The cardiovascular System
The function of the cardiovascular system is to delivery oxygen and nutrients and to remove
carbon dioxide and other waste products
Transport of substances such as:
Oxygen & nutrients to cells
Wastes from cells to liver and Kidneys
Hormones, immune cells, clotting proteins to specific target cells
Aclosed system of the heart and blood vessels
The heart pumps blood
Blood vessels allow blood to circulate to all parts of the body
Blood is used for delivery
Overview of the cardiovascular System
Located in the thoracic cavity
Diaphragm separates abdominal cavity form thoracic cavity
Size of first
Weights approximately 250-350 grams
Valves present for unidirectional blood flow
Valves prevent backflow
Four chambers: 2 atria and 2 ventricles
Blood Vessels Blood
Muscle generates more force so the heart needs to generate more force to pump the blood
through the whole body. Left side also has more musculature.
Properties of Cardiac Muscle
Gap Junction: so heart contracts as a unit
Electricity can pass through these sells and creates one uniform contraction
Desmosomes: resist Stress
Specialized junctions that hold cells together.
No cell division after infancy – growth by hypertrophy
You can’t replace Heart cells.
Heart grows through mass (hypertrophy)
99% contractile cells
1% autorhythmic cells
Creates a rhythm to beat on it’s own
Heart is set to beat at 100 bpm but nervous system and endocrine system adjust the bpm based on
what is appropriate for their metabolic needs
The heart’s Covering: The pericardium
Pericardium is a double-walled membranous sac surrounding heart
Serous fluid fills the space between the layers of pericardium
Lubricates heart decreasing friction
Prevents blisters because of the covering Covering keeps the heart moist.
Pericarditis = inflammation of pericardium
The Heart: 4 Chambers
Right and Left side act as separate pumps
Septa: Separates chambers
Separates the two ventricles
Separates the two atria
Atria are receiving chambers
Ventricles are discharging chambers
The Heart: Valves
Allow blood to flow in only one direction to prevent backflow
Atrioventricular (AV) valves are between atria and ventricles
Bicuspid (mitral) valves (left side of heart) 2 flaps: named after a pop’s hat
Tricuspid Valve (right side of the heart)
Semilunar valves are between ventricle and artery
Pulmonary semilunar valve
Aortic Semilunar Valve
The Heart: Valves
Anchored in place by chordae tendinae (“Heart strings”)
Gives the heart it’s unique shape. It’s shape helps blood leave the heart.
Open during heart relaxation and closed during ventricular contract
Closed during heart relaxation but open during ventricular contraction
When one set it open, the other set is closed. This is known as complimentary Valves
These valves operate opposite of one another to force a one-way path of blood through the heart.
Valves and Unidirectional Blood Flow
Pressure within chambers of heart vary with heartbeat cycle
Pressure differences drives blood flow: high pressure to low Pressure
Movement of blood pushes the valves open
Normal direction of flow Veins to atria
Atria to ventricles
Ventricles to arteries
Valves prevent backward flow of blood
All valves open passively based on pressure gradient
The farther you get from the heart, the lower the blood pressure. Highest BP is in the heart
Heart arteries arterioles capillaries venules Veins (Then starts again)
Arteries are relatively large, branching vessels that conduct blood away from the heart
Arterioles are small branching vessels with high resistance
Branching of Arteries
Capillaries are site of exchange between blood and tissue
Capillaries: only site of gas Exchange
Venules are small converging vessels
Veins are relatively large converging vessels that conduct blood to the heart
By the time we’re in the veins, there is no blood pressure.
Movement (skeletal muscle pump) moves the blood from the veins back to the heart
Doesn’t matter when people are sleeping because they are horizontal and the subtle movements
People with paralysis: They have problems, They need to go to PT so that they can move the
Pressure drives blood Flow Series flow through the Cardiovascular System
Parallel Flow within the systemic or Pulmonary Circuit
Supplied by right Heart
Blood vessels from heart to lungs and lungs to heart
Systemic Circuit has higher pressure from the heart because the entire body needs blood and so
the heart has to get it there.
Supplied by left heart
Blood vessels from heart to systemic tissues and tissues to heart
Not all arties carry oxygenated Blood
Arteries LeadAWAY from the heart
PulmonaryArteries are deoxygenated.
