Connective Tissue Flashcards
what are connective tissue cells derived from?
- undifferentiated mesenchymal cells
- can derive from haematopoetic stem cell line
describe the structure of connective tissue cells
- scaffold of extracellular fibres
- jelly-like matrix
what do connective tissue cells contain?
- collagen
- elastin
what makes connective tissues amorphous?
- high molecular weight
- strongly hydrophilic
- negatively charged
what cells are in connective tissues?
- fibroblasts
- adipose cells
what are the visible fibres in connective tissues?
- collagen
- elastin
- reticulin
what does the ground substance (hydrophilic jelly) of connective tissues contain?
- proteoglycans
- glycosaminoglycans
- invisible fibres (e.g. laminin, fibronectin)
what does the ground substance (hydrophilic jelly) of connective tissues contain?
- proteoglycans
- glycosaminoglycans
- invisible fibres (e.g. laminin, fibronectin)
what is fibrous connective tissue?
contains large numbers of fibres such as collagen, elastin or reticulin
what is fatty connective tissue?
contains mainly fat cells with intervening blood vessels (particularly capillaries)
what is hard connective tissue?
various forms of bone
what is soft connective tissue?
- flexible and gel-like
- interspersed between major tissue elements
what are the types of soft connective tissue?
- fibrous
- fatty
what are the types of fibrous connective tissue?
- loose
- dense
what are the types of fatty connective tissue?
- white
- brown
what are the types of hard connective tissue?
- cartilage
- bone
describe the structure of collagen
- individual collagen fibrils consisting of overlapping linear strands of tropocollagen
what is tropocollagen?
3 linear polypeptide chains wound together in alpha helix
what synthesises tropocollagen?
fibroblasts
where is type I collagen?
- skin
- tendons
- ligaments
where is type II collagen?
cartilage
where is type III collagen?
- liver
- bone marrow
- spleen
- kidney
- lymph nodes
where is type IV collagen?
basement membranes
where is type V collagen?
placenta
does collagen stain with H&E?
yes
how is collagen identified histologically?
- variable thickness and length
- often run in bundles
- no nuclei
what is reticulin?
type III collagen
what is the function of reticulin?
supporting scaffold in organs
how is reticulin identified histologically?
- forms branched fibres instead of linear
- not visible on H&E (silver)
what is the histological difference between loose and dense connective tissue?
dense:
- closer spaced and thicker collagen ribres
- may be irregular
what are the histological similarities between loose and dense connective tissue?
- fibroblasts
- unstained ground substance between fibroblasts
what does elastic tissue contain?
- fine fibres
- sheets of elastin
what is elastin produced by?
fibroblasts
does elastin stain on H&E?
yes
- pink
what is the histological difference between elastin and muscle cells/collagen?
- stains more deeply
- can produce glassy appearance
what is the histological difference between white and brown adipose tissue?
white: single fat globule in each cell
brown: multiple globules of fat in each cell
what is the functional difference between white and brown adipose tissue?
white: insulation, shock absorber
brown: generates heat (thermoregulation)
where is brown adipose tissue found?
across shoulders and down back of newborns
describe the structure of cartilage
- dense glycosaminoglycan-rich matrix containing variable amounts of collagen and elastic tissue
- surrounded by perichondrium
what is perichondrium?
fibrocollaginous capsule
what are the properties of cartilage?
- flexible
- compressible
- hard-wearing
where are chondroblasts found and what do they mature into?
- matrix of cartilage
- chondrocytes
what does the perichondrium contain?
undifferentiated progenitor cells capable of differentiating into chondroblasts
what is found in the extracellular matrix of cartilage?
- glycosaminoglycans
- proteoglycans
give 2 examples of extracellular fibres
- collagen
- elastin
does cartilage have its own blood supply?
no
what are the main types of cartilage?
- hyaline
- elastic
- fibrous
where is hyaline cartilage found?
- synovial joints
- articular surfaces
- ‘rings’ of trachea
- cartilages of larynx
does hyaline cartilage stain on H&E?
very poorly
where is elastic cartilage found?
- pinna of the ear
- epiglottis
what is the structure of elastic cartilage?
irregularly arranged visible fibres of elastin in matrix
what is the structure of hyaline cartilage?
- GAG-rich matrix that appears glassy
- fine fibrils of collagen and elastin
is elastic cartilage visible on H&E?
yes
- more visible under silver stain (highlights elastic fibres)
where is fibrous cartilage found?
- annulus fibrosus
- pubic symphysis
- inter-vertebral discs
what is the structure of fibrous cartilage?
visible collagen fibres (often in distinct bands) in matrix
what is synovium?
connective tissue lining the inside of a synovial joint capsule
how many layers of synovial cells is typically in synovium?
1-4
what are type A synovial cells?
phagocytes
what are type B synovial cells?
- rich in RER
- secrete synovial fluid
what shape are synovial cells?
variable
- squamous to cuboidal
what are the types of muscle?
- visceral (smooth)
- voluntary (skeletal)
- cardiac
where is visceral muscle found?
- arterial walls
- intestinal walls
- airways of lungs
where is skeletal muscle found?
- skeletal muscles
- larynx
- diaphragm
where is cardiac muscle found?
- heart
- base of great vessels
what are other contractile cells?
- pericytes
- myo-fibroblasts
- myo-epithelial cells
where are pericytes found?
alongside some small blood vessels (e.g. veins, venules)
what is the function of myo-fibroblasts?
involved in scar formation
what is the function of myo-epithelial cells?
- assist expression of milk during lactation
