Which of the following is NOT a function of blood?
The option that is NOT a function of blood is the one describing hormone production or generating nerve impulses. Blood transports substances, regulates temperature and pH, and protects against infection and blood loss, but it does not manufacture hormones or conduct nerve signals.
The answer
On this question, the correct choice, the one that is NOT a function of blood, is typically "production of hormones" (or, in some versions, "generating nerve impulses"). Blood carries hormones from endocrine glands to their targets, but it does not make them, and it plays no role in conducting nerve impulses (that is the job of neurons). The genuine functions of blood fall into three categories: transportation, regulation, and protection.
The three real functions of blood
1. Transportation. Blood moves substances throughout the body: oxygen from the lungs to tissues and carbon dioxide back to the lungs; nutrients absorbed from the digestive tract; metabolic wastes to the kidneys for removal; and hormones from endocrine glands to their target organs. Note the distinction: transporting hormones is a blood function, but producing them is not.
2. Regulation. Blood helps maintain homeostasis. It regulates body temperature by absorbing heat and redistributing it (dilating skin vessels to release heat or constricting them to conserve it). It regulates pH through buffers like bicarbonate that keep blood in its narrow healthy range (about 7.35 to 7.45). It also helps regulate fluid balance and blood volume in tissues.
3. Protection. Blood defends the body. White blood cells and antibodies fight infection and foreign invaders, and platelets and clotting factors stop bleeding through clot formation (hemostasis), preventing blood loss after injury.
Why the distractor is wrong
Students get tripped up because blood is closely involved with hormones and nerves, but only indirectly:
- "Production of hormones" — hormones are produced by endocrine glands (thyroid, adrenal, pancreas, pituitary, etc.), not by blood. Blood is merely the delivery highway.
- "Generating nerve impulses" — nerve impulses are generated and conducted by neurons in the nervous system. Blood supplies neurons with oxygen and glucose but does not create the impulses.
- "Producing digestive enzymes" — another common wrong-function distractor; enzymes come from the pancreas and other digestive organs.
By contrast, every true option (carries oxygen, defends against disease, regulates temperature, clots to prevent blood loss, maintains pH) fits neatly into transport, regulation, or protection. Whichever listed item cannot be sorted into one of those three buckets is the answer.
The bigger picture: how to answer any version
These questions vary the answer set, so memorizing one letter will not help. Instead, use the three-bucket test: for each option, ask "Is this transport, regulation, or protection?" If it fits, it is a real function. If it describes making something (hormones, enzymes, nerve signals) rather than carrying, balancing, or defending, it is the odd one out. This framework lets you answer correctly no matter how the options are worded. Remember that blood is a connective tissue whose job is to move things, keep the internal environment stable, and shield the body, not to manufacture the body's chemical messengers or fire its nerves.
Which of the following is NOT a function of blood?
Frequently asked
What are the three main functions of blood?
The three main functions of blood are transportation (carrying oxygen, carbon dioxide, nutrients, wastes, and hormones), regulation (maintaining body temperature, pH, and fluid balance), and protection (fighting infection with white blood cells and preventing blood loss through clotting).
Does blood produce hormones?
No. Hormones are produced by endocrine glands such as the thyroid, adrenal glands, pancreas, and pituitary. Blood transports those hormones from the glands to their target organs, but it does not manufacture them itself, so hormone production is not a function of blood.
How does blood regulate body temperature?
Blood absorbs heat from active tissues like muscles and redistributes it around the body. When you are hot, skin blood vessels dilate to release heat through the skin; when you are cold, they constrict to conserve it. This helps keep core temperature stable, a key part of homeostasis.
What are the protective functions of blood?
Blood protects the body in two main ways: white blood cells and antibodies defend against infection and foreign invaders, and platelets together with clotting factors form clots to stop bleeding after an injury, preventing excessive blood loss.