Cardiovascular System Anatomy and Physiology
Dec 27, 2015
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
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
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
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
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