notes

Cardiovascular System Function

• Transporting blood throughout the body

• Delivering oxygen and nutrients

• Removal of carbon dioxide and other waste products

• Goal: provide adequate perfusion to all body tissues

Perfusion

The delivery of blood per time per gram of tissue; typically expressed in mL/min/g. Adequate perfusion involves delivering sufficient blood to maintain the health of all body cells.

Function of the Heart

Muscular pump that circulates blood through vessels

Arteries

Carry blood away from heart; aorta

Veins

Carry blood to heart; pulmonary veins

Capillaries

Exchange nutrients and gases with tissues

Right side of the Heart

• Receives deoxygenated blood from the body

• Pumps it to the lungs

• Blue shading

Left side of the Heart

• Receives deoxygenated blood from the body

• Pumps it to the body

• Red shading

Atrium

Chamber or cavity to which are connected to other chambers or passageways

Ventricle

Cavity within an organ such as the heart or the brain

Pulmonary Circuit

Carries blood from heart → lungs → heart

Systemic Circuit

Carries blood from heart → body → heart

Right Ventricle

Part of the pulmonary circuit that pumps blood to the lungs

Left Ventricle

Part of the systemic circuit that pumps blood to the body

Great Vessels

Large arteries and veins that directly connect the specific chambers of the heart

Blood Flow through Pulmonary Circulation

Converts deoxygenated blood from the right side of the heart through blood vessels to the lungs for the pickup of oxygen and the release of carbon dioxide, and then back through blood vessels to the left side of the heart.

Blood Flow through Systemic Circulation

Moves oxygenated blood from the left side of the heart. The blood vessels deliver oxygenated blood to systemic cells, such as those of the liver, skin, muscle, and brain, for the exchange of nutrients, respiratory gases, and wastes, before returning the blood to vessels that enter the right side of the heart.

Location and Position of the Heart

• The heart is located posterior to the sternum, left of the body midline, between the lungs in the mediastinum

• The posterosuperior surface of the heart is called the base

• The inferior, conical end of the heart is called the apex
  
  *Think of the heart's position like an "upside down" pyramid with the apex below the base.

Pericardium

Covering of the heart consisting of fibrous and serous layers

Fibrous pericardium

• Composed of dense connective tissue that encloses the heart but isn’t attached

• Attached superiorly to base of arterial trunk (pulmonary trunk and aorta) or grest vessels

• Also attached inferiorly to the diaphragm

Parietal layer of the serous pericardium

• Composed of simple squamous epithelium and an underlying delicate layer of areolar connective tissue

• Layer adheres to inner surface of fibrous pericardium

Visceral layer of serous pericardium

• Epicardium of the heart

• Composed of simple squamous epithelium

• Underlying delicate layer of areolar connective tisseue

• Forms the external surface of the heart

List the structural components of the pericardium.

The pericardium that encloses the heart includes the pericardial sac, which has an outer fibrous pericardium and an inner parietal layer of serious pericardium, and a visceral layer of serous pericardium (epicardium) that forms the outer layer of the heart wall.

Pericardial Cavity

A potential space between the layers of the serous pericardium that contains serous fluid, produced by the serous membranes, which lubricates the surfaces to reduce friction

Serous Fluid

the space between the parietal layer and visceral layer of the pericardium

Pericarditis

• Inflammation of the pericardium, typically caused by viral, bacterial, or fungal infections.

• Leaky, excess fluid leaving blood and accumulating within the pericardial cavity

• Heart is unable to pump blood

• Can cause cardiac tamponade, heart failure and death

Compare the superficial features of the anterior and posterior aspects of the heart

The right side of the heart is more visible from the anterior view, and the left side of the heart is more visible from the posterior view.

Three layers of the heart wall and the tissue components of each

1. Epicardium: the outermost layer that is also called the visceral layer of serous pericardium

2. Myocardium: the middle and thickest layer. Contraction of the cardiac muscle in the myocardium generates the force necessary to pump blood

3. Endocardium: covers the internal surface of the heart and the external surfaces of the heart valves. It is continuous with the inner lining of blood vessels.

Atrioventricular valves

• The right AV valve covers the right atrioventricular opening, and it has three cusps; the left AV valve covers the left atrioventricular opening, but it only has two cusps

• When open, the cusps of the valve extend into the ventricles, allowing blood to move from an atrium into the opening of a ventricle. This causes the AV valves to close

• The papillary muscles secure the thin chordae tendineae that attach to the lower surface of each AV valve cusp, preventing blood flow back into the atrium.

Semilunar Valves

• The pulmonary semilunar valve is located between the right ventricle and the pulmonary trunk, and the aortic semilunar valve is located between the left ventricle and the aorta.

• Cusps: Each valve has three pocket-like flaps, or cusps, that look like half-moons.

• Opening: Pressure from heart contractions pushes the valves open to let blood rush out into the arteries.

• Closing: When the heart relaxes, backward blood pressure catches in the pockets and snaps the valves shut.

