Body Tissues and Membranes Overview

Body Tissues Overview

• Tissues consist of similar cells organized for a specific function and are studied under histology.
• Four primary tissue types: Epithelial, Connective, Muscle, Nervous.

Intercellular Junctions

• Tight Junctions: Close spaces between cells, found in epithelial linings like the bladder.
• Desmosomes: Act as "spot welds" for cell adhesion, common in outer skin and cardiac tissues.
• Gap Junctions: Tubular channels allowing substance transfer between cells, primarily in cardiac muscle.

Epithelial Tissue Characteristics

• Covers organs and body surfaces, lines cavities, and hollow organs.
• Features a free surface, a basement membrane, and lack of blood vessels (avascular).
• Cells are capable of rapid division, tightly packed, and often contain desmosomes.
• Functions include protection, secretion, absorption, and excretion.
• Classified based on cell shape and layers.

Types of Epithelial Tissue

• Simple Squamous: Single layer of flat cells aiding in material exchange; lines air sacs, blood vessels, and lymphatic vessels.
• Simple Cuboidal: Single layer of cube-shaped cells; found in kidney tubules, ovaries, and gland ducts (e.g., thyroid).
• Simple Columnar: Elongated cells; nuclei aligned near the basement membrane. Associated with cilia and goblet cells; lines the uterus, stomach, and intestines.
• Pseudostratified Columnar: Appears stratified but consists of a single layer with nuclei at varying levels. Contains cilia and goblet cells; lines respiratory pathways.
• Stratified Squamous: Multiple layers with flat top cells; can accumulate keratin; found in the skin, oral cavity, vagina, and anal canal.
• Stratified Cuboidal: Contains 2-3 layers of cube-shaped cells; lines ducts of mammary, sweat, and salivary glands.
• Stratified Columnar: Top layer consist of elongated cells with cube-shaped cells below; found in parts of the male urethra and pharynx.
• Transitional Epithelium: Multiple layers with varying cell shapes; lines the urinary bladder, ureters, and part of the urethra.

Glandular Epithelium

• Composed of specialized cells for secretion.
• Types:
  • Endocrine Glands: Ductless, primarily hormone-secreting.
  • Exocrine Glands: Have ducts, can be unicellular (goblet cells) or multicellular (sweat and salivary glands).

Body Tissues Overview

• Tissues consist of similar cells organized for a specific function and are studied under histology.
• Four primary tissue types: Epithelial, Connective, Muscle, Nervous.

Intercellular Junctions

• Tight Junctions: Close spaces between cells, found in epithelial linings like the bladder.
• Desmosomes: Act as "spot welds" for cell adhesion, common in outer skin and cardiac tissues.
• Gap Junctions: Tubular channels allowing substance transfer between cells, primarily in cardiac muscle.

Epithelial Tissue Characteristics

• Covers organs and body surfaces, lines cavities, and hollow organs.
• Features a free surface, a basement membrane, and lack of blood vessels (avascular).
• Cells are capable of rapid division, tightly packed, and often contain desmosomes.
• Functions include protection, secretion, absorption, and excretion.
• Classified based on cell shape and layers.

Types of Epithelial Tissue

• Simple Squamous: Single layer of flat cells aiding in material exchange; lines air sacs, blood vessels, and lymphatic vessels.
• Simple Cuboidal: Single layer of cube-shaped cells; found in kidney tubules, ovaries, and gland ducts (e.g., thyroid).
• Simple Columnar: Elongated cells; nuclei aligned near the basement membrane. Associated with cilia and goblet cells; lines the uterus, stomach, and intestines.
• Pseudostratified Columnar: Appears stratified but consists of a single layer with nuclei at varying levels. Contains cilia and goblet cells; lines respiratory pathways.
• Stratified Squamous: Multiple layers with flat top cells; can accumulate keratin; found in the skin, oral cavity, vagina, and anal canal.
• Stratified Cuboidal: Contains 2-3 layers of cube-shaped cells; lines ducts of mammary, sweat, and salivary glands.
• Stratified Columnar: Top layer consist of elongated cells with cube-shaped cells below; found in parts of the male urethra and pharynx.
• Transitional Epithelium: Multiple layers with varying cell shapes; lines the urinary bladder, ureters, and part of the urethra.

Glandular Epithelium

• Composed of specialized cells for secretion.
• Types:
  • Endocrine Glands: Ductless, primarily hormone-secreting.
  • Exocrine Glands: Have ducts, can be unicellular (goblet cells) or multicellular (sweat and salivary glands).