Chapter 5 (and a bit of Chp 4)

Biology 25: Human Biology 25: Human BiologyBiology

Prof. GonsalvesProf. Gonsalves

Los Angeles City CollegeLos Angeles City College

Loosely Based on Mader’s Loosely Based on Mader’s Human BiologyHuman Biology,7,7thth editionedition

Integumentary SystemIntegumentary SystemComponents: Components: Hair, skin, and nailsHair, skin, and nails..Functions: Functions: Protects the body from:Protects the body from:

Infection: Barrier to microbes.Infection: Barrier to microbes. Mechanical injuryMechanical injury Excessive heat or cold: Excessive heat or cold: ThermoregulationThermoregulation Water lossWater loss

Communication: Communication: Receives stimuli from environmentReceives stimuli from environment Gives out subtle signals (blushing, etc.).Gives out subtle signals (blushing, etc.).

Homeostatic Role:Homeostatic Role: Helps maintain constant body temperature.Helps maintain constant body temperature.

1. Digestive System1. Digestive SystemComponents: Mouth, salivary glands, throat, esophagus, stomach, intestines, Components: Mouth, salivary glands, throat, esophagus, stomach, intestines,

liver, gallbladder, pancreas, rectum, and anus.liver, gallbladder, pancreas, rectum, and anus.Functions: Functions:

Ingest and mechanically break down food.Ingest and mechanically break down food. Digest food: Stomach and small intestine mainly.Digest food: Stomach and small intestine mainly. Absorb nutrients and water.Absorb nutrients and water. Eliminate waste.Eliminate waste.

Homeostatic Roles:Homeostatic Roles: Supplies energy for life’s activities.Supplies energy for life’s activities. Supplies building blocks for macromoleculesSupplies building blocks for macromolecules

Stages of Food ProcessingStages of Food Processing1. Ingestion:1. Ingestion: The act of eating. Usually involves The act of eating. Usually involves

placing food in mouth or oral cavity.placing food in mouth or oral cavity.2. Digestion:2. Digestion: Macromolecules in food (fats, Macromolecules in food (fats,

proteins, polysaccharides, etc.) are too large to proteins, polysaccharides, etc.) are too large to be absorbed by digestive system. be absorbed by digestive system. Must be broken down into small molecules Must be broken down into small molecules (amino acids, simple sugars, etc.) so they can be (amino acids, simple sugars, etc.) so they can be absorbed and utilized by the body. absorbed and utilized by the body. Involves two processes:Involves two processes:Mechanical:Mechanical: Chewing and churning. Chewing and churning.Chemical:Chemical: Enzymatic breakdown of food. Enzymatic breakdown of food.

Stages of Food ProcessingStages of Food Processing

3. Absorption:3. Absorption: Cells lining the digestive cavity take Cells lining the digestive cavity take

up building blocks (simple sugars, amino acids, up building blocks (simple sugars, amino acids,

etc.), which then enter the bloodstream.etc.), which then enter the bloodstream.

Circulatory system distributes nutrients in blood Circulatory system distributes nutrients in blood

to cells throughout the body.to cells throughout the body.

4. Elimination:4. Elimination: Undigested food materials are Undigested food materials are

discharged from body.discharged from body.

Stages of Food Processing

Parts of the Human Digestive SystemParts of the Human Digestive SystemAlimentary canal: Long tube like structure.Alimentary canal: Long tube like structure.

Mouth Mouth TongueTongue Pharynx (throat)Pharynx (throat) EsophagusEsophagus StomachStomach Small intestineSmall intestine Large intestineLarge intestine RectumRectum AnusAnus

Digestive glands: Produce enzymes, bile, and other Digestive glands: Produce enzymes, bile, and other substances important for digestion.substances important for digestion. Salivary glands Salivary glands Pancreas Pancreas Liver and gallbladderLiver and gallbladder

Human Digestive SystemHuman Digestive System

Mouth: Mouth:

Ingest and mechanically break down food.Ingest and mechanically break down food.

Digestion: Saliva lubricates and starts to digest Digestion: Saliva lubricates and starts to digest

food.food.

Starch is digested by salivary amylaseStarch is digested by salivary amylase

Other enzymes in saliva kill bacteria.Other enzymes in saliva kill bacteria.

Part of the Human Digestive SystemPart of the Human Digestive SystemPharynx (Throat):Pharynx (Throat):

Throat opens into both the trachea (respiratory system) and Throat opens into both the trachea (respiratory system) and esophagus (digestive system).esophagus (digestive system).

