Lecture 1 - Introduction to and Histology of the CVS Flashcards
what affects diffusion?
area - determined by capillary density
diffusion resistance - determined by nature of the barrier and molecules diffusing
concentration gradient - depends a lot on blood flow through capillary
what is the blood flow to the brain?
min - 0.75 l/minmax - 0.75 l/min
what is the blood flow to the heart?
min - 0.3 l/minmax - 1.2 l/min
what is the blood flow to the kidneys?
min - 1.2 l/minmax - 1.2 l/min
what is the blood flow to the gut?
min - 1.4 l/minmax - 2.4 l/min
what is the blood flow to muscle?
min - 1 l/minmax - 16 l/min
what is the blood flow to the skin?
min - 0.2 l/minmax - 2.5 l/min
what is the total blood flow in the body?
min - 5 l/minmax - 24.5 l/min
how is blood flow controlled?
resistance vessels - arterioles and pre capillary sphincters
what is capacitance?
ability to cope with changes in cardiac output - store of blood in veins
what are the two typed of artery?
elastic
muscular
what is the role of elastic arteries?
expand slightly with each heartbeat
what is the role of muscular arteries?
branch into arterioles to regulate amount of blood reaching an area
diameter controlled by ans
what are the two types of capillary wall?
continuous
fenestrated
what is a sinusoid?
type of capillary with a wider diameter
special lining cells
incomplete basal lamina
how does the structure of a vein differ to an artery?
wall is thinner
lumen is wider and irregular
valves in large veins
what are the three layers of vein and artery walls?
in to out
tunica intima
tunica media
tunica adventitia
describe the intima layer of elastic arteries
endothelial cells with long axis parallel to long axis of artery; narrow subendothelium of connective tissue
describe the media layer of elastic arteries
40-70 fenestrated elastic membranes with smooth muscle cells and collagen between the lamellae
describe the adventitia layer of elastic arteries
layer of fibroelastic connective tissue containing vasa vasorum, lymphatic vessels and nerve fibres
describe the intima layer of muscular arteries
endothelium, sunendothelial layer, thick internal elastic lamina
describe the media layer of muscular arteries
40 layers of smooth muscle cells, prominent external elastic lamina
describe the adventitia layer of muscular arteries
thin layer of fibroelastic connective tissue containing some vasa vasorum, lymphatic vessels and nerve fibres
what is the role of sympathetic nerve endings in the tunica adventitia?
vasoconstriction
where is the thin internal elastic lamina present?
larger arterioles
what is the difference between metarterioles and arterioles?
smooth muscle layer is not continuous
what is the role of a precapillary sphincter?
allows arterioles and metarterioles to serve as flow regulators
what is the difference between continuous and fenestrated capillaries?
continuous - pericytes form a branching network on the outer surface of the endothelium
fenestrated - pericytes are present but there are pores in the endothelium
What is the role of the cardiovascular system?
To supply cells of the body with their metabolic needs
Where does exchange with tissues occur?
Capillaries
How is the area available for exchange determined?
Capillary density
How is diffusion resistance determined?
The nature of the barrier
The molecules that are diffusing
What is the most important variable in concentration gradient?
Flow of blood through the capillary
What is the distribution of blood volume (5l)?
11% in arteries and arterioles
5% in capillaries
17% in heart and lungs
67% in veins
What happens if blood pressure is not maintained?
Veins collapse
Which 3 places do blood vessels not reach?
Cartilage
Epithelia
Cornea
