BL L11 Flashcards
Define connective tissue
Tissue that supports, protects, gives structure to other tissues and organs in the body.
Number of connective tissue
6
Name all types of connective tissue
Loose connective tissue
ibrous connective tissue (dense)
Adipose tissue
Cartilage
Bone
Blood
What is ground substance?
‘where they sit’
(taken card out)
(taken card out)
Name some fibres in connective tissue
Collagen
Reticular fibre
Elastin
Name the ground substance in connective tissue
Proteoglycans (glucosaminoglycans, e.g. hyaluronic acid)
What are ground substance
Ground substance + fibres
General - connective tissue function
- Binding and supporting (such as holding skin, gut, lungs, etc. together)
- Protecting (such as bone protecting vital organs) {fat acting as a ‘shock-absorber’}
- Insulating (fat underlying skin) {bone marrow holding warm blood}
- Storing fuel reserve and cells (bone marrow and fat tissue)
- Transporting substances (blood and interstitium) 6. Separation of tissues (fascia and tendons/cartilage)
What is the interstitium?
Space between tissues and organs of the body
Intro - Loose connective tissue (it’s other name, list where you find it, how specialised is it?)
Also known as areolar tissue (Areola = ‘little space’)
Already seen where it is found:
- Lamina propria in mucosal membranes
- Lots in the basal lamina
- It fills up any SPACES between different organs, e.g. small space between liver and pancrease will fill up with areolar tissue
Intro - Dense connective tissue (other name, types)
Also known as ‘fibrous’ or collagenous tissue
• Two types
- Irregular Fibres running in different directions
- Regular Fibres running parallel to each other
More depth - Loose connective tissue structure (cell types it contains, fibres, ground substance)
- Contains multiple cell types
Fibroblast, macrophages, other white blood cells and mast cells, adipocytes - Contains two main fibres
Collagen and elastin - Gel-like ground substance
Proteoglycans, hyaluronic acid, etc
More depth - Loose connective tissue functions
- Holds vessels that supply fluids
- Permits cell migration
- Involved in inflammation pathways
- Acts as packaging around organs
- Generally hold everything in place
- Cushions and stabilises organs
Fibroblast (location, function and what they look like)
e.g. found in loose and dense connective tissue
MAKE FIBRES AND GROUND SUBSTANCES
- Fibroblasts synthesise and secrete the fibres that lie within the ground substance (extracellular matrix)
- They are very important in the wound healing process and are the cells primarily responsible for the formation of scar tissue
What are myofibroblasts?
Myofibroblasts are modified fibroblasts that contain actin and myosin. They are responsible for wound contraction when tissue loss has occurred (when myofibroblasts contract they pull the two edges of the wound together, this is because you’ve ‘lost tissue’ when you’ve cut yourself).
Macrophages (where are they found? what are they derived from? what is their role?)
e.g. found in aerolar tissue
Derived: Macrophages are derived from blood monocytes, they move into loose connective tissue, especially when there is local inflammation
Role: Macrophages are phagocytic and can degrade foreign organisms and cell debris Macrophages are ‘professional antigen presenting cells’ (i.e. they can present foreign material to the T and B lymphocytes of the immune system)
Mast cells (where are they found? What do they contain? Role? Link to allergies?)
Mast cells look like basophils but are not derived from them.
Contain:
Mast cell cytoplasm contains abundant granules:
• Histamine (increases blood vessel wall permeability)
• Heparin (an anticoagulant)
• Cytokines that attract eosinophils and neutrophils
Location:
• Found in areolar connective tissue near blood vessels
• Absent from CNS as avoid damaging effects of oedema (the histamine would allow the blood and water in leading to oedema, cerebral oedema = very dangerous)
Allergies:
Mast cells become coated with IgE (IgE molecule specifically bind to allergens). When an allergen cross-links these surface-bound IgE molecules, the contents of the granules are all rapidly released from the cell
What is histamine?
Increases blood vessel wall permeability, they cause epithelial cells to seperate creating a gap where fluid moves in (this is where you can get odema - swelling - at the site of imflammation)
What is heparin?
Anti-coagulent, this stops the blood from clotting at this particular point, this is because due to the effect of histamine there are lots of cells and blood (highly viscose) at this place
Adipocytes (unilocular): Discription, Function
Also present in areolar cells
- Most of the adipocytes in loose connective tissue look white or yellow and so called white adipocytes
- A single enormous lipid droplet, with the nucleus, cytoplasm and organelles all squeezed to one side of the cell
- Function: padding and shock absorber, insulation and energy reserve
Adipoctyes (mulilocular): Discription, Function
- Brown adipocytes
- Multiple small lipid droplets, with the nucleus, cytoplasm and organelles all squeezed to the centre of the cell
- Function: Provides insulation and energy reserve
Compare white adipose and brown adipose tissue (number of droplets, number of mitochondria, location of nucleus, which group of people are they found?)
Which fibres are in loose connective tissue?
- Collagen
Multiple types – type 1 most common and most important - Reticulin
A different type of collagen fibre – most common in lymphatic system - Elastin
Made of hydrophobic amino acids – most common in aorta, lungs, skin - Fibrillin
Glycoprotein essential for the construction of elastin fibres – wherever elastin can be found
What type of macromolucle is collagen?
Protein
Describe the different types of collagen
(Need to learn these)
What do collagen fibres, elastic fibres etc look like?
Proteoglycan structure
Skin - loose and IRREGULAR dense connective tissue (visualise this)
Dense IRREGULAR tissue - visualise this
These bundles are going in all directions = irregular
(bundles - collagen fibres -> fibrils -> fibrils package into bundles)
Visualise dense irregular connective tissue again…
Note - elastins are going in all direction directions, this allows for lateral movement of the dermis
Visualise dense REGULAR connective tissue
Regular - all bundles lie in a parallel densely pakced formation
Fibroblast secrete collagen so have to be there too!
Myotendinous junction (What is this? Briefly how do they interact?)
- Skeletal muscle fibres connecting with tendon collagen bundles at myotendinous junctions provides tremendous physiological strength
- The collagen passes from the tendon to the muscle fibres were it interacts with the collagen fibres coating the muscle fibres
- Cross-links between these fibres results in mechanical strength
How is collagen arranged in ligaments and tendons?
The collagen bundles are densely packed in a parallel arrangement, but undulate and are arranged in fascicles. These are separated by loose connective tissue and ground substance.
Fasicle arrangement - see diagram
Summary of irregular and regular DENSE connective tissue (what does it contain, direction of stress, examples)
Which specific step in collagen synthesis requires vitamin C?
Hydroxylation of Pro and Lys
Elastin fibres
- Elastin fibres have two main components elastin and fibrillin
- Elastin is the primary component of elastic fibres, but itself enfolds and is surrounded by microfibrils called fibrillin
- Elastin rely on fibrillin to work. Pulling elastic fibres cause them to straighten out (see diagram), form cross-links. These cross-links hold the elastin fibres in this position until the force is removed, when it will then spring back.
- Desmosine and isodesmosine are involved in the cross-linking. If enzymes destroy these cross-links, it will drestroy the rebound capacity of this fibre
- If desmosine and isodesmosine are found in the urine = elastin fibres are breaking down (they shouldn’t be!)
Visualise what elastin fibre looks like…
