Cardiovascular Functions and Components

Functions

• distributing what we need and discarding toxins

• facilitates exchange

• enhances communication

• establishes defense

Muscular Pump Basics

• located in the thoracic cavity

• 4 chambered heart

• 2 atria and 2 ventricles

Heart Basics

• the heart is on the ventral side of the thoracic cavity, tilted to the right and between the lungs

• heart is enclosed by pericardium filled with fluid for physical protection and lubrication

• cardiac tamponade: buildup of pericardial fluid within the pericardial sac causing a decrease in cardiac output

• the ventricles occupy the bulk of the heart with the epicardial coronary arteries and veins running along the sulci (groove) of the heart

Fibrous Rings of Heart

• fibrous dense connective tissue rings separating atria from ventricles

• 4 rings that surround the valves of the heart, forming the structural foundation of the heart valves

• they fuse with one another and merge with the inter-ventricular septum

• fibrous rings function as an electrical insulator, preventing the propagation of electrical impulse from atria to ventricles through contractile myocytes

Pace Maker and Conducting Systems

• 2 basic sets of intrinsic pacemaker tissues in the heart

• SA node and AV node

• ectopic focus: any part of the heart other than the SA node that generates a heartbeat

• purkinje fibers have highest conduction velocity so they have fast and coordinated ventricular contraction

• AV node has lowest conduction velocity to ensure adequate ventricular filling and limits the frequency of ventricular activation

Heart Muscle (Myocardium)

• with various thicknesses (proportional to pressure generated)

• atria < right ventricle < left ventricle

• Intercalated disk: forms tightly coupled structure with neighboring cells

• gap junction: forms electrical synapse with low resistance

• with these two things, cardiac muscle can contract as a unit with a single impulse

Heart Valves

• 4 sets of valves

• Atrium: 1 set

• Ventricle: 2 sets

• Aortic Valve and Pulmonary Valve are semilunar and have nothing attached so function by pressure gradient

• tricuspid valve has 3 tendons attached

• bicuspid valve (mitral) has 2 tendons attached

• prolapse: condition that the chordae tendineae fails and valve is pushed back into the atrium during ventricular contraction, giving rise to ventricular regurgitation

Coronary Circulation

• receives roughly 5% of the resting cardiac output

• most blood returns into the right atrium via coronary sinus

• blood enters the coronary arteries through the two coronary orifices located at the root of the aorta behind the right and left cusps of the aortic valves

Autonomic Innervation

• parasympathetic → negative chronotropic (rate)

• Sympathetic → positive chronotropic and inotropic (force)

• ANS modulates rather than initiates cardiac functions

Closed Loop

• cardiovascular system is a closed loop where the heart pumps blood through arteries into the capillary beds and veins carry blood back to the heart

Parallel Arrangement

• majority of organs are in parallel arrangement with 3 major portal systems

1. blood enters into the digestive tract and later reenters the liver

2. In kidney’s filtration system

3. hypothalamic-hypophyseal (pituitary) portal system

• this arrangement is to ensure adequate distribution of blood into all the organs and each organ will receive the same oxygenated arterial blood with approximately the same perfusion pressure

Distribution Networks

• arteries are known as resistance vessels

• veins are known as capacitance vessels (saggy elastic band)

• capillaries are the sites for exchange

• one of the most important functions of the blood vessels is volume and pressure regulation

Transport Medium (Blood)

• 5-6L in body

• plasma → 3 L (55% of total blood volume)

• plasma has electrolytes, plasma protein, carbohydrates, and lipids

• red blood cells → 45% of volume

• buffy coat: white blood cells and platelets