6_Bones and Bone Tissue

Page 1: Bones and Bone Tissue

  • Is the femur a tissue or an organ?

    • The femur is classified as an organ due to its complex structure and function, consisting of multiple types of tissues including bone tissue, cartilage, blood vessels, and nerves.

  • Structure and Function of Bone Tissue:

    • Composed of a matrix that includes both organic components (collagen and cells) and inorganic materials (mineral salts like hydroxyapatite).

    • Main functions include:

      • Supports the body and provides shape.

      • Protects vital organs (e.g., skull protects the brain).

      • Facilitates movement by serving as points of attachment for muscles.

      • Assists in mineral storage (calcium and phosphorus).

      • Functions in hematopoiesis (blood cell formation) in the red bone marrow.

Page 2: Types of Cartilage

  • Three Types of Cartilage:

    • Hyaline Cartilage:

      • Most common type; provides support with flexibility. Found in joints, nose, trachea.

    • Elastic Cartilage:

      • Contains elastic fibers; maintains shape while allowing great flexibility. Found in the external ear and epiglottis.

    • Fibrocartilage:

      • Composed of thick bundles of collagen fibers; provides strong support and withstands pressure. Found in intervertebral discs and the pubic symphysis.

Page 3: Locations of Cartilage

  • Cartilage Locations:

    • External ear, intervertebral discs, pubic symphysis, meniscus of the knee, articular cartilage of joints, epiglottis, thyroid cartilage (larynx), nasal cartilage, trachea, cricoid cartilage, costal cartilage, respiratory tube cartilages.

    • Types of Skeletons:

      • Axial Skeleton

      • Appendicular Skeleton

      • Hyaline Cartilages, Elastic Cartilages, and Fibrocartilages

Page 4: General Characteristics of Skeletal Cartilage

  • Characteristics:

    • Tough yet flexible.

    • Avascular and lacks nerve fibers.

    • Extracellular matrix consists largely of chondroitin sulfate and hyaluronic acid, with fibers comprising up to 80% water.

    • Most cartilaginous structures surrounded by perichondrium (vascularized dense irregular connective tissue).

    • Cell Types:

      • Chondroblasts (immature cells that produce matrix).

      • Chondrocytes (mature cells found in lacunae).

Page 5: Bone Structure

  • Classification of Bones by Shape:

    • Long Bones: Longer than wide (e.g., humerus).

    • Short Bones: About as long as they are wide (e.g., patella).

    • Flat Bones: Broad and thin (e.g., sternum).

    • Irregular Bones: Do not fit into other classes (e.g., vertebrae).

    • Sesamoid Bones: Round and flat, usually found within tendons (e.g., patella).

Page 6: Functions of the Skeletal System

  • Primary Functions Include:

    • Protection of internal organs.

    • Support for body structure.

    • Facilitates movement by anchoring muscles.

Page 7: Mineral Storage and Acid-Base Homeostasis

  • Key Functions:

    • Stores minerals (e.g. Ca²⁺, PO₄³⁻) necessary for body homeostasis.

Page 8: Blood Cell Formation

  • Hematopoiesis:

    • Occurs in red bone marrow, which is found within spongy bone of long bones and within the diploe of flat bones.

Page 9: Fat Storage

  • Yellow Bone Marrow:

    • Functions as a triglyceride storage area.

Page 10: Movement and Muscle Attachment

  • Muscle Function:

    • Muscles attach to bones to produce movement across joints.

Page 11: Support

  • Skeletal Support Role:

    • Supports the weight of the body, maintains structural integrity.

Page 12: Overview of Functions of the Skeletal System

  • Protection of vital organs.

  • Storage of minerals such as calcium and phosphate for acid-base balance.

  • Blood cell production.

  • Triglyceride storage.

  • Provision for movement through muscle attachment.

Page 13: Bone Markings: Projections and Attachments

  • Bone Markings:

    • Tuberosity, Crest, and Line: Indicate sites for muscle and ligament attachment.

Page 14: Bone Markings: Joints and Attachments

  • Examples of Projections:

    • Head, Facet, Condyle, Ramus: assist in forming joints.

    • Depressions and Openings:

      • Groove, Fissure, Foramen: allow passage of blood vessels and nerves.

Page 15: Gross Anatomy of Long Bones

  • Structure of Long Bone:

    • Diaphysis (shaft), epiphyses (ends), periosteum (membrane).

    • Medullary cavity contains yellow marrow.

Page 16: Endosteum and Red Bone Marrow

  • Endosteum:

    • Lines medullary cavity and covers trabeculae of spongy bone.

  • Red Bone Marrow:

    • Site of hematopoiesis, more active in flat bones.

