Integrating Cells Into Tissues Flashcards
How long can packed red cells be stored at 6 degrees C?
42 days
How long can packed red cells be frozen for?
10 years (but they are rarely frozen)
What is a tight junction and what is its function?
Where adjacent cells are held tightly together - forms a seal to prevent molecules from passing between 2 cells so anything on the lumen side has to pass through the cell rather than between the cells
Is a tight junction impenetrable?
Tight junctions are impenetrable and selective
E.g. Bacteria cannot pass into the lining o the intestine
Describe gap junctions
Allow cells to communicate effectively with each other
Proteins called Connexons form channels for ions and small molecules between cells
Allow messages to pass between cells to allow communication and co ordinate function eg cilia beating together
What is a desmosome?
A structure by which 2 adjacent cells are attached, formed from protein plaques in the cell membrane frames by filaments
What is the function of desmosomes?
Strengthen the connections between intermediate cells. Resistant against stretching and twisting.
Where are desmosomes found?
Found between epithelial cells which need to withstand stress, e.g. Skin
2 cells come together under or between tight junctions
What is the basement membrane?
The structural site for overlying cells and underlying connective tissue.
What are the 2 ways cells can attach to the basement membrane?
Hemidesmosomes and focal adhesions
Describe hemidesmosomes
Hemidesmosomes (HD) are very small stud- or rivet-like structures on the inner basal surface of keratinocytes in the epidermis of skin. They are similar in form to desmosomes when visualized by electron microscopy. While desmosomes link two cells together, hemidesmosomes attach one cell to the extracellular matrix.
Where are hemidesmosomes found?
Tissues subject to abrasion such as skin and epithelium of oral cavity
Describe focal adhesions
Anchor intracellular actin filaments to the basement membrane.
What is a function of focal adhesions?
They play a prominent role in cell movement such as migration of epithelial cells in wound repair
What are integrins?
Transmembrane proteins that function mechanically by attaching the cell cytoskeleton to the extracellular matrix,and biochemically, by sensing whether adhesion has occurred
What are the 2 main functions of integrins?
Attachment of the cell to the ECM
Signal transduction from the ECM to the cell
What are some lesser functions of integrins?
Immune patrolling and cell migration
Is it possible to separate cels from tissues?
Yes, using collagenase or microdissection. The cells can then be cultures in Petrina dishes or flasks.
Need to provide nutrients, control pH, temperature and oxygen, and prevent bacterial contamination
Do cultured cells look the same as the same cells in tissues?
No, they look and behave differently. They also demonstrate contact inhibition
Do cultured cells demonstrate senescence?
Yes, they have a limited lifespan
What is direct contact communication?
Adjacent cells communicate by ions and small molecules passing through connexons in gap junctions
What is autocrine communication?
Cell communication whereby a cell secretes a chemical which attaches to receptors on the same cells
What is paracrine communication?
Cell communication whereby a cell secretes chemicals which interact with cells near it
What is endocrine communication?
Cell communication whereby a cell secretes hormones directly into the bloodstream (ductless) which act on distant target cells.
What is synaptic communication?
Cell communication whereby electric signal travels along a nerve, which stimulated release of neurotransmitter. The neurotransmitter diffuses across the synapse and stimulates the target cell
What is neurocrine communication?
Cell communication whereby an electric signal travels along a nerve and releases signal into the bloodstream.
Examples are the hypothalamus, posterior pituitary and adrenal medulla
What are the 2 methods by which cells can die?
Apoptosis and necrosis
Describe necrosis
Necrosis caused by physical disruption through the cell though injury e.g. Bacteria
Cell loses functional control
Osmotic pressure
Swelling of endoplasmic reticulum and mitochondria
Breakdown of plasma membrane, organelles and nucleus
Cell bursts
Contents spill
Describe apoptosis
Condensation of chromatin Membrane blabs form Cellular fragmentation Apoptotic bodies form Phagocytosis of apoptotic bodies Regulated by Bcl-2 protein
What does static mean in relation to cell renewal? Give some examples of static cells
Barely change/renew
CNS, cardiac and cake legal muscle cells
What does stable mean in relation to cell renewal? Give some examples of stable cells
Change/renew sometimes
Fibroblasts, endothelium, smooth muscle
What does renewing mean in relation to cell renewal? Give some examples of renewing cells
Renew/change frequently
Blood, skin epithelium, gut epithelium
What are the 2 main types of organisms in nature?
Prokaryotes and eukaryotes
What is the origin of the mitochondria?
At some stage an aerobic bacterium was taken into an anaerobic eukaryocyte and formed an organelle which later became a mitochondrium – cells and complex life could develop.
Define tissue
A collection of cells working together to achieve a common function
What are the 4 basic types of tissue?
Epithelial
Muscle
Nerve
Connective tissue
Give some examples of specialised connective tissues?
Adipose Lymphatic Blood Haemopoietic Cartilage Bone
Describe epithelium and where it is found
A tissue composed of cells that covers the exterior body surface and lines internal closed cavities and body tubes that communicate with the exterior. Epithelium also forms the secretory portion of glands and lines their ducts. In addition, specialised epithelium functions as receptors for the special senses (smell, taste, hearing and vision)
Do epithelial cells have a free surface?
Yes, they exhibit polarity and comprise
Apical domain
Lateral domain
Basal domain
What are epithelioid cells?
Epithelial cells which do not have surface, e.g. Leydig cells in the testes, lutenin cells in the ovaries, Islets of Langerhans in the pancreas, parenchyma of the adrenal glands
Are all apical domains the same?
No, they are specialised depending on the tissue
What are microvilli?
Cytoplasmic processes that extend from the cell
surface. Examples are intestine and kidney tubule
What are stereovilli?
Particularly long microvilli limited to epididymis
and sensory hair cells of the ear
What are cilia?
Motile cytoplasmic processes that can beat in
synchrony with a rapid forward movement called the
effective stroke and a slower return recovery stroke.
Examples are the tracheobronchial tree and the oviducts
