BIOLOGY OF HUMAN AGING
CHAPTER 9
The Circulatory 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
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)

White Blood Cells (WBCs) Play an essential role in immunity
and defense. Include:
• Lymphocytes: T cells and B cells
• Macrophages (phagocytes)
• Other types of WBCs

Platelets: Cellular fragments. Important in 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.
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.
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.
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.
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.
 Pacemaker (Sinoatrial

node): Controls heart rate.
Regulated by nervous and endocrine systems.
 Pulse: Arteries
expand and contract with each heartbeat.
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 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
Age-related changes
Blood
Total protein concentration decreases with aging
The amount of red bone marrow diminishes with aging replac
by yellow bone marrow
Heart
Decrease vs. increase in heart size
increase of fat deposits
Accumulation of lipofuscin pigment in cardiac muscle cells
Endocardium tends to become thicker due to deposition of fat
Scleroses (hard white patches may form
Systolic and diastolic blood pressures tend to increase with aging
Decrease in maximum oxygen consumption with aging
Cardiac output decreases with aging
(the volume of blood pumped/min by either ventricles)
Age-related changes
Blood Vessels
 Reduction in elasticity. Reduction in ability to
stretch.
 Reduction in elastin. Increase in collageneous
CT.
 Tendency to bind with Ca and calcification of
elastin.
 Gradual accumulation of lipids
 Increase in LDLs. Role of HDLs. Increase in
systolic blood pressure with aging.

Age-related Dysfunction
Atherosclerosis and Arteriosclerosis
Hypertension
Coronary Artery Disease
Myocardial Infarction
Angina Pectoris
Cardiac Arrhythmias
Congestive Heart Failure
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