Left Ventricle aorta system circuit venae cavae right atrium right ventricle Pulmonary
artery Pulmonary Circuit pulmonary veins left atrium left ventricle
Oxygenation of blood
Exchange between blood and tissue takes place on capillaries
Blood entering lungs = deoxygenated blood
Oxygen diffuses from tissue to blood
Blood leaving lungs = oxygenated blood
Blood entering tissues = oxygenated blood
Oxygen diffuses from blood to tissue Blood leaving tissues = deoxygenated blood
Only site of gas exchange is capillaries
Thin walls for diffusion of gases
Gases: Oxygen and CO2
Oxygen comes in and CO2 leaves the blood stream
Oxygen goes out of the blood and CO2 leaves the blood stream
Why do we need Oxygen
Oxygen Phosphorylation: MakesATP so we can use this energy
Certain cells needs moreATP
Intrinsic conduction system (nodal system): heart muscle cells contract, without nerves impulses,
in a regular continuous way.
Blood in the heart chambers does not nourish the myocardium
The heart has its own nourishing circulatory system consisting of
Coronary arteries branch from the aorta to supply the hear muscle with oxygenated blood
Cardiac veins drain the myocardium of blood
Coronary sinus, a large vein on the posterior of the heart, receives blood from cardiac veins
Blood empties into the right atrium via the corony sinus
Done through stents where they uses vessels from other places to completely bypass the current
vessel. Usually the current vessel has plaque or cholesterol buildup which is why it needs bypas
Multiple stents is named after the number of stents.
Quadruple bypass (4 stents)
After about 4 they may have to use veins instead of the arteries
Also hard to find arteries at that point which aren’t clogged
Differences between blood vessels
Wall of theArteries are the thickest
Arteries are under the highest pressure.
Strong muscular vessels.
This allows them to resist the force that the heart generates
Lumens of veins are larger
Larger veins have valves to prevent backflow
Skeletal muscle squeezes blood in veins toward the heart
Walls of capillaries are only one cell layer thick to allow for exchange between blood and tissue
Blood Vessels; MicroscopicAnatomy
Three Layers (Tunics)
Tunica Intima: endothelium
Controlled by sympathetic nervous system
Radius can be altered may be used to control blood flow to individual capillary beds Used to regulate mean arterial pressure.
Tunica externa is mostly fibrous connective tissue
Rapid Transport Pathway, large diameter – little resistance
Walls contain elastic fibrous tissues, under high pressure
Smooth muscle regulates radius
Aorta: Leaves left ventricle
PulmonaryArteries: Leave right ventricle
Site of exchange between blood and tissue
Substances exchanged due to concentration gradients
Oxygen and nutrients leave blood.
Carbon Dioxide and other wastes leave the cells
They are ready to leave the cell
Walls are 1 cell layer, small diffusion barrier
10-40 billion per body, total surface area 600 m^2
Most cells within 1 mm of a capillary
Cartilage: not a very good blood supply.
Eyes:Aren’t as vascularized
Have direct gas exchange for one’s skin Exchange of nutrients through eyelids to the eyes.
Can’t have blood vessels covering eye because then we couldn’t see
Pores between endothelial cells, protein free plasma moves through pores
Did allow leukocytes to but also allow proteins to as well.
Capillary Exchange: Mechanisms
Direct diffusion across plasma membranes
Endocytosis or exocytosis
Some capillaries have gaps (intercellular clefts), plasma membrane not joined by tight junctions
Fenestrations (pores of some capillaries)
Fluid Movements at capillary beds
Blood pressures forces fluid and solutes out of capillaries
Osmotic pressure draws fluid into capillaries
Blood Pressure is higher than osmotic pressure at the arterial end of the capillary bed
Blood pressure is lower than osmotic pressure at the venous end of the capillary bed.
Blood vessels push out too much blood and not the same amount coming back in
Results in edema because of this
Push out more fluid than how much that comes in.
Parallel line for Osmotic Pressure
Rings of smooth muscle that surround capillaries on the arteriole end Contract/relax in response to local factors only
Contraction constrict capillary decrease blood flow
Relaxation increases blood flow
Metabolites (waste products) cause relaxation
If one is metabolically active, a lot of waste is created.
CO2 will open the sphincters (relaxation of the sphincters)
Capillary beds consist of two types of vessels
Vascular shunt – vessel directly connecting an arterioles to venules
If there is backflow, the capillaries will not get blood and the blood will just run through shunts
Blood just needs to get back to the veins so it uses the shunt in order to get blood back to veins.
