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NJDS: Histology - Joints

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Question:
What is the definition of joints?
Answer:
The regions of skeleton where bones articulate, sometimes allows movement between bones and facilitate growth of bones
Question:
What is the definition of a synarthrosis joint?
Answer:
A type of joint characterized by limited or no movement between opposing bones
Question:
What are the 3 types of synarthrosis joints?
Answer:
1. Synostosis
2. Synchondrosis
3. Syndesmosis
Question:
What is a synostosis joint?
Answer:
- bones joined with bone
- does not allow movement to take place
- stablizes parts of skeleton after cessation of bone
Question:
What is an example of a synostosis joint?
Answer:
Cranial bones
Question:
What is a synchondrosis joint?
Answer:
- bones connected by hyaline cartilage
- allow little movement
- pertmits bone growth and expansion by endochondral ossification
Question:
What are 2 examples of a synchondrosis joint?
Answer:
1. epiphyseal plates
2. union of first rib at sternum
Question:
What is a syndesmosis joint?
Answer:
- bones that are far apart united by a ligament composed of dense CT
- allows limited movement
- functions as shock absorbers and sites of appositional bone growth
Question:
What is an example of syndesmosis joints?
Answer:
The union between the distal tibia and fibula
Question:
What is an amphiarthrosis joint?
Answer:
- a type of joint found where fibrocartilage is the interosseous medium
- capable of slight movement
Question:
What are 2 examples of amphiarthrosis joints?
Answer:
1. intervertebral joints
2. pubic symphysis
Question:
What is a diarthrosis joint (synovial joint)?
Answer:
- a type of joint usually found between long bones
- permits wide range of movements
Question:
The diarthroidal joint is organized into 3 articular structures. What are they?
Answer:
1. Articular capsule
2. Articular cavity
3. Articular cartilage
Question:
The bones of a diarthroidal joint are linked by ligaments and an outer capsule that are composed of 2 layers. What are they?
Answer:
1. Fibrous Layer
2. Synovial membrane (synovium)
Question:
Describe the Fibrous Layer of a diarthroidal joint.
Answer:
- an outer layer made of dense CT continuous with periosteum
- contains blood vessels and nerves
Question:
Describe the synovial membrane (synovium) of the diarthroidal joint.
Answer:
- an inner layer lined by 1-3 layers of synovial cells (synovocytes)
- function is to produce and resorb synovial fluid and to remove material shed into the articular cavity
Question:
Describe the structure of synovial membrane (synovium) of the diarthroidal joint.
Answer:
- a loose sheet of vascularized and innervated CT facing the articular cavity and arranged in fold and villi
- does not line the articular cartilage
Question:
Describe the cells type of the synovial membrane (synovium) of the diarthroidal joint.
Answer:
1. Type A (macrophage-like cells) - light staining phagocytic cells
2. Type B (fibroblast-like) cells - dark staining cells that secrete hyaluronic acid and glycoprotein lubricant in the synovial fluid
Question:
What are the bones of a diarthroidal joint surfaced with?
Answer:
articular cartilage
Question:
The articular cartilage of the diarthroidal joint is what type of cartilage?
Answer:
hyaline cartilage
Question:
The articular cartilage of the diarthroidal joint is characterized in part by the absence of what?
Answer:
Perichondrium
Question:
Describe how the collagen fibers of the diarthroidal joint are arranged.
Answer:
- the collagen fibers of the articular cartilage form wide arches
- the collagen fibers are perpendicular to the surface of the bone
- they are parallel to the articular surface when near the articular surface
Question:
Desrcibe what is stacked near the osseous surface of the articular cartilage of the diarthroidal joint.
Answer:
chondrocytes - found near the articular surface and are solitary and flat in shape
Question:
What makes the articular cartilage of the diarthroidal joint so resilient?
Answer:
The cartilage is an efficient absorber of mechanical pressures
Question:
What is the articular cartilage of the diarthroidal joint consist of?
Answer:
- type II collagen
- proteoglycans
- 8o% water
Question:
What do the proteoglycans of the articular cartilage of the diarthroidal joint contain and what does this enable them to do?
Answer:
- these molecules contain large amounts of water, enabling them to function as a biomechanical spring
Question:
Describe how the proteoglycan molecules of the articular cartilage works as a spring.
Answer:
- when pressure is applied, water is forced out of the matrix into the synovial fluid
- reciprocal elctrostatic repulsion of negatively charged carboxyl and sulfate groups in the GAG molecule occurs
- this separates the GAG branches and creates spaces to be occupied by water
- when pressure is released, water is attracted back into these spaces.
Question:
Water movements brought about by use of the diarthroidal joint is responsible for what?
Answer:
This is responsible for the resiliency of the cartilage and for its nutrition
