Unit 3 Chapter 6: Bones and Bone Tissue

This unit will include the skeletal system and articulations.

What is the Skeletal system?

It is bones, joints, and supporting tissues

What are the bones main organs?

• Osseous tissue

• Dense regular and irregular CT, plus bone marrow

What are the functions of the Skeletal System?

1) Protection: Protects vital organs such as the brain

2) Mineral storage and acid-base homeostasis: Bones stores minerals such as Ca² and PO4³, which are necessary for electrolyte and acid balance.

3) Blood cell formation: red bone marrow involved in formation of blood cells (hematopoiesis or hemopoiesis)

4) Fat storage: in yellow bone marrow of medullary cavity

5) Movement: bones are sites for skeletal muscle attachment

6) Support: supports weight weight and provides structural framework

What is the bone structure classification?

1) Long bones:

• longer than they are wide

• Include most bones in arms and legs (falanges also count as long bones)

2) Short bones:

• roughly cube-shaped

• include carpals and tarsals

3) Flat bones:

• thin and broad bones

• Ribs, pelvis, sternum and flat bones in skull

4) Irregular bones:

• include vertebrae and certain skull bones

5) Sesamoid bones:

• Located within tendons

• Patella (kneecap)

What is the structure of long bone?

• Periosteum: membrane surrounds outer surface (it is like a wrapping around the bone)

• Perforating fibers (sharpey’s fibers): anchors periosteum firmly to bone surface

• Diaphysis: shaft of a long bone (long portion of the bone)

• Epiphysis: end of long bone (proximal & distal)

• Articular Cartilage: Hyaline cartilage

• Marrow Cavity: contains bone marrow (red or yellow)

• Endosteum: thin membrane lining marrow cavity

Characteristics of Compact bone and Spongy bone (Cancellous bone)

• Compact bone:

- Hard, dense outer region

- Allows bone to resist stresses (compression & twisting)

• Spongy bone:

- Found inside cortical bone

- Honeycomb-like framework of bony struts;

- Resist forces from many directions

What are the Epiphyseal lines?

• Separates proximal and distal epiphysis from diaphysis

• Remnants of epiphyseal plates

(The lines are fully grown in adults)

What are the Epiphyseal plates? (growth plates)

• Hyaline cartilage found in developing bones of children

(If there is plates, it means the person still growing; children’s)

What is the structure of short, flat, irregular, and sesamoid bones?

• Covered by periosteum

• Diploë- two outer layers of thin compact bone with middle layer of spongy bone

• Sinuses- air filled spaces reduce bone weight

What is the extracellular matrix of bone and what it’s composed of?

• Inorganic matrix (65%) (Comes from outside)

-Consisting of minerals (hydroxyapatite salts of Ca & P)

• Organic matrix (35%) (Cells)

- Osteoid

- Consist of collagen fibers and usual ECM

Break down the word Osteocyte

Osteo = Bone

Cyte = Cells

What are the bone cells and a brief explanation

• Osteogenic- differentiate into osteoblasts

• Osteoblasts- Bone deposition

• Osteocytes- Mature bone cells in lacunae

• Osteoclasts- Bone resorption, secrete acid and enzymes

What is the structure of compact bone?

Osteon is the functional unit of bone

• Lamellae = concentric rings of thin layers of bone

• Centra Canal- Contains blood vessles &nerves