The Gastrointestinal System Flashcards
What are the primary functions of the gastrointestinal system?
- regulated intake of food and water
- conversion of food into nutrients
- absorption of nutrients and water
- energy storage
- excretion of waste products
- protection against bacteria and toxins
What are the processes involved in the gastrointestinal system?
- sensory inputs: appetite, taste, smell, and sight
- mechanical and chemical breakdown of food
- secretion, absorption, and excretion
- the system is regulated by nerves, hormones, and local factors
What are the major subdivisions of the digestive tract?
(from mouth to anus)
- oral cavity, teeth, tongue
- pharynx
- esophagus
- stomach
- small intestine
- large intestine
How do the oral cavity, teeth and tongue contribute to the digestive tract?
Mechanical processing, moistening, mixing with salivary secretions
How does the pharynx contribute to the digestive tract?
Muscular propulsion of materials into the esophagus
How does the esophagus contribute to the digestive tract?
Transport of materials to the stomach
How does the stomach contribute to the digestive tract?
Chemical breakdown of materials via acid & enzymes; mechanical through muscular contractions
How does the small intestine contribute to the digestive tract?
Enzymatic digestion and absorption of water, organic substrates, vitamins, and ions
How does the large intestine contribute to the digestive tract?
Dehydration and compaction of indigestible materials in preparation for elimination
What are the accessory organs of the digestive system?
- salivary glands
- liver
- gallbladder
- pancreas
What are the 4 components of the gastrointestinal system’s structure?
(innermost to outermost)
- mucosa
- submucosa
- muscularis propria/externa
- serosa
(slide 5)
What are the components of the mucosa layer of the gastrointestinal system?
composed of three parts:
- mucosa epithelium
- lamina propria
- muscularis mucosa
What are the components of the submucosa layer of the gastrointestinal system?
- loose connective tissue
- exocrine glands
- nerves, blood and lymphatic vessels
What are the components of the muscularis propria/externa layer of the gastrointestinal system?
- inner circular smooth muscle
- outer longitudinal smooth muscle
What is the serosa composed of?
outer connective tissue
What is the enteric nervous system?
A network of autonomic nerves within the gastrointestinal tract that contains ganglia at the myenteric and submucosal plexus.
(slide 6)
What is the function of the enteric nervous system?
Controls smooth muscle contraction and exocrine/endocrine gland secretions within the gastrointestinal tract.
How is the enteric nervous system regulated?
Regulated by sympathetic and parasympathetic nerves, as well as sensory reflexes
What are interstitial cells of Cajal?
Specialized smooth muscle cells found in the gastrointestinal tract that act as pacemaker cells for gut motility.
What is the function of interstitial cells of Cajal?
Generate pacemaker activity that determines the frequency of slow waves in the gastrointestinal tract - crucial for the regulation of gut motility.
How do interstitial cells of Cajal control gut motility?
They generate and propagate electrical signals called slow waves, which in turn regulate the frequency and strength of muscle contractions in the gastrointestinal tract.
What is the circulation of the gastrointestinal system?
Collectively known as the splanchnic circulation, refers to the blood supply to the digestive organs.
How much blood volume does the splanchnic circulation contain?
approximately 15% of the total blood volume in the body
What is the function of the splanchnic circulation?
Transports absorbed nutrients and waste products for excretion from the digestive organs.
What is the portal circulation in the splanchnic circulation?
The blood flow between the gastrointestinal tract (GI) and the liver
How does the splanchnic circulation regulate blood flow?
Has adjustable resistance and acts as a reservoir of blood. It can undergo:
- vasodilation by parasympathetic control
- vasoconstriction by sympathetic control
What are the phases of digestion?
The different stages of the digestive process that are controlled by gut motility and secretions
What are the 3 phases of digestion?
- cephalic
- gastric
- intestinal
What is the cephalic phase of digestion?
- anticipation of feeding
- sensory input from food - thoughts, sights, smells, tastes
- mediated by vagal parasympathetic nerves
What is the gastric phase of digestion?
- presence of food in the stomach
- sensory input from food - stretch and chemicals
- mediated by parasympathetic and enteric nerve reflexes, hormones (e.g. gastrin)
What is the intestinal phase of digestion?
- presence of food in the intestines
- sensory input from food - stretch and chemicals
- mediated by parasympathetic and enteric nerve reflexes, hormones (e.g. secretin, CCK)
