CVS Session 1 Flashcards
How do hydrophobic and hydrophilic molecules move into capillaries?
Hydrophobic - direct diffusion through lipid bilayer
Hydrophilic - diffuse through small aqueous pores b/w cells
Why do we need a CVS?
Diffusion time is proportional to distance squared
Most cells far away from O2 and nutrient supply
What factors affect the rate of diffusion?
Area
Diffusion resistance
Concentration gradient
What is the total blood flow at rest?
~5 litres per min
Why is a resistance system needed in the CVS?
To reduce ease of perfusion to some areas so harder to perfuse areas receive adequate blood flow
Which BV give variable resistance?
Arterioles and pre-capillary sphincters
What provides capacitance for flexible blood flow?
Easy distension/collapse of vein walls
5 components of CVS and their functions?
Heart = pump Vessels and blood = distribution Capillaries = exchange system Arterioles and pre-capillary sphincters = flow control Veins = capacitance
Path of outflow blood
Large arteries > medium arteries > arterioles > metarterioles > capillaries > post capillary venules > venules > medium veins > large veins
Where is the velocity of blood lowest?
Capillaries bed
Describe the course of the pulmonary trunk.
Major artery from R. ventricle
Bifurcates into R+L pulmonary arteries
Describe the course of the aorta.
Major artery from L. ventricle
Posteriorly oblique arch to descend into thoracic cavity
Branches into brachiocephalic, common carotid and subclavian
Terminates by bifurcating into R+L common iliac arteries
What is the blood pressure in the aorta during systole?
~120 mmHg
What is the aortic pressure during diastole?
70-80 mmHg
Describe the function of elastic arteries in systole and diastole.
Pressure reservoirs:
Store elastic energy in systole
Act as auxiliary pumps in diastole
What are the layers of an artery (lumen outwards)?
Tunica intima
Tunica media
Tunica adventitia
What are the 5 types of artery?
Elastic conducting
Muscular distributing
Arterioles
End
Describe the layers of an elastic conducting artery.
TI: Fenestrated internal elastic lamina and endothelial cells w/long axis parallel to long axis of artery
TM: 40-70 fenestrated elastic membranes w/smooth muscle+collagen
TA: thin fibroelastic layer w/vasa vasorum, lymph vessels and nerves
What produces the elastin, collagen and matrix in elastic conducting arteries?
Smooth muscle cells
What is dissecting aorta?
When blood pushes b/w lamellae in TM
Describe the layers of a muscular distributing artery.
TI: endothelium, subendothelial layer, thick internal elastic lamina
TM: 40 layers of smooth muscle cells connected by gap junctions and prominent external elastic lamina
TA: thin fibroelastic layer w/vasa vasorum, lymph vessels and nerves
Describe propagation in a muscular distributing artery.
NA released at nerve endings –> fenestrations in TM depolarise some smooth muscle cells –> propagated by gap junctions
Describe the layers of an arteriole.
TI: endothelial cells
TM: 1-3 layers of smooth muscle (thin internal elastic lamina in larger ones only)
TA: scant
Describe the structure of a small arteriole.
1 muscle cell completely encircles the endothelial cells
What is not present in an arteriole?
External elastic lamina
Describe the structure of a metarteriole.
Smooth muscle cells spaced apart each encircling the endothelium of a capillary arising from an arteriole
What is the function of a metarteriole?
Feed many capillaries, controlling blood flow into the capillary bed
What are end arterioles?
Terminal artery supplying most or all of the blood to an area w/out significant collateral circulation
Give examples of end arteries.
Coronary
Splenic
Renal
What is bridging?
Compression of a segment of coronary artery during systole
What is the function of a lymphatic capillary?
Drain and return excess ECF to blood and the internal jugular and subclavian vein junctions
What is the function of a precapillary sphincter?
Allow arterioles and metarterioles to serve as flow regulators for the capillary beds.
Open: allows plentiful blood flow
Closed: blood flow greatly reduced
What is a central channel?
Metarteriole + thoroughfare channel = bypass capillary bed
Describe the properties of a capillary.
7-10 micrometer diameter
<1mm long
Single layer of endothelium and BM
Allow passage of one cell at once
What is the maximum distance of a tissue from a capillary?
30 micrometers
What are the three types of capillary?
Continuous
Fenestrated
Sinusoidal
Describe a continuous capillary.
Most common type
Cells joined by tight/occludin junctions
Pericytes form branching network around endothelium
Pericytes can into muscle cells/fibroblasts in angiogenesis, tumour growth and wound healing
Describe a fenestrated capillary
4 routes of transport available
Interruptions bridged by a thin diaphragm
Found in gut, endocrine glands, renal glomerulus
What are the four routes of transport through a fenestrated capillary?
Direct diffusion
Diffusion through intercellular cleft
Diffusion through fenestration
Pinocytosis
Describe a sinusoidal capillary.
Largest diameter therefore lowest blood flow
Gals in walls for whole cells to move b/w blood and tissue
Found in liver, spleen and bone marrow
Describe a post capillary venule.