As food enters pharynx, swallowing reflex is triggered:As food enters pharynx, swallowing reflex is triggered: Esophageal sphincter relaxesEsophageal sphincter relaxes EpiglottisEpiglottis blocks tracheal opening blocks tracheal opening Food is directed towards esophagusFood is directed towards esophagus

Esophagus:Esophagus: Muscular tube that conveys food to stomach.Muscular tube that conveys food to stomach. Peristalsis:Peristalsis: Wavelike involuntary muscle contractions squeeze Wavelike involuntary muscle contractions squeeze

food through alimentary canal (towards the stomach).food through alimentary canal (towards the stomach).

Swallowing Reflex and Esophageal Peristalsis

Smooth Muscle Peristalsis Moves Food Along Alimentary Canal

Part of the Human Digestive SystemPart of the Human Digestive SystemStomach:Stomach:

Located on left side of abdominal cavity, right below diaphragm.Located on left side of abdominal cavity, right below diaphragm. Stores food (can stretch to accommodate up to 2 liters of food Stores food (can stretch to accommodate up to 2 liters of food

and water), and breaks it down with acids and enzymes.and water), and breaks it down with acids and enzymes. Gastric juiceGastric juice is secreted by stomach. Contains hydrochloric acid is secreted by stomach. Contains hydrochloric acid

(HCl), enzymes (pepsin), and mucus.(HCl), enzymes (pepsin), and mucus. Protein digestion starts in stomach with Protein digestion starts in stomach with pepsinpepsin.. Food is churned in stomach with gastric juice to form Food is churned in stomach with gastric juice to form chyme.chyme. Food remains in stomach from 2 to 6 hours, after which it is Food remains in stomach from 2 to 6 hours, after which it is

released into the small intestine.released into the small intestine.

Part of the Human Digestive SystemPart of the Human Digestive System

Small Intestine:Small Intestine: Huge surface area, about 300 square meters.Huge surface area, about 300 square meters. Most digestion and absorption occurs here.Most digestion and absorption occurs here. Pancreas and liver empty digestive enzymes and bile into the small Pancreas and liver empty digestive enzymes and bile into the small

intestine.intestine. Pancreatic amylasePancreatic amylase: Breaks down starch: Breaks down starch Trypsin and ChymotrypsinTrypsin and Chymotrypsin: Break down proteins: Break down proteins LipasesLipases: Break down fats: Break down fats PeptidasesPeptidases: Break down proteins: Break down proteins NucleasesNucleases: Break down DNA and RNA: Break down DNA and RNA Bile:Bile: Helps fat digestion by Helps fat digestion by emulsifyingemulsifying fats. fats.

Very large surface area for absorption due to:Very large surface area for absorption due to: Large circular folds (Large circular folds (villivilli)) Tiny cell surface projections (Tiny cell surface projections (microvillimicrovilli).).

Capillaries drain nutrients from small intestine and then sends them to Capillaries drain nutrients from small intestine and then sends them to first to liver and then rest of body.first to liver and then rest of body.

Small Intestine is Site Most Enzymatic Digestion

Human Digestive SystemHuman Digestive System

Large Intestine (Colon):Large Intestine (Colon): 1.5 m long and 5 cm wide (diameter)1.5 m long and 5 cm wide (diameter) Most water absorption occurs here (up to 90%).Most water absorption occurs here (up to 90%). Undigested remainder of food is converted into Undigested remainder of food is converted into fecesfeces.. Site of bacterial synthesisSite of bacterial synthesis

Vitamin KVitamin K Folic acidFolic acid BiotinBiotin Several B vitaminsSeveral B vitamins

AppendixAppendix: Small fingerlike projection. Involved in immunity.: Small fingerlike projection. Involved in immunity.

Rectum:Rectum: Stores feces until ready to eliminateStores feces until ready to eliminate

Human Digestive SystemHuman Digestive SystemDigestive Glands -- Liver:Digestive Glands -- Liver: StructureStructure

Composed of 2 lobes made up of about 100,000 lobulesComposed of 2 lobes made up of about 100,000 lobules

FunctionsFunctions Removes bilirubin, a hemoglobin breakdown waste product, from the Removes bilirubin, a hemoglobin breakdown waste product, from the

blood and incorporates it into bile.blood and incorporates it into bile. Produces Produces bilebile which is stored in gallbladder. which is stored in gallbladder. Bile is released into the small intestine after a meal.Bile is released into the small intestine after a meal. Bile contains no enzymes, but helps solubilize fat particles.Bile contains no enzymes, but helps solubilize fat particles. Detoxifies blood by removing and metabolizing poisonous substancesDetoxifies blood by removing and metabolizing poisonous substances Stores iron and fat-soluable vitamins A, D, E, K, and BStores iron and fat-soluable vitamins A, D, E, K, and B1212

Makes plasma proteins, such as albumins and fibrinogen, from amino Makes plasma proteins, such as albumins and fibrinogen, from amino acidsacids

Synthesizes and degrades glycogen to maintain homeostatic levels of Synthesizes and degrades glycogen to maintain homeostatic levels of glucoseglucose

Produces urea after breaking down amino acidsProduces urea after breaking down amino acids

Pancreas:

Produces several digestive enzymes Produces several digestive enzymes which are emptied into small which are emptied into small intestine.intestine.

