LECTURE 16 : Cells, tissues, communication Flashcards
4 major tissue types
epithelium
connective
nervous
muscle
5 epithelial sheets
- simple cuboidal (cells are cube shaped, 1 layer)
- simple columnar (cells are column shaped, 1 layer)
- simple squamous (cells are flat, 1 layer)
- stratified squamous (cells are flat, multiple layers)
` - pseudostratified ciliar columnar (appears stratified [multiple layers] but actually just columnar with the nucleus up and down so looks like multiple layers)
structure of epithelia
epithelial tissue are just these cells arranged in those sheets
apical surface: the side that is facing the lumen, may have specialised structures like villi and microvilli
basal surface : the side of epithelial cells anchored to the basal lamina
basal lamina : attached to connective tissue
connective tissue : contains blood vessels, nerves, and lymphatic vessels , supplying nutrients and oxygen to the epithelial cells.
structures found in epithelial
Desmosomes
strong cell-to-cell adhesion, holding adjacent cells together.
–>crucial for maintaining tissue integrity and withstanding mechanical stress.
-strong and flexible connection between cells, allowing for some tissue elasticity while maintaining adhesion.
attached to intermediate filaments
Gap junctions
facilitate direct cell-to-cell communication by allowing the exchange
Hemidesmosomes
anchoring epithelial cells to the basal lamina
transport in epithetlia
active transport through apical membrane (from lumen of e.g. gut into epithelial cells), passive transport through basal membrane (from epithelial cells to blood)
glucose transport in epithelial
Active transport through apical membrane : active glucose channels into intercellular space of epithelial cell
passive transport through basal membrane : passive glucose carriers into blood stream
cancer in epithelila + basal lamina
basal lamina acts as a temporary barrier against metastasis, benign cancers are contained within the ducts with the basal lamina
malignant cancers, produce protease which over time disgests the basal lamina and spreads throughout the body
nervous tissue
Allows the multicellular
animal coordinated
movement and behaviour.
action potentials : how it polarises and depolarises
connective tissues
- cells
- fibres (Collagen Fibers: Strong and flexible fibers that provide tensile strength to the tissue.
Elastic Fibers: Stretchable fibers that allow tissues to return to their original shape after being stretched or deformed.
Reticular Fibers: Fine, branched fibers that form a supportive network in some tissues.) - ground substance (like proteins and liquid. It plays a role in nutrient exchange, hydration, and tissue resilience.)
fibres + ground substance = extracellular matrix (ECM)
ECM = non cellular components
muscle tissues
skeletal : long, multinucleated, cylindrical fibers
smooth : spindle-shaped, non-striated cells with a single nucleus.
cardiac : branched, striated cells with a single nucleus, intercalated discs.
Both skeletal and cardiac muscles have a striated appearance due to the arrangement of myofibrils, while smooth muscles lack striations.
Skeletal muscles are voluntary, cardiac muscles and smooth are involuntary
steriod hormones
steroids are soluble and can diffuse through the cell membrane
once in the cell, binds to receptor inside to form hormone-receptor complex
hormone-receptor complex acts as a transcription factor and interacts with specific DNA sequences
neurotransmitter
Neurotransmitters bind to specific receptors on the postsynaptic cell’s membrane.
–> can open or close ion channels.
–> the flow of cations
–> generates postsynaptic potentials
Peptide Hormones (Protein Hormones)
peptide hormones are released by endocrine glands into the bloodstream.
peptide hormones bind to specific cell surface receptors on the target cell’s membrane.
–> activates intracellular signaling pathways, typically involving second messenger systems (e.g., cAMP, calcium ions).
–> cellular response
