Tissue Types & Cell Junctions Flashcards by Emmaly Smith

Tissue

Similar cells in close proximity, working together towards a common function.

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What does tissue composition and structure reflect?

The tissue’s function and the larger organ’s function

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What are the four main tissue types?

Epithelial Tissue
Nervous Tissue
Muscle Tissue
Connective Tissue

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What are the general functions of epithelial tissue?

Protection -> Convers external surfaces and lines internal surfaces and tubes

Secretion & Absorption

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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

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Is epithelial tissue vascular?

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What are the general functions of connective tissue?

Connecting to other tissues
Structural support and protection
Storage and exchange medium

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What is the cell to ECM ratio of connective tissue?

Lots of cells that are not touching

Abundant ECM and many fibers

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Is connective tissue vascular?

Sometimes

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What are the general functions of muscle tissue?

Contraction and Movement

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What is the cell to ECM ratio of muscle tissue?

Many cells in direct contact and some form bundles.

Some ECM

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Is muscle tissue vascular?

Yes

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What are the general functions of nervous tissue?

Receiving, transmitting, and integrating information

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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

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Is the nervous tissue vascular?

Yes

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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

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If a cell is surrounded on all sides by other cells, what are all of its sides considered?

Lateral Domains

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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

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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