Download Chapter 12 The Cardiovascular System What is the cardiovascular

Chapter 12
The Cardiovascular System
What is the cardiovascular system?
 Includes the heart, blood vessels, and blood
 Brings nutrients to cells and helps get rid of wastes
 The blood is refreshed in the lung, kidneys, intestine and liver
 Lymphatic vessels help this system by collecting excess fluid surrounding
tissues and returning it to the cardiovascular system
Anatomy of the heart
 A large, muscular organ consisting of mostly cardiac tissue called the
myocardium
 It is surrounded by a sac called the pericardium
 Consists of two sides, right and left, separated by a septum
 Consists of four chambers, two atria and two ventricles
Blood flow
 Inferior and superior vena cava (1) dump blood into the right atrium (2)
 Right ventricle (3)
 2 pulmonary arteries (4) that lead to the lungs (5) where blood becomes
oxygenated
 Pulmonary veins (6) bring blood from the lungs back to the left atrium (7)
 Left ventricle (8) is large and muscular to pump blood into the aorta (9) and to
the rest of the body (10)
 Eventually blood will be pumped back to each vena cava (1)
The two cardiovascular pathways in the body
 Pulmonary circuit: the right side of the heart 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
All of this requires properly functioning valves
 2 sets of valves: semilunar valves and atrioventricular valves (AV valves)
 The opening and closing of the valves give the resulting “lub” and “dup” sound
of the heart
Cardiac cycle
 Diastole is a rest phase, when the chambers relax
 This is followed by systole when the atria contract together followed by the
ventricles contracting together
 This cardiac cycle, your heartbeat, occurs on average 70 times/minute
Control of heartbeat
 Internal control:
o
The SA node in the right atrium initiates the heartbeat and causes
the atria to contract
o
This impulse reaches the AV node, also in the right atrium, to send a
signal down the AV bundle and Purkinje fibers that causes ventricular
contraction
o
These impulses travel between gap junctions at intercalated disks
 External control:
o
Heartbeat is also controlled by a cardiac center in the brain and
hormones such as epinephrine and norepinephrine
Electrocardiogram (ECG)
 A record of the electrical changes in the heart muscle during a cardiac cycle
o
The atria produce an electrical current when stimulated by the SA
node called the P wave
o
The contraction of the ventricles is the QRS complex
o
The recovery of the ventricles is called the T wave
 Looking at these electrical changes allows doctors to detect abnormalities
Blood pressure
 The pressure against a blood vessel wall, usually measured in an 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)
Blood vessels
 Heart ➔arteries ➔arterioles ➔capillaries ➔venules ➔veins ➔back to the heart
 Arteries and arterioles
o
Carry blood away from the heart
o
Their walls have 3 layers:
 Thin inner epithelium
 Thick smooth muscle layer
 Outer connective tissue
o
Arterioles are small arteries that regulate blood pressure
 Capillaries
o
Microscopic vessels between arterioles and venules
o
Made of one layer of epithelial tissue
o
Form beds of vessels where exchange with body cells occurs
o
All of them combined form an extremely large surface area
 Veins and venules
o
Venules are small veins that receive blood from the capillaries
o
Venule and vein walls have 3 layers:
 Thin inner epithelium
 Thick smooth muscle layer
 Outer connective tissue
o
Veins carry blood toward the heart
o
Veins that carry blood against gravity have valves to keep blood
flowing toward the heart
Composition of blood
o Formed elements: produced in red bone marrow
o
Red blood cells/erythrocytes (RBC)
o
White blood cells/leukocytes (WBC)
o
Platelets
o Plasma:
o
92% water and 8% salts and organic molecules
o
Plasma proteins are the most abundant molecules
o White blood cells
o
Derived from red bone marrow
o
Large blood cells that have a nucleus
o
Their production is regulated by colony-stimulating factor (CSF)
o
Can be found in the blood as well as in tissues
o
Fight infection and are an important part of the immune system
o
Some live days and others live for months or even years
o Red blood cells
o
They lack a nucleus and have only a few organelles
o
The biconcave shape increases the surface area available for
exchanges
o
Each contains about 200 million hemoglobin molecules that bind 3
molecules of O2 each
o
o
o
o
o
Lifespan of ~120 days
Erythropoiesis is the production of new RBCs
ABO blood types
 Like many body cells, RBCs have surface markers
 The most common and well-known are the ABO markers
 It all has to do with which antigens are present on the RBCs
The Rh factor is also a surface antigen with a difference
 The problem arises if a Rh- female has a Rh+ child
 But it can also be easily avoided
Platelets
 Made of fragments of large cells called megakaryocytes made
in the red bone marrow
 About 200 billion are made per day
 Function in blood clotting
 Blood proteins named thrombin and fibrinogen are important
for blood clotting by forming fibrin threads that catch RBC’s
Cardiovascular disease
 Cardiovascular disease (CVD) is the most common cause of death in the
western world
 Disorders of the blood vessels
o
Hypertension/high blood pressure
o
Atherosclerosis
o
Stroke
o
Heart attack
o
Aneurysm
o
Hypertension
o
High blood pressure results when blood moves through vessels at a
rate higher than normal often due to arterial plaque
o
140/90 mmHg is considered hypertension
o
A silent killer because there are few symptoms
o
Can lead to a heart attack, stroke or kidney failure
 Atherosclerosis
o
A build up of plaque in blood vessels
o
Plaque that is stationary is called a thrombus and an embolus when
it detaches and can move to distant sites
o
Associated with stroke, heart attack and aneurysms
 Aneurysm
o
A ballooning of a blood vessel
o
Atherosclerosis and hypertension can weaken a vessel and cause
ballooning
o
The most commonly affected is the abdominal artery or the arteries
leading to the brain
 Stroke
o
Also known as a cerebrovascular accident (CVA)
o
Usually occurs when a cranial artery is blocked or bursts
o
Part of the brain dies dues to lack of oxygen
o
Symptoms may occur including numbness of hands or face,
difficulty speaking and inability to see in one eye
 Heart attack
o
Also known as a myocardial infarction (MI)
o
Part of the heart dies due to lack of oxygen
o
Can begin with angina pectoris, a pain that radiates down the left
arm due to a blockage of a coronary artery