Lecture 1 - Epithelial Tissue

What type of cells make up epithelial tissues?

Aggregated polyhedral cells

What is the extracellular matrix amount in epithelial tissues?

Small amount

What is the main function of epithelial tissues?

Lining of surface or body cavities

What is the main secretory function of epithelial tissues?

Glandular secretion

What is the main function of connective tissues?

Support and protection of tissues/organs

What are the main functions of muscle tissues?

Strong contraction; body movements

What is the main function of nervous tissues?

Transmission of nerve impulses

How strongly do the aggregated polyhedral cells of epithelial tissues adhere to one another?

Adhering strongly to one another

What do epithelial tissues line in the body?

All external and internal surfaces of the body

What are the principal functions of epithelial tissues?

Covering, lining, and protecting surfaces, absorption, secretion

What shapes do covering epithelium cells vary in?

Columnar, cuboidal, and squamous

How do the cells in covering epithelium fit?

Cells fit closely together

How many free surfaces does a tissue layer of covering epithelium always have?

One free surface

What is the lower surface of covering epithelium bound by?

A basement

What term describes the lack of blood vessels in covering epithelium?

Avascular

When does covering epithelium regenerate easily?

If well nourished

What classification of epithelial cell layers refers to a single layer?

Simple (1)

What classification of epithelial cell layers refers to more than one layer?

Stratified (> 1)

What are the classifications of epithelial tissues based on the shape of cells?

Squamous, Cuboidal, Columnar

What shape are the cells in squamous epithelium?

Flattened cells

How does the width compare to the height in squamous epithelium?

Width > height

How do the nuclei compare to the flattened cells in squamous epithelium?

Nuclei taller than the flattened cells

Where do the nuclei bulge into in squamous epithelium?

Bulge into the lumen

What is difficult to see in squamous epithelium?

cytoplasm

How do the cells appear in terms of width and height in cuboidal epithelium?

Cells appear as high as they are wide

What shape are the nuclei in cuboidal epithelium?

Spherical nuclei

Where are the spherical nuclei positioned in cuboidal epithelium?

Centrally positioned

How do the cells compare in height and width in columnar epithelium?

Cells are taller than they are wide

What shape are the nuclei in columnar epithelium?

Oval nuclei

Where are the oval nuclei located in columnar epithelium?

Located near the base of the cells

What type of tissue are most epithelia adjacent to?

Vascular connective tissue

What does the adjacent vascular connective tissue provide to epithelia?

Nutrients and oxygen

What is the connective tissue that underlies the lining of organs in the digestive, respiratory, and urinary systems called?

Lamina Propria

What are the small evaginations from connective tissue into the epithelium called?

Papillae

What physical force are papillae subject to?

Friction

Where are papillae commonly found covering?

Covering of skin or tongue

What surface of the epithelial cell faces the lumen or the external environment?

Apical surface

What structures can be found on the apical surface?

Microvilli, cilia, stereocilia

What surface of the epithelial cell faces the sides of adjacent cells?

Lateral surface

What junctions are found on the lateral surface?

Tight junctions, adherens junctions, desmosomes, gap junctions

What surface of the epithelial cell attaches to the basement membrane?

Basal surface

What structures are associated with the basal surface?

Basement membrane, hemidesmosomes

What membrane is located between epithelia and connective tissue?

Basement Membrane

Under what microscope is the basement membrane visible only?

EM

What are the two layers of the basement membrane?

Dense layer and Clear layer

What type of collagen is a component of the basement membrane?

Type IV Collagen

What glycoprotein besides Type IV Collagen is a component of the basement membrane?

Laminin

What is integrin attached to in the basement membrane components?

Nidogen and perlecan

What are the two parts of the basement membrane?

Basal lamina and Reticular Lamina

What function of the basal lamina affects cell division and differentiation?

Cell regulation

What function of the basal lamina concentrates growth factors?

Binding

What two laminae combine to form the basement membrane?

Basal lamina + reticular lamina

Which structure is thicker than the basal lamina?

Basement Membrane

What components make up the basal lamina?

Lamina densa + adjacent layers

Under what microscope is the basal lamina seen only?

TEM

What structures provide adhesion and connection between cells?

Intercellular adhesions and junctions

By what membranes are intercellular adhesions and junctions exhibited?

Lateral membranes

What do intercellular adhesions and junctions control the flow of?

inter-cell material flow

What do intercellular adhesions and junctions provide channels for?

Communication

What type of junction forms a seal between adjacent cells?

Tight junction / occluding

What type of junction provides strong cell adhesion?

Adherens junction / anchoring

What type of junction provides communication?

Gap

What is another name for tight junctions?

Zonulae occludens

Where is the tight junction located relative to the cell?

apical part of the cell

What structure forms a band encircling each cell?

Tight junction

What two transmembrane proteins are responsible for the seal in tight junctions?

Claudin and occluding

What do tight junctions restrict the movement of at the apical cell surface?

Membrane lipids and proteins

What is another name for adherens junctions?

Zonula adherens

Where is the adherens junction located in relation to the tight junction?

Located below the tight junction

What junction encircles the epithelial cells and anchors the cell to its neighbors?

Adherens junction

What transmembrane proteins mediate the adherens junction?

Cadherins

In the presence of what molecule do cadherins bind to each other?

Ca(2+)

What do cadherins bind to using catenins?

Actin filaments

What junctions mediate intercellular communication?

Gap junctions

How do gap junctions appear structurally?

Shows as aggregated transmembrane protein complexes

What do gap junctions allow the direct transfer of from one cell to another?

Small molecules and ions

What is another name for desmosomes?

Macula adherens

What shape are desmosomes?

Disc shaped

What are desmosomes matched with at an adjacent cell surface?

Identical structures

What two proteins do desmosomes contain? \

Desmogleins and desmocollins

What provides adhesions for strength in desmosomes?

Cytokeratin

What junction resembles half of the desmosomes?

Hemidesmosomes

What do hemidesmosomes indirectly link to?

Cytokeratin

What are the intermediate filaments in hemidesmosomes rather than cadherins?

Integrins

What do integrins bind to in the basal lamina?

Laminin molecules

What is the purpose of specializations of the apical surface regarding area?

Increase cell surface area

What is the purpose of specializations of the apical surface regarding movement?

Move substances or particles bound to the epithelium

What are three examples of specializations of the apical surface?

Microvilli, Stereocilia, cilia

What specialization is specialized for absorption?

Microvilli

How are microvilli visible projecting into the lumen?

Visible as a brush like borders

What does each microvillus contain bundled within it?

Bundled actin filaments

What type of movements do microvilli undergo?

Dynamic myosin-based movements

What epithelial cells do stereocilia commonly line?

Male reproductive system epithelial cells

How do stereocilia compare to microvilli in length and motility?

Longer and less motile than microvilli

What do stereocilia facilitate?

Facilitates movement and absorption

How do cilia compare to microvilli in size and motility?

Long and highly motile, larger than microvilli

Which specific type of cilium is not motile?

Primary cilium

What is the primary cilium enriched with?

Receptors and signal transduction complexes

In what types of cells are primary cilia abundant?

Cuboidal or columnar cells

What assembly of internal arrays of microtubules do cilia contain?

9+2 assembly