Connective Tissue Flashcards
Where is the origin of connective tissue cells
Mainly from undifferentiated mesenchymal cells
Haematopoietic stem cell line
What are the constituents of connective tissue
Cellular component
- fibroblasts/cytes
- adipose tissue
Extracellular components
- visible fibres
- ground substance (hydrophilic jelly) - doesn’t stain with H&E appears white spaces
What are the types of connective tissues
- Fibrous (depending on collagen fibres within them)
- Loose
- Dense - Hard
- Cartilage
- Bone - Fatty
- White (most prevalent of the fats)
- Brown (role in thermogenesis)
What is collagen
Secreted by fibroblasts as tropocollagen - triple helix of peptides
Fibres assembled extra-cellularly
How many types of collagen are there
More than 20
What is type 1 collagen prevalent in
Skin and bone
What is type 2 collagen prevalent in
Cartilage
What is type 3 (reticulin) collagen prevalent in
Liver, bone marrow, spleen
What is type 4 collagen prevalent in
Basement membrane
What is type 5 collagen prevalent in
Placenta
What colour do collagen fibres stain with H&E
Extracellular - pink
Variable thickness and length - often run in bundles
What is the significant difference between collagen fibres and muscle fibres
Muscle fibres are intracellular (nuclear lies within them)
What does loose connective tissue comprise of
Widely spaced thin collagen fibres
Fibroblasts/fibrocytes
Unstained ground substances
What does dense connective tissue comprise of
Closely spaced thick collagen fibres
Fibroblasts/fibrocytes
Unstained ground substance (less abundant than in loose connective tissue)
May be irregular or regular (running parallel to each other)
What is the role of type 3 collagen - reticulin
Fibrillar collagen
Forms a supporting scaffold in many organs
- Bone marrow
- Liver/kidney
- Lymph node
- Spleen
What stain must be used to see reticulin
Silver stain
Not visible on H&E
What is elastin (elastic tissue)
Contains fine fibres and sheets of elastin
Elastin fibres may be branched
Produced by fibroblasts
What colour is elastin stained on H&E
Pink
What is white adipose (fatty) tissue
Large cells with single fat globule in each cell
Usually appear empty (white) in conventional slides as fat is extracted during process
What is brown adipose (fatty) tissue
Cells with many globules of fat
Found across shoulders and down back of newborn
Important in neonatal thermo-regulation (generate heat to breakdown)
What are the constituents of cartilage
Hard connective tissue
2 cell types
- chondroblasts
- chondrocytes
Set in abundant extracellular matrix
Extracellular fibres
Avascular - gets blood from blood vessels either side of cartilage
What are the three types of cartilage
Hyaline cartilage
What is hyaline cartilage
Found in synovial joints
Chondrocytes in lacunae surrounded by a glassy amorphous matrix
No visible fibres
Perichondrium - fibroblasts and collagen
What is elastic cartilage
Visible elastic fibres
Perichondrium - fibroblasts and collagen
Chondrocytes trapped within matrix
Elastic fibres easily visible on H&E but clear on silver stain
Where is elastic cartilage found
Pinna
Epiglottis
What is fibrocartilage
Visible collagen fibres in matrix
Perichondrium - fibroblasts and collagen
Trapped chondrocytes
Where is fibrocartilage found
Annulus fibrosus
Pubic symphysis
What is synovium
Lines the inside of the joint capsule
1-4 layers of synovial fluid
Two types of cells -
Type A - phagocytes
Type B - rich in rER - secrete synovial fluid
Variable shapes - squamous to cuboidal
Richly vascular, highly innervated
What are the three categories of muscle
Visceral (smooth) muscle
Voluntary (skeletal) muscle
Cardiac muscle
(other)
What are visceral (smooth) muscle
Arterial wall
Wall of intestine
Airways of lungs
What are voluntary (skeletal) muscle
Skeletal muscle
Larynx
Diaphragm
What are cardiac muscle
Heart
Base of great vessels
What fall under other muscle types
Pericytes
Myo-fibroblasts
Myo-epithelial cells
What is smooth muscle
Involuntary muscle
Fusiform cells
Central nucleus
Non striations
Non-branching
Describe the features of the dermis underneath the epidermis
Thick layer of dense irregular connective tissue
Consists of long fibres of collagen that run in many directions to form a mat-like fibrous scalp
Fibres stain dark pink
Have fibroblasts with dark blue nuclei lying alongside them
What are tendons composed of
Thick ribbons of parallel collagen fibres
Between lie the fibroblasts which synthesis them
Describe the composition of the penis
Contains mixture of loose and dense irregular fibrous connective tissue
Describe the wall of arteries
Most contain a large amount of smooth muscle
Those close to the heart the muscle replaced by concentric sheets of elastic tissue
Sheets stain pink with eosin
