Epithelial Tissue Characteristics Quiz

General Characteristics of Epithelium

• Epithelial tissue may be ectodermal, endodermal, or mesodermal in origin.
• It is formed mainly of cells with few intercellular substances.
• The cells rest on a basement membrane.
• Epithelial tissue is avascular (no blood or lymphatic vessels penetrate it).
• It is highly innervated.
• It has a high power of regeneration.

Types of Epithelium

• Surface epithelium
• Glandular epithelium
• Neuro-epithelium
• Myo-epithelium

Simple Epithelium

• Formed of a single layer of cells
• Types:
  • Simple squamous epithelium
  • Simple cubical epithelium
  • Simple columnar epithelium
  • Simple columnar ciliated epithelium
  • Pseudo-stratified columnar epithelium
  • Pseudo-stratified columnar ciliated epithelium

Simple Squamous Epithelium

• Formed of a single layer of flat cells with flat nuclei
• Site: lining heart and blood vessels, lining serous membranes, lining lung alveoli, Bowman's capsule, and thin loop of Henle in the kidney
• Function: acts as a thin, smooth surface facilitating the flow of fluids, easy movement, gas exchange, filtration, and diffusion

Simple Cubical Epithelium

• Formed of a single layer of cube-like cells with central rounded nuclei
• Site: secretory units (thyroid follicle, secretory acini of salivary glands, pancreas, and sweat gland), convoluted tubules of kidney
• Function: responsible for secretion or reabsorption

Simple Columnar Epithelium

• Formed of a single layer of tall cells with basal oval nuclei
• Site: stomach, intestine, convoluted tubule of the kidney
• Function: secretion or absorption

Simple Columnar Ciliated Epithelium

• Formed of a single layer of tall cells with basal oval nuclei and cilia on the surface
• Site: uterus, fallopian tube, bronchioles of lung
• Function: the cilia beat in one direction to move substances

Pseudo-Stratified Columnar Epithelium

• Formed of a single layer of crowded columnar cells with nuclei at different levels
• Site: large ducts of salivary glands, upper part of male urethra
• Function: no specific function mentioned

Pseudo-Stratified Columnar Ciliated Epithelium

• Formed of a single layer of crowded columnar cells with nuclei at different levels and cilia on the surface
• Site: respiratory system (trachea, bronchi)
• Function: the cilia beat in one direction to remove dust and foreign substances

Stratified Epithelium

• Formed of multiple layers of cells
• Types:
  • Stratified squamous epithelium
  • Stratified cuboidal epithelium
  • Stratified columnar epithelium
  • Stratified columnar ciliated epithelium
  • Transitional epithelium

Stratified Squamous Epithelium

• Formed of multiple layers of cells with a flat surface layer
• Site: skin, oral cavity, cornea, vagina
• Function: protection

Stratified Columnar Epithelium

• Formed of multiple layers of cells with a columnar surface layer
• Site: conjunctiva of the eye, male urethra, large ducts of glands
• Function: no specific function mentioned

Stratified Columnar Ciliated Epithelium

• Formed of multiple layers of cells with a columnar surface layer and cilia
• Site: fetal esophagus, soft palate
• Function: no specific function mentioned

Stratified Cuboidal Epithelium

• Formed of 2-3 layers of cuboidal cells
• Site: ducts of sweat glands
• Function: no specific function mentioned

Transitional Epithelium

• Site: urinary system (ureter and urinary bladder)
• Function: allows for stretching and compression of the bladder
• Histological picture in empty bladder: 5-8 layers of cells with a non-clear, non-wavy basement membrane
• Histological picture in full bladder: 2-3 layers of flat cells due to gliding of cells over each other by mucous-like intercellular substance

Glandular Epithelium

• Formed of epithelial cells modified to give secretion
• Classification:
  • Presence or absence of ducts: exocrine, endocrine, or mixed glands
  • Number of cells: unicellular or multicellular
  • Mode of secretion: merocrine, apocrine, or holocrine
  • Type of secretions: serous, mucous, fatty, waxy, or watery
  • Shape of secretory part: tubular, alveolar, or tubuloalveolar

Neuro-Epithelium

• Definition: specialized type of epithelial tissue formed of epithelial cells modified to receive stimuli
• Consists of: hair cells, tall supporting cells, and basal cells
• Site: taste buds in tongue, olfactory epithelium in nose, organ of Corti in ear
• Function: sensation

Myo-Epithelium

• Definition: specialized type of epithelial tissue formed of epithelial cells modified to be contractile
• Site: present around secretory cells in exocrine glands (salivary and mammary gland)
• Function: contraction helps secretory cells to squeeze and evacuate secretion

Functions of Epithelium

• Protection
• Secretion
• Absorption
• Sensation
• Reproduction
• Excretion

Test your knowledge of the general histological characters of epithelial tissue, including its origin, composition, and different types such as surface epithelium, neuroepithelium, myoepithelium, and glandular epithelium.