Transcript Chapter 23: Circulation

Chapter 23
CIRCULATION: CARDIOVASCULAR
SYSTEM
Functions of Cardiovascular System :
1. Transport and exchange of gases:
 Carries oxygen for aerobic respiration from lungs to
tissues.
 Picks up carbon dioxide from tissues and releases it in
lungs.
2. Transport nutrients (from digestive system to cells)
3. Transport hormones (from glands to target cells).
4. Transport metabolic waste (to excretory organs)
5. Defense against infection by pathogens.
6. Regulates water and ion balance.
7. Distribution of metabolic heat and maintenance of body
temperature.
Diffusion Between Blood and Tissue Cells
Cardiovascular System
System of internal transport
Components:
1. Blood (Fluid connective tissue)
2. Heart (Pumping device)
3. System of blood vessels:
 Arteries
and arterioles
 Veins and venules
 Capillaries
Cardiovascular Systems of Fish and Mammal
Fish: Single circuit
Two chamber heart
Mammal: Double circuit
Four chamber heart
Right side pumps O2 poor blood
Left side pumps O2 rich blood
1. Blood
Average Blood Volume: 4 to 6 liters.
Blood composition:
55% Plasma (fluid matrix of water, salts, proteins, etc.)
45% Cellular elements:

Red Blood Cells (RBCs): 5-6 million RBCs/ml of blood.
Contain hemoglobin which transport oxygen and CO2.

White Blood Cells (WBCs): 5,000-10,000 WBCs/ml of blood.
Play an essential role in immunity and defense. Include:
• Lymphocytes: T cells and B cells
• Macrophages (phagocytes)
• Granulocytes: Neutrophils, basophils, and eosinophils.

Platelets: Cellular fragments. 250,000- 400,000/ml of blood.
Important in blood clotting.
Composition of Human Blood
Red Blood Cells Contain Hemoglobin and
Transport Gases in Blood
Platelets are Essential for Blood Clotting
2. Heart
Anatomical Features:
 Hollow
muscular organ, about the size of a human fist.
 Weighs less than one pound (10 ounces).
 Rests on diaphragm, near middle of thoracic cavity.
 Wall is composed of cardiac muscle covered by
connective tissue.
Pericardium: Membrane that surrounds entire
heart and contains a fluid which protects heart
and decreases friction.
Position of Heart in Thoracic Cavity
2. Heart
Heart Chambers: Heart is divided into four
separate chambers. Both the left and the
right side of the heart have a(an):
 Atrium
(Plural atria): Smaller, superior
chambers. Receive blood from veins.
 Ventricle:
Larger, inferior chambers. Pump
blood into arteries.
Two sides of heart have different functions:
 Right
 Left
side: Pumps oxygen poor blood.
side: Pumps oxygen rich blood.
Structure of the Human Heart
Right side pumps O2 poor blood. Left side pumps O2 rich blood
Pacemaker (Sinoatrial node): Specialized structure
that sends electrical impulses that causes both
atria and ventricles to contract.
2. Heart
Heart Valves: Heart has several valves made of
connective tissue, that prevent backflow of blood
as it circulates.
 Atrioventricular (AV) Valves: Close between atria
and ventricles


Right AV Valve: Connects right atrium to the right ventricle.
Left AV Valve: Connects left atrium to the left ventricle.
Semilunar Valves: Close as blood leaves the
ventricles and enters the arteries.
Heart murmur: Rushing, gurgling sound created by
backflow of blood due to damaged or imperfect
heart valves. Fairly common (10% of healthy
population). Most are asymptomatic.

Internal Structure of the Human Heart
3. Blood Vessels
 Include
arteries, arterioles, capillaries, venules,
and veins.
 Double
circuit, closed system:
1. Pulmonary circuit: Delivers blood to lungs.
Oxygenation of blood.
2. Systemic circuit: Delivers oxygenated blood to
tissues and organs of body (brain, liver, heart,
kidneys, etc). Picks up carbon dioxide produced
by tissues.
Structure of Different Blood Vessels
Pulmonary and Systemic Circuits
3. Types of Blood Vessels
A. Arteries and Arterioles:
 Carry
 Have
blood away from heart to body.
high pressure.
 Have
thick muscular walls, which make them
elastic and contractile.
 Vasoconstriction: Arteries
contract:

Reducing flow of blood into capillaries.

Increasing blood pressure.
 Vasodilation: Arteries
relax:

Increasing blood flow into capillaries.

Decreasing blood pressure.
Control of Capillary Blood Flow by
Arteriole Constriction
3. Types of Blood Vessels
Capillaries: Only blood vessels whose walls are thin
enough to permit gas exchange.
Blood flows through capillaries relatively slowly,
allowing sufficient time for diffusion or active
transport of substances across walls.
Only about 5 to 10% of capillaries have blood
flowing through them. Only a few organs (brain
and heart) always carry full load of blood.
Blood flow to different organs is controlled by
precapillary sphincters of smooth muscle.
Control of Capillary Blood Flow by Precapillary Sphincters
Movement of Fluid Across Capillary Walls
99% of fluid that leaves capillary at arteriole end, reenters at
venous end. Remaining 1% is returned by lymphatic vessels.
3. Types of Blood Vessels
Veins and Venules:
 Collect
blood from all tissues and organs and
carry it back towards heart.
 Have
low pressure and thin walls.
 Veins
have small valves that prevent backflow of
blood towards capillaries, especially when
standing. If the valves cease to work properly,
may result in:

Varicose veins: Distended veins in thighs and legs.

