2: Function of GI System Flashcards
What is the overall process of the GI tract?
Digestion makes food into a:
- Sterile
- Neutral
- Isotinic
solution of:
- Small sugars
- Amino Acids
- Small Peptides
- Small Lipid Particles
so it’s ready for absorbtion and excretion
What are the functions of the mouth and oesophagus? (3 things)
- Mastication
- Saliva
- Swallowing (Bolus formation)
What is the function of saliva?
- Protects mouth
- Bacteriostatic
- Alkaline
- High Calcium
- Lubricates food for mastication and swallowing
- Starts digestion (of sugars)
What are the functions of the stomach? (3 things)
- Storage (relaxes to accommodate food)
- Initial disruption
- Delivers chyme into duodenum
What occurs in the initial disruption in the stomach? (2 things)
- Contracts rhythmically → mixes and distrupts
- Secretes acid + proteolytic enzymes → breaks down tissues and disinfects
What is the function of the duodenum?
Dilution and neutralisation of chyme
How does the duodenum carry out its function of dilution and neutralisation? (3 things)
- Water drawn in from ECF
- Alkali (bile) added from liver and pancreas
- Enzymes added from pancreas and intestined
What are the functions of the small intestine? (2 things)
- Absorbs nutrients and electrolytes
- Absorbs majority of water
What allows the small intestine to absorb nutrients and electrolytes? (2 things)
- Fluid passes very slowly
- Large surface area
What does the absorbed stuff from the small intestine pass into?
Hepatic Portal Circulation
What are the functions of the large intestines?
- Final absorption of water
- Formation of faeces (which accumulate in descending sigmoid colon)
What is the speed of transit in the large intestines?
Very slow
How do you poo? (3 steps)
- Faeces propelled periodically into rectum
- Urge to defecate
- Controlled relaxation of sphincter and expulsion of faeces
What are the 4 layers of the alimentary canal? (From the oral cavity down to anus)
- Mucosa
- Submucosa
- Muscularis Externa
- Serosa / Adventitita
Inwards to outwards
What is the mucosa of the alimentary canal?
Epithelial lining and thin layer of SMC
What is the submucosa of the alimentary canal?
Fibroelastic tissue with:
- Vessels
- Nerves
- Leucocytes
- Fat cells
What is the muscularis externa of the alimentary canal?
2 layers of SMC:
- Inner circular layer
- Outer longitudinal layer
Myenteric plexus between layers
What is between the inner and outer layers of the muscularis externa of the alimentary canal?
Myenteric plexus
What is the serosa / adventitia of the alimentary canal?
Thin outer covering of connective tissue
How is chyme formed?
Food + saliva + gastric secretions
What are the propertie of chyme? (2 things)
- Hypertonic
- Acidic
What happens when chyme enters the duodenum?
Around 9L of water (and alkali) drawn into the duodenum from ECF via osmosis
What is the Enteric Nervous System a subdivision of?
Autonomic Nervous System
What is the nervous system of the GI system?
Enteric Nervous System
What is the Enteric Nervous System made up of?
2 nerve plexuses in the wall of the gut
What is special about the Enteric Nervous System?
It can act independantly of the CNS
They call it the 2nd brain
What is the most significant control over Enteric Nervous System?
Parasympathetic NS
What are the different classification types of hormones in the GI system? (2 things)
- Endocrine / Paracrine
- Gastrin / Secretin
