Week 3 content: tissue level of Organisation- Epithelial tissue Flashcards
LC: What are the four types of tissue in the body
- epithelial
- connective
- muscular
- nervous
What is the role of a gene in coding for protein production
- genes must be activated (bound protein removed)
- specific codons indicate where RNA polymerase starts and stops reading gene code
- daughter cells produced express specific gene codes for a specific protein
- active gene = protein production
What is cell differentiation
- where an unspecialised cell (stem cell) becomes more specialised
- developing unique structures and functions
- non-reversible
- AKA the cell cycle
types of stem cells
Adult - partially differentiated, limited pathways of development
Embryonic: can develop into any cell type
What is tissue?
Organised aggregation of cells that function collectively
What are the (7) characteristics of epithelial tissue
- lines internal and external surfaces of the body
- protection (biological, chemical and physical)
- densely packed cells held together by intercellular connections
- polar
- lack of blood supply ∴ requires nutrients via diffusion
- avascular but innervated (nerves provide sensation)
- regeneration of stem cells for repair and replacement of damaged or old skin cells
what are the two sides of the epithelial tissue called? what are they exposed to
apical - exposed to the external environment, or exposed to the interior of hollow organs
- basal: the basement layer, sits between epithelial and connective tissue, support, filter and communication
what are stem cells and how do they function
- non-specialised cells
- stem cells are located near the basal lamina (basement membrane)
- due to the rapid turnover of epithelia, stem cells are necessary for rapid production and replacement
What are the components and specialised components of epithelial cells
- apical surface
- Golgi apparatus
- nucleus
- basal lamina
- mitochondria
specialised
- cilia: move substances over cell surface (beating movement, push egg through fallopian tubes into uterus)
- microvilli: bumps on cell surface to increase SA (more efficient nutrient absorption in small intestines)
what are the (4) functions of epithelial tissue
- physical protection
- controlled permiability
- sensation
- specialised secretion (glands produce mucus for lubrication)
2 classifications of epithelia tissue
location and function influence the
shape and amount of cell layers
how does shape influence epithelial tissue. What are the different shapes of epithelial tissue
squamous = simple and stratified: flat (high SA to volume ratio)
cuboidal = cube-like (good SA to volume ratio)
columnar: large rectangular size
characteristics of squamous cells
- flat, thin with disc-like nuclei
simple:
- thin and flat layer covering basal lamina
- delicate
- always found on internal body surfaces where rapid diffusion and absorption occurs
- lung tissue, lining of blood vessels, kidney glomeruli
stratified:
- strong, multilayered
- has many cell layers
- can resist mechanical stresses
- some deeper layers of squamous cells look cuboidal, however, are classified as squamous due to the flat nature of surface cells
- skin and mouth lining
characteristics of stratified cuboidal cells
- fragile
- found where secretion and absorption are important
- centrally located nuclei
- found in kidney lining - waste secretion and nutrient absorption (simple), duct of sweat glands (stratified)
what are the characteristics of simple columnar
- tall, rectangles with elongated nuclei
- nuclei are located near basal lamina
- single layer
- large size = high production of secretion (contain goblet cells to do this)
- have cilia and microvilli on apical surface
- found in small intestines (simple), lining of epiglottis and pharaynx (striated)
what is transitional epithelium
when cells change shape, allowing the epithelial layer to thin and stretch
- seen in the bladder when storing urine
what are cell junctions
multi-complex protein complexes
- link cells to extracellular matrix (cell-matrix junction) or
connect neighbouring cells (cell-cell junctions)
what are the (3) types of junctions
anchor - stabilise cell position and epithelial structure (via sticky proteins and intercellular cytoskeletal network)
- desmosomes
- Adherens junctions
Occlude: block passage between cells to stop leakage of substances
- Tight junctions (“zips” cells together)
Cell-cell communication:
- allows rapid communication
- gap junctions (form channels between cells for ion and molecule transport)
what are Glandular epithelium
- a type of secretory tissue that obtains molecules from the blood to produce secretions (hormones, enzymes)
- can be uni or multi-cellular
What are unicellular and multicellular epithelium glands
unicellular
- single secretory cell
- goblet cells
multicellular:
Exocrine
- membranes invaginated into connecting tissue to aid in release of glandular secretion onto epithelial surface
- AKA ducts - milk, tears, sweat
Endocrine
- loss of connecting cells from the membrane
- ductless
- secrete hormones directly into the bloodstream via chemical messages
- pituitary gland, thyroid
What are goblet cells
- unicellular gland cells in epithelial lining “colan”
- secrete mucus
- contain secretory vesicles - mucin
LC: Describe the basic properties of epithelial tissue
LC: Explain how epithelial tissue is constructed
- via production of non-specialised stem cells in the basal lamina
LC: Define classifications of epithelial tissue
