(1) Anatomy and Histology of the Periodontium - periodontal ligament (ground substance, cells, nerve and blood supply) Flashcards
What secretes the ground substance?
fibroblasts
What is the role of the fibroblasts?
cells responsible for forming the collagen for collagen fibres
What are the components of the ground substance?
- Hyaluronate glycosaminoglycans.
- Proteoglycans
- Glycoproteins
What are the proteoglycans comprising the ground substance?
1) Proteodermatan sulphate
2) PG1 (contains hybrids of chondroitin sulphate dermatan sulphate).
What are the glycoproteins which comprise the glycoproteins?
1) fibronectin
2) tenascin
What is the role of the ground substance in the periodontal ligament?
maintain pressure and function of the PL
Name the 6 types of cell in the periodontal ligament
- Fibroblasts
- Cementoblasts.
- Osteoblasts
- Osteoclasts and cementoclasts.
- Epithelial cells
- Immune cells
What is the role of fibroblasts in the PL?
Form fibres
Responsible for the regeneration of the periodontal ligament.
Role in adaptive responses to mechanical loading.
What is the shape of the fibroblasts?
vary
don’t always see the spindle shape
prominent nucleoli
Are fibroblasts active or inactive?
active
lots of synthesising organelles
Fibroblasts produce collagen, what else do they do with regard to collagen?
Collagen degradation (fibroblasts are also fibroclastic).
Apart from collagen, what other substances do fibroblasts secrete secrete?
- matrix metalloproteinases
- tissue inhibitors
- metalloproteinases.
What is the role of collagen?
help maintain the structural framework of tissues.
What regulates collagen production from fibroblasts?
Collagenase production is regulated by exposure of cytokines.
Where do cementoblasts line?
the outer surface of the cementum
Are cementoblasts active?
Yes, but produce cementum at a very slow pace
What is formed at a higher rate, acellular or cellular cementum?
cellular
Where are osteoblasts located?
line the alveolar bone
line the tooth socket
What is the role of osteoblasts?
form bone
protein synthesising organelles
prominent where there is active bone formation
active protein formation
What do osteoblasts look like when they are active/inactive?
active = basal round nucleus
inactive = flat
What type of section is shown?
decalcified (can see cells)
Name structures A-D and what are the black and white arrows pointing to?
Decalcified section.
A) Alveolar bone.
B) Periodontal ligament.
C) acellular cementum.
D) Dentine.
White arrows point to osteocytes.
Black arrows point to osteoclasts in Howship’s lacunae.
What do osteoclasts and cementoclasts arise from?
blood macrophages
Are osteoclasts and cementoclasts small mononuclear or giant multinuclear?
they can be both
What is the brush border of cemento and osteoclasts?
striated part of the cell that is adjacent to bone, they represent microvilli.
What is in the vesicles of osteo and cementoclasts?
acid phosphatase
Where are Giant multinucleated osteoclasts found?
Howship’s lacunae in bone.
What is the role of osteoclasts?
reabsorb/ breakdown cementum
What are the epithelial cells rests of malassez?
remnants of the structures that formed the root of the tooth
they don’t regrade completely after tooth has formed
Are the epithelial cells rests of malassez harmful?
No
find them within the periodontal ligament
What is the basal lamina?
extracellular structures found closely apposed to the plasma membrane on the basal surface of epithelial and endothelial cells and surround muscle and fat tissues.
What is the structure of epithelial cell rests of Malassez?
closely packed cuboidal cells
Why are epithelial cell rests of the Malassez important?
If there is an inflammation of some sort and there are inflammatory molecules such as cytokines and growth factors
They can be induced to grow and cause cyst formation
Which cells can cause cyst formation?
epithelial cell rests of the Malassez
What cells are the arrows pointing to here?
epithelial cell rests of the Malassez
What are immune cells in the periodontal ligament?
Macrophages
Mast cells
Eosinophils
What supplies blood to the periodontal ligament? (arteries)
Superior and inferior alveolar arteries.
What is the difference between the Superior and inferior alveolar arteries?
superior = maxillary bone
inferior = mandibular bone
How do the inferior and superior alveolar arteries supply the PDL?
Arteries perforating the alveolar bone.
Through the neurovascular bundle entering the apical region of the pulp.
Where are the blood vessels located in the periodontal ligament?
Major vessels between principal fibres.
Where are the capillary plexus found in the PDL?
Capillary plexus around teeth.
Do veins accompany the arteries?
NO
What are fenestrations?
an arterial anatomic variant where a segment of a single vessel divides into at least two channels, each comprising endothelial and muscular layers (they may share the adventitia) that coalesce to a single lumen along its more distal course.
Why are fenestrations important in supplying the PL?
They allow immune cells migrate into the periodontal ligament when needed
Where would you find intra-alveolar venous networks?
prominent around the apex of the alveolus.
What do the blue, purple and green arrow point to?
blue = blood vessel
purple = endothelial cells
green = fenestration
Where does the nerve supply of the periodontal ligament come from?
comes through the alveolar bone
or through the neurovascular bundle which comes through the apex of the root, which divides into the pulp and the periodontal ligament
What types of nerve fibres supply the PL?
sensory
autonomic
What do the sensory nerve fibres of the PL allow?
nociception
mechanoreception
What do the autonomic nerve fibres control in the PL?
BLOOD VESSELS
Where do the nerve fibres enter the PL?
apical region
others enter through the alveolar wall
