Bones and Bone Tissue

Overview of the Skeletal System

The skeletal system is composed of bones, joints, and supporting tissues. Bones are the primary organs of this system and are made up of osseous tissue, dense regular and irregular connective tissue (CT), and bone marrow.

• Bones: Rigid organs that form the framework of the body.

• Joints: Articulations where two or more bones meet.

• Supporting tissues: Include various types of connective tissue that provide structure and support.

Functions of the Skeletal System

Protection

The skeleton protects vital organs from injury. For example, the skull encases the brain, and the rib cage shields the heart and lungs.

• Protection of the brain by the skull.

• Protection of the thoracic organs by the rib cage.

Mineral Storage and Acid-Base Homeostasis

Bones serve as a reservoir for minerals, especially calcium (Ca2+) and phosphate (PO43−), which are essential for various physiological processes, including nerve conduction, muscle contraction, and acid-base balance.

• Mineral storage: Bones store Ca2+ and PO43− ions.

• Acid-base homeostasis: Bones help buffer the blood against excessive pH changes by absorbing or releasing alkaline salts.

Blood Cell Formation (Hematopoiesis)

Red bone marrow is the site of hematopoiesis, the process by which new blood cells are formed. This includes red blood cells, white blood cells, and platelets.

• Location: Red bone marrow, primarily found in flat bones and the ends of long bones.

• Function: Produces all blood cell types.

Example: Formation of erythrocytes (red blood cells) in the femur's red marrow.

Fat Storage

Yellow bone marrow, found in the medullary cavity of long bones, stores triglycerides, which serve as an energy reserve.

• Location: Yellow bone marrow in the medullary cavity.

• Function: Stores fat as triglycerides.

Movement

Bones act as levers for muscles, enabling movement. Muscles are attached to bones via tendons, and when muscles contract, they pull on bones to produce movement at joints.

• Attachment sites: Bones provide surfaces for muscle attachment.

• Movement: Muscles contract to move bones at joints.

Example: The femur and tibia form a lever system for walking.

Support

The skeleton provides structural support for the entire body, maintaining its shape and supporting the weight of tissues and organs.

• Framework: Bones form the body's framework.

• Weight support: The lower limb bones support the body's weight during standing and movement.

Summary Table: Functions of the Skeletal System