Cellular Organelles, Tissues, and Body Systems

Posted on Jan 7, 2025 in Biology

Membranous Organelles

  • Endoplasmic Reticulum

    A network of flattened membranous sacs.

    • Rough ER: Connected to the nuclear envelope, covered with ribosomes, synthesizes proteins.
    • Smooth ER: Lacks ribosomes, synthesizes lipids.

  • Golgi Complex

    Network of membranous sacs with dilated ends. A pile of these sacs forms a dictyosome. It produces lysosomes.

  • Mitochondria

    Rod-shaped, double membrane (inner and outer). Inner membrane has folds called cristae. The space inside is the matrix. They specialize in synthesizing energy through cell respiration.

  • Lysosomes

    Small bags containing digestive enzymes to digest substances.

Non-Membranous Organelles

  • Ribosomes

    Small organelles made of protein and RNA. They consist of a large and a small subunit. Synthesized in nucleoli, located in cytoplasm and on the rough ER. They read RNA and synthesize proteins.

Types of Tissues

  • Epithelial Tissue

    Two types:

    • Coating Tissues: Cover and protect the body surface (epidermis in skin) and internal cavities (blood vessels).
    • Glands: Synthesize substances. Three types:
      • Exocrine Glands: Release substances into cavities or the body surface (e.g., sweat glands).
      • Endocrine Glands: Secrete hormones into the bloodstream (e.g., testes release testosterone).
      • Exocrine and Endocrine Glands: Consist of both parts (e.g., pancreas secretes insulin and pancreatic juice).

  • Connective Tissue

    Made of cells, extracellular substance, and fibers (e.g., collagen). Five types:

    • Conjunctive Tissue: Connects tissues and organs. Cells are called fibroblasts.
    • Fat Tissue: Energy reservoir. Cells are called adipocytes, full of fats.
    • Cartilaginous Tissue: Elastic tissue, structural component of the rib cage, ear, and nose. Cells are called chondrocytes.
    • Bone Tissue: Cells are called osteocytes. High extracellular calcium content.
    • Blood: Liquid tissue, made of cells (red cells, leukocytes, and platelets) in plasma. Transports nutrients and waste.

  • Muscular Tissue

    Formed by muscle fibers or myocytes. Three types:

    • Striated Skeletal Muscle Tissue: Striated appearance with light and dark bands.
    • Cardiac Muscle Tissue: Striated, single central nucleus.
    • Smooth Muscle Tissue: Not striated, single central nucleus. Surrounds vessels and the digestive system, moves food along the gastrointestinal tract.

  • Nervous Tissue

    Composed of neurons (transmit impulses) and glial cells (help neurons in impulse propagation).

Organs and Systems

Organs: Brain, heart, kidney, etc.

  • Systems involved in nutrition: Circulatory, respiratory, digestive, and excretory systems.
  • Systems involved in reproduction: Reproductive system.
  • Systems involved in relationships: Nervous, muscular, skeletal, and endocrine systems.