Bones are an ext than just the scaffolding the holds the human body together. Skeletal come in all shapes and also sizes and have numerous roles. In this article, we define their function, what they space made of, and also the species of cells involved.

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Despite very first impressions, bones room living, active tissues that room constantly being remodeled.

Bones have many functions. They support the body structurally, defend our critical organs, and enable us come move. Also, they provide an environment for bone marrow, whereby the blood cells space created, and also they act together a warehouse area for minerals, particularly calcium.

At birth, us have around 270 soft bones. Together we grow, some of these fuse. Once we with adulthood, we have actually 206 bones.

The biggest bone in the human being body is the thighbone or femur, and also the the smallest is the stapes in the center ear, i m sorry are just 3 millimeter (mm) long.

Bones are mostly made that the protein collagen, which develops a soft framework. The mineral calcium phosphate hardens this framework, providing it strength. Much more than 99 percent that our body’s calcium is organized in our bones and also teeth.

Bones have an inner structure comparable to a honeycomb, which provides them strict yet relatively light.

The framework of bones

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Bones space composed of two species of tissue:

1. Compact (cortical) bone: A difficult outer layer the is dense, strong, and durable. It makes up approximately 80 percent the adult bone mass.

2. Cancellous (trabecular or spongy) bone: This is composed of a network that trabeculae or rod-like structures. The is lighter, less dense, and an ext flexible 보다 compact bone.

Also uncovered in bones:

osteoblasts and also osteocytes, responsible for creating boneosteoclasts or bone resorbing cellsosteoid, a mix the collagen and also other proteinsinorganic mineral salts within the matrixnerves and blood vesselsbone marrowcartilagemembranes, consisting of the endosteum and periosteum

Below is a 3D map that the skeleton system. Click come explore.

Bone cells

Bones are not a revolution tissue yet need to it is in constantly maintained and remodeled. There are three main cell varieties involved in this process.

Osteoblasts: These space responsible for making new bone and repairing larger bone. Osteoblasts create a protein mixture dubbed osteoid, i beg your pardon is mineralized and becomes bone. They additionally manufacture hormones, consisting of prostaglandins.

Osteocytes: These are inactive osteoblasts the have end up being trapped in the bone the they have actually created. They maintain connections to various other osteocytes and also osteoblasts. Lock are necessary for interaction within bone tissue.

Osteoclasts: this are huge cells with much more than one nucleus. Their project is to malfunction bone. They release enzymes and acids to dissolve mineral in bone and digest them. This procedure is called resorption. Osteoclasts assist remodel injured bones and also create pathways because that nerves and blood ship to take trip through.

Bone marrow

Bone marrow is discovered in almost all bones where cancellous bone is present.

The marrow is responsible because that making roughly 2 million red blood cell every second. It additionally produces lymphocytes or the white blood cells affiliated in the immune response.

Extracellular matrix

Bones are basically living cells embedded in a mineral-based organic matrix. This extracellular matrix is make of:

Organic components, being mostly form 1 collagen.

Inorganic components, including hydroxyapatite and also other salts, such as calcium and also phosphate.

Collagen gives bone the tensile strength, specific the resistance to being pulled apart. Hydroxyapatite offers the skeleton compressive toughness or resistance to gift compressed.

What carry out bones do?

Bones offer several an important functions:

Bones offer several an essential functions:


Bones provide a structure to support the body. Muscles, tendons, and also ligaments attach to bones. There is no anchoring to bones, muscles could not relocate the body.

Some bones protect the body’s interior organs. For instance, the skull protects the brain, and also the ribs defend the heart and lungs.


Cancellous bone to produce red blood cells, platelets, and also white blood cells. Also, defective and also old red blood cells are ruined in bone marrow.


Share ~ above PinterestElectron microscope photo of trabecular bone (x100 magnification).Image credit: Sbertazzo

Storing minerals: bones act as a reserve because that minerals, particularly calcium and phosphorous.

They likewise store some development factors, such together insulin-like development factor.

Fat storage: fat acids have the right to be save on computer in the bone marrow adipose tissue.

pH balance: Bones can release or absorb alkaline salts, helping blood to remain at the ideal pH level.

Detoxification: Bones deserve to absorb hefty metals and also other toxic facets from the blood.

Endocrine function: Bones release hormones the act ~ above the kidneys and also influence blood sugar regulation and fat deposition.

Calcium balance: Bones can raise or alleviate calcium in the blood by developing bone, or break it under in a procedure called resorption.

There are five types of skeleton in the human body:

Long bones: this are mostly compacted bone with little marrow and include most of the skeletal in the limbs. These bones have tendency to assistance weight and help movement.

Short bones: only a thin layer that compact bone, these encompass bones that the wrist and ankle.

Flat bones: typically bones that room thin and curved. Castle consist of two external layers of compact bone and also an inner great of spongy bone. Flat bones incorporate most that the skeletal of the skull and the sternum or breastbone. They have tendency to have a protective role.

Sesamoid bones: this are embedded in tendons, such as the patella or kneecap. They defend tendons native wear and also stress.

Irregular bones: together their surname implies, these space bones that perform not fit into the first four categories and also are an unusual shape. They include the skeletal of the spine and also pelvis. They are regularly protecting guts or tissues.

Bones that the skeleton are split into 2 groups:

Appendicular skeleton — skeletal of the limbs, shoulders, and also pelvic girdle.

Axial skeleton — skeletal of the skull, vertebral column, thoracic cage.

Bone is always being remodeled. This is a two-part process:

1. Resorption once osteoclasts malfunction and eliminate bone.

2. Formation when new bone organization is set down.

An estimated 10 percent of an adult’s skeleton is replaced each year.

Remodeling enables the body to deal with damaged sections, reshape the skeleton throughout growth, and regulate calcium levels.

If one part of the skeleton is put under boosted stress over time, because that instance, during sport or exercise, the sections of bone under many pressure will come to be thicker in response.

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Remodeling is under the regulate of number of hormones, consisting of parathyroid hormone, calcitonin, vitamin D, estrogen in women, and testosterone in men.