The Skeletal System
Structure and Function of Bones:
Bone tissue serves several crucial functions in addition to providing structure and support to the body. It protects vital organs, produces blood cells and stores minerals. These functions are facilitated by several types of bone tissue, primarily cortical bone and cancellous bone.
Types of bone tissue
- Cortical bone (compact bone) :
Forms the hard outer layer of bones and constitutes approximately 80% of the total bone mass.
It provides strength and resistance to bending and torsion.
It is formed by microscopic units called osteons, consisting of a central canal surrounded by concentric rings (lamellae) of matrix.
It contains osteocytes housed in small spaces called lacunae, connected by small canals known as canaliculi that facilitate the exchange of nutrients. - Cancellous bone (spongy bone) :
Located mainly inside the bones and constitutes approximately 20% of the total bone mass.
It is characterized by a porous structure that allows flexibility and a greater surface area, improving metabolic activities such as mineral exchange.
It contains trabeculae, which are thin plates or struts that support the bone structure and house the red bone marrow, where hematopoiesis (the production of blood cells) takes place. - Bone structure and remodeling
Bone structure is dynamic. The process of bone remodeling involves the continuous removal of old bone tissue by osteoclasts and the formation of new bone by osteoblasts. This remodeling is essential for:
Repair of microdamage.
Adjustment of bone structure to meet changing mechanical demands. - Bone marrow
Bone marrow plays a critical role in hematopoiesis:
Red bone marrow : found in cancellous bone and is responsible for producing red blood cells, white blood cells and platelets.
Yellow bone marrow : composed mainly of fat; can be converted back to red marrow in emergency situations to increase blood cell production.
Bones are rigid organs that constitute part of the endoskeleton of vertebrates.
Functions include:
Support: Providing structural support for the body.
Protection: Shielding vital organs (e.g., the skull protects the brain).
Movement: Working with muscles to move the body.
Blood Cell Production: Producing blood cells in the bone marrow.
Types of Bones:
Long Bones: Found in arms and legs (e.g., femur).
Short Bones: As wide as they are long, providing stability with little movement (e.g., carpals of the wrist).
Flat Bones: Protect internal organs (e.g., ribs, skull).
Irregular Bones: Have complex shapes (e.g., vertebrae).
Sesamoid Bones: Embedded within tendons (e.g., patella)