Cardiovascular Anatomy

Objectives: 1. Describe the anatomy of the heart 2. Describe the anatomy of the vasculature 3. 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 5 th 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 contraction 3.Add strength and prevent overexpansion of heart 4.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 capillaries 2.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