Anatomy – Cell Junctions

definition of “cell junctions”
contact points between the plasma membranes of tissue cells (how cells are held together to form tissues)

name the 5 main types of cell junctions
1. tight junctions; 2. adherens junctions; 3. desmosomes; 4. hemidesmosomes; and, 5. gap junctions

tight junctions
form tight seals between cells with weblike strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes); prevents passage of substances between cells (i.e., tissues that line the stomach, intestines, and urinary bladder have many tight junctions)

adherens junctions
contain plaque, a dense layer of proteins on the inside layer of the plasma membrane that attaches both to membrane proteins AND to microfilaments of the cytoskeleton; transmembrane glycoproteins called CADHERINS join the cells; in epitheleal cells, adherens junctions often form extensive zones called “adhesion belts” that encircle the cell; (help epitheleal surfaces resist separation during various contractile activities like when food moves through the intestines)

desmosomes
contain plaque and transmembrane glycoproteins (cadherin). Plaque attaches to intermediate filament (keratin) which extends from desmosomes on one side of the cell across cytoplasm to a desmosomes on the opposite side of the cell. (prevent epidermal cells from separating under tension and cardiac muscle cells from pulling apart during contraction)

hemidesmosomes
strongly anchor cells to an underlying basement membrane NOT to other cells; transmembrane glycoproteins are INTEGRINS

gap junctions
membrane proteins called CONNEXINS form tiny fluid-filled tunnels called connexons that connect neighboring calls; connexons allow ions and small molecules to diffuse from the cytosol of one cell to another; allow cells to communicate with one another; enable nerve or muscle impulses to spread rapidly among cells; found in nervous system, cardiac muscle and gastrointentinal tract

cell theory 1. all living things are made of cells 2. Cells are the basic units of structure 3. new cells are made only from existing cells nucleus control center, contains general DNA WE WILL WRITE A CUSTOM ESSAY SAMPLE …

cell theory concept that cells are the fundamental units of all living things 2 types of cells contained in the body: 1. sex cells 2. somatic cells WE WILL WRITE A CUSTOM ESSAY SAMPLE ON ANY TOPIC SPECIFICALLY FOR YOU …

Some eukaryotic cells have cell walls, although these walls are generally much simpler than those of prokaryotic cells. Most algae have cell walls consisting of the polysaccharide cellulose (as do all plants). Cell walls of some fungi also contain cellulose, …

Plasma Membrane External boundary of the cell; Contains cell contents, regulates entry and exit of materials. Lysosomes Scattered in cytoplasm; Digest ingested material and worn out organisms. WE WILL WRITE A CUSTOM ESSAY SAMPLE ON ANY TOPIC SPECIFICALLY FOR YOU …

chromatin scatterted throughout the nucleus, its DNA is combined with protein+ forms a loose network of bumpy threads cilia whiplike cellular extensions that move substances along the cells surface WE WILL WRITE A CUSTOM ESSAY SAMPLE ON ANY TOPIC SPECIFICALLY …

Histology Study of normal structures of tissues Two basic components of tissues consist of discrete population of cells that are related in structure and function have a surrounding material called extra cellular matrix (ECM) WE WILL WRITE A CUSTOM ESSAY …

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