Anatomy and Physiology. Is about 4.8 inches tall and 3.35 inches wide Weighs about.68 lb. in men...

The Cardiovascular System

Anatomy and Physiology

Is about 4.8 inches tall and 3.35 inches wide

Weighs about .68 lb. in men and .56 lb. in women

Beats about 100,000 times per day

Beats 2.5 billion time in an average 70 yr. lifetime

Pumps about 2000 gallons of blood each day

Circulates blood completely 1000 times each day

Pumps blood through 62,000 miles of vessels

Suffers 7.2 mil. CAD deaths worldwide each year

The Heart

The heart resides in the pericardiumo A loose membranous sac.

Epicardium

◦ Continuous with the pericardium

Myocardium

◦ Composed of bands of involuntary striated muscle fibers

Endocardium

◦ Thin layer of tissue lining the inside of the heart

Three Layers of The Heart

Atria

◦ Thin-walled upper chambers

◦ Separated by atrial septum

◦ Right side of septum has oval depression, fossa

ovalis cordis, remnant of the foramen ovale

◦ Act as receiving chamber for blood returning

from the body and lungs

Four Chambers of The Heart

Left atrium

Fossa ovalis cordis

Right atrium

Atrial septum

Epicardium

Myocardium

Endocardium

Ventricles

◦ Lower chambers which make up the bulk of

the muscle mass of the heart

◦ Left ventricle 2/3 larger than right ventricle

◦ Right ventricle is a thin-walled and oblong,

like pocket attached to left ventricle

Four Chambers of The Heart

Ventricles

◦ Contraction of left ventricle pulls in right

ventricle, aiding its contraction (termed left

ventricular aid)

◦ Separated by intraventricular septum

Four Chambers of The Heart

Right ventricle

Left ventricle

Intraventricular septum

Superior vena cava

Inferior vena cava

Four Valves of the Heart

Tricuspid valve

◦ Separates right atrium from right ventricle

Pulmonic semilunar valve

◦ Separates right ventricle from pulmonary artery

Four Valves of the Heart

Bicuspid (mitral) valve

◦ Separates left atrium from left ventricle

Aortic semilunar valve

◦ Separates left ventricle from aorta

Blood flow from right ventricle to lungs Blood flow from left ventricle to aorta

Four Valves of the Heart

Chordae tendineae cordis

◦ Anchor free ends of A-V valves to papillary

muscles

◦ Prevent A-V valves from pushing upward into

atria during ventricular contraction

Aortic semilunar valve

Pulmonic semilunar valve

Bicuspid (mitral) valve

Tricuspid valve

Chordae tendineae cordis

Papillary muscles

Cardiac Circulation

Pulmonary artery to left lungPulmonary Artery to right lung

Pulmonary veins from left lung

Pulmonary veins from right lung

Superior vena cava

Aorta

Brachiocephalic artery

Left common carotid artery

Left subclavian artery

Coronary Circulation

Arises from root of the aorta

Left Coronary Artery Right Coronary Artery

Anterior Descending Artery

Circumflex Artery

Posterior Descending Artery

Circulation of the Blood

1) Blood enters the heart through the inferior and superior vena cava, flowing into the right atrium.

2) The blood passes through the tricuspid valve into the right ventricle.

3) It then passes through the pulmonic semilunar valve, entering the pulmonary artery of the pulmonary circulation.

4) It flows through the pulmonary bed of the right and left lungs to the pulmonary vein, reentering the heart at the left atrium.

5) It then flows through the bicuspid valve into the left ventricle.

6) Passing through the aortic semilunar valve, the blood enters the aorta and systemic vascular system.

