Every living body is made of cells. But cells do not work alone. Similar cells join together and do one job as a team. Such a group is called a tissue. Exams ask many direct questions here. They ask which tissue carries water, which tissue joins muscle to bone, and which muscle never gets tired. This post explains plant and animal tissues in simple words. It ends with 15 previous year questions.
Key Points (Quick Revision)
- A tissue is a group of similar cells doing one job. Its study is called histology.
- Plants have meristematic (dividing) and permanent tissues.
- Xylem carries water. Phloem carries food.
- Animals have four tissues: epithelial, connective, muscular and nervous.
- Tendon joins muscle to bone. Ligament joins bone to bone.
1. What is a tissue?
A tissue is a group of cells. These cells are similar in shape. They also work together for one function.
Think of a factory. Each team does one job. One team packs. Another team paints. Tissues work in the same way inside a body.
The study of tissues is called histology. The Italian scientist Marcello Malpighi is often called the father of histology.
Plants and animals have different tissues. Why? Their lives are different. Plants stay in one place. They need strong support, so many plant tissues are dead and hard. Animals move around. They need more energy, so most animal tissues are living.
Plants also grow all their lives, but only in some areas. Animals grow more evenly. This is another reason their tissues differ.
2. Meristematic tissue in plants
Meristematic tissue is the growing tissue of a plant. Its cells keep dividing. They make new cells all the time.
These cells have thin walls. They have dense cytoplasm and a large nucleus. They have almost no vacuoles.
There are three kinds, based on their place in the plant.
| Type | Where it is found | What it does |
|---|---|---|
| Apical meristem | Tips of the root and the shoot | Increases the length of the plant |
| Lateral meristem (cambium) | Along the sides of the stem and root | Increases the girth (thickness) |
| Intercalary meristem | At the base of leaves or at the nodes | Helps parts grow in between, as in grasses |
The cambium adds new layers every year in many trees. These layers form annual rings in the trunk. By counting the rings, we can estimate the age of a tree.
3. Permanent tissue in plants
Cells made by the meristem later stop dividing. They take a fixed shape and a fixed job. They form permanent tissue.
Permanent tissue is of two main kinds. They are simple and complex.
Simple permanent tissues have only one type of cell.
- Parenchyma - living cells with thin walls. They store food. They fill most soft parts of a plant. When they have chlorophyll, they are called chlorenchyma. They make food. In water plants, they have large air spaces. Then they are called aerenchyma. This helps the plant float.
- Collenchyma - living cells with walls thick at the corners. They give flexibility. So leaves and young stems can bend without breaking. They are found in leaf stalks.
- Sclerenchyma - dead cells with very thick walls. The walls have a hard substance called lignin. They make parts hard and stiff. The husk of a coconut is made of them. Jute fibres also come from them.
Protective tissue covers the plant. The outer layer is the epidermis. On leaves, it often has a waxy layer called the cuticle. This reduces water loss.
The epidermis of a leaf has tiny pores called stomata. Each pore is guarded by two guard cells. Gases pass in and out through stomata. Water is also lost from here. This loss is called transpiration.
In older trees, the outer layer becomes cork. Cork cells are dead. Their walls have a waxy substance called suberin. It makes cork waterproof. Commercial cork comes from the cork oak tree.
4. Complex tissues - xylem and phloem
Complex tissues have more than one type of cell. All the cells work together. The two complex tissues are xylem and phloem. Together, they are called vascular tissue.
| Point | Xylem | Phloem |
|---|---|---|
| Carries | Water and minerals | Food made in the leaves |
| Direction | Mostly upward, from root to leaves | Both up and down |
| Parts | Tracheids, vessels, xylem parenchyma, xylem fibres | Sieve tubes, companion cells, phloem parenchyma, phloem fibres |
| Living or dead | Mostly dead; only xylem parenchyma is living | Mostly living; only phloem fibres are dead |
The movement of food through phloem is called translocation. The wood of a tree is mostly xylem.
5. Epithelial tissue in animals
Animal tissues are of four types. The first is epithelial tissue. It is the covering tissue.
It covers the body from outside. It also lines organs and cavities inside. Its cells are packed closely. There is little space between them.
| Type | Where found |
|---|---|
| Squamous (thin and flat) | Lining of blood vessels and lung air sacs; in layers in the skin |
| Cuboidal (cube-shaped) | Kidney tubules and ducts of glands |
| Columnar (tall, pillar-like) | Inner lining of the intestine |
| Ciliated (with hair-like cilia) | Respiratory tract; the cilia push mucus forward |
| Glandular | Glands that make sweat, saliva and other secretions |
Where cells are arranged in many layers, the tissue is called stratified. The skin has stratified squamous epithelium. It protects against wear and tear.
