12 - Connective and Adipose Tissue Flashcards
What are the different types of connective tissue?
- Loose connective tissue
- Fibrous connective tissue
- Adipose tissue
- Cartilage
- Bone
- Blood
What are the main three components of connective tissue?
- Cells - fibroblasts, adipocytes, reticular cells
- Fibres - collagen, elastin, reticular fibres
- Ground substance - proteoglycans (GAGs - e.g. hyaluronic acid)
What is extracellular matrix made up of?
Ground substance and fibres
What are the functions of connective tissue?
- Binding and supporting
- Protecting
- Insulating
- Storing reserve fuel and cells
- Transporting substances within the body
- Separation of tissues
What is loose connective tissue also known as?
Areolar tissue
Where is loose connective tissue found?
- In the lamina propria beneath mucosal membranes
- Abounds the basal lamina
- Around glands, capillaries, nerves and sinusoids
What is dense connective tissue also known as?
Fibrous or collagenous tissue
What are the two types of dense connective tissue and how do they differ?
- Irregular - fibres run in different directions
- Regular - fibres run parallel to each other
What cell types are found in loose connective tissue?
- Fibroblasts
- Macrophages
- Other lymphocytes and mast cells
- Adipocytes
What fibres are found in loose connective tissue?
The structure also contain cells and …….. …………
Collagen and elastin
ground substance
What are some functions of loose connective tissue?
- Holds vessels
- Permits cell migration
- Involved in inflammation
- Acts as packaging around organs
What do fibroblasts synthesise and secrete?
- Fibres (elastin and collagen)
- Ground substance (proteoglycans)
What are myofibroblasts?
- Modified fibroblasts that contain actin and myosin and can contract
- Responsible for wound contraction in tissue loss
When are macrophages found in the loose connective tissue?
During local inflammation
Macrophages are phagocytic and are antigen presenting cells
Mast cells contain granules in their cytoplasm, what is contained in these granules?
- Histamine (increases blood vessel permeability)
- Heparin (anticoagulant)
- Cytokines (attract eosinophils and neutrophils)
What do mast cells do?
Become coated with IgE molecules that bind allergens. Granules are released when allergens bind.
What is a unilocular adipocyte and what does it do?
- Cell of white adipose tissue
- Single lipid droplet with organelles squeezed to one side
- Padding/shock absorber, insulation and energy reserve
What is a multilocular adipocyte and what does it do?
- Cell of brown adipose tissue
- Multiple lipid droplets with organelles in the centre of the cell
- Provide insulation and energy reserve
Why is brown adipose tissue only usually found in neonates and young children?
- Lipid breakdown is accelerated in young children as oxidative phosphorylation is uncoupled to generate heat
- Doubles the calories generated
What are the different types of collagen? Where are they found?
Type I - fibres aggregate into bundles (tendons, capsules of organs, skin dermis)
Type II - Fibrils don’t form fibres (hyaline and elastic cartilage)
Type III - Fibrils form fibres around muscle, nerve and lymphatic cells. Known as reticulin.
Type IV - Unique to the basement membrane (epithelia)
What are the properties of:
- Collagen
- Reticulin
- Elastin
Collagen - flexible with high tensile strength
Reticulin - Supporting framework / sponge
Elastin - Allows tissues to recoil after stretch
What is ground substance made up of?
Proteoglycans
- Large molecules with a core protein to which glucosaminoglycans (GAGs) are bound
- GAGs attract water to form a hydrated gel
What is an example of a GAG?
Hyaluronic acid
Give an example of where irregular dense connective tissue is found and why it is significant?
Superficial layers of the dermis (skin)
- Allows skin to resist tearing forces in multiple directions
- Elastic fibres allow for stretch and restoration to the original shape
Give an example of where regular dense connective tissue is found and why it is significant?
Tendons
- Connect muscle to bone
- Collagen fibres run parallel in line with the tensile force exerted by the muscle
How do tendons join to muscles?
The myotendinous junction
Collagen passes from the tendon to the muscle fibres, where it cross-links with the collagen that coats the muscle fibres
What types of collagen are found in a tendon?
Type I - 70% Type III (reticulin) - 30%
What do ligaments do? What is the structure of a ligament?
Connect bone to bone
Dense collagen bundles in a parallel arrangement (same as tendons) but undulate and arranged in fascicles. Fascicles separated by loose connective tissue and ground substance.
What are the different types of fascia?
- Superficial
- Deep
- Visceral or parietal
What is the structure of fascia?
- Made of dense regular connective tissue (like tendons and ligaments)
- Fascia is flexible and able to resist great unidirectional tension forces
How are collagen fibres produced?
- Fibroblasts secrete procollagen that is converted to collagen outside the cell
- Aggregate to form collagen fibrils
- In some tissues, fibrils aggregate to form collagen fibres to provide further strength
Why is vitamin C essential to collagen production?
- Vitamin C used for production of procollagen intracellularly
- Hydroxylates proline and lysine
- Without vitamin C, collagen formation is disrupted (leads to scurvy)
What are some symptoms of scurvy?
- Gum disease
- Bruising of the skin
- Bleeding
- Poor wound healing
What is Marfan’s Syndrome?
- Autosomal dominant disorder - fibrillin 1 gene affected
- Abnormal elastic tissue
Sufferers exhibit the following symptoms:
- Abnormally tall
- Arachnodactyly (long and slender digits)
- Frequent dislocation
- Risk of aortic rupture
What is the structure of elastin fibres?
Primarily composed of elastin but is surrounded by microfibrils called fibrillin
Which layer of the blood vessel wall contains the elastic lamellae?
Tunica media
In blood vessels it is ……… …….. cells that produce elastin, collagen and matrix not fibroblasts.
Fibroblasts will only lay down …… ……..
smooth muscle
scar tissue
Elastin is only produced in …….. …………….. and cannot be replaced. Will only be replaced with scar tissue if damaged.
foetal development
What is osteogenesis imperfecta?
- ‘Brittle bone disease’
- Number of different genetic causes (most are AD)
- Due to mutated collaged that does not ‘knit together’
What are some symptoms of osteogenesis imperfecta?
- Weakened bones
- Short stature
- Blue sclera
- Hearing loss
- Hypermobility (loose joints)
- Poor development of teeth
