Cellular Interactions and Communication

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Epithelial tissue
Covers the outside of the body and lines organs, vessels and cavities. They are tightly packed together in sheets and lay on top of a basal lamina/membrane
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Fibroblast
Synthesise the extracellular matrix, which is made up of lots of different proteins including collagen and elastin
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Basement membrane
Synthesised by epithelial cells. Made up of laminin and collagen. Not penetrated by blood vessels so they get their nutrients from diffusion
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Laminin
Synthesised by epithelial cells. It is a heterotrimer - made up of 3 chains - alpha, beta, gamma. Contains collagen. Contributes to organising the matrix and helping cells to attach to it
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Sebaceous gland
Epithelial cells secrete sebaum into the lumen of the duct of this gland, which travels to the surface of the skin to waterproof it
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Tight junctions
Define the boundaries between the apical surface and the basolateral surface - this gives the cell polarity. They have a barrier and fence function
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Connective tissue
Consist of cells embedded in an extracellular matrix, including fibroblasts, adipocytes, mast cells, macrophages, etc.
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Extracellular matrix
Composed of ground substance (a clear viscous substance made of hydrophilic proteoglycans that trap water) and fibres (collagen and elastin)
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Proteoglycans
Have a core protein, link tetrasaccharides, glycosaminoglycan (GAG) units. GAGs are unbranches polysaccharides composed of repeating disaccharide units. They are negatively charged, attract Na+ which attracts H2O which produces the viscous gel
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Collagen
Found in connective tissue, basement membrane, bone etc. It consists of 3 alpha chains wound around each other to form a triple helical structure - this helps to resist stretching forces
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Elastin
Found in connective tissue and blood vessels. It consists of tropoelastin chains that have been crosslinked. It confers resilience, i.e. elasticity
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Epidermis
A stratified squamous keratinised epithelium that forms the first layer of skin. Also has hair follicles, sebaceous glands and sweat glands
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Dermis
A dense fibroelastic connective tissue. It forms the middle layer of the skin
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Hypodermis
A loose fibro-fatty connective tissue. It forms the bottom layer of the skin
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Epidermis formation
Keratinocyte stem cells, in the basal layer, divide to produce new stem cells and transit amplifying keratinocytes. These undergo cell division, detach from the basement membrane and migrate to skin surface whilst undergoing terminal differentiation
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Terminal differentiation
Consists of: the degredation of nuclei, aggregation of keratin, extrusion of lipids by lamellar bodies, formation of cornified envelope
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Cornified envelope
A tough insoluble sac that forms beneath the plasma membrane of differentiating keratinocytes. The proteins assemble here, and are cross-linked by enzymes to form the envelope. The envelope then surrounds keratin
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Stratum corneum
The top layer of the epidermis. It consists of keratin-filled sacs embedded in a lipid matrix ('bricks and mortar'). It has a barrier function - prevents water loss, protects against microbial invasion, etc.
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Transepidermal
A route taken by drugs to penetrate the stratum corneum. Consists of the paracellular pathway (between - drugs have to be small and lipophilic) and transcellular (through - drugs must be hydrophilic)
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Transappendageal
A route taken by drugs to penetrate the stratum corneum. The drugs go via the sweat glands or hair follicles of which there are fewer so this route is more difficult
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Gap junction
Allows for the movement of small molecules between adjacent epithelial cells. Usually just water and small soluble ions
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Desmosomes
Involved in cell-cell adhesion by linking to intermediate microfilaments within the cytoskeleton
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Hemidesmosomes
Involved in cell-matrix adhesion by linking to intermediate microfilaments within the cytoskeleton
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Adherens junctions
Involved in cell-cell adhesion by linking to actin microfilaments
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Focal adhesion
Involved in cell-matrix adhesion by linking to actin microfilaments
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Actin filaments
They are formed by two strands of polymerised actin monomers called G actin (globular). They interact with adherens junctions and focal adhesions.
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Microtubules
They are formed by the polymerisation of tubulin. Tubulin consists of a alpha-beta heterodimer. They are involved in cell division
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Intermediate filaments
Made from keratin - a coiled dimer. It stops tissues from coming apart by anchoring the membrane to desmosomes and hemidesmosomes
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Contact dependent
A type of local signalling where the signalling cell and recipient cell are adjacent to each other, and the signal molecule remains bound to the signalling cell
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Paracrine
A type of local signalling where the signalling cell can secrete a signal molecule (local mediator) and the target cell receives it; they may be 2 or 3 cell diameters away.
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Synaptic
A type of remote signalling where a nerve cell is activated and an electrical signal is sent down the axon which causes the signal molecule (neurotransmitter) to be released to the target cell
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Endocrine
A type of remote signalling where a cell secretes a hormone into the bloodstream and the target cell can be anywhere within the body
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Other cards in this set

Card 2

Front

Synthesise the extracellular matrix, which is made up of lots of different proteins including collagen and elastin

Back

Fibroblast

Card 3

Front

Synthesised by epithelial cells. Made up of laminin and collagen. Not penetrated by blood vessels so they get their nutrients from diffusion

Back

Preview of the back of card 3

Card 4

Front

Synthesised by epithelial cells. It is a heterotrimer - made up of 3 chains - alpha, beta, gamma. Contains collagen. Contributes to organising the matrix and helping cells to attach to it

Back

Preview of the back of card 4

Card 5

Front

Epithelial cells secrete sebaum into the lumen of the duct of this gland, which travels to the surface of the skin to waterproof it

Back

Preview of the back of card 5
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