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.

• Carries food from the mouth to the stomach
• Adapted for transport rather than digestion or absorption.
• Made up of a thick muscular wall.

• 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.

• 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.

• 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.

• Final section of the intestines.
• Faeces are stored here before periodically being removed via the anus in a process called egestion.

• 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.

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

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Drafted by Eva (Biology)

Photo references:

1. https://journals.rcni.com/nursing-standard/the-digestive-system-part-1-ns2014.02.28.24.37.e7395
2. https://ib.bioninja.com.au/standard-level/topic-6-human-physiology/61-digestion-and-absorption/digestive-system.html
3. https://www.pinterest.com/pin/397090892129861302/