Human Tissue Anatomy: A Comprehensive Review

Posted on Mar 27, 2025 in Biology

Understanding Human Body Tissues

Tissue: A group of cells performing the same function, all originating from the same group of stem cells.

Types of Tissues:

  • Epithelial: Covers external and internal surfaces of the body.
  • Connective: Supports and connects organs and systems.
  • Muscle: Collaborates in the movement of our body and internal organs.
  • Nervous: Transmits nerve impulses and coordinates the functioning of all other body systems.

Epithelial Tissue

  • Epithelia cover the skin and the internal lining of many organs (digestive system, bladder, respiratory tract, urethra, glands).
  • Made up of various layers of cells closely joined together.
  • Two types:
    1. Epithelium Tissue
      • Forms the skin and the internal lining of body cavities: digestive, respiratory, excretory tracts.
      • Protects organs against dehydration, infections, wounds, etc. (it is the first defense barrier against pathogenic agents: viruses). Skin has 2 layers: The outer one is thicker and is called the epidermis (made up of dead cells made up of keratin, making it impermeable), the dermis is the inner layer (it replaces the cells of the epidermis that continuously lose).
    2. Glandular Tissue

      In charge of the production and release of different substances (saliva, tears, digestive juices). Cells of this epithelium organize into glands.

Connective Tissue

  • Made up of cells embedded in an extracellular component (matrix) that joins the cells together. The matrix can be solid (bone, cartilage), semi-liquid (conjunctive, adipose), or liquid (blood).
  • Five types:
    1. Conjunctive Tissue:
      • Stuffing among organs and scaffolding to which they attach to keep body shape and organs in place.
      • The matrix is rich in protein fibers such as collagen.
      • Makes up the tendons and ligaments.
    2. Adipose Tissue: Cells called adipocytes accumulate droplets of fat (lipids) in their vesicles and vacuoles as an energy reserve, thermal insulator of the body, and protection against hits.
    3. Cartilaginous Tissue:
      • Firm and elastic tissue made up of cells (chondrocytes) embedded in a semi-solid, jelly-like matrix.
      • Makes up the joints and strengthens the larynx, trachea, and nose. Young bones are cartilaginous.
    4. Bone Tissue
      • Made up of cells (osteocytes) enclosed in a rigid/solid matrix made up of proteins (collagen) and Calcium Phosphate (mineral). Osteocytes secrete the solid bone. Supports, gives shape to the organism, allows movement, and creates blood cells in the bone marrow. Bone marrow: Our bones produce blood cells of our organisms in the innermost part of the bone, called bone marrow.

Muscle Tissue

  • Made up of myocytes (or “muscle fibers”); elongated contractile cells capable of relaxing and contracting.
  • Responsible for the body’s movements.
  • Types:
    1. Striated (voluntary): Found in the skeletal muscles and allows the skeleton to move. Voluntary contraction. Actin and myosin are the 2 proteins that make up all muscle tissue.
    2. Smooth (involuntary): Allows the movements of internal organs that contract and relax involuntarily to perform their function (except the heart).
    3. Cardiac (involuntary): Exclusive to the heart; contracts involuntarily but is a variety of striated muscle. Myocytes show striae and “intercalated discs”: fibrous unions among them.

Nerve Tissue

This tissue is only present in animals and is formed by neurons, which transmit electric signals called “nerve impulses”. Neurons can’t reproduce themselves.

The nervous tissue has 2 types of cells: neurons (transmit) and glial cells (feeling and sustaining).

Tissues that Make Up Bone:

  • Bone tissue: gives structural support (osteons).
  • Adipose tissue: blood production (red bone marrow).
  • Blood tissue: feeding the osteocytes (arteries and veins inside bone).
  • Connective tissue: protecting the bone (periosteum surrounding).
  • Nervous tissue: gives sensitivity to the bone.

Tissues that Make Up the Stomach:

  • Mucosa: epithelial (absorbs nutrients).
  • Submucosa: connective (joining epithelial absorbing and the muscle).
  • Muscularis: muscle (involuntary contractions that help to get the food to cells).
  • Serosa: connective (keeps the stomach in place).