Connective Tissue Flashcards
What are the functions of connective tissue?
1) Binding and supporting (such as holding skin, gut, lungs)
2) Protecting (such as bone protecting vital organs, eg. fat acting as shock absorber)
3) Insulating
4) Storing reserve fuels and cells (bone marrow and fat tissue)
5) Transporting substances within the body (blood and interstitium)
6) Separation of tissues (fascia and tendons/cartilage)
What is interstitium?
Space between tissues and organs of the body
What are the two types of connective tissue proper?
- Loose connective tissue
- Dense connective tissue
What is loose connective tissue also known as?
Also known as areolar tissue
What is dense connective tissue also known as?
Also known as ‘fibrous’ or collagenous tissue
What are the two types of dense connective tissue?
Irregular
- Fibres running in different directions
Regular
- Fibres running in parallel to each other
What are the types of adipocytes?
- Unilocular
- Multilocular
What adipocytes are found in loose connective tissue?
White adipocytes (unilocular)
- Single lipid droplet, with nucleus cytoplasm and organelles all squeezed to one side of the cell
- Acts as padding and shock absorber, insulation and energy reserve
What are multilocular adipocytes?
Brown adipocytes
- Few of these in an adult
- Multiple small lipid droplets with the nucleus, cytoplasm and organelles squeezed to the centre of the cell.
- Provide insulation and energy reserve
What are the differences between white and brown fat tissue?
White adipose tissue:
- Single lipid droplet
- Normal number of mitochondria
- Single peripheral nucleus
- In adults, lipid breakdown is slow and heat is only generated after shivering reflex
Brown adipose tissue:
- Multiple lipid droplets
- Increased number of mitachondria
- Single central nucleus
- In neonates and young children, lipid breakdown is accelerated, oxidative phosphorylation is uncoupled to generate heat
What is collagen
The most common protein in the body
How many types of collagen are there?
4
- Type I
- Type II
- Type III
- Type IV
What is Type I Collagen?
- The most widely distributed type (90%)
- Fibrils aggregate into fibres and fibre bundles
eg. tendons, capsules of organs and skin dermis
What is Type II Collagen?
Fibrils do not form fibres
eg. present in hyaline and elastic cartilage
What is Type III collagen?
Fibrils form fibres around muscle and nerve cells and within lymphatic tissues and lymphatic organs (eg. spleen) and in tendons
- Called reticulin
What is Type IV collagen?
Unique form present in basement membranes
What is extracellular matrix?
A term used to describe a complex extracellular structural network that consists of ground substances and fibres
What fibres are found in connective tissue?
Collagen
- Flexible with high tensile strength
Reticular (absent in areolar tissue)/reticulin
- Provide a supporting framework/sponge
Elastin
- Allows tissues to recoil after stretch or distension
How is collagen produced?
- Fibroblasts secrete procollagen that is converted to collagen molecules outside the cell
- The collagen molecules are then aggregated to form collagen fibrils
- In some tissues, fibrils group together to form collagen fibres to give strength (bone, tendons, ligaments)
What is required for procollagen production?
Vitamin C
- Required for intracellular production of procollagen, where it hydroxylates proline and lysine
What happens with a vitamin C deficiency?
-Disrupts collagen formation leading to scurvy
What happens in scurvy?
- The thin collagen fibrils aggregate in some areas to form thicker collagen fibres
What are the symptoms and signs of scurvy?
- Gum disease and tooth loss
- Bruising of the skin and hair loss
- Bleeding
- Poor wound healing
- Weakness and fatigue
- Impaired bone development in the young
What is Marfan’s syndrome?
- Autosomal dominant disorder
- Expression of the fibrillin 1 gene is affected so elastic tissue is abnormal
What are signs and symptoms of Marfan’s syndrome?
- Abnormally tall and large wingspan
- Arachnodactyly (long fingers and toes)
- Frequent joint dislocation
- At risk of catastrophic aortic rupture
What is the primary component of elastic fibres?
Elastin
- Elastin infolds and is surrounded by microfibrils of fibrillin
Where are elastin fibres found in the body?
- Dermis
- Artery walls
- Lungs
- Sites bearing elastic cartilage
What is Osteogenesis Imperfecta?
‘Brittle Bone Disease’
What causes Osteogenesis Imperfecta?
- Mostly autosomal dominant
- Due to mutated collagen fibres that do not ‘knit together’
