Cardiovascular Physiology 27 Flashcards
How many cells thick are cappilaries?
One endothelial cell thick
What are capillaries supported by?
A basement membrane
What does the lack of smooth muscle or elastic tissue in capillaries cause?
The quick exchange of material between blood and interstitial fluid
What is the Interstitial fluid?
The extracellular fluid surrounding tissue and muscle cells
What are the spaces between endothelial cells in capillaries called?
Endothelial clefts
What do intercellular clefts in endothelial cells do?
Act as channels or water filled spaces between endothelial cells through which small, water soluble substances can pass through
What are unable to go through intercellular clefts?
Large lipid insoluble materials like proteins because they are too large
What is the function of cappilaries?
Exchange nutrients
What are the three types of Capillaries?
Continuous, Fenestrated, Sinusoidal
What are continuous capillaries characterized by?
An uninterrupted or complete endothelium and a continuous basement membrane
What is a basement membrane?
A thin, protein carbohydrate layer which surrounds the endothelium and separates it from the adjacent connective tissue
What are the junctions between continuous endothelial cells like?
They have cleft junctions that are usually impermeable and only allow for the passage of ions and water
Which capillaries have the lowest permeability of all capillary types?
Continuous capillaries
What do continuous capillaries all the exchange of?
Water, small molecules, lipid soluble materials
What do Pericytes do in continuous cappilaries?
They have elongated tendrils that wrap around the capillary and contain the same contractile proteins as muscle and it is thought they help to stabilize the walls of blood vessels and help regulate blood flow through capillaries
What are characteristic of Fenestrated capillaries?
The numerous Fenestrae or pores that penetrate the endothelial lining
What does the diaphragm do in fenestrated capillaries?
Connects the different segments of the endothelial cell. Sometimes is not present
What do the pores do in Fenestrated capillaries?
Allow for the rapid exchange of water and solutes, including small peptides
Where are Fenestrated Capillaries found?
Endocrine organs, choroid plexus, GI tract, kidneys
What is the Relative diameter of Sinusoids?
Sinusoids have the largest diameter of all capillaries
What are the shape of Sinusoids?
They are flattened and irregularly shaped
What is the basement membrane like in Sinusoids?
It is very thin or absent
Why does blood move through sinusoids slowly?
In order to maximize the time available for exchange across the sinusoid walls
What do sinusoids allow the exchange of?
They allow the free exchange of water and solutes. Including RBCs, cell debris and plasma proteins
Where are Sinusoids found?
The liver, bone marrow, spleen
