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Chapter 5
Cardiovascular System:
Heart and Blood Vessels
Mader, Sylvia S. Human Biology. 13th Edition. McGraw-Hill, 2014.
Points to Ponder
• What are the functions of the cardiovascular
system?
• What is the anatomy of the heart and blood vessels
(veins and arteries)?
• How is the heart beat regulated?
• What is blood pressure?
• What are common cardiovascular diseases and
how might you prevent them?
Cardiovascular system
• Includes heart and blood
vessels
• Brings nutrients to cells that
are bathed by tissue fluid
and helps get rid of wastes
– Exchanges with tissue fluid and
not directly with cells
• Blood is refreshed in
– Lungs: gas exchange
– Kidneys: water and salt
retained, waste excreted
– Intestine: nutrient intake
– Liver: amino acid uptake and
remove toxin
• Lymphatic vessels help this
system by collecting excess
fluid surrounding tissues and
return it to the cardiovascular
system
5.1 Overview of the cardiovascular system
What are the function of the
cardiovascular system?
1. Generate blood pressure via heart
contractions
2. Transport blood via blood vessels
3. Exchange of nutrients and wastes at the
capillaries refreshes blood and tissue fluid
4. Regulate blood flow as needed
5.2 The types of blood vessels
What is the main pathway of blood in
the body?
• Heart – arteries – arterioles – capillaries venules – veins – back to the heart…
5.2 The types of blood vessels
Arteries and arterioles:
• Carry blood away from the heart
• Their walls have 3 layers:
– Thin inner epithelium
– Thick smooth muscle layer
– Outer connective tissue
• elastic tissue to absorb pressure
• Strong walls support vessel when blood enters
under pressure
• Arterioles are small arteries that regulate blood
pressure
– Muscle fibers contract  vessel constricts
– Muscle fibers relax  vessel dilates
– Regulate blood pressure
Capillaries:
• Microscopic vessels between arterioles and venules
• Made of one layer of epithelial tissue only
• Form beds of vessels where exchange with body cells
occurs
• Combined large surface area
• Only certain capillaries are open at any given time
– After eating, capillaries serve the digestive system are open
– Those that serve the muscles are closed
• Precapillary sphincters contract, and blood moves from
arteriole to venule by way of an arteriovenous shunt
Blood Vessels
Exchange at the capillary beds is primarily a
result of osmotic and blood pressure
• Blood Pressure
– Causes water to move from capillary to tissue fluid
• Osmotic Pressure created by presence of salts and plasma proteins
– Causes water to move in the opposite direction
• At arterial end of capillaries
– Blood pressure is higher than osmotic pressure of blood
• Water exits a capillary at this end
• Midway along the capillaries
– Two forces are equal and cancel each other out
– No net movement of water
– Solutes diffuse according to their concentration gradient
• Oxygen and nutrients out and CO2 and waste into capillary
• Venule end of capillaries
– Blood pressure decreased, osmotic pressure is greater in blood
– Water tends to move into the capillary
5.6 Exchange at the capillaries
Exchange at the capillary beds is primarily
a result of osmotic and blood pressure
Lymphatic Capillaries
- Collects excess tissue fluid
- once collected in lymphatic capillaries  lymph
- Lymph is returned to the systemic venous blood at
the subclavian veins of the shoulder
5.2 The types of blood vessels
Veins and venules:
• Venules are small veins that receive blood from the
capillaries
• Venule and vein walls have 3 layers:
– Thin inner epithelium
– Thick smooth muscle layer
– Outer connective tissue
• Wall is thinner and can expand to a greater extent
– 70% of blood in veins  blood reservoir
• If blood lose occurs veins constrict to provide more blood to body
• Veins carry blood toward the heart
• Veins that carry blood against gravity have valves to
keep blood flowing toward the heart
5.2 The types of blood vessels
How can you tell the difference
between an artery and vein?
5.3 The heart is a double pump
Anatomy of the Heart
• A large, muscular organ consisting of mostly cardiac
tissue called the myocardium
– Serviced by the coronary artery and cardiac vein
– Muscle fibers branched and joined at intercalated disks
• Allow atrium and ventricles to contract simultaneously
• It is surrounded by a sac called the pericardium
– Supports and protects the heart
• Consists of two sides, right and left, separated by a
septum
• Consists of 4 chambers:
– 2 atria (thin walled) and 2 ventricles (thick walled)
5.3 The heart is a double pump
Anatomy of the Heart
• 2 sets of valves keep blood flowing in the right
direction:
– atrioventricular valves (AV valves)  between atria and
ventricle
• Supported by chordae tendineae attached to papillary muscles
– Prevent valve from inverting when the heart contracts
• Right = tricuspid, Left = bicuspid (mitral valve)
– semilunar valves  between ventricle and attached
vessels
• Pulmonary semilunar valve and aortic semilunar valve
• The valves give the resulting “lub” and “dup” sound
of the heart
5.3 The heart is a double pump
Two cardiovascular
pathways in the body
• Pulmonary circuit: the
right side of the body
that brings blood from
the body to the heart
and the lungs
• Systemic circuit: the left
side of the heart that
brings blood to the
entire body to deliver
nutrients and rid it of
wastes
Blood flow through the heart
1.
