Practical 3 - Connective Tissues Flashcards
What cell do most connective tissue cells arise from?
Undifferentiated mesenchymal cell
What cells arise from undifferentiated mesenchymal cells?
- mast cells
- white & brown adipocytes
- fibroblasts, differentiate into fibrocytes
- chondroblasts, differentiate into chondrocytes
- osteoblasts, differentiate into osteocytes
Where else are connective tissue cells derived from?
Haematopoetic stem cell line
Which cells are derived from the haematopoetic stem cell line?
- monocytes
- macrophages
- lymphocytes
- mast cells
Constituents of connective tissue?
- cells
- visible fibres (collagen, elastin, reticulin)
- ground substance (hydrophilic jelly which appears as white space on H&E stained specimen) contains proteoglycans, glycosaminoglycans and invisible fibres (laminin, fibronectin)
Three types of connective tissues?
- fibrous
- hard
- fatty
2 types of fibrous connective tissue?
- loose
- dense
2 types of hard connective tissue?
- cartilage
- bone
How is collagen formed?
- fibroblasts secrete tropocollagen subunits
- tropocollagen subunits are assembled into collagen fibres extra-cellularly
How many types of collagen are there?
> 20 types
Where is type 1 collagen found?
Skin & bone
Where is type 2 collagen found?
Cartilage
Where is type 3 collagen found?
Liver, bone marrow, spleen.
Reticulin is type 3 collagen.
Where is type 4 collagen found?
Basement membranes
Where is type 5 collagen found?
Placenta
How do collagen fibres appear on H&E stains?
Extracellular fibres stained pink, often run in bundles.
What does loose connective tissue comprise?
- widely spaced thin collagen fibres
- fibroblasts/ fibrocytes
- ground substance
What does dense connective tissue comprise?
- closely spaced thick collagen fibres
- fibroblasts/fibrocytes
- ground substance
Example of irregular dense connective tissue?
Penile fascia
Example of regular dense connective tissue?
Tendon
Function of reticulin?
Where is reticulin found?
Can it be seen on H&E stain?
- forms a supporting scaffold in many organs
- bone marrow, liver, kidney, lymph node, spleen
- not visible on H&E stain, need silver stain
What does elastin comprise?
Fine fibres and sheets of elastin.
Fibres may be branched.
What produces elastin?
Fibroblasts
Histological appearance of elastin?
Stained pink by H&E, easily confused with smooth muscle.