Cardiovascular System Anatomy and Physiology

Cardiovascular System Consists of heart—pump System of blood vessels --transport

Cardiovascular System Heart is covered by the pericardium This is like a thin membranous sac for protection

Cardiovascular System Heart has four chambers: 2 atria on top and 2 ventricles on the bottom Atria are receiving chambers Ventricles are pumping chambers, and have thicker walls

Cardiovascular System Heart is also divided into right and left Blood on the right side does not mix with blood on the left side Blood which enters the right atrium goes on to the right ventricle Enters left atrium; leaves left ventricle

Cardiovascular System Blood entering the right side of the body is coming from the veins of the body and is low oxygen It is sent from the right ventricle to the lungs

Cardiovascular System Blood entering the left side of the heart has come from the lungs and is oxygenated It is sent from the left ventricle through the arteries to all parts of the body

Cardiovascular System Valves separate the atria from the ventricles On the right side, it is the tricuspid valve On the left side, it is the bicuspid valve They close to prevent flow when it should be sealed off

Label the Heart

Pulmonary vs Systemic The pulmonary circuit goes from the right atrium to the right ventricle And then to the lungs, returning to the left atrium

Pulmonary vs Systemic Systemic circulation goes from the left atrium into the left ventricle And then to all body parts (oxygenated)

Initiating the Heartbeat The “pacemaker” system Involves specialized pockets of heart tissue which can initiate impulses The first pocket is called the S-A (sinoatrial) node

S-A node Initiates the heartbeat Is located in the right atrium Causes both atria to contract (small contraction to send blood into ventricles) Impulse also travels on fibers to the next specialized pocket

A-V Node The A-V node (atrioventricular) receives the impulse from the S-A node Located in the septum where the atrium meets the ventricle Impulse is relatively slow, allowing time for the ventricles to fill

A-V Node passes it on From the A-V node, the impulse goes to the A-V bundle (also called the Bundle of His) From there is branches into Purkinje fibers that enclose both ventricles

The Big Push When all the cardiac muscle cells receive the impulse, the ventricles contract together and powerfully. This is systole

Steps in Order SA node AV node AV bundle Bundle branches Purkinje fibers

Replacement If the SA node fails to keep a regular rhythm, an artificial pacemaker can be inserted.

ECG Electrocardiogram Sometimes called EKG Recording of electrical changes Records the electrical impulses of action potentials

The Blood Vessels Arteries lead away from the heart Arteries branch into arterioles (smaller arteries,) then into tiny capillaries Capillaries merge together to form venules (small veins) Venules merge to become larger veins which return blood to the heart

Arteries Strong Elastic Able to withstand the pumping pressure Three layers in the wall—one layer contains smooth muscle

Arteries The muscle allows the artery to constrict (reduce diameter) and dilate (increase diameter) This is important in maintaining body temperature

Capillaries Smallest diameter Connect the smallest arterioles with the smallest venules The wall is only one layer thick—very thin! Exchange of materials occurs here

Veins Venules merge to form larger veins Walls have three layers, but much thinner Less muscle and elastic tissue Collapse when empty

Artery and Vein Comparison

Veins Contain valves to prevent back flow Valves open Contain valves to prevent back flow Most valves are in veins of the limbs Harder to return blood from these parts, due to low pressure Valves closed

Valves Valves

Veins By the time blood gets to the veins, it has little force behind it. It’s hard to get blood back to the heart Valves help, but also skeletal muscle movement and respiration help

Blood Pressure Force blood exerts against the walls of the blood vessels. Primarily in the arteries, since they are subject to the most force Can feel a pulse in arteries

Blood Pressure Systolic pressure is the pressure during ventricular contraction Diastolic pressure is the pressure during ventricular relaxation A blood pressure reading is expressed as systolic pressure diastolic pressure

Blood Pressure A normal blood pressure reading is 120/80. Generally, lower is better Hypertension may result in heart enlargement, heart attack, atherosclerosis, stroke Exercise, controlling weight, limiting sodium, reducing stress, and medication are treatments for high blood pressure

Blood Pressure Factors affecting blood pressure include: Amount of blood pumped by the left ventricle and how often Blood volume Peripheral resistance Blood viscosity