Cardiovascular System Lecture 1 and 2

Components of the circulatory system

• Pump (heart)

• Liquid (blood)

• Container (vasculature)

• Control system

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Pump

A pump is a device that moved fluids by mechanical action. Pumps consume energy to perform mechanical work.

Herat anatomy overview

• 4 chambers

• 4 valves

4 chambers of heart

• Right atrium

• Right ventricle

• Left atrium

• Left ventricle

4 valves of heart

• Right atrioventricular valve

• Pulmonic valve

• Left atrioventricular valve

• Aortic valve

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Right atrioventricular valve

Also known as the tricuspid valve, it is located between the right atrium and right ventricle, preventing backflow of blood into the atrium during ventricular contraction.

Pulmonic valve

Also known as the pulmonary valve, it is situated between the right ventricle and the pulmonary artery, allowing blood to flow from the heart to the lungs for oxygenation.

Left atrioventricular valve

Also known as the mitral valve, it is located between the left atrium and left ventricle, preventing backflow of blood into the atrium during ventricular contraction.

Aortic valve

Also known as the aortic semilunar valve, it is positioned between the left ventricle and the aorta, allowing blood to exit the heart and enter the systemic circulation.

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Blood flow through heart

1. Right atriu

2. Right ventricle

3. Pulmonary artery

4. Lungs

5. Pulmonary veins

6. Left atrium

7. Left ventricle

8. Aorta

9. Body

10. Vena cava

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Components of the heart

• Myocardium

• Valves

• Conduction system

• Coronary vasculature

Myocardium

The myocardium is the muscular layer of the heart responsible for contracting and pumping blood throughout the body. It is composed of cardiac muscle tissue and forms the bulk of the heart wall.

Conduction system

The conduction system of the heart is a group of specialized cardiac muscle cells that generate and propagate electrical impulses, coordinating the heart's rhythm and ensuring efficient pumping of blood.

Coronary vasculature

The coronary vasculature refers to the network of blood vessels that supply blood to the heart muscle itself. This includes coronary arteries and veins that ensure sufficient oxygen and nutrient delivery to the myocardium.

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What cells reside in myocardium

1. Myocytes

2. Specialized conducting tissue (modified myocytes)

3. Fibroblasts

4. Endothelial cells

5. Nervous tissue

Myocytes

Muscle cells responsible for contraction of the heart, facilitating pumping action.

Myocyte examples

Cardiac muscle cells and Sinoatrial node cells

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Specialized conducting tissue (modified myocytes)

includes the bundle of His and Purkinje fibers, which facilitate electrical conduction in the heart.

Specialized conducting tissue (modified myocytes) examples

include bundle branches and atrioventricular node.

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Fibroblasts

are a type of cell in connective tissue that produce collagen and other fibers. They play a critical role in wound healing and tissue repair.

Fibroblasts examples

include myofibroblasts and adipocytes.

Endothelial cells

are specialized cells that line the blood vessels and lymphatic vessels, playing a key role in vascular function and regulation.

Endothelial cell examples

include capillary endothelial cells and arterial endothelial cells.

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Nervous tissue

is a type of tissue that is responsible for transmitting signals throughout the body. It is composed of neurons and glial cells, playing a crucial role in communication and coordination of bodily functions.

Nervous tissue examples

include neurons and glial cells.

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What is the driving force for the movement of blood through vasculature?

The pressure gradient created by the contraction of the heart, particularly during systole. This pressure pushes blood from areas of higher pressure to areas of lower pressure, facilitating circulation.

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What does this show?

Pressure gradients drive the movement of blood through the circulatory system

What does each variable mean?

• (Flow Rate): The volume of fluid moving through the system per unit of time (e.g., liters per minute).

• (Pressure Gradient/Change in Pressure): The difference in pressure between the start and the end of the vessel. Pressure drives the fluid forward, so a higher difference creates more flow.

• (Resistance): The friction or obstruction that the fluid encounters as it moves through the pipe or vessel. Higher resistance slows down the flow

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Diastole

The phase of the cardiac cycle when the heart muscle relaxes and the chambers fill with blood. It occurs before systole, which is the contraction phase.

Systole

The phase of the cardiac cycle where the heart muscles contract, pumping blood out of the chambers and into the arteries. It follows diastole and is essential for circulation.

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What does this mean?

Cardiac output

What do each of these variables mean?

