cardiovascular system Flashcards
what is the structure of elastic arteries
- large diameter
- thick wall
- close to heart (e.g aorta and pulmonary artery)
- tunica media has high elastin content in numerous concentric elastic laminae, , which can stretch and recoil to propel blood
- vasa vasorum for O2 and nutrient supply
what is the function of elastic arteries
conducting (ie they stretch in response to pulses to propel blood)
what is the structure of muscular arteries
- tunica media has more smooth muscle (for vasoconstriction and vasodilation)
- vasa vasorum in dense CT of tunica adventitia
- further from heart (e.g radial, femoral, brachial arteries)
what is the function of muscular arteries
distributing (ie they draw blood from the elastic arteries and branch into resistance vessels)
what is the function of venous valves
they prevent back flow by opposing and collapsing > unidirectional flow of blood
describe lymphatic vessels
- they start blind
- lymph drains into lymph nodes > transported back to heart
- have valves
what are the two types of circulation
pulmonary and systemic
what drives blood flow
pressure
what components does the systemic circulatory system consist of
aorta, muscular arteries, small arteries, arterioles, capillaries, venules, medium veins, large veins, IVC + SVC
what is the general wall plan of a blood vessel
tunica intima / tunica media / tunica adventitia
function of arteries
deliver blood from heart to tissue
function of veins
return blood from tissues to heart
tunica intima
- innermost
- endothelium (simple squamous epithelium, antithrombogenic)
- basement membrane
- CT
- IEL
tunica media
- middle layer (thickest in arteries)
- smooth muscle > luminal diameter
- elastic lamellae
tunica adventitia
- outermost (thickest in veins)
- fibrous CT (abundant collagen)
- EEL
- smooth muscle IN VEINS
- vasa vasorum (O2 supply and nutrients)
what are arterioles
resistance vessels
- thick wall relative to luminal diameter
- tunica media = most prominent > varies vessel diameter > regulates blood flow through capillaries
what are venules
collect blood from capillaries
- tunica intima reduced to only endothelium
- thin tunica media
- small venules have pericytes which are contractile cells that regulate blood flow through microvasculature
- large venules have smooth muscle and CT
what are medium veins
blood reservoir due to high capacitance
- thin wall and irregular lumen
- valves
- low muscle in tunica media
- tunica adventitia broadest
what are large veins
- no valves
- no IEL
- no EEL
- high collagen in prominent tunica adventitia prevents over distension
arteries VS veins
- high pressure VS low pressure
- pressure reservoir VS blood reservoir
- 100% blood capacity VS 30-70%
- no valves VS valves
- more muscle in media VS less muscle in media
- thinner adventitia VS thicker adventitia
- small lumen, thick wall VS large lumen, thin wall
what are capillaries
smallest vessels > site of exchange
what is the wall structure of capillaries
endothelium, basal lamina, pericytes
endothelial cells in capillaries
- thin to maximise exchange
- intercellular tight junctions
- pinocytotic vesicles (transport across endothelium)
what are the 3 types of capillaries
continuous, fenestrated, sinusoidal
describe continuous capillaries
no gaps between endothelial cells > slower exchange but more selective
describe fenestrated capillaries
interruptions in endothelium > extensive exchange b/w blood and tissue but w some limitations on particle size
faster exchange but less selective
describe sinusoidal capillaries
- larger diameter
- incomplete endothelium > large fenestrations
maximum exchange b/w blood and tissues
what is the function of blood
transport O2 and nutrients to tissues, remove waste products from tissues
what are the components of blood (and their functions)
- plasma (contains water for circulatory volume and medium for dissolved solutes, contains electrolytes for volume and pH regulation)
- RBC (carry O2)
- WBC (lymphocytes, monocytes, neutrohils, eosinophils, basophils > immune responses
- platelets (haemostasis)
outline the process of haematopoiesis
derived from pluripotent haematopoietic stem cells
1 - reduced O2 carrying capacity (to kidney)
2 - erythropoietin release into blood by kidneys > stimulates erythropoiesis in bone marrow
3 - new erythrocytes increase O2 carrying capacity of blood
4 - relieves initial stimulus triggered by erythropoietin secretion
outline the process of haemostasis
formation of platelet plug
