Session 5 Flashcards
Define the term ‘connective tissue’
A tissue that connects, supports, binds, or separates other tissues or organs, typically having relatively few cells embedded in an amorphous matrix, often with collagen or other fibres.
SIMPLER DEF:
- Connective tissue is a tissue made of cells, fibres and ground substance
State 6 functions of connective tissue and give examples of where this function is demonstarted
(Cite examples to explain connective tissue functions: e.g. cell/tissue binding and support, protection, fuel storage and transport of substances)
1) binding and supporting (such as holding skin, gut, lungs, bones, etc. together)
2) protecting (such as bone protecting vital organs) {fat acting as a ‘shock-absorber’}
3) insulating (fat underlying skin) {bone marrow holding warm blood}
4) storing reserve fuel and cells (bone marrow and fat tissue)
5) transporting substances within the body (blood and interstitium)
6) separation of tissues (fascia and tendons/cartilage)
Which 3 components make up connective tissue?
- Cells
- Fibres
- Ground substance
List the common cell types found in connective tissue
- Fibroblasts
- Macrophages
- Mast cells
- Adipocytes (unilocular)
- Adipocytes (multilocular)
DISCUSSION BOARD
Describe the functions of fibroblasts
- 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 and what do they do?
Myofibroblasts are modified fibroblasts that contain actin and myosin. They are responsible for wound contraction when tissue loss has occurred
What do fibroblasts, elastin fibres, collagen fibres and histiocyte macrophages and abundant Rough Endoplasmic Reticulum (RER) look like?
Describe the functions of Macrophages
- Macrophages are derived from blood monocytes
- They move into loose connective tissue, especially when there is local inflammation
- 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 lymphocytes of the immune system)
Describe the functions of mast cells
- Mast cells look like basophils but are not derived from them
- Mast cell cytoplasm contains abundant granules:
- Histamine (increases blood vessel wall permeability)
- Heparin (an anticoagulant)
- Cytokines that attract eosinophils and neutrophils
- Found in areolar connective tissue near blood vessels
- Absent from CNS (avoid damaging effects of oedema)
- Mast cells become coated with IgE, molecules which
specifically bind allergens - When an allergen cross-links these surface-bound IgE molecules, the contents of the granules are all rapidly released from the cell
Describe the functions of unilocular adipocytes
- Most of the adipocytes in loose connective tissue white to 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
Describe the functions of multilocular adipocytes
- Brown adipocytes
- Very few of these in the adult
- Multiple small lipid droplets, with the nucleus, cytoplasm and organelles all squeezed to the centre of the cell
- Function: Provides insulation and energy reserve
- In neonates: main method of generating heat (non-shivering thermogenesis)
What do unilocular adipocytes look like?
- Difficult to see details in standard H&E because xylene and toluene strip out the fats
- Nucleus displaced to periphery of each adipocyte
What do multilocular adipocytes look like?
- Multiple small lipid droplets, with the nucleus, cytoplasm and organelles all squeezed to the centre of the cell
Describe extracellular matrix (e.g. the constituents of ground substance and the collagen, reticular and elastic fibres that may lie within it)
- Ground substance + fibres = extracellular matrix
(The extracellular matrix is the complex extracellular structural network that consists of ground substance and fibres)
- Ground substance consists of:
Protein
Glycoprotein, specifically proteoglycans
Glycosaminoglycans (GAG’s) e.g. hyaluronic acid
Lipid
Water
- Fibres consist of:
Collagen
Elastin
Reticulin
Discuss the function of extracellular matrix (e.g. the constituents of ground substance and the collagen, reticular and elastic fibres that may lie within it)
Describe the functions of collagen, elastin and reticulin
Collagen - used to make connective tissue and connects other tissues and is a major component of bone, skin, muscles, tendons, and cartilage. Flexible with high tensile strength
Elastin - Allows tissues to recoil after stretch or distension
Reticulin - Provide a supporting framework/sponge
Describe the function of ground substance
Ground substance is active in the development, movement, and proliferation of tissues, as well as their metabolism. Additionally, cells use it for support, water storage, binding, and a medium for intercellular exchange (especially between blood cells and other types of cells).
