Structures and Functions
Simple Squamous Epithelial Tissue
- Single layer of thin, flat cells
- Large surface area
- Tightly packed together
- One side of the surface opens to the lumen (apical surface); the other is attached to the underlying cells (basolateral surface)
- Larger, elliptically shaped nuclei
- Mediator of filtration and diffusion
- Allows small molecules to move across the membrane and through the cells
- Helps determine what is able to move from the lumen and into the bloodstream and vice versa
- Thin membrane allows for the passage of small molecules into the body (i.e. when air diffuses into the lungs)
- Tightly bound cells form a selective barrier that helps keep out molecules that don't belong
Simple Cuboidal Epithelial Tissue
- Single layer of cells that are equally wide as they are tall
- Appear hexagonal on the surface
- Tightly packed together
- More organelles (mitochondria, ribosomes, golgi bodies)
- Large, spherical, centrally located nuclei
- Sometimes have microvilli on the surface
- Act like a semipermeable membrane
- Perform active transport
- Provide a layer of protection from abrasion, foreign particles, invading bacteria, and excessive water loss to the underlying tissue
- Tall cells allow for selective permeability, which keeps out harmful substances and retains useful ones
- Cuboidal shape of the cells allows for tight packing, which enables fluids to pass through tubes lined by them
- Cell organelles allow the cells to produce and package large molecules or process substances absorbed by the cell
Smooth Muscle Tissue
- Made up of fusiform (diamond-shaped) cells
- Fibers are small and tapered, with the ends reducing in size
- Centrally located, oval nuclei
- Cells are arranged in sheets
- Contracts hollow organs and keeps the eyes in focus
- Helps move fluids through the body and eliminate indigestible matter from the gastrointestinal system
- Since the relaxed muscle is long and not bundled up, it can easily contract.
Cardiac Muscle Tissue
- Made up of many branch-shaped, interlocking cells
- Nuclei are striated, or striped
- Protein filaments (dark bands made of myosin, light bands made of actin)
- To contract in order to pump blood through the body
- Myosin pulls the actin filaments together like an accordion to shrink the muscle cell and make it contract
- Branch shape connects each cell to three other cells; finger-like extensions of the cell membrane overlap neighboring cells so that they cannot separate under the strain of pumping blood
- Contains few, tiny spaces
- Permeated by an elaborate system of interconnecting vascular canals
- Provides protection and support to everything around which it is the outer layer
- Helps enable long bones to bear the stress placed on them by the weight of the body and the use to which the limbs are put
- Layered cells make the bone strong so that it can protect and support everything it surrounds and help enable long bones to bear stress.
- Glassy appearance
- Covered externally by a fibrous membrane that contains vessels that provide the cartilage with nutrition
- Cells of a rounded form
- Reduces friction at joints
- Supports bronchial and tracheal tubes
- Acts as a shock absorper between vertebrae
- Maintains the shape and flexibility of fleshly appendages
- Fibrous membrane provides the cartilage with needed nutrition so that the tissue can function properly
- Strength and flexibility of the cartilage allow it to be constantly pulled and compressed by bone movement
- Multipolar, each cell contains a single axon and multiple dentrites
- Dentrites branch out from the cell body
- Cell body (soma) contains cellular components and genetic information
- Axon (nerve fiber) is long and thin
- Project their axons outside of the central nervous system to directly or indirectly control the contraction or relaxation of muscles
- Dentrites can receive electrochemical signals from units of the nervous system because they branch out
- Cellular components and genetic information in the cell body keep the cell functional
- Axon is long and thin to allow it to quickly conduct electrical impulses and send signals where they are needed
- Made up of white blood cells
- Many lysosomes
- Cytoplasm appears granular
- Lobed nucleus
- Ingest and destroy invading microrganisms
- Lysosomes contain enzymes that kill ingested cells
- Lobed nucleus allows for greater flexibility
- Plasmic membrane traps germs so that the granules can attack them
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