The Circulatory System (p )

Transcription

1 The Circulatory System (p ) How Does Gravity Affect Blood Circulation? As with all land animals, the giraffe and the corn snake are constantly subject to the force of gravity The circulatory system keeps blood pumping despite gravity s pull Muscle contractions help blood travel uphill in the veins of a giraffe s long legs The wriggling of the corn snake squeezes its veins and increases circulation 1

2 Functions of circulatory system: transports O 2 and nutrients to cells (glucose) takes away CO 2 and other wastes (ammonia) Requires the action of: Blood: fluid tissue that carries nutrients, wastes, and other molecules Heart: muscular force to move blood around the body through blood vessels **your circulatory system is composed of 96,000 km of blood vessels!! 1. The Heart - muscular organ; ~the size of your fist -surrounded by a fluid-filled membrane: pericardium, which reduces friction -in every minute, 5 liters of blood cycles from the heart to the body and back to the heart 2

3 Chambers Chambers Each side has two hollow, muscular chambers which is separated by a wall called the septum Two thin walled atria receive blood Two thick walled ventricles pump out blood Valves 3

4 Valves Allow blood to flow in one direction only AV valve: separates atria & ventricle Semilunar valve: separates ventricles and arteries Tiny cords of tissue anchor flaps of the valves to the ventricle walls Heart murmur: the sound created by an improperly closing heart valve 4

5 2. Blood Vessels (text p ) i) Arteries Carry oxygenated blood AWAY from the heart (one exception: pulmonary artery is deoxygenated ) Walls are thick, strong and elastic Walls are composed of three layers Epithelium Basement membrane Epithelium Epithelium Smooth muscle Smooth CAPILLARY muscle Connective Connective tissue tissue Valve ARTERY VEIN ARTERIOLE VENULE Figure 23.5 atherosclerosis: degeneration of a blood vessel caused by the accumulation of fat deposits (cholesterol or triglycerides) along inside of vessel walls Connective tissue Smooth muscle Epithelium Plaque Figure 23.8B 5

6 Pressure is highest in the arteries It drops to zero by the time the blood reaches the veins Diastolic pressure Relative sizes and numbers of blood vessels Systolic pressure Figure 23.9A ii) Arterioles Smaller arteries Aneurysm: a thin, weakened section of the wall of an artery or vein that bulges outward and may burst. Stroke: blocked arteriole delivering oxygen to brain cells iii) Capillaries Smallest vessel in body (microscopic, single layer thick) Red blood cells must pass through single file Branch through tissues 6

7 Capillaries main function: the site of nutrients, waste, and gas exchange, by diffusion, between blood and tissue Capillary INTERSTITIAL FLUID Diffusion of molecules Tissue cell Figure 23.1B Bruise : capillaries under the skin have been broken and spill out blood iv) Veins Carry deoxygenated blood TOWARD the heart (one exception: pulmonary vein) Thin walled; carry blood under low pressure 7

8 Contain valves which open in one direction only Skeletal muscle contraction aids venous blood flow Direction of blood flow in vein Valve (closed) Valve (open) Skeletal muscle Figure 23.9B Three factors keep blood moving back to the heart muscle contractions breathing one-way valves Direction of blood flow in vein Valve (closed) Skeletal muscle Valve (open) Figure 23.9B 8

9 Varicose Veins: valves become weakened, blood flows backward and collects inside the vein, causing it to bulge 9

10 3. Pathways of the Circulatory System a) Pulmonary Circulation (pathway) Deoxygenated blood pumped from the right side of the heart to the lungs via the pulmonary arteries Lung capillaries Blood picks up oxygen and travels back to the left side of the heart via PULMONARY CIRCUIT the pulmonary veins The pulmonary arteries are the only arteries that are deoxygenated The pulmonary veins are the only veins that are oxygenated A A V V Right Left SYSTEMIC CIRCUIT Systemic capillaries Figure 23.3B 10

11 b) Systemic Circulation (pathway) Two large veins: the superior vena cava and inferior vena cava return blood to the right side of the heart Lung capillaries Left side of heart pumps blood to the entire body via the aorta (largest artery) PULMONARY CIRCUIT A A V V Right Left SYSTEMIC CIRCUIT Systemic capillaries Figure 23.3B From the aorta, the blood is diverted to: upper body arteries lower body arteries hepatic-portal system (starts with intestines and finishes in liver) Lung capillaries PULMONARY CIRCUIT A A V V Right Left SYSTEMIC CIRCUIT Systemic capillaries Figure 23.3B 11

12 Hepatic Portal System: Inferior vena cava Liver Hepatic vein Portal vein Intestines Hepatic Portal System: capillary beds of head and upper extremities Carries blood from the intestines to the liver (to pulmonary circuit) heart aorta (from pulmonary circuit) Allows liver to store and detoxify substances from digestive tract before they are carried to the body Hepatic vein capillary beds of other organs in thoracic cavity capillary bed of liver capillary beds of intestines Portal vein Hepatic Portal System: Inferior vena cava Liver Hepatic vein Portal vein Intestines 12

