1) Filter the blood: The capillaries are lined with tiny pores that allow water, nutrients, and oxygen to pass through, while preventing larger molecules such as proteins from escaping. This process is known as filtration.
2) Reabsorb water: The capillaries also reabsorb water from the tissues back into the blood. This process is driven by the osmotic pressure of the blood, which is higher than that of the tissues.
3) Exchange gases: The capillaries are where oxygen is exchanged for carbon dioxide. Oxygen diffuses from the blood into the tissues, while carbon dioxide diffuses from the tissues into the blood.
4) Deliver nutrients: The capillaries deliver nutrients from the blood to the tissues. Nutrients diffuse from the blood into the tissues, where they are used for energy production and other metabolic processes.
5) Remove waste products: The capillaries remove waste products from the tissues and transport them to the kidneys, where they are excreted. Waste products diffuse from the tissues into the blood, where they are transported to the kidneys for elimination.
The work done in the capillaries is essential for maintaining homeostasis in the body. By filtering the blood, reabsorbing water, exchanging gases, delivering nutrients, and removing waste products, the capillaries ensure that the tissues have the resources they need to function properly.