Epithelial Tissue Overview

Epithelial tissue lines internal closed cavities and body tubes that connect to the external environment, such as the gastrointestinal, respiratory, and genitourinary tracts.
Composed of closely packed cells with minimal intercellular material, differentiating it from connective tissue, which has a substantial extracellular matrix.
Avascular, relying on diffusion from neighboring tissues for nutrition.

Simple Epithelial Tissue: Composed of a single layer of cells, facilitating easy absorption and diffusion.
Stratified Epithelial Tissue: Consists of multiple layers, providing protection against mechanical stress.
Pseudostratified Epithelial Tissue: Appears layered due to varying cell heights but is a single layer.
Transitional Epithelial Tissue: Specialized to stretch and accommodate fluctuating volumes, found in the bladder.

Absorption: Key function in structures like the intestinal lining, where morphology often includes cuboidal or columnar cells.
Secretion: Present in the secretory portions of glands, which are categorized into exocrine (secreting into ducts) and endocrine (secreting into blood).
Filtration: Seen in kidney structures.
Diffusion: Occurs in capillaries for gas exchange.
Sensory Reception: Utilized in neuroepithelial tissue, which is found in sensory organs such as the ears, eyes, and nose.
Contractile Function: Observed in myoepithelial cells, aiding in the expulsion of glandular secretions.

Tight Junctions: Prevent passage of molecules between cells, maintaining polarity.
Adherent Junctions: Provide strength and unite epithelial cells.
Gap Junctions: Allow communication between adjacent cells via small channels.

Microvilli: Increase surface area for absorption, commonly found in the intestines.
Stereocilia: Long microvilli for sensory functions.
Cilia: Hair-like structures that help move substances across epithelial surfaces.

Epithelial tissue lines internal closed cavities and body tubes that connect to the external environment, such as the gastrointestinal, respiratory, and genitourinary tracts.
Composed of closely packed cells with minimal intercellular material, differentiating it from connective tissue, which has a substantial extracellular matrix.
Avascular, relying on diffusion from neighboring tissues for nutrition.

Simple Epithelial Tissue: Composed of a single layer of cells, facilitating easy absorption and diffusion.
Stratified Epithelial Tissue: Consists of multiple layers, providing protection against mechanical stress.
Pseudostratified Epithelial Tissue: Appears layered due to varying cell heights but is a single layer.
Transitional Epithelial Tissue: Specialized to stretch and accommodate fluctuating volumes, found in the bladder.

Absorption: Key function in structures like the intestinal lining, where morphology often includes cuboidal or columnar cells.
Secretion: Present in the secretory portions of glands, which are categorized into exocrine (secreting into ducts) and endocrine (secreting into blood).
Filtration: Seen in kidney structures.
Diffusion: Occurs in capillaries for gas exchange.
Sensory Reception: Utilized in neuroepithelial tissue, which is found in sensory organs such as the ears, eyes, and nose.
Contractile Function: Observed in myoepithelial cells, aiding in the expulsion of glandular secretions.

Tight Junctions: Prevent passage of molecules between cells, maintaining polarity.
Adherent Junctions: Provide strength and unite epithelial cells.
Gap Junctions: Allow communication between adjacent cells via small channels.

Microvilli: Increase surface area for absorption, commonly found in the intestines.
Stereocilia: Long microvilli for sensory functions.
Cilia: Hair-like structures that help move substances across epithelial surfaces.