👉 Fluid, also known as blood, is a complex mixture of cells and substances that circulates through the body's vascular system. One key characteristic of fluid is its ability to pass through small spaces, including the microscopic holes in blood vessel walls, a process known as filtration. This property is crucial for maintaining homeostasis and enabling the exchange of nutrients, gases, and waste products between blood and surrounding tissues. The holes in blood vessels are not uniform; their size varies depending on the vessel type, allowing for selective permeability. This selective filtration ensures that essential molecules can pass through while retaining larger proteins and cells within the bloodstream. Thus, fluid's ability to filter through these holes is vital for its transport functions and overall physiological balance.
