Cardiovascular Anatomy. Objectives: 1. Describe the anatomy of the heart 2. Describe the anatomy of...
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Transcript of Cardiovascular Anatomy. Objectives: 1. Describe the anatomy of the heart 2. Describe the anatomy of...
Cardiovascular Anatomy
Objectives:
1. Describe the anatomy of the heart2. Describe the anatomy of the vasculature3. Describe the pathway of blood during the cardiac cycle
Figure 20–1
Organization of the Cardiovascular System
Position in the thoracic cavity
Figure 20–2b
• Surrounded by pericardial sac• Between 2 pleural cavities • In the mediastinum
• 5 inches base to apex• Apex at 5th intercostal space• Centre of base is to left of midline• Left slant along polar axis• Slight rotation around the polar
axis
Figure 20–2c
• Double lining of the pericardial cavity– Visceral pericardium– Parietal pericardium
Structures of Pericardium
• Pericardial cavity:– Is between parietal and visceral
layers – contains pericardial fluid
• Pericardial sac: – fibrous tissue– surrounds and stabilizes heart
Superficial Anatomy of the Heart
Figure 20–3
Sulci
• Coronary sulcus:– divides atria and ventricles
• Anterior and posterior interventricular sulci:– separate left and right ventricles– contain blood vessels of cardiac
muscle
3 Layers of the Heart Wall
• Epicardium:– outer layer
• Myocardium:– middle layer
• Endocardium:– inner layer
Figure 20–4
Myocardium
• Muscular wall of the heart• Concentric layers of cardiac
muscle tissue• Atrial myocardium wraps around
great vessels• 2 divisions of ventricular
myocardium
2 Divisions of Ventricular Myocardium
• Superficial ventricular muscles:– surround ventricles
• Deep ventricular muscles:– spiral around and between ventricles
Internal Anatomy
Figure 20–6a
The Vena Cava
• Delivers systemic circulation to right atrium
• Superior vena cava:– receives blood from head, neck,
upper limbs, and chest
• Inferior vena cava: – receives blood from trunk, and
viscera, lower limbs
The Pulmonary Trunk
• Delivers deoxygenated blood to the pulmonary circulation
• Leaves the right ventricle and divides into the left and right pulmonary arteries
• Divides into dense capillary network
The Pulmonary Vein
• Left and right pulmonary veins return blood to left atrium.
The Aorta
• Blood leaves left ventricle via the aorta.
• Ascending aorta then turns downward(aortic arch) (supplies head and upper body)
• Becomes descending aorta (supplies lower body)
Aortic Sinuses
• At base of ascending aorta • Prevent valve cusps from sticking
to aorta• Origin of right and left coronary
arteries
Atria
• Thin-walled• Expandable outer auricle• Right and left separated by the
interatrial septum
Atrioventricular (AV) Valves
• Connect right atrium to right ventricle and left atrium to left ventricle
• Permit blood flow in 1 direction: – A V
• Comprising 3 or 2 cusps
Cusps
• Fibrous flaps that form tricuspid (R) and bicuspid (L) valves
• Free edges attach to chordae tendineae from papillary muscles of ventricle
• Prevent valve from opening backward
The Heart Valves
Figure 20–8
Atrioventricular (AV) Valves
• During atrial contraction valves open
• During ventricular contraction– Blood pressure closes valve cusps
during ventricular contraction– Papillary muscles contract and tense
chordae tendineae (to prevent valves from swinging into atria)
Left and Right Ventricles
• Have significant structural differences
Figure 20–7
Structure of Left and Right Ventricles
• Right ventricle wall is thinner, develops less pressure than left ventricle
• Right ventricle is pouch-shaped, left ventricle is round
Trabeculae Carneae
• Muscular ridges on internal surface of right ventricle
• Includes moderator band (R):– ridge contains part of conducting
system– coordinates contractions of cardiac
muscle cells
The Left Ventricle
• Holds same volume as right ventricle
• Is larger; muscle is thicker, and more powerful
• Similar internally to right ventricle, but does not have moderator band
Semilunar Valves
• Pulmonary and aortic tricuspid valves
• Also called Pulmonary Valve and Aortic Valve
• Prevent backflow from pulmonary trunk and aorta into ventricles
• Have no muscular support – open under pressure
Path of blood flow:
Moves to R ventricle through–Tricuspid (AV) valve
Leaves R ventricle via–Pulmonary trunk to pulmonary arteries (L and R pulmonary arteries)
Enters pulmonary circulation
Blood Enters R atrium via –Inferior and superior vena cava
Blood returns from the pulmonary circulation
Path of blood flow:
Blood gathers into left and right pulmonary veins
Pulmonary veins deliver to left atrium
