Bones and Skeletal Tissues

1. Bones and Skeletal Tissues Unit 6

2. Bones and Cartilages of the Human Body Figure 6.1

3. Skeletal Cartilage • Contains no blood vessels or nerves • Surrounded by the perichondrium (dense irregular connective tissue) that resists outward expansion • Three types – hyaline, elastic, and fibrocartilage

4. Hyaline Cartilage • Provides support, flexibility, and resilience • Is the most abundant skeletal cartilage • Is present in these cartilages: • Articular – covers the ends of long bones • Costal – connects the ribs to the sternum • Respiratory – makes up the larynx and reinforces air passages • Nasal – supports the nose

5. Elastic Cartilage • Similar to hyaline cartilage but contains elastic fibers • Found in the external ear and the epiglottis

6. Fibrocartilage • Highly compressed with great tensile strength • Contains collagen fibers • Found in menisci of the knee and in intervertebral discs

7. Growth of Cartilage • Appositional – cells in the perichondrium secrete matrix against the external face of existing cartilage • Interstitial – lacunae-bound chondrocytes inside the cartilage divide and secrete new matrix, expanding the cartilage from within • Calcification of cartilage occurs • During normal bone growth • During old age

8. Appositional Growth

9. Interstitial Growth

10. Bones and Cartilages of the Human Body Figure 6.1

11. Classification of Bones • Axial skeleton – bones of the skull, vertebral column, and rib cage • Appendicular skeleton – bones of the upper and lower limbs, shoulder, and hip

14. These hips don’t lie…

15. Male and Female Cranium Differences Most important skull differences between men and women are indicated by the letter value on the figure to the left

16. Male and Female Cranium Differences • The man’s cranial mass is more blocky and massive compared to the females which more rounder and tapers at the top. • Temporal Ridge - runs along the outer side of the upper skull creating the square shaped of the upper head. More prominent in men than women. • A woman's supraorbital margin (the ridge above the eyes) is sharper while the males is rather round and dull. • The Zygomatic bone (cheekbone that lies under the lower eye ridge) is more pronounced on the male skull. • The Mandible (lower jaw) bone of a woman is more rounded, while the male's is squared. • Frontal bone – forehead structure terminates at the brow. The male forehead is lower and more slopping. • Men have a deeper cranial mass. • The supercilary arch is large and pronounced in the man. • A males gonion (most posterior inferior point on angle of mandible) is more flared out and sharply angled. • The teeth of men tend to be larger.

17. Classification of Bones: By Shape Long bones – longer than they are wide (e.g., humerus) Figure 6.2a

18. Classification of Bones: By Shape Short bones Cube-shaped bones of the wrist and ankle Bones that form within tendons (e.g., patella) Figure 6.2b

19. Classification of Bones: By Shape Flat bones – thin, flattened, and a bit curved (e.g., sternum, and most skull bones) Figure 6.2c

20. Classification of Bones: By Shape Irregular bones – bones with complicated shapes (e.g., vertebrae and hip bones) Figure 6.2d

21. Function of Bones • Support – form the framework that supports the body and cradles soft organs • Protection – provide a protective case for the brain, spinal cord, and vital organs • Movement – provide levers for muscles • Mineral storage – reservoir for minerals, especially calcium and phosphorus • Blood cell formation – hematopoiesis occurs within the marrow cavities of bones

22. Bone Markings • Bulges, depressions, and holes that serve as: • Sites of attachment for muscles, ligaments, and tendons • Joint surfaces • Conduits for blood vessels and nerves

23. Bone Markings: Projections – Sites of Muscle and Ligament Attachment • Tuberosity – rounded projection • Crest – narrow, prominent ridge of bone • Trochanter – large, blunt, irregular surface • Line – narrow ridge of bone

24. Bone Markings: Projections – Sites of Muscle and Ligament Attachment • Tubercle – small rounded projection • Epicondyle – raised area above a condyle • Spine – sharp, slender projection • Process – any bony prominence

25. 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 – armlike bar of bone

26. Bone Markings: Depressions and Openings • Meatus – canal-like passageway • Sinus – cavity within a bone • Fossa – shallow, basinlike depression • Groove – furrow • Fissure – narrow, slitlike opening • Foramen – round or oval opening through a bone

28. Example of Bone Markings

29. Gross Anatomy of Bones: Bone Textures • Compact bone – dense outer layer • Spongy bone – honeycomb of trabeculae filled with yellow bone marrow

30. Structure of Long Bone Figure 6.3

31. Bone Marrow • Yellow marrow • Fills the cavities of adult long bones • Is largely fat • Red marrow • Occurs in spongy bone of some bones • Produces blood cells

32. Structure of Long Bone • Long bones consist of a diaphysis and an epiphysis • Diaphysis • Tubular shaft that forms the axis of long bones • Composed of compact bone that surrounds the medullary cavity • Yellow bone marrow (fat) is contained in the medullary cavity

33. Structure of Long Bone • Epiphyses • Expanded ends of long bones • Exterior is compact bone, and the interior is spongy bone • Joint surface is covered with articular (hyaline) cartilage • Epiphyseal line separates the diaphysis from the epiphyses

34. Structure of Long Bone Figure 6.3

35. Bone Membranes • Periosteum – double-layered protective membrane • Outer fibrous layer is dense regular connective tissue • Inner osteogenic layer is composed of osteoblasts and osteoclasts • Richly supplied with nerve fibers, blood, and lymphatic vessels, which enter the bone via nutrient foramina • Secured to underlying bone by Sharpey’s fibers • Endosteum – delicate membrane covering internal surfaces of bone

36. Structure of Long Bone Figure 6.3

37. Structure of Short, Irregular, and Flat Bones • Thin plates of periosteum-covered compact bone on the outside with endosteum-covered spongy bone (diploë) on the inside • Have no diaphysis or epiphyses • Contain bone marrow between the trabeculae

38. Structure of a Flat Bone Figure 6.4

39. frontal bone sphenoid bone parietal bone ethmoid bone temporal bone lacrimal bone zygomatic bone maxilla occipital bone external auditory meatus mandible Skull and Facial Bones

40. Sinuses frontal sinus ethmoid sinus sphenoid sinus maxillary sinus

41. Location of Hematopoietic Tissue (Red Marrow) • In infants • Found in the medullary cavity and all areas of spongy bone • In adults • Found in the diploë of flat bones, and the head of the femur and humerus

42. Microscopic Structure of Bone: Compact Bone • Haversian system, or osteon – the structural unit of compact bone • Lamella – weight-bearing, column-like matrix tubes composed mainly of collagen • Haversian, or central canal – central channel containing blood vessels and nerves • Volkmann’s canals – channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversian canal

43. Microscopic Structure of Bone: Compact Bone • Osteocytes – mature bone cells • Lacunae – small cavities in bone that contain osteocytes • Canaliculi – hairlike canals that connect lacunae to each other and the central canal

44. Microscopic Structure: Compact Bone Figure 6.6a, b

45. Chemical Composition of Bone: Organic • Osteoblasts – bone-forming cells • Osteocytes – mature bone cells • Osteoclasts – large cells that resorb or break down bone matrix • Osteoid – unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen

46. Chemical Composition of Bone: Inorganic • Hydroxyapatites, or mineral salts • Sixty-five percent of bone by mass • Mainly calcium phosphates • Responsible for bone hardness and its resistance to compression Picture from: cheng.es.osaka-u.ac.jp