chapter 5 cardiovascular system: heart and blood vessels mader, sylvia s. human biology. 13 th...

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

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

5.1 Overview of the cardiovascular system

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

Exchange at the capillary beds is primarily a result of osmotic and blood pressure

5.6 Exchange at the capillaries

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

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


How can you tell the difference between an artery and vein?


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

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 heart1. Inferior and superior vena cava (1) dump oxygen poor blood

into the right atrium (2)2. Right atrium sends oxygen poor blood through AV valve

(tricuspid) 3. Right ventricle (3) oxygen poor blood through the pulmonary

semilunar valve4. 2 pulmonary arteries (4) that lead to the lungs (5) where

blood becomes oxygenated5. Pulmonary veins (6) bring oxygen rich blood from the lungs

back the left atrium (7)6. Left atrium sends blood through AV valve (bicuspid/mitral)7. Left ventricle (8) is large and muscular to pump blood

through aortic semilunar valve8. Aorta (9) and to the rest of the body (10)9. 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)

Visualizing blood flow through the heart5.3 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


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

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

Visualizing the gap junctions at the intercalated disks


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

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

5.4 Features of the cardiovascular system

Blood Pressure

How is blood pressure categorized?


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

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

5.5 Two cardiovascular pathways

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


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


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


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


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


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


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


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


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


chapter 5 cardiovascular system: heart and blood vessels mader, sylvia s. human biology. 13 th...

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