Biology Tissue Types and Functions

Tissue Types

• Nervous tissue transmits signals throughout the body.
• Connective tissue supports, protects, and binds other tissues.
• Epithelial tissue covers surfaces, forms glands.
• Muscle tissue responsible for movement.

Epithelial Tissue Functions and Characteristics

• Functions: protection, absorption, filtration, excretion, secretion, sensory reception.
• Characteristics:
  • Polarity: Distinct apical (free) and basal surfaces with different structures and functions.
  • Specialized Contacts: Cells tightly connected through junctions, minimizing gaps.
  • Supported by Connective Tissue: Underlying connective tissue provides support.
  • Avascular: Lack blood vessels, nourishment from underlying tissue.
  • Innervated: Contains nerve endings for sensation.
  • Regeneration: Cells constantly renew and replace.

Exocrine vs. Endocrine Glands

• Exocrine glands: Secrete products through ducts to outer surface, such as sweat glands.
• Endocrine glands: Secrete hormones directly into bloodstream, such as thyroid gland.

Connective Tissue Characteristics

• Embryonic Origin: All connective tissues arise from mesenchyme.
• Vascularity: Varying degrees of blood vessel presence, cartilage is avascular while bone is highly vascularized.
• Extracellular Matrix (ECM): Cells are embedded in ECM, composed of ground substance and fibers.
  • Ground substance: Unstructured gel-like material that fills the space between cells.
    • Components: interstitial fluid, cell adhesion proteins, proteoglycans, and water.
  • Fibers: Provide support:
    • Collagen: Strongest, resists tension.
    • Elastic: Stretchy and recoil.
    • Reticular: Short, branched, form supporting networks.

Connective Tissue Cells

• Blast cells: Immature form of cell that actively secretes ECM:
  • Fibroblasts: In connective tissue proper.
  • Chondroblasts: In cartilage.
  • Osteoblasts: In bone.
  • Hematopoietic: Stem cells in bone marrow.
• Cyte cells: Mature, less active form, maintain matrix.
• Fat cells: Store nutrients.
• White blood cells: (neutrophils, eosinophils, lymphocytes) for tissue response to injury.
• Mast cells: Initiate inflammatory response.
• Macrophages: Phagocytic cells, “eat” dead cells and microorganisms.

Connective Tissue Types

• Connective Tissue Proper:

  • Loose Connective Tissues:
    • Areolar: Supports and binds tissues, holds fluids, defense against infection, nutrient storage.
    • Adipose: Stores nutrients (White Adipose Tissue), supports local nutrient needs, generates heat (Brown Adipose Tissue).
    • Reticular: Supports free blood cells, forms internal framework for organs.
  • Dense Connective Tissues:
    • Dense Regular: Provides tensile strength, connects structures.
    • Dense Irregular: Withstands tension from multiple directions, provides structural strength (dermis of skin, fibrous capsules of organs).

• Cartilage: Strong, flexible, shock-absorbing tissue, avascular.

  • Hyaline cartilage: Most common, found in nose, trachea, ribs, embryonic skeleton.
  • Elastic cartilage: Flexible, found in ear and epiglottis.
  • Fibrocartilage: Strongest, found in intervertebral discs and menisci.

• Blood: Fluid connective tissue that transports gases and nutrients.

• Bone: Hard, calcified connective tissue, provides support and protection.

  • Compact bone: Dense, outer layer of bone.
  • Spongy bone: Porous, inner layer of bone.
  • Bone marrow: Produces blood cells.

This quiz covers the different types of tissues in biology, including nervous, connective, epithelial, and muscle tissues. It delves into epithelial tissue's functions, characteristics, and the differences between exocrine and endocrine glands. Test your knowledge and understanding of these essential biological concepts.