The Digestive System Flashcards
Define Nutrition
Nutrition is the process by which an organism obtains and uses its food.
Define digestion
Digestion is the physical and chemical breakdown of food into soluble particles that can be absorbed into the blood stream.
What is Mechanical digestion?
the physical breakdown of food i.e. using teeth, churning in the stomach.
What is chemical digestion?
the chemical breakdown of of food using enzymes or acids.
Whats the need for our digestive system?
- Food is only processed once.
- The material needed to process the food are in a single place.
- Individual cells do not have to contain a full range of digestive enzymes.
Whats the alimentary canal?
A long tube that strts at the mouth and ends at the anus.
Stages in Human Nutrition.
- Ingestion
- Digestion
- Absorption
- Egestion
Whats the name given to the process of mechanical digestion of food carried out by the teeth?
Mastication
What does Saliva consist of?
-Water
-Salts
-Mucous
-Amylase
Whats the Oesophagus?
The oesophagus is a thick, muscular walled tube that connects the pharynx to the stomach. The bolus (ball of food) travels down the oesophagus by peristalsis.
Describe peristalsis.
Peristalsis is the rhythmic contraction and relaxation of the wall of the alimentary canal, causing the food to move along it.
Define Heterotrophic
An organism cannot make its own food e.g. Herbivores, Omnivores, Carnivores.
Define Autotrophic
an organism can make its own food
What happens in the stomach?
Food enters the stomach through the cardiac sphincter muscle where it stores food for about 4 hrs. It churns food with gastric juice forming chyme, a semi-solid liquid. Chyme leaves the stomach through the pyloric sphincter muscle.
Give an example of mechanical and chemical digestion in the stomach.
Mechanical - The contraction of the stomach walls helps to break down food.
Chemical - The lining of the stomach ( the mucosa) is heavily folded, forming millions of gastric glands which secrete gastric juice.
What does gastric juice consist of?
Mucous : prevents self-digestion
Hydrochloric Acid : Gives the stomach pH of 1 to 2, activates pepsinogen, denatures salivary enzymes.
Pepsinogen : converts to pepsin… breaks down proteins into peptides.
The Small Intestine consists of …..
The duodenum and the Ileum
Main function of the duodenum
Digestion : produces a range of digestive enzymes, products from the pancreas and liver enter here.
Main function of the Ileum
To absorb nutrients. Adapted for absorption as it is a long tube and has many villi, increased surface area.
Villi
- covered in microvilli
- Walls are 1 cell thick, increases absorption.
Where do you find a lacteal and what is it?
Found inside each Villi, filled with lymph, fats are absorbed into the lacteal and transported to the bloodstream.
Why do humans not need the caecum and appendix?
They contain bacteria capable of digesting cellulose which humans don’t need to do.
Main function of the colon
Reabsorb water, absorb vitamins.
What are symbiotic bacteria
bacteria that live on or in another organism where at least one benefits. In the large intestine, they produce b group vitamins.
Main function of the Rectum and Anus
The rectum stores the faeces before egestion. The anus is where it is egested.
Functions of the liver (3)
Storage - minerals e.g. iron
Production - Bile and Urea
Breakdown - Red blood cells, toxic chemicals.
