Histology Concept – What is it, plant and animal histology

We explain what histology is and the topics that this discipline studies. Also, plant and animal histology and importance.

Histology - human tissue
Histology is also called “microscopic anatomy” or “micro anatomy.”

What is Histology?

Histology is a discipline that is part of biology and examines the tissues of organisms through a microscope to understand their structure and its functions. It is also called “microscopic anatomy” or “micro anatomy.” The word histology comes from the Greek, histo which means “tissue” and logos, which means “knowledge”.

Marcello Malpighi, Italian anatomist and biologist, is considered the founder of histology for having been the first to examine living cells through a microscope at the beginning of the 17th century. Malpighi was the one who discovered the existence of small units within tissues, called cells.

What does histology study?

Histology - biology - tissues
Histopathology helps to learn more about the possible causes of a disease.

Histology studies the microscopic structure of tissues, that is to say, complex groupings of cells organized to fulfill a certain function. The human being, for example, originates from the fusion of two cells: an egg and a sperm. Both cells, in turn, then divide repeatedly to form new cells that make up the different tissues, organs, and systems of the human body. Histological examinations provide insight into how the various components of the body are organized, interrelated, and function.

Histological examinations provide important contributions to:

  • Histopathology. It is the part of histology that examines tissue samples taken from a diseased organism to learn more about the possible causes of the disease and provide a more accurate diagnosis.
  • Forensic investigations and autopsies. The analysis of biological tissues, using special techniques, can clarify the causes of unexpected deaths and provide scientific evidence available to justice.
  • The arqueology. By examining the cells and biological tissues found in recovered remains from ancient societies, information about their history can be obtained.
  • The education. The basic techniques of histology are taught in laboratory workshops to introduce students to the concept of microstructures of different organisms.

General biology recognizes the existence of two groups of organisms: vascular plants (from the plantae kingdom) and animals (from the animal kingdom). Based on this distinction, histology is subdivided into plant histology and animal histology to categorize the different tissues.

Plant histology

Histology - plant tissue
Adult tissues are made up of cells larger than embryonic ones.

Plant histology is the specific study of plant tissues that are classified into two types:

  • Meristematic or embryonic tissues. They are made up of small cells that have a great capacity to multiply.
  • Adult tissues. They are those permanent or of duration in the plant and are composed of cells larger than the embryonic ones. These, in turn, can be:
    • Parenchymal tissues. They are made up of cells that are responsible for nutrition and the accumulation of reserves.
    • Protective or surface fabrics. They are made up of cells that cover the plant and isolate it from the external environment.
    • Supportive tissues or collenchyma. They are composed of cells with thick walls and an elongated shape that give the plant rigidity.
    • Conductive or vascular tissues. They are made up of cylindrical cells that join together and form tubes or ducts, through which nutrients circulate.
    • Secretory and excretory tissues. They are made up of cells that secrete plant substances, such as pine resin.

Animal histology

Animal tissue - histology
Connective tissues contain a viscous material that separates cells from each other.

Animal histology studies the organic tissues of animals that, unlike the plant kingdom, have cells that form very diverse organisms in terms of their shape and function. Animal tissues are classified into four types:

  • Epithelial tissues. They are made up of several layers of cells joined together that form a cell membrane that covers all surfaces of the body (such as the epidermis, digestive and respiratory tracts) and internal cavities (such as arteries, veins and capillaries).
  • Connective or conjunctive tissues. They contain cells of varying shape together with a viscous material that separates them, called “intercellular substance”, which allows other tissues to join to provide support and integration, for example, adipose, cartilaginous, bone and blood tissue .
  • Muscle tissues. They are made up of elongated cells called “muscle fibers”, which contain myofibrils capable of contracting and giving elasticity to the muscles. Depending on the shape and type of contraction, muscles are classified as skeletal, cardiac, and smooth.
  • Nervous tissues. They are made up of cells called “neurons” that establish a complex connection system and have the ability to regenerate extremely slowly. They function as receptors for stimuli (sensory neurons) to which they respond with nerve impulses (motor neurons) that successively propagate to other neurons (association neurons).

Importance of histology

The study of histology allows us to know the structure and function of the organs through microscopic examination of the cells that make them up. The results of histological studies are key to medicine and biology, both to know the properties of the organism under normal conditions and to examine the presence of pathologies, their evolution and their possible diagnosis.