bones and the skeleton

osteoblasts

derive from bone lining cells, form bone matrix

osteocytes

• where

• what do they derive from

• what do they connect to and how

• what allows molecules through

• what does it regulate

• in body of the bone

• derive from osteoblasts

• connect with neighbouring osteocytes and bone lining cells by proceses in canaliculi

• gap junction allow molecules through

• regulate bone modelling

osteoclasts

• what kind of cells

• where do they derive from

• function

• large multinucleated cells

• from precursor cells in blood

• resorbs bone

osteogenic cell

• what kind of cell

• where are they located

• stem cell

• located in bone marrow/periosteal membrane

features of the long bone

• epiphysis at each end joining neighbouring bones

• articular cartilage is smooth at both ends and reduces friction

• trabecular bone is highly porous and has a high surface area

• diaphysis is middle

• medullary cavity is hollow and contains bone marrw

• endosteum is the membrane lining the inner surface

• periosteum is membrane lining the outer surface

• metaphysis is region between epiphysis and diaphysis

• some bones are capped with a layer of synovial cartilage, designed to carry loads and bending moments over long distances

flat bones

• structure

• function

• features

• examples

• 2 thin layers of compact bone separated by cancellous bone

• protection/ base of origin for extensor muscles

• no medullary cavity

• eg ribs, scapula, os coxae

short bone

• structure

• what is it filled with

• function

• roughly same size in all direction

• thin cortices

• completely filled with cancellous bone

• no medullary cavity

• designed to carry compressive loads over short distances

• not much bending

• eg bones of the carpus and the tarsus

sesamoid bones

• eg patellar

• alter direction of tendons

• give leverage to tendons

• prevent excessive tendon wear

periosteum

• 2 layers what are they

• what is it comprised of

• layer of cells on outside

• outer fibrous layer and inner cambium (osteogenic) layer

• fibrous layer contains fibroblasts, cambium layer contains osteoprogenitor cells

• blood vessels, sensory nerves, lymphatic vessels

endosteum

• what does it line

• features

• what is it composed of

• lines the inner surface of bones, eg medullary cavity

• osteogenic and osteolytic

• primarily composed of a single layer of bone lining cells and osteoblasts

what is the shape of the elastic fibres in the epiglottis, and how does this relate to function?

• mainly irregular

• dense network of branching fibres around chondrocytes

• less dense towards perichondrium

• allows return to normal shape after distortion

what is the annulus fibrosus

highly organized, fiber-reinforced, layered fibrocartilage that constitutes a critical component of the intervertebral disc in the spine

type i collagen

what is a slipped disk?

displacement of the nucleus pulposus

osteoprogenitor cells

cells which develop into osteoblast

from where are osteoclasts derived from

monocytes

how are canaliculi formed

contain cytoplasmic processes of the osteocytes, connected by gap junction

what are volkmanns canals

transverse links between the haversian canals

lamellar bone

• arrangement

• production

• regular cocentric arrangement

• strong

• slow production during growth/remodelling

woven bone

• irregular

• weak

• small trabeculae

• produced rapidly eg in fracture healing, intramembranous/endochondral ossification)

what are osteons

• shape

• what is in the centre and what does it contain

• what is this surrounded by

• what is it more resistant to

• functional unit of a bone

• long cylindrical structure with a central osteonal (Haversian) canal containing nerves, blood vessels and osteogenic cells

• central canal is surrounded by dense cocentric lamellae of bone

• there can be primary and secondary

• collagen ribres run in different directions in neihbouring lamellae

• more resistant to twisting force

• still allows give

surface markers

• leverage

• muscle attachment

• respons to strain within bone

• articulation with other bones

moment arms

• large moment arms make it possible to lift large loads with smaller forces

• but

• large moment arms means less absolute movement for a given force applied