1. Chapter 5 (and a bit of Chp 4) Biology 25: Human Biology Prof. Gonsalves Los Angeles City College Loosely Based on Mader’s Human Biology,7 th edition

2. Integumentary System Components: Hair, skin, and nails. Functions: Protects the body from: Protects the body from:  Infection: Barrier to microbes.  Mechanical injury  Excessive heat or cold: Thermoregulation  Water loss Communication: Communication:  Receives stimuli from environment  Gives out subtle signals (blushing, etc.). Homeostatic Role:  Helps maintain constant body temperature.

8. 1. Digestive System Components: Mouth, salivary glands, throat, esophagus, stomach, intestines, liver, gallbladder, pancreas, rectum, and anus. Functions:  Ingest and mechanically break down food.  Digest food: Stomach and small intestine mainly.  Absorb nutrients and water.  Eliminate waste. Homeostatic Roles:  Supplies energy for life’s activities.  Supplies building blocks for macromolecules

9. Stages of Food Processing 1. Ingestion: The act of eating. Usually involves placing food in mouth or oral cavity. 2. Digestion: Macromolecules in food (fats, proteins, polysaccharides, etc.) are too large to be absorbed by digestive system. Must be broken down into small molecules (amino acids, simple sugars, etc.) so they can be absorbed and utilized by the body. Involves two processes: Mechanical: Chewing and churning. Chemical: Enzymatic breakdown of food.

10. Stages of Food Processing 3. Absorption: Cells lining the digestive cavity take up building blocks (simple sugars, amino acids, etc.), which then enter the bloodstream. Circulatory system distributes nutrients in blood to cells throughout the body. 4. Elimination: Undigested food materials are discharged from body.

11. Stages of Food Processing

12. Parts of the Human Digestive System Alimentary canal: Long tube like structure.  Mouth  Tongue  Pharynx (throat)  Esophagus  Stomach  Small intestine  Large intestine  Rectum  Anus Digestive glands: Produce enzymes, bile, and other substances important for digestion.  Salivary glands  Pancreas  Liver and gallbladder

16. Human Digestive System Mouth:  Ingest and mechanically break down food.  Digestion: Saliva lubricates and starts to digest food.  Starch is digested by salivary amylase  Other enzymes in saliva kill bacteria.

20. Part of the Human Digestive System Pharynx (Throat):  Throat opens into both the trachea (respiratory system) and esophagus (digestive system).  As food enters pharynx, swallowing reflex is triggered:  Esophageal sphincter relaxes  Epiglottis blocks tracheal opening  Food is directed towards esophagus Esophagus:  Muscular tube that conveys food to stomach.  Peristalsis: Wavelike involuntary muscle contractions squeeze food through alimentary canal (towards the stomach).

21. Swallowing Reflex and Esophageal Peristalsis

22. Smooth Muscle Peristalsis Moves Food Along Alimentary Canal

24. Part of the Human Digestive System Stomach:  Located on left side of abdominal cavity, right below diaphragm.  Stores food (can stretch to accommodate up to 2 liters of food and water), and breaks it down with acids and enzymes.  Gastric juice is secreted by stomach. Contains hydrochloric acid (HCl), enzymes (pepsin), and mucus.  Protein digestion starts in stomach with pepsin.  Food is churned in stomach with gastric juice to form chyme.  Food remains in stomach from 2 to 6 hours, after which it is released into the small intestine.

26. Part of the Human Digestive System Small Intestine:  Huge surface area, about 300 square meters.  Most digestion and absorption occurs here.  Pancreas and liver empty digestive enzymes and bile into the small intestine.  Pancreatic amylase: Breaks down starch  Trypsin and Chymotrypsin: Break down proteins  Lipases: Break down fats  Peptidases: Break down proteins  Nucleases: Break down DNA and RNA  Bile: Helps fat digestion by emulsifying fats.  Very large surface area for absorption due to:  Large circular folds (villi)  Tiny cell surface projections (microvilli).  Capillaries drain nutrients from small intestine and then sends them to first to liver and then rest of body.

