Flashcards in HISTOLOGY AND EMBRYOLOGY Deck (87)
1. Capable of enduring a great deal of stress
2. It has no blood vessels( avascular) and no nerves
3. The cartilage consists of cells and extracellular matrix (ECM) by perichondrium
4. Matrix cobsists of collagen and elastic fibers embedded in chondroitin sulfate
5. Strength is due to collagen fibers
6. Resilience is due to chondroitin sulfate
Perichondrium of hyaline cartilage (4)
1. Except in articularcartilage of joints, hyaline cartilage is covered by a layer of dense connective tissue called as perichondrium
2. Perichondrium is essentiak for growth and maintenance of cartilage
3. Perichondrium consists of type 1 collagen and fibroblasts
4. Among these fibroblasts, inenr layer of perichondrium are progenştır cells for chondroblasts
growth of cartilage
INTERSTITIAL GROWTH: Growth from chondrocytes within cartilage.
Isogenous group manifacture matrix, pushed away from each other, forming seperate lacunae and thus enlarging he cartilage from within.
APPOSITIONAL GROWTH: growth from undifferentiated cells at the surface of the cartilage or perichondrium.
thw chondrogenic cells in the inner cellular layer of the perichondrium undergo division and differentiate into chondroblasts, which begin to elaborate matrix.
types of cartilage
1. hyaline cartilage
2. elastic cartilage
3. fibrous cartilage
Hyaline cartilage özellikler
1. it is avascular
2. it consists of chondrocytes surrounded by territorial and interterritorial matrices containing type 2 collagen interacting with proteoglycans
3. ıt occurs in the temporary skeleton of the embryo, articular catilage ( ends of long bones, ends of ribs) and the cartilage of the respiratory tract (nose, parts of larynx, trachea, bronci, bronchial tubes.
elastic cartilage özellikleri
1. it is avascular
2. it is surrounded by perichondrium
3. it consists of chondrocytes surrounded by territorial and interterritorial matrices containing type 2 collagen interacting with proteoglycans and elastic fibers
4. elastic fibers can be stained by orcein for light microscopy
5. it occus in the external ear, epiglottis and auditory tubes.
elastis cartilage examples
1. auricle or pinna
3. external auditory meatus
1. it is generally avascular
2. ıt lacks of perichondrium
3. it consists of chondrocytes and fibroblasts surrounded by type 1 collagen and a less rigid ECM
4. it predominates in the intervertebral disks, articular disk of the knee , mandible, sternoclavicular joints, and pubic symphysis.
damaged cartilage undergoes slow and incomplete repair, primarily by the activiy of cells int the perichondrium whic invade the injured area and produce new cartilage and this character is not seen in young children
in extensively damaged areas, perichondrium produces a scar of dens connective tissue instead of new cartilage
the poor capacity of cartilage for repair or regeneration is due to its avascular in nature
1. support and protection for the body and its organs
2. a reservoir for calcium and posphate ions
bone is composed of
1. support celss (osteoblasts, osteocytes)
2. a non-mineral matrix of collagen and GAG's (osteoid)
3. inorganic mineral salts deposited within the matrix
4. remodeling cells (osteoclasts)
Osteoid and bone matrix consists of organic ?% and inorganic ?% components
organic 30%, and inorganic 70%
organic bone matrix
type 1 collagen (90%),
proteoglycans enriched in chondroitin sulfate,
noncollagenous matrix proteins are osteocalcin, osteopontin, osteonectin, bone sialoprotein.
inorganic bone matrix
inorganic bone matrix is represented predominantly by deposits of calcium phosphate wit the crystalline characteristics of hydoxyapetite.
stem cells of bone
synthesize the organic component of bone matrix(osteoid), mineralice it by depositing calcium and phosphate hydroxies (hydroxyapetides)
inactive osteoblasts trapped in mineralized bone, lie within small cavities. Adjacent cell processes found within canaliculi are connected by gap junctions.
multinucleate cells, derived from monocytes, erode ineralized bone, localized in Howship's lacuna
classification of bones
spongy or cancellous bone
types of bone on the basis of microscopic organisatiiın of ECM
lamellar bone: typical mature or compact bone
Woven bone: observed in the developing bone
lamellar bone consists of lamellae, largely composed of bone matrix, and osteocyts each occupying a cavit or lacuna with radiating and branching canaliculi.
vascular channels in compact bone
lamellar bone displays four distinct patterns
1. osteons of Haversian system
2. interstitial lamella
3. outer circumferential lamellae
4. inner cimcumferential lamellae
periosteum: Inner layer
during embryonic period consist of bone-forming cells (osteo-blasts), is the osteogenic layer. In the adult, periosteum contains inactive connective tissue cells that retain their osteogenic potential in case of bone injury.
periosteum: Outer layer
Rich in blood vessels, some of them entering volkman's canal, and thick anchoring collagen fibers, called Sharpey's fibers, that penetrate the outer circummferential lamellae in the bone.
consists of squamous cells and connective tissue fibers covering the spongy walls housing the bone marrow and extending into all the cavities of the bone, including the Haversian canals.
mineralization of osteoid
1. a glycoprotein (osteocalcin) in osteoid binds extracellular Ca ions, leading to a high local concentration.
2. The enzyme alcaline phosphatase, which is abundant in osteoblasts increases local ca and po4 concentration.
3. Osteoblasts produce matrix vesicles, whic can accumulate Ca and PO4 ions from larger molecules.
selective bone resorbtion
1. lysosomal enymes are released by osteoclasts.
2. released enzymes hyrdolyse the collagenous protein and GAG's of the bone matrix.
3. the disrupted bone matrix yields up its attached mineral salts.
4. local acidic conditions result from the secretion of organic acids such as carbonic, lactic, and citric acids by osteoclasts, break up the hydroxyaptie, releasing soluble Ca and PO4 ions.
5. soluble break own products of demineralisation and proteni hydrolysis may be resorbed by the osteoclast by endocytosis.
6. osteoclasts resorbtion of bone can be stimulated by parathormone and inhibited by calcitonin.
both cortical and trabecular bone is thing
Osteoclasts are very active