skeletal connective tissue Flashcards
what are the characteristics of cartilages
- avascular
- contain perichondrium
- few cells
- extracellular matrix (95%)
what are the functions of cartilages
- movement - joins bones firmly together
- support - maintain shape of organs
- growth - hyaline cartilage is responsible for longitudinal growth of long bones
what are the types of cartilage
- hyaline
- elastic
- fibrocartilage
what are the types of bone
- primary/ immature or woven
- secondary, mature or lamellar
what is the histogenesis of cartilaginous tissue
- mesenchymal cells
- mitotic division of mesenchyme leads to thickening
- chondroblasts produce extracellular matrix
- division of chondroblasts produce chondrocytes
what is the perichondrium
- connective tissue covering cartilage
- located on all surfaces of cartilage apart from articular surface and fibrous cartilage
what is the function of the perichondrium
- anchoring point for ligaments and tendons
- nutritional source
- source of stem cells for growth and repair for the cartilage
what are the layers of the perichondrium
- outer fibrous later
- inner chondrogenic layer
what does the outer fibrous layer of the perichondrium contain and do
- contains collagen fibres, fibroblasts and blood vessels
- provide the attachment site for other structures
- source of nutrients for avascular cartilage matrix
what does the inner chondrogenic layer of the perichondrium contain and do
- contains chondroblast which actively secrete the matrix
- important for appositional growth
what the two types of growth of the cartilage
- appositional - growth from periphery
- interstitial - growth from inside
what is interstitial growth
- growth from the inside
- mitosis of cells within the matrix
- results in clusters of chondrocytes called cell nests or isogenous groups
what is appositional growth
- growth from the periphery
- growth of the chondroblasts within the perichondrium
what is the structure of cartilaginous tissue
- cells - chondroblasts and chondrocytes
- extracellular matrix - fibres and ground substance
what is the differentiation of cells to form chondrocyte
chondroprogenitor cell ( mesechymal stem cells) —-> chondrobast —> chondrocyte
what fibres are present in cartilage
- type 2 - only in cartilage
- type 6,9,11 - in collagen and elastic fibres
what are the amorphous ground substances
- proteoglycans - hyaluronan, chondroitin sulfate and keratin sulfate
- glycosaminoglycans and water - rigidity
- multi adhesive glicoproteins - anchorin CII, tenansin and fibronectin
what happens to cartilage when the amount of keratin sulfate increases
increases firmness
what is the capsular (pericellular) matrix
ring of more densely stained matrix located immediately around each chondrocyte
- contains only type 6 cartilage
what is the interterritorial matrix
matrix does not directly surround the cell and is present in greater quantity
what is the territorial matrix
cartilage directly surrounds the chondrocytes, stains at high intensity
where is hyaline cartilage found
- major part of fetal skeleton
- surface of joins and synchondroses of the skull base
- rib cartilages
- large laryngeal cartilage
- nasal cartilages
what are the structural features of hyaline cartilage
- presence of isogenous groups of chondrocytes
- ground substance contains a dense network of collagen fibres
- contain perichondrium
what is articular cartilage
hyaline cartilage on the articular surfaces of bones
what are the features of articular cartilage
- no perichondrium - receives nutrition from synovial fluid
- limits regeneration ability
- low metabolic rate and due to insufficient oxygen - anaerobic metabolism
what is osteoarthritis
common joint disease due to injury of articular cartilage
- occurs by 65
what is the symptoms of osteoarthritis
- chronic joint pain - weight bearing joints
what is the pathology of osteoarthritis
- decrease in proteoglycan content and water or cartilage matrix
- chondrocytes produce more interleukin 1, tumour necrotic factor and less type 2 collagen and proteoglycans
where is elastic cartilage found
- auricle - auditory tube
- epiglottis
what does elastic cartilage contain
- chondrocytes or isogenous groups of chondrocytes - chain
- ground substance contains a dense network of branching and anatomosing elastic fibres
- has perichondrium
what is fibrocartilage
specialised type
found in areas requiring tough support or greater tensile
where is fibrocartilage found
- Annulus fibrosus of intervertebral discs
- Interpubic disc of the pubic symphysis
- Manubriosternal and xiphisternal joints
- Articular menisci and discs
- Artiсular cartilage in joints are exposed to high pressure and tension (temporomandibular, sacroiliac, sternocostal joint)
- Small pieces of fibrous cartilage (fibrocartiagines) of small hand and foot joint
what are the structure features of fibrocartilage
- chondrocytes or isogenous groups of chondrocytes arranged in
long rows - ground substance contains lots of collagen fibres - functional stresses
- no perichondrium
what is achondroplasia/ dwarfism
- autosomal dominant
- mutation of fibroblast growth factor receptor 3 (FGFR3) gene
what is the pathogenesis of achondroplasia/ dwarfism
- defective proteins interfere with conversion of cartilage
- decreased endochrondral bone formation and premature ossification of growth plates
what is the extracellular matrix of the bone tissue like
calcified
what is found in bone tissue
