Tissues diversity in shape

What is Tissue ?

The word tissue comes from an old French verb which means “to weave”. Tissue is a level of organisation in multicellular organisms which consists of a group of structurally and functionally identical cells and their intercellular material. They are arranged in close proximity and perform one or more distinct functions.

Tissues do not exist in unicellular organisms. Even in simple multicellular species like sponges, tissues are either absent or poorly differentiated. But multicellular animals and plants that are more developed have specialised tissues that can regulate an organism’s reaction to its environment.

Body

There are four various kinds of tissues in animals: connective tissue, muscle tissue, nervous tissue and epithelial tissue. 

Connective Tissue

Connective tissue is one of the most extensive and widely distributed primary tissues which varies in amount from one particular organ to another. It maintains the form of the body by providing structure and internal support.

The three main components of the connective tissue are; cells, fibres and ground substance (an amorphous matrix). The ground substance is a clear, colourless, viscous fluid which is composed of cell adhesion proteins. It fills the void between the cells and fibres and acts as glue for the cells to bind to the matrix. 

The ground substance and the fibres together make up the extracellular matrix. There are three types of fibres which aid connective tissue to provide support, that is, collagen fibres, elastic fibres and reticular fibres.

There are four main categories of connective tissue, that is:

Connective tissue proper

Cartilage

Bone

Blood

Epithelial Tissue

Epithelium is a major type of body tissue which forms the membrane of all interior and exterior surfaces of the body, lines the body cavities and hollow organs. Epithelial tissue has a variation of benefits relying on where it’s situated and the processes involved. They can be of various shapes and can be organised in a single or multiple layers depending on where they are in our body and what type of functions they carry out.

Epithelial tissue has several significant functions that are vital to life. Their function and objective change on the basis of their location. Some of the functions are: 

Protection: Epithelial tissue safeguards several characteristics of your body, such as, skin is made up of epithelial tissue which preserves the tissues present deep inside our body, such as blood vessels, muscle and internal organs. 

Secretion: Epithelial tissue in our glands can secrete enzymes, hormones and fluids.

Absorption: The epithelial lining of inner organs, such as liver and lungs, enable absorption of specific substances. For example, epithelial lining of intestines absorbs nutrients from the food we eat.

Excretion:  The epithelial tissue in kidneys excrete waste materials. Similarly, the epithelial tissue in our sweat glands excrete sweat.

Filtration: The epithelium of the respiratory tract filters out dirt and clears the air that we breathe. Similarly, epithelial tissue in kidneys filters your blood.

Sensory reception: The body obtains external sensory impulses through sensory nerve endings embedded in epithelial tissue.

The major types of epithelial tissue are:

Simple squamous epithelium: This type of epithelial tissue lines blood vessels and body cavities and administers the passage of substances into the primary tissue.

Simple cuboidal epithelium: This type of epithelial tissue is found in secreting tissue and kidney tubules.

Simple columnar epithelium: This type of epithelial tissue is specialised for absorption and has apical cilia or microvilli which lines our stomach and intestines.

Stratified squamous epithelium: This type of epithelial tissue has defensive functions which includes protection against microorganisms from invading underlying tissue and protection against water loss. 

Stratified cuboidal epithelium: The excretory ducts of salivary and sweat glands have stratified cuboidal epithelial tissue, which is not very common.

Stratified columnar epithelium: This type of epithelial tissue is not common and is seen in the mucous membrane, lining of eyelids, where it’s both protective and mucus-secreting.

Pseudostratified columnar epithelium: Pseudostratified columnar epithelial tissue has a lot of cilia and lines the upper respiratory tract.

Conclusion 

Animal cells range from a few microscopic micrometres to a few millimetres. Their shape varies from flat, to oval or rod-shaped. Multicellular animals are four major types: epithelial, connective, muscle, and nervous. We know, tissues are associations of identical cells and groups of identical cells carrying out relevant functions. Tissues combine to form organs and organs are organised into organ systems to perform functions. These combine to permit organisms to exist.

Animal tissues are made up of epithelial, connective, muscle and nerve tissue.

Epithelium is associated with secretion of enzymes and protective substances such as mucus and they deliver a supportive advantage.

Muscle tissue made up of cardiac and smooth muscle are involuntary in nature whereas skeletal muscle is voluntary.  

Connective tissues are composed of cartilage, bone and blood provides strength and support, decreases friction and acts as shock absorbers.

Nervous tissue is accountable for receiving stimuli from the environment, processing it and transmitting impulses to muscles or glands so that one can react to the stimuli.