What is the structure of a typical capillary vs. a capillary in the brain or liver? How does this affect how molecules move between plasma and the interstitial fluid?
What will be an ideal response?
Answer: Typical capillaries are a single layer of cells (endothelium) surrounded by occasional smooth muscles. These cells are loosely attached to each other, so small molecules such as glucose can easily penetrate between cells, moving by diffusion from the blood plasma to the interstitial fluid. In the brain, the capillaries are surrounded by a second layer of cells with tight junctions; these prevent trans-capillary movement of most polar molecules except through specific transporters. In the liver, the endothelium is penetrated by many large channels, including fused-vesicle channels, enabling proteins to move easily across the capillary. This is important because the liver exchanges many proteins with the blood.
You might also like to view...
Muscles of facial expression differ from most skeletal muscles because they usually do NOT insert into a bone.
a. true b. false
All other things being equal, a person who has hypothyroidism will have a higher BMR than a person whose thyroid function is normal.
Answer the following statement true (T) or false (F)
Neurotransmitters that cause skeletal muscle contraction are normally stored in
A) myofibrils. B) motor neuron axon terminals. C) motor units. D) motor end plates. E) actin.
The hearing receptors are most closely associated with the
A) ampulla. B) saccule. C) spiral organ. D) utricle.