anatomy and physiology. is about 4.8 inches tall and 3.35 inches wide weighs about.68 lb. in men...
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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