28. Small Intestine is Site Most Enzymatic Digestion

31. Human Digestive System Large Intestine (Colon):  1.5 m long and 5 cm wide (diameter)  Most water absorption occurs here (up to 90%).  Undigested remainder of food is converted into feces.  Site of bacterial synthesis  Vitamin K  Folic acid  Biotin  Several B vitamins  Appendix: Small fingerlike projection. Involved in immunity. Rectum:  Stores feces until ready to eliminate

34. Human Digestive System Digestive Glands -- Liver: Structure Structure  Composed of 2 lobes made up of about 100,000 lobules Functions Functions  Removes bilirubin, a hemoglobin breakdown waste product, from the blood and incorporates it into bile.  Produces bile which is stored in gallbladder.  Bile is released into the small intestine after a meal.  Bile contains no enzymes, but helps solubilize fat particles.  Detoxifies blood by removing and metabolizing poisonous substances  Stores iron and fat-soluable vitamins A, D, E, K, and B 12  Makes plasma proteins, such as albumins and fibrinogen, from amino acids  Synthesizes and degrades glycogen to maintain homeostatic levels of glucose  Produces urea after breaking down amino acids

38. Pancreas:  Produces several digestive enzymes which are emptied into small intestine.  Enzymes digest starch (pancreatic amylase), protein (trypsin), fats (lipase), and nucleic acids (nucleases).

39. Contain H 2 0, HC0 3 - and digestive enzymes. Contain H 2 0, HC0 3 - and digestive enzymes. Pancreatic Juice EnzymeZymogenActivatorAction TrypsinTrypsinogenEnterokinaseCleaves internal peptide bonds ChymotrypsinChymotrypsinogenTrypsinCleaves internal peptide bonds ElastaseProelastaseTrypsinCleaves internal peptide bonds CarboxypeptidaseProcarboxypeptidaseTrypsinCleaves last amino acid from carboxyl- terminal end of polypeptide PhospholipaseProphospholipaseTrypsinCleaves fatty acids from phospholipids such as lecithin LipaseNoneNoneCleaves fatty acids from glycerol AmylaseNoneNoneDigests starch to maltose and short chains of glucose molecules CholesterolesteraseNoneNoneReleases cholesterol from its bonds with other molecules RibonucleaseNoneNoneCleaves RNA to form short chains DeoxyribonucleaseNoneNoneCleaves DNA to form short chains

40. Gallbladder Liver produces about 1,000 ml of bile a day with excess being stored in the gallbladder. Liver produces about 1,000 ml of bile a day with excess being stored in the gallbladder. Gallbladder reabsorbs water making bile thick and mucuslike. Gallbladder reabsorbs water making bile thick and mucuslike. Gallstones may form due to precipitation of cholesterol. Gallstones may form due to precipitation of cholesterol.

46. Vitamins and Minerals Small organic molecules that serve as coenzymes in metabolic reactions or have highly specific functions. Small organic molecules that serve as coenzymes in metabolic reactions or have highly specific functions. Must be obtained from the diet because the body does not produce them, or does so in insufficient amounts. Must be obtained from the diet because the body does not produce them, or does so in insufficient amounts. Certain vitamins function as antioxidants. Certain vitamins function as antioxidants. 2 classes of vitamins: 2 classes of vitamins:  Fat-soluble  Water-soluble

47. Vitamins Water-soluble vitamins: Water-soluble vitamins:  Serve as coenzymes in the metabolism of carbohydrates, lipids, and proteins.  May serve as antioxidants. Fat-soluble vitamins: Fat-soluble vitamins:  Serve as antioxidants.  Bind to nuclear receptors.  Involved in regulating fetal development.  Regulate Ca ++ balance.

49. Minerals Needed as cofactors for specific enzymes and other critical functions. Needed as cofactors for specific enzymes and other critical functions. Trace elements: Trace elements: Required in small amounts from 50  g to 18 mg/day. Required in small amounts from 50  g to 18 mg/day.

51. Free Radicals and Antioxidants Electrons are located in orbitals. Electrons are located in orbitals.  Each orbital contains a maximum of 2 electrons. Free radical: Free radical:  When an orbital has an unpaired electron.  Highly reactive in the body.  Oxidize other atoms or reduce other atoms. Major free radicals called: Major free radicals called:  Reactive oxygen or nitrogen species.  Oxygen or nitrogen as unpaired electron.

52. Free Radicals and Antioxidants Functions of free radicals: Functions of free radicals:  Help to destroy bacteria.  Produce vasodilation.  NO, superoxide radical, and hydroxy radical. Exert oxidative stress contributing to disease states. Exert oxidative stress contributing to disease states. Antioxidants: Antioxidants:  Protective mechanism against oxidative stress.  Can react with free radicals by picking up unpaired electrons.  Glutathione, vitamin C, and vitamin E.

54. Obesity Obesity is often diagnosed by using using a body mass index (BMI). Obesity is often diagnosed by using using a body mass index (BMI). BMI = w h 2 BMI = w h 2  W = weight in kilograms  H = height in meters Obesity in childhood is due to an increase in both the size and the # of adipocytes. Obesity in childhood is due to an increase in both the size and the # of adipocytes. Obesity defined as BMI > 30. Obesity defined as BMI > 30. Healthy weight as BMI between 19 – 25. Healthy weight as BMI between 19 – 25.