- calcium
- phosphate
- other ions
what happens to the ions found in bone tissue
released or stored to maintain concentrations in body fluid
what type of tissue is bone marrow
hematopoiectic tissue
what are the classification of bones
- based on shape and length
- long
- irregular
- flat
- short
what are the 2 parts of a long bone
- diaphysis - hollow region called medullary cavity containing yellow marrow
- epiphysis - filled with red bone marrow
- between 2 parts is metaphysis containing growth plate
types of histological bone tissue
- primary/ immature/ woven
- secondary/ mature/ lammetlar - split into compact dense bone and spongy bone
what is compact bone composed of
osteons
what is spongy bone composed of
trabeculae
what cells are in bone tissue
- oseoprogenitor cells
- osteoblasts
- osteocytes
- osteoclasts
what does the matrix of bone tissue contain
- organic component - osteoid - collagen fibres and ground substances
- inorganic component - calcium hydroxyapatite and water
what are osteoprogenitor cells
mesenchymal stem cells
located in inner cellular layer of periosteum
what are osteoblast
produce components of bone matrix
associated with growing surface of bone
what are osteocytes
watcher cells, sit on bone and monitor current status
- located in lacunae
what are osteoclasts
degrade and resorb bone for remodelling
what cells originate from mesenchymal stem cells
osteoprogenitor cells
osteoblasts
osteocytes
where do osteoclasts originate from
blood monocytes
what do osteoclasts contain
- developed lysosomes
- acid phosphatase, metalloprotinase and collagenase to degrade bone matrix
what are howships lacunae
osteocytes forms erosion resorption bays
what are the zones of osteoclasts
- basal zone
- ruffled boarder
- clear zone
- vesicle zone
what is the basal zone of osteoclasts
contains most organelles except mitochondria
what is the ruffled boarder of osteoclasts
at osteoclast-bone interface where resorption occur
what is the clear zone of osteoclasts
organelle free region periphery of the ruffled boarder
expresses intergins
what is the vesicular zone of osteoclasts
between basal zone and ruffled boarder
rich in exocytotic and endocytotic vesicles with lytic enzymes
what does the inorganic component of the bone matrix contain
- calcium and phosphate
- deposition of minerals for hydroxyapatite crystals which hardens matrix
what is found in the organic component of the bone matrix
- proteoglycans
- glycoproteins osteonectin
- bone specific protein - vitamin K dependent
- growth factors - BMPs, sclerostin
what is the periosteum
external sheath of dense connective tissue
what are the 2 layers of periosteum
- outer fibrous tissue - firmly attached to bone
- inner cellular layer - contains esteoprogenitor cels
what is the endosteum
thin layer of osteoprogenitor, osteoblasts and small amount of connective tissue
- lines all internal surfaces of cavities within bones
what are the functions of perlosteum an endosteum
- numerous blood vessels enter the bone through periosteum giving nutrition
- osteoprogenitor cells involved in growth and repair
- mechanical support
what are the characteristics of primary bone tissue
- abundant osteocytes
- low mineral content
- irregular organisation of collagen fibres
- mechanically weak
where is primary bone tissue located
- embryo skeleton
- flat bones of skull
- tooth sockets
- tendon insertions
what is lamellae of bone tissue
bone matrix arranged in parallel sheets
provides strength to bone
what is the characteristics of lamellar bone tissue
- collagen fibres run parallel forming lamella
- collagen of adjacent lamellae run at 90 degrees
- osteocytic processes extend through canaliculi
what do lamellae contain
lacunae housing osteocytes which get nutrition by diffusion from the marrow cavity
what is the canaliculi
narrow channels in the calcified bone matrix
what is the epiphyses of long bones composed of
spongy bone covered by a thin layer of compact bone
what is the diaphysis of bone tissue composed of
compact bone
what are short bones composed of
core of spongy bone surrounded by compact bone
what is the structural unit of compact bone
osteon - long cylinder called Haversian system
what does each osteoblasts consist of
a single central canal surrounding lamellae and osteocytes
what does the central canal/ Haversian canal of osteons contain
blood vessels, lymphatic vessels and nerves
how is one osteon connected to another
volkmanns canal or perforating which connects the periosteum and endosteum
where is outer circumferential lamellae present
beneath the periosteum
where is the inner circumferential lamellae present
marrow cavity over the endosteum
where is interstitial lamellae found
between osteons
what are endochondral bones
forms from hyaline cartilaginous model and ossifies through process of endochondral ossification
what are membrane/ dermal bones
develops from ossification directly from mesenchyme through intramembranous ossification
what is the hyaline cartilage of the epiphyseal plate
continues to grow and continuously replaced by newly formed bone matrix resulting in elongation of bone
- only in children
what are the 4 stages of bone remodelling
1) fracture hematoma is formed which is gradually replaced by granulation tissue
2) granulation tissue transforms into fibrocartilgainous soft callus
3) bony hard callus replaces firocartlxage
4) woven primary bone tissue is replaced by lamella bone tissue
