Four Basic Tissue Types and Epithelial Tissue

Study Notes

Four Basic Tissue Types

Nervous tissue: Transmits signals throughout the body.
Connective tissue: Supports, protects, and binds other tissues.
Epithelial tissue: Covers surfaces and lines cavities.
Muscle tissue: Enables movement.

Epithelial Tissue

Functions: Protection, absorption, filtration, excretion, secretion, sensory reception.
Characteristics:
- Polarity: Apical (free) surface exposed to the environment, basal surface attached to underlying connective tissue.
- Specialized contacts: Tight junctions and desmosomes for cell-to-cell adhesion.
- Supported by connective tissue: Attached to a basement membrane for structure and support.
- Avascular but innervated: No blood vessels, but supplied with nerves.
- Regeneration: Can repair themselves quickly.

Glands

Endocrine glands: Secrete hormones directly into the bloodstream. Example: Pancreas releasing insulin.
Exocrine glands: Secrete products through ducts onto body surfaces or cavities. Example: Sweat glands.

Connective Tissue

Characteristics:
- Common embryonic origin: All connective tissues develop from mesenchyme.
- Varying degrees of vascularity: Some, like cartilage, are avascular, while others, like bone, are highly vascularized.
- Cells suspended in extracellular matrix (ECM): Provides structure and support.
Structural elements:
- Ground substance: Unstructured gel-like material containing interstitial fluid, cell adhesion proteins, proteoglycans, and water.
- Fibers: Provide support.
  - Collagen: Strongest, providing tensile strength.
  - Elastic: Allows stretching and recoiling.
  - Reticular: Fine, branched fibers forming networks for support within organs.
- Cells: Responsible for production of fibers and ground substance.
  - Blast cells (immature): Actively secrete ECM components.
    - Fibroblasts (connective tissue proper)
    - Chondroblasts (cartilage)
    - Osteoblasts (bone)
    - Hematopoietic stem cells (bone marrow)
  - Cyte cells (mature): Help maintain the ECM.
  - Fat cells: Store nutrients.
  - White blood cells: Immune response (neutrophils, eosinophils, lymphocytes)
  - Mast cells: Initiate inflammatory response.
  - Macrophages: Phagocytic cells that engulf debris and microorganisms.

Connective Tissue Types

Connective tissue proper:
- Loose connective tissue:
  - Areolar: Supports and binds other tissues, holds fluids, defends against infection, stores fat. Found beneath epithelial tissue, digestive and respiratory systems.
  - Adipose: Stores nutrients (white fat), supports local nutrient needs, generates heat (brown fat). Found under skin, around organs, between muscles.
  - Reticular: Supports blood cells, forms stroma of organs. Found in lymph nodes, spleen, bone marrow.
- Dense connective tissue:
  - Dense regular: Provides tensile strength in one direction, forms tendons, ligaments, aponeuroses.
  - Dense irregular: Provides tensile strength in multiple directions, found in dermis, fibrous capsules of organs.
Cartilage:
- Hyaline: Strong, flexible, found in joints, nose, trachea.
- Elastic: More flexible, found in ears, epiglottis.
- Fibrocartilage: Very strong, found in intervertebral discs, menisci of knee.
Blood: Fluid connective tissue, transports oxygen, nutrients, waste products.
Bone: Hard, rigid connective tissue, provides support, protection, mineral storage.

Description

Explore the four basic types of tissues in the human body, with a focus on epithelial tissue. This quiz covers functions, characteristics, and various types of glands related to epithelial tissue, enhancing your understanding of histology.