Bone Histology Lecture Slides PDF

PAS 313: Human Anatomy Lecture 8: Bone Histology Dr. Joseph Costa, PhD Department of Pathology and Anatomical Sciences 1 The Skeletal System I. General Functions A. Support 1. Structural framework 2. Supports/supported by soft...

PAS 313: Human Anatomy Lecture 8: Bone Histology Dr. Joseph Costa, PhD Department of Pathology and Anatomical Sciences 1 The Skeletal System I. General Functions A. Support 1. Structural framework 2. Supports/supported by soft tissues (muscle, organs) B. Protection 1. Internal organs C. Movement 1. Created by contracting muscle 2. Tendon pulls at bones creating movement at joints 2 D. Storage 1. Fat stored in yellow marrow found in medullary cavity (internal hollow space) 2. Major site of calcium and phosphate storage 3. Other minerals are stored in smaller amounts 4. All can be withdrawn when needed E. Blood cell production 1. Red marrow: Blood cells and platelets 3  II. The Matrices A. Inorganic Matrix: “non-living” portion 1. Accounts for 2/3 of the total bone mass 2. Calcium and phosphate salts form crystals of hydroxyapatite around collagen 3. Provides bone with strength and rigidity. Resists compression. 4 B. Organic Matrix: “Living portion” 1. Accounts for 1/3 of the total bone mass 2. Composed of cells, collagen and intercellular matrix 3. Provides tensile strength & flexibility: withstand twisting, stretching. 5  III. Gross organization of bone A. Inner and out membranes 1. Periosteum: A protective outer covering of CT. Rich nervous and vascular supply 2. Endosteum: Inner lining of bone. 6  III. Gross Organization of Bone B. Matrix Arrangement 1. Compact bone Dense, solid outer surface. Primary component of long bone shafts 2. Spongy bone (AKA trabecular bone) Resembles sponge: wide “holes” “Holes” are filled with red and yellow marrow 7  Compact vs. Spongy Bone Spongy bone Compact bone Outer surface: Compact bone 8 C. Bone shape and internal arrangement 9  C. Bone shape and internal arrangement 1. Flat bones layer of spongy bone surrounded by two plates of compact bone Examples: Cranium Sternum Ribs Body of scapula 10 2. Long Bones a. Greater length than width b. Shaft = compact bone (diaphysis) c. Ends = primarily spongy d. Examples: a. Femur b. Humerus c. metacarpals 11 3. Short bones a. Cuboid shape b. Spongy bone surrounded by compact bone (like sponge candy) c. Carpal & tarsal bones 12 3. Irregular a. Doesn’t fall into other categories: Vertebrae 13 D. Structure of a Long Bone 14  D. Structure of a Typical Long Bone 1. Diaphysis a. Shaft b. Primarily compact bone 2. Epiphysis a. Ends of long bone b. Primarily spongy bone 15 1. Epiphyseal plate (metaphysis) a. Plate of cartilage in growing bones b. Lengthwise bone growth 2. Medullary cavity a. Cavity within diaphysis b. Mostly yellow marrow (in adults) 16 5. Articular Cartilage: Protective Hyaline cartilage on ends of the long bones 6. Nutrient Vessels: - Blood vessels that penetrate bone to supply nutrients 17  IV. Bone Cells A. Osteocytes 1. Mature bone cells 2. Reside in cell-sized spaces: lacunae 18 B. Osteoblast 1. Bone forming cell. Produces osteoid (organic matrix component) 19 C. Osteoclast 1. Resorption: Breaks down bone w/ enzymes for release into blood 20 D. Chondroblasts 1. Cells that produce cartilage 2. Play a role in bone development and growth E. Chondrocytes: Mature cartilage cells 21  V. Micro-organization: The Haversian System : functional/structural unit in mature bone. 1. Long, cylindrical structures (green column) 2. Run parallel to long axis of the bone 3. Like weight bearing pillars 4. Arrangement allows bone to withstand torsion (twisting) and compression forces 22  Osteon/Haversian system: Structural Components 1. Concentric Lamellae Concentric layers of bone (circles within circles) Surround haversian canal 2. Haversian Canal Contains nerves & blood vessels 4 2 3. Canaliculi (not visible): “Small channels”. Communication between osteocytes in lacunae 4. Perforating (Volkman’s) Canals 1 90° to haversian canals Communication between inside/outside bone 23  Osteocyte in lacuna Central Canal Canaliculi 24 VI: Osteogenesis: Bone formation and development The formation of new bone occurs through two processes: 1. Ossification: a. Process of bone formation b. Osteoblasts secrete osteoid (organic component of bone) 2. Calcification: a. Deposition of insoluble calcium salts (inorganic component) b. Results in the hardening of bone 25 There are Two Types of Bone Formation 1. Intramembranous 2. Endochondral 26 1. Intramembranous bone formation a. Occurs in fetal development b. Ossification in fibrous CT membrane c. Bones that are required for protection d. Ex: flat bones of the skull, body of the scapula, ilium 27 2. Endochondral bone formation: a. Begins with a hyaline cartilage model b. Osteoblasts gradually replace cartilage with bone. May occur up to the age of 25 c. Eventually all cartilage replaced by bone. d. Most of the skeleton is formed this way e. Ex: long bones of the limbs 28  Begins with Bone collar forms. Cartilage replaced Diaphysis grows, hyaline cartilage Invasion of vessels. by bone in cavity enlarges. model Osteoblasts & medullary cavity osteoclasts arrive. 29  Secondary Continuous ossification centers ossification at in epiphyses secondary centers: Bone gets longer 30  Bone development in fetus 6 weeks 10 weeks 31 Endochondral Ossification Epiphyseal Cartilages and Lines 32  VII. Factors Regulating Bone Growth 1. Nutritional Requirements a. Calcium and Phosphate salts b. Vitamins A and C Healthy Osteoblasts c. Vitamin D Affects Calcium absorption & transport 33 2. Hormone regulation a. Parathyroid hormone: Stimulates osteoclasts & increases Ca absorption in G.I. system Parathyroid b. Calcitonin: Produced by thyroid. Inhibits gland osteoclasts Thyroid gland Trachea 34 c. Growth Hormone Produced in pituitary gland. Promotes osteoblast proliferation. d. Sex Hormones Estrogen and Testosterone Stimulate osteoblasts 35 Up next: Axial and Appendicular Muscles! Questions & comments: [email protected] 36