Wk3 Structure & Function of Connective Tissue Flashcards
What is a fibroblast?
Provides structural and metabolic support to other cells
Which fibres are needed?
Elastin, fibrous collagen
What does ground substance do?
Acts as a barrier
What are cells of connective tissue?
- Fibroblast
- Plasma cells (clock face) - antibodies
- Apidocyte = nucleus on outer line, rest washed away (glittering appearance)
- Macrophage
- Mast cell
- Lymphocyte
- Neutrophil
- Eosinophils (tomato with glasses)
- Fibrocyte (inactive state of fibroblast when finished depositing ground substance and fibres
What are connective tissue fibres synthesised by?
Fibroblasts
What are the different types of collagen?
- Abundantly distributed in body
- Seen in cartilage
- Reticular
- Basement membrane
Summary of collagen fibres properties
- Thick
- Tough
- Do not branch
- Bundles
- Tensile strength
Summary of reticular fibres (reticulin)
- Type III collagen fibres
- Thin
- Delicate framework of organs like liver, spleen, lymph nodes etc.
Summary of elastic fibres (elastin) properties
- Thin
- Branching
- Allows stretching
What is ground substance made up of?
- Hyaluronic acid backbone (GAG)
- Proteoglycan branches made up of: link protein, core protein and glycosaminoglycans (GAG)
Are ground substances hydrophilic or phobic?
Hydrophilic (traps water)
What are basic types of connective tissue?
- Loose connective tissue
- Dense connective tissue
- Adipose tissue
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Type 1 collagen fibre = Bone, Skin, Tendon
Type 2 = Cartilage
Type 3 = Reticulin and Blood vessels
Type 4 = Basement membrane
What is the function of mast cells and where are they derived from?
- Bone marrow
- Release bioactive substances (histamine, heparin etc.) that mediate local inflammatory responses
What type of blood cell are macrophages derived from?
Monocyte precursor
What do macrophages and lymphocytes do?
Protection against specific viral and bacterial pathogens
What are reticular fibres and what is their function?
- Supportive stroma
- Scaffoldings
What do reticular cells do?
Fibroblasts secreting reticular fibres
What is white adipose tissue?
- Subcutaneous (insulator)
- Unilocular
- Stores fat for energy release
- Signet ring appearance on H&E
What is brown adipose tissue?
- Scapula
- Multilocular
- Thermogenesis
- Rich in mitochondria and capillaries
- Many small fat droplets - soap bubble appearance
What is tendonitis?
Inflammation of tendons
- Tendons have a very poor blood supply, so don’t heal well
What are elastic fibres composed of and describe the ultrastructural appearance of elastic fibres?
- Elastin and scaffolding provided by fibrillar (a structural glycoprotein) both secreted by fibroblasts
- Allow stretch and recoil of structures
- Prevalent in lungs, skin, bladder and walls of elastic arteries e.g. aorta
- Marfan’s syndrome - results from mutation in fibrillar gene - therefore, less resistance to stretch in tissues which normally have a lot of elastic fibres - risk of aortic aneurysms
Fibres + Ground substance =
Extracellular matrix
Give an overview of collagen fibres
- Flexible yet have a higher tensile strength than steel
- If you stretch collagen fibres over 3% of their original length they break
Give an overview of elastin fibres
- Provide connective tissue with the ability to stretch and recoil back to its original shape
- Tissues with a high elastic content in their matrix e.g. the cartilage of the ear will be more elastic than those with little (ligaments) or no elastin (tendons)
Give an overview of ground substance
- Fibres are embedded in an amorphous ground substance which is the component of connective tissue that occupies the space between the fibres and the cells
- It is a viscous clear substance that feels very slippery because it is highly hydrated
- Ground substance is composed of proteoglycans - highly hydrophobic molecules that trap water within the matrix
Give an overview of cells
- In dense connective tissues, only one cell cycle is present - the cell that produces the fibre and ground substance
- In loose and dense connective tissue this cell is the fibroblast
What is loose connective tissue?
- Surrounds blood vessels within tissues and underlies the basement membrane of epithelia - it is the site of metabolic exchange between the capillary and the tissue it supplies
- Composed largely of the hydrated ground substance with relatively few fibres (both collagen and elastin) and fibroblasts
- Provides ideal environment for the exchange of nutrients and waste products between tissues and the blood
- Therefore populated by macrophages, lymphocytes and plasma cells which act as mobile residents, and other white blood cells can be rapidly recruited from local blood vessels when required
- Apidocytes
What is dense connective tissue?
- Provides tough physical support and protection
- E.g. ligaments, tendons and in dermis of skin
- Comprised largely of fibres where collagen fibres are arranged in a very orderly fashion
- Dense irregular connective tissue - less ordered array of collagen fibres although same density
What is metabolic exchange?
Responding to environmental stimuli using metabolic exchange controlled via homeostasis
What do tendons do?
Connect muscles to bones
What do ligaments do?
Connect bones to other bones
what is an oedema?
- caused by excess fluid becoming trapped in body tissues
- accumulates in extracellular vascular spaces like ankles feet and legs
- increases diffusion distance for oxygen and other nutrients
how do you diagnose an oedema?
- pressure applied, if fluid there will be a gap
what is Marfan’s syndrome?
- A defect in the gene that tells the body how to make fibrilin-1, which is a major constituent of microfibrils which form the frame for elastic fibres - artery wall breaks down and causes an aneurism