Anterior descending artery

◦ Supplies anterior sulcus and apex

◦ “Widow maker” heart attack

Circumflex artery

◦ Supplies posterior side of left ventricle

Left Coronary Artery

Together supply most of left ventricle, left

atrium, 2/3 of intra ventricular septum, half

of intra atrial septum, and part of right

atrium

Left Coronary Artery

Anterior View

Posterior View

Posterior descending artery

◦ Supplies posterior intraventricular sulcus

Has numerous smaller branches

Right Coronary Artery

Supplies anterior and posterior portions of

right ventricular myocardium, right atrium,

sinus node, posterior 1/3 of intraventricular

septum, and portion of base of right

ventricle

Right Coronary Artery

Closely parallel the arterial system

Some coronary venous blood enters the

heart through the Thebesian veins

◦ Thebesian veins empty directly into all

chambers thus creating some venous

admixture lowering Pa02

Coronary Veins

Blood Vessels

Large, highly elastic, low resistance to

blood flow

Small muscular arterioles of varying

resistance

The Vascular System-Arterial

Transport blood away from the heart

Generally contain oxygenated blood Exception: pulmonary artery

Composed of three layers◦Tunica adventitia (external layer)◦Tunica media (thickest layer)◦Tunica intima (thinnest layer)

The Vascular System-Arterial

Tunica adventitia◦Consists of connective tissue surrounding

collagenous and elastic fibers

◦Supports and protects the vessel

◦Contains lymphatic vessels and nerve fibers

◦Has fine vessels that provide its blood supply

The Vascular System-Arterial

Tunica media◦Thickest layer

◦Composed of concentrically arranged smooth muscle and elastic fibers

◦Nerve fibers of tunica adventitia terminate in tunica media

The Vascular System-Arterial

Tunica intima◦Thinnest layer of the artery

◦Consists of the epithelium – flat layer of simple squamous cells

◦Common to all blood vessels including the endocardium

The Vascular System-Arterial

Large arteries are termed conductance or elastic arteries because the tunica media has less smooth muscle and more elastic fibers

Medium sized arteries are termed the nutrient arteries because they control the flow of blood to the various regions of the body

Arterioles have a thin tunica intima and adventitia, but a thick tunica media composed almost entirely of smooth muscle and control blood flow to the capillary bed

◦ Called resistance vessels because they control the rate that the blood leaves the arterial tree , control arterial blood volume and thereby blood pressure

The Vascular System-Arterial

Aorta

Brachial

Radial

Ulnar

Femoral

Anterior tibial

Peroneal artery

Posterior tibial

Aortic knob

Circle of Willis

Internal carotidsExternal carotids

Common carotids

Vertebral arteries

Microcirculation

Maintains constant environment for the cells and

tissues

Exchange of nutrients, gases, and wastes

The Vascular System-Capillary

The blood does not directly come in contact with the parenchymal cells and tissues in the body, but constituents of the blood first exit the micro vascular exchange blood vessels to become interstitial fluid, which comes into contact with the parenchymal cells of the body. Lymph is the fluid that is formed when interstitial fluid enters the initial lymphatic vessels of the lymphatic system

Pre-capillary sphincter valves

◦ Smooth muscle rings at the proximal end of the capillary

◦ Contraction decreases blood flow

◦ Relaxation increases blood flow

◦ Responsive to local changes in PaO2, PaCO2, pH, and temperature

◦ Called exchange vessels because they are the site of gas, fluid, nutrient, and waste exchange

The Vascular System-Capillary

The Vascular System-Capillary

Transport deoxygenated blood back to the heart – exception: pulmonary vein

Composed of the same layers as arteries, but are thinner

Called capacitance or reservoir vessels because 70% to 75% of the blood volume is contained in the venous system

Peripheral veins contain one-way valves.

◦ Valves are formed by duplication of endothelial lining

◦ Found in veins >2mm in diameter

◦ Are in areas subjected to muscular pressure, arms/legs

◦ Prevent retrograde flow of blood

The Vascular System-Venous

Mechanisms aiding venous return to the heart:

◦ Sympathetic venous tone

◦ Skeletal muscle pumping or “milking” combined with the one-way valves

◦ Cardiac suction

◦ Thoracic pressure differences created by respiratory efforts (thoracic pump)

The Vascular System-Venous

The Vascular System

Histological Structure of Blood Vessels

Blood

Consists of formed elements (cells) suspended & carried in plasma (fluid part)

Total blood volume: 60-80 mL/kg of body weight

Plasma is straw-colored liquid consisting of 90% H20 & dissolved solutes

◦ Includes ions, metabolites, hormones, antibodies, proteins

Composition of Blood

Constitute 7-9% of plasma Three types of plasma proteins: albumins,

globulins, & fibrinogen◦ Albumin accounts for 60-80%

Creates colloid osmotic pressure that draws H20 from interstitial fluid into capillaries to maintain blood volume & pressure

