The Cell; Epithelium and Glands

The study of Cells is called?

Cytology

The study of Tissues is called?

histology

What 3 structures of the cell can only be identified by a Light Microscope?

Cytoplasm, Nucleus & Nucleolus

Can the Cell Membrane be identified by a light Microscope?

No

What are the 4 Basic Types of Tissues?

Epithelial, Connective, Muscle & Nervous

Which type of tissue supports and protects Tissues/Organs?

Connective Tissue

T/F The Epithelium is made up of aggregated polyhedral cells?

True

T/F The epithelium has a large amount of Extracellular matrix?

False

Give an example of an epithelial tissue that serves as a protective barrier.

Skin or oral mucosa.

How does the skin act as a protective barrier?

By forming a physical barrier against external threats and preventing dehydration.

What is the role of oral mucosa as a barrier?

To protect the underlying tissues of the mouth from mechanical damage, chemical irritants, and pathogens.

Where does absorption primarily occur in the digestive system?

Small intestine.

What types of substances are absorbed by the small intestine's epithelium?

Nutrients and water.

Describe the process of nutrient absorption in the small intestine.

The epithelial cells lining the small intestine have micro-villi that increase surface area for absorption. These cells transport nutrients from the lumen of the intestine into the bloodstream.

What is the function of epithelial tissue in secretion?

To produce and release substances like enzymes, mucus, and hormones.

Provide two examples of secretions produced by epithelial tissue.

Digestive enzymes + mucus.

What type of epithelium secretes digestive enzymes?

Intestinal epithelium.

What type of epithelium secretes mucus, and where is it located?

Respiratory epithelium, located in the respiratory tract.

Why is lubrication important in the body?

To reduce friction between moving surfaces, preventing damage.

What epithelial tissue provides lubrication for abdominal organs?

Mesothelium.

What is the mesothelium, and what is its function regarding lubrication?

It is the outermost covering of abdominal organs that secretes tissue fluid for lubrication.

What is the role of epithelial tissue in the male and female reproductive tracts?

To provide a surface for gamete transport, protection, and secretion of fluids.

What is the function of epithelial tissue in transport?

To allow the passage of small molecules and ions.

What types of substances are transported across epithelial tissue?

Small molecules + Ions

Can substances move in both directions across this type of tissue?

Yes

How does epithelial tissue facilitate the passage of ions?

Through selective permeability and transport mechanisms within the epithelial cells.

What is the primary function of epithelial tissue acting as a barrier?

To prevent the passage of harmful substances, pathogens, and excessive fluid loss.

Give an example of an epithelial tissue that serves as a protective barrier.

Skin or oral mucosa.

How does the skin act as a protective barrier?

By forming a physical barrier against external threats and preventing dehydration.

What is the role of oral mucosa as a barrier?

To protect the underlying tissues of the mouth from mechanical damage, chemical irritants, and pathogens.

Where does absorption primarily occur in the digestive system?

Small intestine.

What types of substances are absorbed by the small intestine's epithelium?

Nutrients and water.

Describe the process of nutrient absorption in the small intestine.

The epithelial cells lining the small intestine have microvilli that increase surface area for absorption. These cells transport nutrients from the lumen of the intestine into the bloodstream.

Provide two examples of secretions produced by epithelial tissue.

Digestive enzymes and mucus.

What type of epithelium secretes digestive enzymes?

Intestinal epithelium.

What type of epithelium secretes mucus, and where is it located?

Respiratory epithelium, located in the respiratory tract.

Why is lubrication important in the body?

To reduce friction between moving surfaces, preventing damage.

What epithelial tissue provides lubrication for abdominal organs?

Mesothelium.

What is the mesothelium, and what is its function regarding lubrication?

It is the outermost covering of abdominal organs that secretes tissue fluid for lubrication.

What is the function of the fluid secreted by the mesothelium?

To reduce friction between abdominal organs.

Where are epithelial tissues found in relation to reproduction?

Linings of male and female reproductive tracts.

What is the role of epithelial tissue in the male and female reproductive tracts?

To provide a surface for gamete transport, protection, and secretion of fluids.

Describe the epithelial lining of the reproductive tracts.

The epithelial lining varies depending on the specific location within the reproductive tract, but it generally facilitates the movement and protection of gametes.

What is the function of epithelial tissue in transport?

To allow the passage of small molecules and ions.

What types of substances are transported across epithelial tissue?

Small molecules and ions.

Can substances move in both directions across this type of tissue?

Yes, in either direction.

How does epithelial tissue facilitate the passage of ions?

Through selective permeability and transport mechanisms within the epithelial cells.

What does "avascular" mean in the context of epithelial tissue?

No blood vessels.

How do epithelial tissues obtain nutrients and oxygen?

Via diffusion from neighboring blood vessels located in the ECM and connective tissue.

What does "polarity" mean in epithelial tissue?

That the tissue has several domains with specific, varying characteristics.

What are the three poles or surfaces of polarized epithelial tissue?

Apical pole + basal pole + lateral pole/surface.

