(b) Animal Transport and Exchange Systems National 5 Biology Key Area 6: The Need for Transport (b) Animal Transport and Exchange Systems

By the end of this lesson you will be able to .... Name the different parts of the digestive system State the function of each part of the digestive system Describe the mechanism of peristalsis Explain how the structure of the small intestine is related to its function. Explain how the villi and associated structures are adapted for absorption and transport of food particles.

Use these words to label the laminated diagram! Pancreas Stomach Anus Liver Salivary glands Mouth Large intestine Small intestine Rectum Oesophagus (gullet)

B A C I D J E F G Appendix H

Appendix

Digestion is a process where large insoluble molecules are broken down into small soluble molecules A balanced diet contains a mix of: ·   Carbohydrates Proteins Fats Carbohydrate—broken down into sugars. Used by the body as an energy source. Large insoluble molecule: starch Small soluble molecules: sugars These slides relate to the digestion foldable available in the Digestion folder. If it’s red they write it.

Protein—broken down into amino acids Protein—broken down into amino acids. Used by the body for growth and repair. Large insoluble molecule: Protein Small soluble molecules: Amino Acids These slides relate to the digestion foldable available in the Digestion folder. If it’s red they write it.

Fat—broken down into glycerol and fatty acids Fat—broken down into glycerol and fatty acids. Used by the body as an energy source and for insulation. Large insoluble molecule: Fat Small soluble molecules: Glycerol and Fatty Acids Glycerol These slides relate to the digestion foldable available in the Digestion folder. If it’s red they write it. Fatty Acids

The digestive system is made up of the alimentary canal which is a long muscular tube running from mouth to anus. The salivary glands, liver and pancreas (known as the associated organs) are connected to the alimentary canal by tubes called ducts.

Match the organ to it’s function! Mouth Muscular ‘bag’ that produces hydrochloric acid and digestive enzymes. Salivary glands Start of digestion. Teeth mechanically break down food. Oesophagus (gullet) Muscular tube connecting mouth to stomach Stomach Produces saliva. Saliva contains digestive enzymes that chemically break down food.

Pancreas Small Intestine Large Intestine Rectum Anus Highly folded muscular tube. Site of nutrient absorption. Contains ‘villi’. Small Intestine Removes water from waste to produce faeces. Large Intestine Faeces are excreted through this opening. Rectum Faeces is stored here before excretion. Anus Produces digestive enzymes and secretes them into the small intestine.

Peristalsis What is the alimentary canal made of? When food is swallowed it is pushed through the alimentary canal.

Peristalsis Peristalsis animation Really good! 3D Medical Animation - Peristalsis in Large Intestine/Bowel || ABP ©

Peristalsis Peristalsis is the contraction of muscles behind the food and relaxation of muscles in front of the food. This moves food along the entire alimentary canal. Bolus (food) Contract Relax

Small Intestine Good blood supply (nice and pink!) The small intestine is where the end products of digestion (small soluble molecules!) are absorbed into the blood stream (sugars, amino acids) and the lymph system (fatty acids and glycerol). 6.9 metres long – one inch wide. Good blood supply (nice and pink!) Long and highly folded = large surface area Can you see anything that would make it efficient at this?

Inside the small intestine…. The inner surface of the small intestine is highly folded – large surface area for absorption.

Inside the small intestine…. Hundreds of trillions of finger like projections called villi increase the surface area for absorption even more!

The Small Intestine The small soluble molecules produced by digestion pass through the small intestine wall by diffusion and enter the bloodstream and the lymph system. The small intestine has a large surface area for absorption because: It is long The inner lining is folded A large number of villi All of these features increase the surface area for absorption.

Structure of a Villus (pl. villi) Villi wall (one cell thick) – allows rapid diffusion of food molecules Lacteals – for the absorption of fatty acids and glycerol. Blood capillary – for the absorption of glucose and amino acids

a thin wall a large surface area a good blood supply How does villi structure make the absorption of molecules an efficient process? A villus has a thin wall a large surface area a good blood supply

The following diagram shows a cross-section of some villi in the small intestine. Explain why the structure and number of villi make absorption an efficient process in the small intestine. 3 marks Graeme Moffat said the national for this question was lass than 1 mark!

National 5 biology 2014, Section 2, Q4.