Chapter5

Veins

Veins carry blood back to the heart. Veins have much thinner walls than arteries, causing them to collapse easily. The veins also have valves that allow the blood to move only toward the heart. These valves prevent blood from backflowing, ensuring that blood always flows toward the heart. The two large veins that enter the heart are the superior vena cava, which carries blood from the upper body, and the inferior vena cava, which carries blood from the lower body. Blood pressure in the veins is much lower than in arteries. Muscular action against the veins and skeletal muscle contractions help in the movement of blood.

cardiomyopathy

heart muscle disease can be caused by alcohol abuse, parasites, viral infection and congestive heart failure.

Cardiovascular System

-Maintains the distribution of blood throughout the body. -Composed of the heart, blood, vessels, arteries, capillaries, and veins.

infarct

An area of tissue within an organ or part that undergoes necrosis (death) following the loss of its blood supply.

angiospasm

An involuntary muscle contraction of the smooth muscle in the wall of a vessel; narrows the vessel

Blood Vessels

Arteries, capillaries, and veins; these are the pipes that circulate blood throughout the body. The lumen is the channel within these vessels through which the blood flows.

Capillaries

Capillaries are a network of tiny blood vessels referred to as a capillary bed. Arterial blood flows into a capillary bed, and venous blood flows back out. Capillaries are very thinned walled, allowing for the diffusion of the oxygen and nutrients from the blood into the body tissues. Since capillaries are so small in diameter, the blood will not flow as quickly through them as it does through the arteries and veins. This means that the blood has time for an exchange of nutrients, oxygen, and waste material to take place. As blood exits a capillary bed, it returns to the heart through a vein.

bundle branch block

Occurs when the electrical impulse is blocked from traveling down the bundle of His or bundle branches. Results in the ventricles beating at a different rate then the atria. Also called a heart block.

congestive heart failure

Pathological condition of the heart in which there is a reduced outflow of blood from the left side of the heart because the left ventricle myocardium has become too weak to efficiently pump blood. Results in weakness, breathlessness, and edema.

palpitations

Pounding, racing heartbeats.

Blood Flow through the Heart

The flow of blood through the heart is very orderly. From the heart to the lungs, it receives oxygen. Then goes back to the heart; and then out to the body tissues and parts.

Heart Chambers

The heart is divided into four chambers or cavities; two atria, or upper chambers. Two ventricles, or lower chambers. These chambers are divided into right and left sides by walls called the interatrial septum and the interventricular septum. -Atria- are the receiving chambers of the heart. Blood returning to the heart via veins first collects in the atria. -Ventricles- Are the pumping chambers. They have a much thicker myocardium and their contraction ejects blood out of the heart and into the great arteries.

Conduction system of the heart

The heart rate is regulated by the autonomic nervous system; we have no control over our heart beats. Special tissue within the heart is responsible for conducting an electrical impulse stimulating the different chambers to contract in the correct order. -Sinoatrial node- Is where the electrial impulses begin. -Arioventricular node- is stimulated. This node transfers the stimulation wave to the atrioventricular bundle. Bundle of HIS. The electrical signal next travels down the bundle branches within the interventricular septum. The purkjie fibers out in the centricular myocardium are stimulated, resulting in ventricular systole.

ischemia

The localized and temporary deficiency of the blood supply due to an obstruction to the circulation.

embolus

The obstruction of a blood vessel by a blood clot that has broken off from a thrombus somewhere else in the body and traveled to the point of obstruction. If it occurs in a coronary artery, it may result in a myocardial infarction.

orthostatic hypotension

The sudden frop in blood pressure a person experiences when standing straight up suddenly.

Arteries

They are large, thick-walled vessels that carry the blood away from the heart. The walls of arteries contain a thick layer of smooth muscle that can contract or relax to change the size of the arterial lumen. The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs. The largest artery, the aorta, begins from the left ventricle of the heart and carries oxygenated blood to all the body systems. The coronary arteries then branch from one aorta and provide blood to the myocardium. As they travel through the body, the arteries branch into progressively smaller sized arteries. The smallest of the arteries, called arterioles, deliver blood to the capillaries.

regurgitation

To flow backwards. This refers to the backflow of the blood through a valve.

plaque

A yellow, fatty deposit of lipids in an artery.

Heart

-Cardiac muscle fibers considered a muscle rather than an organ. -Beats an average of 60-100 beats per minute or about 100,00 per day. -Each time the (cm) contracts, blood is ejected from the heart and pushed throughout the body within the blood vessels. -The heart is located in the mediastinum in the center of the chest cavity but it is not exactly centered but more of the heart is on the left side of the mediastinum than the right. -The heart is the side of a fist and shaped like an upside-down pear and the heart lies directly behind the sternum. -The tip of the heart at the lower edge is called the apex.

