Human Nutrition Part 1

Nutrition  Process by which an organism obtains food.

Types of nutrition  Autotrophic Organism can make its own food Name such an organism?  Heterotrophic Organism cannot make its own food but must obtain it from its environment.

Heterotrophs 3 categories 1. animals that feed only on plants ________________ 2. Animals that feed on other animals ________________ 3. Animals that feed on plants & animals ________________

Digestion  This is the breakdown of food into particles that are small enough to pass into cells.  Digestion may be Physical ___________ or Chemical__________.

What is in the picture? Sponges have no digestive system and each cell has to digest its own food

Digestion Most animals have a digestion system and food is processed once, before being transported to all the cells in the body. Digestive system consists of the Alimentary canal, this is a long tube from mouth to the Anus.

4 stages of human Nutrition 1.Ingestion – Putting food into the mouth 2.Digestion Physical, food broken down by teeth & muscles Chemical, food is broken down by enzymes 3.Absorption Food is absorbed into the blood stream. 4.Egestion This is the removal of unabsorbed material

Alimentary canal in more detail  Now we will look at the following parts in more detail: The Mouth The Oesophagus The Stomach The Small Intestine The Pancreas The Liver The jejunum/ileum The Large Intestine

The Mouth  4 types of teeth 1.Incisors – Flat, sharp edges for cutting 2.Canines – Pointed to grip, tear & stab food 3.Premolars – Cusp for crushing & chewing food 4.Molars – Larger than premolar for crushing & chewing.

Baby Teeth!  First set of teeth in humans are milk teeth – no molars present

Herbivore  Only eats plants  Very large incisors  Large molars and pre-molars to chew grass.

Carnivore  Only eats meat  Large canine teeth  Use the teeth to catch and tear their prey

Omnivore  Eats plants and meat  Need all of the different teeth

The Mouth  Human Dental Formula 32 teeth 2( I 2/2 C 1/1 PM 2/2 M 3/3) Digestion in the mouth Physical- carried out by teeth, results in small particles of food which are easier to swallow and have a greater surface area. Chemical- Action of amylase enzyme, found in saliva. 3 glands- under tongue, back of jaws & in cheeks. Produce 1 litre of saliva a day

The mouth Saliva, helps soften & dissolve food  Consists of water, salts, mucous, and the enzymes amylase and lysozyme.  Amylase digests starch into maltose.  Lysozyme destroys micro-organisms found in sweat and tears also.  In the mouth food is formed into a ball and pushed backwards into the Pharynx. A flap called the epiglottis closes over the trachea to ensure the food goes down the oesophagus

 The food is chewed into a ball or Bolus and pushed into the pharynx, the epiglottis closes over the trachea when swallowing

Oesophagus (Food Pipe)  An involuntary wave of muscular action carries food to the stomach  This action is called Peristalsis  This action helps to break food down mechanically it mixes food with secretions of the stomach and forces food into small intestine it is also responsible for expelling faeces

Role of Fibre  Dietary Fibre (Roughage) consists of cellulose which humans cannot digest  Good sources are wholemeal bread, cereals, vegetables and fruit  Fibres stimulate peristalsis  Diet high in fibre reduces risk of colon cancer as wastes are moved through quickly