Hemorroids: Distended veins and inflammation of the rectal and
anal areas.
Veins Contain Valves to Prevent Backflow of Blood
Heart Beat
 Average
70 beats per minute.
 100,000
beats every day.
 Cardiac
cycle about every 0.8 sec.

Diastole: Heart relaxes and blood flows into chambers (0.4 sec).

Systole: Heart contracts.
• First atria (0.1 sec)
• Then ventricles (0.3 sec)
 Pumps
about 8000 liters of blood/day.
 Pacemaker (Sinoatrial

node): Controls heart rate.
Regulated by nervous and endocrine systems.
 Two
heart beat sounds (“Lub-dupp”):

First sound: Ventricles contract, AV valves close.

Second sound: Heart relaxes, semilunar valves are closing.
 Pulse: Arteries
expand and contract with each heartbeat.
Stages of Cardiac Cycle
Diastole: Heart Relaxes
Second
Sound
“Dupp”
Systole: Heart contracts
First
Sound
“Lub”
Pacemaker Controls Cardiac Rhythm
Blood Pressure
 Pressure
is highest in arteries; lowest in veins.
 “Blood
pressure” usually refers to arterial pressure.
 Usually
measured at brachial artery in arm.
 Two
measurements:
 Systolic
Blood Pressure: During heart contraction.
Normal systolic pressure is about 120 mm Hg.
(Range: 110-140 mm Hg).
 Diastolic
Blood Pressure: During heart relaxation.
Normal diastolic pressure is about 80 mm Hg.
(Range: 70-90 mm Hg)
Measuring Systolic and Diastolic Blood Pressure
Blood Pressure and Velocity in Blood Vessels
Blood Pathway in Body
 Right
Side of Heart:
 Right
atrium receives oxygen poor blood from body.
 Right
ventricle pumps oxygen poor blood to lungs.
 Left
Side of Heart:
 Left
atrium receives oxygenated blood from lungs.
 Left
ventricle pumps oxygenated blood to body.
Blood Pathway:
Veins ---> Vena cava ---> Right atrium ---> Right ventricle --->
Pulmonary artery ---> Lungs ---> Left atrium ---> Left ventricle --->
Aorta ---> Arteries ---> Capillaries ---> Veins
Path of Blood Flow through Cardiovascular System
Cardiovascular Disease

Number one cause of death in the U.S. and
industrialized nations.

Includes hypertension, strokes, heart attacks, and
congestive heart failure.

Most often caused by complications of:
Arteriosclerosis: A condition in which arteries
become blocked by calcium and lipid deposits
(plaque), losing their elasticity.
Heart Attack (Myocardial infarction-MI)
 Sudden
decrease in blood supply to the heart, due to a clot
or plaque in arteries.
 Death
of cardiac muscle resulting in insufficient blood
supply to rest of body.
 Heart
may stop beating altogether or suffer permanent
damage.
 Over
1.3 million heart attacks every year in U.S.

Leading cause of death and disability

60% had no previous symptoms.

25% are not recognized when they occur.

25% die before receiving medical assistance.

In 1995 960,000 deaths in U.S.
Heart Attacks are Caused by Blocked
Coronary Arteries
Heart Attack (Myocardial infarction)
 Symptoms:
Chest pain, pressure, or tightness, sweating,
nausea, shortness of breath, dizziness, and fainting.
 Risk










factors:
Smoking
High blood pressure
High cholesterol
High LDLs (low density lipoproteins)
Diabetes
Male gender
Emotional stress
Obesity
Heredity
Sedentary lifestyle
Hypertension: High blood pressure.
 Blood
pressure over 140/90.
 Over
20% of U.S. population suffers from blood
pressures over 160/95.
 Another
25% is borderline (above 140/90).
 Heart
must work harder to overcome resistance.
 Silent
killer: May have few or no symptoms.
 May
result in strokes, heart attacks, aneurysms,
ischemia (insufficient blood supply to heart) and
arteriosclerosis.
 Risk
factors: Heredity, obesity, high salt intake, black
race (relative risk 2), smoking, stress, diet high in fat,
and lack of exercise.
Ischemic Heart Disease:
 Insufficient
 Especially
 May
blood supply to the heart.
during exercise or physical exertion.
cause angina pectoris: sharp chest pain.
Congestive Heart Failure:
 Heart
cannot pump enough blood to meet body’s
needs.
 Slow
blood flow causes veins to back up causing edema
in tissue (legs, tissues, or lungs).
 Symptoms:
 Causes:
Shortness of breath, edema, and fatigue.
Hypertension , arteriosclerosis, heart valve
damage, heart attack, etc.
Stroke:
 Third
leading cause of death in U.S. after heart disease
and cancer.
• 5% of people over 65 have had a stroke.
• 400,000 stroke victims discharged from hospitals every year.
 Insufficient
blood supply to the brain, caused by a
blood clot or rupture of a blood vessel.
 Depending
on area affected may cause:
• Paralysis (usually one side of body).
• Loss of sensation or motor control.
• Incontinence
• Loss of speech, hearing, or sight.
• Death
Relationship between major organ systems