cartilage and bone module Flashcards
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fibrocartilage
characteristics of hyaline cartilage
- Type II collagen, chondrocytes usually arranged in groups
- perichondrium present except articular surfaces
- articular ends of long bones, nose, larynx, trachea, bronchi, ventral ends of ribs, template for endochondral bone formation
elastic cartilage characteristics
possesses a perichondrium and is nearly identical to hyaline cartilage except for a network of elastic fibers, which impart a yellowish color. Although it contains type II collagen, it is less prone to degeneration than hyaline cartilage and is located in areas where flexible support is required.
Fibrocartilage characteristics
lacks an identifiable perichondrium. It is characterized by alternating rows of fibroblast-derived chondrocytes surrounded by a scant matrix and thick parallel bundles of type I collagen fibers. Fibrocartilage is located in areas where support and tensile strength are required.
types of hitiogenesis
interstitial growth
appositional growth
interstitial growth
[Existing chondrocytes] ➡ [More chondrocytes]
Occurs (1) during the early stages of cartilage formation, (2) in articular cartilage, and (3) in epiphyseal plates of long bones
Appositional growth
- Occurs in perichondrium
- Chondrogenic cells ➡ Chondroblasts ➡ Chondrocytes
- These new cells elaborate a new layer of cartilage matrix at the periphery.
osteoclasts arrise from
hematopoetic stem cell- monocyte lineage
Functions primarily to support soft tissues and assist in the development and growth of long bones.
cartilage
Has a firm extracellular matrix that is less pliable than that of connective tissue proper
cartilage
Avascular specialized fibrous connective tissue
cartilage
matrix of cartilage
Composed of an amorphous ground substance containing proteoglycan aggregates and chondronectin, in which type II collagen is embedded.
has territorial and interterritorial matrix
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collagen matrix
territorial matrix
Adjacent to chondrocytes
Poor in collagen
Rich in proteoglycans
Stains more deeply
Region away from chondrocytes
Rich in collagen
interterritorial matrix
chondroblasts
- Manufacture the cartilage matrix through which nutrients and waste materials pass to and from the cells
- Differentiate into chondrocytes
chondrocytes
- Mature cartilage cells that are embedded within lacunae in the matrix
- Arise from chondroblasts in the perichondrium
Chondrocytes arise by differentiation of ____ chondrogenic cells and from chondrogenic cells within the inner layer of the perichondrium into _____, which are the earliest cells to produce cartilage matrix.
mesenchymal
chondroblasts
perichondrium
-A layer of dense, irregular connective tissue that surrounds…
Hyaline cartilage (except at articular surfaces)
Elastic cartilage
provides the nearest blood supply to the avascular cartilaginous tissue
perichondrium
degeneration of chondrocytes
Occurs when chondrocytes undergo hypertrophy and die and the matrix becomes calcified, a process that becomes more frequent with age
Degeneration of hyaline cartilage is a normal part of ______ bone formation.
endochondral
most abundant cartilage in the body
hyaline
serves as a temporary skeleton in the fetus until it is replaced by bone
hyaline cartilage
A specialized type of connective tissue with a calcified extracellular matrix in which osteocytes, osteoblasts, and osteoclasts are embedded
bone
functions of bone
Protect vital organs
Support fleshy structures
Provide a calcium reserve
Inorganic (calcified) matrix
~65% of the dry weight
Composed of calcium, phosphate, bicarbonate, citrate, magnesium, potassium, & sodium
Consists primarily of hydroxyapatite crystals: Ca10(PO4)6(OH)2
inorganic calcified matrix
~35% of the dry weight of bone
organic matrix
type of collagen fibers in organic matrix
type 1
organic matrix has a ground substance that contains ___ and ___
chondroitin sulfate & keratan sulfate
Located in the periosteum and the endosteum
Differentiate into osteoblasts
osteoprogenitor cells
Spindle-shaped cells derived from embryonic mesenchyme
osteoprogenitor cells
osteoblast appearance
Cuboidal when active, flat when inactive (a.k.a., “bone-lining cells”)
osteoblasts
- Responsible for synthesis of organic matrix (e.g., type I collagen, proteoglycans, and glycoproteins) which they secrete as osteoid (uncalcified bone matrix)
- Possess receptors for parathyroid hormone (PTH)
- Become entrapped in lacunae (small spaces) but maintain contact with other cells via their cytoplasmic processes
entrapped osteoblasts are ___
osteocytes
Mature bone cells housed in their own lacunae (small spaces)
osteocytes
how do osteocytes communicate
gap junctions
Nourished and maintained by nutrients, metabolites, and signal molecules carried by the extracellular fluid that flows through the lacunae and canaliculi.
