Endosteum

Endosteum is a thin layer of connective tissue that lines the inner surface of the bony tissue that forms the medullary cavity of long bones. This endosteal surface is usually resorbed during long periods of malnutrition, resulting in less dense bones and leading to diseases such as osteoporosis.

Structure

The endosteum is composed of a single layer of osteoprogenitor cells that differentiate into one of two types of bone cells: osteoblasts, which form bone, and osteoclasts, which resorb bone. The endosteum also contains osteocytes, mature bone cells that maintain the bone matrix.

Function

The endosteum plays a crucial role in the body's calcium homeostasis. It helps in the growth, repair, and remodeling of bones by providing new osteoblasts. The endosteum also plays a role in the body's response to hormones such as parathyroid hormone (PTH) and calcitonin.

Clinical significance

Diseases that affect the endosteum can lead to bone disorders. For example, osteoporosis is a condition in which the endosteum resorbs more bone than the osteoblasts can produce, leading to less dense and more fragile bones. Another condition, osteopetrosis, occurs when the osteoclasts are defective and can't resorb the bone, leading to overly dense and brittle bones.

See also

• Bone marrow
• Bone remodeling
• Osteoblast
• Osteoclast
• Osteocyte
• Osteoprogenitor cell

Endosteum

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