Page 17: Compact Bone Structure

  • Components of Compact Bone:

    • Ostons, Haversian canals, Volkmann's canals, osteocytes, lacunae, canaliculi provide structure and support.

Page 18: Structure of Short, Flat, Irregular Bones

  • General Structure:

    • Similar to long bones but less organized layers of compact and spongy bone.

Page 19: Microscopic Anatomy of Compact Bone

  • Osteons:

    • Basic structural units in compact bone consisting of lamellae, Haversian canals, and osteocytes.

Page 20: Blood Supply and Structure in Bone

  • Vascular System:

    • Central (Haversian) canals and Volkmann's canals connect blood supply to osteocytes.

Page 21: Chemical Composition of Bone

  • Inorganic Elements:

    • Mineral salts (hydroxyapatites) contribute to bone strength.

    • Organic Components:

    • Cells and osteoids provide flexibility.

Page 22: Bone Cell Types

  • Types of Bone Cells:

    • Osteogenic cells, osteoblasts, osteocytes, and osteoclasts all play roles in bone formation and maintenance.

Page 23: Osteogenesis / Ossification

  • Bone Development:

    • Begins with fibrous membranes and hyaline cartilage.

    • Involves intramembranous and endochondral ossification processes.

Page 24: Steps in Ossification

  • Process Overview:

    • Osteoblasts develop, secrete organic matrix, form hard callus.

Page 25: Formation of Bone Structures

  • Formation Process:

    • Early spongy bone formation leads to the creation of a bone callus.

Page 26: Development and Ossification in Long Bones

  • Bone Collar:

    • Created by osteoblasts; cartilage calcifies and chondrocytes die.

Page 27: Secondary Ossification Centers

  • Development of Ossification Centers:

    • Formation of spongy bone continues; medullary cavity develops as bones mature.

Page 28: Zones of Growth

  • Zones of the Epiphyseal Plate:

    • Proliferation, hypertrophy, calcification each play distinct roles in bone growth.

Page 29: Direction of Bone Growth

  • New Bone Formation:

    • New bone increases the length of bone in a longitudinal direction.

Page 30: Hormonal Control of Bone Growth

  • Hormonal Influences:

    • Growth hormone stimulates epiphyseal plate activity.

    • Testosterone and estrogen regulate growth patterns during puberty.

Page 31: Bone Remodeling

  • Continuous Change:

    • Bone undergoes remodeling for maintenance and adaptation to stress or injury.

    • Bone deposition and resorption by osteoblasts and osteoclasts, respectively.

Page 32: Processes of Bone Remodeling

  • Roles of Cells:

    • Osteoblasts build new bone, while osteoclasts break down old bone.

Page 33: Bone Deposition

  • Process:

    • Carried out primarily by osteoblasts as they secrete bone matrix.

Page 34: Bone Resorption

  • Mechanism:

    • Osteoclasts degrade bone matrix using hydrogen ions and enzymes for mineral release.

Page 35: Bone Resorption Process

  • Analysis of Resorption:

    • Osteoclasts absorb broken down components of the bone matrix for reformation.

Page 36: Remodeling Response to Stress

  • Adaptive Remodeling:

    • Bone thickness increases under compression; affected by physical stress.

Page 37: Influencing Factors on Remodeling

  • Influencers:

    • Hormones, age, vitamin/mineral intake affect remodeling rates.

Page 38: Nutritional Factors in Bone Remodeling

  • Dietary Importance:

    • Sufficient vitamin C, D, K, and protein are critical for healthy remodeling.

Page 39: Response to Low Calcium Levels

  • Mechanism of Response:

    • Parathyroid glands regulate calcium levels through osteoclast activation and hormone release.

Page 40: Summary of Influencing Factors

  • Homeostatic Controls for Remodeling:

    • Factors like dietary intake, hormones, and physical activity play roles in bone health.

Page 41: Bone Repair Mechanisms

  • Fracture Types:

    • Simple vs. compound fractures; the bone's protective function is often tested during injury.

Page 42: Types of Fractures Breakdown

  • Fracture Types Include:

    • Spiral, compression, comminuted, avulsion, and greenstick fractures with varying severity.

Page 43: Fracture Healing Process

  • General Healing Steps:

    • Hematoma formation, soft callus formation, followed by bony callus development.

Page 44: Transition from Soft to Hard Callus

  • Callus Formation:

    • Transition from soft to hard calluses to restore bone integrity.

Page 45: Homeostatic Imbalances of Bone

  • Conditions Affecting Bone Health:

    • Conditions like rickets, osteomalacia, and osteoporosis affect bone density and strength.