👉 Fluids, including blood, are essential for transporting nutrients, oxygen, and waste products throughout the body. However, their movement is often hindered by various barriers. Vascular smooth muscle cells can constrict blood vessels, limiting fluid flow, while endothelial cells lining blood vessels may release substances that restrict fluid passage. Additionally, the presence of proteins and other large molecules can impede fluid movement through capillaries. In some cases, physical barriers such as tight junctions between cells in tissues like the brain's blood-brain barrier prevent fluid from passing. These barriers are crucial for maintaining homeostasis but can also contribute to conditions like edema or impaired organ function if they become overly restrictive.
