Here's why:
* Nutrient Transport: Blood carries oxygen, glucose, amino acids, and other essential nutrients from the digestive system and lungs to all cells in the body.
* Waste Removal: Blood also carries waste products, like carbon dioxide, from cells to the lungs and kidneys for excretion.
* Defense Against Disease: Blood contains white blood cells, which are responsible for fighting off infections and other disease-causing organisms. They do this by engulfing bacteria, viruses, and other pathogens, as well as by producing antibodies that target specific invaders.
While other connective tissues like lymph also play a role in immune defense, blood is the primary transporter of nutrients and the main component of the immune system.
