Epithelial Tissue and Glands Quiz

Epithelium and Glands

• Epithelial tissue covers the body's exterior surfaces and lines its internal closed cavities.
• It forms the secretory portion of glands and their ducts.
• Epithelial tissue is also part of the receptors for certain sensory organs.
• Epithelial tissue lacks blood vessels (avascular).

Learning Outcomes

• Understand the characteristics of different types of body epithelia.
• Compare and contrast the functions of various types (8+).
• Recognize glands as clusters of epithelial cells for specific functions (e.g., secretion).
• Define the structural and functional distinctions between mucous and serous glands.
• Describe methods of exocrine gland secretion (merocrine, apocrine, holocrine).

Four Basic Types of Tissues

• The four main tissue types are epithelial, connective, muscle, and nervous tissue.
• Images of each tissue type are provided for visual recognition.

Epithelial Tissue

• Epithelium covers external surfaces of the body and internal cavities.
• It lines internal closed cavities and forms glands.
• Epithelium constitutes receptors in certain sensory organs.

Epithelium

• Cells in epithelium are tightly packed in sheets.
• Cells have characteristic junctions (complexes).
• They have distinct domains for apical (free), lateral, and basal regions.
• Epithelial cells rest on a basement membrane (basal lamina).

Epithelium-Function

• Epithelium can function as a transport system through motile cilia (e.g., trachea, bronchi).
• It receives sensory stimuli (e.g., neuroepithelia, taste buds, retina, smell, hearing).
• It participates in lubrication (mucous, serous fluid).
• It carries out excretory functions (e.g., blood filtration, urine, sweat).
• Epithelial cells support reproductive functions (e.g., sex cells from ovary & testes).

Epithelium-Classification

• Epithelial tissue is classified by cell arrangement and shape (not by function).
• Simple epithelium consists of a single layer of cells.
• Stratified epithelium consists of two or more cell layers.
• Types include squamous (flattened), cuboidal (cube-shaped), and columnar (elongated).

Epithelium-Classification of Cells (Squamous)

• Squamous cells are flattened, with width greater than height.
• Simple squamous epithelium lines blood vessels, Bowman's capsule (kidney), and respiratory spaces (lung).
• Function includes exchange, barrier & lubrication (CNS)

Epithelium-Classification of Cells (Cuboidal)

• Cuboidal cells have approximately equal width, depth, and height.
• Simple cuboidal epithelium is found in follicle walls (thyroid), kidney tubules (collecting ducts), and ovarian surfaces.

Epithelium-Classification of Cells (Columnar)

• Columnar cells have height exceeding width.
• Simple columnar epithelium lines the intestinal tract (stomach to rectum), uterus, and cervix, and gall bladder.
• Functions include absorption, secretion, and barrier formation.

Epithelium-Classification of Cells (Pseudostratified)

• Pseudostratified epithelium gives a stratified appearance but all cells rest on the basal lamina.
• It is found in respiratory tracts (trachea, bronchi).
• It includes cilia for movement.

Epithelium-Classification of Cells (Transitional)

• Transitional epithelium is stratified tissue, adapting to distension.
• It lines the urinary bladder, parts of the urethra, and renal calyces.

Epithelium-Classification of Cells (Stratified Squamous)

• Multiple layers of squamous cells forms the epidermis, oral cavity lining, and vaginal lining.
• Keratinized type is resistant to abrasion.
• Non-keratinized type lines wet surfaces.

Glands

• Glands are composed of epithelial cells.
• Exocrine glands secrete into ducts or onto free epithelial surfaces (e.g., sweat, saliva, digestive enzymes).
• Endocrine glands secrete hormones directly into the bloodstream (e.g., hormones for homeostasis).
• Paracrine glands secrete into extracellular space

Methods of Glandular Secretion (Merocrine)

• Merocrine secretion is most common.
• Vesicles release products into ducts.
• Sweat glands are an example

Methods of Glandular Secretion (Apocrine)

• Apocrine cells release products by pinching a portion of the cell.
• Smelly sweat is an example

Methods of Glandular Secretion (Holocrine)

• Holocrine secretion involves cell death and rupture.
• The entire cell becomes the secretion (sebaceous glands, oil production).

Epithelial Regeneration

• Certain epithelia (e.g., epidermis, intestinal) are continually recycled.
• Inappropriate cell division stimulation can cause tumors.
• Carcinomas are malignant tumours of epithelial origin; adenocarcinomas are glandular.

MCQ – Selected Questions

• Transitional epithelium lines the urinary bladder.
• A lesion in the trachea's innermost layer would primarily affect the pseudostratified columnar epithelium.

Test your knowledge on epithelial tissue and its functions in the body. This quiz covers various types of epithelia, their characteristics, and the roles of glands in secretion. You'll also explore distinctions between mucous and serous glands, as well as exocrine gland secretion methods.