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

Artery Vein

Veins

• 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 open

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