1 - platelet adhere to + activated by exposed collagen at site of injury
2 - activated platelets release ADP and thromboxane
3 - these chemical activate more passing platelets (positive feedback loop as it enhances)
4 - newly activated platelets pile on and release more chemicals
5 - uninjured endothelium releases NO and prostacyclin > inhibit platelet aggregation > platelet plug confined to site of injury
clot dissolution
tPA acts on plasminogen to form plasmin which results in a fibrin cleavage ie clot dissolution
Where is the heart
In the thoracic cavity, inferior to the sternal angle, posterior to the sternum
Shape of the heart
‘Inverted cone’
Size of the heart
2nd to 5th intercostal spaces on the left
3rd to 6th intercostal spaces on the right
Functions of the heart
Right heart = receives deoxygenated blood from the body and pumps it towards the lungs
Left heart = receives oxygenated blood from the lungs and pumps it to the tissues in the body
What are the 4 chambers of the heart
Right atrium, right ventricle, left atrium, left ventricle
What does the right atrium consist of
Auricle / pectinate muscles / IVC / SVC / fossa ovalis / interatrial septum
What does the right ventricle consist of
Tricuspid valve / pulmonary valve / papillary muscles / interventricular septum
What does the left atrium consist of
4 pulmonary veins / left auricle / floor oval fossa
What does the left ventricle consist of
Ventricular walls / bicuspid valve / aortic valve / papillary muscles
What are the 3 surfaces of the heart
Diaphragmatic, pulmonary, sternocostal
Left coronary artery
Arises from left side of aorta
Branches into the left anterior descending artery and circumflex
LAD supplies blood to the front and bulk of the left ventricle
Circumflex supplies left atrium and back of left ventricle
Right coronary artery
Arises from the right side of the aorta
Supplies right atrium, right ventricle, bottom portion of left ventricle
Posterior descending artery supplies the back of the heart
What happens after blood is supplied to the heart
Blood drains into the coronary sinus which empties into the right atrium
What are the 3 walls of the heart
Endocardium / myocardium / epicardium ie visceral pericardium
What are the two types of valves
AV (atrioventricular) which are leaflets
SL (semilunar) which are cusps
Describe the structure of the endocardium
- in contact with blood as it is the innermost wall
- has subendothelial CT (collagen and elastin)
- can contain purkinje fibres
Describe the structure of the myocardium
- thick middle layer
- cardiac muscle
- vascular CT b/w muscle fibres
- abundant blood capillaries (due to high high high demand for O2)
Describe the structure of epicardium
- aka visceral pericardium
- outermost layer in contact with the pericardial cavity
- has mesothelium > lubricates for smooth contractions
- underlying CT (adipocytes, nerves, coronary vessels)
Describe the structure of the pericardium sac
- separated from the heart by the pericardial cavity
- keeps the heart in place and prevents overexpansion
- mesothelium covers surface facing pericardial cavity
- fibrous CT
Describe the structure of the heart valves
- dense CT core (fibrosa)
- either side of the core = endothelium
What are the features of the conduction system of the heart
SA node, AV node, bundle of his, bundle branches, purkinje fibres
How does the conduction system of the heart work
SA node has the ability to generate 60-100APs/min (due to pacemaker cells), meaning that before the others (ie AV node, bundle of his etc) can generate their own APs, they are already activated by the APs from SA node
Where is SA node
Right atrium
Where is AV node
Right atrium
Where is bundle of his
Next to the tricuspid valve in the right atrium
Where is bundle branches
Interventricular septum
Where is purkinje fibres
Runs subendocardial
AP in pacemaker cells
- slow entry of Na+ > depolarisation
- Ca2+ transient channels open > depolarisation
- Ca2+ L type channels open > depolarisation
- > AP
- K+ channels open > hyperpolarised
How does AP of SA node work
- depolarise SA node
- SA node
What is MAP an indication
How well perfused the periphery of the tissue are ie is there sufficient blood going to the organs
(1/3 x PP) + diastolic
What is pulse pressure indicative of
Valuable info abt arterial health, cardiac function, and cardiovascular risk
What affects blood flow
Resistance in the vessels
Pressure in the vessels
Cardiac output
What affects resistance in the vessels
Length and diameter of vessel
Compliance of the vessel
Blood viscosity