2.
3.
4.
5.
6.
7.
8.
9.
Inferior and superior vena cava (1) dump oxygen poor blood
into the right atrium (2)
Right atrium sends oxygen poor blood through AV valve
(tricuspid)
Right ventricle (3) oxygen poor blood through the pulmonary
semilunar valve
2 pulmonary arteries (4) that lead to the lungs (5) where
blood becomes oxygenated
Pulmonary veins (6) bring oxygen rich blood from the lungs
back the left atrium (7)
Left atrium sends blood through AV valve (bicuspid/mitral)
Left ventricle (8) is large and muscular to pump blood
through aortic semilunar valve
Aorta (9) and to the rest of the body (10)
Arterioles from the artery branch into capillaries, where
exchange takes place, and then venules join into the vein
Eventually blood will be pumped back to each vena cava(1)
5.3 The heart is a double pump
Visualizing blood flow through the heart
5.3 The heart is a double pump
How do the structure of the vessels and heart
match their functions?
• The left ventricle is much more muscular than the
right ventricle (pumps to the lungs) because the
left ventricle must pump blood to the entire body
• Heart sends blood out under pressure into the
arteries
• The arteries are more muscular than veins to
withstand the higher pressure exerted on them
• The veins have a thinner wall and a larger center
to store blood
5.3 The heart is a double pump
How does the heartbeat occur?
• Heartbeat = cardiac cycle
• During systole
– the atria contract together followed by the ventricles contracting
together
• This is followed by diastole
– a rest phase, when the chambers relax
• This cardiac cycle, heartbeat, on average occurs 70
times/minute
• Lub:
– increased pressure of blood inside ventricle forces the cusps of the
AV valve to shut
• Dub:
– Pressure of blood inside a ventricle causes the semilunar valves
(pulmonary and aortic) to open
– Ventricle relaxes and blood in the arteries pushes back, causing the
semilunar valves to close
Cardiac Cycle
5.3 The heart is a double pump
How is the heartbeat controlled?
1. Internal control:
– Node tissue in two locations of the heart
– The sinoatrial (SA) node in the right atrium
• initiates the heartbeat and causes the atria to contract
• Also known as pacemaker, keeps heartbeat regular
– This impulse reaches the atrioventricular (AV) node, in the
right atrium
• send a signal down the AV bundle and Purkinje fibers
that causes ventricular contraction
– These impulses travel between gap junctions at intercalated
disks
• Allow electrical current to flow from cell to cell
How is the heartbeat controlled?
2. External control:
– heartbeat is also controlled by
• cardiac center in the medulla oblongata of
the brain
–Parasympathetic (resting) and
sympathetic (fight or flight) portions of
the nervous system
• Hormones released by adrenal medulla,
such as epinephrine and norepinephrine,
stimulate the heart
Visualizing the heartbeat
5.3 The heart is a double pump
Visualizing the gap junctions at the
intercalated disks
5.3 The heart is a double pump
What is an electrocardiogram (ECG)?
• A record of the electrical changes in the heart
muscle during a cardiac cycle
• The atria produce an electrical current when
stimulated by the SA node called the P wave
• The contraction of the ventricles is the QRS
complex
• The recovery of the ventricles is called the T
wave
• Looking at these electrical changes allows
doctors to detect abnormalities
How does a “normal” and abnormal
ECG compare?
Pulse
• Pulse = rhythmic expansion and recoil of an
arterial wall
– Arterial walls pulse whenever the left ventricle
contracts
• Can be felt in any artery that runs close to
the body’s surface
– Commonly used
• Radial Artery: palm side of wrist
• Carotid Artery: either side of the trachea in the neck
5.4 Features of the cardiovascular system
What is blood pressure?
