Anatomy of Long Bones

Long Bone Anatomy

Articular cartilage is a thin layer of hyaline cartilage that protects the ends of our bones from friction when we move and shock when we put weight on our joints.

​​Articular Cartilage

As people age, this articular cartilage sometimes begins to wear out and fade. When this happens, the joints affected become painful and swollen. This is known as osteoarthritis.

​​Arthritis

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Articular cartilage is a type of ​

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. It is found at the ​

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of long bones. It helps ​

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our bones from friction and stress from moving and weight bearing. ​

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is a condition that causes painful, swollen joints because the articular cartilage is ​

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.

The ends of our bones are made of a special type of bone called spongy bone. It has microscopic spaces filled with red bone marrow.

​​Ends of Bones

Red bone marrow is a soft tissue full of stem cells.

Red Bone Marrow

​The stem cells in red bone marrow produce red blood cells, most white blood cells, and platelets.

​​Stem Cells

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Red bone marrow is found in the ​

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of bone in a special bone called ​

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. Red bone marrow is full of ​

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which produce ​ red blood cells, most ​

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blood cells, and ​

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.

​The middle, or shaft, of long bones are made of compact bone. The shaft is also called the diaphysis. Compact bone has very few spaces, and is much stronger than spongy bone.

​​Compact Bone

​Compact bone is full of tightly packed units called osteons.

​​Osteons

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The ​

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of long bones are made of ​

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. Compact bone is made of tightly packed units, called ​

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. Because of these units, compact bone is much ​

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than spongy bone.

Growth plates are actually called epiphyseal plates. This is where new bone is created and a bone grows in length (not width). Epiphyseal plates are made of hyaline cartilage which ossified (turns to bone) repeatedly as you grow in height.

Growth Plates

In the diaphysis of bones is a medullary cavity. It is lined with a membrane known as the endosteum. Inside this cavity you can find yellow marrow.

Medullary Cavity

​Yellow marrow is primarily adipose tissue. This tissue can be used as an emergency energy reserve.

Yellow Marrow

Did you know? In an emergency situation where your body loses significant amounts of blood, the yellow marrow in bones can quickly transform to red marrow to boost blood cell formation!

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Yellow Marrow & Emergencies

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Growth plates are called ​

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plates. This is where new ​

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is created and a bone grows in ​

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. Epiphyseal plates are made of ​

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which ​

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(turns to bone) repeatedly as you grow in height.

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In the diaphysis of bones is a ​

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cavity. It is lined with a membrane known as the ​

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. Inside this cavity you can find ​

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.

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​Yellow marrow is primarily ​

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tissue. This tissue can be used as an emergency energy reserve. In an emergency where your body loses significant amounts of ​

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, the yellow marrow in bones can quickly transform into ​

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to boost ​

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!

Long bones need to be able to send new blood cells into the main blood supply. Bones also need to receive blood so that nutrients, oxygen and hormones can reach the bone inside. Blood vessels enter the bone through the nutrient foramen.

​​Nutrient Foramen

The outside of a long bone is covered with a connective tissue membrane known as the periosteum. It is a very vascular membrane. It is full of osteoblasts, cells that grow new bone. This growth increases a bones width.

Periosteum

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The outside of a long bone is covered with a connective tissue membrane known as the ​

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. It is a very vascular membrane that is full of ​

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, cells that grow new bone. This growth increases a bone's ​

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.

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Long bones need to be able to send new blood cells into the main blood supply. Bones also need to receive blood so that ​

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, oxygen and hormones can reach the bone inside. Blood vessels enter the bone through the ​

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.