Class 9 Science Tissues
Tissue
Tissues are groups of cells that have a similar structure and function, working together to perform specific activities.
The study of tissue is known as “Histology”.
Plant Tissues
Various organs and organ systems present in the body of plants are also made up of tissues. This is the first level of organization, which forms organs and organ systems respectively. There are mainly two types of plant tissues-
(i) Meristematic Tissue
Depending on the region where they are present, meristematic tissues are classified.
These tissues are immature and continuously dividing.
There are three types of these tissues-
- Apical Meristem tissues: These are present in the top part of the stem/shoot and root and its main work is increasing length. It is two types.
- i) SAM (Shoot apical Meristem)
- ii)RAM (Root apical Meristem)
- Lateral Meristem tissues: These are present in the periphery of the stem and root and its main work to increase the thickness of the stem.
- Intercalary Meristem tissue: These tissues are present both at the base of the leaves and before the branch. This tissue present only in grasses and its main work is to increases length of stem.
Overall, We can say that the main function of meristematic tissue is growing plants.
(ii) Permanent Tissue
These tissues are formed by meristem tissue only and are known as the main functional tissues of plants. Their cells do not have the ability to divide.
There are two types of these tissues
- Simple permanent tissue: These tissues are formed by the same type of cells.
- i) Parenchyma: Parenchyma is a versatile plant tissue involved in photosynthesis, storage, and healing, with thin cell walls for flexibility.Its main function is to store water and food items.
- Living tissue
- Intercellular space present
- Thin cell wall and made up of cellulose
- Helps in photosynthesis and storage of food
- This tissue is present in stem, leaves, roots, fruit and flower.
- Modification of Parenchyma
- Chlorenchyma: Chlorenchyma, a type of parenchyma tissue in plants, contains chloroplasts and facilitates photosynthesis, playing a crucial role in converting light energy into chemical energy for the plant.
- Aerenchyma: Aerenchyma is a plant tissue that has big air gaps. These gaps help the plant breathe and live in wet/water or low-oxygen places and help in floating.
- ii) Collenchyma: Collenchyma is a plant tissue that provides flexible support, allowing growth while strengthening stems and leaves without breaking.
- Living tissue
- Intercellular space can be present or absent.
- Cell wall is thickend only from corners due to deposition of cellulose, hemicellulose and pectin.
- Provides mechanical support and flexibility.
- This tissue is present in Hypodermis, petioles of the leaves, stem tendrils
- iii) Sclerenchyma: Sclerenchyma is a rigid plant tissue with thick cell walls, providing structural support and strength to mature plants.
- Dead tissue
- Intercellular space is absent.
- Cell wall is uniformly thick due to presence of lignin.
- Provides strength, support and hardness plant parts.
- Found in stem, roots, veins of leaves l, hard covering of seed and nuts, Husk of the coconut.
- i) Parenchyma: Parenchyma is a versatile plant tissue involved in photosynthesis, storage, and healing, with thin cell walls for flexibility.Its main function is to store water and food items.
- Complex permanent tissue: These tissues are made up of more than one type of cells and are responsible for internal transport in plants.These are of two types-
- (i) Xylem: Xylem is a plant tissue that transports water and nutrients from roots to leaves. These are four types.
- Tracheids: Tracheids are plant cells that conduct water and provide support.
- Vessel: Vessels are plant cells that efficiently conduct water and nutrients, enhancing the efficiency of water transport in plants.
- Xylem fibre: Xylem fibers provide structural support, aiding in water and nutrient transport and strengthening plant tissues against mechanical stress.
- Xylem parenchyma: Xylem parenchyma stores nutrients, provides support, and helps in water conduction within the xylem tissue of plants.
- (ii) Phloem: Phloem is a plant tissue that transports sugars and nutrients from leaves to other parts. These are four types.
- Sieve tubes: Sieve tubes are phloem cells that transport sugars and other nutrients throughout the plant for growth and energy.
- Companion cells: Companion cells support sieve tube function by providing metabolic support and regulating nutrient transport in plants’ phloem.
- Phloem parenchyma: Phloem parenchyma stores nutrients, aids in phloem transport, and provides metabolic support to surrounding cells in plant tissues.
- Phloem fibre: Phloem fibers provide structural support and protection to the phloem tissue in plants, aiding in the transport of nutrients.
- (i) Xylem: Xylem is a plant tissue that transports water and nutrients from roots to leaves. These are four types.
