Flashcards in Week 6 CVM Deck (31):
What are the three major types of blood vessels?
Arteries, veins and capillaries
Name the three layers/tunics of a blood vessel from outermost to innermost
1. Tunica externa/adventitia
2. Tunica media
3. Tunica interna
Which blood vessel type is involved with exchange with tissues?
Which blood vessel type carries blood away from the heart?
Arteries and arterioles
Which blood vessel type carries blood to the heart?
Veins and venules
Which sized veins have valves in them?
Medium and small veins
What is the significance is valves in veins?
Prevent backflow of venous blood that can occur due to gravity. Valves are found mostly in the limbs for this reason
What is the name of the tiny blood vessel networks that service the layers of the larger vessels themselves?
Describe the histological make up of the tunica externa
Connective tissue with loose weave of collagen and elastic fibres. Contains nerves and lymphatic vessels
Describe the histological make up of the tunica media
Smooth muscle( innervated by sns) and lose connective tissue.
Describe the histological make up of the tunica interna
Simple squamous endothelium, connective tissue with elastin. In contact with blood
List the two types of arteries
Elastic and muscular arteries
List the 4 major controllers of flow?
4 . Endothelial
Describe the flow of blood through the body winning and ending with the right atrium ?
• Blood 'begins' in right atrium
• Pumped into pulmonary artery
• Into lung, O2 exchange occurs
• Returns to left atrium
• Pumped into aorta via left ventricle
• Blood to the periphery from through arteries
• Arterioles -> capillary beds
• Fluid forced out of capillaries to interstitium
• Fluid returns to capillary beds at venous end
• Capillaries drain into venules
• Venules drain into the veins
• Veins empty in the venae cavae
• Blood travels back to the right atrium
Describe some characteristics of elastic arteries
Largest arteries with diameter of 1-2.5cm
Closest to the heart
Conduct blood from heart to medium sized arteries
Thick walls but wide lumen (important for laminar blood flow )
Lots of elastin to withstand pressure of ejection from the ventricle and to dampen pressure oscillation contain the most elastin than any other vessel type
Smooth muscle opposes stretch rather than actively constricting vessel diameter.
Elastic arteries expand and recoil as heart ejects blood consequently blood flows continuously rather than starting and stopping with pulsating rhythm of heart beat
Describe some characteristics of muscular arteries
Do the major redistribution of blood flow to the organs
Distal to elastic arteries , distributing blood among the organ systems
Diameter of 0.3-1cm
Thickest tunica media of all arteries contains more smooth muscle than the elastic arteries (less elastin)
Vasoactive (capable of vasodilation and constriction to modulate blood pressure and flow)
Account for the majority of arteries in the body
They are more active in vasoconstriction but less distensible than elastic (not capable of stretching)
Distal to both types of arteries (muscular and elastic)
Smallest of the arteries with diameters of 10 micrometers to 0.3 mm
The smallest arteriole (terminal or resistance arterioles have no tunica adventitia and may be 1 layer of smooth muscle surrounding one layer of endothelial cells
Vasoactive with strong influence on blood pressure and flow (protective mechanism)
Basically arterioles are smooth muscle machines packed full of smooth muscle and sometimes a few scattered elastic fibers
The make local decisions of where blood is going to flow and can shut down flow to a particular capillary bed
Constriction of arterioles causes the tissues served to be largely bypassd
Which blood vessel type do rbcs travel in single file?
List the 3 types of capillaries and how they differ
1. Continuous capillaries:
Endothelium is uninterrupted tight junctions
These junctions are usually incomplete and leave intercellular clefts which are large enough to allow limited passage of fluids and small solutes
Service all tissues except epithelia and cartilage
The can also be completely impermeable(Blood brain barrier) or be able to pass water, small solutes and lipid soluble materials
Common in the skin and muscles
2. Fenestrated Capillaries:
Endothelium has numerous pores/fenestrations between cells to allow for easier fluid movement and movement of small proteins allows easy uptake or filtration
Found wherever active filtration and absorption occurs eg. Intestines , kidneys
3. Sinusoidal Capillaries:
Very leaky capillaries which are usually fenestrated
Allow larger molecules to pass than the fenestrated capillaries allow
Found only in liver, bone marrow , spleen (lymphoid tissues) and some endocrine organs (adrenal medulla)
They have less tight junctions and larger intercellular clefts
May have large and irregular lumens
What is micro circulation
Blood flow from arteriole through capillaries to the Venule
What is the metarteriole
Vessel that links arterioles and true capillaries
What is a thoroughfare channel
Vessel that links venules and true capillaries
In terms of the capillary bed, what is the vascular shunt?
metarteriole & thoroughfare channel connect directly and drain the capillaries but also may allow blood to bypass the capillaries (due to changing need) and connect the arteriole and venule directly
What are precapillary sphincters??
Blood flow from metarteriole to capillary is controlled by precapillary sphincters which are cuffs of smooth muscle which surround the roots of each capillary at the metarteriole. It acts as a valve to regulate blood flow into the capillary.
When the sphincters are relaxed, blood flows through the true capillaries and takes part in exchanges with tissue cells
When the sphincters are contracted, blood flows through the shunts and bypasses the tissue cells
List the four assist devices for venous flow of blood
Muscle pump,mrwspiratory pump, cardiac suction and venoconstriction
What is an anastomoses
where two blood vessels merge/join together
a connection between two peripheral vessels without an intervening capillary bed
arteries supplying the same capillary bed often join to create arterial anastomoses (collaterals)
metarteriole thoroughfare passages link arterioles and venules
veins form many anastomoses
What are the four starlings forces?
1. Capillary Hydrostatic Pressure
Pressure of fluid within the capillary forces water and dissolved substances out of capillary
~30mmHg at arteriole end and 10mmHg at venous end
2. Plasma Colloid Osmotic (aka Oncotic) Pressure
Osmotic pressure caused by blood proteins draws fluid in
3. Interstitial Fluid Pressure
Hydrostatic pressure in tissues may draw or oppose flow from capillary
Varies with capillary bed; positive in glomerulus, negative in loose tissues, like the skin (set average as 0 mmHg)
4. Interstitial Fluid Colloid Osmotic (aka Oncotic) Pressure
Proteins in tissues causes osmosis out of capillary
How many litres of fluid from plasma is lost per day?
~3L but Lymphatics return it!
Describe true aneurysms
•all 3 layers/tunics are affected in the blood vessel
•Defined as a 50% increase in the normal diameter of the vessel.
•The artery wall can balloon out symmetrically to form a 'fusiform' aneurysm or there can be a local 'blow-out' to form a 'saccular' aneurysm.
Describe dissecting aneurysms
• A split or dissection within the tunica media
• Allows blood to collect and compress the lumen