A tissue is a group of cells connected to each other that collectively perform similar functions in an organism. All contents of the body including structures and various organs are made of tissues.
The animal body comprises four basic types of tissues, all of which vary in their origin and function. They are:
Made up of tightly packed cells layer together, epithelial tissues line the body surface. Their functions include protection, absorption, and secretion. Epithelial tissues can be found in the lining of the mouth and nose, digestive system lining, and the skin.
These are of three types, smooth muscle tissue- found in inner linings of organs, skeletal muscle tissue- found attached to the bone and helps in body movement and cardiac muscle tissue- found in the heart. These tissues help in changing the size of a cell.
Made up of neurons (nerve cells in the brain), these tissues form the entire nervous system, including the spinal cord and the brain.
Made of various cells that are involved in lending support to the body, connective tissues are namely the fat, bone, blood and cartilage in an animal body.
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Epithelial Tissues
These tissues form the lining of body surfaces and also account for glands. The cells along these tissues are tightly connected to each other. The epithelium does not contain blood vessels and hence depends on the other connective tissues to derive its nutrients and other essentials.
It is found along the edges of the organs and has two prominent surfaces, namely, the apical surface which is on the exterior and lies open to the body cavity, and the basal surface which lies adjacent to the underlying tissue.
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Epithelial cells can be either squamous, cuboidal, or columnar in shape. The number of cell layers along with the combination of cell shapes decides the classifying features of epithelial tissue.
Types of Epithelial Tissues and Their Function
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Epithelial Tissues are always located on the inner or outer surfaces of organs, and their functions largely depend on the exact position of their locations. These are of the following types:
Squamous Epithelium
Closely packed with one another, these are thin and flat cells that mostly like the esophagus, blood vessels, alveoli and the inner cavities of the mouth. The squamous epithelium tissue lends protection against mechanical injuries, while also blocking any sort of germs from entering.
The squamous epithelium may also be arranged in multiple layers, in which case it is known as the stratified squamous epithelium tissue. These tissues are usually found in the lining of the esophagus and the skin.
Cuboidal Epithelium Tissue
These are cuboidal in shape, hence rightfully deriving their name. Found in kidney tubules, salivary glands, and sweat glands, the functions of the cuboidal epithelium tissue are secretion, protection and absorption.
When the cuboidal epithelium is arranged in multiple layers, it is known as the stratified cuboidal epithelium tissue, and found on the inner side of the salivary glands and pancreatic ducts.
Columnar Epithelium Tissue
Mostly with column-like or pillar-like cells, these can be found in the intestine and lining of the stomach. Important functions of the columnar epithelium tissue include secretion and absorption.
Ciliated Epithelium Tissue
The columnar epithelium tissues often have cilia; this is when they come to be known as ciliated epithelium tissues. These can be found in kidney tubules, the respiratory tract and lining of the trachea. Their function is to help in the movement of material in a given direction.
Glandular Epithelium Tissue
These are majorly modified columnar epithelial tissues whose main function is secretion. They can be found in the sweat glands and tear glands.
Muscle Tissues
Muscle tissues are specialised tissues found in animals, responsible for applying force to various parts of the body by using the method of contraction. Thin and elongated cells called muscle fibers make up the muscle tissues.
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The structure of a muscle tissue contains three distinct elements- the cytoplasm in the muscle fibers, called the sarcoplasm, a membrane network known as the sarcoplasmic reticulum, and the surrounding membrane of the muscle fibers known as the sarcolemma.
Important properties of muscle tissues are as follows-
The ability of a muscle to stretch itself
The ability of the muscle cells to forcefully shorten themselves
The ability of a muscle tissue to respond to a stimulus given by any hormone or a motor neuron
The ability of a muscle to recoil to it’s usual length after being stretched
Types of Muscle Tissues and Their Functions
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Mostly responsible for initiating movement of an organism, muscle tissues have a range of other functions based on their types. These are:
Skeletal Muscle Tissues
Voluntary muscle and striated in nature, skeletal muscle tissues have neatly arranged bundles and have tendons anchoring them. These have an impact on the skeletal movements of an organism that include posture and locomotion.
Smooth Muscle Tissues
These are involuntary and non-striated in nature and have tapered ends. They are mostly located in the blood vessel walls like arteries and veins, urinary tract, trachea and digestive system. Smooth muscle tissues help in peristalsis to move food up and down the alimentary canal.
Cardiac Muscle Tissues
These majorly consist of making up the heart. Involuntary and striated, these are branched out at irregular angles to help with coordinated contractions occurring inside the heart.
Nervous Tissues
Nervous tissues are the cells that form the central and peripheral nervous system. While in the central nervous system, the nervous tissues form the spinal cord and the brain, in the peripheral nervous system, the nervous tissues make up the cranial and spinal nerves, also including the motor and sensory neurons.
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The most important function of the nerve tissues is to transmit and carry nerve impulses in various parts of the body. Impulses are often sent by axons and received by dendrites.
Nerve cells can be of three types- sensory neurons, motor neurons and interneurons.
Connective Tissues
These are tissues that support, connect or separate various other kinds of tissues and organs inside the body. They are made up of cells, fibers like collagen and extracellular matrix. Collective tissues can be found abundantly located inside the body in a freely arranged form or in a matrix.
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Types and Functions of Connective Tissues
The various types of connective tissues include areolar, adipose, bone, cartilage and fat. All cells are involved in the secretion of collagen except for blood.
Areolar Connective Tissues
These are found under the skin, surrounding nerves and blood vessels. Their function is to repair tissues and provide support.
Adipose Tissues
These can be found in the organs and skin. Composed of fat globules, their function is to insulate the body with the fat presence.
Bones
These form the skeletal structure of the body and have a characteristic of being rich in calcium and collagen fibers. They protect the body and are the location of blood cell production.
Cartilage
These can be found in the ear tips, vertebral column, bronchi and are made of chondrocytes that are composed of flexible intercellular materials.
Blood
The functions of blood include putting up a defence system, transportation and most importantly homeostasis. Blood is composed of blood cells that include platelets, RBC and WBC along with plasma.
Relevance of knowing Types of Animal Tissues in Biology
Our body is made up of four kinds of tissues. Each of these tissues vary in their functions. They are epithelial tissues, muscle tissues, nervous tissues and connective tissues. Knowing about these will help all students in understanding basic facts about our bodies. It will especially be a help to those students who intend to take up Biology as a career later on as getting the fundamentals right at an early stage will always come to one’s rescue when he/ she faces difficulty in tackling a question.
Conclusion
The article presented a complete insight about animal tissues types and functions. Learning about them will help in future.