1. Bones and Skeletal Tissues6
P A R T A
Bones and Skeletal Tissues

2. Intro to the Skeletal System

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. Provides support, flexibility, and resilience
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 larynx, 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. Calcification of cartilage occurs
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. Bones and Cartilages of the Human Body
Figure 6.1

9. Bones are Active Tissues
Each bone has several types of tissues – so each bone is an organ!
Nerves
Blood Vessles
Cartilage
Spongy bone
Compact bone
Most bones have both compact & spongy tissue.

10. Classification of Bones: by Region
Axial skeleton (forms an axis of rotation) – bones of the skull, vertebral column, and rib cage
Appendicular skeleton (appendages that are appended (i.e., added) on to the axial skeleton) – bones of the upper and lower limbs, shoulder, and hip
Articulation refers to bones connected to each other (bones articulate at joints)

11. Classification of Bones: By Shape (4 types)
1. Long bones – longer than they are wide (e.g., humerus, phalanges, etc.)
Figure 6.2a

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

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

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

15. 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 (storage and release)
Blood cell formation – hematopoiesis occurs within the marrow cavities of bones

16. Gross Anatomy of Bones: Bone Textures
Compact bone – dense outer layer
Spongy bone – honeycomb of trabeculae filled with red (sometimes yellow) bone marrow
Trabeculae are oriented to reduce forces across bones
Yellow marrow is mostly fat, fills the medullary cavity in the middle of long bones
Red marrow has hematopoiesis (blood cell formation)

17. Bulges, depressions, and holes that serve as:
Bone Markings
Bulges, depressions, and holes that serve as:
Joint surfaces (where bones meet – also known as articular surfaces)
Sites of attachment for muscles, ligaments, and tendons
Conduits for blood vessels and nerves

18. 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

19. 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
Tubercle – small rounded projection
Epicondyle – raised area above a condyle
Spine – sharp, slender projection
Process – any bony prominence

20. Bone Markings: Depressions and Openings
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

21. Bone Markings
Table 6.1

22. Bone Structure

23. 9 7 3 4 5 8 6 2 1 10 11 12
13 – Name this bone

24. 1 2 3 4 11 5 6 7 8 10 9

25. Structure of Long Bone
Long bones consist of a diaphysis (the shaft) and two epiphyses (the ends)
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

26. Structure of Long Bone Epiphyses
Expanded ends of long bones; oddly shaped to form joints and allow muscle attachments
Exterior is compact bone, and the interior is spongy bone – the random branches of spongy bone are called trabeculae
Joint surface is covered with articular cartilage (made of hyaline cartilage)
Epiphyseal line separates the diaphysis from the epiphyses – location where bone grows in length

27. Structure of Long Bone
Figure 6.3

28. Structure of Long Bone
Figure 6.3a

29. Structure of Long Bone
Figure 6.3b

30. Structure of Long Bone
Figure 6.3c

31. Periosteum – double-layered protective membrane
Bone Membranes
Periosteum – double-layered protective membrane
Outer fibrous layer is dense regular connective tissue
Inner osteogenic layer is composed of osteoblasts (cells that build bone) and osteoclasts (cells that break down bone)
Richly supplied with nerve fibers, blood vessels, and lymphatic vessels, which enter the bone via nutrient foramina
Secured to underlying bone by Sharpey’s fibers (aka, perforating fibers)

32. Bone Membranes
Endosteum – delicate membrane covering internal surfaces of bone
Same layers as periosteum: osteogenic layer next to bone, dense connective tissue next to marrow

33. Structure of Short, Irregular, and Flat Bones
“Sandwich Bone:” 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 red bone marrow between the trabeculae

34. Structure of a Flat Bone
Figure 6.4

35. 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 and irregular bones, and the head of the femur and humerus

36. Microscopic Structure of Bone

37. Four types of bone cells.
Osteogenic cells: conduct mitosis in the membranes of the endosteum and periosteum.
Stem cells that produce other bone cell types.
These cells respond to trauma by giving rise to osteoclasts and osteoblasts.
Osteoblasts: bone forming cells.
Secrete the bone matrix of collagen, calcium phosphate, and other materials (the matrix is the non-living material surrounding connective tissue cells).

38. Four types of bone cells.
Osteoclasts: bone destroying cells.
Giant macrophagic cells that move along a bone surface to break down the matrix using enzymes and hydrochloric acid.
Break down bone to release calcium needed for other functions in the body (nerve impulses, muscle contractions, etc.)
Osteocytes: spider-shaped, mature bone cells derived from osteoblasts.
Found in lacunae and connected by tentacle-like projections passing through canaliculi.
These cells maintain healthy bone tissue by secreting enzymes and influencing bone mineral content.
They also regulate calcium release into blood by signaling osteoclasts to break down bone matrix.

39. Microscopic Structure of Bone: Compact Bone
Figure 6.6b

40. Haversian system, or osteon – the structural unit of compact bone

41. Osteon Structure I
Lamellae: Like tree rings in 3-D - Several layers of collagen & CaPO4 – Weight-bearing, stress absorbers – Each lamellar layer has its collagen fibers wrapping in the same direction, but alternate layers wrap in opposite directions to resist twisting

42. Osteon Structure II
Haversian canal, aka osteonic or central canal – central channel running the length of the osteon containing blood vessels and nerves
Volkmann’s canals, aka perforating canals – channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversian canal
Lacunae – small cavities in bone that contain osteocytes
Canaliculi – hairlike canals that connect lacunae to each other and the central canal – provides nutrients to bone cells

43. Microscopic Structure of Bone: Compact Bone
Figure 6.6c

44. Microscopic Structure of Bone: Spongy Bone
No osteons
Random-looking projections called trabeculae – only a few cells thick – contain irregular lamellae with ostocytes inside lacunae – canalliculi connect osteocytes
Trabeculae resist stress on bone
Figure 6.6c

45. Microscopic Structure of Bone
Figure 6.6a, b

46. Microscopic Structure of Bone
Figure 6.6a

47. Chemical Composition of Bone
Bone chemistry can be divided into organic and inorganic components
Organic components include the cells described above (Osteocytes, Osteoblasts, Osteoclasts, and Osteogenic cells) and the Osteoid – unmineralized bone matrix composed of organic molecules including proteoglycans, glycoproteins, and collagen
Inorganic components include Hydroxyapatites, or mineral salts – these make up 65% of the bone’s mass and are mainly calcium phosphates – they are responsible for bone hardness and its resistance to compression