Intro to CVS & general principles Flashcards
What is the primary function of the cardiovascular system (CVS)?
Transport, Defence, Haemostasis, Thermoregulation
What substances does the CVS transport to cells?
O2 and substrates
What does the CVS remove from cells?
CO2 and metabolites
What role does the CVS play in defence?
Immune cells and molecules in blood
What is the function of haemostasis in the CVS?
Blood clotting mechanism
What mechanisms are involved in thermoregulation by the CVS?
Vasodilation and vasoconstriction
What are the main components of the CVS?
Heart, Blood vessels, Blood, Spleen
What is the primary role of the heart in the CVS?
Pump
What is the approximate composition of blood?
- Solid (cells) ~45%
- Fluids (plasma) ~55%
What is the function of the spleen in the CVS?
Large flat organ caudal to the diaphragm
How many chambers does the heart have in mammals?
4
What are the two types of pumps in the heart?
- 2 atria ‘primer’ pumps
- 2 ventricles ‘power’ pumps
What controls the contraction of the heart?
An intrinsic pacemaker and regulated by the autonomic nervous system
What marks the left ventricle of the heart?
Apex
The apex is the pointed end of the heart that indicates the position of the left ventricle.
What separates the heart chambers externally?
Fat-filled grooves
These grooves are important for the physical structure and organization of the heart.
What supplies the heart muscles externally?
Coronary arteries
Coronary arteries branch off from the aorta and provide blood to the heart muscle.
Where are the atria located in relation to the ventricles?
Above the ventricles
The atria are positioned superiorly to the ventricles in the heart structure.
What are the small sacs or expansions covering the atria called?
Atrial appendages or auricles
These structures help to increase the volume of the atria.
Where is the base of the heart located?
Near the atria (top)
The base of the heart is oriented towards the top of the heart structure.
Which veins enter the right atrium?
Cranial and caudal vena cava
These veins bring deoxygenated blood from the body to the heart.
From which ventricle does the pulmonary artery emerge?
Right ventricle
The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.
Which veins enter the left atrium?
Pulmonary veins
These veins carry oxygenated blood from the lungs to the heart.
From which ventricle does the aorta emerge?
Left ventricle
The aorta is the main artery that carries oxygenated blood from the heart to the body.
What is the myocardium?
Muscle wall of the heart
The myocardium is responsible for the contraction of the heart.
What is the endocardium?
Thin layer of cells lining internal surface
The endocardium is continuous with the endothelium of blood vessels.
What is the function of the heart valves?
Prevent backflow
Valves ensure unidirectional blood flow through the heart.
What are the two sets of heart valves?
Atrioventricular and Semi-lunar valves
Atrioventricular valves include mitral and tricuspid; semi-lunar valves include pulmonary and aortic.
What are the inlet valves to the ventricles called?
Atrioventricular valves (Mitral/Bicuspid & Tricuspid)
These valves are crucial for regulating blood flow from the atria to the ventricles.
What are the outlet valves from the ventricles called?
Semi-lunar valves (Pulmonary or Aortic)
These valves control blood flow from the ventricles to the arteries.
What anchors the atrioventricular valves?
Chordae tendinae (heart strings)
These structures prevent the valves from inverting during heart contractions.
What is the cardiac ‘skeleton’?
Rigid, fibrous structure that holds cardiac shape and anchors structures
It electrically separates compartments, breaking muscle continuity between atria and ventricles.
What are coronary arteries?
The first arteries to branch from the aorta
They deliver approximately 5% of the cardiac output directly to the myocardium.
What percentage of cardiac output is delivered to the myocardium?
~5%
This indicates the importance of coronary circulation in supplying the heart muscle.
How many functional types do blood vessels fall into?
5
Each type serves a specific role in the circulatory system.
What are the three layers of blood vessels?
- Tunica intima
- Tunica media
- Tunica adventitia
Each layer has distinct structures and functions.
What characterizes the Tunica intima?
Flattened layer of endothelial cells plus basement membrane
This layer is crucial for reducing friction as blood flows through the vessel.
What is found in the Tunica media?
Smooth muscle cells, internal and external laminae
This layer is responsible for the contraction and dilation of blood vessels.
What does the Tunica adventitia consist of?
Loose connective tissue and vasa vasorum
The vasa vasorum supplies blood to the outer layers of large vessels.
How do arteries and veins differ in appearance?
Arteries have round and thick walls, while veins have flattened thin walls
This structural difference is related to their functions in the circulatory system.
What distinguishes the Tunica intima of arteries from that of veins?
