MT 30 (LAB): EPITHELIAL TISSUE

• Reproduce rapidly

• Tightly packed

• Good barriers

• secretion, absorption, excretion, sensory reception, protection

What are the general features of epithelial tissue?

Cellularity, polarity, attachment, avascularity, innervation, high regeneration capacity

Characteristics of Epithelial tissue

What does Cellularity in epithelial tissue mean?

composed almost entirely of cells (with

some extracellular matrix and sometimes other

structures)

What is the significance of epithelial tissue being avascular?

Epithelial tissue lacks blood vessels and receives nutrients via diffusion from well-vascularized connective tissues.

What is the high regeneration capacity of epithelial tissue essential for?

It allows for rapid replacement of epithelial cells frequently damaged by abrasion.

What characterizes the polarity of epithelial tissue?

Epithelial tissue has specific top (apical surface) and bottom (basal surface) regions.

apical surface, basal surface, lateral surfaces

Polarities of an epithelial tissue

apical surface

exposed to the external environment or internal body space

basal surface

attached to underlying connective tissue

lateral surfaces

connected by intercellular junctions

Attachment

basal surface bound to the basement membrane

Innervation

lots of nerve endings

Basement layer, hemidesmosomes, Intercellular Junctions, Desmosomes

What are the Specialized structures of Epithelial Tissue?

How does the basement membrane relate to epithelial tissue?

It is the extracellular layer that attaches the basal surface of the epithelium to the connective tissue.

what are hemidesmosomes?

• found in some epithelial tissue

• basal cells anchored to the basement membrane with junctions

What role do intercellular junctions serve in epithelial tissues?

They connect lateral surfaces of epithelial cells and help maintain the integrity of the tissue.

What function does a tight junction serve?

• anchor cells to each other

• prevents substances from passing between cells, requiring materials to move through the cells.

• intestinal lining

intestinal lining

tights junctions are found in what part?

What function do adhering junctions serve?

• often deep to tight junctions

• Form all the way around a cell

• Support apical surface

• Allows passage between cells below the apical surface

What function does a desmosome serve?

• attach cells to each other

• bind epithelium together

• bind muscle cells

• resist shear forces

Physical protection, Selective permeability, Sensation, secretion

Functions of epithelial (PSSS)

Physical protection

protect exposed and internal surfaces from dehydration, abrasion, destruction

Selective permeability

act as gatekeepers to let some substances in and keep others out

secretion

contain glands that release sweat, scents, hormones, etc.

What is the difference between simple and stratified epithelium?

Simple epithelium has one cell layer thick, while stratified epithelium has more than one layer.

What are the general types of Epithelium?

Covering and lining epithelium, Glandular epithelium

Covering and lining epithelium

▪ epidermis of skin

▪ lining of blood vessels and ducts

▪ lining respiratory, reproductive, urinary and GI tract

lining of respiratory, reproductive, urinary and GI tract

Location of Covering and lining epithelium

Glandular epithelium

• originates from invaginated epithelial cells

• secreting portion of glands

• thyroid, adrenal, and sweat glands

thyroid, adrenal, and sweat glands

Glandular epithelium is found where?

Ectoderm, Endoderm, Mesoderm

Epithelium Germ Layers

oral and nasal mucosa, cornea epidermis, glands of the skin, mammary glands

Ectoderm is found in?

lining of respiratory and gastrointestinal tract, liver, pancreas

Endoderm is found in?

lining of the urogenital system, circulatory system, and body cavities lining

Mesoderm is found in?

Simple squamous epithelial tissue

Which epithelium type lines the lungs?

Endothelium

• a specific type of simple squamous epithelium lining the blood vessels

• stained with pararosaniline-toluidine blue (PT)

Secretion and absorption.

What is the function of simple cuboidal epithelium?

lining of the trachea and upper respiratory tract.

Where can you find ciliated pseudostratified columnar epithelial tissue?

Protection against abrasion.

What is the primary function of stratified squamous epithelium?

What are goblet cells?

Unicellular glands found in some epithelial tissues that secrete mucus.

What distinguishes keratinized from non-keratinized stratified squamous epithelium?

• Keratinized has a layer of keratin and is found in the skin;

• non-keratinized is found in moist areas like the mouth.

What is the role of transitional epithelium?

It stretches readily and permits distension, found in the urinary bladder.

Exocrine and endocrine glands

What types of glands can epithelial tissues form?