Enzymes digest starch (pancreatic Enzymes digest starch (pancreatic amylase), protein (trypsin), fats amylase), protein (trypsin), fats (lipase), and nucleic acids (nucleases).(lipase), and nucleic acids (nucleases).

Contain HContain H220 , HC00 , HC033- - and digestive enzymes. and digestive enzymes.

Pancreatic Juice

Enzyme Zymogen ActivatorAction

Trypsin Trypsinogen EnterokinaseCleaves internal

peptide bonds

Chymotrypsin Chymotrypsinogen TrypsinCleaves internal

peptide bonds

Elastase Proelastase TrypsinCleaves internal

peptide bonds

Carboxypeptidase Procarboxypeptidase TrypsinCleaves last

amino acid from carboxyl-terminal end of polypeptide

Phospholipase Prophospholipase TrypsinCleaves fatty

acids from phospholipids such as lecithin

Lipase None NoneCleaves fatty

acids from glycerol

Amylase None NoneDigests starch

to maltose and short chains of glucose molecules

Cholesterolesterase None NoneReleases

cholesterol from its bonds with other molecules

Ribonuclease None NoneCleaves RNA to

form short chains

Deoxyribonuclease None NoneCleaves DNA to

form short chains

Gallbladder

Liver produces about 1,000 ml of bile a Liver produces about 1,000 ml of bile a day with excess being stored in the day with excess being stored in the gallbladder.gallbladder.

Gallbladder reabsorbs water making bile Gallbladder reabsorbs water making bile thick and mucuslike. thick and mucuslike.

Gallstones may form due to precipitation Gallstones may form due to precipitation of cholesterol.of cholesterol.

Vitamins and Minerals Small organic molecules that serve as coenzymes Small organic molecules that serve as coenzymes

in metabolic reactions or have highly specific in metabolic reactions or have highly specific functions.functions.

Must be obtained from the diet because the body Must be obtained from the diet because the body does not produce them, or does so in insufficient does not produce them, or does so in insufficient amounts.amounts.

Certain vitamins function as antioxidants.Certain vitamins function as antioxidants. 2 classes of vitamins:2 classes of vitamins:

Fat-solubleFat-soluble Water-soluble Water-soluble

Vitamins Water-soluble vitamins:Water-soluble vitamins:

Serve as coenzymes in the metabolism of Serve as coenzymes in the metabolism of carbohydrates, lipids, and proteins.carbohydrates, lipids, and proteins.

May serve as antioxidants.May serve as antioxidants. Fat-soluble vitamins:Fat-soluble vitamins:

Serve as antioxidants.Serve as antioxidants. Bind to nuclear receptors.Bind to nuclear receptors. Involved in regulating fetal development.Involved in regulating fetal development. Regulate CaRegulate Ca++++ balance. balance.

Minerals

Needed as cofactors for specific enzymes Needed as cofactors for specific enzymes and other critical functions.and other critical functions.

Trace elements:Trace elements: Required in small amounts from 50 Required in small amounts from 50 g to g to

18 mg/day.18 mg/day.

Free Radicals and Antioxidants Electrons are located in orbitals.Electrons are located in orbitals.

Each orbital contains a maximum of 2 Each orbital contains a maximum of 2 electrons.electrons.

Free radical:Free radical: When an orbital has an unpaired electron.When an orbital has an unpaired electron. Highly reactive in the body.Highly reactive in the body. Oxidize other atoms or reduce other atoms.Oxidize other atoms or reduce other atoms.

Major free radicals called:Major free radicals called: Reactive oxygen or nitrogen species.Reactive oxygen or nitrogen species.

Oxygen or nitrogen as unpaired electron.Oxygen or nitrogen as unpaired electron.

Free Radicals and Antioxidants Functions of free radicals:Functions of free radicals:

Help to destroy bacteria.Help to destroy bacteria. Produce vasodilation.Produce vasodilation.

NO, superoxide radical, and hydroxy radical.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.Protective mechanism against oxidative stress. Can react with free radicals by picking up unpaired Can react with free radicals by picking up unpaired

electrons.electrons. Glutathione, vitamin C, and vitamin E.Glutathione, vitamin C, and vitamin E.

Obesity Obesity is often diagnosed by using using a body Obesity is often diagnosed by using using a body

mass index (BMI).mass index (BMI). BMI = BMI = ww

h h 22

W = weight in kilogramsW = weight in kilogramsH = height in metersH = height in meters

Obesity in childhood is due to an increase in both Obesity in childhood is due to an increase in both the size and the # of adipocytes.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.