All living organisms are made up of cells. Some organisms are unicellular and some multicellular. A group of cells is called a tissue. Tissue may be defined as a group of cells that may be or may not be similar in structure but are specialized to perform specific functions. The tissue of an animal is Animal tissue while the tissue of plants is known as plant tissue. Cells having similar structures, origins and functions are termed tissues. The study of tissues is called histology. The study of the development and differentiation of tissues is known as histogenesis.
Introduction A multi-cellular animal is composed of different kinds of cells. The cells are different in origin, structure, and function. A group of cells, which are similar in origin and function, is called tissue. The word ’tissue’ (Gr. Tissue-woven) was firstly used by a French anatomist Bichat (1792). He is also considered the father of histology. The microscopic study of tissue is called histology. The term ‘histology’ was used and defined by Mayer (1819). An Italian scientist Marcello Malpighi is considered the founder of histology. He creates a separate branch of histology for the study of tissue.
A cell is the basic unit of the body. Many cells form tissue. Many tissues are combined to form an organ and a number of organs functioning together constitute an organ system and various organ systems constitute a body.
Types of Tissues
On the basis of structure and function, there are four fundamental types of animal tissues. These are epithelial tissue, connective tissue, muscular tissue, and nervous tissue.
1. Epithelial Tissues
Epithelial tissue is the tissue that forms covering of the various body parts (skin) on the outside as well as the various internal organs and body spaces inside. The cells are closely packed almost no intercellular substances or matrix in between the cells. The cells are held together by a cementing substance made up of carbohydrate derivatives. The cells lie on a thin noncellular basement membrane and it is not supplied with blood vessels. Epithelial tissues are protective, secretary, glandular and sensory in functions.
Types of Epithelial Tissues
On the basis of the shape of cells and cell layers, the epithelial tissue can be classified into two types
- Simple epithelium — The epithelial cells are arranged in single layers (one layered cells).
- Stratified epithelium — The epithelial cells are arranged in multiple layers (two or more layers).
Simple Epithelial Tissues
- Simple squamous epithelium
- Simple cuboidal epithelium
- Simple columnar epithelium
- Pseudo-stratified epithelium
Stratified or Compound Epithelial Tissues
- Stratified squamous epithelium
- Stratified cuboidal epithelium
- Stratified columnar epithelium
- Transitional epithelium
Modified Epithelial Tissues
- Ciliated epithelium
- Sensory epithelium
- Germinal epithelium
- Glandular epithelium
2. Connective Tissues
Connective tissues bind the different types of cells or tissues together in an organ. These are developed from mesoderm. Connective tissues consist of different kinds of cells and fibers. This tissue constitutes about 30% of the body and has a large amount of non-living intercellular substances known as matrix
Functions of Connective Tissues
- Bind the differnt cells or tissues together.
- Store lipids or fat globules in the cells are in adipose.
- Form skeleton or support framework of body.
- Provide the hard surface for muscle attachment.
- Transport material form one place of another in body.
- Defend the body against mocroorganisms and toxic substances.
- Replace dead and damaged tissues.
- Insulate the body.
Types of Connective Tissue
Proper Connective Tissue
- Loose Connective
- Dense Connective
Supportive Connective Tissue
Fluid Connective Tissue
Read Also: Meristematic Tissue
3. Muscular Tissue
Muscular Tissue is also mesodermal in origin. It is highly contractile in nature and is an elongated cell called muscles fibres. Each fibre contains fine longitudinal fibrils called the myofibrils. Its cytoplasm is known as sarcoplasm. Each muscle fibre is externally covered by a membrane called sarcolemma. The fibres are highly contractile.
Muscles are supplied with blood vessels that provide nutrition and take away metabolic wastes. Each muscle has its own nerve supply. The muscular tissues are used for movements of arms or limbs for locomotion. There are three kinds of muscles, these are
- Unstriated (unstriped or involuntary muscles)
- Striated (striped or skeletal or voluntary muscles)
- Cardiac Muscles
Function of Muscular Tissue
Muscular tissue performs the following functions:
- It helps in movement and locomotion of our body.
- The main function of muscular is to supports the bones and other structures.
- It is responsible for peristalsis and parturition.
4. Nervous Tissue
Nervous tissues form the nervous system of animals. It controls and coordinates the body’s functions. It is ectodermal in origin. It consists of nerve cells (neurons), processes of nerve cells (nerve fibres), packing cells (neuroglia), and epithelial (ependymal) cells. Axon a fiber of nervous tissue is a bundle of fibers that uses electrical and chemical signals.
Cells of Nervous Tissue are
- Neurosecretory Cells
- Ependymal Cells
Hence, we have discussed animal tissue, types of animal tissue, and all its functions. A good description of each tissue will be described in single posts. You can read out all these posts.
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