OCB02-2019 Development of salivary glands Flashcards
What is the histology staining of salivary glands done with? why?
Using Periodic- Acid Schiff staining because H&E cannot stain glycoproteins very well
What colour do acinar cells appear in histological stain?
Purple
What colour do duct cells appear in histological stain?
pink
What is the purpose of acinar cells?
produce saliva into the ducts
What is the purpose of ductal cells?
Modify the saliva
What do the parasympathetic and sympathetic nerves control with regards to saliva?
Control the flow rate and which proteins are secreted into the saliva
What saliva does the parasympathetic NS result in?
Large amounts of thin saliva
What saliva does the sympathetic NS result in?
Small amounts of thick saliva
Once secretory components have formed in acinar cells, where do they travel?
Into intercalated ducts which lead to striated ducts
What type of ducts are intercalated and striated ducts known as?
Intralobular ducts
What are the cells of the ducts connected by?
Tight junctions
What do blood vessels supply for the saliva?
The water content, but not proteins
Where do major salivary glands develop from?
Oral ectoderm
Where do minor salivary glands develop?
Oral ectoderm and endoderm
What are the 5 stages of salivary gland development?
Initial bud formation Pseudo-glandular Canalicular Terminal Bud Adult formation
Which stages of development are embryonic?
Initial bud formation
Pseudo-glandular
Canalicular
What stage of development is perinatal?
terminal bud formation
When does initial bud formation take place?
Initial 6 weeks of embryogenesis
What occurs during initial bud formation?
Thickening of the oral cavity ectoderm to form epithelial placode
Mesenchyme receives signals and it condenses as the placode expands
What occurs in the pseudo glandular stage?
Branching occurs, and there are long projections of epithelial cells with terminal ends
In the pseudo glandular phase, what promotes branching?
FGFs
In the pseudo glandular phase, what antagonises branching?
BMPs
What does mesenchyme control in the pseudo glandular phase?
It control influence on branching only and does not affect which salivary proteins are secreted
When does the canalicular stage occur?
10 weeks in utero
What occurs in the canalicular stage?
Apoptosis of central cells forms lumens
What does failure of the canalicular stage result in?
Cause retention cysts/ ranulas which are a collection of fluid/saliva that becomes trapped in the mucosa
When does terminal bud stage occur?
Around 16 weeks in utero
What cells form acini in the terminal bud stage?
Type 3 cells
What cells form striated ducts in the terminal bud stage?
type 1 cells
When does the adult formation stage occur?
36 weeks in humans
What occurs in the adult formation stage?
Development and integration of nerves
Nerves develop separately and attach to acini cells around birth
What does the maturation of salivary glands depend on?
The interaction with nerves
What proteins are present in neonates?
IgD
sIgA
Albumin
What does the salivary protein shift from and to?
IgD to sIgA
What defence builds in the first year?
Mucosal defence
What are the influences on salivary gland development in adults?
Tooth eruption/ weaning/ mastication: there are mechanoreceptors which become activated, there is increased neural input to glands which causes secretion
Puberty and menopause: hormones
Age: Salivary protein profile changes so amylase is found. More fibrosis and fat deposits through age but this does not impede function. The is no age-related decline in salivary flow, but medications can cause xerostomia
When does branching morphogenesis occur?
Pseudo-glandular stage
When do nerves connect into acinar cells?
Perinatal/ adult formation
From which tissue do myoepithelial cells develop?
Ectoderm
Is amylase an embryonic or adult salivary protein?
Adult
Which signalling molecule opposes FGF-signalling?
BMPs
