Anatomy
Functions of the skeletal system: including one most students miss.
“List the functions of the skeletal system” shows up on almost every first A&P exam. Most students can name support and movement. Fewer remember blood cells and mineral storage. Almost nobody expects the last one: your bones make a hormone. Here are all of them, with the example that makes each one stick.
The short answer
The skeletal system has 7 main functions: support, protection, movement, mineral storage, blood cell production, fat storage, and hormone production. The one students usually miss is the last: bone cells release a hormone called osteocalcin, which gives the skeleton an endocrine role.
1. Support
The skeleton is the frame the rest of the body hangs on. Without it, your muscles and organs would have nothing to hold their shape against.
2. Protection
This one is easiest to remember as three pairs:
- The skull protects the brain.
- The ribs protect the heart and lungs.
- The vertebral column protects the spinal cord.
In lessons, I explain these three, move on, then ask a few minutes later: “What does the vertebral column protect?” Try it on yourself tomorrow.
3. Movement
Bones don’t move on their own. Muscles attach to them, and when a muscle contracts, it pulls the bone it is attached to, while the joint acts as the pivot. This is why so much of anatomy is about attachment points: where a muscle attaches tells you what movement it makes.
4. Mineral storage
Bone is a store of calcium and phosphate. When your blood needs more calcium, some is released from bone. This is the link between the skeletal system and physiology questions about calcium balance.
5. Blood cell production
Red bone marrow, inside certain bones, produces red blood cells, white blood cells and platelets. The process is called haematopoiesis (hematopoiesis in American spelling). Expect the term on your exam.
6. Fat storage
Yellow bone marrow stores fat, which the body can use as an energy reserve. It is the function students most often leave off the list, after the next one.
7. Hormone production: the one most students miss
Bones have an endocrine function. Bone cells release a hormone called osteocalcin, and researchers have linked it to how the body handles blood sugar, among other effects.
“Your bones make a hormone.”
When I tell students this, they are usually shocked. That surprise is useful: I mention it once mid-lesson, ask about it again at the end, and they remember it.
Blood cells come from red marrow. Fat is stored in yellow marrow. Exams love to swap them.
New to A&P? My beginner’s guide covers the skeletal system alongside three other body systems.