Epithelial Tissue Overview

Tissues

• A tissue is a group of similar cells working together to perform a specific function within an organism.
• There are four main types of tissue: epithelial, muscle, connective, and nervous.

Epithelial Tissue

• Covers the surfaces of the body and lines body cavities.
• Provides barriers between internal and external environments.
• Specializes in secretion and absorption.
• Protects organisms from microorganisms, injury, and fluid loss.
• Excretes waste products, such as sweat from the skin.
• Epithelial tissue is classified into simple and stratified based on cell layers.
  • Simple epithelia: single layer of cells.
  • Stratified epithelia: multiple layers of cells.
• Three main types of epithelial tissues based on cell shape: squamous, cuboidal, and columnar.

Simple Squamous Epithelium

• Thin and flat cells.
• Elliptically shaped.
• Cells lie on a basement membrane.
• Found in capillaries and alveoli (in lungs).
• Responsible for diffusion.
• Thin structure allows for movement of substances across the cells.

Stratified Squamous Epithelium

• Found in the skin.
• Provides protection against damage.

Cuboidal Epithelium

• Cube-like in structure.
• May have microvilli on the surface to aid absorption.
• Located in kidney tubules and glands.
• Serves a protective function against bacteria and wear and tear.

Columnar Epithelium

• Elongated cells with nuclei located at the base.
• Cells are connected by tight junctions.
• Located in the digestive tract and reproductive organs.
• Main function is protection against bacterial infections.
• Can secrete mucus to protect the surface from damage.

Connective Tissue

• Provides support, connects, or separates different types of tissues and organs in the body.
• Is composed of cells, fibers, and extracellular matrix.

Functions of Connective Tissue

• Binding of organs.
• Support.
• Physical protection.
• Immune protection.
• Movement.
• Storage.
• Heat production.
• Transport.

Types of Connective Tissue Cells

• Fibroblasts: produce fibers and ground substance that form the matrix of the tissue.
• Macrophages: large phagocytic cells that engulf and destroy bacteria, other foreign particles, or dead cells of the body.

Specialized Connective Tissues

• Tendons: attach muscles to bones.
• Ligaments: join bones together at joints.
• Blood: does not have an extensive extracellular matrix.

Components of Blood

• Plasma: the liquid portion of blood.
• Red Blood Cells (RBCs): responsible for oxygen transport.
• Platelets: involved in blood clotting.
• White Blood Cells (WBCs): part of the immune system.

Connective Tissue Fibers

• Collagenous fibers: made of collagen, tough, flexible, and resist stretching.
• Reticular fibers: thin collagen fibers coated with glycoprotein.
• Elastic fibers: thinner than collagenous fibers, made of elastin, and provide elasticity.

Adipose Tissue

• A specialized type of loose connective tissue.
• Stores fat in adipose cells distributed throughout the matrix.

Bone Tissue (Osseus Tissue)

• A hard calcified connective tissue.
• Composes the skeleton.

Muscle Tissue

• Responsible for movement.
• Three types: skeletal, smooth, and cardiac.

Skeletal Muscle

• Responsible for voluntary movements of the body.
• Also called striated muscle due to its striped appearance under the microscope.

Smooth Muscle

• Lacks striations.
• Involuntary.
• Found in the walls of the digestive tract, bladder, arteries, and other internal organs.

Cardiac Muscle

• Found only in the heart.
• Cardiomyocytes (heart muscle cells) are striated.
• Differs from skeletal muscle in other ways.

This quiz covers the basic concepts of epithelial tissue, including its functions, types, and classifications. Learn about simple and stratified epithelia as well as the different cell shapes involved. Test your understanding of how epithelial tissue plays a crucial role in protection and absorption within the body.