Intro to CVS and general principles Flashcards
What are the functions of the CVS?
- Transport
- defence
- haemostasis
- thermoregulation
What does the CVS transport?
- O2 and substates to cells
- CO2 and metabolites from cells
- hormones and drugs around the body
How does the CVS function as a defence?
- immune cells and molecules in the blood
How does the CVC function in haemostasis?
- blood clotting mechanism (platelets and blood vessel walls)
Hoe does the CVS function in thermoregulation?
- vasodilation/constriction to dissipate/conserve heat
The CVS is also involved in transmission of pressure - where is an example of this?
- like filtration of substrates in the kidneys
What are the components of the CVS?
- heart (pump)
- blood vessels (transport)
- blood
- spleen
The blood is a central components of the CVS what is it made up of?
- solid (cells) including red and white blood cells (45%)
- fluids (plasma) = 55%
What is the spleen and what does it do within the CVS?
- large flat organ caudal to diaphragm
- stores and filters blood
What can horses and dogs do to their spleens?
- the spleen can contract to shunt blood into CVS if required
There are 4 chambers in the mammal heart what are these chambers?
- 2 atria “primer” pumps
- 2 ventricles “power” pumps
How is contraction controlled?
- controlled by an intrinsic pacemaker, and regulated by the autonomic nervous system
Describe heart rate in larger species and smaller species and how it can be affected?
- lower in larger species
- higher in smaller species
- can be breed specific
- can be health related
Describe arteries and what do they do?
- smooth muscle and elastic walls to prevent inferences with blood flow and are able to stretch
- carry blood away from the heart to the body or lungs
Describe capillaries and what do they do?
- very thin walls (endothelial cells only)
- exchange of gases and substrates with tissues
Describe veins and what do they do?
- less muscular than arteries as they carry blood at a lower pressure
- carry blood back to the heart
- also blood reservoirs (blood rests in veins)
Evolutionary the heart is derived from what?
- a simple pulsating pipe
In adult mammals (+ birds and crocs) the heart has developed what?
- septa to divide it into 4 chambers
- separate systemic and pulmonary circuits so the blood doesn’t mix between the two
What is the fish heart like?
- single atrium and ventricle
What is an amphibian heart like?
- 2 atria , 1 ventricle
What are lizard and chelonians hearts like?
- 2 atria, 1 ventricle with incomplete septa
The mammalian heart is a dual circulatory system - where does blood coming from the body enter?
- cranial vena cava
Where does blood coming from the veins enter?
- the pulmonary veins
Where does blood going towards the lungs exit?
- pulmonary arteries
Where does blood going to the body exit?
- the aorta
Due to the heart having a dual circulatory system - what type of circulation does the left side of the heart have?
- systemic circulation (from the left ventricle)
Describe the left side of the heart:
- blood to and from the body
- high pressure (120/80 systolic/diastolic - in humans)
- oxygenated blood
Describe the right side of the heart:
- Pulmonary circulation (from right ventricle)
- blood to and from lungs
- lower pressure (e.g. 25/8 systolic/diastolic)
- deoxygenated blood
What does systolic mean and what is its effect on blood pressure?
- ventricles contracting so pressure is higher
What does diastolic mean and what is its effect on blood pressure?
- ventricles relaxing so pressure is lower
What does the apex of the heart mark?
- the left ventricle
What externally separates the chambers of the heart?
- fat filled groove (paraconal groove)
What supplies the heart muscle externally?
- coronary arteries
Where are the atria found?
- above the ventricles
What are the atria covered by?
- by atrial appendages = auricles (small sacs, expansions)
Where is the base of the heart found?
- base of the heart is where it is anchored by blood vessels = the top of the heart
Where do the cranial and caudal vena cava enter?
- the right atrium
Where does the pulmonary artery emerge from?
- the right ventricle
Where do the pulmonary veins enter?
- enters the left atrium
Where the the aorta emerge from?
- from the left ventricle
What is the myocardium?
- muscle wall of heart
What is the endocardium?
- Thin layer of cells lining internal surface, continuous with endothelium of blood vessels
What is the sac called around the heart called?
- pericardial sac
What is the function of the pericardial sac?
- functions to aid heart beating in reducing friction
What do the valves in the heart function to do?
- to prevent back flow
What are the atrio-ventricular (inlet valves to ventricles) called?
- mitral value
- tricuspid valve
What are semi-lunar valves (outlet valves from ventricles) called?
- pulmonary
- aortic
What are AV valved anchored by and what does this prevent?
- by chordae tendinae (heart strings) and papillary muscles
- prevents them flapping the wrong way
What valves are located on the left side of the thoracic cavity?
- pulmonary valve
- aortic valve
- mitral
How can location of heart valves help in diagnosis?
- help locate murmurs
What is the cardiac skeleton and what is its function?
- fibrous ridged structure
- Holds cardiac shape and anchors structures
- electrically separate compartments (breaks up muscle continuity between atria and ventricles)
What arteries are the first to branch from the aorta?
- the coronary arteries
How much of the cardiac output is delivered directly to the myocardium?
- 5%
There is extensive what of the myocardium?
- extensive capillarisation
What do elastic vessels (large arteries) do?
- Accommodate stroke volume (high elastance)
- convert intermittent ejection (stop-go -flow) into continuous flow
What do conduit and feed vessels (medium to small arteries) do?
