Animal Tissues and Their Functions

Tissue Types and Functions

• Tissues are groups of cells performing specific functions together.
• Three primary germ layers in embryonic development:
  • Endoderm: Forms lining of digestive and respiratory systems.
  • Mesoderm: Develops into muscles, bones, and blood vessels.
  • Ectoderm: Forms skin and parts of the nervous system.

Main Types of Animal Tissues

• Epithelial Tissues:

  • Covers body surfaces and lines cavities.
  • Types include Simple (squamous, cuboidal, columnar), Pseudostratified, and Stratified (squamous, cuboidal, columnar).
  • Transitional epithelium allows stretching.

• Connective Tissues:

  • Provides support, binds organs, and protects.
  • Includes connective tissue proper (loose, dense) and specialized types (cartilage, bone, blood).

• Muscle Tissues:

  • Composed of fibers specialized for contraction.
  • Types include Skeletal (voluntary movement), Cardiac (heart contraction), and Smooth (involuntary movements in organs).

• Nervous Tissues:

  • Generates and transmits electrical impulses.
  • Composed of neurons and glial cells that support and protect neurons.

Epithelial Tissue Classification

• Covering and Lining Epithelium:
  • Simple and stratified types for protection, absorption, and secretion.
• Glandular Epithelium:
  • Endocrine Glands: Ductless, release hormones directly into the bloodstream.
  • Exocrine Glands: Secrete substances through ducts to specific sites (e.g., sweat, digestive glands).

Connective Tissue Characteristics

• Connective Tissue Proper:

  • Loose Connective Tissue (e.g., areolar, adipose) provides flexibility and support.
  • Dense Connective Tissue: Contains more collagen, offers strength (e.g., tendons and ligaments).

• Specialized Connective Tissues:

  • Cartilage: Supports structures with types such as hyaline, elastic, and fibrocartilage.
  • Bone: Provides structure and protection for organs.
  • Blood: Composed of plasma and blood cells (erythrocytes, leukocytes, thrombocytes).

Plant Tissues

• Meristematic Tissues: Regions of actively dividing cells, including three types:
  • Apical Meristem: Located at tips of roots and stems, responsible for primary growth.
  • Lateral Meristem: Increases thickness of stems and roots.
  • Intercalary Meristem: Found at bases of leaves or internodes, aids in regrowth.

Types of Plant Tissues

• Ground Tissue: Makes up most of the plant body, involved in photosynthesis, storage, and support.
• Dermal Tissue: The outer protective layer of the plant, consisting of the epidermis in younger parts and periderm in woody plants.
• Vascular Tissue: Contains xylem (water transport) and phloem (nutrient transport), essential for nutrient distribution.

Cell Types in Plant Ground Tissue

• Parenchyma: Living cells that perform functions like photosynthesis and storage (types include palisade and spongy).
• Collenchyma: Living cells with unevenly thickened walls for flexible support.
• Sclerenchyma: Dead cells providing structural support with thickened lignified walls.

Anatomical Differences: Dicot vs. Monocot Roots

• Root System: Dicot (taproot), Monocot (fibrous).
• Vascular Bundle Arrangement: Dicot (diarch/triach/tetrach), Monocot (poly-arch).
• Cambium Presence: Present in dicots, absent in monocots.

Modified Roots

• Adventitious Roots: Develop from stems or leaves for support (e.g., in corn).
• Pneumatophores: Specialized roots in mangrove trees for aeration in submerged conditions.

Important Functions of Parenchyma

• Photosynthesis due to high chlorophyll content.
• Air and water storage mechanisms.
• Supports overall plant development and healing processes.