Chapter 6 Nutrition in Humans

1. Chapter 6Nutrition in Humans You Are what you Eat….

2. Nutrition • Have you wondered why do we eat?

3. Why do we eat? • Cos you’re hungry? • Cos your tummy aches? • Cos you just love to eat? • Cos you live to eat? • Cos you eat to live?

4. You Eat to LIVE! • We eat to supplement our body with nutrients. • So what type of nutrients do our body need? • Water • Carbohydrates • Fats • Proteins

6. Why do we eat? • You have to realise that everything in our body is made from the very items that you eat. • Proteins are used to create enzymes, mRNA, antibodies & muscles. • Fats are used to transport materials within the body and protect vital organs. • Carbohydrates are used to provide energy in our body.

7. Holozoic Nutrition • Holozoic means taking in complex organic matter such as proteins, carbohydrates and fats. • Nutrition is the process of taking in food & converting it into living matter.

8. Nutrition : 4 Step Process • Feeding / Ingestion • food is taken into the body • Digestion • large food molecules broken down into simpler soluble substances • Absorption • simple molecules absorbed into body cells • Assimilation • absorbed substances are converted & used in the body

9. Digestion • Physical Digestion • Mechanical break down of food into smaller particles. • Increases surface area of food for enzymes to act on. • Chemical Digestion • Break down of complex molecules into simple soluble molecules. • Eg : proteins  amino acids fats glycerol & 3 fatty acids

10. Animation Time • Let’s take a look at a simple animation on the digestive system. • http://kitses.com/animation/swfs/digestion.swf

11. Human Digestive System

12. Mouth Simpler Form! My Oldest Son Smells Like a Rotten Apple Oesophagus Stomach MOSSiLiRA Small Intestines Large Intestines Rectum Anus

13. Associated Organs • Associated Organs • Not in Digestive System • Has a role in Digestion • Liver • Gall Bladder • Pancreas

14. Mouth

15. Mouth • Teeth • Breaks large pieces into smaller pieces (Increase surface area) • Tongue • Mix food with saliva • Forms balls for easier swallowing • Salivary Glands • Ducts secrete saliva • Amylase and mucus

16. What Happens in the Mouth? • Physical Digestion • Chewing by teeth breaks food into smaller pieces. • Increase surface area of food enables more sites for enzyme action. • Chemical Digestion • Saliva contains salivary amylase • Salivary amylase is active at pH 7 • Salivary amylase digests starch  maltose

18. Parts of the Throat • Pharynx • Leads to both oesophagus and trachea (windpipe) • Trachea • Leads to lungs • Contains larynx (voice box) • Oesophagus • Leads to stomach • Epiglottis • Flap tissue that prevents food from entering the trachea.

19. Food digested is softened by mucin and rolled by the tongue to form bolus. • Bolus is a small and slippery round mass • Bolus moves into the Pharynx. • Epiglottis covers trachea. • Bolus moves into oesophagus

20. Swallowing Animation • http://leavingbio.net/Human%20Nutrition/Human%20Nutrition_files/image014.gif

21. Question Time 1 • Why do we eat? • What are the nutrients that we take in? • State both their complex and simple natures • What does Holozoic mean? • What does Nutrition mean? • Name the 4 Steps of Nutrition. • Explain each step. • What is the difference between physical & chemical digestion? • State the major parts of the Digestive System. • In the mouth, what aids physical digestion? • Which enzyme is found in the mouth? State it’s optimum pH and it’s chemical reaction.

22. FYI : Choking & Heimlich Manoeuvre

23. Oesophagus • Narrow muscular tube • Connects mouth to stomach • Consists of 2 muscles • Longitudinal muscles • Circular muscles (inside of gut) • Moves food by Peristalsis • Gravity helps push food down • NO ENZYMES! (Digestion)

24. Peristalsis • It is the rhythmic wave-like contractions of the gut walls. • Circular M contract, Longi M relax result in gut narrowing thus food is pushed forward. • Moves food by a series of muscular contractions and relaxations. • Helps mix food with digestive juices • Occurs for the entire alimentary canal

26. Stomach • It is a thick muscular bag. • Distensible • Expand & Contracts • Walls lined with gastric glands • Secretes gastric juices • Gastric juices contain hydrochloric acid & proteases Pepsin & Rennin. • Food stays for 4 hours • Liquifies bolus to chyme

27. Functions of HCL • Hydrochloric acid is at pH 2 (acidic) • Acid stops salivary amylase action by denaturing it (pH7) • Kills bacteria & harmful microorganisms • Provide optimum pH for enzymes • Activates proteases Pepsin & Rennin • Pepsinogen  Pepsin • Prorennin  Rennin

28. What happens in the stomach? • Physical Digestion • Peristalsis in stomach churns & breaks food • Peristalsis mixes bolus with gastric juices • Chemical Digestion • Pepsin digest proteins to polypeptides • Rennin curdles milk into insoluble casein protein which is digested into polypeptides by pepsin. • The digested bolus turns into liquified chyme and moves into the duodenum (small intestines).

