Cartilage & Bone Flashcards
What is the General function of Cartilage?
Cartilage provides pliable support; Firm but flexible
What are the (3) subtypes of cartilage?
How are they distinguished biochemically?
Hyaline Cartilage: Collagen Type II
Elastic Cartilage: Collagen Type II + Elastin
Fibrocartilage: Collagen Type I
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What are the Specialized types of Hyaline Cartilage?
How can they be differentiated?
Articular cartilage: Hyaline cartilage that coats the ends of bones w/ synovial membrane
Costal Cartilage: Connects the ribs to the sternum to provide elasticity to the thoracic cavity
Articular cartilage lacks a Perichondrium layer, which is distinct from the Hyaline Cartilage
What is the function of the Perichondrium?
The Perichondrium is a sheath of dense irregular CT that surrounds cartilage.
Composed of 2 layers;
- Outer Fibrous Layer: Fibroblasts produce Collagen Type I
- Inner Chondrogenic Layer: Mesenchymal cells differentiate into Chondroblasts, intiate matrix production (Elastin & Type II Collagen) & become immature Chondrocytes
Function:
- Growth & Maintenance of Cartilage
- Vascular Support (Cartilage is Avascular)
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What are Chondrocytes?
Chondrocytes are cells within the lacunae inside cartilage that maintain the cartilage.
They can occur singularly or within clusters referred to as Isogenous Groups
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Describe the orientation of Hyaline cartilage
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Describe the Components of this image
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P: Pericondrium
C: Chondrocytes; Singular & isogenous groups
M: Matrix
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Thyroid cartilage falls under what type?
Thyroid cartilage is considered Hyaline Cartilage*
Describe the cartilage present in most joints.
Articular Cartilage (Hyaline): Hyaline cartilage coats the ends of bones & allows them to glide over each other with little friction
Synovial Membrane: Specialized CT that lines the inner surface of joint capsules
Secretes synovial fluid (egg white-like consistency)
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What are the characteristics of Articular Cartilage?
Articular Cartilage:
- Persists for life
- Lacks a Perichondrium; Repair is exclusively interstitial
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What type of cartilage is shown?
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Articular Cartilage
Evident by it’s smooth surface (top) and lack of perichondrium
Describe the condition of Osteoarthritis
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What type of cartilage is Costal Cartilage?
Costal cartilage falls under Hyaline Cartilage
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How does Elastic Cartilage compare to Hyaline Cartilage?
Elastic cartilage is extremely similar to Hyaline Cartilage.
Both have a perichondrium & chondrocytes in lacunae. The primary difference is the presence of Elastin fibers within the ECM
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What type of cartilage is this?
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This is Elastic Cartilage
Evident by presence of Elastin fibers in the ECM
Where is Elastic Cartilage located?
Elastic Cartilage is located in:
- Outer Ear, Eustachian Tube
- Epiglottis
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What are the components of this image?
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Epiglottis:
Elastic Cartilage surrounded by a Perichondrium
Additional: Adipose Tissue (White)
Where is Fibrocartilage located?
Fibrocartilage:
- Intervertebral Discs
- Some Joints:
- Pubic Symphysis
- Meniscus of the knee joint
- Osteotendinous Junctions (OTJ)
- Osteoligamentous Junctions (OLJ)
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What are the characteristics of Fibrocartilage?
This tissue is primarily fibrous tissue, located in areas that withstand a lot of force;
- Chondrocytes are rowed in lacunae
- No perichondrium
- Resembles a tendon microscopically
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What type of Cartilage is this?
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Fibrocartilage:
Evident by the lack of perichondrium & presence of lined-Chondrocytes
What types of Cartilages are present at the Knee joint?
Articular Cartilage (hyaline): Present on the end of the long bones
Fibrocartilage: Makes up the Meniscus of the knee
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Describe the condition known as Osteomyelitis
Osteomyelitis: Infection & inflammation of the Bone primarily caused by S. aureus
Symptoms:
- Fever
- Bone pain
- Swelling (painful) of the affected area
Xray shows a periosteal elevation indicating a subperiosteal abscess
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What must occur while preparing slides for bone?
