Flashcards in Lecture 13 Bone and Cartilage Deck (84):
True of False:
The skeletal system in all vertebrates begins as cartilage.
True, the skeletal system in all vertebrates does begin as cartilage.
What are the two different cell types that make up cartilage?
1) Chondroblasts (cartilage-forming cells)
2) chondrocytes (cartilage-maintenance cells)
What are the 3 major types of cartilage?
1) Hyaline Cartilage
2) Elastic Cartilage
What two components make up the extracellular matrix in cartilage?
1) Collage fibers
*mostly type II collagen (type I in fibrocartilage)
2) Amorphous ground substance
Name a few of the 6 functions that cartilage has?
2) Resists Distortion
3) Absorbs shock in joints
4) Reduces friction in movable joints
5) Necessary for endochondral bone growth
6) Involved in bone fracture repair
What do chondrocytes do?
Chondrocytes maintain the cartilage matrix.
What is the primary function of chondroblasts?
Chondroblasts lay down cartilage matrix and become chondrocytes.
What is a lacunae, and which two cell types would you find there?
A lacunae is a pocket within the cartilage matrix where the chondrocytes and chondroblasts are found.
*Lacunae means "little lake"
Since cartilage is avascular, how does cartilage get nutrients and oxygen?
Nutrients and oxygen are derived from blood vessels that surround the cartilage and must diffuse through the matrix to the cells.
A patient presents to you in the clinic 2 months after a cartilage tear and is upset with the slow recovery and assure you they have attended all of their physical therapy sessions. What characteristic of cartilage would you tell them about to explain the slow recovery?
That cartilage is avascular, thus, slow recovery is expected. You could also include how cartilage gets it nutrients into the matrix from blood vessels.
What are the two layers that make up the perichondrium?
*Outer fibrous layer:
*Inner chondrogenic layer:
>gives rise to chondroblasts, which become chondrocytes
>the condrocytes is involved in the production of the collagen and proteoglycans in the matrix. Chondrocytes also secrete chondronectin.
What makes up an isogenous group? What is the isogenous groups a result from?
* 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.
Which matrix (territorial or inter-territorial) surrounds each condrocyte?
True or False:
The inter-territorial matrix surrounds the territorial matrix.
Fill in the Blank:
_____matrix has a high glycoaminoglycan content and a low collagen content.
Fill in the Blank:
_____matrix has a low glycoaminoglycan content and a high collagen content.
What 3 sulfate containing compounds are components of the cartilage matrix?
True of False:
Glycosaminoglycans are not a component of the cartilage matrix.
False, glycosaminoglycans are a component of the cartilage matrix.
Which sulfer-less containing component is found in the cartilage matrix?
Hyaluronan (hyaluronic acid)
What is the most abundant form of collagen found in the cartilage matrix? What about in fibrocatilage, is it the same type of collagen?
Collagen type II is the most abundant, except for in fibrocartilage, which is made up of predominately type I collagen.
What is the most common type of cartilage found in the body and what type of collagen fibers does it contain?
Hyaline Cartilage and Type II Collagen
What are the two growth patterns that hyaline cartilage undergoes?
Give examples of where hyaline cartilage is found within the body.
External Auditory Meatus
Fetal Long Bones
Articular Ends of Bones
Chondroitin sulfate, type I collagen fibers, and proteoglycans are the 3 most abundant components found in the matrix of hyaline cartilage?
What are the two types of perichondrium found in hyaline cartilage?
Fibrous Perichondrium (source of fibroblasts)
Chondrogenic Perichondrium (source of chondroblasts and osteoprogenitor cells)
Give some examples of where elastic cartilage would be found.
Auricle (pinna) of the ear
Which 2 major cartilage types are surrounded by a perichondrium and which one is not?
Hyaline and Elastic cartilage are surrounded by a perichondrium.
Fibrocartilage is not surrounded by a perichondrium.
What gives elastic cartilage its yellow color?
The elastic fibers
Where is fibrocartilage typically found?
* intervertebral discs
* insertion of some tendons and ligaments
* closely associated with dense connective tissue or hyaline cartilage
What are the small cavities called in the extracellular matrix that chondrocytes occupy?
True or False:
Interstitial growth of cartilage is very active during endochondral ossification.
What are the 3 classifications of bone that are determined by matrix arrangement?
* Woven Bone
>occurs during bone development and bone repair
* Compact Bone
>also called lamellar bone
>also called trabecular or cancellous bone
Which 2 major components make up the matrix of bone?
1. An organic component referred to as osteoid.
2. An inorganic component referred to as hydroxyapatite which makes up 35 to 65 percent of the matrix.
What type of growth and cartilage model increases the length of bones?
Increase in bone length occurs through appositional growth of a hyaline cartilage model.
True or False:
Bone is highly vascular and thus is not found in close proximity to capillaries.
Bone is highly vascular and is found in close proximity to capillaries.
What makes up an osteon (or Haversian System)?
An osteon consists of a concentric (Haversian) lamellae which incircle a central blood vessel (and associated nerves) forming an osteon, orHaversian system.
How are osteocytes connected to each other and the Haversian canal? Also, what are they located in?
Osteocytes are found between the lamellae located in lacunae and are connected to each other and the Haversian Canal via canaliculi.
Which canal runs perpendicular to the Haversian canals and connect the Haversian canals to each other and to the surface of the bone?
What does trabecular (spongy) bone do in long bones and flat bones?
Has a 3D lattice of branching, bony spicules intertwined to form trabeculae surrounding the bone marrow spaces in the long bones and flat bones.
True or False:
The outer layer of the periosteum contains osteoprogenitor cells?
False, the inner layer contains osteoprogenitor cells.
In which layer of bone is blood vessels found?
