Circulatory System

Figure 24.01

Transports materials throughout body: Nutrients Metabolic wastes Gases (O 2 & CO 2 ) Hormones [regulate body processes] Antibodies Circulatory System Function

Components of Circulatory System: Blood –transport medium; –consists of cells suspended in liquid (plasma) Heart –Pumps the blood through the vessels Blood vessels –tubes that carry blood –including arteries, veins, capillaries

Components of Blood Plasma: (yellowish), contains water, minerals, salts, proteins, vitamins, hormones, dissolved gases and fats Red blood cells: carry oxygen Contain hemoglobin – no nucleus White blood cells: destroy pathogens (disease-causing organisms) bacteria, viruses Platelets: important part in blood clotting

Accounts for ~ 7% body weight Totals ~ 5 liters (a little over a gallon) in volume Blood

The Heart Double pump Right side: pumps O 2 -poor blood to lungs Left side: pumps O 2 -rich blood to body Each side has 2 chambers Atria : upper, thin-walled chambers, receive blood Ventricles: lower, thick-walled chambers, pump blood Septum: separates sides and prevents mixing

Heart Four Chambers Right Atrium Right Ventricle Left Atrium Left Ventricle Pumps Blood Through Vessels Septum – divides ventricles

Blood Flow Through Heart 1.Blood arrives in the atria of the heart 2. Blood flows from atria to ventricles 3. Blood leaves the heart from the ventricles From the Body From the Lungs

Blood Flow Through Heart Valves keep the blood moving in one direction Aortic Semilunar Pulmonary Semilunar Semilunars are found between ventricles and vessels

Blood Flow Through Heart Valves keep the blood moving in one direction TricuspidBicuspid or Mitral Atrioventricular (cuspid) valves are between atria and ventricles

Circulatory System Pathways: Three Branches: –Pulmonary circulation heart – lungs – heart –Systemic circulation heart – body – heart –Coronary circulation heart – heart

Path of a Red Blood Cell Vena cava Right Atrium –Tricuspid valve Right Ventricle –Pulmonary semilunar Pulmonary trunk Pulmonary arteries Lungs Pulmonary Veins Left Atrium –Bicuspid or Mitral Left Ventricle –Aortic semilunar Aorta Body cells

Arteries, Capillaries, Veins Blood Vessels

Carry blood away from heart Thick-walled Elastic fibers Muscle layer Blood under high pressure Small arteries called arterioles Diameter can be regulated Arteries

Exchange materials with surrounding tissue cells Capillaries Extremely narrow Only one cell thick Materials diffuse or actively transported through the lining All human cells less than 1 mm away from a capillary

All exchanges of materials occur through the capillaries

Return blood to the heart Thin-walled and wider diameter than arteries Low pressure - further from heart Valves keep blood moving towards heart Small veins called venules Veins

Blood Flow in Veins Blood pressure much reduced in veins Two ways to help blood get back to heart  Skeletal muscles help force blood back toward heart  Reduced pressure in thoracic cavity during inhalation Valves prevent backflow

Varicose Veins Veins with defective valves allow the blood to flow backward and pool inside the vein Veins become enlarged or dilated to form varicose veins

Blood flows from Heart  arteries  arterioles  capillaries  venules  veins  heart

Major arteries and veins Systemic Circulation Aorta: largest artery brings blood from the heart (left ventricle) to the rest of the body Inferior vena cava: vein brings blood from the legs and abdominal cavity to the heart (right atrium) Superior vena cava: vein that brings blood from the head and the arms to the heart (right atrium) Inferior Vena Cava Aorta Superior Vena Cava

Major arteries and veins Pulmonary Circulation Pulmonary arteries: bring blood from the heart (right ventricle) to the lungs Only artery with low oxygen Pulmonary veins: bring blood from the lungs to the heart (left atrium) Only vein with high oxygen Pulmonary Artery Pulmonary Vein

Major Arteries and Veins Aorta Pulmonary Arteries Pulmonary Trunk Pulmonary Veins Inferior Vena Cava Superior Vena Cava

Stages in the cardiac cycle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. superior vena cava right atrium inferior vena cava c. aorta pulmonary arteries atrioventricular valves b. semilunar valves a. pulmonary vein left atrium left ventricle right ventricle aorta Atria contract – Atrial systole Ventricles Contract – ventricular systole Atria and Ventricles relax - diastole

Control of Heartbeat: The Pacemaker Electrical impulse starts at the sino-atrial node and spreads across the atria, causing them to contract Impulse transferred to atrio-ventricular node, spreads across ventricles, causing them to contract

Brain/nervous system - Monitor blood circulation - maintain constant blood pressure -Send signals to heart, blood vessels, endocrine glands Red Bone Marrow - Site of new blood cell manufacture Supporting Organs

Kidneys - Metabolic waste products removed from blood - Balance of minerals and fluids, pH, glucose Spleen - Breaks down and filters out old red blood cells - Stores red blood cells - Recycles constituents, such as iron Spleen