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Structural organisation deals with the basic structures that organize the organ and organ systems in multicellular animals.
- Tissues contribute to the structural organisation by acting as a main supporting system.
- Plant tissues are not the same as animal tissues.
- Several cells of the same type come together in a group along with intracellular substances to form tissues.
- Different types of tissues are formed for various functions.
Also Read: Difference between Tissues and Organs
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Key Terms: Tissues, Muscles, Organs, Organ System, Morphology, Epithelial Tissues, Epithelium, Intracellular substances, Multicellular animals
Animal Tissues
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In multicellular organisms, several cells of the same type come together in a group along with intracellular substances to form tissues.
- Tissues in animals are different from tissues in plants.
- Different types of animal tissues perform different functions.
- Based on function, animal tissues are classified into three types viz. Epithelial tissues, Connective tissues, Muscle tissues, and Neural tissues.
Animal Tissues
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Epithelial Tissues
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Epithelial tissues, also known as epithelia, are tissues with free surface area.
- They act as a protective covering for some parts of the body.
- Epithelial tissues have very little to no intercellular spaces.
- They are compactly arranged.
- They are held together by small amounts of intercellular materials.
- These tissues either face the outside environment or some type of body fluid.
Epithelial tissues are broadly classified into two types.
- Simple Epithelium and
- Compound Epithelium.
Read More: Megasporangium
Simple Epithelium
Simple Epithelium is composed of a single layer of animal cells.
- It serves as the lining for tubes, body cavities, and ducts.
- Simple Epithelium is divided into subtypes based on the structural modification of animal cells present in the tissue.
They are classified as
- Squamous Epithelium,
- Cuboidal Epithelium, and
- Columnar Epithelium.
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Squamous Epithelium
Squamous Epithelium has flattened cells that are irregular in shape.
- These cells form a single thin layer.
- Squamous Epithelium is usually found in air sacs of the lungs and walls of blood vessels.
- Their function is to form a diffusion boundary.
Squamous Epithelium
Read More: Permanent Tissue
Cuboidal Epithelium
Cuboidal Epithelium has cube-like shaped cells.
- These cells form a single layer.
- Cuboidal Epithelium is usually found in tubular sections of nephrons which are located in kidneys and ducts of glands.
- Their function is to secrete and absorb materials.
Cuboidal Epithelium
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Columnar Epithelium
Columnar Epithelium has slender and tall cells.
- Each of these cells has a nucleus which is commonly located at their base.
- These cells form a single layer.
- Columnar Epithelium is usually found in the linings of intestines and stomachs.
- Their function is to secrete and absorb materials.
Columnar Epithelium
Read More: Catabolism and Anabolism
Compound Epithelium
Compound Epithelium is composed of multi-layers of cells.
- It takes very little part in secretion and absorption.
- Compound Epithelium is commonly located in the inner lining of ducts of pancreatic glands and salivary glands, the moist surface of the buccal cavity, the dry surface of the skin, and the pharynx.
- Their function is to protect the organs against mechanical and chemical stress.
Compound Epithelium
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Connective Tissues
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Connective Tissues link and connect different tissues and organs of the body.
- These tissues are widely found in complex multicellular organisms such as humans.
- All Connective Tissues except blood secret collagen.
- Collagen, also known as elastin, are fibers of structural proteins that are capable of providing flexibility, elasticity, and strength to these tissues.
- Some of the Connective Tissues are adipose, bone, blood, and cartilage.
Connective Tissues are further classified into three types.
- Loose Connective Tissues,
- Dense Connective Tissues, and
- Specialized Connective Tissues.
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Loose Connective Tissues
Loose Connective Tissues are tissues that are made up of loosely arranged cells and fibers in a semi-fluid ground substance.
- These tissues act as a support framework for Epithelium Tissues.
- They can also store fats.
- Examples of Loose Connective Tissues are areolar tissue and adipose tissue.
Loose Connective Tissues
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Dense Connective Tissues
Dense Connective Tissues are made up of compactly packed fibroblasts and fibers.
- They can be regular or irregular in shape depending on their type and function.
- An example of a Dense Connective Tissue is Tendon.
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Specialized Connective Tissues
Specialized Connective Tissues are a complex version of Dense Connective Tissues. Some of the Specialized Connective Tissues are blood, cartilage, and bones.
Types of Specialized Connective tissue
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Muscle Tissues [Click Here for Sample Questions]
Muscle Tissues have long and cylindrical fibers that are arranged in parallel arrays.
- These tissues contract and relax in response to external stimuli.
- This action of contraction and relaxation enables organisms to move and maintain the position of various parts of their bodies.
Muscle Tissues are further classified into three types.
- Skeletal Muscles,
- Smooth Muscles, and
- Cardiac Muscles.
Skeletal Muscles
Skeletal Muscles, also known as Striated Muscles are very closely attached to the bones. These muscles have multiple nuclei. Several bundles of muscle fibers are found in the biceps of humans.
Skeletal Muscles
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Smooth Muscles
Smooth Muscles have a tapering shape at both ends.
- They do not have any striations.
- Cell junctions play the role of holding these muscles together.
- These muscles are involuntary muscles as humans cannot control their actions.
- They are present at the internal walls of blood vessels, oesophagus, intestine, and stomach.
Smooth Muscles
Cardiac Muscles
Cardiac Muscles are only present in the heart.
- They are connected by cell junctions and communication junctions.
- When a single cell is given the command to contract or relax, it alerts all the neighboring cells to contract or relax together as a unit.
