28.4 - 28.9 Flashcards
___ are cells of cartilage. ___ cartilage is the most common type of cartilage. It consists of connective tissue cells in ECM. ECM is mainly composed of type ___ collagen, aggrecans, ___ acid, and chondronectin. It is incompressible and smooth.
Chondrocytes
Hyaline
Type 2 collagen
Hyaluronic acid
Elastic cartilage is ___ cartilage with the addition of ___. It is very flexible and maintains shapes e.g. in ears, ear canals, epiglottis, larynx.
Hyaline cartilage with elastin
___ is a mixture of fibrous/dense connective tissue and some cartilage. It binds solid joints and forms menisci and IVDs. There is no ___ (surface connective tissue layer) and is composed of type ___ collagen.
Fibrocartilage
No perichondrium (surface connective tissue layer found in hyaline and elastic cartilage)
Type 1 collagen
The IVD is composed of an external ring of ___ called the annulus fibrosus. The internal core is called the ___ ___ and is derived from the notochord. The gelatinous core is composed of collagen type ___. By the age of 20, all collagen type ___ is converted to ___.
Fibrocartilage Nucleus pulposus Collagen type 2 Collagen type 2 Fibrocartilage
Bone is hollow and composed of 2 types: ___ bone that forms a dense, outer layer, and ___ or ___ bone that forms a spongy interior.
Compact bone
Cancellous or trabecular bone
Blood vessels in the medullary cavities of bone are called ___ - large diameter, open vessels with pores in walls for cells from bone marrow to enter circulation.
Sinusoids
The thin layer of fibrous connective tissue on the inside of bone is called ___, and on the outside is called ___.
Inside - endosteum
Outside - periosteum
Type ___ collagen fibres of tendons penetrate into the surface of bone for strong attachment. The collagen fibres that penetrate the bone surface are called ___ ___. These are the basis for avulsion fractures.
Type 1 collagen fibres of tendons
Sharpey’s fibres
Long bones receive blood supply at 2 major points: in the ___ and in both ___. Nerves are associated with the blood vessels.
Diaphysis
Both epiphyses
Cartilage is avascular. Therefore, nutrients usually diffuse from the ___ (layer of connective tissue) to the cartilage. There are also ___ precursors in this layer. Repair of articular cartilage (in joints) is slow because there is no ___ (layer of connective tissue).
Nutrients diffuse from perichondrium to cartilage
Chondrocyte precursors
No perichondrium in joints
Synovial ___ lines the synovial space - this is NOT an ___, so there is no ___ ___, ___ junctions or desmosomes.
Synovial membrane
Not an epithelium
No basement membrane, tight junctions or desmosomes
Synovial fluid is an ___filtrate of synovial blood vessels and proteoglycans.
Ultrafiltrate
___ systems (i.e. ___) are oriented in lines of stress.
Haversian systems
Osteons
Osteoid (produced by ___) is composed of collagen type ___ and bone matrix proteins e.g. osteocalcin and osteonectin, proteoglycans and ___ phosphatase.
Osteoblasts
Collagen type 1 (c.f. type 2 in hyaline cartilage)
Alkaline phosphatase
In any long bone there is usually ___ centers of ossification.
3
One in diaphysis, one for each epiphysis
New bone (during development or repair) is called ___ bone - it is more cellular with more collagen and NO ___ systems. It is rapidly remodelled by osteoblasts and osteoclasts to ___ systems, called ___ bone.
Woven bone
No Haversian systems
Remodelled to Haversian systems
Lamellar bone
Remodelling of woven bone occurs when ___ form tunnels in bone and ___ ___ invade tunnels. ___ cells move down the walls of the tunnel to form ___ and produce new Haversian systems. They produce layers of bone in different orientations (approx. ___ degrees) from the outside in to form a smaller tunnel for the blood vessel in the tunnel.
Osteoclasts Blood vessels Osteoprogenitor Osteoblasts 90
Mechanotransduction occurs in ___, allowing direct remodelling to stresses.
Osteocytes
___ cells and resting ___ are found in the periosteum and endosteum.
Osteoprogenitor cells
Resting osteoblasts
Osteoid is composed of collagen type ___, whereas hyaline cartilage is composed of collagen type ___. In osteoid there are other proteins/proteoglycans and some GAGs, but there are ___ compared to cartilage.
Collagen type 1
Collagen type 2
Less in osteoid c.f. cartilage
There are some growth factors and cytokines in osteoid. Therefore, in resorption of bone by ___ there is release of growth factors for growth of bone by ___.
Osteoclasts
Osteoblasts
In histology of endochondral ossification, cartilage appears ___ due to GAGs and osteoid from osteoblasts, on the outside of the cartilage model appears ___.
Cartilage - basophilic due to GAGs
Osteoid - eosinophilic, on the surface/outside of cartilage model
Osteoblasts secrete collagen and secretory vesicles to increase the concentrations of ___ and ___ (note - osteoblasts do NOT directly secrete these, but secrete enzymes for precipitation of them) which precipitate into ___.
Calcium and phosphate
Hydroxyapatite
Normal bone turnover is ___-___% per year, but up to 200x faster in children.
5-10%/year
The functional unit of bone remodelling is called a ___ ___ ___, with osteoclasts in the front and osteoblasts in the back. The osteoclast resorbs a tunnel of bone and produces a new ___ ___ (or osteon). A capillary enters the tunnel and osteoblasts produce new bone. This new bone is “remodelled” bone, therefore it is ___ bone and NOT ___ bone.
Bone multicellular unit - osteoclast and osteoblast
Haversian system
Lamellar bone
NOT woven bone
Mineralisation of new osteoid depends on ___ and ___ in serum.
Calcium and phosphate
What are some factors that slow healing of fractures?
Age Comorbidities Medications Social factors Nutrition Fracture type Trauma Local factors e.g. infection