Difference between meristematic tissue and permanent tissue
| Meristematic tissue | Permanent tissue |
|---|---|
| 1. It is devide repeatedly. | 1. It is derived from meristematic tissue and do not divide. |
| 2. It is small and isodiametric. | 2. It is variable in shape and size. |
| 3. Intercellular spaces are generally absent. | 3. Visible intercellular spaces are present l. |
| 4. Vacuoles are absent. | 4. Large vacuoles are present in mature cells. |
| 5. The cell walls are thin. | 5. Cell wall may be thin or thick. |
Difference between Xylem and Phloem
| Xylem | Phloem |
|---|---|
| It transport water and minerals from root to the apical parts of the plant. | It transport food material from the leaves to growing parts of the plant. |
| Xylem consist of tracheids, vessel, xylem fibres and xylem parenchyma | Phloem consists of sieve cells, phloem fibres and phloem parenchyma. |
| Only xylem parenchyma is living. | Sieve tubes, sieve cells, companion cell and phloem parenchyma are living. |
| Tracheids, vessel, xylem fibres are dead tissue. | Phloem fibres are dead tissue. |
| Conduction of water by xylem is unidirectional i.e. from root to apical parts of the plant. | Food material conduction is bidirectional i.e. from leaves to storage organs to growing parts of plants. |
Protective Tissue
These are two types
- (i) Epidermis : In plants, the epidermis is the outermost layer of cells that protects against water loss, infection, and injury, and helps regulate gas exchange.
- Functions of Epidermis
- 1. The epidermis protects plants from injury, pathogens, and water loss.
- 2. The thick cuticle of the epidermis reduces transpiration and helps desert plants retain water.
- 3. Stomata in the epidermis allow gas exchange for respiration and photosynthesis.
- 4. Epidermal cells in roots increase surface area for better absorption.
- (ii) Cork : Cork tissue is a protective, outer layer of cells in plants that prevents water loss and shields against damage and pathogens.
- Function of Cork Tissue
- Cork tissue is a protective layer on plants that stops water from escaping and protects against harm and diseases.
- Cork stops injuries and water loss.
- Cork’s ability to resist water, be lightweight, tough, and compressible makes it valuable in business.
- Cork is used to make various products like bottle stoppers, shuttlecocks, and wooden paddles
Animal Tissue
These differ from plant tissues because they are modified according to their life form, that is, instead of dead plant cells, the body of animals is mostly made up of living tissues that provide mechanical strength. These tissues are of the following types-
1. Epithelial Tissue
Epithelial tissue is a type of tissue that covers the surfaces of organs, lines cavities and tubes within the body, and forms the outer layer of the skin. It serves protective, absorptive, secretory, and sensory functions in various parts of the body.
- Simple Epithelium
- Stratified or Compound Epithelium
- Squamous Epithelium
- Stratified Squamous Epithelium
- Columnar Epithelium
- Cuboidal Epithelium
- Ciliated Epithelium
| Name | Location | Structure | Function |
|---|---|---|---|
| Squamous epithelium | Inner surface of the mouth, oesophagus(food pipe), blood-vessels, alveoli(in lungs) | Thin, small, flat cells form semipermeable membrane | Selective transport of substances. |
| Stratified squamous or Compound Epithelium | Outer layer of skin | Many layer of cells | Prevention of wearing of organs, protection of organs. |
| Columnar epithelium | Inner surface of intestine, alimentary canal | Column-like tall cell Upper free surface beats folds made of these cells at places or absorption | Secretion of digestive juice, absorption of nutrients |
| Cuboidal epithelium | Tubules of kidney (nephron) salivary glands | Cells are cuboidal | Reabsorption of useful materials from urine, secretion of saliva |
| Glandular epithelium | Inner layer of skin, etc. | Cells contain vesicles packed with secretory material | Secretion of sweat, oil (sebum), mucus, etc. |
| Ciliated epithelium | inner surface of respiratory tract | Upper free surface of cells bears minute hair-like processes (Celia) | Push mucus and air forward to keep the air passage free |
2. Muscular Tissue
Muscular tissue is a type of tissue in the body that is specialized for contraction and movement. It is composed of cells called muscle fibers, which can contract and generate force. There are three main types of muscular tissue:
- (i) Skeletal muscle/ Striated muscle/Voluntary muscle: Skeletal muscle tissue is a type of muscle tissue that is attached to bones and is responsible for voluntary movements of the body.
- Structure: Skeletal muscle fibers are long, cylindrical, multinucleated cells with a striated appearance due to the arrangement of actin and myosin filaments.
- Function: Skeletal muscles are primarily responsible for voluntary movements, posture, and support of the skeleton. They are under conscious control.