- conduct blood flow to organs
What do resistance vessels (arterioles, terminal arteries) do?
- control arterial blood pressure
- control local blood flow
What do exchange vessels (capillaries) do?
- nutrient delivery to cells
- lymph formation
- removal of metabolic wate
What do capacitance vessels (venules, veins) do?
- control cardiac filling pressure
- reservoir of blood
What are the 3 layers of the blood vessel?
- tunica intima
- tunica media
- tunica adventitia
Describe the tunica intima:
- flattened layer of endothelial cells plus basement membrane
- continuous with endocardium of the heart
Describe the tunic media:
- smooth muscle cells, internal and eternal elastic laminae
Describe the tunica adventitia:
- loose connective tissue, vasa vasorum
What is the difference in the appearance of a artery and vein walls historically?
- arteries have thick walls
- veins have thin walls
What is the difference between the tunica intima in an artery vs a vein?
- artery = rippled, internal elastic membrane present
- vein = smooth looking, internal elastic membrane absent
What are the differences between the tunica medias in arteries vs veins?
- smooth muscle cells in both
- Artery = thick, elastic , external elastic membrane present
- Vein = thin, collagen fibres, external elastic membrane absent
What are the similarities in the tunica adventitia in both veins and arteries?
- collage, elastic fibres, nerve terminals in both
What layer is only present in the capillaries?
- only have tunica intima
What are capillaries?
- endothelium supported by basement membrane
What do some capillary beds contain?
- pericytes
What is the function of a pericyte in a capillary bed?
- supportive
- contractile
There are several types of capillary - what are these?
- continuous (one endothelium sitting on basement membrane)
- fenestrated (Kidney - glomerulus)
- Sinusoidal (spleen)
Why are veins used as reservoirs and how much of blood is at rest?
- large volume of blood can be accommodated in veins so 2/3rds of blood volume is at rest
The amount of blood in reservoir veins can be altered based in physiological need - give an example:
- haemorrhage or exercise > contraction under sympathetic influence
The functions of the cardiovascular system are due to what?
- due to blood flow through body via vessels
Fluid flow (F - volume of fluid transported through a tube per time) is determined by what?
- pressure difference between tube ends ( put triangle here P)
- resistance to flow (R)
What is the equation for volume of fluid transported through a tube per unit of time (F)?
F = triangle P / R
The same pressure does what to the flow?
- the same pressure = same flow
Where does resistance to flow come from?
- Resistance to flow comes from the fluid molecules/particles moving against each other and the fluid moving against the vessel walls
What causes resistance?
- The viscosity (n) of the fluid
- the length (L) of the tube
- the radius (r) of the tube (more important)
What is the equation for resistance (R)?
R = nL/r4
What happens as vessels branch?
- there is an increase in total cross-section
At what vessel can we act to change resistance in blood flow?
- the arterioles
Where does most resistance come from?
- comes from arterioles (many tubes of small radius)
What does the changing of radius of arterioles have a big impact on?
- has a big impact on blood flow to tissues (vasodilation, vasoconstriction)
What vessels is flow slowest in?
- flow slowest in capillaries (site of exchange)
As well as molecules what is also exchanged across capillary walls?
- fluid
Two opposing pressures cause fluid movement across the capillary wall - what are these pressures?
- Hydrostatic pressure exerted by fluid
- oncotic pressure exerted by proteins
The balances of both hydrostatic and oncotic forces determine what?
- determines net fluid movement
What are starling forces?
- they are hydrostatic pressures
In hydrostatic pressures at the input (arterial) end - capillary hydrostatic force is what?
- is high
= net outward hydrostatic force
In hydrostatic pressure at the output (venous) end, capillary hydrostatic pressure is what?
- pressure is lower
= net inward hydrostatic force
What do hydrostatic forces create along the vessel?
- create a gradient along the vessel
In oncotic pressure at the input (arterial) end, capillary oncotic force is what?
- is low
= net outward oncotic force
In oncotic forces at the output end (venous) capillary oncotic pressure is what?
- higher
= net inward oncotic force
What do oncotic pressure create along a vessel?
- create a gradient along the vessel
The balance of forces along a vessel determines what?
- movement
The net effect of the four starling forces results in what fluid movements?
- outward (filtration)
- inwards (reabsorption)
Every tissues has a difference in balance of forces depending on what?
- the anatomy and function of the tissue
What is the general rule for fluid filtering and reabsorption in tissue?
- generally in tissue more fluid is filtered than is reabsorbed
Well-perfused capillaries filter fluid what happens to their filtration rate along the vessel?
- filtration rate decreases along the vessel
The composition of lymph is similar to the composition of what?
- interstitial fluid
Excess lymph drains where?
- into lymphatic vessels
Where do lymphatic vessel carry interstitial fluid?
- back into the bloodstream
Lymph travels through progressively larger lymphatic vessels until they are emptied where?
- back into venous circulation
Lymph may travel through what node?
- lymph nodes
Where does the thoracic duct commonly drain into?
- left branches of vena cava (left jugular, subclavian, brachiocephalic veins)
Some conditions can result in abnormal accumulation of interstitial fluid (oedema) via what?
- increased capillary pressure
- decreased circulating plasma protein (decreases absorption)
- increased capillary permeability (inflammation)
- decreased lymphatic drainage (blockage)
