Wk 2: Connective Tissue Flashcards
4 Functions of CT
- Structural support
- Medium for exchange of nutrients & waste products
- Defence, protection & repair of the body
- Fat storage
What are the 3 functions of the Extracellular Matrix
- Provides tissue w strength to resist tensile & compressive forces
- Directs cells to proper positions within tissue & holds cells in place
- Regulates development, mitotic activity & survival of cells in a tissue
Composition of ECM
- Ground substance
- Protein fibres
(gel like ground substance w fibres embedded throughout)
The ground substance of ECM is made up of what 3 families of macromolecules
- Glycosaminoglycans (GAGs)
- Proteoglycans
- Cell adhesive glycoproteins (CAGs)
What are glycosaminoglycans (GAGs)
Polysaccharides, made of sugars including glycosamine
Function of proteoglycans in ground substance of ECM
- Bind to a long GAG forming proteoglycan aggregates.
- These make ECM firmer, more solid, resistant to compression.
Function of Cell Adhesive Glycoproteins (CAGs)
- Holds everything in place - adhere cell to cell and cells to surroundings
- Maintain normal tissue architecture
Function of collagen in CT
Provides tensile strength & elasticity
Type 1 collagen
- Main structural collagen
- Fibrous supporting tissue
- Skin (dermis), tendons, ligaments & bone
Type 2 collagen
- Hyaline cartilage
- Consists of fibrils in the cartilage ground substance
Type 3 Collagen
- Liver, bone marrow & lymphoid organs
- Forms reticular supporting mesh work, prominent in liver
Type 4 collagen
- Constituent of basement membranes
- Network mesh forming collagen
Type 7 collagen
- Anchoring fibrils
- These link ECM to basement membranes
What can be seen in histological analysis of collagen
Characteristic cross banding (due to polymerisation of the tropocollagen monomer)
What is the elasticity of a tissue due to
Due to the presence of elastic fibres in the ECM
What is the precursor monomer of elastin and what synthesises it
- The precursor monomer of elastin is tropoelastin
- Tropoelastin is synthesised by fibroblasts
What is tropoelastin polymerised by
Lysyl oxidase
Where in the body is elastin found (4)
- Lung
- Skin
- Urinary bladder
- Blood vessels
What is CT derived from (what precursor cells)
Mesenchyme
5 fixed cells in CT
- Fibroblasts
- Myofibroblasts
- Adipose cells
- Mast cells
- Macrophages
What are fixed cells
Cells that develop & remain in the CT where they carry out their function
7 transient cells in CT (& what are transient cells)
- Plasma cells
- Lymphocytes
- Neutrophils
- Eosinophils
- Basophils
- Monocytes
- Macrophages
* Transient cells originate in the bone marrow, circulate in the bloodstream and migrate into CT to perform function when given the signal
Funtion of active fibroblasts (3)
- Specialise in tissue repair
- Support wound healing
- Create new ECM
Function (1) of inactive fibroblasts
- Maintain structural integrity - synthesise ECM
Appearance of unilocular (white) adipocyte
- Large spherical cells
- Contain a single large lipid droplet that pushes the cytoplasm to the edge of the cell
- More abundant
Appearance of multilocular (brown) adipocytes
- Smaller & more polygonal
- Less abundant
- Contain several small lipid droplets
2 subdivisions of macrophages
- Phagocytes
- Antigen presenting cells
Function of macrophages
- Remove cellular debris
- Protect against foreign invaders
the 2 primary mediators in mast cells & their functions
- Histamine & heparin released by mast cells
- Function in the initiation of the inflammatory response
What is mast cell activation induced by
Foreign antigens - pollen, certain drugs
How is the inflammatory response initiated - detailed
First exposure to foreign antigen
* IgE antibody formation
* IgE antibodies bind to Fc receptors on mast cells, sensitising the mast cells
Subsequent exposure:
* Antigen binds to IgE
* Release of primary mediators from granules of mast cells
* Inflammatory response initiated
What are plasma cells derived from
B lymphocytes
Function of plasma cells
- Part of adaptive immune system
- Produce antibodies for specific antigens
(found in greatest numbers in areas of chronic inflammation & in areas where foreign substances or m/os have entered tissues)
What is loose (areolar) CT made of - cells & other substance
- Mainly ground substance
- Houses fibroblasts, adipocytes, immune cells
- Contains the 3 types of protein fibres - collagen, elastin, reticular
- Extensive blood supply
Where is loose (areolar) CT found
- it surrounds blood vessels, nerves, muscles, organs
- Separates skin from deeper structures
What is dense irregular CT made of
- Predominantly disorganised collagen bundles
- More fibres & fewer cells than loose CT
Function of dense irregular CT
- Strong
- Resists tension in movement
Where is dense irregular CT found (3)
High tension areas:
* Dermis of skin
* Surrounding organs & joints
* Sheaths of nerves
What is dense regular collagenous made of
- Predominantly organised into parallel collagen bundles
- Fibroblasts between collagen bundles
Where is dense regular collagenous CT found
- Constitutes tendons & ligaments that are subject to tension
What is dense regular elastic connective tissue made of
- Composed of parallel elastic fibres
- Randomly oriented collagen fibres
- Few fibroblasts scattered throughout
Where is dense regular elastic CT found (2)
In walls of organs that must stretch to perform function - large blood vessels & certain ligaments
WHat is reticular CT composed of
Reticular fibres produced by fibroblasts
What does reticular CT form & hence what can it support
- A fine network
- That can support small structures - blood & lymphatic vessels
Where can reticular CT be found
- Lymph nodes
- Spleen
(forms weblike nets trapping old & foreign cells) - Part of basement membrane that supports all epithelia
What is adipose CT made of
- Adipocytes
- Surrounding fibroblasts
- ECM
Function of adipose CT (4)
- Fat storage
- Insulation
- Shock absorption
- Protection
Where is adipose CT found
- Buttocks
- Breast
- Abdomen
