The Cardiovascular System
Chapter #13
Human
Heart
13.1 Introduction
• The heart pump 7,000 liters of blood/day.
• Pumps 2.5 billion times in an average life span.
• The heart, arteries, veins, capillaries, and blood
make up the cardiovascular system.
• The main job of the cardiovascular system is to
deliver oxygen and nutrients to all body cells and
remove waste from all cells.
• Without fresh O2 and removing waste death
would be quick.
13.2 Structure of the Heart
• The heart is a hollow, cone-shaped, muscular
pump located within the thoracic cavity and
resting on the diaphragm. The upper most of the
heart is the BASE. The pointy end is the Apex.
• An average heart is about the size of your fist.
• The base of the heart lies beneath your 2nd rib.
• Pericardium is the covering of the heart.
• Pericardial cavity contains a small volume of fluid
that reduces friction the pericardium and the
heart itself.
13.2 Continued…
• The wall of the heart is made of 3 layers:
1. The outer pericardium which protects the
heart by reducing friction.
2. The thickest middle myocardium consist
mostly of muscle and pumps blood out of the
heart.
3. The inner endocardium consists of epithelium
and connective tissue that contains many
elastic and collagenous fibers. The
endocardium is continuous with the inner
linings of blood vessels attached to the heart.
13.2 Heart Chambers and Valves
• The heart is divided into 4 chambers.
• The upper chambers are the atria. Atria have
thin walls and receive blood returning to the
heart.
• The lower chambers are the ventricles. Ventricles
receive blood from the atria and contract to
force blood out of the heart into arteries.
Bicuspid valve
Tricuspid
• The septum separates the atrium and ventricle
on the right side from the left side. The blood
from the two sides NEVER mixes.
• An atrioventricular valve, the tricuspid on the
RIGHT side and the bicuspid (Mitral) on the
LEFT side ensure one-way blood flow from
atria to ventricle.
• Tricuspid has 3 cusps allows blood to move
from the right atrium into the right ventricle.
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•
Veins carry blood to the heart.
Arteries carry blood away from the heart. Aaway.
• The right atrium receives blood from two large
veins and 1 small.
1. Superior vena cava
2. Inferior vena cava
3. (Small) Coronary sinus drains blood into the
right atrium from the myocardium.
• Strong, fibrous strings called chordae tendineae
attach to the cusps of the tricuspid valve on the
ventricular side. They keep the cusps from
swinging back into the atrium.
• The right ventricle has a thinner muscular wall
than the left ventricle.
• The right chamber pumps blood a short
distance to the lungs.
• The left ventricle pumps blood to all other parts
of the body.
Valves
• The bicuspid and tricuspid valves are called
atrioventricular valves because they are between
atria and ventricles.
• The pulmonary and aortic valves are called
semilunar because of the half-moon shapes of
their cusps.
Skeleton of the Heart
• Rings of dense connective tissue surround the
pulmonary trunk and aorta and dense masses of
connective tissue make up the Skeleton of the
Heart.
• These rings provide firm attachments for heart
valves and for muscle fibers.
• They prevent the outlets of the atria and
ventricles from dilating during contraction.
Path of Blood
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Vena cava (Largest vein in the body)
Right atrium (Right side deoxygenated blood)
Tricuspid value
Right ventricle
Pulmonary artery
Right and left lung (Picks up O2 & drops off CO2)
Pulmonary vein
Left atrium (Left side oxygenated blood)
Bicuspid value
Left ventricle
Aorta (Largest artery in the body)
To all body cells
Blood Supply to the Heart
• Coronary vessels carry blood to and from the
heart itself.
• Heart attack is the death of a section of heart
muscle.
Heart Actions
• Systole atria contract and ventricles relaxed.
• Diastole atria relaxed and ventricles contract.
• Both atria contract while both ventricles relax
and them both ventricles contract as both atria
relax.
Heart Sounds
• A heartbeat heard through a stethoscope sounds like
lubb-dupp.
• The sound is caused by the closing of valves.
• Lubb when bicuspid and tricuspid valves close.
• Dupp when semilunar valves close.
• A heart murmur blood flowing backward through the
heart when valves are not closing tightly.
• Lubb-dupp-swish would signal a problem with the
semilunar valve.
• Lubb-swish-dupp= problem with bicuspid and/or
tricuspid valve.
Cardiac Muscle Fibers
• Cardiac muscle fibers function much like those
of skeletal muscles. The heart pumps as one
unit.
