Possess mostly red marrow, found throughout most bones.
Adults:
Red marrow is replaced by yellow marrow with maturity.
Appearance of yellow marrow attributed to the abundance of adipose cells.
Location of Red Marrow in Adults:
Found primarily in:
Skull
Vertebrae
Ribs
Sternum
Proximal femur and humerus
Yellow Bone Marrow
Function:
Serves primarily as fat storage.
Ceases hematopoiesis, except in emergencies.
Microscopic Bone Structure
Compact Bone:
Composed of Haversian systems.
Features a central canal (Haversian canal) surrounded by concentric rings of matrix.
Contains osteocytes within their lacunae.
Osteocyte Nourishment
Nutrition Mechanism:
Through a network called the lacunar-canalicular system, which interconnects canals (canaliculi) transporting nutrients from blood vessels to osteocytes situated in lacunae.
Haversian System
Description:
Composed of Haversian canals within compact bone, located internally to the periosteum and endosteum.
Structure of Long Bone
Layers (Superficial to Deep):
Periosteum
Compact Bone
Endosteum
Spongy Bone
Articular Cartilage
Metaphysis
Diaphysis
Medullary Cavity containing yellow marrow
Periosteum
Function and Structure:
Covers the outer surface of bones (except at joint surfaces) and contains blood vessels, nerves, and lymphatics necessary for bone nourishment.
Tendons and ligaments attach to it.
Endosteum
Definition:
Membrane lining the marrow cavity and Haversian canals.
Spongy Bone Structure
Comparison with Compact Bone:
Situated deep to compact bone, less hard than compact but still firm.
Joints
Definition:
Points where two bones connect.
Characteristics:
Smooth cartilage facilitates movement.
Some joints are movable, while others are fixed.
Joints Structure
Components of Synovial Joint:
Smooth cartilage
Synovial membrane (produces synovial fluid)
Ligaments
Ligaments vs. Tendons
Ligament:
Connects bone to bone (the 'L' is in 'b').
Tendon:
Connects muscle to bone.
Joints Classification
Structural Types of Joints:
Fibrous Joints:
Immovable or slightly movable, connected by fibrous connective tissue (e.g., skull sutures).
Cartilaginous Joints:
Partially movable, joined by cartilage (e.g., intervertebral discs).
Synovial Joints:
Freely movable with fluid-filled capsules (e.g., knee joint).
Functional Classification of Joints
Synarthrosis:
Immovable joints.
Amphiarthrosis:
Slightly movable joints.
Diarthrosis:
Freely movable joints.
Types of Synovial Joints
Ball-and-Socket:
One bone fits into a socket-like depression in another (e.g., hip, shoulder).
Hinge:
One bone moves back-and-forth like a door (e.g., elbow, knee).
Pivot:
One bone rotates around another (e.g., neck).
Gliding:
Bones slide over each other (e.g., wrist).
Condyloid:
Oval-shaped movement (e.g., wrist).
Saddle:
Combination of movements (e.g., thumb).
Bone Disorders
General Information:
Disorders are often due to abnormalities in bone resorption.
Men's bones are typically denser than women's due to testosterone effects.
Men experience faster healing; however, they are also more likely to sustain fractures due to sports activities.
Osteoporosis
Definition:
Condition that weakens bones, making them brittle.
Risk Factors:
Can result in fractures from moderate stress (bending or coughing).
Affects all races but is most prevalent in post-menopausal white and Asian women.
Osteopenia
Description:
A precursor to osteoporosis, involves slower bone formation than resorption.
Causes:
Low calcium intake
Smoking
Estrogen deficiency
Certain medications
Osteopetrosis
Description:
A rare inherited disorder leading to bone brittleness and deformities.
May cause scoliosis, vision problems, fracture risks, infections, and stunted growth.
Osteolysis
Description:
Condition where bones become thin and weak, often associated with the use of prosthetics (referred to as "cement disease").
Bone Cancer
Description:
An abnormal growth of tumors in bone tissue, possible causes include:
Genetic conditions
Radiation therapy
Previous tumors
Metastasis from other cancers
Ainhum
Description:
A rare condition causing autoamputation of a toe due to pressure from toughening tissues.
Symptoms begin with slight pain due to nerve pressure.
Prevalent among individuals of African descent and those with a history of walking barefoot since childhood.