Lecture 7/8 Flashcards
bone
what can stimulate cartilage growth?
growth hormone, thyroid hormone, testosterone
what can retard cartilage growth?
corticosteroids, estradiol, retinoids
what are tumors that can form in cartilage?
chondroma, chondrosarcoma
bone is one of the _______ tissues of the body
hardest
what are the cell types found in bone?
with roles
- osteoprogenitor cell: stem cells
- osteoblast: synthesize the organic camponent of the matrix
- osteocyte (in lacunae - inactive)
- osteoclastst: multinucleated cells involved in bone resorption
what is found in the ECM of bone?
- fibers: type 1 collagen
- ground substance: proteoglyacns, glycoproteins (sialoprietin and soteocalcin)
- minerals: crystal of hydroxyapatite
calcified cartilage
what special histological technique is required for bone?
decalcification (5% nitric acid or EDTA treatment)
how can we classify bone based on: gross appearance, microscopy appearance, development appreance?
- gross: compact or cancellous (spongy)
- micro: woven (immature) or lamellar (mature)
- dev: intramembranous or endochondrial
layers of bone
inside from outside
- endosteum
- inner circumferential system
- inside: haversian system, interstitial system
- outer circumferential system
- periosteum
what are the different canals found in bone?
and describe them
- haversian canal: in the middle of a haversian system and runs with the bone
- volksmann canal: perpendicular to the bone, drains to the bone marrow
role of an osteoclast
contains carbonic anhydrase which uses CO2 and H2O to make H+, used to make an acidic microenvironemnt to make bone, and bicarbonate, which goes in capillaries.
what are the layers/general makeup of long bones?
from top to bottom
- proximal epiphysis: articular cartilage, epiphyseal line, and spongy bone
- metaphysis: spongy bone
- dyaphysis: compact bone with bone marrow inside
- metaphysis: spongy bone
- distal epiphysis: same as proximal
where do we see intramembranous ossification?
in flat bones (mandibular, maxilla, occipital, temporal, parietal bones)
what is the process of intramembranous ossification?
- within plates of mesenchymal cells, primary ossification occurs, where the first group of mesenchymal cells differentiate into osteoblasts
- then, they synthesize ECM, which encapsulate osteocytes and form spicules.
- then this is repeated in secondary ossification centers
- in the periphery, the mesenchymal cells with differentiate into the periosteum
where does endochondrial ossification occur?
within a piece of hyaline cartilage with a simialr shape of the bone to be formed, and is surrounded by perichondrium except at sites of future articular sites
steps of primary endochondrial ossification
- at the level of the diaphysis, the perichondrium is transformed into periostieum which deposits bone (called bone collar)
- the bone collar prevents the diffusion of nutrients and the cartilage degenerates (hypertrophy and cell death following by calcification of ECM)
- blood vessles invade from the perichondrium, the spaces left by the degenerating chondrocytes and carry osteoprogenitor cells
- differentiating osteoblasts divide and secrete ECM
steps of secondary endochondrial ossification
- takes place at the epiphysis of the future bone
- the cartilage degenrates and is invaded by blood vessels from the perichodnrium, transformed into periosteum
- cartilage persists in articular surface and epiphyseal plate
how is the bone marrow formed?
during the remeodelling phase of ossification: osteoclastss are active in the resorption of calcified cartilage and wovem bone,w hcih leads to the formaion of a hollow marrow
layers of the epiphyseal plate
- zone of resting cartilage
- zone of rpoliferation
- zone of hypertrophy
- zone of cell death
- zone of mixed spicules
endochondral ossification permits growth in what?
length via the proliferation of chondrocytes
bone growth occurs up to X years
20
what regulates bone growth?
growth hormone
how exactly does ossification lead to length-wise bone growth?
even if the epiphyseal plate does not get bigger in size (rate of chondrocyte proliferation = rate destruction of spicules), the plate is displaced away from the middle
chondrogenesis occurs where?
at the epiphyseal plate
where does radial bone growth occur?
in the perichondrium
effect of nutritional Calcium deficiency?
decalcification of bone
which hormone promotes bone growth?
and its role
parathyroid hormone; acts on osteoclastst, which stop the production of bone and start the secretion of osteoclast stimualting factor
what hormone inhibits bine growth?
and its role
calcitonin; inhibits bone resorption
what causes pituitary dwarfism?
lack of GH
what causes gigantism?
excess GH
what causes acromegaly?
excess GH
