0404 - Connective Tissue - RM Flashcards
What is connective tissue? What does connective tissue do? How are the different types of connective tissues formed? What are the different types of connective tissues in our body? What is the appearance of the different components of connective tissue?
What is connective tissue?
A group of similar, specialised, cells that collectively perform the common functions of: supporting and protecting organs, filling space between other tissues binding tissue systems together.
What are the four functions of connective tissue?
Structural (binding, protecting, supporting). Mediating (exchange of nutrients, intermediates, waste products between cells and circulatory system). Repair (including scarring) Defence (immune cells in blood)
What is the common origin of all connective tissue?
Embryonic mesenchyme.
What are the two basic forms of connective tissue?
Extracellular matrix (ground substance and fibres) Cellular (indigenous and migratory)
Fibroblast – most common indigenous connective tissue Spindle-shaped indigenous cell, responsible for maintaining and building ECM Active (fibroBLAST, many organelles, prominent nucleolus, found in healing wounds). May be stained very dark by presence of RER. Inactive (fibroCYTE, oval nuclei, few organelles).
What cell type is the arrow pointing to?
Reticular Cell
Indigenous - Found in reticular connective tissue. Larger than fibrocyte. Large, lightly stained nuclei Irregular cytoplasm.
Do not confuse with ‘reticulocyte’ - immature erythrocyte.
Adipocyte
Indigenous – Fat cell Large, almost entirely white Nucleus pushed to periphery due to fat.
Macrophage (also monocyte)
Migratory - Pseudopod movement may be visible.
May be phagocytosing another cell.
VERY difficult to distinguish from fibroblasts otherwise.
Mast Cell
Migratory – Defence against foreign proteins (responsible for allergic reactions).
Granular appearance due to many large vesicles of histamine and heparin in cytoplasm.
Plasma Cells
Migratory – Defence by producing antibodies. Commonly found together in significant quantities, with a round nucleus. When active, contain a large cytoplasm and the cells are basophilic (attract stain).
Known as having a ‘clock face’ presentation.
Eosinophils
Migratory – Defence by phagocytosis or release of granules. Rounded or oval cells with a bi-lobed nucleus. May contain crystals in the cytoplasm.
Lymphocyte
Migratory, small (6-8µm) cell, with round, very dark nuclei. Small cytoplasm may be difficult to see. Non-granular cell.
What are the two components of the extracellular matrix?
Ground substance (protein-based ‘gel’ between fibres) Fibres (collagen, elastin, or reticular)
What are the wavy pink fibres?
Collagen fibres
Most CT fibres are made of collagen. Provides strength and support. Thick bundles with an elongated, wavy, pink appearance. Individual fibres 1-10µm wide. Fibres composed of fibrils and microfibrils. Striated appearance may be visible on electron microscopy.
What are the fibres in this image?
Reticular Fibres
Tiny collagen fibres in loose CT and blood vessels. Form delicate networks that support cells, rather than bundles.
Demonstrated by using silver stains (hence dark, not pink).
Elastic Fibres
Form a coil, with links between fibres. Found in CT where elasticity is required (skin, lung, bladder, blood vessels, ligaments etc).
What lies between the two arrows?
Basement membrane
Sheet of ECM proteins that divides epithelial and functional cells. Provides anchor for epithelium. Controls growth of epithelial cells.
What are the two types of connective tissue? What are their sub-types?
Dense (fibrous) - more fibres, less cells Regular Irregular Loose (areolar) - lots of small spaces Mucoid Reticular Adipose
Dense irregular connective tissue
Dense irregular connective tissue
No clear orientation of fibres. Bundles for a mesh, with fibrocytes scattered between. Found in dermis of skin, and capsules of organs.
Dense regular connective tissue
Tightly packed, parallel fibre bundles. Found in tendons, ligaments, cornea of eye.
Allow considerable stress to be applied, and resist deformation, in one direction.
What type of tissue is in the picture?
Mucoid connective tissue
A few nuclei scattered between loosely-spaced fibres. Large amount of ground substance – may be jelly-like. Found in umbilical cord and dental pulp.
What tissue type is this?
Reticular connective tissue
Consists of reticular cells and surrounding reticular fibres (delicate networks). Form a structure to suspend organ cells, assisting diffusion and cell movements. Found in liver, lymph nodes, spleen.
What are the two forms of adipose tissue? What are their functions?
White fat – one large droplet of fat provides energy storage.
Brown fat – many small droplets of fat provides thermal regulation via mitochondria. Generally found in infants.
