Bones and Skeletal Tissues PART 1 Bones and Skeletal Tissues

Location and basic structure Cartilage Location and basic structure Found throughout adult body Ear and epiglottis Articular cartilages and costal cartilage Larynx, trachea, and nose Intervertebral discs and pubic symphysis Where do you find each type of cartilage? Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Is surrounded by perichondrium Consists primarily of water Cartilage Is abundant in embryo Is surrounded by perichondrium Consists primarily of water Resilient tissue – springs back to original shape Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Types of Cartilage – Covered in CH 4 Hyaline cartilage – (glassy) Most abundant cartilage Provides support through flexibility Elastic cartilage – contains many elastic fibers Able to tolerate repeated bending Fibrocartilage – resists strong compression and strong tension An intermediate between hyaline and elastic cartilage Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Cartilages in the Adult Body Figure 6.1 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Growth of Cartilage Appositional growth Interstitial growth Chondroblasts in surrounding perichondrium produce new cartilage Interstitial growth Chondrocytes within cartilage divide and secrete new matrix Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Bones contain several types of tissues Tissues in Bone Bones contain several types of tissues Dominated by bone CT Contain nervous tissue and Blood CT Contain cartilage in articular cartilages Contain ET lining blood vessels Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Support – provides hard framework Function of Bones Support – provides hard framework Movement – skeletal muscles use bones as levers Protection of underlying organs Mineral storage – reservoir for important minerals Blood-cell formation – bone contains red marrow Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Classification of Bones Long bones – longer than wide – a shaft plus ends Short bones – roughly cube-shaped Flat bones – thin and flattened, usually curved Irregular bones – various shapes, do not fit into other categories Give an example of each type of bone Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Classification of Bones Figure 6.2 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Compact bone – dense outer layer of bone Gross Anatomy of Bones Compact bone – dense outer layer of bone Spongy (cancellous) bone – internal network of bone Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Structure of a Typical Long Bone Diaphysis – “shaft” of a bone Epiphysis – ends of a bone Blood vessels – well vascularized Medullary cavity – hollow cavity filled with yellow marrow Membranes Periosteum, perforating fibers (Sharpey’s fibers), and endosteum Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Structure of a Long Bone Figure 6.3a–c Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Structure of Short, Irregular, and Flat Bones Flat bones, short bones, and irregular bones Contain bone marrow but no marrow cavity Diploë Internal spongy bone of flat bones Figure 6.4 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Gross Anatomy of Bones Bone design and stress Anatomy of a bone reflects stresses Compression and tension greatest at external surfaces Figure 6.5a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Superficial surfaces of bones reflect stresses on them Bone Markings Superficial surfaces of bones reflect stresses on them There are three broad categories of bone markings Projections for muscle attachment Surfaces that form joints Depressions and openings Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Bone Markings Table 6.1 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Microscopic Structure of Compact Bones Figure 6.6 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Bones and Skeletal Tissues PART 2 Bones and Skeletal Tissues

Chemical Composition of Bone 35% organic components Composed of cells, fibers, and organic substances Collagen – abundant 65% inorganic mineral salts Primarily calcium phosphate Resists compression Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Ossification (osteogenesis) – bone-tissue formation Bone Development Ossification (osteogenesis) – bone-tissue formation Membrane bones – formed directly from mesenchyme Intramembranous ossification Other bones – develop initially from hyaline cartilage Endochondral ossification Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Intramembranous Ossification Figure 6.9, steps 1–2 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Intramembranous Ossification Figure 6.9, steps 3–4 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Endochondral Ossification All bones except some bones of the skull and clavicles Bones are modeled in hyaline cartilage Begins forming late in the second month of embryonic development Continues forming until early adulthood Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Stages in Endochondral Ossification Figure 6.10 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Anatomy of Epiphyseal Growth Areas In epiphyseal plates of growing bones Cartilage is organized for quick, efficient growth Cartilage cells form tall stacks Chondroblasts at the top of stacks divide quickly Pushes the epiphysis away from the diaphysis Lengthens entire long bone Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Anatomy of Epiphyseal Growth Areas Older chondrocytes signal surrounding matrix to calcify Older chondrocytes then die and disintegrate Leaves long trabeculae (spicules) of calcified cartilage on diaphysis side Trabeculae are partly eroded by osteoclasts Osteoblasts then cover trabeculae with bone tissue Trabeculae finally eaten away from their tips by osteoclasts Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Organization of Cartilage within Epiphyseal Plate of Growing Long Bone Figure 6.11 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Postnatal Growth of Endochondral Bones During childhood and adolescence Bones lengthen entirely by growth of the epiphyseal plates Cartilage is replaced with bone CT as quickly as it grows Epiphyseal plate maintains constant thickness Whole bone lengthens Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Hormonal Regulation of Bone Growth Growth hormone – produced by the pituitary gland Stimulates epiphyseal plates Thyroid hormone – ensures that the skeleton retains proper proportions Sex hormones (estrogen and testosterone) Promote bone growth Later induces closure of epiphyseal plates Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Postnatal Growth of Endochondral Bones As adolescence draws to an end Chondroblasts divide less often Epiphyseal plates become thinner Cartilage stops growing Replaced by bone tissue Long bones stop lengthening when diaphysis and epiphysis fuse Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Bone is dynamic living tissue Bone Remodeling Bone is dynamic living tissue 500 mg of calcium may enter or leave the adult skeleton each day Cancellous bone of the skeleton is replaced every 3 – 4 years Compact bone is replaced every 10 years Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Postnatal Growth of Endochondral Bones Growing bones widen as they lengthen Osteoblasts – add bone tissue to the external surface of the diaphysis Osteoclasts – remove bone from the internal surface of the diaphysis Appositional growth – growth of a bone by addition of bone tissue to its surface Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Bone deposit and removal Bone remodeling Occurs at periosteal and endosteal surfaces Bone remodeling Bone deposition – accomplished by osteoblasts Bone reabsorption – accomplished by osteoclasts Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Remodeling, Spongy Bone Figure 6.12 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Osteoclast – A Bone-Degrading Cell A giant cell with many nuclei Crawls along bone surfaces Breaks down bone tissue Secretes concentrated HCl Lysosomal enzymes are released Figure 6.13a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Repair of Bone Fractures Simple and compound fractures Treatment by reduction Closed reduction Open reduction Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Stages of Healing a Fracture Figure 6.14 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Common Types of Fractures Table 6.2 (1 of 3) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Common Types of Fractures Table 6.2 (2 of 3) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Common Types of Fractures Table 6.2 (3 of 3) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Disorders of Bones Osteoporosis Characterized by low bone mass Bone reabsorption outpaces bone deposition Occurs most often in women after menopause Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Osteoporosis Figure 6.15 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Disorders of Bones Osteomalacia Rickets Occurs in adults – bones are inadequately mineralized Rickets Occurs in children – analogous to osteomalacia Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

Disorders of Bones Paget’s disease Osteosarcoma Characterized by excessive rate of bone deposition Osteosarcoma A form of bone cancer Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Skeleton Throughout Life Cartilage grows quickly in youth Skeleton shows fewer chondrocytes in the elderly Bones are a timetable Mesoderm Gives rise to embryonic mesenchyme cells Mesenchyme Produces membranes and cartilage Membranes and cartilage ossify Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings

The Skeleton Throughout Life Skeleton grows until the age of 18–21 years In children and adolescents Bone formation exceeds rate of bone reabsorption In young adults Bone formation and bone reabsorption are in balance In old age reabsorption predominates Bone mass declines with age Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings