An Idea On Animal Tissues

Cells are found in all living species, including microorganisms, animals, and plants. Plants and animals are typically multicellular, whereas microorganisms are unicellular. Multicellular organisms arrange their cells into functional units termed tissues. Tissues are made up of identical cell types that perform similar activities. Animal tissues consist of animal cells and play a vital part in forming several organs in the body. These tissues differ in their structure, origin, and functions. The article below will discuss the several types of tissues in animals and their important functions. 

Animal Tissues: Types

Animal tissues are segregated into four types, namely;

• Epithelial tissue
• Neural tissue
• Muscle tissue
• Connective tissue.

Epithelial Tissue

They are closely packed, flat sheets of cells that cover the external or internal surface.  

Location: Epithelial tissues cover organ surfaces, like the skin surface, the reproductive tract, the airways, and the surfaces of soft organs. It also covers the thin inner lining of the digestive tract.  

Types: Epithelial tissue is classified into several categories based on the number of sheets or layers it forms and the morphology of each cell that comprises those layers. The major types of epithelial tissues include:

• Simple epithelial tissues
• Cuboidal epithelial tissues
• Stratified epithelial tissues
• Squamous epithelial tissues
• Columnar epithelial tissues
  • Ciliated columnar epithelial tissues
  • Glandular columnar epithelial tissues.

Characteristics of epithelial cells

• The cells are tightly packed together to form continuous layers. A cementing substance consisting of glycoprotein holds the cells together.
• The epithelial cells can divide and regenerate throughout their lives.
• The epithelial cells’ free surfaces either have delicate hair-like structures called cilia or microvilli, or they can be smooth.
• The epithelium is devoid of blood vessels. The lymph vessels are unable to puncture this tissue due to the lack of intercellular gaps. Therefore, blood circulation is nonexistent in the epithelium.
• Apart from protection, these tissues in animals have specialised functions like absorption, excretion, and secretion. 

Functions: The primary function of epithelial tissue is protection. The cells that make up an epithelial layer are connected by semi-permeable, tight junctions, forming a barrier between the outside environment and the organ it protects. Epithelial tissue also has specialised functions like absorption, secretion, and excretion in addition to its protective function. Organs are protected by epithelial tissue against injury, fluid loss, and harmful microbes. 

Neural Tissues

The nervous system is divided into the central nervous system and the peripheral nervous system. The spinal cord and the brain make up the central nervous system. On the other hand, the peripheral nervous system is composed of branching peripheral nerves. Neural tissues are the animal tissues that act as the fundamental component of the nervous system. 

It is made up of nerve cells and glial cells. The nerve cells are also called neurons, which receive and send impulses. The glial cells also called neuroglia or glia, help the nerve impulse propagate while also delivering nutrition to the neuron. 

Components: The primary components of neural tissues in animals are neurons and glial cells.

• Neurons: Neurons are the fundamental unit of neural tissue, often known as nerve cells. A cyton, an axon, and axon terminals are all present in each neuron. Dendrites are present in the cell body or the cyton. There is a nucleus in the cell body and several Nissl’s granules. Myelinated and unmyelinated neurons exist. Compared to unmyelinated neurons, the presence of a myelin sheath in the axon aids in the fast transmission of nerve impulses. Neurons cannot divide. 

• Neuroglia: Glial cells, also known as neuroglia, are non-nervous cells that exist alongside, over, as well as between neurons in the retina, ganglia, and the CNS. Microglia and macroglia are the two types.

Functions: The primary function of the neural tissue is to transmit nerve impulses to various body parts. Other functions include the control of different glands and muscles, homeostasis, sensory input, and regulation of mental activities. 

Muscular Tissues

Muscle cells aggregate to form a type of tissue called muscle tissue. These tissues combine to form muscles that have the ability for contraction and relaxation. Muscle cells are typically elongated and long structures. They are composed of contractile proteins, namely actin and myosin. 

Types: Muscle types of tissue are segregated into three types. They are 

• Cardiac muscle tissues
• Smooth or visceral muscle tissues
• Skeletal muscle tissues. 

Location: The cardiac muscle tissues are found in the heart. The smooth muscles are typically located in the organs’ inner linings. The skeletal muscle tissues are found attached to bones. 

Functions: The muscle tissues contain contractile proteins, which aid in contraction and relaxation, resulting in locomotion, or the inner organs’ movement. For instance, the skeletal muscle tissues are responsible for gross movement. The cardiac muscle tissues contract and relaxes to pump blood throughout the body. 

Connective Tissues

Animal tissues that are fibrous and are separated by the extracellular matrix, a non-living substance, are called connective tissues. The intercellular matrix can either be rigid or liquid. For example, the bone matrix is rigid while the blood’s matrix (plasma) is liquid. 

Location: Connective tissues are found throughout the body between organs and other tissues. For example, the 3 outer membranes, also called the meninges, surrounding the spinal cord and the brain is composed of connective tissues. 

Types: Connective tissues can be segregated into

• Dense connective tissue
• Loose connective tissue
• Supportive connective tissue
• Fluid connective tissue.

Functions: Connective tissues are animal tissues that support, separate or connect different types of organs and tissues in the body. They primarily offer support and strength to the soft body parts. 

Conclusion

Animal tissues are composed of several animal cells combined with similar structures and activities. They can be broadly segregated into four types. They are epithelial, connective, muscular, and neural tissues. All these issues have their specific functions in the body of animals. Animal tissues combine to form different organs. While a few tissues protect the organs, the others help with movement and locomotion. The above article discussed the different types of tissues with their classifications, functions and locations in the body.