Circulatory System (Cardiovascular System)

-Composed of two parts; pulmonary circulation and the systemic circulation. -Pulmonary Circulation- Between the heart and lungs, transports deoxygenated blood to the lungs to get oxygen and then back to the heart. -Systemic Circulation- Carries oxygenated blood away from the heart tissues and the cells, then back to the heart. -Cardiovascular system also collects waste products from the bodies cells.

Heart Layers

-The wall of the heart is quite thick and composed of three layers. -Endocardium- Is the inner layer of the heart lining the heart chambers. Very smooth, has a thing layer that serves to reduce friction as the blood passes through the heart chambers. -Myocardium- Is the thick, muscular middle of the heart. Contraction of this muscle layer develops the pressure required to pump blood through the blood vessels. -Epicardium- Is the outer layer of the heart. The heart is enclosed within a double-layered pleural sac, called the pericardium. The epicardium is the visceral pericardium, or inner layer of the sac. The outer layer of the sac is the parietal pericardium. Fluid between the two layers of the sac reduces friction as the heart beats.

thrombus

A blood clot forming within a blood vessel. May partially or completely occlude the blood vessel.

congenital septal defect

A hole, present a birth, in the septum between two heart chambers; results in a mixture of oxygenated and deoxygenated blood.

murmur

A sound, in addition to the normal heart sounds, arising from blood flowing through the heart. This extra sound may or may not indicate a heart abnormality.

cardiomegaly

An enlarged heart.

cardica arrest

Complete stopping of heart activity

angina pectoris

Condition in which there is severe pain with a sensation of constriction around the heart. Caused by a deficiency of oxygen to the heart muscle.

Blood Flow through the Heart

Deoxygenated blood from all the tissues in the body enters a relaxed atrium via two large veins called superior vena cava and inferior vena cava. The right atrium contracts and blood flows through the tricuspid valve into the relaxed right ventricle. The right ventricle then contracts and blood is pumped through the pulmonary valve into the pulmonary artery, which carries it to the lungs for oxygenation. The left atrium receives blood returning to the heart after being oxygenated by the lungs. This blood enters the relaxed left atrium from the four pulmonary veins. The left atrium contracts and blood flows through the mitral valve into the relaxed left ventricle. When the left ventricle contracts, the blood is pumped through the aortic valve and into the aorta, the largest artery in the body. The aorta carries blood to all parts of the body. The period of time that a chamber is relaxed is diastole. The contraction phase is systole.

Heart Valves

Four valves acts as restraining gates to control the direction of blood flow. They are situated at the entrances and exits to the ventricles. -Tricuspid valve- An atrioventricular valve, meaning that it controls the opening between the right atrium and the right ventricle. Once the blood enters the right ventricle, it cannot go back up into the atrium again.This valve has three leaflets or cusps. -Pulmonary valve- a semilunar valve. The prefix semi, meaning half, and the term lunar, meaning moon, indicate that this valve looks like a half moon. Located between the right ventricle and the pulmonary artery, this valve prevents blood that has been ejected into the pulmonary artery from returning to the right ventricle as it relaxes. -Mitral valve- also called the biscupid valve, indicating that it has two cusps. Blood flows through this atrioventricular valve to the left ventricle and cannot go back up into the left atrium. Airtuc valve- a semilunar valve located between the left ventricle and the aorta. Blood leaves the left ventricle through this valve and cannot return to the left ventricle.

endocarditis

Inflammation of the lining of the heart.

Coronary artery disease

Insufficient blood supply to the heart muscle due to an obstruction of one or more coronary arteries. May be cause by atheroscierosis and may cause angina pectoris and myocardial infarction.

arrhythmia

Irregularity in the heartbeat or action. Comes in many forms. None and life threatening.

Pulse and Blood Pressure

Is a measurement of the force exerted by blood against the wall of a blood vessel. During ventricular systole, blood is under a lot of pressure from the ventricular contraction, giving the highest blood pressure reading- the systolic pressure. Pulse could be felt at the wrist or neck, caused by the heart contracting and the pulse is equal to the heart rate. Ventriular diastole, blood is not being pushed by the heart at all and the blood pressure reading drops to its lowest point- the diastolic pressure. Therefore, to see the full range of what is occurring with blood pressure, both numbers are required. Blood pressure is also affected by several other characteristics of the blood and the blood vessels. Including the elasticity of the arteries, the diameter of the blood vessels, the viscosity of the blood, the volume of blood flowing through the vessels, and the amount of resistance to blood flow.

tachycardia

The condition of having a fast heart rate

bradycardia

The condition of having a slow heart rate.

angiostenosis

the narrowing of a vessel