Circulatory System

Unit 6.8 (6th Edition)

Chapter 7.8 (7th Edition)1

Learning Objectives

• Label the layers, chambers, valves, and

major blood vessels of the heart.

• Differentiate between systole and diastole.

• Trace the path of blood, O2, & CO2 during cardiac cycle.

• Explain the conductive pathway of electrical impulses.

• Identify abnormal heart rhythms (arrhythmias)

• Distinguish between the 3 major types of blood vessels.

• Compare/contrast the three main types of blood cells by

describing the function of each.

• Describe the major diseases of the circulatory system.

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Fun Facts About the Circulatory System

• The heart beats ~ 2.5 billion times in an average life span.

• ~ 8 million blood cells die in human body each second.

• ~ 8 million blood cells are born each second.

• A tiny droplet of blood has ~ 5 million red blood cells.

• It takes ~ 20 seconds for a red blood cell to circle the body.

• Red blood cells make ~ 250,000 round trips of the body

before returning to the bone marrow, where they were

born, to die.

• Red blood cells may live for ~ 4 months circulating

throughout the body, feeding the 60 trillion other cells.

• Though weighing only 11 ounces on average, a healthy

heart pumps 2,000 gallons of blood through 60,000

miles of blood vessels each day.

• Adult body has 4-6 quarts of blood in circulation. 3

Overview of Circulatory System

• Also Known as Cardiovascular System

• “Transportation” System

– transports O2 & nutrients

to body cells

– carries CO2 & metabolic

materials away from cells

• Consists of heart, vessels, & blood

• Heart

– Muscular, hollow organ that is

“pump” of body

– approximately size of fist

– sits between lungs, behind

sternum, above diaphragm 4

Layers of the Heart• Endocardium

– smooth layer of cells that line inside of the heart

– continuous with the inside of blood vessels

– allows for the smooth flow of blood

• Myocardium

– thickest layer of heart

– muscular middle layer

• Pericardium

– double-layered membrane sac that covers outside

– lubricating fluid fills space between the two layers to

prevent friction/damage as heart beats or contracts5

Four Chambers of the Heart

• Septum

– muscular wall

– divides heart into left & right

– prevents blood from moving

between left & right side

• Atrium (plural-atria)

– Latin word “entrance hall”

– two upper chambers

– Left & Right Atria

• Ventricles

– Latin word “little belly”

– two lower chambers

– Left and Right Ventricles6

Valves of the Heart

• Purpose

– one-way valves in heart chambers

– keep blood flowing in one direction

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Valve Functions• Tricupsid Valve

– closes when right ventricle contracts

– allows blood to flow to lungs

– prevents blood from flowing back into right atrium

• Pulmonary Valve

– carries blood to the lungs

– closes when the right ventricle has finished contracting

– prevents blood from flowing back into right ventricle

• Mitral Valve

– closes when the left ventricle contracts

– allows blood to flow into aorta for transport to body

– prevents blood from flowing back into left atrium

• Aortic Valve

– closes when left ventricle is finished contracting

– allows blood to flow into aorta

– prevents blood from flowing back into left ventricle 8

Blood Circulation

• Cardiopulmonary Circulation

– from heart to lungs and

– from lungs to heart

• Systemic (General) Circulation

– carry blood through rest of

body

• Blood Vessels

– carry blood leaving heart

– arteries carry blood away

from heart

– veins carry blood to heart9

How the Heart Works

10

• You Tube Video– http://www.youtube.com/watch?v=84PrHxJri9Q

Cardiac (Heartbeat) Cycle

• Diastole (Rest)

• Systole (Ventricular Contraction)

• How Does the Cycle Work?

– atria contract

– this pushes blood into ventricles

– atria then relax (diastole)

– blood returning from body enters right atrium

– blood returning from lungs enters the left atrium

– as atria fill, (systole begins), ventricles contract

– right ventricle pushes blood into pulmonary artery

– this sends blood to lungs for oxygen collection

– left ventricle pushes blood into aorta

– this sends blood to all other parts of the body11

Tracing O2 and CO2 in Blood

• Blood in right side of heart

is low in O2 & high in CO2

• When this O2 depleted

blood arrives in lungs, CO2

is released into lungs, and

• O2 is taken into the blood

• Oxygenated blood is

carried to left side of

heart by pulmonary veins

• This blood in left side of

heart is now high in O2

and low in CO2

• It is therefore ready for

transport to the body cells12

Illustrated Cardiac Cycle

13

Conductive Pathway• Electrical Impulses

– originate in heart

– cause cyclic contraction of muscles

– cycle occurs every 0.8 seconds

– recorded on an electrocardiogram (ECG)

• Sinoatrial (SA) Node

– pacemaker

– group of nerve cells located in right atrium

– sends out electrical impulse

– spreads over muscles in atria

– atrial muscles contract and push blood into ventricles

• Atrioventricular (AV) Node

– group of nerve cells located between atria and ventricles

– sends electrical impulse through “bundle of His,” (septum nerve

fibers)