What is the actual function of extracellular matrix?
The extracellular matrix helps cells to bind together and regulates a number of cellular functions, such as adhesion, migration, proliferation, and differentiation. It is formed by macromolecules, locally secreted by resident cells.
Describe the key details of ground substance (what the lecture slide says about it)
Explain the differences between loose and dense connective tissues, in terms of their cellular and extracellular components, relating these differences to tissue function
Check Lusuma set in deck
What is loose connective tissue also known as?
Areolar connective tissue (also adipose tissue)
Where is dense connective tissue usually found in the body?
Dense connective tissue occurs as dense regular connective tissue (e.g. tendons, ligaments, aponeuroses, etc.) or as dense irregular connective tissue (e.g. dermis, deep fascia, joint capsule, organ capsules, etc.)
Where is loose connective tissue usually found in the body?
Loose connective tissue (also known as areolar connective tissue) is widely distributed in the body as superficial fascia (fascia means ‘covering’) and as an investing fascia around nerves and blood vessels, and between skeletal muscles. it is also found under epithelial cell layers (e.g. lamina propria beneath mucosal membranes) and around glands, surrounds capillaries, nerves and sinusoids. It also abounds the basal lamina and is the Least specialised connective tissue in the adult.
Describe the functions of loose connective tissue.
- 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
Describe the structure of loose connective tissue.
- Contains multiple cell type ie Fibroblast, macrophages, other white blood cells and mast cells adipocytes
- Contains two main fibres - Collagenous and elastic (no reticular)
- Gel-like ground substance - containing Proteoglycans, hyaluronic acid, etc.DE
Histology of loose connective tissue
Classify different types of loose and dense connective tissue
DISCUSSION BOARD
Recognise the following connective tissues and fibres in photomicrographs, discuss their anatomical locations and salient histological features in relation to their function:
oDense connective tissue – irregular (e.g. dermis) and regular (e.g tendon)
oAreolar / Loose connective tissue
oMucoid connective tissue (e.g. in umbilical cord) oAdipose tissue
oFibres: elastic fibres (e.g. in lung), collagen fibres,
reticular fibres (e.g. in lymph node)
List the signs and symptoms 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
List the signs and symptoms of Marfan’s syndrome
- Abnormally tall
- Arachnodactyly
- Frequent joint dislocation
- Can be at risk of catastrophic aortic rupture (90% mortality rate - aortic aneurysm)
List the signs and symptoms of osteogenesis imperfecta.
- Weakened bones (fractures are common)
- Short stature (depends on type)
- Presence of blue sclera
- Hearing loss
- Hypermobility (loose joints) and flat or arched feet
- Poor teeth development
Briefly explain the causes, including the molecular mechanisms, behind scurvy
Briefly explain the causes, including the molecular mechanisms, behind Marfan’s syndrome
Briefly explain the causes, including the molecular mechanisms, behind osteogeneis imperfecta
What does areolar mean?
‘Little space’
Describe dense connective tissue
- Also known as ‘fibrous’ or collagenous tissue
- Two types:
1) Irregular - Fibres running in different directions
2) Regular - Fibres running in parallel to each other
Summarise loose connective tissue
Give 2 examples of loose connective tissue
Describe the properties of ground substance in connective tissue
- Viscous, clear substance with a high water content
- It is composed of proteoglycans
What is a proteoglycan?
A proteoglycan is a large macromolecule consisting of a core protein to which glycosaminoglycans (GAGs) are covalently bound
Distinguish between the structure of loose and dense connective tissue
- Loose:
I. Many cells
II. Sparse collagen fibres
III. Abundant ground substance
- Dense:
I. Few cells, nearly all fibroblasts
II. Many collagen fibres
III. Little ground substance
oDense connective tissue – irregular (e.g. dermis)
oDense connective tissue – regular (e.g tendon)