osteocytes
calcium released from bone enters the extracellular fluid located within these spaces.
lacuna and canaliculi
osteolysis
osteoclasts
Osteoclasts (O) form and reside in depressions known as ______, which represent areas of bone resorption.
Howship’s lacunae
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Osteoclasts possess cell surface receptors:
colony-stimulating factor-1 receptor,
calcitonin receptor,
RANK (nuclear factor kappa B).
osteoblasts that have been stimulated by PTH promote
PTH casues osteoblasts to decrease bone formation which releases osteoclast stimulating factor, this leads to increased bone resoprtion, liberation of calcium, in osteoclast formation
osteopontin
secreted by osteoblasts, is used to seal the zone between osteoclasts and the subosteoclastic compartment.
osteoclast zones
basal zone
ruffled border
clear zone
vesicular zone
Contains exocytotic vesicles that transfer lysosomal enzymes to Howship’slacunae and endocytic vesicles that transfer degraded bone products from Howship’s lacunae to the interior of the cell.
vesicular zone of osteoclasts
ruffled border of osteoclast
Site of active bone resorption
Composed of irregular fingerlike cytoplasmic projections extending into the subosteoclastic compartment, a slight depression that deepens as the osteoclast resorbs bone, resulting in Howship’s lacuna
steps of bone resorption
- Osteoclasts secrete acid, which decalcifies the surface layer of bone.
- Acid hydrolases, collagenases, and other proteolytic enzymes secreted by osteoclasts then degrade the organic portion of the bone.
- Osteoclasts resorb the organic and inorganic residues of the bone matrix and release them into connective tissue capillaries.
periosteum
A layer of noncalcified connective tissue covering bone on its external surfaces except at synovial articulations and muscle attachments
Composed of an outer dense fibrous collagenous layer and an inner cellular osteoprogenitor (osteogenic) layer.
periosteum
Sharpey fibers
(type I collagen) attach the periosteum to the bone surface
Functions to distribute blood vessels to bone
periosteum
A thin specialized connective tissue that lines the marrow cavities
endosteum
Supplies osteoprogenitor cells and osteoblasts for bone growth and repair
endosteum
spongy bone also called
cancellous or trabecular bone
Trabeculae contain ____ and are lined on both surfaces by a single layer of _____.
osteocytes
osteoblasts
spongy bone is always surrounded by
compact bone
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dense or cortical bone
compact bone
compact bone
has no trabeculae or bone marrow cavities
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primary bone
the first compact bone produced during fetal development and bone repair. It is remodeled and replaced by secondary bone.
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contents of primary bone
Many osteocytes
Large, irregularly-arranged type I collagen bundles
Low mineral content.
places where primary bone remains without replacement
tooth sockets
near suture lines in skull bones
insertion sites of tendons
mature or lamellar bone
secondary bone
compact bone of adults
seconday bone
bone remodeling
the combination of bone formation and resorption
Intramembranous bone formation produces bone that is ______ to bone produced by endochondral bone formation.
histologically identical
centers of developing bone where osteoblasts become trapped in their own matrix
trabeculae (fused spicules)
Fusion of the bony trabeculae produces spongy bone as blood vessels invade the area and other undifferentiated mesenchymal cells give rise to the
bone marrow
The _____ and _____ develop from portions of the mesenchymal layer that do not undergo ossification.
periosteum
endosteum
endochondral formation
Begins in a segment of hyaline cartilage that serves as a small model for the bone
Two stages of endochondral bone formation:
Two stages of endochondral bone formation:
Primary center of ossification
-Occurs at the midriff (middle of diaphysis, or shaft)
Secondary center of ossification
-Occurs at the ends of the bones
haversian systems are composed of 4 to 20 _____ surrounding a central Haversian canal, which contains blood vessels and nerves
lamellae (calciied concentric layers)