– bundle of His divides into right and left bundle branches

– impulse is carried down through ventricles 14

Arrhythmias• Definition

– abnormal heart rhythms

– interference to natural heart rhythms

– can be mild to life-threatening

• Premature Atrial Contraction (PAC)

– early contraction of atria

– usually goes unnoticed

• Ventricle Fibrillation

– ventricles contract at random without coordination

– decreases blood output and causes death if untreated

• Diagnosis

– cardiac monitors

– electrocardiograms

• Treatment

– defibrillator: device that shocks the heart with electrical current

– stops uncoordinated contraction & SA node regains control

– pacemakers: monitors and delivers electrical impulses 15

Blood Vessels• Arteries

– carry blood away from heart

– aorta is largest artery in body & receives blood from left ventricle

– immediately branches into smaller arteries, then arterioles

– arteries are more muscular and elastic than other vessels

• Capillaries

– connect arterioles with venules (smallest veins)

– have thin walls of one layer of cells

– thin walls allow oxygen and nutrients to pass through to cells

– allow CO2 and metabolic products from cells to enter capillaries

• Veins

– blood vessels that carry blood back to heart

– venules join together to form veins until they form two largest

veins (superior and inferior vena cava)

– contain valves to prevent blood from flowing backwards

– thinner and less muscle than arteries16

Major Arteries and Veins

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Blood Composition• What is Blood?

– often called a tissue because it contains many kinds of cells

– 4-6 quarts of blood in average adult

– made of a fluid called plasma and solid blood cells (3 types)

– plasma is 90% water with many dissolved and suspended substances

• What Else is in Blood?

– blood proteins and clotting agents

– nutrients: vitamins, minerals, carbohydrates

– eletrotrolytes: potassium, calcium, and sodium ions

– gases: carbon dioxide, oxygen, and nitrogen

– metabolic and waste products

– hormones and enzymes

– diseases (such as malaria parasite shown at right)

• Blood Transports

– oxygen from lungs to body cells

– carbon dioxide from body cells to lungs

– nutrients from digestive tract to body cells

– metabolic and waste products from body cells to excretion organs

– heat produced by body parts

– hormones produced by endocrine glands to body organs 18

Three Blood Cell Types

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Red Blood Cells (Erythrocytes)

• Produced in red bone marrow at rate of 1 million/min.

• Live 120 days

• Broken down by liver and spleen

• 25 trillion in the body at any one time

• Mature form circulating in blood lacks

a nucleus

• Shaped like a a disc

• Thinner central area

• Contain hemoglobin (protein) that carries

O2 and CO2

• hemoglobin carrying oxygen gives blood red color

• blood containing less oxygen is bluish in color

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White Blood Cells (Leukocytes)• Not as numerous as RBC

• Formed in bone marrow and lymph tissue

• Live for 3-9 days

• 5,000 – 10,000 is normal count per mm3 of blood

• Can pass through capillary walls and enter body tissue

• Main function is to fight infection

• Phagocytosis: process in which WBC engulf, ingest, and

destroy pathogens (germs)

• 5 types of WBC

– neutrophils

– eosinophils

– basophils

– monocytes

– lymphocytes 21

Platelets (Thrombocytes)

• Pieces of cells

• Shown in middle at right

• Lack nuclei

• Vary in shape and size

• Formed in bone marrow

• Live for 5-9 days

• Normal count is 250,000 – 400,000 per mm3 of blood

• Important for clotting process (stop bleeding)

• Collect at sight of cut and form a sticky plug

• Secrete serotonin that causes blood vessel to spasm and

narrow (decreasing blood flow)

• Release enzyme that forms net-like fiber/clot22

Diseases & Abnormalities• Anemia

– inadequate number of RBC, hemoglobin, or both

– types: iron deficiency, aplastic, pernicious, and sickle cell

• Aneurysm

– ballooning out of, or saclike formation of artery wall

• Arteriosclerosis

– hardening or thickening of arterial walls (result of aging)

– causes high blood pressure (hypertension)

• Atherosclerosis

– fatty plaques (often cholesterol) deposit on

artery walls

• Congestive Heart Failure (CHF)

– heart muscles do not beat adequately to supply blood

• Embolus

– foreign substance in bloodstream 23

Diseases & Abnormalities Continued• Hemophilia

– inherited disease common in males

– blood is not able to clot (missing plasma protein)

• Hypertension

– high blood pressure (above 140 / 90 mm Hg)

• Leukemia

– malignant disease of bone marrow or lymph tissue

– results in high number of immature WBC

• Myocardial Infraction

– heart attack

– caused by blockage in coronary arteries

– cuts off supply of blood to heart

• Phlebitis

– inflammation of vein, frequently in legs

• Varicose Veins

– swollen, dilated veins that have lost elasticity24