Compendium 6 Flashcards
The cardiovascular system
- Transports fluids, nutrients, waste products, ages and hormones throughout the body
- Exchange materials between blood, cells and extracellular fluid
- Plays a role in the immune response, blood pressure and the regulation of the body temperature
- Consists of the heart, blood vessels, capillary beds and blood
The heart – function
- Generating blood pressure -moves blood through vessels
- Routing blood: separates pulmonary and systemic circulations
- Ensuring one-way blood flow
- Regulating blood supply
- Changes to match need
The heart – “2 pumps in 1”
This is because the right side of the heart acts to receive blood that is coming from the body so its low in oxygen, it will come into the heart on the right side, it is pumped through the right side of the heart and then it will go into pulmonary circulation so essentially it will go to the lungs to pick up oxygen and the left side of the heart, the other side of the pump receives freshly oxygenated blood form the lungs, it pumps it through the left side of the heart and then into systemic circulation where it will deliver oxygen to body tissues and to body cells
The heart – location
- Size of a closed fist
- Shape
Apex – blunt rounded point of cone – bottom/ most inferior
Base—flat part at the opposite end of cone—is actually superior - Located in thoracic cavity in mediastinum
The heart – pericardium
Fibrous pericardium
- Connective tissue
- Tough fibrous outer layer
- Prevents overfilling or over distention of the heart
- Acts as to anchor the heart
Serous pericardium
- Thin
- Transparent
- Inner layer
- Simple squamous epithelium
Parietal pericardium – lines the fibrous outer layer
Visceral pericardium – covers heart surface
Pericardial fluid reduces friction as heart is moving or beating which is between the two
The heart – wall
Three layers of tissue
1. Epicardium – most outer
Serous membrane; smooth outer surface of heart
2. Myocardium – middle layer
Middle layer composed of cardiac muscle cells – contractility
Reason for the pump (contraction)
3. Endocardium – most inner
Smooth inner surface of heart chambers
Pectinate muscles
- Muscular ridges in auricles and right atrial wall
Trabeculae carnae
- Muscular ridges and columns on inside walls of ventricles
The heart – chambers
Atria – superior and slightly posterior
Right atrium
- Three major openings to receive blood returning from the body
- Inferior vena cava, superior vena cava and the coronary sinus (vein that brings deoxygenated blood to heart) are the 3 openings
- Heart own blood service through coronary sinus
Left atrium
- Four openings that receive blood from pulmonary veins
- Most superior chamber
- Received oxygenated blood from the lungs
- Left and right pulmonary veins, because 2 openings for each makes 4
Ventricles – inferior
Atrioventricular canals – openings between atria and respective ventricles and where you will find atrioventricular valves
- Right atrioventricular valve or the tricuspid valve
- Left atrioventricular valve or the bicuspid valve
Right ventricle- opens to pulmonary trunk
Left ventricle- opens to aorta – very muscular wall
Interventricular septum – between the two ventricles
So blood will flow from the atrium into the ventricle on on either side of the heart.
So when talking about the right side of the heart, blood will go through the right atrium through the right atrioventricular valve into the right ventricle, when it exits the right ventricle blood will move up through the pulmonary trunk and from here it will go to the lungs.
On the left side of the heart as the blood comes in, oxygenated blood comes in from the lungs. Oxygenated blood will move through the left atrioventricular valve into the left ventricle. It will then move from the left ventricle up through the aorta and the aortic arch, blood will go into systemic circulation
The heart – valves
Cusps = flaps
Atrioventricular valves (AV valves)
Each valve has leaf-like cusps that are attached to cone-shaped papillary muscles by tendons (chordae tendineae)
Right has three cusps (tricuspid
left has two cusps (bicuspid, mitral)
When valve is open, blood flows from A -> V
When it is closed, blood exits ventricle
Semilunar valves- right is pulmonary, left is aortic
Each cusp is shaped like a cup
When cusps are filled, valve is closed – stops backflow
When cusps are empty, valve is open – blood exits heart
Blood vessels overview
Arteries - Elastic, muscular, arterioles - Take blood away from the heart - Contain blood under pressure - Thicker walls Capillaries - Site of exchange with tissues (interstitial fluid) - small Veins - Large, medium, small, venules - Take blood to the heart - Thinner walls wall than arteries - Contain less elastic tissue - Less smooth muscle - Valves to prevent backflow
Blood vessels – arteries and veins
The wall of blood vessels both consist of the same 3 layers in their wall
- Tunica intima – endothelium (a thin layer of epithelium)
- Tunica media – smooth muscle cells arrange circularly around the blood vessels
- Vasoconstriction- smooth muscle contracts, decrease in blood flow
- Vasodilation- smooth muscle relaxes, increase in blood flow - Tunica externa (adventitia)- connective tissue
Blood vessels – capillaries
- Capillary beds – extensive networks for exchange
- Wall consists of endothelial (simple squamous epithelium), basement membrane and a delicate layer of connective tissue
- Substances move through capillaries through diffusion
Blood – functions
Transport – gases, nutrients, waste products, processed molecules, hormones, enzymes
Blood - composition
Considered a connective tissue mad eup of a liquid matrix (the plasma) which makes up about 55% of the blood volume
- Plasma consists mainly of water and other substances such as proteins, ions, nutrients and gases that have been dissolved in the plasma
Formed elements
Red blood cells, white blood cells, platelets which makes up about 45% of blood volume
Blood – red blood cells
No nucleus and bi-concave shape to increase SA and thus oxygen carrying capacity
Oxygen from lungs to blood vessels: 98.5% attached to haemoglobin protein 1.5% dissolved in plasma
They contain a protein called haemoglobin which oxygen attaches to in order to be transported
Why do we need a CVS
Transports
- Humans are multicellular
- All cells around body need a constant supply oxygen and nutrients, and constant removal of waste products
- We need a circulating fluid for transportation
- Exchange materials between blood, cells and extracellular fluid (interstitial)
- Blood and blood vessels
- Capillaries – exchange
Pump
- Generating blood pressure – moves blood through vessels
- Routing blood – separates pulmonary and systemic circulations
The heart – pulmonary circulation
Gas exchange in the lungs
Deoxygenated blood that has returned from all body cells or body tissues enters the right atrium and flows down through the atrioventricular valve into the right ventricle. As thee right ventricle contracts blood flows into the pulmonary trunk and exits the heart. The pulmonary trunk divide into left and right pulmonary arteries which carry blood away from the heart and towards the right and left lung. Once blood is in the alveoli of the lung gas exchange takes place and due to the differences of partial pressures in oxygen and the partial pressure of carbon dioxide, oxygen is going to flow into the blood from the alveoli and carbon dioxide is going to flow out of the blood into the alveoli where it exits the body during exhalation.
