6 Bones and Skeletal Tissues: Part A

Respiratory tube cartilages in neck and thorax Epiglottis Larynx Thyroid cartilage Cartilage in external ear Cartilages in nose Trachea Cricoid cartilage Lung Articular Cartilage of a joint Cartilage in Intervertebral disc Costal cartilage Respiratory tube cartilages in neck and thorax Pubic symphysis Bones of skeleton Axial skeleton Meniscus (padlike cartilage in knee joint) Appendicular skeleton Cartilages Articular cartilage of a joint Hyaline cartilage CT Elastic cartilage CT Fibrocartilage CT Figure 6.1

The skeleton is divided into two parts Axial: bones of the skull, vertebrae, ribs Appendicular: bones of the shoulders, hips, arms, legs

Calcification of cartilage As cartilage ages, calcium adds to the cartilage, making it more brittle Be careful when giving CPR to the elderly

Classification of Bones by Shape Long bones -Longer than they are wide Short bones -Cube-shaped bones Flat bones -Thin, flat, slightly curved Irregular bones -Complicated shapes

Figure 6.2

Functions of Bones 1. Protection For brain, spinal cord, and vital organs well, usually……..

Functions of bones 2. Support for the body shape

Functions of bones 3. Bones as levers for muscles to pull on, creating movement

Functions of Bones 4. Storage of minerals (calcium and phosphorus) and growth factors

Functions of bones 5. A place for blood cell formation (hematopoiesis) in marrow cavities

Functions of bones 6. Triglyceride (fat) storage in bone cavities

We will learn the bone markings in BONE LAB Table 6.1

Compact on the outside, spongy on the inside

Spongy bone inside a flat bone (diploë) Compact bone Why do we have compact bone on both outside and inside surface? Trabeculae Figure 6.5

Articular cartilage Compact bone Proximal epiphysis Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum) (b) Diaphysis Distal epiphysis (a) Figure 6.3a-b

Endosteum Yellow bone marrow Compact bone Periosteum Perforating (Sharpey’s) fibers Nutrient arteries (c) Figure 6.3c

Location of Hematopoietic (blood making) Tissue Newborn erythrocytes are made in red marrow in all marrow cavities and in spongy bone Adults erythrocytes are made in red marrow of: the heads of the femur and humerus inside flat bones of sternum and hips (*all other adult marrow is yellow) nerves and blood vessels vessels leave/enter the bone via nutrient foramina (holes)

Coverings of bone Periosteum Outer fibrous layer dense irregular CT (with collagen fibers) connects muscle and bone Inner osteogenic layer contains cells -Osteogenic cells (stem cells that divide to become osteoblasts) -Osteoblasts (bone-forming cells that make collagen) -Osteoclasts (bone-destroying cells that remodel bone) Remember! Osteocytes live WITHIN the BONE

Linings of bone Endosteum Delicate reticular CT lines the hollow part of the shaft and contains: -Osteogenic cells (stem cells that divide to become osteoblasts) -Osteoblasts (bone-forming cells that make collagen) -Osteoclasts (bone-destroying cells that remodel bone)

Osteoprogenitor cells divide and daughter cells are osteoblasts. Osteocytes Osteogenic cells Osteoblasts Change into Change into BONE CELLS Osteoprogenitor cells divide and daughter cells are osteoblasts. Osteoblasts produce collagen, to which minerals will attach. Osteocytes are mature bone cells which maintain the calcium balance in a bone Figure 6.4a-b

OsteoCLASTS are giant cells that digest bone with mild acids and enzymes during bone remodeling. They are related to white blood cells, not the other bone cells.

A BONE is made of smaller “pencil” shaped structures called osteons Compact bone Spongy bone A BONE is made of smaller “pencil” shaped structures called osteons Central canal Endosteum lining bony canals and covering trabeculae Osteon (a) Perforating fibers Lamellae Nerve Vein Artery Lamellae Central canal Canaliculi Lacuna (with osteocyte) Osteocyte in a lacuna Lacunae Interstitial lamellae (b) (c) Figure 6.7a-c

Osteons have many layers called lamella Artery with capillaries Structures in the central canal Vein Nerve fiber Lamellae Collagen fibers run in different directions Twisting force Figure 6.6

Osteocytes are connected by canaliculi (little canals) through which their “arms” pass nutrients to cells far from the blood in the central canal, and waste back. blood

Most cells in spongy bone are close enough to blood vessels in bone marrow to receive nutrition without the structure of osteons and canaliculi.

powered minerals water rebar Strong yet flexible All bone needs to be strong and flexible. How does it get that way? Strong yet flexible Calcium phosphate collagen water

FORMATION of soft organic bone matrix (osteoid) Osteoblasts secrete collagen into space around the cell Osteoblasts secrete proteoglycan gel Collagen fiber Proteoglycan and glycoprotein ground substance osteoblast

Inorganic salts arrive Calcium ions arrive in blood Collagen fiber Calcium ion

Bone matrix starts to harden Phosphate ions arrive in blood Phosphate Collagen fiber Calcium ion

Bone matrix is now hardened Hydroxyapatite forms, and matrix hardens into bone Phosphate Collagen fiber Calcium ion hydroxyapatite