Parenchyma and stroma

What are the two components of a gland?

glandular epithelia

Parenchyma is aka?

connective tissue

stroma is aka?

What are unicellular glands?

Glands composed of a single cell, such as goblet cells.

Exocrine glands

▪ Most commonly found in digestive, respiratory, and urogenital

▪ Can be Unicellular or multicellular

▪ Secrete: mucous (e.g. salivary gland), serous (e.g pancreas), or mix (submandibular)

Unicellular or multicellular

Exocrine glands can be ___ or ___

digestive, respiratory, and urogenital

Exocrine glands is most commonly found in?

Multicellular exocrine glands

• Classified into

  • Simple glands have unbranched ducts

  • compound glands have branched ducts. (septa)

septa

Compound glands have branched ducts, aka?

Simple cuboidal epithelial tissue.

What type of epithelium lines the kidneys?

Ciliated pseudostratified columnar epithelium.

Which epithelial tissue type is found in the respiratory tract?

Digestive tract, small intestine, gallbladder, and excretory ducts.

In which parts of the body would you find simple columnar epithelium?

Absorption and secretion.

What is the main function of stratified cuboidal epithelium?

Describe the structure of simple squamous epithelium.

Single layer of flattened cells with disc-shaped nuclei.

Absorption, secretion, and propulsion of substances.

What is the primary function of simple columnar epithelium with cilia?

What does the term 'mesothelium' refer to?

The lining of body cavities which is derived from mesoderm.

What is the function of adhering junctions?

Support the apical surface and allow passage between cells.

Squamous, cuboidal, columnar and transitional

What are the classifications of epithelial tissue according to cell shape?

male reproductive tract

Where in the body can stratified columnar epithelium be found?

What is the key characteristic of transitional epithelium when relaxed?

Cells appear cuboidal.

What happens to transitional epithelium when it is stretched?

Cells become flattened and appear squamous.

Mucous membranes, serous membranes, and cutaneous membranes.

What are the main types of epithelial membranes?

Stratified squamous keratinized epithelial cells.

What types of cells make up the epidermis of the skin?

Describe the appearance of ciliated pseudostratified columnar epithelial cells.

They have nuclei at different levels and may contain cilia.

What is the importance of epithelial tissues in sensation?

They contain nerve endings that sense changes in the environment.

Glandular epithelium.

What type of epithelium is involved in secretion within glands?

Transitional epithelial cells.

What type of epithelial cells are found lining the urinary bladder?

What common function do glandular epithelial tissues serve?

Secretion of substances like hormones, sweat, and enzymes.

How is avascularity significant for epithelial tissue?

It relies on diffusion for nutrient and waste exchange due to lack of blood vessels.

What is the functionality of desmosomes in epithelial cells?

They bind cells to each other and resist shear forces.

digestive tract, gallbladder, and some gland ducts.

Where is simple columnar epithelium with goblet cells typically found?

Tight junctions.

What type of junction prevents intercellular passage of materials?

Kidney tubules.

Identify an example of a location where simple cuboidal epithelium is found.

Stroma.

What are the connective tissue components that support parenchyma in glands called?

Stratified squamous keratinized epithelium.

What tissue type forms the epidermis of the skin?

secretion and absorption.

What role does the cell type of cuboidal epithelium play in organs?

protect against abrasion and water loss.

What is the main function of keratinized stratified squamous epithelium?

secretion and absorption.

What is the function of the stratified columnar epithelium in the male reproductive tract?

How do epithelial cells exhibit high regeneration capacity?

They are rapidly replaced due to frequent damage or loss.

What is the appearance of the basal surface of epithelial cells?

It is attached to the underlying connective tissue by the basement membrane.

What is one function of epithelial cells in relation to environmental changes?

They sense and respond to changes in the environment.

Simple squamous epithelium.

Name a type of epithelium that provides filtration and passageway functions.

What do hemidesmosomes do within epithelial tissues?

• Anchor basal cells to the basement membrane.

How does the presence of cilia on epithelial cells affect their function?

Cilia help propel mucus or reproductive substances along the surface of the epithelium.

Why is it important for epithelial cells to be tightly packed?

To form effective barriers and control permeability.

small intestine

Where can you find the Simple columnar epithelial tissue?

Stratified squamous non-keratinized epithelial tissue

What epithelial tissue lines the mouth?

salivary glands, sweat glands

Where can you find the Stratified cuboidal epithelial tissue