Transcript 9) Circulatory System - Cal State LA

BIOLOGY OF HUMAN AGING
CHAPTER 9
The Circulatory System
Outline
1. Review of Structure and Function
•
Blood, Heart, Blood Vessels, Lymphatic System
2. Age-related Changes
•
Blood, Heart, Blood Vessels
3. Age-related Dysfunctions
•
Atherosclerosis
•
Arteriosclerosis
•
Hypertension
•
Coronary Artery Disease
•
Myocardial Infarction
•
Angina Pectoris
•
Cardiac Arrhythmia
•
Congestive Heart Failure
Introduction
Survival, growth and proper functioning of the cells need a
constant supply of nutrients & O2, & efficient disposal of
waste (metabolic byproducts)
Compositions of the circulatory system provide these needs
Diseases of heart & blood vessels: major cause of death in US
Two top causes of death, heart disease & stroke, associated w/
dysfunctions of circulatory system
9% of total population die from heart/blood vessel disease,
survivors have varying degrees of disabilities, high-cost care

Circulatory System:
Cardiovascular: heart and blood vessels; Rhythmic heart contractions 
force  propel blood through vessels

Lymphatic System: lymphatic vessels; collects tissue fluid from intercellular
space, carry to cardiovascular system and lymphoid organs that filter the
lymph & participate in immune response (organs: tonsils, thymus, spleen,
lymph nodes and nodules).

Cardiovascular system is a closed system (hear chambers & blood vessels)
forms a circular path throughout the body

Blood is confined w/in the heart & vessels and repeatedly travels through the
heart into arteries and arterioles then through capillaries into venules and
veins, then back to heart

Under physiological conditions, blood won’t leave the vessels, though
plasma passes through capillary walls (tissue fluid) but re-enters capillaries
or enters lymphatic system  back to 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
4. Lymphatic system
Mammalian Cardiovascular System
Double circuit
Four chamber heart
Right side pumps O2 poor blood
Left side pumps O2 rich blood
Blood:
fluid component of the circulatory system, transports substances to &
from the body cells. Average Blood Volume: 4 to 6 liters.
Blood composition:
55% Plasma (fluid matrix composed mostly of water, salts, proteins,
lipids, gases, ions, metabolic end products)
45% Cellular (formed) elements:

Red Blood Cells (RBCs): O2 transport (hemoglobin)

White Blood Cells (WBCs): Play an essential role in immunity and
defense. Include:

Lymphocytes: T cells & B cells (killing and Ab secretion)

Macrophages (phagocytes)

Other types of WBCs (monocyte, neutrophil, basophil, eosinophil)

Platelets: Cellular fragments. Important in blood clotting (prevent
hemorrhages).

Blood cells are formed from precursor cells in red BM.
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 one:
 Atrium
(Plural atria): Smaller, superior chambers.
Receives blood from veins.
 Ventricle:
Larger, inferior chambers. Pumps 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
Sympathetic nervous system increase rate of heart contraction, parasympathetic nervous system decreases heart rate.
Impulses are generated by specialized cell masses
 Pacemaker (Sinuatrial (SA) node): Specialized structure located in
right atrium that sends electrical impulses that causes both atria and
ventricles to contract.
Stimulatory impulses from SA node also depolarize AV node (located in
interatrial septum)
AV node cells like SA depolarize
Spontaneously
SA node 70 times/minute
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.
Pulmonary and Systemic Circuits
3. Types of Blood Vessels
A. Arteries and Arterioles:

Carry blood away from heart to body.

Have 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.
Structure of Different Blood Vessels
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 Pathways 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
4. Lymphatic System

Consists of extensive network of vessels, lymph nodes, lymphoid organs

Means by which tissue fluid is collected from intracellular space, filtered,
transported to cardiovascular system

Excess fluid that moves to tissue space (tissue fluid) is source of lymph

Accumulation of tissue fluid  swelling  pressure and pain

Fluid passes through thin walled lymphatic capillaries  lymphatic system

Lymphatic capillaries  progressively larger vessels (travel alongside
arteries and veins)  lymph nodes  thoracic duct or right lymphatic duct

Both ducts empty into veins, thus lymphatic system returns excess
tissue fluid back to blood stream

Function:

Pick up foreign material (antigen, microorganisms)  lymph node

Role of phagocytes

Plasma cells, antibody
Age-related changes
A. Blood
 Total protein concentration decreases with aging
 The amount of red bone marrow diminishes with aging replaced
by yellow bone marrow
B. 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
C. Blood Vessels









Reduction in elasticity.
Reduction in ability to stretch.
Reduction in elastin.
Increase in collageneous CT (connective tissue).
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
Presence of plaques (degenerative changes) in inner surface of walls of
arteries (ATHEROSCLEROSIS)
Plaques: connective tissue, lipids, abnormal smooth muscle cells, high LDL

