Describe the adaptations of the ileum to its function. (20 marks)

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■Has secretory glands / crypts of lieberkuln which secretes enzymes (maltase / sucrose / peptidase / lipase to complete digestion of lipids / sugar / proteins.

■Goblet cells secrete mucus which allows for smooth movement of food / protect wall of ileum from action of digestive enzymes.

■Very long to provide large surface area for absorption

■Highly folded / coiled to slow movement of food to allow more time for digestion / absorption / increase surface area for absorption.

■Has numerous villi which increase surface area for absorption / microvillus which further increase surface area for absorption.

■Ileum wall / villi have thin epithelium which is only one cell thick to reduce distance over which digested food has to diffuse.

■Villi are highly vasculised / have a rich network of blood capillaries for rapid transport from small intestines / maintain a steep concentration gradient.

■Villi have lacteals for absorption of fatty acids and glycerol

■Cells of ileum wall have a large count of mitochondria to release energy that aid in active transport across the epithelium.

Max 20mks

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