Bone, cartilage, tendons, and ligaments of the skeletal system are all connective tissues.
The matrix always contains collagen, ground substance, and other organic molecules, as well as water and minerals.
Collagen
is a fibrous protein that provides flexibility but resists pulling or compression.
Matrix ground substance contains proteoglycans which are water trapping proteins that help cartilage to be smooth and resilient.
Bone Matrix
is about 35% organic and 65% inorganic material by weight. The organic material is primarily collagen and proteoglycans.
hydroxyapatite
the inorganic material in bone matrix
Collagen fibers lend flexible strength to the bone
The mineral component gives bone compression (weight bearing) strength.
Osteoblasts
are responsible for the formation of bone and the repair and remodeling of bone.
What do osteoblasts produce?
collagen and proteoglycans
Ossification
formation of new bone by osteoblasts
Osteocytes
are cells that maintain bone matrix and form from osteoblast after bone matrix has surrounded it.
Osteocytes account for 90–95% of bone cells and are very long-lived
Lacunae
Osteocyte cell bodies are housed within the bone matrix
Canaliculi
Their cell extensions are housed in narrow, long spaces
Osteoclasts
bone-destroying cells
Reabsorption (Osteoclasts)
contribute to bone repair and remodeling by removing existing bone
Bone breakdown is important for mobilizing crucial Ca2+. As bone is broken down, the Ca2+ goes into the blood.
Lamellar Bone
Mature bone
Lamellae
organized lamellar bone into thin, concentric sheets or layers
Spongy bone consists of interconnecting rods or plates of bone called trabeculae
Spaces in trabeculae are filled with bonemarrow and blood vessels
Compact bone
cortical bone, is the solid, outer layer surrounding each bone
The functional unit of compact bone is an osteon. It is composed of concentric rings of matrix surrounding a central canal
Canaliculi
connect osteocytes to one another, transport nutrients and remove waste
Lamellae
are concentric rings of bone matrix which surround the central canal
Diaphysis
the center portion of the bone
Medullary cavity
hollow center of the long bone
Epiphyses
contain mostly spongy bone, with an outer layer of compact bone; ends of a long bone
Articularcartilage
end of a long bone is covered with hyaline cartilage
Epiphyseal plate is located between the epiphysis and the diaphysis. Growth in bone length occurs at the epiphyseal plate.
Epiphysealline
When bone stops growing in length, the epiphyseal plate becomes ossified
Bone Marrow
Cavities in spongy bone and the medullary cavity in the diaphysis are filled with soft tissue
Red Marrow
is the location of blood forming cells
Yellow marrow is mostly fat
The outer surface of a bone is covered by a connective tissue membrane called periosteum
The endosteum is a single cell layer of connective tissue that lines the internal surfaces of all cavities within bones; includes osteoblasts and osteoclasts
Intramembranous ossification
starts within embryonic connective tissue membranes; occurs when osteoblasts begin to produce bone within connective tissue; occurs primarily in the bones of the skull;