Cardiovascular Histology - Heart and Blood Vessels Flashcards
What is the outermost layer of a blood vessel?
What is it made of?
What does it do?
Tunica adventitia
Collagenous connective tissue
Anchorage, support, elasticity, carries nerve and blood supply to vessel
What is the middle layer of a blood vessel?
What is it made of?
What does it do?
Tunica media
SM
Support, elasticity, contractility(tone), regulation and smoothing of blood flow
What is the innermost layer of a blood vessel?
What is it made of?
What does it do?
Tunica intima
Endothelium over a little dense connective tissue
Selectively permeable barrier to blood, regulated adhesion to platelets and leukocytes, makes mediators controlling vessel tone and inflammation.
What is the largest type of artery?
What are its special features?
Elastic - pulmonary and aorta and their largest branches
They have a very thick T. media with many elastic sheets that absorb systolic flow by stretching and continue blood flow in diastole by elastic recoil.
What is the alternate name for distributing arteries?
What do they do?
What special features do they have?
Muscular arteries
They are contractile - regulate blood flow and blood pressure
Visible by eye, structure is same as arterioles, have single internal elastic lamina between I and M, have an external elastic lamina - several laminae in A near M.
What is the name of the smallest type of artery?
How big are they?
What do they do?
What special features do they have?
Arterioles
<0.3mm wide
Regulate BP and flow
M is predominant for contractility against high BP, SM runs circularly and is in 1-2 layers
What are pericytes?
Pericytes are contractile stem cells that wrap around the endothelial cells that line the capillaries for contraction and repair.
Which type of capillary has no holes in its walls?
Continuous.
What are the special features of fenestrated capillaries?
They have many tiny pores in the wall all the way through the cytoplasm which makes it more permeable.
What differentiates sinusoid capillaries from fenestrated capillaries?
They are wider - 20 to 40um - allowing slow blood flow and thus have the highest rates of exchange.
What are the main functions of veins and venules?
Control blood flow and BP.
What is unique about the smallest venules?
They don’t have a Tunica Media.
What are special feature of veins?
They have valves with skeletal muscle that assist the flow of blood.
Some major veins in limbs have longitudinal SM in their wall to assist flow of blood against gravity.
How does a venule differ to an arteriole?
It has a larger diameter, thinner wall, less SM muscle, less rounded.
How does over-filling of the atria affect urine secretion?
Over-filling causes stretching and causes ANP release which increases secretion of water and Na+ into urine.
