Chapter 17 – Part I Alimentary canal Mouth Pharynx Esophagus

Can you sort out the statements into True and False? Carbohydrates, proteins and fats are all made up of carbon, hydrogen, nitrogen and oxygen. Fats are made up of smaller units called amino acids Starch is a large carbohydrate molecule Starch molecules can be broken down by amylase. Proteins are made up of one or more glucose molecules Proteins are important for the growth and repair of cells

How do we break down the food we eat? 1. Mastication/Mechanical 2. Chemical Digestion  teeth  bile  stomach acid  enzymes

The Alimentary Canal The alimentary canal (or gut) is the tube within the body through which food passes and is processed in various ways

1. Mucosa - protects tissues and carries absorption 2. Submucosa - glands, blood vessels, nerves 3. Muscular Layer - smooth muscle tissue, circular & longitudinal fibers, pushes food (PERISTALSIS) 4. Serosa (serous layer) - visceral perineum, outer covering of the tube, lubricates surfaces (serous fluid) Layers of the Alimentary Canal

The Mouth

Teeth Enamel is the hardest substance in the human body.

Incisors – cutting and chopping food Cuspid (canine) – sharp and pointed for cutting and tearing food Bicuspids – cutting and chopping Premolars – crushing and grinding food Molars - grinding and mashing food

Get a mirror and look at a partner’s teeth. Identify each type of tooth – count them A dentist would write your dental records as: I: 2/2 C:1/1 PM: 2/2 M: 3/3. What do you think this means?

Dental Caries

What causes tooth decay? Saliva is slightly alkaline – it’s not that! When we eat, bacteria in your mouth feeds on the sugar and turns it to acid. The acids wear away the enamel. Decay has started in the enamel NO PAIN Decay has reached the dentine SLIGHT TOOTHACHE Decay reaches the pulp SEVERE TOOTHACHE Decay has spread down to the nerve root EXCRUCIATING PAIN!!

Meth Mouth  Dry mouth – xerostomia (no neutralization of acids)  Shrinking blood vessels  Erosive chemical  Compulsive grinding  Desire for sugar

Wisdom teeth

Digestion ‘the breakdown of large insoluble molecules into soluble molecules’

Absorption – only small particles can pass through cells, but large molecules can be broken down into smaller ones TASK: Copy and complete this diagram into your notes: starch G G G GUT INSIDE THE BODY (BLOOD) G G G BEFORE ABSORPTION GUT INSIDE THE BODY (BLOOD) AFTER ABSORPTION

Digestive Enzymes There are 3 main types of digestive enzymes: Amylase breaks starch down into glucose. Protease breaks protein down into amino acids. Lipase breaks fats down into fatty acids and glycerol

Salivary Glands Saliva is mixed with food during chewing Teeth assist the mechanical breakdown of food Saliva contains the enzyme amylase which starts the digestion of food Saliva contains mucus that keeps the mouth moist and lubricates food for easier swallowing

Digestive Enzymes Amylase Starch Glucose Protease Protein Amino Acids

Glycerol Fatty Acid Glycerol Fatty Acid Lipase Fat Fatty Acids and Glycerol

Digestive Juices SALIVA Salivary amylase GASTRIC JUICE Hydrochloric acid Pepsin (protease) LIVER bile PANCREATIC JUICE Pancreatic lipase Proteases (trypsin) INTESTINAL JUICE Mucus, various enzymes

Peristalsis

Pharynx nasopharynx oropharynx laryngopharynx

Esophagus esophageal hiatus is where it penetrates the diaphragm cardiac sphincter at entrance to stomach