3.3.3 Nutrition in the Human

Need to know The definition of Autotroph, heterotroph, herbivore, carnivore, omnivore and examples of each Know the definition of ingestion, digestion, absorption, egestion Understand the need for digestion and a digestive system

The way an organism obtains and uses its food Nutrition

Autotrophic Heterotrophic A type of nutrition where organism make its own food A type of nutrition where organism cannot make its own food

Herbivores Carnivores Animals that feed only on plants eg.. rabbit Animals that feed on other animals eg..fox

Omnivores Animals that feed on plants and animals Badger

Digestion definition The physical and chemical breakdown of food into soluble particles small enough to pass into body cells Need for Digestion To breakdown large food particles until they are small enough to pass into body cells

Need for a Digestive System Food can be digested in a single location Individual cells do not have to contain a full range of digestive enzymes

Stages in Human Nutrition Ingestion Digestion Absorption Egestion Food is taken into the alimentary canal Food is broken down into smaller soluble pieces The movement of digested material from the alimentary canal into the blood system Removal of unabsorbed material as faeces

Learning check Define Autotroph, heterotroph, herbivore, carnivore, omnivore Give an examples of each Define ingestion, digestion, absorption, egestion Explain (a)the need for digestion (b) the need for a digestive system

3.3.4 Human Digestive System

Need to know The functions of the main parts of the alimentary canal and the associated glands Function of teeth. The human dental formula Role of mechanical digestion and peristalsis Details of chemical digestion by one amylase, one protease and one lipase. Role of bile salts Symbiotic bacteria functions in the large intestine Benefits of fibre

The Digestive System

Mechanical breakdown of food 1. Teeth 2.Contractions in stomach wall 3. Peristalsis Rhythmic muscular contraction and relaxation in the wall of the alimentary canal causing the food to move along the canal

Human Teeth Canines Incisors Cutting Tearing Crushing and grinding Molars Pre molars

Human dental Formula Molars Pre molars Canines Incisors The number of each type of tooth in the upper jaw one side of the mouth i 2 2 c 1 1 pm 2 2 m 3 3

Learning check 1 Name four types of teeth Write down the human dental formula State the function of each of the four types of teeth Name the parts of the digestive system

Oesophagus Connects Pharynx to stomach Food moves down the Oesophagus by Peristalsis A muscular tube 25 cm long

Stomach J shaped muscular bag Stores food for about 4 hours Digest food Churns and mixes food with gastric juice forming Chyme

Digestion in the Stomach 2. Chemical Digestion using Gastric Juice containing a. Mucus b. HCl c. Pepsinogen 1. Mechanical Digestion Peristalsis physically breaks up food particles

Functions of gastric juice 1. Mucus 2. HCl 3. Pepsinogen Lines and protects the stomach wall a. Kills bacteria b. Activates pepsinogen Converted to the active enzyme Pepsin by HCL. Pepsin digests protein to peptides

Learning check 2 Define peristalsis What is the function of HCl in the stomach Why is pepsin secreted as inactive pepsinogen What is the function of mucus in the stomach

Sphincter Muscle Location Cardiac Sphincter Muscle Pyloric Sphincter Muscle Circular muscle which contracts to close the entry to duodenum from the stomach. ( Open when relaxed ) Circular muscle which contracts to close entry from oesophagus to stomach

Small Intestine Has three parts 1. duodenum 2. jejunum 3. ileum Muscular tube 5-6m long Functions Digestion Absorption

Duodenum 25cm muscular tube Function Most Digestion takes place in the duodenum

Jejuneum / ileum 2. Villi. Infoldings which increase the surface area available for the absorption of food Function Absorb nutrients Adaptations for absorption 1. Long tube. This gives time for absorption

Villi Infolding in the lining of the small intestine Function Increase surface area for absorption of digested food

A single Villus Fatty acids and Glycerol are absorbed into the Lacteal All other digested food are absorbed into the blood vessels

Large Intestine Appendix Caecum RectumAnus Colon

Large Intestine Functions (Colon) 1.Reabsorb water 2.Produce B group vitamins Functions 2 & 3 are carried out by symbiotic bacteria 3.Digest cellulose

