Epithelial Tissue and blood composition

What are epithelial tissues? give function, structure and examples

Function:

Covers and protects body surfaces

Lines internal organs, cavities, and ducts

Forms glands (e.g., sweat, salivary, and endocrine glands)

Structure:

Made up of closely packed cells with minimal space between them

Arranged in continuous sheets (single or multiple layers)

Has a free (apical) surface and a bottom (basal) surface attached to a basement membrane

Avascular (no blood supply), so it relies on nearby connective tissue for nutrients

Examples:

Skin surface (epidermis)

Lining of the mouth, stomach, intestines, and blood vessels

Glandular tissues (e.g., thyroid gland, sweat glands)

What are the types of epithelial tissue

simple, stratified, pseudostratified

Simple Squamous Epithelium

give the function, location, shape

Shape: Flat, thin cells.

Location:

Alveoli of lungs (for gas exchange).

Lining of blood vessels and heart (endothelium).

Serous membranes (mesothelium) in body cavities.

Function: Diffusion, filtration, and secretion of serous fluid.

Simple Cuboidal Epithelium

Shape: Cube-shaped cells.

Location:

Kidney tubules.

Ducts of glands (e.g., salivary and thyroid glands).

Surface of ovaries.

Function: Absorption and secretion.

Simple Columnar Epithelium

Shape: Tall, column-like cells, often with microvilli or cilia.

Location:

Lining of the stomach and intestines (non-ciliated).

Fallopian tubes and parts of the respiratory tract (ciliated).

Function: Absorption, secretion (e.g., mucus), and movement of substances.

Stratified Squamous Epithelium

Shape: Surface cells are flat; deeper layers may vary in shape.

Location:

Skin (keratinized).

Mouth, esophagus, and vagina (non-keratinized).

Function: Protection against abrasion, pathogens, and water loss.

Stratified Cuboidal Epithelium

Shape: Two or more layers of cube-shaped cells.

Location:

Ducts of sweat glands.

Mammary and salivary glands.

Function: Protection and secretion.

Stratified Columnar Epithelium

Shape: Column-like surface cells with irregularly shaped basal cells.

Location:

Male urethra.

Large ducts of some glands.

Function: Protection and secretion.

Pseudostratified Columnar Epithelium

Shape: Cells of varying heights, often ciliated, with nuclei at different levels.

Location:

Trachea and upper respiratory tract (ciliated, with goblet cells).

Parts of the male reproductive tract (non-ciliated).

Function: Secretion (mucus) and movement of particles.

Transitional Epithelium (Specialized for stretching)

Shape: Cells can change shape (from cuboidal to squamous).

Location:

Urinary bladder.

Ureters.

Part of the urethra.

Function: Allows stretching and distension.

what is blood composed of?

give percentages

Water (90-92%)

Plasma Proteins (7-8%)

Other Solutes

Albumin

maintains osmotic pressure and transports substances.

Globulins

involved in immune responses (antibodies).

Fibrinogen

essential for blood clotting.

what are the other solutes in the blood

Electrolytes (e.g., Na⁺, K⁺, Cl⁻, Ca²⁺)

Nutrients (glucose, amino acids, lipids)

Hormones

Gases (O₂, CO₂)

Waste products (urea, creatinine)