1. Copyright © 2010 Pearson Education, Inc. Chapter 6 Bones And Skeletal Tissues Shilla Chakrabarty, Ph.D.

2. Copyright © 2010 Pearson Education, Inc. Introduction Bones and cartilages form our internal skeleton The human skeleton is initially made up of cartilages and fibrous membranes Most of these early supports are soon replaced by bones

3. Copyright © 2010 Pearson Education, Inc. Skeletal Cartilages Made up of cartilage tissue, which primarily consists of water Contain no blood vessels or nerves Surrounded by dense irregular connective tissue, the perichondrium Perichondrium contains blood vessels for nutrient delivery to cartilage Perichondrium serves as a girdle to resist outward expansion when cartilage is compressed Three types of cartilage tissue in the body: hyaline, elastic and fibrocartilage All types of cartilage have the same basic components: Chondrocytes encased in small cavities or lacunae Extracellular matrix containing a jelly-like ground substance, and fibers

4. Copyright © 2010 Pearson Education, Inc. Skeletal Cartilages 1.Hyaline cartilages: Translucent or glass-like in appearance Provide support, flexibility, and resilience Most abundant type: include articular cartilages, costal cartilages, respiratory cartilages, nasal cartilages 2.Elastic cartilages Similar to hyaline cartilages, but contain elastic fibers and therefore can withstand repeated bending Found only in the external ear and the epiglottis 3.Fibrocartilages Consist of roughly parallel rows of chondrocytes, alternating with thick collagen fibers Highly compressible—have great tensile strength Occur in areas subjected to heavy pressure and stretch, such as intervertebral discs and pad-like cartilages (menisci) of the knee

5. Copyright © 2010 Pearson Education, Inc. Figure 6.1 Axial skeleton Appendicular skeleton Hyaline cartilages Elastic cartilages Fibrocartilages Cartilages Bones of skeleton Epiglottis Larynx Trachea Cricoid cartilage Lung Respiratory tube cartilages in neck and thorax Thyroid cartilage Cartilage in external ear Cartilages in nose Articular Cartilage of a joint Costal cartilage Cartilage in Intervertebral disc Pubic symphysis Articular cartilage of a joint Meniscus (padlike cartilage in knee joint) Distribution Of Cartilage Tissues In The Body

6. Copyright © 2010 Pearson Education, Inc. Growth of Cartilage  Unlike bone, cartilage has a flexible matrix that can accommodate mitosis  Cartilage growth occurs in two ways:  Appositional Chondrocytes in surrounding perichondrium secrete new matrix against the external face of existing cartilage  Interstitial Lacunae-bound chondrocytes divide and secrete new matrix, expanding cartilage from within NOTE: Typically, cartilage growth ends during adolescence, when the skeleton stops growing  Calcification (deposition of calcium salts in the matrix of cartilage, causing it to harden) occurs during Normal bone growth in youth Old age

7. Copyright © 2010 Pearson Education, Inc. Bones of the Skeleton Two main groups, by location  Axial skeleton Forms the long axis of the body Includes the bones of the skull, vertebral column and rib cage Most involved in protecting, supporting or carrying other body parts  Appendicular skeleton Consists of the upper and lower limbs and the girdles that attach the limbs to the axial skeleton

8. Copyright © 2010 Pearson Education, Inc. Axial skeleton Appendicular skeleton Hyaline cartilages Elastic cartilages Fibrocartilages Cartilages Bones of skeleton Figure 6.1 Epiglottis Larynx Trachea Cricoid cartilage Lung Respiratory tube cartilages in neck and thorax Thyroid cartilage Cartilage in external ear Cartilages in nose Articular Cartilage of a joint Costal cartilage Cartilage in Intervertebral disc Pubic symphysis Articular cartilage of a joint Meniscus (padlike cartilage in knee joint) Axial And Appendicular Skeleton

9. Copyright © 2010 Pearson Education, Inc. Classification of Bones by Shape Long bones  Longer than they are wide (all limb bones, except patella, wrist and ankle bones)  Has a shaft plus two ends Short bones  Cube-shaped bones (in wrist and ankle)  Sesmoid bones are shaped like a sesame seed (formed within tendons, e.g., patella)

10. Copyright © 2010 Pearson Education, Inc. Classification of Bones by Shape Flat bones  Thin, flat, slightly curved  Includes the sternum, scapula, ribs and most skull bones Irregular bones  Complicated shapes  Examples Vertebrae and hip bones, sphenoid and ethmoid bones

11. Copyright © 2010 Pearson Education, Inc. Figure 6.2 Distribution of Bones In The Human Body

12. Copyright © 2010 Pearson Education, Inc. Functions of Bones 1.Support Provides a framework for supporting the body and soft organs.  Bones of lower limbs act as pillars to support the body when standing  The rib case supports the thoracic vault 2.Protection Fused bones of skull protect the brain Vertebrae surround the spinal cord, and Rib cage helps protect vital organs of the thorax 3.Movement Levers for muscle action to facilitate movement of body and its parts.

