
Match the following gastric mucosal cells with their secretions:
Parietal cells
ECL cells
D-cells
G-cells
Parietal cells → gastric acid
ECL cells → histamine
D-cells → somatostatin
G-cells → gastrin
What are the two main plexuses of the enteric nervous system?
The submucosal (Meissner’s) plexus and the myenteric (Auerbach’s) plexus.
How does the enteric nervous system operate independently?
It can function without input from the parasympathetic and sympathetic systems but is influenced by them.
What triggers the cephalic phase of digestion?
The sight, smell, or thought of food, activating the parasympathetic system and leading to acetylcholine release.
What happens during the gastric phase?
Food in the stomach stimulates stretch and pH receptors, triggering more acid secretion and motility.
What defines the intestinal phase of digestion?
When chyme enters the duodenum, it inhibits the stomach and stimulates hormone release from the gallbladder and pancreas.
What are the two main types of motility in the GI tract and where do they occur?
Peristalsis: occurs throughout the GI tract except the stomach.
Segmentation: occurs in the stomach.
What neurotransmitters control peristalsis and how?
Acetylcholine causes contraction behind the bolus via M3 receptors, and nitric oxide causes relaxation in front of it.
What is a bolus, and what happens to it after it is formed in the mouth?
A bolus is a roundish mass of chewed food that is swallowed and moves through the esophagus into the stomach.
What role does the mucosal layer play in digestion?
The mucosal layer contacts food directly and is responsible for nutrient absorption and secretion of digestive substances.
Why is it important for the GI tract to function in one direction?
Directional movement ensures proper digestion, absorption, and waste excretion while preventing issues like vomiting.
What is chyme, and where is it formed?
Chyme is the semi-digested mixture of food, enzymes, and gastric juices formed in the stomach before entering the duodenum.
How does segmentation aid digestion in the stomach?
Segmentation involves random contractions that break down the bolus into smaller parts, increasing surface area for enzymatic action.
