The Circulatory System

“ A Transport Service”

Circulatory System Consists of…

• Heart

• Blood Vessels

• Blood

HEART: The Vital Pump

On average, the heart contracts 72 times a minute, pumping about 5 quarts of blood.

Structure and Function

• Keeps blood moving• Large organ

composed of – cardiac muscle, – rich in mitochondria– Enclosed by a

PERICARDIUM sac

Structure of Heart (cont)

• Four chambers :

– Two upper (Atria)

– Two lower (Ventricles)

Right Ventricle

Right Atrium

Left Atrium

Inferior Vena CavaVein that brings oxygen-poor blood from the lower part of the body to the right atrium

Tricuspid ValvePrevents blood from flowing back into the right atrium after it has entered the right ventricle

Pulmonary ValvePrevents blood from flowing back into the right ventricle after it has entered the pulmonary artery

Pulmonary VeinsBring oxygen-rich blood from each of the lungs to the left atrium

Superior Vena CavaLarge vein that brings oxygen-poor blood from the upper part of the body to the right atrium

AortaBrings oxygen-rich blood from the left ventricle to the rest of the body

Pulmonary ArteriesBring oxygen-poor blood to the lungs

Aortic ValvePrevents blood from flowing back into the left ventricle after it has entered the aorta

Mitral ValvePrevents blood from flowing back into the left atrium after it has entered the left ventricle

Left Ventricle

Septum

Structures of the Heart

Blood Flow Through the Heart

©COPY 1997 HeartPoint

Blood Flow Through the Heart

• Both Atria fill at same time

– Right atrium receives oxygen POOR blood from body through vena cava

– Left atrium receives oxygen RICH blood from lungs through four pulmonary veins

• After filled with blood atria contract, pushing blood into ventricles

STEP 1

STEP 2

•Both ventricles contract

Right ventricle contracts and pushes oxygen-poor blood toward lungs,

-against gravity-through pulmonary arteries

STEP 3

Left ventricle contracts and forces oxygen rich blood • out of heart through aorta (largest vessel)

This creates the “lub” sound of the heartbeat.

STEP 4

• As the ventricles relax, the valves snap shut.

• Blood start filling the atria, and the cycle begins again.

This creates the “dub” sound, finishing the heartbeat.

Heart - as two separate pumps:

• Circulation of blood between the heart and the lungs- PULMONARY circulation

• Circulation of blood between the heart and the rest of the body- SYSTEMIC circulation

Circulatory System

BLOOD VESSELS

Blood Vessels: Pathway of Circulation

• 3 types of vessels– Arteries– Capillaries– Veins

Arteries:carry blood Away from heart

– Large– Thick-walled, Muscular– Elastic– Oxygenated blood

• Exception -Pulmonary Artery

– Carried under great pressure

– Steady pulsating

Capillary

Connective tissue

Connective tissue

Smooth muscle

Smooth muscle

Endothelium

Endothelium

Valve

Venule

Endothelium

Arteriole VeinArtery

Capillaries - Smallest vessels

– Microscopic– Walls one cell thick– Nutrients and gases diffuse here

Veins:Carry blood to heart

– Carry blood that contains waste and CO2

• Exception -pulmonary vein

– Blood not under much pressure

– Valves to prevent much gravity pull

Circulatory System

BLOOD

The Blood

• Body contains 4-6 L• Consists of

– Water– Red Blood Cells– Plasma– White blood cells and

platelets

Whole Blood Sample

Red blood cells

White blood cells

Platelets

Plasma

Sample Placed in Centrifuge Blood Sample That Has Been Centrifuged

Parts of the Blood

Blood: Fluid Transport

Liquid Portion Carries • Blood cells

– red blood cells– white blood cells

• Platelets (non cellular particles)• Proteins

– Enzymes – Hormones – Endocrine System

• Nutrients - Digestive System• Gases - Respiratory System• Inorganic salts

Carbon Dioxide in the Blood

• CO2 is a waste product of cellular work

• 70% of CO2 combines with water

• The rest travels to the lungs

RBC• Transporters of

– Oxygen– Carbon Dioxide

• RBC– Lack a nucleus– Contain hemoglobin– Disk-shaped

• RBC are produced in red bone marrow of – ribs, – humerus, – femur, – sternum, and other long bones

• Lives for 120 days• Old RBC are destroyed in liver

and spleen

WBC

• WBC fight infection– Attack foreign

substances

• Less abundant• Large cells• Some live for

months– Most just a few days

• Several types• ALL contain nuclei

Platelets

• PLATELETS are for CLOTTING blood

• Cell fragments

• Produced in bone marrow

• Short life span (1 week)

• Fibrin (sticky network of protein fibers)– Form a web trapping blood cells

Blood Clotting

Break in Capillary Wall

Blood vessels injured.

Clumping of Platelets

Platelets clump at the site and release thromboplastin. Thromboplastin converts prothrombin into thrombin..

Clot Forms

Thrombin converts fibrinogen into fibrin, which causes a clot. The clot prevents further loss of blood..

Blood Types

• Massive loss of blood requires a transfusion

• Four Types– A– B– AB– O

• Inherited from your parents

Blood Pressure

• Blood against the blood vessel’s walls– The systolic pressure refers to

• the pressure recorded while the ventricles pump the blood.

– The diastolic pressure refers to • the pressure recorded as the ventricles fill with

blood.

• A normal blood pressure is 120/80

Disorders (cont)

• Hypertension– High blood pressure– Hearts works harder than necessary– Increases risk of heart attack or stroke

Disorders (cont)

• Heart Attack– Atherosclerosis in coronary artery– Heart muscle begins to die

• Symptoms– Nausea– Shortness of breath– Severe chest pain

IMMEDIATE MEDICAL ATTENTION NECESSARY

Disorders (cont)

• Stroke– Blood clot gets stuck in blood vessels leading

to brain– Brain cells die due to lack of oxygen

• Or blood vessel burst

– Can lead to paralysis, • loss of ability to speak• death

Current PREVENTION Recommendations

• Regular exercise• Weight control• Well balanced diet• Do not smoke• Diet low in saturated

fat