S1) Purpose of the Gut Flashcards
Label the following components of the digestive system:
Identify the 8 functions of the gut
- Port of entry for food into the body
- Mechanically disrupt the food
- Temporarily store the food
- Chemically digest the food
- Kill pathogens in the food
- Move the food along the tract
- Absorb nutrients from the resultant solution
- Eliminate residual waste material
Which areas of the GI tract mechanically disrupt food?
- Mouth/teeth
- Stomach (vigorous contractions cause the food to be liquefied – chyme)
Describe how the upper and lower areas of the stomach mechanically disrupt food
- Upper area creates basal tone (slow/sustained contractions)
- Lower area has powerful peristaltic contractions that effectively grind food (thicker muscle layer distally)
Why must the GI tract temporarily store food?
We eat faster than we digest
How does the stomach act as a storage facility?
- Distension – accommodates entry of food
- Receptive relaxation – maintains intraluminal pressures
Explain how the colon also acts as a temporary store
Contents are only evacuated several times a day from the colon (mass movements)
In which areas does chemical digestion occur?
- Oral cavity (saliva)
- Stomach
- Duodenum/jejunum
Which substances are used for digestion by saliva?
- Amylase (starch)
- Lipase (fats)
Which substances are used for digestion by the stomach?
- Acid
- Pepsin (protein)
Which substances/structures are used for digestion by the duodenum/jejunum?
- Bile
- Exocrine pancreas secretions
What are the challenges to the GI’s ability to kill pathogens?
- Thin epithelia
- Large surface area
What are the defences of the GI tract to pathogens?
- Saliva
- HCl
- Liver (kupffer cells)
- Peyers patches (immune surveillance)
I. Lymphoid follicles
II. Submucosa/mucosa (terminal ileum)
Different regions in the GI tract used different types of movement to move food along.
Identify them
- Peristalsis
- Segmentation
- Haustral shuttling
- Mass movements
What type of muscle is found in the bowel?
- Small amounts of skeletal muscle
- Mainly smooth muscle
What does the gut absorb?
- Digested food + secretions
- Fluids (fluid balance of the gut)
Which structural features of the gut aid absorption?
- Length of gut
- Folds
- Villi/microvilli
Describe, briefly, how residual waste is eliminated from the colon by mass movement
- Colon acts as temporary storage site, so the rectum is normally empty
- Internal/external anal sphincter open and residual waste is egested via the gastrocolic reflex
What is the broad function of the mouth?
- Physical breakdown of food
- Initial digestive enzymes released
- Infection control (lysozymes to digest any pathogens)
Identify 3 functions of the oesophagus
- Rapid transport of bolus (chewed food) to stomach through thorax
- Upper oesophageal sphincter prevents air from entering GI tract
- Lower oesophageal sphincter prevents reflux into oesophagus
Identify 4 functions of the stomach
- Storage facility
- Produces chyme (physical and chemical digestion)
- Infection control (HCl)
- Secretes intrinsic factor (aids digestion of Vit B12)
Identify 2 functions of the duodenum
- Neutralisation/osmotic stabilisation of chyme (HCO3 rich secretions)
- Concluding digestion: pancreatic secretions and bile
- can find it next to the stomach, it then changes direction retro-peritoneally and then comes back up on the left s
Identify 2 functions of the jejunum
- Final point of digestion
- Nutrient absorption
Identify 3 functions of the ileum
- Water/electrolyte absorption
- Bile recirculation
- B12 absorption (terminal ileum)