• CO (Cardiac Output): The volume of blood pumped by the heart per minute, usually expressed in liters per minute (L/min) . A normal resting adult has a CO of about 5 L/min.

• SV (Stroke Volume): The volume of blood ejected by the left ventricle with each single heartbeat, typically measured in milliliters per beat (mL/beat). The average resting SV is about 70 mL .

• HR (Heart Rate): The number of times the heart beats per minute (bpm). A normal resting heart rate typically ranges from 60 to 100 bpm

What happens when something goes wrong with the heart? (2)

• Heart disease

• Heart failure

Heart disease

Something is wrong with the heart

Types of heart disease

can include coronary artery disease, arrhythmias, and valvular heart disease.

Heart failure

Heart is unable to deliver sufficient blood to the tissues

Heart failure types

include systolic and diastolic heart failure.

4 chambers of heart

• Right atrium (RA)

• Right ventricle (RV)

• Left atrium (LA)

• Left ventricle (LV)

4 valves of heart

• 2 Atrioventricular (AV) valves

  • Right AV valve

  • Left AV valve

• Pulmonic valve

• Aortic valve

Major blood vessels in heart

• Cranial and caudal vena cava

• Pulmonary trunk

• Pulmonary veins

• Aorta

Cranial and caudal vena cava

Major veins that drain into RA

Pulmonary trunk

• From RV to lungs

• Splits into left and right pulmonary arteries

• Deoxygenated blood

Pulmonary veins

• From lungs to LA

• Oxygenated blood

Aorta

From LV to systemic circulation

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Heart histology

heart is composed of 3 layers

3 layers of heart

• Endocardium

• Myocardium

• Epicardium

Endocardium

Lines the atria and ventrciles

Myocardium

• Cardiac muscle

• Contractile units = sarcomeres

Sarcomeres

The basic contractile units of cardiac muscle, composed of actin and myosin filaments that enable muscle contraction.

Contractile units

• Composed of actin/myosin filaments

• Contraction requires ATP and Ca2+

Epicardium (Visceral Pericardium)

• Outer layer of simple squamous cells

• Lines pericardial cavity

Intercalated disks

In cardiac muscle; anchoring structures containing gap junctions

Cardiac muscle cells

Faintly striated, branching, mononucleated cells, which connect by means of intercalated disks to form a functional network

The action potential

Travels through all cells connected together forming a functional syncytium in which cells function as a unit

Syncytium

A multinucleated cell formed by the fusion of individual cells, allowing coordinated contraction in cardiac muscle tissue.

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Problem List:

• Grade V/VI basilar systolic murmur

• Weak synchronous femoral pulses

• More diagnostics are necessary - WHICH?

• Electrical analysis of heart

• Functional analysis of heart

• START WITH THE HEART

Pulmonary circulation

To lungs from RV

• Arteries deoxygenated

• Veins oxygenated

Systemic circulation

To body from LV

• Arteries oxygenated

• Veins deoxygenated

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Cardiovascular Phyiology Goal

Circulation of blood

• Delivers oxygen and metabolic substrates to tissues

• Removes carbon dioxide and metabolic byproducts

In Cardiovascular Physiology, blood flow is driven by pressure gradients

• Driving force is rhythmic pumping of heart

• Modulated by constricting or dilating blood vessle sto change their resistance to flow

Phases of Cardiac Cycle

• Phase 1: Diastole

• Phase 2: Systole

• Phase 3: Systole

• Phase 4: Diastole

Phase 1

• Diastole

• Opening of AV valves

• Ventricular filling and atrial contraction

Phase 2

• Systole

• Closing of AV valves

• Isovolumetric ventricular contraction

  • All valves closed

Phase 3

• Systole

• Opening of pulmonic and aortic valves

• Ventricular ejection

Phase 4

• Diastole

• Closing of pulmonic and aortic valves

• Isovolumetric ventricular relaxation (all valves closed)

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3 equations

1. Blood pressure (BP)

2. Cardiac Output (CO)

3. Stroke Volume

Blood Pressure (BP)

Cardiac Output (CO) x Total Peripheral Resistance (TPR)

Cardiac Output (CO)

Heart Rate (HR) x Stroke Volume (SV)

Stroke Volume

Preload Contractility - Afterload

Preload

The load imposed on the heart prior to systole (end dystolic volume)

Contractility

Number of actin-myosin interactions during systole (intracellular calcium)