6. Connective tissue
Connective tissue joins and supports other tissues. Its cells are loosely spaced. They sit in a material called the matrix. The matrix can be liquid, jelly-like or hard.
- Blood - a fluid connective tissue. Its matrix is plasma. It has red cells, white cells and platelets. It carries gases, food and hormones.
- Bone - a hard connective tissue. Its matrix has calcium and phosphorus. It forms the skeleton.
- Cartilage - softer and flexible. It is found in the nose, ear, trachea and at the ends of bones.
- Tendon - joins muscle to bone. It is very strong but not very flexible.
- Ligament - joins bone to bone. It is elastic and strong.
- Areolar tissue - found between the skin and muscles. It fills space and helps repair.
- Adipose tissue - stores fat. It lies below the skin. It keeps the body warm.
7. Muscular and nervous tissue
Muscular tissue helps the body move. Its cells are long. They are called muscle fibres. They can contract and relax.
| Type | Features | Where found |
|---|---|---|
| Striated (skeletal) | Voluntary; long, unbranched, many nuclei; light and dark bands | Arms and legs, attached to bones |
| Smooth (unstriated) | Involuntary; spindle-shaped, one nucleus | Food pipe, intestine, blood vessels, iris of the eye |
| Cardiac | Involuntary; branched, one nucleus; works non-stop | Only in the heart |
Cardiac muscle contracts and relaxes all through life. It does not get tired like arm muscles.
Nervous tissue carries messages. Its cells are called neurons. They are found in the brain, the spinal cord and nerves.
A neuron has three parts. The cell body has the nucleus. Dendrites are short branches that receive messages. The axon is a long fibre that sends messages away.
A neuron can be very long. It is often called the longest cell in the human body.
8. Previous year questions
- The study of tissues is called what? – Histology
- Which tissue increases the length of a plant? – Apical meristem
- Which tissue increases the girth of a stem? – Lateral meristem (cambium)
- Which tissue carries water and minerals in plants? – Xylem
- Which tissue carries food in plants? – Phloem
- Which tissue helps aquatic plants float? – Aerenchyma
- The husk of a coconut is made of which tissue? – Sclerenchyma
- Cork cells have which substance in their walls? – Suberin
- The age of a tree can be found by counting what? – Annual rings
- Which tissue connects muscle to bone? – Tendon
- Which tissue connects bone to bone? – Ligament
- Which is a fluid connective tissue? – Blood
- Which muscle works throughout life without getting tired? – Cardiac muscle
- Which is the longest cell in the human body? – Neuron (nerve cell)
- Which tissue stores fat in the body? – Adipose tissue
9. How to revise this topic
First, draw the two family trees. One is for plant tissues. The other is for animal tissues. Keep them on one page.
Next, learn the xylem vs phloem table. Many questions come from it.
Then learn the pairs that exams love: tendon and ligament, aerenchyma and floating, sclerenchyma and coconut husk, cork and suberin.
Finally, revise the three muscle types with one example each.
10. Frequently Asked Questions
What is a tissue?
A tissue is a group of similar cells that work together to do one job. For example, xylem carries water in plants, and muscle tissue helps animals move.
What is the difference between xylem and phloem?
Xylem carries water and minerals, mostly upward from the root to the leaves. Phloem carries food made in the leaves to other parts, in both directions. Xylem is mostly dead, while phloem is mostly living.
What is the difference between a tendon and a ligament?
A tendon joins a muscle to a bone. A ligament joins one bone to another bone. Both are connective tissues.
Why is blood called a connective tissue?
Blood connects all parts of the body. It carries oxygen, food, hormones and waste. It has cells floating in a liquid matrix called plasma, so it is called a fluid connective tissue.
Which muscle is involuntary but striated?
Cardiac muscle, found only in the heart. It has bands like skeletal muscle, but it works on its own without our control.
For more Biology topics in simple language, see our Cell Structure and Functions, Muscular System and Photosynthesis and Plant Nutrition posts, or browse the General Science section. Preparing for a specific exam? Start with the SSC CGL guide or join the 100 Hour GS Course.