Rectum Stores Faeces Appendix Caecum Function unknown in humans Large Intestine Functions

Role of the Liver in digestion The liver produces bile Bile is a yellow-green liquid Bile is stored in the gall bladder Bile enters the duodenum through the bile duct

Bile consists of 1.Water2.Bile salts3.Bile pigments 1.Emulsifies fatThis increases the surface area of the fat droplets 2.Neutralises the acidic chyme from stomach Function of bile

Learning check 3 State two ways in which the small intestine is adapted to absorb digested food Give the function of the liver in digestion What are the main functions of the large intestine How are the products of fat digestion transported away from the small intestine

Fibre stimulates peristalsis in the colon Helps prevent constipation Constipation results when undigested material passes through the colon too slowly. This leads to too much water being reabsorbed Benefits of dietry fibre

Three enzymes involved in digestion 1Amylase 2Pepsin 3Lipase Enzymes are biological catalysts

Salivary amylase Digest starch Production site Where it acts Role Salivary glands Mouth pH in mouth Alkaline, pH =8 Digestion product Maltose

Pepsin Digest protein Production site Where it acts Role Gastric glands in Stomach wall Stomach pH in stomach Acid, pH =2 Digestion product Peptides

Lipase Digest fat Production site Where it acts Role Pancreas Dudenum pH in duodenum Alkaline, pH =8 Digestion product Fatty acids + Glycerol

Learning check 4 Explain the benefits of fibre in the diet What is the product of the action of the protease Name a protease enzyme Give the site of action of the protease and state the pH at this location

3.3.5 Blood Transport of nutrients

Need to know Where and how digested nutrients are absorbed from the alimentary canal Learn how digested nutrients are transported to the liver Learn the main liver functions Learn how nutrients are transported to cells and how urea is transported to the kidneys

Absorption of Nutrients Glucose, Amino acids, vitamins and minerals pass into the blood capillaries Fatty acids and Glycerol are absorbed from the small intestine into the Lymphatic system for transport to liver The Hepatic Portal vein then brings these nutrients directly to the liver

Villi Infolding in the lining of the small intestine Function Increase surface area for absorption of digested food

Absorption of Nutrients by Villi A single Villus Fatty acids and Glycerol are absorbed into the Lacteal All other digested food are absorbed into the blood vessels

Blood Transport from Intestine to Liver The Hepatic portal vein connects the small intestine to the liver transporting glucose, amino acids, minerals and vitamins

Blood Transport of nutrients to Cells The Hepatic Vein transports nutrients and waste urea from Liver to heart From the heart nutrients are transported away from the heart through the Aorta to the body cells dissolved in the plasma From the heart waste urea is transported away from the heart to the kidney through the aorta dissolved in the plasma

Liver Functions 1.Make Bile 6.Make Urea from excess protein 4.Store Vitamins A, D, K 7.Produce Heat 2.Store Glycogen 8.Store Iron 3.Breakdown toxins 5.Make Plasma Proteins

Learning Check List six functions of the liver Name the blood vessel that connects the small intestine to the liver Explain how glucose, amino acids, vitamins and minerals are transported to cells Distinguish between the hepatic vein and the hepatic artery

Need to know Understand the term balanced diet Learn the main human food groups Understand how variety and moderation are important in having a balanced diet Draw a human food pyramid Relate human diet to age, gender and activity level Learn the recommended daily servings of each of the main food groups

Taking the correct amounts of all the essential nutrients in the diet Water Vitamins Protein Carbohydrate Minerals Fat Fibre

Eat a variety of foods Eat each food type in moderation

Depends on Young adults need more than older individuals Males need more than females More active individuals need more than less active people

Breads and cereals Fruit and vegetables Meat, fish and poultry Milk and milk products Fats, oils and alcohol

Build a Food Pyramid Cereals, Breads, potatoes Fruit Vegetables Milk, Products Meat Fish Poultry Oils Fats Alcohol

Cereals, Breads, potatoes Fruit Vegetables Milk, Products Meat Fish Poultry Oils Fats Alcohol Very few The daily food portions types an average adult should eat

Learning check Define Balanced diet List the five main food groups Give two general ways to ensure a balanced diet Draw a human food pyramid State the recommended daily average number of servings of each food groups

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