13. Copyright © 2010 Pearson Education, Inc. Functions of Bones 4. Mineral and Growth Factor Storage Reservoir for minerals (calcium and phosphorus) and growth factors 5. Blood cell formation (hematopoiesis) Occurs in marrow cavities 6. Triglyceride (energy) storage in bone cavities Fat is stored in bone cavities and is a source of stored energy for the body.

14. Copyright © 2010 Pearson Education, Inc. Bone Markings External surfaces of bones are rarely smooth and featureless Bulges, depressions, and holes on external surface serve as  Sites of attachment for muscles, ligaments, and tendons  Joint surfaces  Conduits for blood vessels and nerves Bone markings are named in different ways.

15. Copyright © 2010 Pearson Education, Inc. The Major Surface Features Of Bones

16. Copyright © 2010 Pearson Education, Inc. Bone Markings: Projections Usually indicate stresses created by muscles attached to and pulling on them, or are modified surfaces where bones meet and form joints Sites of muscle and ligament attachment Tuberosity—rounded projection Crest—narrow, prominent ridge Trochanter—large, blunt, irregular surface Line—narrow ridge of bone Tubercle—small rounded projection Epicondyle—raised area above a condyle Spine—sharp, slender projection Process—any bony prominence

17. Copyright © 2010 Pearson Education, Inc. Table 6.1

18. Copyright © 2010 Pearson Education, Inc. Bone Markings: Projections Projections that help to form joints Head: Bony expansion carried on a narrow neck Facet: Smooth, nearly flat articular surface Condyle: Rounded articular projection Ramus: Arm-like bar

19. Copyright © 2010 Pearson Education, Inc. Bone Markings: Depressions and Openings Depressions and openings usually serve to allow passage of nerves and blood vessels. Meatus: Canal-like passageway Sinus: Cavity within a bone Fossa: Shallow, basin-like depression Groove: Furrow Fissure: Narrow, slit-like opening Foramen: Round or oval opening through a bone

20. Copyright © 2010 Pearson Education, Inc. Table 6.1

21. Copyright © 2010 Pearson Education, Inc. Bone Textures Compact bone: Dense outer layer Spongy (cancellous) bone: Honeycomb of trabeculae Compact bone

22. Copyright © 2010 Pearson Education, Inc. Proximal epiphysis (b) (a) Epiphyseal line Articular cartilage Periosteum Spongy bone Compact bone Medullary cavity (lined by endosteum) Compact bone Diaphysis Distal epiphysis Diaphysis (shaft) Compact bone collar surrounds medullary (marrow) cavity Medullary cavity in adults contains fat (yellow marrow) Epiphyses Expanded ends Spongy bone interior Epiphyseal line (remnant of epiphyseal growth plate that lengthens the bone during childhood) occurs between the diaphysis and epiphysis of adult bone NOTE: The region where the epiphysis and diaphysis meet is sometimes called the metaphysis Articular (hyaline) cartilage on joint surfaces Structure Of A Long Bone

23. Copyright © 2010 Pearson Education, Inc. Membranes of Bone Periosteum Outer fibrous layer of dense irregular connective tissue Inner osteogenic layer consists of Osteoblasts Osteoblasts (bone-forming cells) secrete bone matrix Osteoclasts (bone-breaking cells) destroy bone Osteogenic cells (stem cells) give rise to osteoblasts Rich supply of nerve fibers, nutrient blood vessels, and lymphatic vessels enter the bone via nutrient foramina Secured to underlying bone by perforating Sharpey’s fibers which are tufts of collagenous fibers that extend from the fibrous layer into bone matrix

24. Copyright © 2010 Pearson Education, Inc. Yellow bone marrow Endosteum Compact bone Periosteum Perforating (Sharpey’s) fibers Nutrient arteries Membranes of Bone Endosteum Delicate connective tissue membrane on internal surfaces of bone Covers trabeculae of spongy bone and lines canals that pass through compact bone Also contains osteoblasts and osteoclasts

