Cartilage and Bone Flashcards
What are the functions of cartilage?
Supports soft tissues
Formation and growth of long bones
Role in joints
What are the components of cartilage?
Cells: Chondroblasts (active in forming ECM) appear elongated…. Chondrocytes (embedded in cartilage matrix within lacunae)
Fibers (collagens, elastin)
Ground substance (water, proteoglycans, GAGs)
What are some qualities of cartilage?
avascular
solid, firm, but also pliable
What are the three types of cartilage?
Hyaline
Elastic
Fibrous
What do chondrocytes in isogenous groups have?
A clonal relationship, arising from one cell via mitosis
Study these pictures of the three types of cartilage.
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What type of cartilage is this? Describe its features and where it is found.
Hyaline cartilage
Most abundant type of cartilage
Matrix is ‘glassy’
Type II Collagen (not seen with LM)
Surrounded by Perichondrium (outer fibrous and inner chondrogenic layers)
Chondrocytes in isogenous groups
Found: Nasal septum
Larynx, Tracheal rings, Bronchi
Costal cartilages
Articular cartilage of joints
What are the two layers of the perichondrium? Which layer performs appositional growth?
Outer fibrous layer of DICT, has stem cells and fibroblasts
Inner chrondrogenic layer… contains chondroblasts.. appositional growth
Describe appositional growth of hyaline cartilage
Mitosis of stem cells makes chondroblasts, these make new matrix at the periphery of the hyaline cartilage
What are the different regions of the hylaine cartilage?
Territorial - surround lacunae darker staining
Inteterritorial - majority of space between lacunae, lighter staining
Describe the process of interstitial growth.
Chrondrocyte divides by mitosis
Two chondroblasts in lacuna
New matrix produces
Cartilage grows internally
What structure of the body is this a picture of?
Hyaline cartilage and other tissues of the trachea
What type of hyaline cartilage is found as the darker red border of the bone adjacent to the joint space here?
Articular cartilage
What type of cartilage is shown in this picture? What are the similarities and differences to hylaine cartilage? Where can this be found?
Elastic cartilage
Similar to Hyaline cartilage: Does have Perichondrium, Chondrocytes in isogenous groups, Type II Collagen fibers (not seen with LM)
Different: Elastic fibers are abundant
Found: External ear
Eustachian tube
Epiglottis
What type of cartilage is in the right part of this picture? What are some defining features?
Fibrocartilage (Fibrous cartilage)
Distinct chondrocyte lacunae have ’fried egg’ appearance
Abundant Type I collagen fibers (seen) as well as the Type II collagen fibers
(Type I are easy to see)
No perichondrium
What are some functions, components, and qualities of bone?
Functions:
Support soft tissues
Attachment sites
Protects internal organs
Stores and releases minerals (Ca2+ & PO42-)
Contains bone marrow
Components:
Cells (Osteoblasts, Osteocytes, Osteoclasts)
Compact (Cortical) & Spongy (Cancellous) types
Collagen fibers
Qualities:
Calcified (Hydroxyapatite) gives hardness
Organic component (Collagen) gives tensile strength
Good blood supply
Study this bone structure diagram, note these structures:
Compact bone
Osteons
Haversian canal
Concentric lamellae
Lacunae
Osteocytes
Canaliculi
Volkmann’s canal
Circumferential lamellae
Periosteum
Sharpey’s fibers
Cancellous (spongy) bone
Trabeculae
Endosteum
Marrow cavity
What is this a picture of?
Cross section of a shaft of a long bone (decalcified).
Note these things:
Skeletal muscle
Periosteum
Compact bone
Spongy bone trabecula
Bone marrow in Medullary cavity
What are the two layers of the periosteum?
Outer fibrous layer (DICT)
Inner cellular layer (osteogenic layer) where osteoprogenitor cells turn into osteoblasts
YOu can also see outer circumferential lamellae in this image
What is the difference between the periosteum and the endosteum?
Endosteum is one layer and much thinner
Has oseoprogenitor cells like periosteum though
What are the 3 bone cells we should know and some basic functions?
