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.
Characteristics of white adipose tissue?
Large cells, single fat globule in each. Nucleus pushed to one side by fat globule.
Histological appearance of white adipose tissue?
Appear white and empty as fat is extracted during processing. Nucleus pushed to one side.
Features of brown adipose tissue?
- each cell contains many fat globules
- found across shoulders in adults, down the back in newborns
- important in neonatal thermoregulation as breakdown of tissue generates heat
Constituents of cartilage?
- chondroblasts and chondrocytes
- extracellular matrix comprises glycosaminoglycans (e.g. hyaluronic acid) and proteoglycans (condroitin sulfate and keratan glycan)
- extracellular fibres (collagen and elastin)
Does cartilage contain blood vessels?
No, it is avascular.
What does hyaline cartilage comprise?
Where is it found?
Chondrocytes in lacunae (cavities) surrounded by a glassy matrix. No visible fibres. Perichondrium consists of fibroblasts and collagen.
Found in synovial joints.
What does elastic cartilage comprise?
Where is it found?
Chondrocytes in matrix which contains visible elastic fibres. Perichondrium consists of fibroblasts and collagen.
Found in the pinna (outer ear) and epiglottis.
What does fibrocartilage comprise?
Where is it found?
Chondrocytes in a matrix containing visible collagen fibres.
Perichondrium consists of fibroblasts and collagen.
Found in the annulus fibrosus (circular exterior of intervertebral discs, surrounding the nucleus pulposus). Also found in the pubic symphysis.
What is synovium, and what does it comprise?
What are the 2 types of synovial cells?
Lining of inside of joint capsule. Consists of 1-4 layers of synovial cells of variable shapes (squamous to cuboidal). Richly vascular and highly innervated.
Type A cells - phagocytes
Type B cells - rich in rough ER
Where is visceral (smooth) muscle found?
- arterial wall
- intestinal wall
- airways of lungs
- reproductive and urinary tracts
Where is voluntary (skeletal) muscle found)?
- skeletal muscles
- larynx
- diaphragm
Where is cardiac muscle found?
- heart
- base of great vessels
3 examples of contractile cells (other than muscle)?
Where are they found?
Pericytes - around the outside of capillaries.
Myo-fibroblasts and myo-epithelial cells - found in and around ducts.
Features of smooth muscle?
- involuntary
- fusiform cells
- central nucleus
- no striations or branching
- cytoplasm stained pink by eosin
