Bone and Cartilage Flashcards
What are the three major classes of cartilage?
hyaline, elastic, fibrocartilage
What are the two components of cartilage?
cells (chondroblasts and chondrocytes) and extracellular matrix.
What are chondroblasts?
cartilage-forming cells
What are chondrocytes?
cartilage-maintenance cells
What is in the cartilage extracellular matrix?
collagen (type II) and amorphous ground substance
What are some functions of cartilage?
absorb shock, reduce friction, repair bone fractures, necessary for endochondral bone growth.
What do chondroblasts become after they lay down cartilage matrix?
chondrocytes
What are lacunae?
Pockets within the matrix where the chondroblasts and chondrocytes are found.
Is cartilage vascular or avascular?
avascular
How does cartilage receive nutrients?
diffusion through the cartilage matrix
What is the perichondrium?
A layer that can give rise to chondroblasts. It contains an outer fibrous layer and an inner chondrogenic layer.
What does the outer fibrous layer contain, and what do they differentiate into?
fibroblasts; they differentiate into chondroblasts.
What does the inner chondrogenic layer give rise to?
chondroblasts, which become chondrocytes.
What are functions of the chondrocyte?
produce collagen and proteoglycans, secrete chondronectin (adhesion molecules).
What is in the cartilage matrix?
collagen type II, hyaluronic acid, glycosaminoglycans, terriritorial and inter-territorial matrices
What matrices surround each chondrocyte?
territorial and inter-territorial; the territorial has a high GAG content and low collagen content and vice versa for inter-territorial.
What is hyaline cartilage often referred to as?
gristle; it is the most common type of cartilage
What are features of hyaline cartilage?
avascular, contains type II collagen fibers, surrounded by perichondrium, grows appositionally or interstitially.
Where is hyaline cartilage located?
fetal long bones, articular ends of bones, tracheal cartilages, larynx
What is the matrix of hyaline cartilage composed of?
chondroitin sulfate, collagen fibers and proteoglycans
What is the chondrogenic perichondrium a source of?
chondroblasts and osteoprogenitor cells.
What are characteristics of elastic cartilage?
has elastic fibers in the matrix, surrounded by perichondrium, is flexible, has type II collagen.
Where is elastic cartilage found?
auricle (pinna) of the ear, epiglottis.
What are characteristics of fibrocartilage?
increased collagen, not surrounded by pericardium, type I collagen, sparse chondrocytes, has good tensile strength.
Where is fibrocartilage located?
intervertebral discs, pubic symphysis, tendons & ligaments
Where does interstitial growth occur?
from chondrocytes within the cartilage
During embryogenesis, what do mesenchymal cells differentiate into?
chondroblasts
What do the chondroblasts from the mesencyhmal cells then do?
Divide mitotically and fill the lacuna; they are surrounded by territorial matrix and inter-territorial matrix; which is known was INTERSTITIAL GROWTH.
Where does appositional growth occur?
from undifferentiated cells at the surface of the cartilage, or perichondrium.
What do the inner layers of the perichondrium do during appositional growth?
Differentiate into condroblasts and synthesize/secrete type II collagen precursors and other ECM components.
What kind of a system is bone tissue based on?
canalicular
Is bone vascular or avascular?
vascular
How does bone increase in length?
through appostional growth of a hyaline cartilage model.
What is bone formed by?
osteoblasts, which become osteocytes.
What is the organic components of a bone?
the osteoid
What is the inorganic component of a bone?
hydroxyapatite
What are the three types of bone?
woven bone, compact bone, spongy bone
When is woven bone most commonly seen?
during bone development and repair
When is compact bone also referred to as?
lamellar bone
What is spongy bone also referred to as?
trabecular or cancellous bone
What are the lamellae which encircle a central blood vessel?
Haversian
Where are the osteocytes found, and how are they connected?
between the lamellae; they are connected via canaliculi.
What do Volkmann’s canals do?
run perpindicular to haversian canals and connect the haversian canals to each other and to the surface of the bone.
What does spongy bone contain? What does it surround?
trabeculae; they surround bone marrow spaces in long bones and flat bones.
What is the periosteum?
A membrane that surrounds the entire bone.
What are Sharpey’s fibers?
fibers that connect to bone and periosteum. They are abundant where tendons and ligaments attach.
What are osteocytes responsible for?
maintenance and turnover of the bone matrix.
What do osteoprogenitors differentiate into?
osteoblasts, then osteocytes
What do osteoblasts do?
control the mineralization of the matrix. They also synthesize the organic matrix of bone.
What are the major protein products of an osteoblast?
type I collagen, RANKL, osteocalcin, osteopontin, bone siatoprotein.
Where are osteoclast cells derived from?
monocytes (bone marrow)
What occurs at adult remodeling sites and during development?
ARF (activation-resorption-reversal-formation).
What is the primary regulator of bone turnover?
parathyroid hormone.
What is stimulated at low PTH levels?
bone formation by osteoblasts.
What is stimulated at high PTH levels?
osteoclast-differentiation factors (turns osteoblasts into osteocytes).
What does the osteoblast synthesize after PTH binds to receptors on the osteoblast?
M-CSF (monocyte colony stimulating factor) and RANKL. The osteocyte releases M-CSF.
What does M-CSF bind to?
an M-CSF receptor on a nearby monocyte.
What does a monocyte bound to M-CSF become?
a macrophage that expresses RANK
What does RANK bind to?
RANKL (osteoblast and macrophage binding).
What does a macrophage become once it has bound to RANKL?
an immature osteoclast.
What is osteoprotegerin?
substanced secreted by the osteoblast that binds to RANKL with greater affinity than rank. It inhibits maturation of osteoclasts.
What does PTH block?
synthesis of osteoprotegerin.
What are osteoclasts directly regulated by?
calcitonin, vitamin D and regulatory molecules of the osteoblasts.
What are functions of the osteoclasts?
Bone remodelling (removing bone matrix and replacing with osteoblasts), proper shaping of the bones, extension of medullary space to allow for hematopoiesis.