Osteoblasts - immature bone cells that secrete osteiod matrix that eventually calcifies into bone matrix, found on the surface of forming bone
Osteocytes - the cells tht are embedded in the calcified bone matrix
Osteoclasts - LARGE MULTINUCLEATE CELLS, resorb bone, found in shallow depression on surface of trabeculae (howships lacunae)
Ob = Osteoblast
Oc = Osteocyte
Ot = Osteoid
P = Periosteum
What can be seen in this picture?
Ob (and asterisk) = Osteoblast
Ocl = Osteoclast
Ot = Osteoid
Arrowheads = Howship’s lacunae
What are some structures to note in this picture of compact bone?
Osteon
Haversian (Central) canal
Concentric lamellae
Lacuna with Osteocyte
Interstitial lamellae
Inner circumferential lamellae
Marrow cavity
What is a main difference between spongy and compact bone?
Spongy does have osteons, but they have trabeculae/spicules - thin plates of bone that extend into the marrow (medullary) cavity.
What is this a picture of? What can be identified here?
Ground Bone
Haversian canal
Volkmann’s canal
Canaliculi
Concentric lamellae
Lacunae
What type of bone is seen in this picture? What are some key features and functions of it?
Woven (fibrous/primary) bone
Newly formed bone made after fractures
Much more cellular than mature bone, no lamellar organization, collagen less organized
More weak and more flexible than lamellar bone
Osteoblasts and osteoclasts work to make this into mture secondary bone.
Describe the different parts of intramembraneous ossification
A) Development of ossification center:
- Begins with richly vascularized mesenchymal cells
- Mesenchymal cells à Osteoblasts
- At this cluster, Osteoblasts secrete organic matrix
- Cells become surrounded by the matrix
B) Calcification:
- Secretion of matrix stops
- Cells are now called Osteocytes (inside lacunae).
- Cytoplasmic processes extend into canaliculi
in all directions
- Within days, calcium salts are deposited and
extracellular matrix hardens
C) Formation of trabeculae:
- As the bony ECM develops it forms into trabeculae.
- Trabeculae fuse to form spongy bone around a network of blood vessels.
- CT associated with blood vessels in the trabeculae become red bone marrow
D) Development of periosteum:
- Mesenchymal cells at periphery of bone
condense to become periosteum.
- Thin layer of compact bone replaces surface of spongy bone, but inside stays spongy
- Spongy bone in center is named diploe.
Describe endochondral ossification (cartilage template replaced by bone)
A) Hyaline cartilage model:
- Mesenchymal cells develop into chondroblasts
- Chondroblasts form the hyaline cartilage model
B) Vascularization and primary ossification center:
- Vascularization of the diaphysis perichondrium results in chondrogenic cells becoming osteogenic, giving a subperiosteal bone collar (1)
- Chondrocytes in center of cartilage hypertrophy (3) and lacunae
become confluent. Primary ossification center is located in diaphysis
C) Secondary ossification centers:
- Subperiosteal bone collar increases in size
- Osteoclasts form a marrow cavity (5) within diaphysis
- Secondary ossification centers (7) begin in epiphyses
D & E) Epiphyseal plate develops:
- Elongation of bone occurs at epiphyseal plate (8)
- Vascular periosteum (11) covers the diaphysis
- Hyaline cartilage that covers the epiphyses
becomes articular cartilage
Note the different cartilage zones at the epiphyseal plate in this picture.
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Do bones undergo growth in width (appositional growth)? Describe the process if so.
1) Ridges in periosteum create a groove for periosteal blood vessel
2) Periosteal ridges fuse, forming an endosteum-lined tunnel (new central canal)
3) Osteoblasts in endosteum build new concentric lamellae (new osteon)
4) Osteoblasts in periosteum build new circumferential lamellae
What type of ossification takes place in the bones of the cranium mostly? What about the bones of the base of the skull, ethmoid, sphenoid, and temporal bones?
Cranium and face = intramembraneous
Base of skull, ethmoid, sphenoid, and temporal = endochondral