• Blood travels into the left ventricle via– The bicuspid (Mitral) AV valve
Path of blood flow:
Blood leaves the left ventricle via–The aortic/semilunar valve
• Into the Systemic circulation:– blood leaves left ventricle through
aortic valve into ascending aorta– ascending aorta turns (aortic arch)
and becomes descending aorta
Path of blood flow:
Figure 20–6a
Connective Tissue Fibers of the Heart
1. Physically support cardiac muscle fibers
2. Distribute forces of contraction3. Add strength and prevent
overexpansion of heart4. Elastic fibers return heart to
original shape after contraction
The Fibrous Skeleton
• 4 bands around heart valves and bases of pulmonary trunk and aorta
• Stabilise valves • Electrically insulate ventricular
cells from atrial cells
Blood Supply to the Heart• Coronary circulation
Figure 20–9
Coronary Arteries
• Left and right• Originate at aortic sinuses• High blood pressure, elastic
rebound force blood through coronary arteries between contractions
Right Coronary Artery
• Supplies blood to:– right atrium– portions of both ventricles– cells of sinoatrial (SA) and
atrioventricular nodes – marginal arteries (surface of right
ventricle)– branches to posterior interventricular
artery
Left Coronary Artery
• Supplies blood to:– left ventricle– left atrium– interventricular septum
Left Coronary Artery
• 2 main branches:– circumflex artery – anterior interventricular artery
Figure 20–9
Arterial Anastomoses
• Interconnect anterior and posterior interventricular arteries
• Stabilize blood supply to cardiac muscle
Coronary Sinus
• Cardiac veins return blood to coronary sinus
• Coronary sinus opens into right atrium
Cardiac Veins
• Great cardiac vein:– drains blood from area of anterior
interventricular artery into coronary sinus
• Anterior cardiac vein:– empties into right atrium
• Posterior cardiac vein, middle cardiac vein, and small cardiac vein:– empty into great cardiac vein or
coronary sinus
5 Classes of Blood Vessels
1. Arteries:– carry blood away from heart
2. Arterioles:– Are smallest branches of arteries
5 Classes of Blood Vessels
3. Capillaries:– are smallest blood vessels– location of exchange between blood
and interstitial fluid
5 Classes of Blood Vessels
4. Venules:– collect blood from capillaries
5. Veins:– return blood to heart
Structure of Vessel Walls
Figure 21-1
Arteries and Veins
• Walls have 3 layers:– tunica intima– tunica media– tunica externa
The Tunica Intima
• Is the innermost layer• Includes:
– the endothelial lining– connective tissue layer
• In arteries, layer of elastic fibers (external elastic membrane) in outer margin
Tunica Media
• Is the middle layer• Contains concentric sheets of
smooth muscle in loose connective tissue
• Binds to inner and outer layers
Tunica Externa
• Is outer layer• Contains connective tissue sheath• Anchors vessel to adjacent tissues
Tunica Externa
• In arteries:– contain collagen– elastic fibers
• In veins:– contain elastic fibers– smooth muscle cells
Figure 21-2
Artery Characteristics
• From heart to capillaries, arteries change:– from elastic arteries – to muscular arteries – to arterioles
Elastic Arteries
• Also called conducting arteries• Large vessels (e.g., pulmonary
trunk and aorta, 2.5cm) • Tunica media has many elastic
fibers and few muscle cells• Elasticity evens out pulse force
Muscular Arteries
• Also called distribution arteries (0.4 to 0.05cm)
• Are medium-sized (most arteries)• Tunica media has many muscle
cells
Arterioles
• Are small (30µm)• Have little or no tunica externa• Have thin or incomplete tunica
media • Can create resistance to circulation
Capillaries
• Microscopic capillary networks permeate all active tissues
• Location of all exchange functions of cardiovascular system
• Materials diffuse between blood and interstitial fluid
Capillary Structure
• Endothelial tube, inside thin basal lamina
• No tunica media• No tunica externa• Diameter is similar to RBC (8µm)
Capillary Structure
Figure 21-4
2 Types of Capillaries
1. Continuous capillaries2. Fenestrated capillaries
Sinusoids
Capillary Networks
Figure 21-5
3 Vein Categories
1. Venules:– very small veins (20-50µm)– collect blood from capillaries
3 Vein Categories
2. Medium-sized veins (2-9mm thick):
– thin tunica media and few smooth muscle cells
– tunica externa with longitudinal bundles of elastic fibers
3 Vein Categories
3. Large veins (2cm):– have all 3 tunica layers– thick tunica externa– thin tunica media
Valves in the Venous System
Figure 21-6
Vein Valves
• Folds of tunica intima • Prevent blood from flowing
backward• Compression pushes blood toward
heart