Human Nutrition

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Nutrition

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The way that organisms obtain + use food to provide energy + carry out characteristics

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Heterotrophic

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Organisms cannot make their own food. Obtain nutrients by eating other animals.

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Autotrophic

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Organisms can make their own food through photosynthesis

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Herbivores

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Animals that feed on plants e.g. Rabbit

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Carnivores

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Animals that feed on other animals e.g. Fox

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Omnivores

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Animals that feed on plants + animals e.g. Badger

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Balanced Diet

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A diet that has correct amount of nutrients for body's needs

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Digestion

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Physical + chemical breakdown of food into soluble particles that can be absorbed into the body

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Mechanical Digestion

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Breakdown of food into smaller particles by teeth, churning of stomach or peristalsis

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Chemical Digestion

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Breakdown of food into smaller particles by enzymes, stomach acid or bile

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Stages of Human Nutrition

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1. Ingestion

2. Digestion

3. Absorption

4. Egestion

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Ingestion

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Food is taken into the body through mouth

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Digestion

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Food broken down into small molecules

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Absorption

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Nutrients (e.g. Amino acids) taken into bloodstream through walls of intestines

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Egestion

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Removal of unabsorbed materials known as faeces through anus

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Peristalsis

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Wave like contraction + relaxation of alimentary canal causing food to move through

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Types of teeth

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Function of incisors

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Cutting, biting

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Function of canines

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Tearing

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Function of Premolars + Molars

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Grinding

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The Human Dental Formula

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Amount of teeth in a human

I 2/2, C 1/1, PM 2/2, M 3/3

(half mouth)

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Areas of Mechanical Digestion

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Mouth, oesophagus, stomach

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Oesophagus

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A muscular tube 25cm long which connects mouth to stomach

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Stomach

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Muscular J shaped bag

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How long does stomach store food?

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4 hours

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Chyme

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Semi-solid liquid formed when stomach churns + mixes food with gastric juices

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Components of Saliva

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- Water > softens food

- Salts > make pH alkaline (pH 7.5) > optimum pH for salivary amylase

- Salivary amylase > breaks down starch into maltose

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Chemical Digestion in Mouth

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- Secretes saliva

- Food turned to bolus (easy swallow)

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Epiglottis

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Flap of skin that covers windpipe when swallowing which prevents food entering into it

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What ring of muscle does food enter the stomach through?

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Cardiac sphincter muscle

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What produces gastric juice in the stomach?

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Gastric glands in the stomach wall

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Components of Gastric Juice

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- Mucus > protects stomach lining as it is alkaline

- Hydrochloric acid > acid (pH2) that kills bacteria

- Pepsin > protease (breaks down protein) enzyme > breaks proteins into peptides

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Through what does chyme enter duodenum?

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Pyloric sphincter muscle

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Small Intestines

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25 ft long tube made up of:

> duodenum

> jejunum

>ileum

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What happens when acidic chyme arrives in duodenum?

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Hormones released > pancreas release pancreatic juice + gallbladder release bile

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Pancreas

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Feather shaped organ which lies underneath stomach

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Function of Pancreas

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Secretes pancreatic juice > contains water + alkaline salts > neutralises chyme + creates optimum pH for enzymes

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Function of Pancreatic Amylase in Duodenum

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Breaks down starch to maltose

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Function of Pancreatic Lipase in Duodenum

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Breaks down lipids to fatty acids + glycerol

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Function of Pancreatic Amylase in Duodenum

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Breaks down protein to peptides

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Location of liver

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Right of stomach under diaphragm connected to hepatic artery, hepatic vein + hepatic portal vein

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Functions of Liver

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- Produces bile

- Detoxes blood by removing poisonous substances (e.g. Drugs)

- Removes biliverdin + bilirubin pigments for breakdown of dead red blood cells

- Stores excess glucose as glycogen + fat soluble vitamins

- Excess proteins changed into urea

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Bile

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Yellow liquid alkaline that has bile salts which neutralises chyme from stomach

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Where is bile stored?

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Gallbladder

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How bile enters duodenum

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Through bile duct

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Functions of Bile

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- Emulsifies fats breaking them into smaller fat droplets (easier for lipase to work on)

- Activates pancreatic lipase

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Despite being a big factor in chemical digestion, bile doesn't contain...

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Enzymes

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Where is food almost fully digested?

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Ileum (small intestine)

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Chemical digestion in ileum by enzymes

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- Carbohydrates broken into monosaccharides

- Lipids broken into glycerol + fatty acids

- Proteins broken into amino acids

- Digested foods absorbed into bloodstream + lymph system through process of absorption

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Carbohydrate that cannot be broken down by enzymes

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Cellulose

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Path of amino acids + glucose to bloodstream

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Brought to liver via hepatic portal vein + to villi

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Path of glycerol + fatty acids to bloodstream

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Brought to lacteal + enter lymphatic system

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Adaptations of Small Intestines to Improve Absorption

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- Villi increase surface area for absorption

- Cells of intestines one cell thick

- Rich blood supply to carry digested nutrients around body

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Undigested remains of food that pass through colon (large intestine)

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Cellulose, water + bacteria

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What softens material as it moves through colon?

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Mucus secreting lining

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Functions of Large Intestines

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- Absorption of water + salts. As water is removed, waste becomes solid. Waste (faeces) passes to rectum where it is stored be removed by anus

- Symbiotic Bacteria produce vitamin B + K (break down cellulose)

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Symbiotic Bacteria

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Bacteria that live off another organism where at least one organism benefits

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Alternative terms for Fibre

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Roughage or cellulose

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Where is fibre found in cell?

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Plant Cell walls

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Benefits of High Fibre Diet

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- Helps absorb water which prevents constipation + diarrhoea

- Prevents bowel cancer as fibre removes carcinogens

- Provides feeling of fullness to prevent overeatinf

- Adds bulk to colon wall. Pressure against colon ensures waste is moved along to be removed.

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What does balanced diet depend on?

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Age, gender, activity level + general health

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