Slowly narrow & completely block vessel & restrict blood flow to the region

Plaques are rough, cause blot clot, cause coronary artery disease

Responsible for more death/year than all kinds of cancers combined

In advanced cases, plaques harden by Ca deposition & fibrous tissue
proliferation  hardening of arteries of Arteriosclerosis

Greatly reduce blood vessel elasticity, less able to expand & recoil in
response to BP changes (contraction & relaxation)

Weakened areas of vessel dilate  aneurysm (rupture in high BP)

Contributing Factors:

LDL & HDL

Smoking & drinking coffee raise cholesterol levels

Role of diet: less than 300 mg/day, average diet in US: 450-600
mg/day

Role of reducing cholesterol in diet & maintaining regular aerobic
exercise
Hypertension

High blood pressure, not restricted to older people

30% of population in industrialized countries suffer high BP by 65

High BP contribute to heart attack, heart failure, kidney damage,
rupture of blood vessels

Pressures above 170/90 are considered hypertensive

Most common cause of hypertension in older people:
a)
Atherosclerosis: decrease blood vessel diameter
b)
Arteriosclerosis: decrease elasticity

Heart must contract harder to maintain blood flow, additional
imposed workload  high BP & eventually heart failure

Also, excessive dietary sodium intake or retention

Elevated BP usually lowered or maintained by proper medication

High BP is not automatic body response to aging, mainly lifestyle
contributes to development (obesity, lack of exercise, smoking,
salt)
Coronary Artery Disease

Due to insufficient blood flow through the coronary arteries

Inadequate blood supply to tissue: ischemia (ishemic heart disease)

Interferes w/ contractions  severe cases  degenerate

Reduced blood flow due to narrowing or constriction of coronary
arteries

It is progressive: incidence increases w/ age

Major cause of heart problems & death in older persons

Most frequent cause: plaques that develop in lining of blood vessel

Cholesterol high in postmenopausal women  partial or complete
block

Thrombus: Enlarge plaques, protrude vessel, direct contact w/
flowing blood. Plaque surface is roughened, platelets adhere  form
fibers  blood cells entrapped  local blood clot (Thrombus)
narrows blood vessel lumen

Danger: blood clot breaks away, travel to smaller peripheral branches of
coronary  complete block  deprive regions of heart supplied by artery

Blood clot that travels in vessel to a new region is called embolus

Symptoms are referred to as heart attack (may be due to local spasm)

Amount of damage: determined by the extend of development of vessels
that bypass the blocked region which provide collateral circulation

Collateral vessels may help a person recover from episodes of coronary
artery blockage

Treatment: Bypass Surgery

Graft a portion of any artery to coronary artery to direct blood around block

Chemical injection (urokinase, streptokinase); dissolve clot  catheter (w/ a
balloon)  inflate balloon  compress the clot  open the vessel (balloon
angiography)

Laser beams transmitted through fine glass fibers
Blocked Coronary Arteries cause heart attack
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
Angina Pectoris

Short episodes of cardiac pain that result from chronic
restriction of coronary artery

Dull, pressing, constricting pain, appear on strenuous work

Examples: exercise or emotions that accelerate heart rate

Pain located deep in the center of chest, sometimes surface of
body (left arm, shoulder, neck, side of face)

Incidence reduced with age (reduced physical activity in older &
more extensive collateral circulation)

Treatment:

Drugs that dilate the artery (nitroglycerin)

Block receptors that stimulate sympathetic nervous system
(beta blockers)
Cardiac Arrhythmias
Heart normally contacts in a regular manner  predictable
sequence of heartbeats

Cardiac Arrhythmias: irregular beats outside the normal
sequence

Can occur at any age, more common in older people

Not all cases of irregular heartbeats are pathological

Result from extra systole (atrium or ventricle contracts more
often that it should) or from delayed heartbeats

Normal: 70 beats per minute
Congestive Heart Failure

Heart unable to pump blood to meet bodily requirements

Also referred to as cardiac insufficiency

Causes:

Muscular damage (due to heart attack)

Valvular diseases (interfere w/ blood movement)

Prolonged high blood pressure (BP)

Kidney is profoundly affected

Decreased urine production

Increase tissue fluid and blood volume

Dilated veins and capillaries  congested heart  hypertrophy
heart (increase in size)
Symptoms

Depend on which chamber involved: Ex: left ventricle failing  R
continues to pump into pulmonary vessels, yet, return from lung
inefficient (reduced cardiac output)

In failing L ventricle, blood backs up, elevates pressure in lung
capillaries  fluid forced out  pulmonary congestion “EDEMA”
(shortness of breath, difficulty breathing, especially while lying down)

Over time R side will also fail (compensatory mechanisms work initially)

No favorable prognosis, drugs can increase contractile strength of
cardiac muscle, eliminate excess fluid.

Surgical repair of defective valves or other structures can reduce
severity