- Location: Attached to bones by tendons.
- (ii) Cardiac muscle: Cardiac muscle tissue is a specialized type of muscle tissue that is found exclusively in the heart. It is responsible for the rhythmic contractions that pump blood throughout the body
- Structure: Cardiac muscle fibers are branched, interconnected cells with a single central nucleus and striations. They contain intercalated discs, which are specialized junctions that allow for synchronized contractions.
- Function: Cardiac muscle tissue is responsible for the rhythmic contractions of the heart, which pump blood throughout the body. It operates involuntarily.
- Location: Found exclusively in the heart.
- (iii) Smooth muscle/Non-striated muscle/Involuntary muscles: Smooth muscle tissue is a type of muscle tissue that is found in the walls of various hollow organs and structures within the body. It is responsible for involuntary movements and functions essential for bodily processes.
| Name | Structure | Location | Working |
|---|---|---|---|
| Skeletal muscle | Fibres arranged in the form of bundles Dark and light bands present | Limbs ( arms, legs) Tongue Body Face Neck | Contract quickly but can’t remain contracted for long. Get fatigued/tired. |
| Cardiac muscle | Fibres arranged in the form of network. Faint dark and light bands | Walls of the heart | Contract quickly and rhythmically. Do not get fatigued/tired. |
| Smooth muscle | Fibres arranged in the form of sheet. Dark and light bands absent | Stomach Intestine Blood vessel Urinary bladder bronchi of lungs | Contract slowly but can remain contracted for long. |
3.Nervous tissue
Nervous tissue is essential for communication within the body. It consists of neurons, which transmit signals, and glial cells, which support neurons. This tissue allows the body to respond to stimuli, process information, and maintain homeostasis.
- Functions of Muscular Tissue
- Movement: Muscular tissue enables movement of the body and its parts through contraction and relaxation.
- Posture Maintenance: Skeletal muscles help maintain body posture by holding the body in stationary positions.
- Heat Production: Muscle contractions generate heat, which helps maintain body temperature.
- Stabilization: Muscles stabilize joints and maintain alignment during movement.
- Blood Circulation: Cardiac muscles pump blood, while smooth muscles in blood vessels regulate blood flow and pressure.
- Digestive and Respiratory Functions: Smooth muscles facilitate the movement of food through the digestive system and regulate airflow in the respiratory system.
4. Connective Tissue
Connective tissue is a type of tissue that is found throughout the body. It supports, binds together, and protects other tissues and organs.
- Types of Connective Tissue
- Loose Connective Tissue:
- Areolar Tissue: Provides a flexible support and fills spaces between organs.
- Adipose Tissue: Stores fat and provides insulation and cushioning.
- Reticular Tissue: Forms a supportive framework for organs like the liver and spleen.
- Dense Connective Tissue:
- Dense Regular Tissue: Contains tightly packed collagen fibers, providing strong connections, such as in tendons and ligaments.
- Dense Irregular Tissue: Contains collagen fibers arranged in a less ordered manner, providing strength in multiple directions, such as in the dermis of the skin.
- Cartilage:
- Hyaline Cartilage: Provides smooth surfaces for joint movement and forms the framework of the nose, trachea, and ribs.
- Elastic Cartilage: Provides flexibility and maintains the shape of structures like the ear and epiglottis.
- Fibrocartilage: Provides strong support and absorbs shock, found in intervertebral discs and the menisci of the knee.
- Bone:
- Provides structural support, protection for vital organs, and a reservoir for minerals.
- Blood:
- Transports nutrients, gases, hormones, and waste products, and plays a role in immune defense and clotting.
5. Nervous Tissue
Nervous tissue is a specialized tissue found in the brain, spinal cord, and nerves. It is responsible for transmitting and processing information throughout the body.
- Functions of Nervous Tissue
- Sensory Input:
- Nervous tissue receives sensory information from the internal and external environment through receptors in the sensory organs.
- Integration and Processing:
- It processes and interprets sensory input, making decisions about appropriate responses.
- Control of Muscles and Glands:
- Nervous tissue sends signals to muscles to contract and to glands to secrete hormones, thereby controlling bodily functions and actions.
- Homeostasis:
- It helps maintain homeostasis by regulating body processes such as heart rate, breathing, and digestion.
- Mental Activities:
- Nervous tissue is responsible for higher mental functions, including thinking, memory, learning, and emotions.
- Locations
- Central Nervous System (CNS): Includes the brain and spinal cord.
- Peripheral Nervous System (PNS): Consists of nerves that extend from the CNS to the rest of the body.
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