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 resides in the pericardium

o 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

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

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

Ventricles

◦ Contraction of left ventricle pulls in right

ventricle, aiding its contraction (termed left

ventricular aid)

◦ Separated by intraventricular septum

Right ventricle

Left ventricle

Intraventricular septum

Superior vena cava

Inferior vena cava

Tricuspid valve

◦ Separates right atrium from right ventricle

Pulmonic semilunar valve

◦ Separates right ventricle from pulmonary artery

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

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

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

Arises from root of the aorta

Left Coronary ArteryRight Coronary Artery

Anterior Descending Artery

Circumflex Artery

Posterior Descending Artery

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

Together supply most of left ventricle, left

atrium, 2/3 of intra ventricular septum, half

of intra atrial septum, and part of right atrium

Posterior descending artery

◦ Supplies posterior intraventricular sulcus

Has numerous smaller branches

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

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

Large, highly elastic, low resistance to blood

flow

Small muscular arterioles of varying

resistance

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)

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

Tunica media

◦ Thickest layer

◦ Composed of concentrically arranged smooth muscle and elastic fibers

◦ Nerve fibers of tunica adventitia terminate in tunica media

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

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

Aorta

Brachial

Radial

Ulnar

Femoral

Anterior tibial

Peroneal artery

Posterior tibial

Aortic knob

Circle of Willis

Internal carotids

External carotids

Common carotids

Vertebral arteries

Microcirculation

Maintains constant environment for the cells and

tissues

Exchange of nutrients, gases, and wastes

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

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

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)

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

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

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

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

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

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

Agranularleukocytes are phagocytic & produce antibodies

Include lymphocytes & monocytes

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

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

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

Neutrophils: 40 – 75%

Eosinophils: 0 – 6%

Monocytes: 2 – 10%

Basophils: 0 – 1%

Megakaryocyte: 150,000 – 400,000/mm

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

Mean arterial pressure (MAP)

◦ Average pressure in the arterial system over a

given time

◦ Normal value: 80 – 100 mmHg

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.

Reflects right atrial pressure

Influenced by changes in right ventricular function

Measured with catheter placed in superior vena cava just above right atrium

Purpose◦ Assess blood volume status

◦ Administration of fluids

◦ Sampling of blood

◦ Measurement of SvO2

◦ Assessment of right ventricular pre-load

Normal valueoCVP: < 6 mmHg

oRight atrial pressure (RAP): 2-6 mmHg

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)

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

Total amount of blood pumped by the heart

per minute

Cardiac Output = Heart Rate x Stroke

Volume

Normal value – 5L/min

Cardiac Index

◦ Volume of blood pumped by the heart per

minute divided by body surface area

CI = CO

BSA

Normal range: 2.5 - 4.0 L/min per square meter

Low values can indicate cardiogenic shock

Amount of blood ejected from the ventricle

with each ventricular systole

End-systolic volume (ESV)

◦ Volume remaining after systole

End-diastolic volume (EDV)

◦ Volume to which the ventricles fill during

diastole

SV = EDV – ESV

Normal value: 60 – 130 ml/beat

Ejection fraction (EF)

◦ Proportion of EDV ejected on each stroke

EF = SV

EDV

◦ Normal value – 64%

Preload

◦ Initial stretch of the ventricle

◦ The greater the preload, the greater the tension

on contraction

Afterload

◦ Force against which the heart must pump.

◦ In clinical practice, left ventricular afterload

equals systemic vascular resistance.

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.

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

Heart rate

Autonomic nervous system

o Sympathetic: fight or flight: HR, RR, BP, pupil

dilation and bronchodilation

o Parasympathetic: rest and digest

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

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

SVR = Mean Aortic Pressure-Right Atrial PressureCardiac 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

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

Venous system◦ Structure of system

◦ Purpose

◦ Aids to venous flow

Capillary system◦ Structure of system

◦ Purpose

Composition of blood

Plasma proteins

Types of cells, functions, normal values, abnormalities◦ Erythrocytes

◦ Leukocytes

◦ Megakaryocytes

◦ Platelets

◦ Hemoglobin

◦ Hematocrit

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, ef

Factors affecting stroke volume