When does the digestive process begin?
image of food triggers digestion as it the mouth releases saliva
How long is the digestive tract?
around 7 times longer than the length of the body
Ingestion meaning?
The process of taking food, drink, or another substance into the body by swallowing or absorbing it.
Digestion meaning?
The process of breaking down ingested foods into their basic units in preparation for absorption by the cells of the gastrointestinal tract.
Absorption meaning?
The movement of nutrients, water and electrolytes from the lumen of the small intestine into the cell, then into the blood.
Elimination meaning?
The food molecules that cannot be digested or absorbed need to be eliminated from the body. The removal of indigestible wastes through the anus, in the form of faeces, is defecation or elimination.
What happens at the mouth and oesophagus?
Teeth used to breakdown food so it can pass through oesophagus.
Ingestion and absorption of food and liquids takes place in mouth. Anything ingested moves to the oesophagus.
The muscles that aid the contraction of food down the oesophagus are known as sphincters.
Processes involved in the mouth and oesophagus?
Two types of digestion happen in the mouth:
Mechanical digestion (teeth and tongue) - catabolism
Chemical digestion (enzymes in saliva)
Enzymes used in the mouth and oesophagus?
Kallikrein - group of proteases in saliva
Amylase - breaks down starches to sugars
Lingual lipase - breaks down fats
- All in the saliva
What happens in the stomach?
Gets digested in the stomach.
Food and liquids are absorbed.
Processes involved in the stomach?
Produces enzymes and acids that breaks down food so it can pass to small intestine.
Enzymes used in stomach?
Pepsin - stomach enzyme that serves to digest protein found in ingested food
Gastric lipase - acidic lipase secreted by the gastric chief cells in the fundic mucosa of the stomach. pH level of 3-6
Special feature of the stomach?
Inside the stomach are rugae, ridges that increase the surface area of the stomach stretch out to increase stomach volume when the stomach is full.
What happens in the small intestine?
Food is broken down into liquid and most of its nutrients are absorbed.
The waste is passed on to the large intestine.
Processes involved in the small intestine?
Digestion, absorption and water absorption.
Chyme (partly digested food from stomach) is mixed with bile and pancreatic enzymes in the duodenum. This neutralises its acidity and breaks nutrients down into smaller molecules.
Enzymes used in the small intestine?
Amylase - starch into simple carbs (sugar)
Protease - breaks up proteins
Lipase - breaks down fats
Special features of small intestine?
Walls are lines with villi (finger like projections) which increases surface area. Each villi contains capillaries and a lymphatic vessel which nutrients are diffused into then transported to bloodstream.
Fatty acids go into the lymphatic vessel, amino acids and simple sugars flow into capillaries.
What happens in the large intestine?
Absorbs water and electrolytes.
When the water is absorbed, food turns into a solid (faeces)
Processes involved in the large intestine?
Absorption
Fermentation and storage of faecal matter.
Enzymes used in large intestine?
Maltase - breaks down maltose into two glucose molecules
Sucrase - breaks down sucrose and maltose into simple sugars
Lactase - breaks down lactose into simple sugars
Special features of large intestine?
Contains lots of bacteria that breaks down substances.
What is osmosis?
High concentration of water moves to area of low concentration through partially permeable membrane
What is passive diffusion?
Similar to osmosis, substances move with a concentration gradient.
Some can go straight through the membrane, others require a transport protein
Passive - doesn’t require energy.
What is facilitated diffusion?
Change shape to facilitate entry and exit