13 Hepatic Portal System: c) Coronary Circulation (pathway) Coronary arteries branch from the aorta into smaller vessels that provide oxygen-rich blood to the heart muscle Oxygen-poor blood then flows away from the heart muscle from capillaries to larger coronary veins that enter the right ventricle 4. Cardiovascular Disorders coronary artery disease (arteriosclerosis): accumulation of plaque (fatty deposits) in the coronary arteries that lead to a reduction in blood flow to the heart (p.277) 13

14 Heart: normal Heart: abnormally enlarged 14

15 angina: chest pain that is caused by reduced blood supply (oxygen) to the heart tissue; weakening the heart cells without killing them heart attack: lack of blood, and consequently oxygen supply to the heart tissue; killing heart cells coronary by-pass: -a surgical procedure in which a blood vessel from another part of the body is attached to a coronary artery so as to bypass an area of blockage 15

16 Pulmonary artery Aorta Superior vena cava RIGHT ATRIUM Pulmonary artery LEFT ATRIUM Pulmonary veins Pulmonary veins Semilunar valve Semilunar valve Atrioventricular valve Atrioventricular valve Inferior vena cava RIGHT VENTRICLE LEFT VENTRICLE Figure 23.4A Superior vena cava 7 Capillaries of Head and arms Pulmonary artery Pulmonary artery Capillaries of right lung 9 Aorta Capillaries of left lung Pulmonary vein RIGHT ATRIUM 1 5 Pulmonary vein LEFT ATRIUM RIGHT VENTRICLE 10 LEFT VENTRICLE Inferior Aorta vena cava Capillaries of abdominal organs 8 and legs Figure 23.4B 16

17 5. Control of the Heartbeat The SA node (pacemaker) generates electrical signals that trigger the contraction of the atria (located at top of right atrium) The AV node then relays these signals to the ventricles Pacemaker (SA node) AV node Specialized muscle fibers Right atrium Right ventricle ECG Figure 23.7 artificial pacemaker: electrical device surgically implanted which regulates the electrical impulses Pacemaker (SA node) AV node Specialized muscle fibers Right atrium Right ventricle ECG Figure

18 Heart with artificial pacemaker An electrocardiogram (ECG) is a recording of electrical changes in the skin resulting from the electrical signals in the heart Control centers in the brain adjust heart rate to body needs 6. The Heart (Cardiac) Cycle: sequence of heart chamber contraction/relaxation Diastole: relaxation Blood flows from the veins into the heart chambers Systole: contraction The atria briefly contract and fill the ventricles with blood Then the ventricles contract and propel blood out 1 Heart is relaxed. AV valves are open. DIASTOLE 0.4 sec 0.1 sec 0.3 sec 3 2 SYSTOLE Atria contract. Ventricles contract. Semilunar valves are open. Figure

19 7. Heart Sounds First sound( lubb ) caused by closing both AV valves Second sound ( dubb ) caused by closing both semilunar valves 8. Cardiac Output and Stroke Volume (p. 275) Heart rate: number of heart beats per minute (about 70) Stroke volume: amount of blood leaving the heart with each heartbeat (about 70 ml) Cardiac output: amount of blood pumped by the heart (ml/min) cardiac output = heart rate x stroke volume Average person s cardiac output is 5 liters: = 70 beats per min x 70 ml = 4900 ml/min Activity: Your Heart Performance Score 19

20 9. Blood pressure the contraction of the ventricles generates pressure exerted by blood on the walls of a blood vessel Blood pressure depends on 1. The volume of blood flow (cardiac output) 2. The resistance to blood flow caused by the narrow openings of arterioles Any change that affects these two factors will change blood pressure Systolic blood pressure: Left ventricle pumps out blood; pressure rises to a maximum of ~120 mm Hg Diastolic blood pressure: Left ventricle fills with blood; pressure falls to a minimum of ~80 mm Hg -Average blood pressure is 120/80 -healthier values may be lower, however it is possible to have blood pressure too low hypertension: persistently high blood pressure with systolic 140 or greater and diastolic 90 or greater 20

21 Why is hypertension a problem? The heart must work harder to pump blood which can cause it to enlarge and become weaker -----> coronary artery disease Accelerates atherosclerosis There is an increased force on blood vessels, which can cause them to weaken ----> rupture Life style changes to reduce hypertension: Exercise Lose weight Reduce intake of sodium (salt) Maintain a balanced diet Don t smoke Manage stress Limit alcohol intake Blood Pressure Lab 21

22 BIOLOGY Blood Pressure CONCEPTS & CONNECTIONS Fourth Edition Neil A. Campbell Jane B. Reece Lawrence G. Mitchell Martha R. Taylor The force exerted by blood against the inner walls of blood vessels (usually refers to pressure in large systemic arteries) From PowerPoint Lectures for Biology: Concepts & Connections When the cuff is inflated so that it stops arterial blood flow, no sound can be heard through a stethoscope placed over the brachial artery distal to the cuff. Korotkoff sounds are created by pulsatile blood flow through the compressed artery 22

23 Blood flow is silent when the artery is no longer compressed. Plastination by Gunther von Hagen: professor of anatomy 23

24 Professor of Anatomy: Gunther von Hagen 24

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