Chapter 12The Cardiovascular

System

* function:circulate blood throughout entire body:

– transport O2 and nutrients (glucose) to cells

– transport CO2 and wastes (urea) away from cells– transport immune system cells and antibodies– transport hormones to target cells

* consists of 2 components:

heart “cardio” - pumps blood

blood vessels “ vascular” - carry blood

* 2 circuits:

pulmonary circuit

right side of heart

lung capillaries

left side of heart

systemic circuit

left side of heart

body tissue capillaries

right side of heart

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12.1 Anatomy of the Heart

* located in thoracic cavity between lungs

A. The Wall and Coverings of the Heart

1. pericardium- serous membrane, covers the heart

2. myocardium – cardiac muscle, wall of heart

3. endocardium – inner lining of heart

B. Chambers of the Heart

1. Right Atrium * right upper chamber of heart * receives deoxygenated blood from body (venae cavae) tricuspid (R-AV) valve right ventricle

2. Right Ventricle * right lower chamber of heart * pumps deoxygenated blood pulmonary semilunar valve pulmonary arteries lungs

3. Left Atrium * left upper chamber of heart * receives oxygenated blood from lungs (pulmonary veins)

bicuspid (mitral) valve left ventricle

4. Left Ventricle * left lower chamber of heart * pumps oxygenated blood

aortic semilunar valve aorta body

Right Atrium

Right Ventricle

Left Atrium

Left Ventricle

Interventricular Septum

Heart Chambers

Tricuspid Valve Bicuspid

Valve

Pulmonary Semilunar

Valve

Aortic Semilunar

Valve

Chordae Tendinae

Heart Valves

Pulmonary Arteries

AortaHeart Blood Vessels

Superior Vena Cava

Left Pulmonary

Veins

Right Pulmonary

Veins

Inferior Vena Cava

C. Operation of the Heart Valves 1. AV valves are normally open, they close when ventricles contract. 2. Semilunar valves are normally closed, they open when ventricles contract

D. Coronary Circuit1. Heart muscle gets blood supply from the

coronary arteries, and drains into coronary veins

2. Coronary Circuit Disorders: a. atherosclerosis / plaque = fatty deposits in coronary arteries b. ischemic heart disease = insufficient blood supply to heart c. thromboembolism = blood clot stuck in coronary artery d. angina pectoris = chest pain left arm e. myocardial infarction = damage to myocardium “heart attack”

3. Surgical Procedures a. balloon angioplasty = balloon inflates to open up a clogged coronary artery b. coronary bypass operation = portion of blood vessel from another part of body is used to bypass blocked coronary arteries

12.2 Physiology of the Heart

A. Conduction System of the Heart* electrical system of the heart * causes contraction of the heart muscle* controlled by brain autonomic NS

1. Nodal Tissue

a. SA (sinoatrial) node * upper posterior wall of right atrium * initiates heartbeat “pacemaker” * causes atria to contract

b. AV (atrioventricular) node * base of right atrium near septum * “relay station”

AV bundle “bundle of HIS”

bundle branches

Purkinje fibers * causes ventricles to contract

2. Electrocardiogram (ECG) * graph: records electrical activity of

heart

* consists of a set of waves:

P = depolarization (contraction) of atria

QRS = depolarization (contraction) of ventricles

T = ventricles repolarize (recover)

Electrocardiogram

Intervals show timing of cardiac cycleP-P = one cardiac cycleP-Q = time for atrial depolarizationQ-T = time for ventricular depolarizationT-P = time for relaxation

B. Cardiac Cycle and Heart Sounds

1. cardiac cycle * events that occur during one

heartbeat systole = contraction of heart

muscle diastole = relaxation of heart

muscle

* 3 phases:

1. atrial systole atria contract (blood is forced into

ventricles) venrtricles relaxed AV valves open, semilunar valves closed

2. ventricular systole ventricles contract (blood forced out of

heart) atria are relaxed AV valves close “lubb”, semilunar valves

open

3. atrial and ventricular diastole

atria and ventricles are relaxed blood flows from atria to ventricles AV valves open, semilunar valves close

“dup”

2. Heart Sounds * caused by the closing of the heart

valves * “lubb-dup”

C. Cardiac Output (CO)

* volume of blood pumped out of a ventricle in one minute

* dependent on 2 factors:

Heart Rate (HR) - beats per minute

Stroke Volume (SV) - amount of blood

A Simple Model of Stroke Volume

Figure 20.19a-d

Factors Affecting Cardiac Output

Figure 20.20

Cardiac Output: An Example

CO (ml/min) = HR (75 beats/min) x SV (70 ml/beat) CO = 5250 ml/min (5.25 L/min)• If HR increases to 150 b/min and SV increases to 120

ml/beat, then– CO = 150 b/min x 120 ml/beat– CO = 18,000 ml/min or 18 L/min (WOW is right!!)

12.3 Anatomy of Blood Vessels

A. Arteries and Arterioles * transport blood away from heart * usually transport oxygenated blood * thick, strong, elastic walls * 3 layers (tunic = coat):

tunica interna (intima) - inner layer, endothelium

tunica media - middle layer (thick), sm. muscle

tunica externa (adventitia) - outer layer, CT

* arterioles = small arteries

B. Capillaries * microscopic blood vessels * join arterioles to venules * site of gas/nutrient/waste exchanges

C. Veins and Venules * transport blood toward the heart * usually transport deoxygenated blood * walls are much thinner (same 3 layers)

Fig. 21.5

A

V

Tunica adventitia

Tunica media

Tunica intima

* some veins have valves (arms, legs)

* venules = small veins

Direction of blood flow in vessels:Arteries

Arterioles Capillaries

Venules Veins

12.4 Physiology of Circulation

A. Velocity of Blood Flow * fastest in arteries, slowest in capillaries

Velocity of blood flow (mL/s)

Blood Vessels

B. Blood Pressure * force of blood against a vessel wall * decreases with distance from left

ventricle * 2 factors that affect BP:

cardiac output – HR and SVperipheral resistance – arterial diameter and length

* Avg. BP in young adult = 120/80 top number = systolic pressure bottom number = diastolic pressure

* venous return depends on: skeletal muscle pump – muscles

squeeze respiratory pump - breathing

movements

valves in veins

C. Evaluating Circulation

1. Pulse * surge/wave of pressure in an artery * = heart rate (bpm)

* pulse points can be felt in arteries close to skin

2. Blood Pressure * = force of blood (mm Hg) * measured with a sphgmomanometer

Steps for measuring BP Apply cuff above elbow Place stethoscope on brachial artery Inflate cuff until pulse disappears

Steps for measuring BP cont.

Let air out gradually Listen for sounds that blood is moving past cuff

systolic pressure = pressure when 1st sound is heard

diastolic pressure = pressure when last sound is heard

* hypertension = 140/90

12.5 Circulatory Routes

A. The Major Systemic Arteries

* see p.243

B. The Major Systemic Veins

* see p.244

C. Special Systemic Circulations

* hepatic portal system = from stomach/intestines to liver

* cerebral arterial circle = brain

* fetal circulation = fetus (no circulation to lungs)