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Digestion

Digestion. In humans. Objectives. Looking at the processing of nutrients. You should be able to identify features of effective systems in heterotroph’s. Mechanical breakdown . What is this? Where does this occur? Why is it important?. Chemical Breakdown. What protein is used here?

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Digestion

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  1. Digestion In humans

  2. Objectives • Looking at the processing of nutrients. • You should be able to identify features of effective systems in heterotroph’s

  3. Mechanical breakdown • What is this? • Where does this occur? • Why is it important?

  4. Chemical Breakdown • What protein is used here? • Where does it occur? There are three main types...

  5. Amylase Protease Chemical Digestion - Digestive Enzymes Glucose Starch Amino Acids Protein Lipase Fatty Acid Glycerol Fatty Acid Fatty Acid Glycerol Fatty Acid Fatty Acid Fatty Acid Fatty Acids and Glycerol Fat

  6. Ingestion • Oral cavity/Mouth • Both mechanical and chemical digestion begin here • Food in the oral cavity triggers nervous reflex that triggers salivary glands. • More than 1L of saliva is secreted in a human per day. • In saliva is: • Mucin, protects mouth from abrasions, helps you swallow. • Buffers, stop tooth decay • Salivary Amylase, digestive enzyme that breaks down starch. • Mouth shapes food into a ball called Bolus which is pushed into the pharynx. • The pharynx is an intersection between the oesophagus & the windpipe.

  7. Digestion • Peristalsis squeezes a bolus along the narrow oesophagus through involuntary waves of smooth muscle contractions. • Starch is continually hydrolysed as it moves towards the stomach.

  8. Digestion • Stomach : stores food and performs preliminary digestion • is located on the LHS of the abdominal cavity, it breaks up food and delivers it to the duodenum • It is extremely elastic and has accordian style folds allowing it to hold up to 2L. • The epithelium lining stomach secretes gastric juices that: • Have a high concentraion of HCl (pH of 2). • Could digest iron nails • Disrupts extra cellular matrix • Kills bacteria • Include pepsin, breaks down protein. Food will remain in the stomach for up to 6 hours until it resembles a ‘soupy’ substance known as chyme.

  9. Digestion • Small intestines is the organ where: • Most hydrolysis takes place of macromolecules • Most absorption of nutrients into the blood. • In humans: • 6m long. • It is the longest section of the alimentary canal. • Called ‘small’ because of diameter. There are three defined regions in the small intestine: 1 the duodenum 2 the jejunum 3 the ileum.

  10. Digestion • Secretions from the pancreas enter the duodenum at the top of the small intestine. • These secretions, known as pancreatic juice, contain a mixture of amylase, trypsin, lipase and bicarbonate • Bicarbonate neutralised acid from stomach chyme and stops pepsin and protease from working • Bile, produced by the liver, passes down the bile duct and into the duodenum. If there is no food to digest in the small intestine bile is stored in the gall bladder. It’s involved in the mechanical breakdown of fats. • Lipases are enzymes that are produced by the pancreas and act on the fat droplets. They chemically break down fat into fatty acidsand glycerol. • Trypsin this enzyme acts on the long chain polypeptides and breaks them down to shorter-chain peptides.

  11. From the duodenum, food enters the jejunum and the ileum where digestion of all food nutrients continues.

  12. Absorption • The small intestines have the surface area of a tennis court. • High SA/V ratio from villi & microvilli. • Passive & Active transport used to absorb materials like glucose, amino acids, fatty acids & glycerol • Materials flow from capillaries & lacteal into hepatic portal vessel .

  13. Liver • Detoxifies/removes • Drugs • Alcohol • Stores • Gycolgen • Vitamins (A, D, E, K) • Fe and other minerals • Cholesterol • Activates vitamin D • Fetal RBC production • Phagocytosis • Metabolizes absorbed food molecules • Carbohydrates • Proteins • Lipids

  14. Large Intestines Are Involved In Water Reabsorption • Made up of two parts: colon and rectum • It compacts undigested food material, such as dietary fibre, and to absorb water and some salts back into the body. • This waste material, faeces, is eliminated from the body through the anus.

  15. Words to know • Oesophagus • Amylase • Salivary gland • Saliva • Peristalis • Stomach • Gastric Juices • Chyme • Pancreas • Amylase • Lipase • Small intestine • Liver • Colon • Anus • Faeces • Bile • Bile duct • Gallbladder

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