Epithelial Tissue Quiz

Epithelial Tissue Part 1

• Epithelial tissue is one of four basic tissues in the body
• The other three basic tissues are connective, nerve, and muscle tissue
• Epithelial tissue covers the external body surface and lines the internal body cavities and tubes
• Epithelial tissue is avascular; it obtains nutrients by diffusion from blood vessels in the underlying tissue
• Epithelial tissue is composed of cells closely attached by cell-to-cell junctions

Learning Objectives

• Differentiate between and compare the functions of 8 morphologically different types of epithelium
• Determine the general and specific characteristic features of the various epithelia of the body
• Differentiate between endothelium and mesothelium
• Understand the exception to simple squamous designation in lymph nodes and the spleen
• Identify how protective, secretory, excretory, lubricating, absorptive, and reproductive functions of epithelia contribute to individual health
• Identify and match locations of epithelia based on their specific functions
• Explain the functions and examples of the locations of apical, basal, and lateral surface modifications of epithelial cells
• Define microvilli, stereocilia, and cilia, and correlate their structure to function
• Identify the structure and functions of the basal and external laminae
• Name the different types of cell-to-cell and cell-to-matrix junctions and define their functions
• Identify the structural elements contributing to these junctions
• Define the elements of the cytoskeleton and correlate their distribution to their functions
• Define a gland, outline their morphological patterns, and state their general functions
• Classify specific glands in the body based on their morphological features
• List functional and morphological features of exocrine and endocrine glands, and cite specific examples
• Review functional and structural differences between mucous and serous glands
• Identify microscopic characteristics of mucous and serous glands
• Describe ultrastructural features of cells and other structures that make up the exocrine glands
• Differentiate between various modes of secretion of exocrine glands (e.g., merocrine, apocrine, holocrine)
• Histologically identify specific glands and match them to merocrine, apocrine, holocrine, endocrine, and exocrine classifications
• Relate ultrastructural appearance of a gland to its functions
• Identify serous and mucous membranes

Epithelial Tissue: Characteristics of Epithelial Cells

• Epithelial cells are arranged in sheets, one or multiple layers
• Sheets can be arranged as glands (secretory portions or parenchyma of glands)
• Attached by cell-to-cell junctions
• Exhibit three distinct surface domains (apical, lateral, and basal) with specific lipid and integral membrane protein properties identifiable by special techniques

Characteristics of Epithelial Cells (cont.)

• Basal surface of epithelial cells is attached to an underlying non-cellular basement membrane
• The basement membrane is a protein-polysaccharide structure visible with PAS stain
• In special situations, epithelial cells lack a free surface and are called epithelioids (e.g., islets of Langerhans, interstitial cells of Leydig)

Functions of Epithelium

• Epithelia have numerous functions, including physical protection, selective transport (diffusion, absorption, secretion), secretion, absorption, transportation, mechanical protection, and receptor function
• Examples of specialized epithelial functions include absorptive columnar epithelium in the intestines and secretory columnar epithelium in the stomach

Classification of Epithelium

• Classified by cell shape (squamous, cuboidal, columnar) and number of cell layers (simple, stratified)
• Additional specializations (cilia, keratin, goblet cells) also used for categorization

Epithelial Types:

• Simple squamous
• Simple cuboidal
• Simple columnar
• Stratified squamous
• Stratified cuboidal
• Stratified columnar
• Pseudostratified
• Transitional

Simple Squamous Epithelium

• It is one cell thick, with a shape where the width is greater than height
• Functions include diffusion and filtration
• Located in the walls of Bowman's capsule, respiratory spaces (alveoli), and lining blood/lymphatic vessels (endothelium), and body cavities (mesothelium)

Simple Cuboidal Epithelium

• One cell thick and cube-shaped
• Its function includes protection, absorption, and secretion
• It is found in glandular ducts, thyroid follicles, kidney tubules, and parts of the kidney's collecting ducts

Simple Columnar Epithelium

• This type is one cell thick and tall
• Functions include absorption and secretion. Types include ciliated and non-ciliated
• Ciliated varieties are found in the fallopian tubes and large bronchioles of the lungs. Those that are not ciliated (non-ciliated) types are found in the small intestine.

Stratified Squamous Epithelium

• Two or more cell layers
• Includes keratinized and non-keratinized subtypes
• The superficial layer composed of squamous cells
• Non-keratinized types line the oral cavity, pharynx, esophagus, and vagina
• Keratinized types are found in the epidermis of the skin

Stratified Cuboidal Epithelium

• Consists of more than one layer of cube-shaped epithelial cells
• It is found in the ducts of sweat glands and in larger ducts of exocrine glands
• Its function is barrier and protection.

Stratified Columnar Epithelium

• More than one layer of columnar cells, with columnar cells prominent in the uppermost layer
• It is located in the largest ducts of exocrine glands
• Functions as a barrier and conduit.

Pseudostratified Epithelium

• Gives a false appearance of layering due to varying cell heights, but it is actually simple
• It has various subtypes: non-ciliated, ciliated, and stereocilia (with stereocilia located in the reproductive organs)
• Common location is upper respiratory tract, seminal vesicles, and epididymis

Transitional Epithelium or Urothelium

• Specialized stratified epithelium; its function and cell shape and numbers of cell layers change depending on whether the bladder is full or empty
• It is found in the renal calyces, ureters, urinary bladder, and proximal urethra

Mucous Membranes

• Lines cavities that open to the exterior, such as the digestive, respiratory, and urogenital tracts
• Consist of epithelial tissue, basal lamina, and underlying connective tissue
• May have glands that secrete mucus

Serous Membranes

• Lines closed cavities in the body, such as the peritoneal and pleural cavities
• Consists of simple squamous epithelium (mesothelium), a basal lamina, and underlying connective tissue
• Do not contain glands

Basement Membrane

• Synthesized by epithelium; components are secreted and assembled extracellularly.
• Supports and compartmentalizes tissue via structural attachment to epithelium
• Involved in filtration, tissue scaffolding for regeneration, and separation of tissues
• Characterized by two basic layers, lamina densa, and lamina lucida (or rara)

Squamous Cell Carcinoma

• Maligned squamous cells arise due to abnormal squamous epithelium formation
• A diagnosis is facilitated by large amounts of keratin produced in characteristic swirls and nests

Test your knowledge on epithelial tissue, its types, functions, and characteristics with this quiz. Explore concepts related to cell types, basement membranes, and gland distinctions. Perfect for students of histology or anatomy.