Bone Function: What Your Bones Do And Why They're Essential

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HealthlineSubscribeBone Function: Why Do We Have Bones?

Medically reviewed by William Morrison, M.D. — Written by Jill Seladi-Schulman, Ph.D. on June 17, 2019

Function
Types of bone
Bone tissue
Bone cells
Takeaway

Human beings are vertebrates, meaning that we have a spinal column, or backbone.

In addition to that backbone, we also have an extensive skeletal system that’s made up of bones and cartilage as well as tendons and ligaments.

In addition to providing a framework for your body, bones also serve many other important biological functions, such as protecting your internal organs from harm and storing essential nutrients.

Read on to explore the diverse functions and types of bones.

What does bone do?

Bones serve many vital functions in your body, including:

Support

Bone provides a rigid framework as well as support for other parts of your body.

For example, the larger bones of the legs offer support to your upper body while you’re standing up. Without our bones, we’d have no defined shape.

Movement

Bones also play an important role in the movement of your body, transmitting the force of muscle contractions.

Your muscles attach to your bones via tendons. When your muscles contract, your bones act as a lever while your joints form a pivot point.

The interaction of bones and muscles contributes to the wide range of movements your body is capable of making.

Protection

Your bones also protect many of your internal organs. Good examples of this include the way your rib cage surrounds organs such as your heart and lungs or how the bones of your skull surround your brain.

Blood cell generation and maintenance

The many cells of your blood — red blood cells, white blood cells, and platelets — are formed within your bones. This process is called hematopoiesis, and it occurs in a part of your bone marrow called the red marrow.

Storage

Important minerals, such as calcium and phosphorus, are stored within your bones. When your body needs more of these resources, they can be released back into your bloodstream for use.

In addition to red marrow, bones also contain another type of marrow called yellow marrow. This is where some fat tissue is stored. The fats in this tissue can be broken down and used for energy if required.

5 types of bone

The bones of your body are divided into five different types based on their shape and function.

Long bones

As their name implies, long bones are longer than they are wide. Some examples include:

femur (thigh bone)
humerus (upper arm bone)
bones of your fingers and toes

The function of long bones is centered on supporting the weight of your body as well as facilitating the movement of your body.

Short bones

Short bones have very equal proportions and are roughly shaped like a cube. Examples can be found in the bones of your wrists and ankles.

Short bones provide stability to the wrist and ankle joints and also help facilitate some movements.

Flat bones

Flat bones aren’t actually flat, but thin and slightly curved. Examples of flat bones include your:

cranial bones
scapula (shoulder bone)
ribs

Flat bones often serve to protect your internal organs. Think of how your cranial bones tightly surround your brain.

Flat bones can also serve as points of attachment for your muscles. Your shoulder bone is a good example of this.

Irregular bones

The irregular bones of your body have varied shapes that are often complex. Examples include:

vertebrae
pelvic bones
the many bones of your face

Like flat bones, the function of irregular bones is to protect various parts of your body. For example, your vertebrae protect your spinal cord.

Sesamoid bones

Sesamoid bones are small and round in shape. They’re found throughout the body, mostly in the hands, feet, and knees.

Interestingly, their placement can vary from person to person. The patella (kneecap) is an example of a prominent sesamoid bone in the body.

Sesamoids are bones that form within a tendon and bones surrounded by tendons, which connect muscle to bone. They help to protect the tendons from wear and tear and to relieve pressure when a joint is used.

They give a mechanical advantage to the muscles and tendons in which they are located.

Types of bone tissue

Your bones are composed of two different types of tissue.

Compact

The compact bone is the outer shell of the bone. It’s made up of many closely packed layers of bone tissue.

Compact bone contains a central canal that runs the length of the bone, often called a Haversian canal. Haversian canals allow blood vessels and some nerves to reach into the bone.

Spongy

Spongy bone isn’t as dense as compact bone and looks very much like a honeycomb. It contains cavities that hold the red or yellow bone marrow.

Spongy bone is also important for movement. If all of your bone tissue was compact, you’d probably be too heavy to move! Spongy bone also helps to absorb shock and stress from movement.

Types of bone cells

There are a variety of different cells present in your bones.

Mesenchymal stem cells

These are stem cells found in your bones. They can develop into a variety of different cell types, including osteoblasts.

Osteoblasts

These cells originate from mesenchymal stem cells. They work to deposit collagen and minerals that will eventually form mature bone.

When they’ve accomplished this, osteoblasts can become a cell on the bone surface, develop into an osteocyte, or die by a natural process called apoptosis.

Osteocytes

Osteocytes are trapped within the bone tissue and are the most prevalent cell type in mature bone tissue. They monitor things such as stress, bone mass, and nutrient content.

They’re also important for signaling during bone remodeling, the process of bone resorption and generation of new bone tissue that can follow.

Osteoclasts

Osteoclasts are large cells. They secrete a variety of ions and enzymes that allow bone tissue to be resorbed. The material that has been resorbed can then be used to create new bone tissue.

The takeaway

Your bones do so much more than provide support for your body. They facilitate movement, provide protection to internal organs, and are important for blood cell formation and nutrient storage.

Your bones are classified according to their size and function. On the inside, bones contain a variety of different tissues and cells. All of these components work together to make your bones the multifunctional tissue that they are.

How we reviewed this article:

SourcesHistoryHealthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Anatomy and physiology. (2013).https://opentextbc.ca/anatomyandphysiology/
Introduction to the skeletal system. (n.d.).https://training.seer.cancer.gov/anatomy/skeletal/
Jagannathan-Bogdan M, et al. (2013). Hematopoiesis. DOI:https://doi.org/10.1242/dev.083147
Rowe P, et al. (2019). Physiology, bone remodeling.https://www.ncbi.nlm.nih.gov/books/NBK499863/#article-18453.s1
Structure of bone tissue. (n.d.).https://training.seer.cancer.gov/anatomy/skeletal/tissue.html
What is bone? (n.d.).https://www.bones.nih.gov/health-info/bone/bone-health/what-is-bone

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Medically reviewed by William Morrison, M.D. — Written by Jill Seladi-Schulman, Ph.D. on June 17, 2019

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