Tissue Types & Cell Junctions Flashcards
Tissue
Similar cells in close proximity, working together towards a common function.
What does tissue composition and structure reflect?
The tissue’s function and the larger organ’s function
What are the four main tissue types?
- Epithelial Tissue
- Nervous Tissue
- Muscle Tissue
- Connective Tissue
What are the general functions of epithelial tissue?
Protection -> Convers external surfaces and lines internal surfaces and tubes
Secretion & Absorption
What is the cell to ECM composition in epithelial tissue?
Many cells is direct contact that forms clusters or sheets
Very little ECM - basement membrane only
Is epithelial tissue vascular?
No
What are the general functions of connective tissue?
Connecting to other tissues
Structural support and protection
Storage and exchange medium
What is the cell to ECM ratio of connective tissue?
Lots of cells that are not touching
Abundant ECM and many fibers
Is connective tissue vascular?
Sometimes
What are the general functions of muscle tissue?
Contraction and Movement
What is the cell to ECM ratio of muscle tissue?
Many cells in direct contact and some form bundles.
Some ECM
Is muscle tissue vascular?
Yes
What are the general functions of nervous tissue?
Receiving, transmitting, and integrating information
What is the cell to ECM ratio of nervous tissue?
Many cells in direct contact and some form bundles.
Some ECM in PNS and no ECM in CNS
Is the nervous tissue vascular?
Yes
What are the three domains of cells with orientation? What part of the tissue are they associated with?
- Apical - Close to lumen of duct, organ, skin surface, or vessel like fluid, blood, secretions
- Lateral - adjacent to neighboring cells
- Basal - close to basement membrane and whatever tissues form layer below
If a cell is surrounded on all sides by other cells, what are all of its sides considered?
Lateral Domains
What do cell junctions allow cells to do? What junctions are associated with each function?
Work as a team in communication, support, cohesiveness, and exclusivity.
Gap junctions - communication
Anchoring junctions - support, link cells to adjacent cells, prevent separation
Occluding (tight) junctions - cohesiveness and exclusivity, stop outside from entering
What are 3 components in most kinds of junctions?
- Transmembrane proteins - intercellular connecters
- Intracellular linker (attachment) proteins - intracellular adapters
- Cytoskeletal filaments - intracellular anchors
What is the function of an occluding junction?
Seal off intercellular spaces from lumen contents
Keep domains separate - maintains polarity
Block pathogens from entering intercellular spaces
Regulate movement between cells - paracellular pathway
Where are occluding junctions located on the cell?
Between the apical and basal domains of a cell
What tissues have occluding junctions?
Common in surface/lining epithelia
Epidermis of skin
Cells lining ducts, GI tract, vessels, etc.
What are the proteins involved in occluding tight junctions?
Transmembrane proteins - occludin and claudins
Intracellular linker proteins - ZO proteins (ZO-1, ZO-2, ZO-3)
Cytoskeletal component - actin filaments
What is the function of an anchoring junction?
To keep the team of cells together by linking adjacent cells
Keep the cells grounded by anchoring cells to ECM (basement membrane)
Mechanotransduction - transmit forces through tissued
Where are anchoring junctions located in epithelial cells?
Lateral domain - all around cell and they link adjacent cells and prevent separation from neighbors
Basal surface - link cells to basement membrane and keep cells anchored to underlying tissue
What are the 4 kinds of anchoring junctions?
Adhesion Belt
Desmosomes
Hemidesmosomes
Focal adhesions
What are the functions of adhesion belts?
Lateral adhesion between adjacent cells
Where in the cell are adhesion belts located?
Continuous band on lateral surface, just below occluding junction
Where are adhesion belts found?
Epithelial cells that have junctional complexes
What proteins are involved in adhesion belts?
Transmembrane proteins - cadherins
Intracellular linker proteins - catenins, vinculin, and alpha-actinin
Cytoskeletal component - actin filaments
What are the functions of desmosomes?
Lateral adhesions between adjacent cells
Help resist mechanical stress
Mechanotransduction
Where are desmosomes located in cells?
Scattered around lateral domain
What proteins are involved in desmosomes?
TMPS - cadherins
Intracellular linker proteins - desmoplakin and catenins
Cytoskeletal component - intermediate filaments
What are the functions of hemidesmosomes?
Anchors cells to basement membrane/ECM
Prevent delamination of cell layer
Help cells resist abrasion, shearing
Where are hemidesmosomes located in the cell?
Scattered around basal domain
What tissues commonly have hemidesmosomes?
Common in cornea, vagina, and esophagus
What proteins are involved in hemidesmosomes?
TMPS - integrins and type XVII collagen. Basement membrane or ECM component contains laminins and type IV collagen
Intracellular linker proteins - “desmoplakin-like” proteins
Cytoskeletal component - intermediate filaments
What are the functions of focal adhesions?
Anchors cells to basement membrane/ECM
Regulate cell migration
Mechanotransuction from the extracellular environment into the cell
Where are focal adhesions located within the cell?
Scattered around basal domain
What proteins are involved in focal adhesions?
TMPS - integrins. Basement membrane or ECM component contains laminins and fibronectin
Intracellular linker proteins - talin, vinculin, alpha-actinin
Cytoskeletal component - actin filament
What is the function of gap junctions?
Form cell to cell channels that allow direct exchange of metabolites and signals
Connect adjacent cells; cytoplasm
Coordinate cell activities across entire tissue
Exchange fluid and metabolites
Molecular and electric signaling - regulate cell growth, differentiation, and recognition
What tissues commonly have gap junctions?
Muscle tissue, neurons, and epithelia. Also common in embryonic tissues
Where are gap junctions located in the cell?
Scattered around lateral domain
What proteins are associated with gap junctions?
TMPs - Each side has a channel called a connexon
6 connexins form a connexon
Each gap junction is a small region with many connexons
What are the components of junctional complexes from top to bottom?
Occluding junction
Adhesion Belt
Ring of small desmosomes that goes all the way around the cells