Globulins carry lipids◦ Gamma globulins are antibodies

Fibrinogen serves as clotting factor◦ Converted to fibrin when clotting blood ◦ Serum is fluid left when blood clots

Plasma Proteins

Composed of erythrocytes (RBCs) & leukocytes (WBCs)

RBCs are flattened biconcave discs◦ Generated in the red bone marrow by

the process of erythropoiesis from the hemocytoblast, a common stem cell

◦ Shape provides increased surface area for diffusion

◦ Lack nuclei & mitochondria◦ Has semi-permeable membrane◦ Contains hemoglobin molecule that

transports oxygen◦ Approx. 30 trillion in the body

Formed Elements

Is the formation of blood cells from stem cells in marrow (myeloid tissue) & lymphoid tissue◦ RBC’s increase in number above normal with

chronic hypoxia Erythropoiesis is formation of RBCs

◦ Stimulated by erythropoietin (EPO) from kidney Leukopoiesis is formation of WBCs

◦ Stimulated by variety of cytokines

Hematopoiesis

2.5 million RBCs created daily

Lifespan of 120 days Old RBCs removed

from blood by phagocytic cells in liver, spleen, & bone marrow◦ Iron recycled back

into hemoglobin production

Erythropoiesis

Have nucleus, mitochondria, & amoeboid ability

Formed in the myeloid tissue Can squeeze through capillary walls

(diapedesis)◦ Granular leukocytes help detoxify foreign

substances & release heparin Include eosinophils, basophils, & neutrophils

Leukocytes

Agranular leukocytes are phagocytic & produce antibodies

Include lymphocytes & monocytes

Leukocytes

Specialized type of blood cell Fragments into small irregular pieces of

protoplasm called thrombocytes and platelets

Have no nucleus Have a granular cytoplasm Function in clot formation

Megakaryocyte

Are smallest of formed elements, lack nucleus

Constitute most of mass of blood clots

Release serotonin to vasoconstrict & reduce blood flow to clot area

Secrete growth factors to maintain integrity of blood vessel wall

Survive 5-9 days

Platelets (thrombocytes)

RBC’s – Males: 4.6 - 6.2 x 10 /mm

Females: 4.2 – 5.4 x 10 /mm

• Hb – Males: 13.5 – 16.5 g/dl

Females: 12 – 15 g/dl

• Hematocrit – Males: 42 – 54%

Females: 38 – 47%

• Leukocytes – 4500 – 11,500/mm

Normal Values

Neutrophils: 40 – 75%

Eosinophils: 0 – 6%

Monocytes: 2 – 10%

Basophils: 0 – 1%

Megakaryocyte: 150,000 – 400,000/mm

Normal Values

Systolic pressure

◦ Pressure during contraction phase of heart

◦ Normal value: 90 – 140 mmHg

Diastolic pressure

◦ Pressure during relaxation phase of heart

◦ Normal value: 60 – 90 mmHg

The Vascular System-Blood Pressure

Mean arterial pressure (MAP)

◦ Average pressure in the arterial system over a

given time

◦ Normal value: 80 – 100 mmHg

The Vascular System-Blood Pressure

Mean arterial pressure

MAP = (2 x diastolic pressure) + (systolic pressure) 3

A MAP of approximately 60 mmHg is necessary to perfuse coronary arteries, brain, kidneys.

