1. Bones & The Skeleton
Lecture 1

2. Cartilage: Skeletal Cartilage
Made of some variety of cartilage tissue molded to fit it’s body and function
Cartilage is mostly water (which is why it’s resilient-it can spring back into shape)
There are three types:
Hyaline
Elastic
And Fibro Cartilage

3. Hyaline Cartilage: Look like frosted glass
Provide support with flexibility & resilience
Most abundant
Include:
Articular Cartilage: cover ends of most bones at moveable joint sites
Costal Cartilage: Connect ribs to Sternum
Respiratory Cartilage: form the voice box & reinforce passageways
Nasal Cartilage: support the external nose

4. Elastic Cartilage: Resemble Hyaline Cartilage but are more stretchy
Can stand up to repeated bending
Found in the ear & epiglottis

5. Fibrocartilage: Highly compressible with great tensile strength
Consist of parallel rows of chondrocytes and alternating with collagen fibers
Found in between the vertebrae, knee, & hip

6. Growth of Cartilage:
Cartilage has a flexible matrix which accommodates mitosis
Grows 2 ways
Appositional Growth: cartilage forming cells secrete a matrix against the existing cartilage tissue.
Growth from OUTSIDE
Interstitial Growth: Chondrocytes divide and secrete a new matrix , expanding the cartilage from within
Growth from INSIDE
Typically cartilage growth ends when the skeleton stops growing.
Cartilage and bone are two different tissues.

7. Functions Support: Provide a framework and cradles soft organs.
Protection: Protect the skull, Heart, and vertebrae.
Movement: Skeletal muscles attach to bone by tendons and bones act as levers to move the body.
Mineral Growth/Storage: Bone is a reservoir for minerals (calcium & phosphate). These can be released into the bloodstream as needed. It also sores growth factors.
Blood Cell Formation: Most blood cell formation (hematopoiesis) occurs in red marrow in certain bones.
Triglyceride (Fat) Storage: This energy source is stored in yellow marrow in certain bones.
Hormone Production: Bones produce Osteocalcin (helps to regulate bone formation & helps to protect against obesity or glucose intolerance).

8. Bone Classifications:
Axial Skeleton:
Forms the long axis of the body
Includes the skull, vertebral column, and rib cage
These bones protect, support, or carry other body parts.

9. Bone Classifications Appendicular Skeleton:
Bones of the upper and lower limbs, & girdles (shoulder bones and hip bones)
Help you move from place to place

10. Facts Bones come in many sizes and shapes
The unique shape of the bones fulfill a particular need
Ex. Femur withstands great pressure, and it’s hollow cylinder design provides maximum strength with minimum weight to accommodate our posture.

11. Classification Of Bones by Shape
Long:
Longer than they are wide
Have a shaft plus two ends that are usually expanded
All limb bones (except patella and wrist/ankle)
Elongated shape NOT overall size
Ex. finger bones=long bones
Short:
Roughly cube shaped
Bones of the wrist and ankle
Vary in number and size
Sesamoid bone: short bone that form in a tendon- they act to alter the direction of pull for that tendon

12. Classification Of Bones by Shape
Flat:
Thin flattened bones
Usually slightly curved
Sternum, Scapula, ribs, and most skull bones
Irregular:
Have complicated shapes
Vertebrae & Hip Bones

13. Bone Structure: Gross Anatomy
Bone Textures:
COMPACT BONE: A dense OUTER layer that looks smooth and solid
SPONGEY BONE: next layer after compact bones. A matrix of small bone which are normally filled

14. Structure of Short, Irregular, & Flat Bones
All of these bones consist thin plates of spongy bone covered by compact bone
The plates are covered by connective tissue membranes
They contain marrow but have no marrow cavity

15. Structure of Typical Long Bones:
Usually have: a shaft, bone ends, and membranes
Diaphysis (shaft):
Forms the long axis of the bone
Has a thick collar of compact bone surrounding the medullary cavity (marrow cavity)
Epiphysis (bone ends):
Boarder than the shaft
Outer shell=compact bone, inside that=spongy bone
Thin layer of articular (hyaline) cartilage covers the joint surface of each end—this cushions the opposing bone end during movement.

16. Structure of Typical Long Bones:
Epiphysis (Bone ends):
In adults: between diaphysis & epiphysis is an epiphyseal line—remnant of the plate (this is where your plate grew when you were younger)
Membranes (Periosteum & Endosteum):
Covers the outside (external) surface of all but the joint surfaces
Outer layer= irregular connective tissue
Inner layer= osteogenic cells that give rise to all bone except bone-destroying cells
Supplied with nerve fibers and blood which pass through the shaft and enter the marrow cavities
Collagen fibers attach & secure the periosteum to the bone

17. Structure of Typical Long Bones:
Membranes
Endosteum (within the bone) covers the internal bone

18. Cells of bone Tissue:
Osteogenic Cells: active stem cells found in the membranes they can become osteoblasts or bone lining cells
Osteoblasts: actively mitotic cells. They secrete an un-mineralized bone matrix of bone protein and calcium binding proteins. They can also play a role in matrix calcification
Osteocytes: mature bone cells which monitor and maintain the bone matrix and act as stress sensors
Bone Lining Cells: maintain the matrix and are found on the surface of bone
Osteoclasts: located at bone reabsorption sites (breaking down)

19. Bone Formation Two Types:
1. Endochondral ossification: (endo=within, chondro=cartilage) a bone develops by replacing hyaline cartilage. The resulting bone is called a cartilage bone or endochondral bone.
2. Intramembranous Ossification: a bone develops from a fibrous membrane and the bone is called a membrane bone.

20. Endochondral Ossification

21. Intramembranous Ossification