25. Copyright © 2010 Pearson Education, Inc. Compact bone Trabeculae Spongy bone (diploë) Thin plates of periosteum-covered compact bone on the outside and endosteum-covered spongy bone within No diaphysis (shaft) or epiphysis Contain bone marrow between trabeculae, but no significant marrow cavity Spongy bone called diploë in flat bones Structure of Short, Irregular, and Flat Bones

26. Copyright © 2010 Pearson Education, Inc. Location of Hematopoietic Tissue In Bones In adults, hematopoietic tissue or red marrow are found in  Trabecular cavities of spongy bones heads of the femur and humerus NOTE: In most adult long bones, the fat-containing yellow marrow in the medullary cavity extends well into the epiphysis. Thus blood cell production in adult long bones routinely occurs only in heads of the femur and humerus. Yellow marrow can revert to red marrow under dire conditions.  Trabecular cavities of the diploë of flat bones NOTE: Red marrow in diploë of flat bones such as the sternum and irregular bones such as the hip bone are more active in hematopoiesis, and are routine sites for obtaining red marrow samples In newborn infants, red marrow is found in  Medullary cavities of the diaphysis and all spaces in spongy bone

27. Copyright © 2010 Pearson Education, Inc. Microscopic Anatomy of Bone Four major cell types in bones are: 1.Osteogenic (osteoprogenitor) cells: Mitotically active stem cells in membranous periosteum and endosteum 2.Osteoblasts: Bone-forming cells 3.Osteocytes: Mature bone cells trapped in lacunae 4.Osteoclasts: Bone-destroying cells break down (resorb) bone matrix

28. Copyright © 2010 Pearson Education, Inc. (a) Osteogenic cell(b) Osteoblast Stem cell Matrix-synthesizing cell responsible for bone growth (c) Osteocyte Mature bone cell that maintains the bone matrix (d) Osteoclast Bone-resorbing cell

29. Copyright © 2010 Pearson Education, Inc. Microscopic Anatomy of Bone: Compact Bone Structural unit is called the osteon or the Haversian system Each osteon is an elongated cylinder parallel to the long axis of the bone Functionally, osteons are tiny weight bearing pillars

30. Copyright © 2010 Pearson Education, Inc. Structures in the central canal Artery with capillaries Vein Nerve fiber Lamellae Collagen fibers run in different directions Twisting force An Osteon A group of weight-bearing hollow tubes of bone matrix, called lamella, one placed outside the next Collagen fibers in adjacent lamellae run in different directions to reinforce one another and resist twisting Central canal or Haversian canal containing small blood vessels and nerves runs through core of osteon NOTE: Not all lamellae in compact bone are part of osteons. Incomplete lamellae called interstitial lamellae are remnants of previous osteons cut through by bone remodeling. Circumferential lamellae extend around the entire circumference of the diaphysis

31. Copyright © 2010 Pearson Education, Inc. Microscopic Anatomy of Bone: Compact Bone Perforating (Volkmann’s) canals:  Run at right angles to the central canal  Connect blood vessels and nerves of the periosteum and central canal Lacunae: Small cavities in which osteocytes are trapped as bone matrix hardens Canaliculi—hair-like canals filled with tissue fluid and containing extensions of osteocytes connect all osteocytes in an osteon for food and waste exchange

32. Copyright © 2010 Pearson Education, Inc. Endosteum lining bony canals and covering trabeculae Perforating (Volkmann’s) canal Perforating (Sharpey’s) fibers Periosteal blood vessel Periosteum Lacuna (with osteocyte) (a) (b)(c) Lacunae Lamellae Nerve Vein Artery Canaliculi Osteocyte in a lacuna Circumferential lamellae Osteon (Haversian system) Central (Haversian) canal Central canal Interstitial lamellae Lamellae Compact bone Spongy bone Microscopic Anatomy Of Compact Bone

33. Copyright © 2010 Pearson Education, Inc. Microscopic Anatomy of Bone: Spongy Bone Apparently poorly organized, but help resist stress Contain trabeculae Trabeculae Are tiny bony struts or spicules Align along lines of stress for stress resistance Are only a few cells thick Lack osteons: contain irregularly arranged lamellae and osteocytes, connected by canaliculi Capillaries in endosteum supply nutrients to osteocytes through diffusion

34. Copyright © 2010 Pearson Education, Inc. Chemical Composition of Bone Organic Components Osteogenic cells, osteoblasts, osteocytes, osteoclasts Osteoid—organic bone matrix secreted by osteoblasts Ground substance (proteoglycans, glycoproteins) Collagen fibers: provide tensile strength and flexibility Inorganic Components Hydroxyapatites (mineral salts) Form 65% of bone mass Mainly calcium phosphate crystals Responsible for hardness and resistance to compression