The tissue level of organization - Cell shape and number of layers determine the classification of epithelia

23 important questions on The tissue level of organization - Cell shape and number of layers determine the classification of epithelia

What are the two categories epithelia can be sorted in?

  • The cell shape
  • The number of cell layers

What are the possible categories when talking about cell layers?

  • Simple
  • Stratified

What is a transitional epithelium?

A transitional epithelium is an unusual stratified epithelium because its cells can change between being squamous and cuboidal in shape.
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What is keratinized and nonkeratinized?

Keratinized means that an epithelium is though and water resistant. This happens when mechanical stress and dehydration are potential problems. The superficial layers of epithelial cells are packed with filaments of the protein keratin.
A nonkeratinized stratified squamous epithelium resists abrasion, but will dry out and deteriorate unless kept moist.

Where are simple cuboidal epithelia located?

In ducts and secretory portions of small glands and in kidney tubules.

What is the function of a stratified cuboidal epithelia?

Protection, secretion, and absorption.

Where do you find stratified cuboidal epithelia?

Stratified cuboidal epithelia are relatively rare.

Where do you find a simple columnar epithelium?

Cilliated tissues including the bronchi, uterine tubes, and uterus + smooth tissues in the digestive tract and bladder

What is pseudostratified columnar epithelium?

A pseudostratified columnar epithelium is a columnar epithelium that includes several types of cells with varying shapes and functions. It seems to be stratified because the different types of cell shapes make it look like there are more layers. However all the cells contact the basal membrane.

Where do you find pseudostratified columnar epithelia?

Cilliated tissue lines the trachea and much of the upper respiratory tract.

Where do you find stratified columnar epithelia?

The male urethra and the ducts of some glands.

What are glandular epithelia?

Glandular epithelia are epithelia that are specialized for secretion.

Where does an endocrine gland release its secretions? What about an exocrine gland?

An endocrine gland releases its secretion into the blood. An exocrine gland releases its secretions directly onto an epithelial surface or into passageways called ducts that open onto an epithelial surface.

What are the three ways to classify an exocrine gland?

  • The structure
  • The way of secretion
  • What the products are

What is merocrine secretion?

In merocrine secretion, the product is released from an exocrine cell by secretory vesicles through exocytosis. This is the most common method of exocrine secretion.

What is apocrine secretion?

Apocrine secretion from an exocrine cell involves the loss of cytoplasm as well as the secretory product. The apical portion of the cytoplasm becomes packed with secretory vesicles and is then shed.

What is holocrine secretion?

Holocrine secretion destroys the gland cell. During holocrine secretion, a superficial cell in a stratified glandular epithelium becomes packed with secretory vesicles and then burst, releasing the secretion, but killing the cell.

Identify the three cell shapes characteristic of epithelial cells.

  • Squamous (thin and flat)
  • Cuboidal (box shaped)
  • Columnar (tall and slender)

When classifying epithelial tissue, one with a single layer of cells is called ____, whereas one with multiple layers of cells is called ____.

Simple - stratified

Viewed with a light microscope, a tissue appears as a simple squamous epithelium. Can this be a sample of the skin surface? Why or why not?

No, this is not a sample from the skin surface. A simple squamous epithelium does not provide enough protection against infection, abrasion, or dehydration. The skin surface has a stratified squamous epithelium.

Why do the pharynx, esophagus, anus, and vagina have a similar stratified epithelial organization?

All these regions are subject to mechanical trauma and abrasion - by food (pharynx and esophagus), by feces (anus), and by intercourse or childbirth (vagina).

Name the two primary types of glandular epithelia.

  • Endocrine
  • Exocrine


The secretory cells of sebaceous glands fill with vesicles and then rupture releasing their contents. Which method of secretion is this?

Holocrine secretion.

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