Chapter 18 Anatomy of the Cardiovascular System

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Chapter 18Anatomy of the Cardiovascular System
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Heart

• Location of the heart
• Lies in the mediastinum
• Posteriorly the heart rests on the bodies of
  thoracic vertebrae 5 through 8
• Boundaries of the heart are clinically important
  as an aid in diagnosing heart disorders

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Heart

• Size and shape of the heart
• At birth, is transverse and appears large in
  proportion to diameter of chest cavity, 1/130
  body weight
• Between puberty and 25 years of age the heart
  attains its adult shape and weight, 1/300 body
  weight
• Males- 310 g
• Females- 225 g

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Heart Structure

• Pericardium- covers the heart
• Function of the heart coveringsprovides
  protection against friction

pericardium from a normal ferret
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Heart Structure

• Wall of the heartmade up of three distinct
  layers
• Epicardium
• outer layer of heart wall
• Myocardium
• thick, contractile middle layer of heart wall
• compresses the heart cavities, and the blood
  within them, with great force
• Endocardium
• delicate inner layer of endothelial tissue

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Heart Structure

• Chambers of the heart divided into four cavities
  with the right and left chambers separated by the
  septum
• Atria
• Two superior chambers, known as receiving
  chambers, because they receive blood from veins
• Myocardial wall of each atrium is not very thick,
  because little pressure is needed to move blood
  such a small distance

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Heart Structure

• Ventricles
• Two lower chambers, known as
• pumping chambers, because they
• push blood into the large network of
• vessels
• Ventricular myocardium is thicker than myocardium
  of the atria, because great force must be
  generated to pump blood a large distance (to
  lungs and body)
• myocardium of left ventricle is thicker than the
  right, because it must push blood much further

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Body
Aorta


Superior Vena Cava
Left Atrium
Right Atrium
Pulmonary Vein
Through tricuspid (mitral) valve
Through bicuspid valve
Left Ventricle
Right Ventricle
Pulmonary Artery
Lungs
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Brain Body ? Right Atrium ? Right Ventricle ?
Lungs ? Left Atrium ? Left Ventricle ? Brain
Body
To Brain
To Lungs
Right Ventricle to the LUNGS (blue
chambers) Left Ventricle to the BODY (red
chambers)
To Body
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Heart Valves

• Valves of the heart devices
• that permit the flow of blood
• in one direction only
• Atrioventricular (AV) valvesprevent blood from
  flowing back into the atria from the ventricles
  when the ventricles contract
• Tricuspid valve (LEFT AV valve) guards the left
  atrioventricular orifice with 3 flaps of
  endocardium
• Bicuspid, valve (RIGHT AV valve)similar in
  structure to tricuspid valve except only two
  flaps present

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Heart Valves

• Semilunar (SL) valves
• half moonshaped flaps growing out from the
  lining of the pulmonary artery and aorta
• prevents blood from flowing back into ventricles
  from aorta and pulmonary artery

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Heart Blood Supply

• Artery Carries blood AWAY from heart
• Coronary arteries
• First branches to come off aorta
• Ventricles receive blood from branches of both
  right and left coronary arteries
• Each ventricle receives blood only from a small
  branch of corresponding coronary artery
• Most abundant blood supply goes to myocardium of
  left ventricle

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Heart Blood Supply

• Veins of the coronary circulation
• As a rule, veins follow a course that closely
  parallels that of coronary arteries
• After going through cardiac veins, blood enters
  coronary sinus to drain into right atrium
• Several veins drain directly into right atrium

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Heart

• Conduction system of the heart
• Sinoatrial node (SA node or pacemaker) hundreds
  of cells in right atrial wall near opening of
  superior vena cava- start heart beat
• Atrioventricular node (AV node)small mass of
  special cardiac muscle in right atrium along
  lower part of interatrial septum
• Atrioventricular bundle (bundle of His) and
  Purkinje fibers
• Bundle of His originates in AV node, extends by
  two branches down the two sides of the
  interventricular septum, and continues as
  Purkinje fibers
• Purkinje fibers extend out to papillary muscles
  and lateral walls of ventricles

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Heart

• Nerve supply of the heart
• Cardiac plexuses made up of the combination of
  excitatory and inhibitory fibers
• Vagus fibers inhibitory, or depressor, nerves

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Blood Vessels

• Arteries
• Carry blood AWAY from heartall arteries (except
  pulmonary artery) carry oxygenated blood
• Elastic arteries largest in body
• Examples aorta and its major branches
• Able to stretch without injury
• Accommodate surge of blood when heart contracts
  and able to recoil when ventricles relax

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Blood Vessels

• Arteries
• Muscular (distributing) arteries
• Smaller in diameter than elastic arteries
• Muscular layer is thick
• Examples brachial, gastric, superior mesenteric
• Arterioles (resistance vessels)
• Smallest arteries
• Important in regulating
• blood flow to organs

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Blood Vessels

• Capillaries primary exchange vessels
• Microscopic vessels
• Carry blood from arterioles to venules
• Not evenly distributed
• highest numbers in
• tissues with high
• metabolic rate
• may be absent in some
• avascular tissues
• such as cartilage

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Blood Vessels

• Types of capillaries
• True capillaries
• Continuous capillaries
• Fenestrated capillaries
• Sinusoids

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Blood Vessels

• Veins
• Carry blood toward the heart
• Act as collectors and as reservoir vessels
• called capacitance vessels

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Circulatory routes

• Systemic circulation- Left Ventricle ? Brain
  Body ? Right Atrium
• Pulmonary circulation- Right Atrium ? Right
  Ventricle ? Lungs ? Left Atrium

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Systemic circulation

• Systemic arteries
• arteries ? arterioles ? capillaries

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Fetal circulation

• Basic plan of fetal circulation additional
  vessels needed to allow fetal blood to secure
  oxygen from maternal blood at the placenta
• Umbilical vein- returns oxygenated blood from
  placenta to fetus
• Foramen ovale-opening in septum between right and
  left atria

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Fetal circulation

• Changes in circulation at birth
• When umbilical cord is cut, the two umbilical
  arteries, the placenta and the umbilical vein no
  longer function
• Umbilical vein within the babys body becomes the
  round ligament of the liver
• Foramen ovalefunctionally closed shortly after a
  newborns first breath and pulmonary circulation
  is established structural closure takes
  approximately 9 months
• Ductus arteriosuscontracts with establishment of
  respiration, becomes ligamentum arteriosum

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Cycle of Life Cardiovascular Anatomy

• Birth change from placenta-dependent system
• Heart and blood vessels maintain basic structure
  and function from childhood through adulthood
• Exercise thickens myocardium and increases supply
  of blood vessels in skeletal muscle tissue
• Adulthood through later adulthooddegenerative
  changes
• Atherosclerosis blockage or weakening of
  critical arteries
• Heart valves and myocardial tissue
  degeneratereduces pumping efficiency