Question:
What are the 3 zones in the articular cartilage?
Answer:
1. superficial zone
2. middle (transitional) zone
3. deep zone
Question:
Describe the superficial zone of the articular cartilage.
Answer:
- chondrocytes are small and flattened
- collagen fibers arranged parallel to the surface
Question:
Describe the middle (transitional) zone of the articular cartilage.
Answer:
- chondrocytes arranged in columns
- collagen fibers begin to change their orientation from horizontal to vertical
Question:
Describe the deep zone of the articular cartilage.
Answer:
- contains calcified cartilage with small chondrocytes
- located adjacent to the subchondral bone
- collagen fibers run perpindicular to the surface
Question:
Describe the intra-articular menisci (discs).
Answer:
- cushions of fibrocartilage or dense CT
- may be free or transverse the joint
Question:
Describe the 2 classifications of the articular cartilage.
Answer:
- simple: two articulating surfaces (ex. knee joint)
- compound: three or more articulating surfaces (ex. TMJ)
Question:
The TMJ is a type of what kind of joint?
Answer:
This is a type of gliding-hinge synovial joint found in mammals
Question:
Describe the articulation of the TMJ
Answer:
This is the articulation of the mandibular condyle with the temporal bone, by way of the glenoid fossa
Question:
Describe the mandibular condyles of the TMJ.
Answer:
These are ovoid structures with long axes oriented medially
Question:
Identify the 5 layers of the TMJ.
Answer:
The layers of this structure are
1. dense fibrous CT
2. proliferative zone
3. fibrocartilage (hyaline during growth period)
4. calcified cartilage
5. sub-articular bone
Question:
Describe the proliferative zone of the TMJ.
Answer:
this zone consists of a layer of cells acting as a replicating pool for underlying cartilage
Question:
Describe the layers of the articular eminence of the TMJ from superficial to deep.
Answer:
1. dense CT (fibrous layer)
2. proliferative layer
3. fibrocartilage
4. bone
Question:
What is the glenoid fossa?
Answer:
- This is the concave depression in the squamous portion of the temporal bone.
- Covered by thin film fibrous layer (periosteum)
Question:
What is the capsule of the TMJ?
Answer:
This is the fibrous membrane that surrounds the joint and incorporates the articular eminence.
Question:
What is the capsule of the TMJ composed of?
Answer:
This is composed of dense fibrous CT.
Question:
Describe the attachments of the TMJ capsule.
Answer:
1. the upper half forms a loose envelope with a posterior attachment at the squamotympatic fissure
2. an anterior attachment at the articular eminence
3. a lateral attachment at the glenoid fossa
4. attached medially, laterally, and posteriorly at the articular disk
5. firmly attached to the neck of the mandibular condyle
Question:
What is the function of the articular disk of the TMJ?
Answer:
This structure functions as an articular surface and divides the TMJ into 2 distinct compartments.
Question:
Describe the composition, innervation, and vascularization of the TMJ articular disk.
Answer:
This structure is:
1. composed of fibrous connective tissue
2. it is avascular and aneural centrally
3. it is vascular and innervated at its periphery
Question:
What can be said about the attachment of the bioconcavity structure in the TMJ articular disk?
Answer:
This structure is attached to the medial and lateral poles of the condyle.
Question:
Describe the upper lamella of the TMJ anterior articular disk.
Answer:
This region runs forward and fuses with the capsule and periosteum of the anterio slope of the articular eminence.
Question:
Describe the lower lamella of the TMJ anterior articular disk.
Answer:
This region is attached to the anterior surface of the condylar neck.
Question:
What inserts between the lamellae of the TMJ articular disk?
Answer:
The superior head of the lateral ptyerygoid is found here.
Question:
Describe the upper lamella of the TMJ posterior articular disk.
Answer:
This region is composed of fibrous and elastic CT and inserts into the squamotympatic fissure (as part of the capsule)
Question:
Describe the lower lamella of the TMJ posterior articular disk.
Answer:
This region merges with the periosteum of the condylar neck
Question:
What 2 things are found in the zone between the posterior lamallae?
Answer:
1. retrodiscal tissue
2. comprised of loose vascular CT
Question:
Name and describe the lateral portion of the TMJ capsule.
Answer:
This portion is thickened and fanshaped and is known as the temporomandibular ligament.
Question:
Describe how the temporomadibular ligament is placed within the TMJ.
Answer:
This structure runs in an oblique course posteriorly and inferiorly from the later aspect of the articular eminence to the posterior part of the condylar neck.
Question:
Identify the muscle of the TMJ.
Answer:
The muscle of this structure is called the lateral pterygoid.

Image Question:
Can you name all the structures in the TMJ?
A - mandibular condyle
B - glenoid fossa
D/C - articular disc
E - articular eminence
H - region of squamotympanic fissure

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