Download AHS CVS Lecture 1

THE CARDIOVASCULAR SYSTEM
LECTURE 1:
INTRODUCTION
Eamonn O’Connor
Applied Health Science
Lecture Outline
1
 
 
 
Overview of the Cardiovascular System
The Path of Blood Flow Through the Heart
and Vasculature
Anatomy of the Heart
AHS Physiology - Cardiovascular System 11-12
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Overview of the Cardiovascular System
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AHS Physiology - Cardiovascular System 11-12
Overview of Cardiovascular System
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 
Functions of CV system:
  Transport
of substances
  Oxygen
& nutrients to cells
  Wastes from cells to liver & kidneys
  Hormones, immune cells, clotting proteins
to specific target cells
  Regulation of Cardiovascular system: interactions with
nervous system, endocrine system and kidneys
AHS Physiology - Cardiovascular System 11-12
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The Heart
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 
Four chambers
  2
Atria: receive venous
blood
  2 Ventricles: pump blood to
the circulation
 
Septum: prevent mixture of
blood from both sides (left
and right)
  Interatrial
  Interventricular
 
 
Base: upper end
Apex: lower end
Figure 13.1
AHS Physiology - Cardiovascular System 11-12
Blood Vessels
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Heart →Arteries → Arterioles → Capillaries → Venules → Veins
 
Vasculature
  Arteries
– relatively large, branching vessels that conduct
blood away from the heart
  Arterioles – small branching vessels with high resistance
  Capillaries – site of exchange between blood
and tissue
  Venules – small converging vessels
  Veins – relatively large converging vessels that conduct
blood to the heart
  Closed system
AHS Physiology - Cardiovascular System 11-12
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Blood
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Arterial Blood
Blood leaving the heart
Bright Red
High oxygen content
(oxyhaemoglobin)
Venous blood
Blood returning to the heart
Darker colour
Lower oxygen content
(deoxyhaemoglobin)
Cellular portion of blood (45% blood volume)
a) Erythrocytes (red blood cells): oxygen transport
b) Leukocytes (white blood cells): immune function
c) Platelets: Blood clotting
Plasma (55% blood volume)
a) Water (90%)
b) Dissolved solutes eg. Ions, O2, CO2…
c) Plasma proteins
d) Other components eg. metabolites, hormones, enzymes, antibodies.
Figure 15.1
AHS Physiology - Cardiovascular System 11-12
Path of Blood Flow through CVS
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 
Pulmonary circuit
  Supplied
by right heart
  Blood vessels from heart to lungs and
lungs to heart
 
Systemic circuit
  Supplied
by left heart (rest of blood
vessels)
  Blood vessels from heart to systemic
tissues and tissues to heart
Figure 13.2
AHS Physiology - Cardiovascular System 11-12
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Oxygenation of Blood
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 
Exchange between blood and tissue
takes place in capillaries
  Pulmonary
capillaries
  Blood
entering lungs = deoxygenated blood
  Oxygen diffuses from tissue to blood
  Blood leaving lungs = oxygenated blood
  Systemic
capillaries
  Blood
entering tissues = oxygenated blood
  Oxygen diffuses from blood to tissue
  Blood leaving tissues = deoxygenated blood
Figure 13.2
AHS Physiology - Cardiovascular System 11-12
Path of Blood Flow Through the CVS
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 
Cardiovascular system = closed system
  Flow
through systemic and pulmonary
circuits are in series (has to go through
both circuits and simultaneously)
 
Left ventricle  aorta  systemic
circuit  vena cavae  right atrium
 right ventricle  pulmonary artery
 pulmonary circuit  pulmonary
veins  left atrium  left ventricle
AHS Physiology - Cardiovascular System 11-12
Figure 13.2
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10
 
Parallel Blood Flow Within the Systemic
(or Pulmonary) Circuit
Aorta  arteries  arterioles 
capillaries
  Oxygenated
blood enters each capillary
bed
  Parallel flow allows independent
regulation of blood flow to organs
 
Capillaries  venules  veins
  Exception:
portal systems (i.e. kidneys, GI
tract-liver)
Figure 13.3
AHS Physiology - Cardiovascular System 11-12
Anatomy of the Heart: Location
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Located in thoracic cavity
  Diaphragm separates
abdominal & thoracic
cavities
  Size of a fist
  Weight approx
250-350g
 
AHS Physiology - Cardiovascular System 11-12
Figure 13.5
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Pericardium
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 
Membranous sac surrounding heart
 
Lubricates heart decreasing friction
 
Pericarditis = inflammation of pericardium
AHS Physiology - Cardiovascular System 11-12
Myocardium & the Heart Wall
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 
Three layers of the heart wall:
  Endocardium
  layer
(inner)
of endothelial cells
  Myocardium
  cardiac
(middle)
muscle
  Epicardium
  external
(outer)
membrane, connective tissue
AHS Physiology - Cardiovascular System 11-12
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Properties of Cardiac Muscle
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 
 
 
Smaller fibres than skeletal muscle
Sarcomeres: Striated
Intercalated Disks
 
 
 
Gap junctions: Contract as unit
Desmosomes: Resist stress
Atria & Ventricles: Separate units (separated by fibrous skeleton)
 
 
Aerobic muscle
99% contractile cells / 1% autorhythmic cells
Figure 12.32c
AHS Physiology - Cardiovascular System 11-12
Walls of the Heart
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 
Walls of ventricles thicker than walls of atria
  Wall
of left ventricle thicker than wall of right
Figure 13.1
Figure 13.6
AHS Physiology - Cardiovascular System 11-12
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Function of Cardiac Muscle
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 
Rhythmic contraction and relaxation generates heart
pumping action
  Contraction
increases the pressure within the chamber
and pushes blood out of heart into vasculature
  Relaxation allows heart to fill with blood
 
Heartbeat:
  Wave
of contraction through cardiac muscle
  Atria contract as a unit
  Ventricles contract as a unit
  Atrial contraction precedes ventricle contraction
AHS Physiology - Cardiovascular System 11-12
Valves and Unidirectional Blood Flow
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 
Pressure within chambers of heart vary with
heartbeat cycle
  Pressure
  High
 
difference drives blood flow
pressure to low pressure
Normal direction of flow
  Atria
to ventricles
  Ventricles to arteries
 
Valves prevent backward flow of blood
  All
valves open passively based on pressure gradient
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Heart Valves: atrioventricular valves
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 
AV valves:
  Right
AV valve = tricuspid
valve (3 flaps or cusps)
  Left AV valve = bicuspid
valve = mitral valve
  Papillary muscles and
chordae tendinae: keep AV
valves from everting
AHS Physiology - Cardiovascular System 11-12
Figure 13.7
Semilunar Valves
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 
Semilunar valves:
  Aortic
valve (L)
  Pulmonary valve (R)
AHS Physiology - Cardiovascular System 11-12
Figure 13.8
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