• The pressure against a blood vessel wall, usually
measured in a brachial artery in the arm
• The highest pressure is during blood ejection from the
heart called the systolic pressure
• The lowest pressure is the diastolic pressure when
the ventricles relax
• Average blood pressure is recorded at about 120/80
mmHg (systolic/diastolic)
• Reminder: this is controlled by the arterioles
• Systolic and diastolic blood pressure decrease with
distance from the left ventricle
Blood Pressure
5.4 Features of the cardiovascular system
How is blood pressure categorized?
5.4 Features of the cardiovascular system
What is important about blood
flow?
• Blood flow is under the
highest pressure in the
arteries but remember the
thick, muscular walls
• Blood flow is slower in the
capillaries which is
important to allow time for
exchange between cells
• Blood pressure is minimal
in the veins and venules
but blood flow increases
If blood pressure is so low in the veins why
does the blood flow increase?
Venous Return Depends on:
1. Skeletal muscle
contraction
-
Compression forces blood
past valves
2. Breathing
- inhale, chest expand and
decrease pressure in
thoracic cavity. Blood flows
from higher pressure
(abdominal cavity) to lower
pressure (thoracic cavity)
- exhale, reverse but valves
prevent back wash
3. Valves
5.5 Two cardiovascular pathways
The heart’s blood supply: Coronary
circulation
• There are small coronary arteries that supply
the heart with oxygen rich blood that are
separate from the systemic and pulmonary
pathways of the body
• First branch off of the aorta, just above the
aortic semilunar valve
• Aorta  coronary artery  arterioles 
coronary capillary bed  venules 
converge at cardiac veins  right atrium
5.5 Two cardiovascular pathways
What is the hepatic portal system?
• A system that brings blood from the digestive
tract rich in amino acids and glucose to the
liver
• The liver synthesizes blood proteins and
stores the glucose as glycogen
• The liver also plays a role in purifying blood
from the digestive tract
• Finally, the blood exit the liver via the hepatic
vein and blood will return to the heart via the
inferior vena cava
5.7 Cardiovascular disorders
Why should we care about cardiovascular
disease?
• Cardiovascular disease (CVD) is the most
common cause of death in the western
world
5.7 Cardiovascular disorders
Disorders of the blood vessels:
•
•
•
•
•
Hypertension/high blood pressure
Atherosclerosis
Stroke
Heart attack
Aneurysm
5.7 Cardiovascular disorders
Hypertension
• High blood pressure results when blood
moves through vessels at a rate higher than
normal often due to arterial plaque
• 140/90 mmHg is considered hypertension
• A silent killer because there are few
symptoms
• Can lead to a heart attack, stroke or kidney
failure
5.7 Cardiovascular disorders
Atherosclerosis
• A build up of plaque in blood vessels
• Plaque that is stationary is called a thrombus and an
embolus when it detaches and can move to distant
sites
• Associated with a stroke, heart attack and aneurysm
5.7 Cardiovascular disorders
Stroke
• Also known as a cerebrovascular accident
(CVA)
• Usually occurs when a cranial artery is
blocked or bursts
• Part of the brain dies dues to lack of oxygen
• Symptoms may occur including numbness of
hands or face, difficulty speaking and inability
to see in one eye
5.7 Cardiovascular disorders
Heart attack
• Also known as a myocardial infarction (MI)
• Part of the heart dies due to lack of oxygen
• Can begin with angina pectoris, a pain that
radiates down the left arm due to a blockage
of a coronary artery
5.7 Cardiovascular disorders
Aneurysm
• A ballooning of a blood vessel
• Atherosclerosis and hypertension can
weaken a vessel and cause ballooning
• The most commonly affected is the
abdominal artery or the arteries leading to
the brain
5.7 Cardiovascular disorders
How are disorders of the blood vessels
treated?
• Dissolving blood clots:
– t-PA is a drug that dissolves clots
• Treating clogged arteries:
– Bypass surgery: usually a vein from the leg is taken and
used to bypass a clogged artery
– Stents: wire mesh cylinder inserted into a clogged artery
to hold it open
– Angioplasty: a tube with a balloon is inserted into the
clogged area and the balloon is then inflated to open the
vessel
– A stent and angioplasty may be used in combination
5.7 Cardiovascular disorders
Disorders of the heart and its treatment
• Disorders:
– Heart failure is when the
heart no longer pumps
properly
• Treatments:
– Left ventricular assist
device(LVAD)
– Heart transplant either
natural or artificial
5.7 Cardiovascular disorders
Health Focus: The do’s and don’ts for
prevention of cardiovascular disease?
• Do not smoke
• Do not abuse drugs
• Keep your weight down to decrease chances of
hypertension and Type II diabetes
• Eat a healthy diet
– Low in saturated and trans fats
– Low in cholesterol
• Know your blood cholesterol
• Exercise