29. FYI : Stomach Ulcers • Stomach ulcers thought to be caused by excess HCL. • 1982 - Australians Robin Warren & Barry J. Marshall self-experimented to show that Helicobacter pylori bacteria caused ulcers. • Marshall drank a petri dish of the bacteria to prove gastritis. • In 2005, both won a Nobel Prize in Medicine.

30. Small Intestines

32. Parts of the Small Intestines - DJI • Duodenum • Jejunum • ileum • 6m in length • Secretes digestive enzymes. • Adapted to absorb digested food

33. What happens in the Small Intestines? • Chyme from stomach  duodenum • Chemical Digestion • Intestinal Juice – Maltase, Sucrase, Lactase, Lipase, Peptidase • Pancreatic Juice – Pancreatic amylase, lipase & trypsinogen(protease) • Physical Digestion • Bile – produced in the liver and secreted by gall bladder & emulsify fat into smaller globules • All juices are alkaline in nature to neutralise acids. • Absorption by villi into bloodstream

34. Associated Organs • Associated Organs • Not in Digestive System • Has a role in Digestion • Liver (produce Bile) • Gall Bladder (secrete Bile) • Pancreas (digestive enzymes)

35. maltase lactase sucrase Carbohydrate Digestion • Mouth: little starch digested by amylase to maltose. • Duodenum: most starch digested by pancreatic amylase to maltose. • maltose glucose • lactose glucose + galactose • sucrose glucose + fructose • Carbohydrates digested to Simple Sugars

36. pepsin erepsin trypsin Protein Digestion • Proteins digested by Proteases • Stomach: Proteins digested to Polypeptides • Duodenum: Polypeptides digested to Amino Acids by peptidases from Pancreatic & Intestinal Juices • Stomach: proteins polypeptides • Duodenum • proteins polypeptides • polypeptides amino acids

37. lipase Fat Digestion • Duodenum: Bile from gall bladder emulsify fats • Lipases by Pancreatic & Intestinal Juices • fats glycerol + fatty acids

38. (2) Digestion  (3) Absorption • Duodenum – Food digested into simple soluble molecules • Simple Sugars – Glucose, fructose, galactose • Amino acids • Glycerol & fatty acids • After digestion, the simple soluble molecules can be absorbed by the small intestine villi. (Absorption Animation) • Nutrients move from small intestine villi(epithelial cell) hepatic portal vein  liver

39. Small Intestines consists of many folds of villus, each villus are lined with epithelial intestinal cells that each have finger-like projections known as microvilli. Microvilli increases surface area to volume ratio of the cell to facilitate greater absorption of nutrients.

41. Adaptations of Small Intestine for Absorption • Small Intestines (SI) have numerous folds • Each fold are villi • Each epithelial cell have finger-like projections • Villi have thin walls (one cell thick) • SI is long to allow more time for absorption of nutrients • SI have many blood capillaries to carry the nutrients through the hepatic portal vein to liver for detoxification.

42. Rate of Absorption • Surface area of small intestines (villus) • Membrane of epithelial cell (one cell thick) • Concentration gradient

43. Absorption in Intestines • Glucose & Amino acids are both passively & actively diffused into epithelial cells & blood capillary. • Glycerol & fatty acids passively diffuse into epithelial cells. Then transported into lacteals (lymphatic capillary) • Water & mineral salts absorbed by large intestines.

46. Hepatic portal vein brings nutrients to the liver for assimilation and detoxification. • Hepatic artery gives oxygenated blood to the liver. • Hepatic vein carries deoxygenated blood from the liver to the inferior vena cava and finally the heart.

47. Egestion : Rectum & Anus • Rectum • Food digested with it’s nutrients, water & mineral salts removed become faeces • Faeces are undigested & unabsorbed food • Faeces are temporarily stored • Anus • Site of removal of faeces by defecation

48. FYI : Stool Indicator

49. FYIWhy can’t we digest Cellulose? (Green Fibres)

50. What happens to nutrients in the bloodstream? • Blood rich in nutrients from villi  hepatic portal vein  liver • Assimilation occurs in the liver • Simple molecules constructed into complex molecules • Example: Glucose • Glucose used as source of energy for cellular activities • Excess glucose in bloodstream is bad for the body • Glucose converted to glycogen and stored in liver