Gastrointestinal system (flipped) Flashcards
What are the primary functions of the gastrointestinal system?
The GI system serves three main purposes:
Breaking down food into nutrients the body can use:
Energy sources: carbohydrates (glucose), proteins (amino acids), fats (fatty acids)
Supporting growth and repair (vitamins, minerals, amino acids)
Eliminating waste and undigested food
Contributing to overall health by:
Regulating blood sugar levels
Maintaining a healthy immune system
Promoting good mental health through microbiota
what is the GI tract?
A muscular tube that runs from the mouth to the anus. It’s responsible for the digestion and absorption of food, as well as the elimination of waste products.
Describe the basic structure of the GI wall and its layers.
The GI wall has four main layers:
1.mucousal layer: The innermost layer of the GI tract. It is made up of epithelial cells that are in contact with the food. The mucosa also contains glands that secrete mucus and digestive enzymes
2. Submucosal layer: connective tissue, glands, blood vessels
3. Circular and longitudinal smooth muscle layers
4. Serosa (squamous epithelia)
What is the main functions of the mouth?
-Mechanical disruption of food (mastication)
-Initial digestion through lingual lipase and amylase
-Saliva production for lubrication, antimicrobial protection and buffering (neutralise acid)
-sensory information relay to brainstem
What are the key features and functions of the oesophagus?
-Lined with stratified squamous epithelia
-upper sphincter controls entry into oesophagus
-Conducts swallowing reflex
-Controls food movement through primary and secondary peristaltic waves
-Contains upper and lower oesophageal sphincters
-Regulated by vagovagal reflex and PNS vagus nerve
Describe the three phases of stomach motility and its secretions.
- Receptive relaxation in Orad stomach to receive food
- Mixing of food with gastric juice in Caudad region to form chyme
- Gastric emptying through pyloric sphincter into small intestine
What roles do the pancreas, liver, and gallbladder play in digestion?
Pancreas:
Produces 1L of exocrine secretion daily
Secretes bicarbonate to neutralize stomach acid
Releases digestive enzymes
Parasympathetic nervous system stimulates secretion
Liver and Gallbladder (Bile):
Produces bile containing:
Water
Bile salts for lipid emulsification
Bilirubin (RBC waste product)
Cholesterol
Phospholipids
Electrolytes
95% of bile acids are recirculated
Liver produces bile, gallbladder stores and concentrates it
What are the main functions of the small intestine?
Digestion and absorption of nutrients (carbs, amino acids, fats, water, ions)
Mixing chyme with digestive enzymes and pancreatic secretions
Contains brush border enzymes for digestion
Increases surface area through three levels: Plicae, Villi, and Microvilli
Divided into three sections: Duodenum, Jejunum, and Ileum
What are the three primary functions of the large intestine?
- Absorption of water and electrolytes (Na⁺, Cl⁻, HCO₃⁻, K⁺)
- Production and absorption of vitamins K and B (via bacteria)
- Formation and propulsion of faeces
How is the GI system regulated by the autonomic nervous system?
3 divisions of ANS:
Sympathetic (extrinsic)
Parasympathetic (extrinsic)
Enteric Nervous System (intrinsic)
What is the enteric nervous system?
ENS is solely within GI tract
-Has 2 main plexuses- ganglia within submucosal + myenteric plexuses (inc. pancreas + biliary system)
-ENS contains over 100 million neurons (more than spinal cord)
-neurochemically complex
What are the different types of GI motility and how are they achieved?
Types of contractions:
Tonic: constant level of contraction/tone
Phasic: periodic contraction and relaxation (3-12/min)
Achieved through:
Slow waves (subthreshold membrane depolarization)
Action potentials
Interstitial Cells of Cajal (ICC) acting as pacemakers
Coordinated smooth muscle contractions via gap junctions
What are low pressure organs separated by? How many are there?
Sphincters- regulate food movement
6 sphincters
what is GI motility?
GI motility is a complex process that involves coordinated muscle contractions driven by neural and hormonal factors. These movements ensure efficient digestion, absorption, and elimination, maintaining overall gut health