Where is the apical pole located?

Faces the opposite space, usually the lumen.

Where is the basal pole located?

In contact with the ECM and connective tissue.

Where is the lateral pole/surface located?

In contact with adjacent cells.

What is the basement membrane?

A thin extracellular sheet of macromolecules.

Where is the basement membrane located in relation to epithelial tissue?

All basal portions of epithelia lie on a basement membrane.

What is the role of the basement membrane in nutrient and oxygen transport?

All nutrients and oxygen need to pass through the basement membrane.

What are the functions of the basement membrane?

1) Acts as a filter, 2) Aids in epithelial repair and regeneration

3) Maintains cellular functions (endocytosis, signal transduction, cell-to-cell interactions, polarity, etc.),

4) Provides structural support

5) Attaches epithelia to underlying connective tissue.

What are the two components of the basement membrane?

Basal and Reticular lamina.

Which component of the basement membrane is electron-dense and closest to the basal portion of the cell?

Basal lamina.

Which component of the basement membrane is more diffuse and fibrous?

Reticular lamina.

What is the difference between basal lamina and basement membrane?

Basal lamina is a component of the basement membrane and can only be seen ultrastructurally, while the basement membrane can be seen via light microscopy.

What is the Main Intermediate Filament of Epithelial tissues?

Keratin

What is another name for an occluding or tight junction?

Zonula Occludens.

Where are tight junctions located in relation to the cell?

At the most apical portion.

What is the purpose of tight junctions being located at the apical portion?

To ensure all molecules enter or exit the cell via the transcellular pathway.

What is the difference between the transcellular and paracellular pathway?

Transcellular goes into the cell, paracellular goes in between cells.

What transmembrane proteins are involved in tight junctions?

Claudin and occludin.

What bacterial food poisoning is associated with claudin?

Clostridium perfringens.

How does Clostridium perfringens affect tight junctions?

It elaborates an enterotoxin that binds with claudin, disrupting the tight junction.

What are the symptoms of Clostridium perfringens food poisoning?

Diarrhea, due to tissue fluid entering the intestinal lumen via the paracellular pathway.

What gastric condition is associated with disrupted tight junctions?

Gastric ulcers by Helicobacter pylori.

How does Helicobacter pylori disrupt tight junctions?

It binds the extracellular domains of tight-junction proteins and inserts a protein into these cells, disrupting signaling.

What is another name for an adherens junction?

Zonula Adherens.

Where are adherens junctions located in relation to tight junctions?

Immediately below tight junctions.

What transmembrane proteins are involved in adherens junctions?

Cadherin and catenin.

What ion is required for cadherin function?

Calcium (Ca2+).

What is another name for a desmosome?

Macula Adherens. (Look like “Spot Welds”)

What is the shape of a desmosome?

Like a "spot-weld."

What transmembrane proteins are involved in desmosomes?

Desmoglein and desmocollin (cadherin family).

What is the function of desmosomes?

To provide stability to cells, especially those under shearing stress.

What medical condition is associated with faulty desmosome function?

Blistering skin conditions, such as Pemphigus vulgaris.

What causes Pemphigus vulgaris?

Autoimmune reactions against specific desmogleins.

What is another name for a gap junction?

Nexus.

What transmembrane protein is involved in gap junctions?

Connexin.

How many connexins form a connexon?

6.

How are the gaps (channels) formed in gap junctions?

By paired connexons between cells.

What is the function of gap junctions?

To allow small molecules and nutrients to pass selectively between cells.

What size molecules can pass through gap junctions?

Molecules less than 1.5nm in diameter.

Why are gap junctions important?

They allow cells to function as a unit.

Give an example of where gap junctions are important for coordinated function.

Heart muscle (contracting as a single unit) and abdominal organs (rhythmic contractions).

What is the meaning of "hemi" in hemidesmosome?

Half.

What transmembrane protein is involved in hemidesmosomes?

Integrins.

What molecule does integrin form cross-links with in hemidesmosomes?

Laminin.

What is the function of hemidesmosomes?

Anchors cell to basal portions.

What medical condition is associated with faulty hemidesmosomes?

Epidermolysis bullosa.

What are the characteristics of Epidermolysis bullosa?

Blisters even with minimal friction, severe pain due to exposed raw skin, and prone to infections.

How do focal adhesions resemble hemidesmosomes?

Both involve Integrins and anchor cells to basal portions.

How do focal adhesions differ from hemidesmosomes?

Focal adhesions are more numerous and smaller.

T or F? Simple cuboidal epithelium allows the passive transport of gas, fluids, nutrients, and metabolites between cells and organs. (SQ1LE12025)

False.

Simple squamous epithelium is responsible for the passive diffusion and transport of fluids, nutrients, and metabolites across capillary walls to surrounding cells. In particular, the single thin

epithelium in the alveolar sacs allows the rapid exchange of gases

during breathing.

On the other hand, the simple cuboidal epithelium’s primary

function is to increase absorption by having a greater surface area

as compared to the simple squamous epithelium.