• Heart sound: The snapping shut of these two valves creates the second part ("dub") of the classic "lub-dub" heartbeat sound

Tricuspid Valve

Right atrioventricular valve

Mitral (Bicuspid) Valve

Left atrioventricular valve

General structure of cardiac muscle

Cardiac muscle cells are small, have one or two centrally located nuclei, and are branched.

Aortic Valve

Valve between the left ventricle and aorta

Describe the four chambers of the heart and its function

• Right Atrium (Upper Right Chamber): Receives oxygen-poor blood from the body and pumps it down into the right ventricle

• Right Ventricle (Lower Right Chamber): Receives oxygen-poor blood from the right atrium and pumps it out to the lungs to pick up oxygen

• Left Atrium (Upper Left Chamber): Receives oxygen-rich blood coming back from the lungs and pumps it down to the left ventricle

• Left Ventricle (Lower Left Chamber): Receives oxygen-rich blood from the left atrium and pumps it forcefully out to the rest of the body

Hypertrophic Cardiomyopathy

• Also known as hypertrophic heart or heart enlargement

• Inward growth (hypertrophy) of heart walls, especially in one or both ventricles

• Narrows the openings (outlets) for the blood to pass through

• Decreases cardiac blood pumped by ventricles per

Describe the location and function of the fibrous skeleton

The fibrous skeleton provides an attachment site for heart valves and cardiac muscle, and prevents action potentials from spreading between the atria and ventricles except through the AV node

Coronary Circulation

Circulation of blood to and from the heart wall

Coronary Arteries

Coronary arteries supply oxygenated blood to the heart wall and include the left and right coronary arteries that branch off the aorta

Describe the specific areas of the heart supplied b their major branches

• three major coronary arteries off the right side of the heart (RMP): the right coronary artery splits into the right marginal artery and posterior inter ventricular artery

• three major coronary arteries off the left side of the heart (LAC): the left coronary artery, the anterior inter ventricular artery, and circumflex artery

Explain the significance of coronary arteries as functional end arteries

• Some arteries may share connections, called arterial anastomoses

• Other arteries terminate in capillary beds only, and are called end arteries

• The left and right coronary arteries are considered functional end arteries because, although there coronary arteries have anastomoses, if one of the arteries becomes blocked these anastomoses are too tiny to shunt sufficient blood from one artery to the other.

• As a result, the part of the heart wall that was supplied by one coronary artery branch will die due to lack of blood flow to the tissue.

Blood Flow through the coronary arteries

Blood flow to the heart wall is not a steady stream; it is impeded and then flows, as the heart rhythmically contracts and relaxes

Heart Sounds

• S₁ ("lub") - AV valves close (tricuspid & mitral valve)

• S₂ ("dub") - semilunar valves close (pulmonary semilunar & aortic semilunar valves)

Coronary Veins and Specific Heart Drainage

Venous return is through the cardiac veins (great, middle, and small) into the coronary sinus, which collects venous blood and drains deoxygenated blood from the heart wall directly into the right atrium of the heart

Describe the general structure of cardiac muscle

• Involuntary, striated muscle found in the heart wall

• Are short, thick, and branched (often Y-shaped)

• One or two nuclei per cell

Structures of Cardiac Muscle: Intercalated Discs

• Desmosomes act as mechanical junctions to prevent cardiac muscle cells from pulling apart.

• Gap Junctions provide a low-resistance pathway for the flow of ions between cardiac cells

  • Allow an action potential to move continuously along the sarcolemma of cardiac muscle cells, resulting in synchronous contraction of that chamber.

How does Cardiac Muscle meets its energy needs

• Aerobic cellular respiration for supplying ATP

• Creatine kinase transfers Pi from creatine phosphate to ADP, yielding ATP and Creatine

• It is also versatile in being able to use different types of fuel molecules, including fatty acids, glucose, lactic acid, amino acids, and ketone bodies.

Myoglobin

Molecule that binds oxygen within muscle

Conduction System

Stimulation of the heart involves the initiation of an action potential at the SA node and its transmission through the conduction system.

Structure of the Conduction System

• SA node: located in posterior wall of right atrium, adjacent entrance of the superior vena cava

• AV node: located n the floor of the right atrium between right AV valve and the opening for coronary sinus

• AV bundle: extends from AV node into and through the interventricular septum (left and right bundle branches)

• Subendocardial Branches (Purkinje Fibers): extend from left to right bundle branches beginning at the apex heart

Components of the Heart’s Conduction System

• Sinoatrial (SA) node

• Atrioventricular (AV) node

• AV bundle

• Purkinje fibers

  • Composed of specialized cardiac cells that initiate and conduct action potentials resulting in a heartbeat.

Parasympathetic Innervation of the Heart

Parasympathetic innervation comes from the cardioinhibitory center to decrease the heart rate

Sympathetic Innervation of the Heart

Sympathetic innervation comes from the cardioacceleratory center to increase the heart rate and increase force of contraction

Describe the pumps and channels associated with cardiac nodal cells.

• The pumps and channels associated with neurons are also in the plasma membrane of nodal cells

• A type of channel unique to nodal cells is the slow voltage-gated Na+ channel that allows the nodal cells to spontaneously depolarize