Bone and Cartilage Flashcards
What are the three major classes of cartilage
Hyaline, Elastic, fibrocartilage
The skeletal system in all vertebrates begins with ______
Cartilage
What makes up the ECM of cartilage
Collagen fibers (mostly type II collagen (Type I in fibrocartilage) amorphous ground substance
what cells make up cartilage
Chondroblasts and Chondrocytes
Cartilage functions
Compressible, resists distortion, absorbs shock in joints, reduces friction in movable joints, necessary for endochondral bone growth, Involved in bone fracture repair
Function of chondroblasts
Lay down cartilage matrix and become chondrocytes
Function of Chondrocytes
Maintain cartilage matrix
produce collagen and proteoglycans in the matrix
secrete chondronectin
what are lacunae
Pockets within the matrix where the chondroblasts and chondrocytes are found
Why is cartilage slow to heal
It is Avascular
Nutrients and oxygen are derived form blood vessels that surround the cartilage and must diffuse through the matrix to the cells
What type of collagen is found in the ECM of fibrocartilage
Type I
What type of collagen is found in the ECM of hyaline and elastic cartilage
Type II
Where is the Perichondrium found
on the outer surface of cartilage
How many layers does the perichondrium have
2
What are the two layers of the perichondrium
The outer fibrous layer
+ - contains fibroblasts
The inner chondrogenic layer
- Gives rise to chondroblasts, which become chondrocytes
- The chondrocyte is involved in the production of the collagen and proteoglycans in the matrix. Chondrocytes also secrete chondronectin
what is an isogenous group
Groups of 2-8 chondrocytes occupying the same lacunae
result of mitotic division
cells will become separated as they begin to lay down matrix of their own
Components of the cartilage ECM
Collagen (type II in most cartilage and Type I in fibrocartilage)
Hyaluronan (hyaluronic acid)
Chondroitin sulfate, keratan sulfate, heparin sulfate
Glycosaminoglycans
what is territorial matrix
Matrix that directly surrounds each chondrocyte
high glycosaminoglycan content, low collagen content
What is inter-territorial matix
Surrounds territorial matrix
low glycosaminoglycan content: high collagen content
what is the most common type of cartilage
Hyaline
What type of Collagen makes up hyaline cartilage
Type II
Is hyaline cartilage surrounded by a pericondrium
Yes
What color is hyaline cartilage
Translucent, bluish gray to white
Describe the texture of hyaline cartilage
solid but flexible
What are the growth patterns of hyaline cartilage
appositional
Interstitial growth
Where is hyaline cartilage located
External auditory meatus Larynx Tracheal Cartilages Bronchial Cartilages Fetal long bones Articular ends of bones
What does elastic cartilage have added to its matrix that hyaline cartilage doesn’t
Elastic fibers
Is elastic cartilage surrounded by a perichondrium
Yes
what is the color of elastic cartilage
Yellow
Why is elastic cartilage yellow in appearance
because of the presence of elastic fibers
Describe the appearance of elastic cartilage
More opaque, flexible, and elastic than hyaline cartilage
How are chondrocytes arranged in elastic cartilage
Located singly
What type of collagen is in the matrix of elastic cartilage
Type II with the addition of elastic fibers
Where is elastic cartilage found
Auricle (pinna) of the ear
Epiglottis
how are chondrocytes arranged in hyaline cartilage
often found in cell groups (resulting form cell division)
what has more collagen in the matrix fibrocartilage or hyaline
Fibrocartilage
Which type of cartilage has a lower cellularity hyaline or fibrocartilage
Fibrocartilage
Is Fibrocartilage surrounded by a perichondrium
No
what is the appearance of fibrocartilage
opaque from fibrous texture
What type of collagen makes up fibrocartilage
Type I
Explain the chondrocyte appearance/location in fibrocartilage
single sparse chondrocytes
Where is fibrocartilage located
intervertebral discs, pubic symphysis, insertion f some tendons and ligaments, closely associated with dense CT or hyaline cartilage
is bone vascular
Yes! it is highly vascular and found in close proximity to capillaries
How does bone length increase
Through the appositional growth of hyaline cartilage model
Bone is formed from what kind of cells
Osteoblasts
