[RAP0 21LAB] PRELIM: Lesson 5 Tissue Level & Epithelial Tissue

Tissue Level

• It is the second level of biological organization, following the cellular level and preceding the organ level.

• It is a group of similar cells working together to perform a specific function.

• In the human body, they are categorized into four main types.

4 Types of Tissues

• Epithelial Tissue

• Connective Tissue

• Muscle Tissue

• Nervous Tissue

Epithelial Tissue

• Covers body surfaces, lines cavities, and forms glands.

• Examples:

  • Skin (epidermis)

  • Lining of the digestive tract

  • Glandular tissue (sweat glands, salivary glands)

3 Examples of Epithelial Tissue

• Skin (epidermis)

• Lining of the digestive tract

• Glandular tissue (sweat glands, salivary glands)

6 Functions of Epithelial Tissue

• Protection – Shields underlying tissues from mechanical injury, pathogens, and dehydration.

• Absorption – Found in the digestive tract, where it absorbs nutrients.

• Secretion – Produces substances such as mucus, enzymes, and hormones (e.g., glandular epithelium).

• Excretion – Aids in removing waste products (e.g., kidney tubules).

• Filtration – Allows selective exchange of substances, such as in the kidneys.

• Sensation – Contains sensory receptors for touch, pressure, and temperature.

Protection

• Function of Epithelial Tissue

• Shields underlying tissues from mechanical injury, pathogens, and dehydration.

Absorption

• Function of Epithelial Tissue

• Found in the digestive tract, where it absorbs nutrients.

Secretion

• Function of Epithelial Tissue

• Produces substances such as mucus, enzymes, and hormones (e.g., glandular epithelium).

Excretion

• Function of Epithelial Tissue

• Aids in removing waste products (e.g., kidney tubules).

Filtration

• Function of Epithelial Tissue

• Allows selective exchange of substances, such as in the kidneys.

Sensation

• Function of Epithelial Tissue

• Contains sensory receptors for touch, pressure, and temperature.

Types of Epithelial Tissue

• Based on Cell Layers:

  • Simple Epithelium

  • Stratified Epithelium

  • Pseudostratified Epithelium

• Based on Cell Shape:

  • Squamous

  • Cuboidal

  • Columnar

Simple Epithelium

• Type of Epithelial Tissue Based on Cell Layers

• (Single layer of cells, found in areas involved in absorption, secretion, and filtration).

Stratified Epithelium

• Type of Epithelial Tissue Based on Cell Layers

• (Multiple layers of cells, providing protection in high-friction areas).

Pseudostratified Epithelium

• Type of Epithelial Tissue Based on Cell Layers

• (Appears stratified but consists of a single layer with varying cell heights).

Squamous

• Type of Epithelial Tissue Based on Cell Shape

• (Flat, thin cells, e.g., lung alveoli for gas exchange).

Cuboidal

• Type of Epithelial Tissue Based on Cell Shape

• (Cube-shaped cells, e.g., kidney tubules for absorption and secretion).

Columnar

• Type of Epithelial Tissue Based on Cell Shape

• (Tall, rectangular cells, e.g., lining of intestines for absorption).

Ciliated, Glandular, and Transitional Epithelium

3 Specialized Epithelial Tissue

Ciliated Epithelium

• Specialized Epithelial Tissue

• Contains cilia for movement of substances

• (e.g., respiratory tract)

Glandular Epithelium

• Specialized Epithelial Tissue

• Produces and secretes substances

• (e.g., sweat and salivary glands).

Transitional Epithelium

• Specialized Epithelial Tissue

• Found in the urinary bladder, allowing stretching.