What are Tissues?
A particular function is carried out by a cluster of cells at a definite place in the body.This cluster of cells, called tissue.
Tissue is arranged and designed so as to give the highest possible efficiency of function.Blood, Phloem and muscle are all examples of tissues. A group of cells that are similar in structure and/or work together to achieve a particular function forms a tissue.
~ Meristematic Tissue~
The growth of plants occurs only in certain specific regions. This is because the dividing tissue, also known as meristematic tissue,is located only at these points. Depending on the region where they are present meristematic tissues are classified into three:-
2. Intercalary Meristem
3. Lateral Meristem
Apical Meristem is present at the growing tips of the stem and the root and increases the length of the stem and the root.
The girth of the stem or the root increases due to lateral meristem.
It is the meristem at the base of the leaves or inter nodes on twigs.
They take up a specific role and loose the ability to divide. As a result, they form a permanent tissue.
*The process of taking up a permanent shape, size and a function is called differentiation.
SIMPLE PERMANENT TISSUE:~
A few layers from the basic packing tissue.This tissue is parenchyma a type of permanent tissue.
In some situations it contains chlorophyll and performs photosynthesis and then it is called chlorenchyma.
In aquatic plants large air cavities are present in parenchyma to give buoyancy to the plants to help them float such a parenchyma is called aerenchyma.
The flexibility in plants is due to collenchyma.
Complex Permanent Tissue
Complex tissues are made of more than one type of cells. For e.g. Xylem and Phloem. They are both conducting tissue and constitute a vascular bundle (vascular or conductive tissue is a distinctive feature of the complex plants one that has made possible their survival in the terrestrial environment).
Xylem consists of tracheids and vessels, xylem parenchyma and xylem fibres. The cells have thick walls, and many of them are dead cells. Tracheids and vessels are tabular structures. This allows them to transport water and minerals vertically. The parenchyma stores food and helps in sideway conduction of water.
Phloem is made of four types of elements: sieve tubes, companion cells, phloem fibres and Phloem parenchyma. Sieve tubes are tabular cells perforated walls (perforated means they have pores). Phloem is unlike Xylem in that materials can move in both directions in it. Phloem transports food from leaves to other parts of plants.
When we breathe we can actually feel the movement of our chest. How do these body parts move?For this we have specialized cell called muscle cell. The concentration and relaxation of these cells result in movement.During breathing we inhale oxygen. Where does this oxygen go?It is absorbed in the lungs and then transported to the whole body cells through blood.Blood and muscles are both e.g. of tissues found in our body.
The covering or protective tissues in the animal body are epithelial tissues. Epithelium covers most organs and cavities within the body.
There is a simple flat kind of tissue known as simple squamous epithelium. they are thin and flat and form a delicate lining.The oesophagus and the lining of the mouth is also covered by the simple squamous epithelium.
Skin epithelial cells are arranged in a pattern of layers, the epithelial is called Stratified squamous epithelium. Where absorbing and secretion occurs.
Blood is a type of connective tissue.The cells of connective tissue are loosely spaced and embedded in an inter cellular matrix.Matrix may be rigid, fluid, jelly like.
Muscular tissue consist of elongated cells also called muscle fibres. This tissue is responsible for movement in our body.
The brain spinal chord and nervous are all composed of nervous tissue. The cells of this tissues are called nervous tissue or neurons.