The outer layer of the periosteum.
True or False:
Sharpey's fibers are collagen fibers derived from the inner layer of the periosteum, projecting into the outer circumferential lamellar system.
Sharpey's fibers are collagen fibers derived from the outer layer of the periosteum, projecting into the outer circumferential lamellar system.
What type of junction is located at the contact ports of osteocyte processes?
What are the 2 main functions of the osteoblast?
1) synthesize the organic matrix or bone, the osteoid.
2) control the mineralization of the bone matrix
Is bone growth achieved through appositional growth or interstitial growth?
What ectoenzyme (cell surface protein) hydrolyzes monophophate esters at high pH?
When does alkaline phosphatase stop function and disappear?
When the osteoblast ceases protein synthesis and becomes embedded in a mineralized bone matrix as an osteocyte.
What cell is osteoblasts derived from?
What cell are osteocytes derived from?
Derived from the monocyte lineage, which, in turn, is derived from the monocyte precursors in bone marrow.
Osteoblasts turn into osteocytes.
What are osteoblasts characterized by?
Where are osteoprogenitor cells found, besides the inner layer of the periosteum?
In the adult they are found in the inner layer of the periosteum, in the endosteum, and lining vascular canals of compact bone.
What are osteoprogenitor cells derived from?
Derived from mesenchyme of the embryonic somite (sclerotome) and possess mitotic potential.
What regulates the expression of osteocalcin in osteoblast cells? Also, what protein does osteocalcin have a high binding affinity for?
Vitamin D3 regulates expression of osteocalcin
Osteocalcin has high binding affinity for hydroxyapatite
What insulin-like growth factor stimulates the growth of long bones at the epiphyseal plate, and what hormone stimulates the upregulation of this insulin-like growth factor?
IGF-1 stimulates growth of long bones and it is upregulated by growth hormones that act on heptatocytes that produce the IGF-1.
What are the 2 major proteins products of an osteoblast?
1) Type 1 Collagen
2) Several Noncollagenous Proteins
What is RANKL and where is it located?
The receptor for the ligand RANK, which activates nuclear factor kappa B (RANK) -- present in osteoclast precursor cells.
What does osteopontin do?
Mediates the formation of the sealing zone.
What does bone sialoprotein do?
Mediates binding of osteoblasts to the extracellular matrix through integrins.
What is ARF?
ARF (activation-resorption-reversal-formation) cycle occurs at adult remodeling sites and during development.
*continually breaking down old bone and laying down new bone.
What hormone is the primary regulator of bone turnover?
Parathyroid Hormone (PTH)
What impact does low PTH levels have on the activation of osteoblasts?
Low PTH levels stimulate osteoblasts to form bone.
What role does high levels of PTH have on osteoblasts?
High PTH levels stimulate osteoblasts to release osteoclast-differentiation factors.
Besides stimulating osteoblast activity, what other mechanisms does PTH stimulate?
PTH stimulates the differentiation of monocyte precursors to form osteoclasts.
It also stimulates the formation of ruffled borders on osteoclasts.
A patient presents in your clinic with complaints of bone pain and tenderness with a remakable history of bone fractures of the arm. Lab results show elevated PTH levels and image studies show eroded bone and fibrosis of the humoris. What pathological condition is this patient most likely presenting with?
What does calcitonin do?
Calcitonin acts to reduce bone resorption, which is released by osteoblasts.
What 5 cell types can be derived from pluripotent mesenchymal cell?
What two non-collagenous proteins do osteoblast express when stimulated by parathyroid hormone (PTH)?
M-CSF and RANKL
What are the two essential recruiters for osteoclastogenesis that are up-regulated by parathyroid hormone?
M-CSF and RANKL
What binding of M-CSF ligand to the M-CSF receptor induces the expression of what?
RANK (transmembrane receptor for activation of nuclear factor kappaB
The binding of which ligand from the osteoblast to which receptor on a macrophage commits the cell to osteoclastogenesis, thus, becoming a multinucleated osteoclast precursor?
RANKL to RANK
RANKL-stimulated osteoclastogenesis is inhibited by what osteoblast-derived RANKL decoy protein?
(osteoprotegerin blocks RANKL binding to its receptor RANK)
The appearance of which two things marks that the maturation of osteoclasts is complete?
The Sealing Zone and the Ruffled Border
True or False:
Osteoclasts are multinucleated cells and contain abundant mitochondria and acidified vesicles.
What anion is exchanged for bicarbonate in the osteoclast?
What does the bicarbonate-chloride exchanger ensures in the osteoclast?
The bicarbonate-chloride exchanger ensures the maintenance of cytoplasmic electroneutrality.
How does the protons generated by carbonic anhydrase II get into the Howship's lacuna so that an acidic environment (pH 4.5) for solubilizing mineralized bone can be created, and maintained?
H+ ATPase Pump
What protein is releases into Howship's lacuna to degrade the exposed organic matrix (collagen and noncollagenous proteins) following solubilization of minerals by acidification?
What marks the start of bone degradation by an osteoclast?
Bone degradation starts when the alpha5beta3 integrin-F-actin-osteopontin complex organizes the sealing zone resulting in the isolation of the resorption space from the extracellular space.
Name the 3 places where osteoprogenitor cells are found?
1) inner portion of periosteum
3) lining vascular canals of compact bone
What two cell types do osteoprogenitor cells give rise to ?
2) bone lining cells
What characteristic of osteoblasts is not found in osteocytes?
Which of the following is not a characteristic of fibrocartilage?
A)Type II Collagen
B) Not surrounded by a perichondrium
C) Found in intervertebral discs
D) Increased collagens in the matrix
A - type II collagen
Which of the following is not part of a Haversian system?
D) Volkmann Canal
A - periosteum