Gastrointestinal system 5 Flashcards
What is the function of the GI tract
Obtain nutrients and replace fluid and salts lost
How is fluid and salt lost
Urine & faeces
Sweating
Breathing
How does the central nervous system regulate the GI tract
Activity over long distances - motility and secretion - modulates ENS
Parasympathetic - stimulates
Sympathetic - inhibits
How does the enteric nervous system regulate the GI tract
Local reflexes - peristalsis and segmentation
Submucosal plexus - secretion
Myenteric plexus - motility
Describe hormonal regulation in the GI tract
Largest endocrine organ in body
Endocrine and paracrine function
What are the 4 critical hormones of the GI tract
Gastrin
Gastric inhibitory peptide (GIP)
Secretin
Cholecystokinin (CCK)
What are the functions of motility
Aids chemical digestion and absorption
Mechanical digestion (surface area)
Mixing (chemical digestion)
Exposure to absorptive surfaces (absorption)
What basic tissue type controls motility
Smooth muscle - spontaneously active - without external input
How often do the parts of the GI contract
Stomach - 2 per min
Duodenum - 12 per min
Ileum - 9 per min
How is the strength of contraction regulated
Nervous and hormonal input
Describe fasting
Migrating motor complex
4 hours after a meal - every 2h until you eat again
House keeping - clear out flood
Describe the different types of mixing
Stomach - retropulsion
Small and Large intestine - Segmentation
How does storage in the stomach work
Relaxation of smooth muscle increases volume without changing pressure
Describe segmentation and peristalsis
Segmentation - contraction either side mixing food
Peristalsis - Contraction of one side moving food
What does chewing do
Reduces size
Mixes with saliva (taste)
Voluntary (skeletal)
Reflex control (strength, frequency, size)
Describe swallowing
Rapid transfer from mouth to stomach
Initially voluntary - becomes reflex
Where does majority of storage occur in stomach
Fundus and body
Where does mechanical digestion and mixing occur in the stomach
Antrum
Describe migrating motor complex
4 hours after meal - continues until you eat
1 hour of inactivity
50 mins uncoordinated activity
10 min coordinated activity
What does the vagus nerve control
Receptive relaxation and gastric accommodation
Describe peristalsis of the stomach
Starts on greater curvature and spreads to antrum
first 60 min following meal gentle
60-300 min more intense activity
Describe retropulsion of the stomach
Mixing and mechanical breakdown
Combination of peristalsis and opening and closure of the pyloric sphincter
How is gastric emptying rate maintained
Matches digestive capacity of intestine
Regulated by feedback from duodenum
What can affect gastric emptying
Size of meal
Composition of meal
How does size of meal effect gastric emptying
The larger the meal the faster the emptying
How does the composition of a meal effect gastric emptying
Fluids faster than solids - reduction of particle size increases surface area
Fats slow gastric emptying - difficult to digest
What are the functions of small intestine motility
Mixing with pancreatic, biliary and intestine secretions
Controlled movement
Exposure to absorptive surfaces
Describe the motility patterns of the small intestine
Between meals - Migrating motor complex
After meal - segmentation and limited peristalsis
What does segmentation in the LI do
Exposure to absorptive surfaces - absorb fluid and salt from faeces
Describe mass movement of the LI
1-2 times a day following meals
Peristaltic wave - moves faeces into rectum
Describe motility in the LI
Large periods of inactivity - storage of faeces