Endothelial lining w/associated pericytes
10-30 micrometer diameter
Even more permeable than capillaries
When is the pressure in a post capillary vein not lower than the pressure in the surrounding tissue fluid?
Inflammatory response when fluid and leukocytes emigrate
Where is the preferred location of emigration of leukocytes from the blood?
Post capillary venule
At what diameter do merging venules begin to develop a tunica media?
50 micrometers
How is a tunica media formed?
Smooth muscle fibres become associated with the endothelium
What do valves in venules consist of?
Thin intimal extensions
In which direction is the longitudinal axis of the endothelial cells?
Parallel to the direction of blood flow
How do you differentiate b/w veins and arteries?
Veins have: Larger diameter Thinner wall More CT in wall Fewer elastic and muscle fibres in wall
Describe the structure of small and medium veins.
TI: thin
TM: 2-3 layers of smooth muscle
TA: well developed
Describe the structure of large veins.
Diameter >10mm
TI: thick
TM: not prominent
TA: well developed
Why do superficial veins of the legs have a well-defined muscular wall?
Resist distension caused by gravity (proposed)
What is present in large vein Ta and TM not seen in smaller veins?
TA: well developed, longitudinally oriented smooth muscle
TM: circularly oriented smooth muscle and vasa vasorum
What is a venae comitantes?
A structure enclosed by a sheath consisting of a pair of veins flanking an artery
What is the function of a venae comitantes?
Promote venous return in the involved veins
How does a venae comitantes function?
The pulsing of the artery promotes venous return w/in the adjacent artery
Give three examples of venae comitantes.
Brachial
Ulnar
Tibial
Where do the left and right coronary arteries arise from?
Left and right aortic sinuses within the aorta
Where are the aortic sinuses found?
Within the aorta behind the left and right flaps of the aortic valve
How does blood enter the coronary arteries?
When the heart is relaxed backflow of blood fills the aortic sinuses allowing entry into the coronary arteries
What is the initial branch of the left coronary artery?
Left anterior descending artery (LAD)
What is another name for the LAD?
Anterior interventricular artery
What does the LCA progress to become after it has branched to form the LAD?
Left marginal and circumflex arteries
What does the right coronary artery branch to form anteriorly?
Right marginal artery
What does the right marginal artery branch to form posteriorly?
Posterior interventricular artery
Where do the cardiac veins drain?
Coronary sinus
Where is the coronary sinus located?
Posterior surface in the coronary sulcus
Where does the coronary sinus drain?
Into the right atrium
Where is the coronary sinus opening located in the right atrium?
B/w the right atrioventricular orifice and the inferior vena cava orifice
How many tributaries drain into the coronary sinus?
Five
Which is the main tributary of the coronary sinus?
The great cardiac vein
Describe the path of the great cardiac vein.
Originates at apex
Follows anterior interventricular groove into sulcus and around left side to join the coronary sinus
Describe the path of the small cardiac vein.
Anterior side of heart
Passes around right side of heart to join the coronary sinus
Where does the middle cardiac vein drain?
The right side of the heart
Where is the middle cardiac vein located?
Posterior surface of the heart
Where is the left marginal vein located?
Left posterior side
Describe the path of the left posterior ventricular vein.
Located in the centre on the posterior surface
Runs along posterior interventricular sulcus to join the coronary sinus
What regions are supplied by the right coronary artery?
Right atrium
SAN
AVN
Posterior part of interventricular septum
What are the vein draining regions of the right coronary artery?
Small cardiac vein
Middle cardiac vein
Which regions are supplied by the right marginal artery?
Right ventricle
Apex
Which are the vein draining regions for the right marginal artery?
Small cardiac vein
Middle cardiac vein
Which regions are supplied by the posterior interventricular artery?
Right ventricle
Left ventricle
Posterior third of interventricular septum
What is the draining region of the posterior interventricular artery?
Left posterior ventricular vein
Which regions does the left coronary artery supply?
Left atrium
Left ventricle
Interventricular septum
AV bundles
What drains the left coronary artery?
Great cardiac vein
What regions does the LAD supply?
Right ventricle
Left ventricle
Anterior 2/3 of in interventricular septum
What drains the LAD?
Great cardiac vein
What region does the left marginal artery supply?
Left ventricle
What drains the left marginal artery?
Left marginal vein
Great cardiac vein
Which regions are supplied by the circumflex artery?
Left atrium
Left ventricle
What drains the circumflex artery?
Great cardiac vein
Describe the path of the right coronary artery.
Right of pulmonary trunk –> coronary sulcus –> branches –> continues to posterior surface in coronary sulcus –> branches again
What are the two branches of the right coronary artery?
Right marginal artery
Posterior interventricular artery
Describe the path of the left coronary artery.
B/w left side of pulmonary trunk and left auricle –> divides into LAD and circumflex branch
Describe the path of the LAD.
Follows the anterior interventricular groove towards the apex where it continues on the posterior surface to anastamose with the posterior interventricular branch
Describe the path of the circumflex branch.
Follows coronary sulcus to the left border and onto posterior surface giving rise to left marginal artery
Describe the path of the left marginal branch.
Follows left border of the heart