Bone matrix consists of what two major components
Organic component referred to as osteoid
inorganic component referred to as hydroxyapatite which makes up 35-65 percent of the matrix
What is the organic component of the bone matrix
Osteoid
What is the inorganic component of the bone matrix
hydroxyapatite which makes up 35 to 65 percent of the matrix
Bone tissue is continuously _____, _______, and ______
Resorbed , reconstructed, and remodeled
How much of the matrix is made from hydroxyapatite
35-65 percent
What are the three types of bone arrangement
Woven bone, Compact bone, and spongy bone
What is another name for compact bone
lamellar bone
What is another name for spongy bone
Cancellous bone
When does woven bone occur
occurs during development and bone repair
compact bones lack _____ and form a ______ on the outside of long bones or flat bones
cavities, dense plates
Compact bone consists of _______ lamellae which encircle a central blood vessel (and associated nerves) forming an osteon, or haversian system
Concentric (Haversian)
where are osteocytes found in compact bone
They are found between the lamellae, located in lacunae
How are osteocytes connected to one another and the haversian canal in compact bones
via canaliculi
_____ _____ run perpendicular to the Haversian canals and connect the Haversian canals to each other and to the surface of the bone
Volkmann’s canals
what kind of bone has a 3-D lattice of branching, bony spicules intertwined to form trabeculae surrounding the bone marrow spaces in the long bones and flat bones
Trabecular (Spongy) bone
Describe the characteristics of bone’s macroscopic structure
Periosteum, Marrow (medullary) cavity, Endosteum, Sharpey’s fibers
What are Sharpey’s fibers
These are special bundles of collagen fibers that nail tendons and ligaments to the bone
What are Osteoprogenitor cells
Stem cells which in the adult are described as bone lining cells
- give rise to osteoblasts and bone lining cells
where are osteoprogenitor cells found
in the inner portion of the periosteum, in the endosteum, and lining vascular canals of compact bone
What are osteoprogenitor cells derived from
Mesenchyme of the embryonic somite (sclerotome) and possess mitotic potential
What are osteocytes derived from
osteoblasts and are trapped by the matrix they secrete
What are osteoblasts derived from
osteoprogenitor cells
what are osteoblasts characterized by
Alkaline phosphatase and Vitamin D3
What are the major protein products of Osteoblasts
Type I collagen
Noncollagenous proteins:
- Osteocalcin
- Osteonectin
- Osteopontin
- Osteoprotegerin
- RANKLWhat is the primary regulator of bone turnover
Parathyroid Hormone (PTH)
What is stimulated at low PTH levels
bone formation by osteoblasts
What is stimulated at high PTH levels
Osteoblasts are stimulated to release osteoclast-differentiation factors
What is a result of elevated PTH levels
eroded bone and fibrosis of the resulting spaces (osteitis fibrosa) (bone is removed and replaced with cartilage)
What are Osteoclasts derived from
monocytes, which are derived from monocyte precursors in the bone marrow
What is ARF
Activation-resorption-reversal-formation
cycle occurs at adult remodeling sites and during development
Where and when does ARF occur
at adult remodeling sites and during development
where does PTH bind
Receptors on the osteoblast
PTH stimulates osteoblasts to synthesize ___ and ___
M-CSF and RANKL
M-CSF is released by who
The osteoblast
Where does M-CSF bind
to the M-CSF receptor on the monocyte
After binding of M-CSF to the M-CSF receptor on the monocyte it is now a ______ and expresses ____
Macrophage, RANK
when does the macrophage become multinucleated and immature osteoclast
after RANK binds to RANKL
Who secretes osteoprotegerin
Osteoblasts
What is the function of osteoprotegerin
binds to RANKL with greater affinity than RANK
inhibits maturation of osteoclasts
Parathyroid blocks the synthesis of what
Osteoprotegerin
A non-functional osteoclast uncouples form the osteoblast and becomes a ______ _______
a functional osteoclast
What is the function of Calcitonin
Acts to reduce bone resorption
___ is secreted by exocytosis from the osteoclast and degrades the bone organic matrix
Cathepsin K
What forms the sealing zone of an osteoclast
Osteopontin, actin filaments, and Integrins
