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In this IBDP Biology topic, you can learn about the digestive system in human.
- Absorption – taking soluble molecules into the body.
- Assimilation – incorporating absorbed molecules into body tissues.
Oesophagus:
- Carries food from the mouth to the stomach
- Adapted for transport rather than digestion or absorption.
- Made up of a thick muscular wall.
Stomach:
- Muscular sac with an inner layer that produces enzymes.
- Its role is to store and digest food, especially proteins.
- It has glands that produce enzymes which digest proteins.
- Other glands in the stomach wall produces mucus.
- Mucus prevents the stomach being digested by its own enzymes.
Small Intestine:
- It is a long muscular tube.
- Food is further digested here by enzymes that are produced by its walls and by glands that pour their secretions into it.
- Inner walls are folded into villi, which gives them a large surface area.
- Surface area of these villi is further increased by millions of tiny projections, called microvilli, on the epithelial cells of each villus.
- This adapts the small intestine for its purpose of absorbing the products of digestion into the bloodstream.
Large Intestine:
- Absorbs water.
- Most of the water that is reabsorbed comes from the secretions of many digestive glands.
- Therefore the food within the large intestine becomes drier and thicker in consistency and forms faeces.
Rectum:
- Final section of the intestines.
- Faeces are stored here before periodically being removed via the anus in a process called egestion.
Salivary Glands:
- Situated near the mouth.
- They pass their secretions via a duct into the mouth.
- These secretions contain the enzyme amylase, which breaks down starch into maltose.
Enzyme and Digestion
In humans digestion takes place in 2 stages:
- Physical breakdown – broken down by food to provide a large surface area for chemical digestion and stomach walls churn up food.
- Chemical breakdown – large insoluble molecules to small soluble molecules by enzymes
Hydrolases – enzymes which split up large molecules into smaller ones by a chemical reaction known as hydrolysis which involve adding a water molecule.
This is the end of the topic
Drafted by Eva (Biology)
Photo references:
- https://journals.rcni.com/nursing-standard/the-digestive-system-part-1-ns2014.02.28.24.37.e7395
- https://ib.bioninja.com.au/standard-level/topic-6-human-physiology/61-digestion-and-absorption/digestive-system.html
- https://www.pinterest.com/pin/397090892129861302/