Bones & Skeletal system: Part 1

Cartilage

-Provides support, framework and attachments

-structural model for many developing bones

-Chondrocytes in Lacuna

-Abundant extracellular matrix, mostly collagen fibers, and gel-like ground substance:protein-polysaccharide(chondromucoprotein)

-surrounded by perichondrium (dense irregular connective tissue)

-Cartilage is avascular, nutrients provided by blood vessels in perichondrium

-Three types: Hyaline, Elastic, and fibrocartilage

Hyaline cartilage

-Flexibility, reduce friction, absorb shock

-Most abundant type of cartilage

-Weakest cartilage

-Very fine collagen fibers in extracellular matrix (glass like appearance)

-joints, respiratory system, nose, embryonic model for bone

Elastic cartilage

-Maintain shape of organs

-Threadlike network of elastic fibers within the matrix

-More flexible than hyaline

-External ear, larynx

Fibrocartilage

-Strength and rigidity, compression, torsion-strongest

-Bundles of collagen fibers in extracellular matrix

-Found in knee joint, pubic symphysis, intervertebral discs

Skeletal system

-Bones are the organs of the skeletal system

-Composed of many tissues: bone, cartilage, dense connective, blood, epithelial, nervous

-206 bones in human body, babies have more bones(unfused), some adults have more bones

-Each bone is an organ

Bone classification

-Long bone(humerus), long slender

-Sutural Bones, Between skull bones

-Short bone(wrist bone), small box-shaped

-Flat bone(sternum), thin, large surface area for attachments

-Irregular bone(vertebra), Complex shapes

-Sesamoid bone(patella), small, flat, sesame seed-like

Projections

where muscles, tendons, or ligaments attach, or where bones form joins

Openings and depressions

sites where blood vessels or nerves lie alongside or penetrate the bone

Diaphysis

Tubular shaft of the bone, consists of compact bones-dense and solid, a layer of protection around a medullary cavity-central space

Epiphysis

The end parts of the long bone, consists of spongy (trabecular) bone-opening network of struts and plates resembling a lattice

Metaphysis

The region between the diaphysis and epiphysis

Epiphyseal plate/line

area of linear growth/remnant from growth

Articular Cartilage

hyaline cartilage covering joints

Periosteum

membrane covering outside of bone

Outer fibrous layer

dense connective tissue

Inner cellular layer

Osteoprogenitor cells, fibroblasts-like cells that differentiate into osteoblasts

Endosteum

membrane covering inside of bone, trabeculae and central canal; thinner than periosteum, reticular fibers and osteoprogenitor cells

Sharpey’s fibers

Collagen fibers from the periosteum that penetrate the bone matrix for attachment, particularly at tendons and ligaments

Red marrow

Blood cell production

Yellow marrow

lipid storage

Flat bones

Thin layer of compact bone on the outside with a core of trabecular bone

Osteoprogenitor(osteogenic) cells

progenitor cells in membranes that give rise to osteoblasts as necessary

Osteoblasts

Bone builders, are non-mitotic, secrete osteoid (organic) matrix, the matrix binds calcium and other minerals from the blood

Osteocytes

mature osteoblasts that are entrapped in matrix, maintain the protein and mineral composition of the matrix

Osteoclasts

Multi-nucleated, derived from monocytes (macrophages)and break down or resorb matrix

Matrix of bone

1/3 collagen fibers and other proteins, strength comes from calcium phosphate to form hydroxyapatite

Osteons

cylinders of circular lamellae that run parallel to the long axis of the bone (direction of max force)

Nutrient vessels

supply blood to vessels in the medulla and nerves

Central(Haversian) canals

contain endosteum, nerves and blood vessels

Perforating (Volkmann’s) canals

connect blood supply from periosteum to central canal and medullary vessels, nerves as well

Location of osteocytes

In the lacunae between the lamellae, they have fine projections that connect osteocytes via small openings called canaliculi

Location of osteoblasts and osteoclasts

found in the endosteum or periosteum where they are either building or eroding bone

Spongy (cancellous, trabecular) bone

composed of trabeculae (not osteons)

covered by endosteum

forms the core of most bones

Spaced between trabeculae is filled with red marrow-the site of hemopoiesis (blood cell production)