Types of Body Tissues

Types of Body Tissues

• Epithelial tissue: Covers body surfaces, lines cavities, and forms glands.
  • Functions include protection, secretion, absorption, excretion, filtration, diffusion, and sensory reception.
  • Characterized by tightly packed cells with minimal extracellular matrix.
  • Classified by shape (squamous, cuboidal, columnar) and layering (simple, stratified).
• Connective tissue: Supports, connects, and separates different tissues and organs.
  • Contains cells scattered within an abundant extracellular matrix, composed of ground substance and fibers (collagen, elastic, reticular).
  • Types include: loose connective tissue (e.g., adipose), dense connective tissue (e.g., tendons, ligaments), cartilage, bone, and blood.
• Muscle tissue: Responsible for movement.
  • Three types: skeletal (voluntary), smooth (involuntary), and cardiac (involuntary).
  • Skeletal muscle is striated and attached to bones; smooth muscle is non-striated and found in internal organs; cardiac muscle is striated and found only in the heart.
• Nervous tissue: Receives, processes, and transmits information.
  • Composed of neurons and neuroglia (supporting cells).
  • Neurons transmit electrical signals; neuroglia support and protect neurons.

Characteristics of Epithelial Tissue

• Polarity: Apical (free) and basal (attached) surfaces.
• Specialized contacts: Tight junctions, desmosomes, and gap junctions.
• Supported by connective tissue: Basement membrane provides support and filters.
• Avascular: Lacks blood vessels, depending on diffusion from underlying connective tissue for nutrients and waste removal.
• Regeneration: High capacity for renewal and repair.

Classification of Epithelial Tissue

• Based on shape of cells: Squamous (flat), cuboidal (cube-shaped), columnar (column-shaped).
• Based on layers of cells: Simple (single layer), stratified (multiple layers).

Glands

• Exocrine glands: Secrete products into ducts that empty onto surfaces (e.g., skin, digestive tract).
  • Examples include sweat glands, salivary glands, and mammary glands.
• Endocrine glands: Secrete products (hormones) directly into the bloodstream.
  • Examples include thyroid gland, pituitary gland, and adrenal glands.

Connective Tissue Subtypes

• Loose connective tissue: Binds and supports body parts, underlies most epithelial tissues.
• Dense connective tissue: Forms tendons and ligaments, providing strong structural support for movement.
• Cartilage: A firm, flexible tissue supporting structures like ears, nose, and joints.
• Bone: Hard connective tissue providing skeletal support.
• Blood: Fluid connective tissue carrying oxygen, nutrients, and waste products throughout the body.

Muscle Tissue Types

• Skeletal muscle: Voluntary muscle tissue responsible for movement.
  • Structure involves striated appearance and multinucleated cells.
• Smooth muscle: Involuntary muscle tissue found within internal organs.
  • Smooth appearance (non-striated) and single-nucleus cells.
• Cardiac muscle: Involuntary muscle tissue only found in the heart.
  • Striated appearance and interconnected cells (intercalated discs) enabling coordinated contraction.

Nervous Tissue Components

• Neurons: Specialized nerve cells transmitting information.
  • Structure includes cell body, dendrites, and axon.
• Neuroglia (glial cells): Support and protect neurons.
  • Types include astrocytes, oligodendrocytes, and Schwann cells.

Functions of Body Tissues

• Protection: Epithelial tissue protects underlying tissues from pathogens and physical injury.
• Support: Connective tissue provides support and structure to the body.
• Movement: Muscle tissue enables movement of body parts.
• Communication: Nervous tissue facilitates communication and coordination throughout the body.
• Secretion and absorption: Epithelial tissues are involved in secretion and absorption.

Tissue Repair

• Regeneration: Damaged tissue replaced with similar tissue.
• Fibrosis: Damaged tissue replaced with scar tissue (connective tissue).

Tissue Inflammation

• Tissue response to injury or infection.
  • Signs include redness, swelling, heat, pain.
• Important in initiating tissue repair.

Relationship Between Tissues and Body Systems

• Tissues are the fundamental building blocks that form organs.
• Organs are made up of two or more tissue types working together to perform a specific function.
• Different organ systems include multiple organs working together for more complex functions. For example, the digestive system relies on epithelial tissues for absorption, while smooth muscle tissues and nervous tissue contribute to motility and regulation.