Epithelial Tissue Flashcards
What are the four basic types of tissue?
- Epithelial tissue
- Connective tissue
- Muscle tissue
- Nervous tissue
What is the definition of epithelial tissue?
Epithelial tissue is a type of tissue that covers the body’s surfaces, lines internal cavities, and forms glands. It is composed of closely packed cells with little to no intercellular material.
What are the General Features and Functions of Epithelial Tissues:
- Features: Epithelial tissues are avascular (lack blood vessels), have a free surface, and are anchored to a basement membrane.
- Functions: They serve as a protective barrier, regulate the passage of substances, secrete and absorb materials, and provide sensory input.
What are the Classifications of Epithelial Tissues Based on Cell Layers and Cell Shape?
- Based on Layers: Epithelial tissues can be classified as simple (single layer), stratified (multiple layers) or pseudostratified (Single layer, but not all cells reach
surface. Appears layered, but isn’t.- Based on Shape: They can be categorised into - squamous (flat), cuboidal (cube-shaped), columnar (rectangular) cells, transitional (variety of shapes).
Where are Simple Squamous Epithelium found?
Found in the air sacs of the lungs (alveoli) and lining blood vessels.
Where are Simple Cuboidal Epithelium found?
Lines kidney tubules and various glands.
Where are Simple Columnar Epithelium found?
Found in the digestive tract, including the small intestine and stomach lining.
Where are Stratified Squamous Epithelium found?
Forms the outer layer of the skin (epidermis) and lines the oral cavity and oesophagus.
Where are Stratified Cuboidal and Columnar Epithelium found?
Rare, mainly found in ducts of certain glands.
Where are Pseudostratified Columnar Epithelium found?
Lines the respiratory tract.
Where is the Transitional Epithelium found?
Found in the urinary bladder and allows stretching.
What are the four functions of epithelial cells?
(i) Protection - Against: microbial infection, drying out,
harmful environments
(ii) Secretion - Of fluids e.g. sweat, saliva, hormones
(iii) Absorption - Of nutrients, fluids, chemicals
(iv) Excretion - Removal of waste products
Can nerves penetrate the layers of epithelial cells?
Yes
Can blood vessels penetrate the layers of cells?
No
How is oxygen and nutrients obtained by epithelial cells?
Diffusion
What links epithelial cells together?
Cell junctions (forms a functional unit)
Do epithelial cells have a great capacity for renewal?
Yes
What is the function of glandular epithelium?
Secretion
Where do the secretions of endocrine glands enter and what is the name of the secretions?
The interstitial fluid, then diffuse into the blood stream WITHOUT flowing through a duct. These secretions are HORMONES.
Give examples of endocrine glands?
The pituitary glands and adrenal glands.
What is the function of endocrine glands?
Regulating many metabolic and physiological activities to maintain homeostasis.
What is the function of exocrine glands?
Exocrine glands secrete their products INTO ducts that empty at the surface of off, covering and lining, epithelium or directly onto a free surface. The product of an exocrine gland may be released at the skin surface or into the lumen of a hollow organ.
Give examples of secretions from exocrine glands.
Examples include; mucus, perspiration, oil, earwax, milk, saliva and digestive enzymes.
Give examples of exocrine glands.
Exocrine glands include:
Sweat glands - produce perspiration to help lower body temperature
Salivary glands - secretes mucus and digestive enzymes.
