astrocytes
This is known as an astrocyte
respiratory membrane
Astrocytes are star-shaped neuroglia that form the blood brain barrier between blood vessels and neurons.
blood-brain barrier (!)
Neurons conduct electrical impulses in the brain. Neuroglia are cells that support the neurons. These cells undergo mitosis where neurons do not. Brain tumors are formed from neuroglia cells because they mitosis.
Air sacs; blood vessels that surround the air sacs
The capillaries are in between the red and blue veins :)
capillaries between the cells in the lungs or the capillaries between the cells in the body
Lymphatic capillaries are dead-end vessels interspersed between the vascular capillaries. They lack tight junctions between endothelial cells and therefore are more permeable to proteins than are vascular capillaries.
It technically can be a barrier; a barrier between the water in the bucket and the ground.
Here the capillaries have no gap in between them. Second and outer layer comes from the connective tissue of brain. They also have no gap between them. This effective mechanism makes, infection of brain, very less likely.
Capillaries