Cardiac Muscles
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Neural Tissues
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The primary unit of Neural Tissues is called Neurons.
- Every neuron is protected by a neuroglial cell.
- Electrical impulses are generated in the Neurons which travel along the plasma membrane to carry the signal to the next neuron.
- Neural Tissues play an important role in multicellular organ systems.
Neurons
Organ And Organ Systems
All the types of tissues mentioned above come together to form organs.
- Several organs come together to form organ systems.
- Different organs are made up of different types of cells.
- Organ systems are necessary to perform coordinated functions in multicellular organisms.
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Earthworm
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Earthworms are terrestrial invertebrates.
- It is reddish-brown in colour.
- Earthworms live in the moist upper layers of soil.
- Common earthworms found in India are Pheretima and Lumbricus.
| Body type | Long, cylindrical |
| Number of Segments | 100 - 120 |
| Dorsal surface | Median mid-dorsal line |
| Ventral surface | Genital opening |
Morphology of Earthworm
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Cockroaches
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Cockroaches belong to the class Insecta of Arthropoda phylum.
- They are usually brown or black in colour but sightings of bright yellow, green, and red-colored cockroaches are also reported.
- They are nocturnal and omnivorous insects.
- They live in damp places.
- They are considered pests all over the world.
| Size | 0.6 cm to 7.6 cm |
| Body type | Segmented |
| Head | Flexible and mobile in all directions |
| Wings | 2 pairs |
Morphology of Cockroach
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Frog
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Frogs belong to the class Amphibia of phylum Chordata.
- They are amphibians so they can live on land as well as in water.
- They are cold-blooded animals.
- They can camouflage themselves based on their surroundings.
- In India, Rana tigrina is a commonly found species.
| Skin type | Smooth and slippery |
| Dorsal side | Uneven green-coloured skin |
| Ventral side | Uniform yellow-coloured skin |
| Limbs | 2 fore and 2 hind |
Morphology of Frog
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Things to Remember
- There are different types of animal tissues namely Epithelial tissues, Connective tissues, Muscle tissues, and Neural tissues.
- Epithelial tissues are classified into two types viz. Simple Epithelium and Compound Epithelium.
- Simple Epithelium is classified as Squamous Epithelium, Cuboidal Epithelium, and Columnar Epithelium.
- Connective Tissues are classified into three types viz. Loose Connective Tissues, Dense Connective Tissues, and Specialized Connective Tissues.
- Muscle Tissues are classified into three types viz. Skeletal Muscles, Smooth Muscles, and Cardiac Muscles.
- Neurons are the primary unit in Neural Tissues.
- Cells form tissues, tissues form organs, and organs form organ systems.
Sample Questions
Ques. How to differentiate between a male frog and a female frog? [2 Marks]
Ans. The exterior point of differentiation between a male and a female frog is the presence of an external vocal sac on the male. Internally, male frogs have testes while females have ovaries. Their reproductive systems are quite different from each other.
Ques. Do organ systems, in an animal body, work independently? [2 Marks]
Ans. No, organ systems, in an animal body, cannot work independently. Each organ and organ system is highly dependent on others for its smooth functioning. That is why they work in unison and coordinate whenever necessary.
Ques. Name the different body divisions in a cockroach. [2 Marks]
Ans. A cockroach’s body is divided into three divisions. They are the head, thorax, and abdomen. They comprise eyes, antennae, and mouth. The thorax comprises legs and wings. The abdomen comprises the anus.
Ques. What role does neuroglia play in the nervous system? [2 Marks]
Ans. Neuroglia, also known as glial cells, play a very important role in the nervous system. They protect the nervous system and support and maintain its equilibrium. Neuroglia holds the neurons in place and supplies nutrients and oxygen to them.
Ques. Name the types of muscular tissues present in different locations of the human body. [2 Marks]
Ans. The different muscular tissues present in the human body are:
Smooth muscle is present in Blood vessels, urinary bladder, and stomach, Skeletal Muscle is present in Facial muscles, and Cardiac Muscle is present in the Heart.
Ques. Pick the odd one out. (i) Areolar tissue, squamous epithelium, bones, blood (ii) Ligament, exocrine glands, salivary glands, endocrine glands. [2 Marks]
Ans. Squamous epithelium - All the other tissues are connective tissues while Squamous epithelium is epithelial tissue.
Ligament – All the other tissues are glandular epithelial tissues while Ligament is connective tissue.
Ques. Where is the Ciliated Epithelium located in the animal body? [2 Marks]
Ans. Ciliated Epithelium tissue is located on the inner lining of bronchioles, fallopian tubes, etc. It being an Epithelial Tissue is always found in the inner lining of organs in the body. Its function is to absorb and secrete different kinds of material.
Ques. What does a neuron look like? [2 Marks]
Ans. A neuron consists of a cell body with a nucleus and cytoplasm, from which long thin hair-like parts arise. Each neuron has a single long part called the axon, and many small, short branched parts called a dendrite. An individual nerve cell is called a neuron, it may be up to a metre long.
Ques. What are the functions of areolar tissue? [2 Marks]
Ans. Areolar tissues are connective tissues found in animals. It is found between skin and muscles, around blood vessels and nerves and in the bone marrow. It fills the space inside the organs, supports internal organs and helps in the repair of tissues.
Ques. How does the cork act as a protective tissue? [2 Marks]
Ans. Cork acts as a protective tissue because its cells are dead and compactly arranged without intercellular spaces. They have deposition of suberin on the walls that make them impervious to gases and water.
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