Bone is too hard for routine sectioning:
- Specialized microtomes (ground sections) are used
- Bone matrix is decalcified prior to paraffin embedding
Describe the Organization of Bone layers
Periosteum–sheath of Dense irregular CT
- Attached via perforating fibers (Sharpey’sfibers)
- Cells: fibroblasts, MScs, osteoblasts
Bone
- Osteoblasts
- Organic ECM = osteoid(collagen I, GAGs, PGs, multi-adhesive gps)
- Progressive mineralization: calcium, phosphate (50% inorganic)
- Osteocytes
- Trapped in lacunae -maintain the bone
Endosteum
- Thin layer of CT that lines inside of bone
- MSCs, osteoblasts
- Osteoclasts(monocyte-macrophage lineage) –digest bone
Bone marrow
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What are the (2) types of bone?
Compact bone -cortex of most bones
- 80% of the mass
Cancellous (spongy) bone –inside long bones)
- Spaces filled with BM
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How does bone appear?
All adult bone (compact or cancellous) appears lamellar
- In sheets or concentrically wrapped around a central canal
- Osteocyte nuclei are trapped in lacunae between layers
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Describe what the Osteon is.
Columns of concentric lamellae around a central canal
Osteocytes in lacunae are between the lamellae
Haversian canal
- Blood vessels & nerves
- Communicate with the periosteum & BM
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What are canaliculi?
Canaliculi are channels linking Osteocytes
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Describe the components of bone remodeling & Repair
Balance of synthesis & degradation:
Synthesis: Osteoblasts
Degradation: Osteoclasts
- Bone resorption releases calcium
How are the Haversian canals formed?
Osteoclasts form a cone that cuts through bone, while bringing osteoblasts & blood vessels along for the ride
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What type of growth is responsible for Diameter?
New bone added beneath the periosteum
Concurrent with bone removal at the endosteum surface
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Describe bone formation of flat bones of the skull & short bones (i.e. Jaw)
Intramembranous ossification
- ECM & calcification forms directly in embryonic tissue
Describe the formation of Long bones during development
Endochondral Ossification:
- Deposition of bone matrix onto a pre-existing hyaline cartilage model
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Describe the signaling pathway for growth at the epiphyseal plate
Anterior Pituitary: Growth hormone (GH) release
GH stimulates chondrocytes in growth plate to secrete & respond to IGF-1
Describe the layers of the Epiphyseal Plate
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What structure is depicted here?
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Epiphyseal Plate
Describe the process of repairing a bone fracture
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Which of these defects are considered “better”?
Why?
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Full thickness defects induce hemorrhage formation
Stem cells trigger repair, resulting in Fibrocartilage
Describe the Metabolic function of Bones
Skeleton is the major Ca2+ reservoir (99%)
- Maintains plasma Ca2+ levels
Released from cancellous bone into interstitial fluid by osteoclasts
- Regulated by two hormones
- Parathyroid hormone -stimulates osteoclasts
- Calcitonin (thyroid) -inhibits osteoclasts
Describe the types of Musculoskeletal Insertions
- Muscle-Tendon-Bone
- Bone-Ligament-Bone
- Muscle-Bone
Describe the Myotendinous Junction
CT to CT
- Epimysium fibers merge with deep fascia and the tendon (may also include periosteum)
- May also merge with the periosteum, providing an attachment to bone
Muscle-CT
- Muscle fibers interdigitate with collagen fibers of the tendon
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Describe Bone insertions
Muscle fibers may attach to bone by merging with the periosteum
Tendons & ligaments have specialized interfaces that transmit tensile load from soft tissue to bone
- Entheses
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Describe the 2 types of Entheses
- Fibrous enthesis
- Typically occur over large surface areas
- Collagen fibers in the ligament/tendon merge with the periosteum
- Fibrocartilaginousenthesis
- Attach via a layer of fibrocartilage
- More common than fibrous insertions
- Prone to overuse injury -commonly encountered in orthopedics