The Digestive System Chapter 13 Why Do We Eat?

2 What is digestion?

Let’s find out what happened to your breakfast today!

4 Digestion Processing of Food (copy) Type oneMechanical (physical) Chewing Tearing Grinding Mashing Mixing

(Copy) Type twoChemical Catabolic reactions Enzymatic hydrolysis Carbohydrates Proteins Lipids

Ingestion Movement Digestion Secretion Absorption Excretion Functions of the digestive system (copy)

(Copy) Gastrointestinal System Includes alimentary canal and accessory organs Accessory organs: Salivary glands, tongue, teeth, liver, gallbladder, and pancreas

Steps in Digestion (Copy) Mouth – Crushing and grinding Stomach – Chemical Breakdown Small Intestine – Useful material extracted Colon – Water removal

Mouth -mechanical digestion mastication) = teeth, tongue -chemical digestion = saliva Uvula – prevents food entering the nose Alimentary canal (copy) 2 main functions: Digesting and absorbing nutrients Protecting from invasion

(COPY) Epiglottis – safety hatch. A flap of cartilage prevents food from entering the trachea Trachea - windpipe

11 Swallowing (Copy) Sequence Voluntary stage Push food to back of mouth Esophageal stage Open esophagus Start peristalsis

Oesophagus (Copy) -transfers food to stomach by peristalsis Cardiac sphincter -opens to allow food oesophagus stomach -heartburn –acid escapes stomach

13 Peristalsis and Segmentation

(Copy) Stomach Stores the food you eat Digestion = chemically - breaks it down into tiny pieces = mechanical – mixes food with digestive juices acid in the stomach kills bacteria Cardiac sphincter Pyloric sphincter Slowly releases food into intestine

Small Intestine (copy) Around 6m in an adult Food takes 1-6 h to pass through Enzymes and bile are added 2 main tasks = digestion, absorption nutrients pass into bloodstream through small intestine walls

16 Anatomy of the Large Intestine

Large Intestine (copy) About 1.5 meters long Accepts what small intestines don’t absorb. Absorbs water and minerals from the waste matter.

Liver (copy) Directly affects digestion by producing bile Bile is an enzyme that helps dissolve fat Processes nutrients in the blood, filters out toxins and waste.

19 Related Organs

Gall Bladder (copy) Stores bile from the liver Delivers bile when food is digested Fatty diets can cause gallstones

Pancreas (copy) Produces compounds to digest fats and proteins Neutralizes acids that enter small intestine Regulates blood sugar by producing insulin

22 The Organs and Positions in the Abdominal Cavity

Rectum and Anus (copy) Rectum About 15cm long Stores waste before egesting. Anus Muscular ring that controls egesting.