True capillaries – exchange vessels
Oxygen and nutrients cross to cells
Carbon dioxide and metabolic waste products cross into blood
Factors affecting filtration and absorption across capillaries
increase blood volume and thus blood pressure
Decrease in plasma proteins
Frothy Urine is a sign of this because you may be urinating proteins
Heart Disease pulmonary edema
Seen first because it is closer to the heart Pulmonary circuit is under lower pressure than the systemic circuit
Liver Disease Decrease in plasma proteins
Factor that influence central venous pressure and venous return
Large diameter, but thin walls
Valves allow unidirectional blood flow.
Veins are a volume reservoir because of a high Compliance
Compliance is a measure of how the pressure of a vessel will change with a change in volume
Low compliance arteries: small increase in blood volume causers a large increase in pressure
High Compliance (veins): large increase in blood volume required to produce large increase in
Veins expand with little change in pressure and function as blood reservoir
60% total blood volume in system veins at rest, veins hold large volume with small pressure
change due to high compliance
Volume that Veins have is about 3.5 times larger than how much volume arteries can hold
Compliance: How easy is it to stretch (measured through pressure)
The skeletal muscle Pump
Most arterial blood is pumped by the heart
Veins use the milking action of muscles to help move blood
One-way valve in peripheral veins
Skeletal muscle contracts
Squeezing on veins increased pressure ( blood actually goes both ways but valves prevent
backflow so it turns into unidirectional muscle) Blood moves toward heart
Blood cannot move backwards due to valves
Skeletal muscle relaxes
Blood flows into veins between muscles
People need movement.
The Heart: Conduction System
Special tissue sets the pace
Sinoatrial node = SAnode (“Pacemaker”), is in the right atrium
Atrioventricular Node =AV node, is at the junction of the atria and ventricles
Atrioventricular bundle =AV bundle (bundle of His), in in the interventricular septum
Bundle branches are in the interventricular septum
Purkinje fibers spread within the ventricle wall muscles.
Atria contract as a unit and then ventricles contract as a unit
Atrial Contraction precedes ventricle contraction
Auto-rhythmicity is the ability to generate own rhythm.
Autorhythmic cells that provide pathway to spread excitation through the heart
Sinoatrial node is the pacemaker of the heart
Blood into ventricles
Then the message goes to the atrioventricular node Excites Ventricles
Alot more electrical wires going through ventricles
This makes sure the ventricles contract
Waves of contraction through cardiac muscle
Special Tissue sets the pace
Sinoatrial node = SAnode (“Pacemaker”), is in the right atrium
Excites the atrium and excites theAV node
Action potential spread through theAV bundle in order to get through the tough cardiac muscle
Atrioventricular node =AV node, is at the junction of the atria and ventricles
Atrioventricular bundle =AV bundle (bundle of His), is in the interventricular septum
Gap Junctions also allow electrical signals to spread.
Bundle branches are in the interventricular septum
Purkinje fibers spread within the ventricle wall muscles
Control of heart beat by pacemakers
Auto-rhythmic cells have pacemaker potentials
Heart sets it’s own stimulus: Funny Channels. These channels let in sodium themselves.
When sodium goes in, it open voltage gated channels. T-Type Channels
These T-Type channels open and allow calcium in.
Threshold:Action Potential: When the L=type calcium channels open Calcium moves in
Spontaneous depolarization caused by closing K+ channels and opening of cation channels
Channels that open:
If channels: NA+ moves in, net depolarization, then Ca2+ T channels: Further depolarization
Car+ L Channels cause the action potential
The Resting Membrane Potential
Resting potential is caused by the membrane’s ability to maintain a positive charge on its outer
surface opposing a negative charge on its inner surface.
Maintains a concentration gradient by having potassium inside the cells, and sodium outside the
K+ leak channels allow potassium to leave the cell.
It leaves down it’s concentration gradient and leaves behind negatively charged proteins. The
inside of the cell becomes more and more negative.
-70mV is equilibrium in cells
Form this a concentration gradient is created because it is potential energy
If sodium moves into the cell (selectively), electricity comes in.
Calcium does the same thing, it enters the cell and also can create electricity as it comes into the
Resting Potential = Potential Energy
Action potential: Stimulus – activate and allow sodium to flow into the cell and create electricity
Thinking about something causes it to activate.Acetylcholine receptors start the neurons in order
to start the sodium channels that open up.
Stimulus is thinking
Once you open and hit a particular potential, a create amount of sodium channels open and
creates an action potential.
Returns to RMP Known as Repolarization
ElectricalActivity in pacemaker Cells
Depolarize to threshold with funny channels and T Type Ca2+