Arteries have a rippled appearance with an internal elastic membrane present, while veins have a smooth appearance and lack this membrane
This affects the elasticity and functionality of the vessels.
What is found in the Tunica media of arteries compared to veins?
Arteries have more smooth muscle cells and elastic fibers; veins have fewer smooth muscle cells and more collagen fibers
This difference allows arteries to handle higher pressure from blood flow.
What does the Tunica adventitia contain in both arteries and veins?
Collagen, elastic fibers, and nerve terminals
Vasa vasorum may also be present in larger arteries.
What supports the endothelium in capillaries?
Basement membrane
The basement membrane provides structural support to the endothelium of capillaries.
What are pericytes and where are they found?
Supportive, contractile cells found in some capillary beds
Pericytes help in the regulation of blood flow and maintenance of capillary structure.
What type of capillaries are most common in tissue beds?
Continuous capillaries
Continuous capillaries have uninterrupted endothelial linings and are characteristic of most tissues.
Which specialised capillaries are found in the kidney?
Fenestrated capillaries
Fenestrated capillaries have pores that facilitate filtration, especially in the glomerulus of the kidney.
What type of capillaries are found in the spleen?
Sinusoidal capillaries
Sinusoidal capillaries are wider and more irregularly shaped, allowing for the exchange of larger molecules.
What proportion of blood volume can be accommodated in veins at rest?
2/3 rds of blood volume
Veins serve as a blood reservoir, capable of holding a significant amount of blood.
What structures do veins have that arteries do not?
Valves
Valves in veins prevent backflow and ensure unidirectional blood flow towards the heart.
What determines fluid flow (F) in the cardiovascular system?
Pressure difference (ΔP) and resistance (R)
Fluid flow is affected by the driving pressure and the resistance encountered in the vessels.
What is the formula for fluid flow?
F = ΔP/R
This formula indicates that fluid flow is directly proportional to pressure difference and inversely proportional to resistance.
What factors determine resistance to fluid flow?
Viscosity (ƞ), length (L), and radius (r) of the tube
These factors influence how easily fluid can move through a vessel.
What vessels are considered resistant vessels in the circulatory system?
Arterioles
Arterioles have a small radius and contribute significantly to the overall resistance in the circulatory system.
What happens to total cross-section as vessels branch?
It increases
The branching of vessels increases the total cross-sectional area, affecting blood flow dynamics.
Where is blood flow slowest and why?
In capillaries, due to exchange processes
Slow flow in capillaries allows for the exchange of nutrients and waste products.
What are the two opposing pressures that determine fluid movement across capillary walls?
- Hydrostatic pressure
- Oncotic pressure
Hydrostatic pressure is exerted by the fluid, while oncotic pressure is exerted by proteins in the blood.
Fill in the blank: The balance of hydrostatic and oncotic pressures determines _______.
net fluid movement
The interaction of these pressures controls how fluids move in and out of capillaries.
What are Starling forces?
Starling forces = hydrostatic pressures
Starling forces describe the pressures that influence fluid movement across capillary walls.
Describe the hydrostatic force at the input (arterial) end of a capillary.
High capillary hydrostatic force
This results in a net outward hydrostatic force.
Describe the hydrostatic force at the output (venous) end of a capillary.
Lower capillary hydrostatic pressure
This results in a net inward hydrostatic force.
Fill in the blank: At the input (arterial) end, the capillary oncotic force is _______.
Low
This results in a net outward oncotic force.
Fill in the blank: At the output (venous) end, the capillary oncotic pressure is _______.
Higher
This results in a net inward oncotic force.
What is the net effect of the four Starling forces?
Fluid movement
The movement can be outward (filtration) or inward (resorption).
What generally happens in tissues regarding fluid movement?
More fluid is filtered than is reabsorbed
This is influenced by the specific anatomy and function of the tissue.
What is the composition of lymph?
Same as interstitial fluid
Lymph is derived from interstitial fluid.
What happens to excess interstitial fluid?
Drains into lymphatic vessels
The lymphatic system returns this fluid to the bloodstream.
How does lymph travel back into the bloodstream?
Through progressively larger lymphatic vessels until emptied into venous circulation
This process ensures the return of interstitial fluid to the blood.
List the conditions that can lead to abnormal accumulation of interstitial fluid (edema).
- Increased capillary pressure
- Decreased circulating plasma protein
- Increased capillary permeability (e.g., inflammation)
- Decreased lymphatic drainage
These factors disrupt normal fluid balance.