The Vascular System-Blood Pressure

Reflects right atrial pressure Influenced by changes in right ventricular

function Measured with catheter placed in superior

vena cava just above right atrium

Central Venous Pressure (CVP)

Purpose◦ Assess blood volume status◦ Administration of fluids◦ Sampling of blood◦ Measurement of SvO2

◦ Assessment of right ventricular pre-load

Normal valueoCVP: < 6 mmHgoRight atrial pressure (RAP): 2-6 mmHg

Central Venous Pressure (CVP)

Used to assess filling pressure of the left side of heart

Measured by flow-directed, balloon-tipped catheter

Measures◦ Pulmonary artery pressures – systolic, diastolic,

mean◦ Right ventricular preload (via right atrial pressure)◦ Right ventricular afterload (via PA systolic

pressure)

Pulmonary Artery Pressure

Normal values

◦ Pulmonary artery pressure, systolic: 20-30 mmHg◦ Pulmonary artery pressure, diastolic: 6-15 mmHg◦ Pulmonary artery pressure, mean: 10-20 mmHg◦ Pulmonary artery wedge pressure, mean:

4-12 mmHg

Pulmonary Artery Pressure

Total amount of blood pumped by the

heart per minute

Cardiac Output = Heart Rate x Stroke

Volume

Normal value – 5L/min

Cardiac Output

Cardiac Index

◦ Volume of blood pumped by the heart per

minute divided by body surface area

CI = CO BSANormal range: 2.5 - 4.0 L/min per square meter

Low values can indicate cardiogenic shock

Cardiac Output

Amount of blood ejected from the ventricle

with each ventricular systole

End-systolic volume (ESV)

◦ Volume remaining after systole

Stroke Volume

End-diastolic volume (EDV)

◦ Volume to which the ventricles fill during

diastole

SV = EDV – ESV

Normal value: 60 – 130 ml/beat

Stroke Volume

Ejection fraction (EF)

◦ Proportion of EDV ejected on each stroke

EF = SV EDV

◦ Normal value – 64%

Stroke Volume

Preload

◦ Initial stretch of the ventricle

◦ The greater the preload, the greater the tension

on contraction

Factors Affecting Stroke Volume

Afterload

◦ Force against which the heart must pump.

◦ In clinical practice, left ventricular afterload

equals systemic vascular resistance.

Factors Affecting Stroke Volume

Contractility

◦ Amount of systolic force exerted by heart muscle at any

given preload.

◦ Increases in contractility leads to higher EF, lower end

systolic volume, and higher stroke volume

◦ Decreases in contractility lead to lower ejection fraction,

higher end systolic volume, and decreased stroke

volume.

Factors Affecting Stroke Volume

Contractility

Inotropism: any factor which affects the contractility of the heart

◦ Positive inotropism

Higher stroke volumes for a given preload: indicating an increase in contractility

◦ Negative inotropism

Decreased stroke volumes for a given preload; indicates a decrease in contractility

Factors Affecting Stroke Volume

Heart rate

Autonomic nervous system

oSympathetic: fight or flight: HR, RR, BP,

pupil dilation and bronchodilation

o Parasympathetic: rest and digest

Factors Affecting Stroke Volume

Heart Rate

◦ Cardiac output directly proportional to heart rate

Relationship exists up to 160 to 180 beats/min

Filling time for ventricles insufficient at higher rates

Factors Affecting Stroke Volume

Sum of all frictional forces opposing blood flow through the vascular circulation.

SVR = Mean Aortic Pressure-Right Atrial Pressure Cardiac Output

◦ Mean Aortic Pressure - use systolic pressure (normal mean =

90mmhg)

◦ Right Atrial Pressure - use central venous pressure (normal mean =

4mmhg)

◦ Cardiac Output normal mean = 5L/min.

Normal value: 15 – 20 mmHg/L/min

The Vascular System-Systemic Vascular Resistance (SVR)

Cardiac anatomy◦ Layers of the heart◦ Chambers of the heart◦ Valves◦ Coronary arteries

Blood flow through the heart Arterial system

◦ Structure of artery◦ Purpose◦ Major arteries

Key Points

Venous system◦ Structure of system◦ Purpose◦ Aids to venous flow

Capillary system◦ Structure of system◦ Purpose

Key Points

Composition of blood Plasma proteins Types of cells, functions, normal values,

abnormalities◦ Erythrocytes◦ Leukocytes◦ Megakaryocytes◦ Platelets◦ Hemoglobin◦ Hematocrit

Key Points

Definition, normal values, and formula (if applicable)◦ Systemic vascular resistance◦ Systolic pressure◦ Diastolic pressure◦ Mean arterial pressure◦ Cardiac output and index◦ Stroke volume, esv, edv, efFactors affecting stroke volume

Key Points