One gas exchange has occurred
The oxygenated blood is going to travel in the left or right pulmonary veins and go back to the left atrium
The heart – systemic circulation
Capillary exchange in body/ cells
Oxygenated blood enters the left atrium and will flow through the left atrioventricular valve into the left ventricle. As the left ventricle contracts blood flows out of the heart through the aorta. Aorta branches into 3 large vessels, the ascending aorta, aortic arch and descending aorta and its these 3 vessels which essentially take blood both up and down the body, so blood goes all around the body for capillary exchange in the tissues so blood is delivered to all the cells and tissues in the body for gas/nutrients/fluid exchange- where these 3 are exchanged between the blood and the interstitial fluid that’s surrounding the cells. Once capillary exchange has taken place blood travels back to heart via veins and re-enters right atrium through both the inferior and superior vena cava.
The heart- blood flow
Both types of circulation work together
Process:
(1) Blood enters the right atrium through the superior and inferior vena cava its then going to flow through the right AV valve which is the tricuspid valve
(2) Blood flows into right ventricle, and as this right ventricle contracts
(3) Blood flows through the pulmonary semilunar valve which is located in the pulmonary trunk which then divides into
(4) the left and right pulmonary arteries and this is where blood will travel to the lungs
(5) Oxygenated blood now coming back to heart, blood re-enters the left side through the left and right pulmonary veins
(6) Blood flows into left atrium.
(7) Blood will then flow through the left atrioventricular valve or the bicuspid valve into the left ventricle. When this contracts..
(8) Blood moves through the aortic semilunar valve in the aorta then blood will exit the heart and travel through the blood vessels in the CVS to all the cells in the body and then will travel to the capillary beds which will allow for exchange of fluid/ nutrients/ gases out of the blood into the interstitial and then from here will be picked up by the cells
The heart – cycle and control
Contraction of the heart produces the pressure
- Which is responsible for moving blood through the heart and out through the circulatory system to areas of lower pressure
- Blood will move around the body by the pressure generated by the heart
Cardiac cycle
- Repetitive contraction (systole) and relaxation (diastole) of heart chambers – moves blood through the heart and body
- Contraction followed by relaxion, bloods enters heart when relaxed
Blood flow is proportional to metabolic needs of tissues
- Brain, kidneys, liver, exercising skeletal muscle – very high
Can increase or decrease amount of blood its pumping out
Cardiac output = heart rate X stroke volume
Cardiac output- amount of blood coming out of the heart per minute
Heart rate- beats per minute
Stroke volume- amount of blood being ejected by the ventricles with each beat
Nervous system and endocrine system (hormonal control) can influence the heart
Nervous system
- Maintains blood pressure and thus blood flow and can also reroute blood flpow when required
- E.g. increase blood flow during exercise
- E.g. injury rerouting blood towards needed area
Hormonal control
- Epinephrine (adrenaline) from adrenal glands – increases HR and SV
The heart – conducting system
Action potential – a rapid change in membrane potential, acts as an electrical signal / impulse
The heart can generate its own action potentials
Auto-rhythmicity – repetitive contraction
Sinoatrial node (SA) – pace maker — can generate its own action potential which spreads to ventricles
Atrioventricular (AV)
Action potential spread through the conducting system of the heart to all cardiac muscle cells – as a result the cardiac muscles contract. Blood is pumped
Capillary exchange
Cells are bathed in interstitial fluid (extracellular matrix) Constant transport (diffusion) in and out of cells – requires a pressure gradient Needs constant turnover/ freshening Comes via capillaries and CVS Capillary exchange - The movement of substances into and out of capillaries. How cells receive what they need to survive and eliminate waste products Most important means of exchange: diffusion - Oxygen, hormones, nutrients can diffuse from a high concentration in the capillary to low concentration in the interstitial fluid Lipid soluble molecules can diffuse through the plasma membrane of endothelial cells (O2, CO2, steroid hormones, fatty acids). Water soluble molecules diffuse through intercellular spaces or fenestrations (gaps) of capillaries, glucose, amino acids.
Depending on where the capillary beds are and where this exchange is taking place capillaries can be very leaky and allow whole cells to pass through or can be very strict and allow very small molecules to pass through
Large spaces between endothelial cells- proteins and whole cells can pass e.g. liver or spleen
Very small spaces between cells – very few molecules can pass e.g. blood brain barrier
Capillary permeability, blood pressure, and osmotic pressure affect movement of fluid form capillaries
The lymphatic system
Fluid move out of capillary into the interstitial fluid (intercellular) space and most returns to capillaries
The fluid which remains (1/10) in tissues is picked up by the lymphatic system then eventually returned to venous circulation
