Chap 7

• Essential nutrients for humans

  • Carbohydrates
  • Fats and oils
  • Proteins
  • Vitamin C
  • Vitamin D
  • Mineral ions like calcium
  • Iron
  • Fiber or roughage
  • Water
• Iron


  • Needed to make hemoglobin in red blood cells to carry oxygen around the body
  • Found in red meat and some green vegetables like spinach
• Mineral ions like calcium

  • Essential for strong and healthy bones and teeth
  • Has a role in blood clotting
  • Found in milk, cheese, and eggs
• Vitamin C


  • Maintains healthy skin and gums
  • Deficiency causes scurvy with symptoms like wounds not healing and excessive bleeding
  • Found in citrus fruits like oranges and lemons
• Associated organs of the digestive system

  • Salivary glands
  • Pancreas
  • Liver
  • Gall bladder
• Digestive system

  Breaks down large insoluble molecules into smaller soluble food molecules to provide the body with nutrients
• Proteins


  • Vital substance for growth and repair of tissues
  • Found in fish, meat, and eggs
• Carbohydrates

  • Provide energy for respiration in cells
  • Examples include rice, pasta, and potatoes
• Vitamin D

  • Helps the body absorb calcium for strong bones and teeth
  • Deficiency leads to rickets causing weak and soft bones and deformities
  • Found in dairy products, fish oil, and eggs
• Water


  • Needed for chemical reactions in cells
  • Can be obtained from both drinks and food
• Paths of the small and large intestines

  • Duodenum (first part of the small intestine)
  • Ilium (second part of the small intestine)
  • Colon (larger part of the large intestine)
  • Rectum and anus (parts of the large intestine)
• Functions of the organs of the digestive system

  • Ingestion (taking substances like food and drink into the body)
  • Digestion (breakdown of food)
• Fats and oils


  • Used as long-term stores of energy
  • A layer of fat under the skin acts as insulation
  • Examples include cheese, fatty meats, and butter
• Parts of the digestive system

  • Mouth
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
• Fiber or roughage


  • Helps food move through the stomach and intestines
  • Found in vegetables, fruits, and whole grains
• Physical digestion in the stomach

  1. Stomach walls squeeze the food to liquefy it

  2. Muscles in the stomach contract to physically squeeze and mix the food with digestive juices

  3. Bile plays an important role in physical digestion
• Types of digestion

  • Physical digestion
  • Chemical digestion
• Bile helps in digestion by emulsifying large fat droplets into smaller ones to increase the surface area for chemical digestion
• Parts of the large intestine

  • Rectum
  • Anus
• Role of bile in digestion

  1. Bile is produced in the liver and stored in the gall bladder

  2. Bile is released through the bile duct into the duodenum

  3. Bile is alkaline, neutralizes hydrochloric acid, and breaks down large fat droplets into smaller ones (emulsification)
• Functions of the organs of the digestive system

  1. Ingestion: taking substances like food and drink into the body

  2. Digestion: breakdown of food

  3. Absorption: movement of nutrients from the intestines into the blood

  4. Assimilation: uptake and use of nutrients by cells

  5. Ejection: removal of undigested food from the body as feces
• Physical digestion

  • Breakdown of food into smaller pieces without chemical change to the food molecules
  • Increases the surface area of food for the action of enzymes in chemical digestion
• Structure of a tooth

  • Enamel
  • Dentine
  • Pulp cavity
  • Nerves
  • Blood vessels
  • Cement
• Types of teeth in humans

  • Incisors
  • Canines
  • Premolars
  • Molars
• Functions of different types of teeth

  • Incisors: biting and cutting
  • Canines: tearing, holding, and biting
  • Premolars and molars: chewing and grinding
• Enzyme protease

  1. Pepsin breaks down protein to amino acids in the stomach

  2. Trypsin breaks down proteins to amino acids in the small intestine
• Enzyme lipase


  Breaks down fats and oils to fatty acids and glycerol
• Capillaries absorb glucose and amino acids and carry them away in the blood
• Chemical digestion is the breakdown of large insoluble molecules into small soluble molecules
• Enzyme amylase

  Breaks down starch to maltose, then maltose to glucose
• Role of bile in chemical digestion

  1. Emulsify fats

  2. Neutralizes the acidic mixture of food and gastric juices entering the duodenum

  3. Provides a suitable pH for enzyme action in the small intestine
• Functions of hydrochloric acid in gastric juice

  1. Kills harmful microorganisms in food

  2. Provides an acidic pH for optimum enzyme activity
• Role of chemical digestion

  • Produce small soluble molecules that can be absorbed
• Small intestine is the region where nutrients are absorbed most
• Function of absorption

  Movement of digested food molecules from the digestive system into the blood
• Where enzymes are secreted and act in the digestive system

  • Amylase: Produced by salivary glands and pancreas, acts in mouth and duodenum
  • Protease: Pepsin produced in the stomach and acts in the stomach, trypsin secreted by pancreas into duodenum
  • Lipase: Secreted by pancreas and acts in the duodenum
• Ilium is adapted for absorption with highly folded surface, villi, and microvilli
• Functions of enzymes in the digestive system

  1. Amylase breaks down starch to simple reducing sugars

  2. Protease breaks down protein to amino acids

  3. Lipase breaks down fats and oils to fatty acids and glycerol
• Villi greatly increase the surface area of the ilium for faster and more efficient absorption
• Lacteals absorb fatty acids and glycerol and transport them away in the lymph