Bones and Bone Tissue Functions

Bones and Bone Tissue Functions

• Bones provide support for soft tissues and attachment points for tendons
• Bones protect internal organs like the heart and brain
• Bones store triglycerides for energy
• Bones store calcium and phosphorus, critical for bone strength and mineral balance
• Bones produce WBC, RBC, and platelets in spongy bone containing red bone marrow

Bones as Living Tissues

• Bones consist of osseous tissue, cartilage, dense irregular connective tissue, adipose tissue, and nervous tissue
• Each of these tissues have cellular activity that maintains bone health and mineral balance
• Osseous tissue contains osteocytes and osteoblasts that form new cells

Bone Classification by Shape and Compactness

• Long bones are greater in length than width, examples include the humerus, tibia, and femur
• Short bones are cube-shaped, like carpals and tarsals
• Irregular bones have complex shapes, examples are hip bones and vertebrae
• Flat bones are thin bones, examples include the cranial bones, sternum, ribs and scapulae
• Sesamoid bones are short bones found within tendons near joints; examples include the patella and sutural bones

Anatomy of Long and Flat Bones

• A long bone features a diaphysis, or shaft, containing a nutrient foramen for blood supply
• The metaphysis is between the diaphysis and epiphysis; it includes the epiphyseal line (or plate in growing bones)
• The epiphysis is at the bone's ends, containing spongy bone surrounded by compact bone
• Articular cartilage covers the epiphysis at joints
• The periosteum is the outer covering consisting of two layers and containing cells for bone growth and protection
• The endosteum lines the inner bone, with osteoblasts and osteoclasts
• The medullary cavity, found in the diaphysis, stores yellow fat in adults
• Hematopoietic tissue is located in the humerus, femur, and dipole of flat bones in adults

Histology of Compact and Spongy Bone

• Compact bone's structural unit is the osteon or Haversian system
• Each osteon has a central canal surrounded by lamellae
• Lacunae are found between lamellae and contain osteocytes
• Canaliculi connect adjacent osteocytes
• Volkmann's canals connect longitudinal Haversian canals and contain blood vessels and nerves
• Spongy bone has trabeculae and spaces, but no Haversian system
• Spongy bone consists of osteocytes, lamellae, and canaliculi

Chemical Composition of Bone

• Bones have an organic (osteoid) and inorganic matrix
• Osteoid comprises 33% of bone and is mostly collagen
• The inorganic part constitutes 65% of bone and contains mineral salts like calcium phosphate
• Collagen fibers provide resistance, while calcium provides hardness

Bone Formation (Osteogenesis)

• Intramembranous ossification forms bones from membranes, such as skull bones and the mandible
• Endochondral ossification forms bone from hyaline cartilage, producing long bones

Bone Growth in Length and Diameter

• Length: growth occurs at the epiphyseal plate in growing bones
• Diameter: growth occurs via the periosteum and endosteum

Bone Remodeling

• Osteoblasts are responsible for bone formation, while osteoclasts handle bone absorption
• Osteocytes are mature cells that maintain bone tissue
• Wolff's Rule dictates that bone becomes stronger with increased stress from muscle pull

Stages of Bone Fracture Repair

• Hematoma formation
• Fibrocartilaginous callus formation
• Bony callus formation
• Bone remodeling

Types of Fractures

• Comminuted: bone broken into 3+ pieces
• Compression: bone crushed
• Spiral: ragged break due to excessive twisting forces
• Epiphyseal: epiphysis separates from the diaphysis
• Depression: broken bone is pressed inward (skull)
• Greenstick: broken in half

Homeostatic Imbalances of Bones

• Osteoporosis: common in older women, bones become hollow

• Rickets: occurs in kids due to vitamin D and Calcium deficiency

• Osteomalacia: leads to soft bones and muscle weakness

• Paget's Disease: new bone tissue replaces the old, weakens bones, and affects the pelvis, spine, legs and skull

• Bone cancer: growth of cells that starts mostly in the thighbone

• Scoliosis: sideways curvature of the spine

• Kyphosis: curvature of the thoracic vertebrae, results in hunchback

• Lordosis: curvature of lumbar vertebrae

Joints Classification

• Fibrous joints are sututres, syndesmoses, and gomphoses
• Cartilaginous joints are synchondroses and symphyses
• Synovial joints can be gliding, hinge, pivot, condyloid, saddle and ball and socket

Synovial Joint Structure

• Contains a joint cavity filled with synovial fluid
• Synovial fluid is made through blood filtration
• The articular capsule has an outer fibrous layer and inner synovial membrane
• Articular cartilage is hyaline cartilage
• Reinforced by ligaments, their type depending on joint location

Bursae and Tendon Sheaths

• Bursae are flattened sacs containing synovial fluid lined by a synovial membrane
• Tendon sheaths act like bursae but are elongated and surround a tendon

Joint Inflammation Types

• Bursitis is inflamed Bursae
• Tendonitis is inflamed Tendons

Body Movements at Synovial Joints Types:

• Gliding occurs in intercarpals
• Angular movements are flexion/extension, abduction/adduction, and circumduction
• Rotation happens between the atlas and axis
• Rotation occurs in hip and shoulder joints
• Special movements are supination/pronation, inversion/eversion, protraction/retraction, elevation/depression, and opposition

Synovial Joints by Movement

• Gliding joint is intercarpal and intertarsal
• Hinge joint as in the elbow and knee
• Pivot joint examples are the brain and spine
• The condyloid joint is the wrist and knuckle
• Saddle joint is found in the thumb
• Ball and socket joint examples are the shoulder and hip

Homeostatic Imbalances of Joints

• Osteoarthritis causes progressive degeneration as we age

• Rheumatoid Arthritis is an autoimmune disorder that is bilateral

• Gouty Arthritis involves stiff and swollen joints

Trauma to Joints

• Sprains: muscles or tendons are overstretched
• Strain: overstretched ligament
• Luxation: dislocation of the joint
• Rheumatism: any painful joint condition

Knee Joint Structures

• The knee joint contains the femur, tibia, fibula, patella, cartilage, ligaments, muscles, and nerves
• It's the biggest joint in the body that connects the thigh to the shin (tibia) with hyaline and fibrocartilage
• It moves knee to support the body, stabilizes the body and helps with balance