Functions of Bones and Bone Marrow

Functions of Bones

• Red marrow produces blood cells
• Red marrow is essential for blood cell formation
• Bones support the body
• Bones protect organs
• Bones allow movement
• Bones store Calcium
• Bones store Phosphate
• Bones regulates blood sugar
• Bones regulate fat storage
• Bones influence calcium levels
• Bones influence metabolic hormones like osteocalcin
• Mineralization increases bone strength to resist fractures
• Bones provide structural support to the body

Osteocalcin

• Osteocalcin regulates blood sugar
• Osteocalcin regulates fat storage
• Osteocalcin affects insulin secretion
• Osteocalcin affects insulin sensitivity
• Osteocalcin regulates energy metabolism

Bone Marrow

• Yellow marrow stores fat
• Yellow marrow is found in the medullary cavity of long bones
• Bone marrow is responsible for blood cell production
• Red marrow produces blood cells
• Red marrow is active in Hematopoiesis

Processes Supported by Bone Mineral Storage

• Nerve impulse transmission requires calcium
• Muscle contractions require calcium
• Blood clotting requires calcium

Muscle Attachment Points

• Tendons connect muscle to bone
• Bones serve as levers for muscle attachment
• A tubercle is a small rounded projection used for muscle and ligament attachment
• The periosteum serves as an anchoring site for tendons and ligaments

Increased Osteoclast Activity

• Excessive bone resorption leads to weakened bones
• Osteoporosis results from low bone mass due to high resorption

Hormones Affecting Bone Metabolism

• Growth hormone regulates bone growth and metabolism
• Insulin regulates bone growth and metabolism
• Parathyroid hormone regulates bone growth and metabolism
• These hormones regulate calcium homeostasis

Calcium

• Calcium is essential for nerve impulses
• Calcium is essential for muscle contractions
• Calcium is essential for clotting
• Bones release and store calcium as needed
• Calcium is released into the bloodstream as needed

Osteoblasts

• Osteoblasts deposit new bone matrix
• Osteoblasts secrete a hormone that helps regulate insulin

Bone Structure

• The epiphyseal plate is found at the epiphysis of long bones
• The epiphyseal plate is responsible for lengthwise growth during development
• Osteons are composed of central (Haversian) canals
• Osteons are composed of canaliculi (connecting channels)
• Osteons are composed of lacunae, which house osteocytes
• Spongy bone (trabecular bone) is made of trabeculae

Bone Surfaces

• The endosteum lines internal bone surfaces like the medullary cavity and trabeculae.
• The periosteum is a dense connective tissue membrane covering the external surface of bones except at joint surfaces.

Bone Makeup

• The organic matrix includes collagen
• Inorganic salts (mainly calcium phosphate) provide hardness
• Bone matrix consists primarily of collagen and calcium phosphate

Bone Markings

• A foramen is an opening in bone that allows the passage of nerves and blood vessels.
• A tubercle is a small rounded projection used for muscle and ligament attachment

Bone Types

• Flat bones include skull bones
• Flat bones include sternum
• Flat bones include ribs
• Vertebrae are classified as irregular bones
• Short bones are cube-shaped
• Short bones are found in the wrists (carpals)
• Short bones are found in the ankles (tarsals).
• The diaphysis is the shaft of a long bone
• The expanded ends of a long bone are called epiphyses
• Appositional growth increases bone width by adding layers to the outer surface.

Bone Cells and Canals

• Osteoclasts secrete acids and enzymes to break down bone matrix during bone remodeling.
• Osteons are the functional unit of compact bone, surrounding the central canal.
• Lacunae contain mature bone cells called osteocytes.
• Osteoblasts are bone-forming cells found on bone surfaces.
• Canaliculi are small channels that connect lacunae and allow osteocytes to exchange nutrients and waste.
• The central (Haversian) canal carries blood vessels and nerves that nourish bone cells.

Cartilage

• Elastic, hyaline, and fibrocartilage are the three types of cartilage
• Endosteum is a membrane, not cartilage
• The perichondrium is a dense connective tissue surrounding cartilage, aiding in growth and repair.
• Trabeculae form the lattice structure of spongy bone.
• Osteons are only found in compact bone
• The epiphyseal plate is found in growing bones
• Once fused, the epiphyseal plate becomes the epiphyseal line
• In adults, the medullary cavity primarily contains yellow bone marrow (fat), not spongy bone.