• Functional syncytium is a mass of merged cells
that function as a unit.
• Sinoatrial node (S-A node) is a small, elongated
mass of specialized cardiac muscle tissue just
beneath the epicardium in the right atrium.
• S-A node are the cells that initiate the stimulus
for contraction of the heart muscle.
• Electrocardiogram (ECG)is the recording of the
electrical charges that occur in the myocardium
during a cardiac cycle.
• Blood volume of changes to accommodate
cellular requirements. Example during strenous
exercise, skeletal muscles require more blood.
• The cardiac control center is in the brains
medulla oblongata.
• The ions that influence the heart the most are
potassium (K+) and Calcium (Ca+2).
• Excess potassium ions (hyperkalemia) decrease
the rate and force of contractions.
• Low potassium ions (hypokalemia) the heart
may develop a potentially life-threatening
abnormal rhythm (arrhythmia).
• Excess calcium ions (hypercalcemia) increase
heart actions, posing the danger that the heart
will contract for a prolonged time.
• Low calcium ions (hypocalcemia) depresses
heart action.
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13.4 Blood Vessels
Arteries
They carry blood away from the heart
They carry blood under high pressure
They are round in shape
They have thick, muscular walls
Arterioles are arteries that have divide and divide
into progressively thinner tubes.
 Vasoconstriction when arteries contract.
 Vasodilation when arteries dilate.
Veins
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1.
2.
3.
4.
Veins
They carry blood to the heart
They carry blood under low pressure
They are flat in shape and have little muscle
They have many one-way valves to keep blood
flowing in one direction.
96 000
kilometers of
blood vessels in
the human body.
2 ½ times
around the earth.
13.5 Blood Pressure
• Blood pressure is the force of blood exerts
against the inner walls of blood vessels.
• Blood pressure is most commonly refers to
pressure in arteries.
• Pulse is the force of blood through an artery.
• Blood pressure is recorded as a fraction. Systolic
over diastolic.
• Systolic pressure is the maximum pressure
during ventricular contraction.
• Diastolic pressure is the lowest pressure that
remains in the arteries before the next
contraction (ventricular relaxation).
Heart Action
• Stroke Volume the volume of blood discharged
from the left ventricle with each contraction.
• Cardiac output the volume discharged from the
left ventricle per minute. Can be calculated by
multiplying the stroke volume by the beats per
minute.
• Blood volume equals the sum of the formed
elements and plasma volumes in the vascular
system. (It is usually about 5 liters for adults)
• Peripheral resistance is the friction between the
blood and the walls of blood vessels.
• Blood viscosity is the ease with which a fluid
flows. The greater the viscosity, the greater the
viscosity.
• Starling’s law of the heart is the relationship
between fiber length ( due to the stretching of
the cardiac muscle cell just before contraction)
and the force of contraction. Sooooo the more
blood that enters the heart the stronger in
contracts. This ensures that the volume of blood
discharged from the heart is = to the volume
entering its chambers.
Hypertension
• High blood pressure
• One of the more common diseases of the
cardiovascular system.
• Hypertension can be caused by kidney disease,
high sodium intake, obesity, psychological stress,
and arteriosclerosis.
• Arteriosclerosis decreases the elasticity of
arterial walls and narrows openings increases
blood pressure.
Hypertension Cont….
• If hypertension is left untreated it can cause
atherosclerosis or plaque accumulation in
arteries that can lead to a stroke.
• Plaque are deposits of fatty materials on the
inside of the arterial walls.
• Hypertension can be treated with regular
exercise, controlling body weight, reducing
stress, and limiting sodium in the diet.
13.6 Paths of Circulation
• Pulmonary circuit consists of vessels that carry
blood from the heart to the lungs and back to
the heart.
• Systemic circuit carries blood from the heart to
all other parts of the body and back to the heart.
Pulmonary Circuit
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Right ventricle
Right and left pulmonary arteries
Right and left lungs
Arterioles into the alveoli (gas exchange)
Pulmonary viens
Left atrium
Systemic Circuit
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Left atrium
Left ventricle
Aorta
Head and body (deliver O2 and pick up CO2)
Veins
Right atrium
13.7 Arterial System
• Jugular veins drain blood from the face, scalp,
and superficial regions of the neck.
• Femoral artery located in the upper thigh supply
blood to the tissue of the thigh, skin of the
groin and the lower abdominal wall.