The Circulatory System

The Circulatory System

Major Function TRANSPORTATION Helps maintain homeostasis

within the body

Two sub-divisions Cardiovascular system Lymphatic system

The Cardiovascular System

Consists of: Blood

Transporting fluid Heart

Pumps the blood Carries the blood

Arteries, veins, capillaries

The HeartHeart wall has 3 layers

Epicardium, myocardium, endocardium

Made of cardiac muscle Rich in mitochondria

Four chamber Two Atria – upper chambers

Pumps blood to the ventricles Two Ventricles – lower chambers

Left pumps blood to the entire body Right pumps blood to the lungs

Blood Flow in the Heart Oxygen-poor blood enter through the superior & inferior

venae cavae into the right atrium Passes down through the tricuspid valve to the right

ventricle. Passes out the pulmonary trunk arteries to the lungs &

gas exchange occurs. Oxygen-rich blood returns via the pulmonary veins &

passes into the left atrium. Flows down through the bicuspid valve or mitral valve to

the left ventricle. Oxygen-rich blood then flows out the aorta to the body

tissues.

http://www.youtube.com/watch?v=Rj_qD0SEGGk

Physiology of the Heart

Heartbeat & Heart Sounds Two phases of the heartbeat

Diastole (relaxation) Occurs when the ventricle walls relax & blood flows into the

heart from the venae cavae & pulmonary veins Tricuspid & mitral valves open; pulmonary & aortic valves close

Systole (contraction) Walls of right & left ventricles contract; pumping blood into the

pulmonary artery & aorta Tricuspid & mitral valves are closed, preventing backflow

Physiology of the Heart Closure of the valves is associated with audible sounds

“lubb-dubb” “Lubb” associated with closure of the tricuspid & mitral valves at

the beginning of systole “Dubb” closure of the aortic & pulmonary valves at the end of

systole Murmur

Abnormal swishing sound http://www.dundee.ac.uk/medther/Cardiology/audio/norm

al.wav

http://www.dundee.ac.uk/medther/Cardiology/audio/ms.wav

Physiology of the Heart Conduction System

Sinoatrial Node (SA Node) (pacemaker)

Specialized muscle tissue that initiates the heartbeat Wave of electricity passes to another region of the

myocardium (within the interatrial septum) to the Atrioventricular node (AV node)

AV node sends excitation wave to atrioventricular bundle (bundle of His)

Bundle divides into the left bundle branch & right bundle branch

Physiology of the Heart

Electrocardiogram (ECG or EKG) Record used to detect the electrical changes in the

heart muscle

Blood Vessels

Arteries Large blood vessels that carry blood away from the

heart Lined with connective tissue, muscle, tissue, elastic

layer, & endothelium (innermost layer) Strong to withstand high pressure pumping from the

heart Arterioles

Smaller branches of arteries Thinner & carry blood to capillaries

Blood Vessels

Capillaries One endothelial cell thick Carry nutrient-rich, oxygenated blood from the

arteries & arterioles to the body cells Pick up waste products (i.e. CO2) & flow back to

the small venules, which combine to form larger vessels called the veins.

Blood VesselsVeins

Thinner walls compared with arteries Take blood toward the heart Have valves to prevent the backflow of blood

Blood Pressure Blood moves through our Circulation System because it is

under Pressure. caused by the Contraction of the Heart and by Muscles that

surround Blood Vessels. Blood Pressure is Always highest in the Two Main Arteries that

leave the Heart. Maintained by TWO WAYS:

(1) The Nervous System, which can speed up or slow down the Heart Rate;

(2) The KIDNEYS, which regulate blood pressure by the amount of fluid in our Blood.

When pressure is too high, kidneys remove water from blood, lowering the total amount of fluid in the Circulatory System. Both High and LOW Blood Pressure can cause our bodies problems.

Blood PressureUsually Measured in the Artery Supplying the

upper Arm. Measured by a sphygmomanometer

Systolic Blood Pressure force of blood recorded during ventricular

contractionDiastolic Blood Pressure

force of blood reordered during ventricular relaxation

Average blood pressure = 120/80 mm Hg

Factors Affecting Blood Pressure

Neural FactorsRenal Factors – KidneysTemperatureChemicalsDietAge & WeightExerciseEmotional State

Cardiac DisordersRisk factors of heart disease

High blood pressure, high blood cholesterol, cigarette smoking, obesity, lack of exercise, diabetes mellitus, and genetics.

Immediate Causes of Heart Disease Inadequate blood supply, anatomical disorders,

arrhythmiasCHF – Congestive Heart Failure

Heart cannot meet the body’s oxygen demands

The Lymphatic System Consists of lymphatic vessels,

lymph nodes, & lymph organs. Supports both Cardiovascular

System & the Immune System. Functions:

Picks up fluid leaked from the blood vessels & returns it to the blood.

Disposes of debris in the lymphatic stream

Houses WBCs involved in immunity

Lymphatic Vessels

Picks up excess tissue fluid called lymph, & returns it to the bloodstream. Fluid accumulation in tissues can cause edema, which

impairs blood-to-tissue exchange One-way system towards the heart Lymph capillaries absorb fluid in tissues Enters the venous system through two large ducts

Right lymphatic duct Thoracic duct

Lymph Nodes Removes foreign material

from the lymphatic stream by producing lymphocytes (WBCs) that function in immune response.

Act as tiny filters Contain macrophages that

engulf & destroy bacteria Swollen glands are a result

of trapping substances in the nodes.

Other Lymphoid Organs

Spleen Filters blood & destroys worn-out RBCs & returns

the breakdown products to the liverThymus

Produces hormones that program lymphocytes (immune system cells)

Tonsils Masses of lymphoid tissue embedded in mucus Trap any foreign material entering the throat.

http://www.youtube.com/watch?v=Kh-XdNnTZUo