Tissue Level of Organization - NURS 207

Tissue Level of Organization

• Tissues: Epithelial and connective tissues are covered in this lecture.
• Reading Material: Tortora, 16th edition, Chapter 4
• Date: September 19, 2024
• Professor: Dr. P. Lee
• Course: NURS 207 (N01)

Objectives

• Objective 1: Name the four basic tissue types that constitute the human body.
• Objective 2: Describe the characteristics of each of the four tissue types.
• Objective 3: Detail the classification and features of epithelial, connective, muscular, and nervous tissues.
• Objective 4: Summarize the key differences between epithelial and connective tissues.

Tissues (Colony of Aggregated Cells)

• Diversity of Cells: Leads to a diversity of tissues.
• Four Basic Tissue Types: Epithelial, connective, muscular, and nervous tissues. These visuals illustrate these tissues.
• Structural Variations: Reflect physiological function.

Four Basic Types of Tissues

• 1) Epithelial Tissue:
  • Sheets of cells forming surface linings for the body, hollow organs, body cavities, and ducts.
  • Creates the barrier between internal and external environments.
  • May also function as glands for secretion.
• 2) Connective Tissue:
  • Composed of cells and extracellular matrix.
  • Extracellular matrix is a mixture of protein fibers and ground substance.
  • Ground substance binds cells together within the connective tissue.

Four Basic Types of Tissues: Muscle Tissue

• Characteristics:
  • Can contract, generating tension or force.
  • Generates heat during contraction.
  • Excitable cells (exhibit electrical excitability).
  • Three types: skeletal, cardiac, and smooth muscle.

Four Basic Types of Tissues: Nervous Tissue

• Characteristics:
  • Responds to stimuli by generating and conducting electrical impulses (action potentials).
  • Action potentials are transmitted to target tissues.
  • Elicits a response in the target tissue.
  • Response is proportionate to the initial stimulation.
  • Can be excitatory or inhibitory.
  • Coordinates bodily activities.

Four Basic Types of Tissues: Nervous Tissue System

• Subdivisions: Central Nervous System (CNS) and Peripheral Nervous System (PNS). The PNS has three subunits.
• CNS Structure: Brain and spinal cord
• PNS Structure: Three subsections - sympathetic, parasympathetic, and enteric.

Epithelial Tissue Detailed

• Continuous Sheets: Form protective barriers for body systems.
• Layers: Can be single or multiple layers.
• Tight Junctions: Between neighboring cells limit solute and fluid diffusion around epithelial cells.
• Shapes & Forms: Epithelial cells have various shapes for diverse functions.
• Nerve Supply: Epithelial tissue has its own nerve supply.
• Avascular: No capillary blood supply, requiring nutrient supply and waste removal through surrounding connective tissues via diffusion.

Classification of Epithelial Tissue

• 2 General Types: Covering and lining epithelium; and glandular epithelium.

• a) Covering and Lining Epithelium:

  • Single Layer (Simple): Capable of transporting substances (solvents and solutes) via diffusion and osmosis; also involved in absorption from the external environment to body compartments and secretion from body compartments to external environments, such as intestinal lining.
  • Multiple Layers (Stratified): Primarily protects underlying tissues from wear and tear, like the skin.
  • Pseudostratified: Appears layered but is a single layer, often with cilia and goblet cells for secretion and mucus removal, e.g., upper airway.

• b) Glandular Epithelium: Has secreting cells within a lining structure that function as secretion glands.

• Examples: Intestine, upper airway.

Classification of Epithelial Tissue

• Arrangement (3 Subtypes):

  • Simple: Single layer of cells
  • Pseudostratified: Appears layered but is a single layer.
  • Stratified: Multiple layers of cells

• Shape (4 Subtypes):

  • Squamous: Thin and flat, allows substance passage.
  • Cuboidal: Wide and cube-like shape, often for secretion or absorption.
  • Columnar: Tall and column-shaped, can have microvilli or cilia, and involved in secretion or absorption.
  • Transitional: Stratified epithelium with changing shapes, like in the bladder.

Connective Tissue Detailed

• Abundant Tissue: Most common type of tissue in the body.
• Components: Cells, and extracellular matrix, which include protein fibers and ground substance.
• Cell Types: Fibroblasts, macrophages, mast cells, plasma cells, adipocytes, eosinophils, neutrophils, osteocytes, chondrocytes, and leukocytes, among others.
• Fibers: Collagen, elastic, and reticular fibers contribute to tissue strength and support.
• Ground Substance: Varies in consistency (fluid, semi-fluid, gelatinous, calcified). Composed of polysaccharides and proteins (e.g. glycosaminoglycans or GAGs).
• Functions: Protection, support, connection/binding, transport, and immunity

Classification of Connective Tissue

• Two Main Types: Embryonic and mature connective tissue.
• Embryonic: Includes mesenchyme and mucous connective tissues. Found primarily in developing embryos.
• Mature: Consists of loose, dense, cartilage, bone, and liquid connective tissues.

Various Types of Cells in Connective Tissue

• Fibroblasts: Synthesize and maintain connective tissue's extracellular matrix.
• Macrophages: Phagocytic cells that engulf and destroy foreign substances.
• Plasma Cells: Produce antibodies, crucial components of the immune response.
• Mast Cells: Release histamine and other mediators involved in the inflammatory response.
• Adipocytes: Fat cells that store energy.
• Leukocytes: White blood cells, crucial components of the immune system.
• Osteocytes: Involved in bone formation.
• Chondrocytes: Involved in cartilage formation and maintenance.

Various Types of Fibers in Extracellular Matrix

• Collagen Fibers: Strong, provide tensile strength.
• Elastic Fibers: Flexible, return to original shape after stretching.
• Reticular Fibers: Thin, supportive meshwork.

Ground Substance in Extracellular Matrix

• Extracellular material between cells and fibers.
• Properties: Can be fluid, semi-fluid, gelatinous, or calcified.
• Composition: Mixture of polysaccharides (e.g. glycosaminoglycans) and proteins.
• Functions: Provides a medium for exchange between blood and cells.

Various Functions of Connective Tissue

• Protection: Against pathogens with phagocytes like macrophages.
• Support: Structural support, for example, osteocytes in bone.
• Connection and Binding: Hold organs in place, such as by linking tissues (e.g., tendons, ligaments).
• Support: Holding organs in place (e.g., tendons, ligaments).
• Transport: Carrying nutrients and gases (e.g., blood plasma).

Common Features of Connective Tissue

• Composed of cells and extracellular matrix.
• Extracellular matrix (ECM) surrounds cells and has fibers and ground substance.
• ECM can be soft (adipose) or hard (bone).
• ECM are generally highly vascular, except in cartilage and tendons.
• Contain nerves (except in cartilage)

Sample Questions and Answers (from provided slides)

• Question 1: Which type of epithelial tissue forms the skin? Answer: Stratified epithelium
• Question 2: Which type of epithelial tissue lines the airways and intestine, secreting mucus? Answer: Ciliated glandular epithelium
• Question 3: Where are transitional epithelial cells found? Answer: Lining of the urinary bladder
• Question 4: What components make up the connective tissue extracellular matrix? Answer: Protein fibers and ground substance
• Question 5: What is the extracellular matrix of blood? Answer: Plasma
• Question 6: Which is a good example of dense connective tissue? Answer: Bone