6.1 Digestion and absorption Flashcards
How many major groups of organs is the digestive system made up of?
Two
What are the two major groups of organs the digestive system is made up of?
The alimentary canal and the accessory organs
What does the ailmentary canal consist of?
Organs where food actually passes
(oesophagus, stomach, small & large intestine)
What do the accessory organs of the digestive system comprise of?
Organs that aid in digestion but do not actually transfer food
(salivary glands, pancreas, liver and gall bladder)
What is the oesophagus?
A hollow tube connecting the oral cavity to the stomach
How is the oesophagus separated from the trachea?
By the epiglottis
What is food mixed with before entering the oesophagus?
Saliva
How is food moved in the oesophagus?
In a bolus via peristalsis
What is the stomach?
A temporary storage tank where food is mixed by churning and protein digestion begins
What is the stomach lined with?
Gastric pits that release digestive juices
What do the digestive juices in the stomach create?
An acidic environment
What is the small intestine?
A long, highly folded tube where usable food substances are absorbed
What are the three sections of the small intestine?
Duodenum
Jejunum
Ileum
What is the large intestine?
The final section of the alimentary canal where water and dissolved minerals are absorbed
What does the large intestine consist of?
Ascending/transverse/descending/sigmoidal colon and the rectum
What are the salivary glands?
Release saliva to moisten food and contains enzymes to initiate starch breakdown
What does the salivary glands include?
The parotid gland, submandibular gland and sublingual gland
What is the pancreas?
Produces a broad spectrum of enzymes that are released into the small intestine via the duodenum
What does the pancreas secrete?
Certain hormones which regulate blood sugar concentrations
What does the liver do?
Takes the raw materials absorbed by the small intestine and uses them to make key chemicals
What are the five roles of the liver?
Detoxification
Storage
Metabolism
Bile production
Haemoglobin breakdown
What does the gall bladder store?
Bile produced by the liver
Where is the bile stored in the gall bladder released?
Into the small intestine via the common bile duct
What are the two ways food can be digested?
Mechanical digestion and chemical digestion
How is food broken down in mechanical digestion?
It is broken down into smaller fragments via the acts of chewing, churning and segmentation
How is food initially broken down?
In the mouth by the grinding action of teeth
What does the tongue do in mechanical digestion?
Pushes the food towards the back of the throat
What does the epiglottis prevent?
The bolus from entering the trachea
What does the uvula prevent?
The bolus from entering the nasal cavity
What do the muscles in the stomach lining do?
Physically squeeze and mix the food with digestive juices
How long is the food digested within the stomach for?
Several hours
Once the food has been digesting in the stomach what does it turn into?
A creamy paste called chyme
Where does the chyme go after the stomach?
Into the small intestine where absorption will occur
What is peristalsis?
The principal mechanism of movement in the oesophagus
Apart from the oesophagus where else does peristalsis occur?
Stomach and the gut
How does peristalsis happen?
Continuous segments of longitudinal smooth muscle rhythmically contract and relax
In what direction is food moved along the alimentary canal?
Unidirectionally in a caudal direction
What does segmentation invlove?
The contraction and relaxation of non-adjacent segments of circular smooth muscle in the intestines
Which direction does segmentation contractions move chyme?
In both directions
What does the fact that segmentation contractions move chyme in both directions allow for?
Greater mixing of food with digestive juices
What is the downside to segmentation?
Its bidirectional propulsion of chyme can slow overall movement
How is food broken down in chemical digestion?
By the action of chemical agents
What is the pH of the stomach?
2
What does the acidic environment of the stomach function to do?
Denature proteins and other macromolecules to aid in their overall digestion
What does the stomach epithelium have to prevent the acids from damaging the gastric lining?
A mucous membrane
What does the alkaline compounds released by the pancreas do?
Neutralise the acids as they enter the intestine
What does the liver produce that is stored in the gall bladder?
Bile
What does the bile contain?
Bile salts
What do bile salts do?
Interact with fat globules and divide them into smaller droplets
What increases the total surface area available for enzyme activity?
The emulsification of fats
What are enzymes?
Biological catalysts which speed up the rate of a chemical reaction
What do enzymes allow digestive processes to occur at?
Body temperatures and sufficient speeds for survival requirements
How does enzymes being specific for a substrate help digestion?
It allows digestion of certain molecules to occur independently in distinct locations