Histology Lecture 2 -- Blood Vessels Flashcards
What are the efferent vessels?
Arteries
Artery function
Conduct oxygen and nutrients to the tissues which diffuse out through a capillary network
What are the afferent vessels?
Veins
Vein function
Convey the product of metabolism of tissues such as waste products and CO2 to the heart
3 distinct layers of the walls of arteries and arterioles
Intima
Media
Adventitia
What does the adventitia often merge with?
Dense or loose connective tissue surrounding the vessels
Describe the walls of veins or venules
Equivalent layers to arteries and arterioles are generally difficult to identify, or boundaries are poorly defined
Location of capillaries
Between metarterioles and postcapillary veins
Dimensions of capillaries
1 mm in length
8 - 10 micrometers in diameter
Approximate number of capillaries in myocardium
2000 per cubic mm
Histology of capillaries
Simply squamous endothelium with tight junctions sitting on a basement membrane and surrounded by reticular fibers
What support do capillaries have structure-wise?
Intermediate vimentin filaments within endothelial cells
Describe the adventitia of capillaries
Absent or minor
What is the relative area of the capillary network?
800 times larger than the area of the aorta
Blood flow in the capillary network
0.3 mm/s
Blood flow in the aorta
320 mm/s
What substances increase the permeability of capillaries
histamine
bradykinin
4 roles of capillaries
Gas exchange
Thermoregulation
Regulation of blood pressure
Inflammation
3 classifications of capillaries plus 2 subclassifications
Impermeable
Continuous
Permeable (fenestrated, sinusoid)
How are arteries and veins classified?
According to their size and histological features
4 types of arteries
Large elastic arteries
Muscular arteries
Arterioles
Metarterioles
4 types of veins
Large veins
Medium and small size veins
Venules
Postcapillary venules
Function of muscular arteries
Distribute blood to organs
Help regulate blood pressure by contracting or relaxing smooth muscle
Location of smooth muscle in arteries
Media
Location of muscular arteries
Branching tree between the large elastic arteries and arterioles
Accompanying veins for muscular arteries
Medium and small size veins
Shape of muscular arteries
Circular/oval profile
Shape of medium and small veins
Irregular profile, often larger collapsed lumen
Muscular arteries: 3 layers of the intima
Endothelium (with gap and tight junctions)
Sub-endothelial layer (thin)
IELM (Internal Elastic Limiting Membrane; or internal elastica)
Muscular arteries: media
4 - 10 layers of smooth muscle cells
Collagen type III