3. Tissues in Action – Important & Difficult Keywords with Definitions

Important Keywords and Definitions

Keyword	Definition
Cell	The basic structural and functional unit of life.
Tissue	A group of similar cells that work together to perform a specific function.
Organ	A structure made up of more than one type of tissue working together.
Organ System	A group of organs that work together to perform a major body function.
Organism	A complete living being made up of organ systems.
Division of Labour	The distribution of different functions among different cells, tissues, organs, or organ systems.
Multicellular Organism	An organism made up of many cells.
Unicellular Organism	An organism made up of only one cell.
Plant Tissue	A group of plant cells that perform a specific function like growth, support, protection, or transport.
Animal Tissue	A group of animal cells that perform functions like protection, movement, support, or coordination.

Plant Tissues

Keyword	Definition
Meristematic Tissue	Plant tissue made up of actively dividing cells responsible for growth.
Meristematic Cells	Cells that divide continuously and help the plant grow.
Apical Meristem	Meristematic tissue present at the tips of roots and shoots; it helps plants grow in length.
Root Apical Meristem	Meristematic tissue present at root tips that helps roots grow longer.
Shoot Apical Meristem	Meristematic tissue present at shoot tips that helps shoots grow longer.
Lateral Meristem	Meristematic tissue present along the sides of stems; it helps increase the girth or thickness of plants.
Intercalary Meristem	Meristematic tissue present at the base of internodes or just above nodes; it helps plants regrow after cutting or grazing.
Node	The point on a stem from where leaves or branches arise.
Internode	The part of the stem between two nodes.
Annual Growth Rings	Ring-like structures seen in the cut trunk of a tree, formed due to yearly growth. They help estimate the age of a tree.
Differentiation	The process by which meristematic cells become specialised to perform specific functions.
Permanent Tissue	Plant tissue formed after differentiation; its cells usually lose the ability to divide.
Simple Permanent Tissue	Permanent tissue made up of only one type of cell.
Complex Permanent Tissue	Permanent tissue made up of more than one type of cell working together.

Protective and Supporting Plant Tissues

Keyword	Definition
Epidermis	The outermost protective layer of the plant body.
Cuticle	A waxy layer present on the epidermis that reduces water loss and protects the plant.
Cutin	A waxy substance that forms the cuticle.
Root Hair	Hair-like projections from root epidermal cells that increase the surface area for absorption of water and minerals.
Stomata	Tiny pores present in the epidermis of leaves and young stems for gaseous exchange and transpiration.
Transpiration	The loss of water vapour from the aerial parts of a plant, mainly through stomata.
Transpiration Pull	The pulling force created by transpiration that helps water move upward through xylem.
Parenchyma	A simple permanent tissue made of living, thin-walled cells; it stores food and may help in photosynthesis.
Aerenchyma	Special parenchyma with air spaces that helps aquatic plants float.
Collenchyma	A simple permanent tissue made of living cells with unevenly thickened corners; it provides support and flexibility.
Pectin	A substance deposited at the corners of collenchyma cells, giving them flexibility.
Sclerenchyma	A simple permanent tissue made of thick-walled, mostly dead cells; it provides strength and hardness.
Lignin	A hard substance deposited in sclerenchyma cell walls, making them strong and rigid.

Conducting Plant Tissues

Keyword	Definition
Conducting Tissue	Plant tissue that transports water, minerals, and food within the plant.
Vascular Tissue	Conducting tissue of plants, mainly xylem and phloem.
Xylem	A complex permanent tissue that transports water and minerals from roots to other parts of the plant.
Tracheids	Long, thick-walled cells of xylem that help in water transport.
Vessels	Tube-like xylem cells that help transport water efficiently.
Xylem Parenchyma	The living component of xylem that helps in storage.
Xylem Fibres	Thick-walled xylem cells that provide strength.
Phloem	A complex permanent tissue that transports food from leaves to other parts of the plant.
Sieve Tubes	Long tube-like cells of phloem that transport food.
Companion Cells	Specialised cells that help sieve tubes in loading and unloading sugars.
Phloem Parenchyma	Phloem cells that store food materials and other substances.
Phloem Fibres	Thick-walled phloem cells that provide support.
Dermal Tissue System	The outer protective tissue system of plants, mainly formed by the epidermis.
Ground Tissue System	The tissue system forming the main body of the plant; includes parenchyma, collenchyma, and sclerenchyma.
Vascular Tissue System	The tissue system made up of xylem and phloem for transport.

Animal Tissues

Keyword	Definition
Epithelial Tissue	Animal tissue that forms the outer covering of the body and lines internal organs.
Connective Tissue	Animal tissue that connects, supports, binds, or protects different parts of the body.
Muscular Tissue	Animal tissue that helps in movement by contraction and relaxation.
Nervous Tissue	Animal tissue that receives, processes, and transmits messages in the body.
Matrix	The non-living material present between cells in connective tissue.

Epithelial Tissue

Keyword	Definition
Exchange Epithelium	Thin epithelial tissue that allows rapid diffusion of gases and liquids.
Protective Epithelium	Epithelial tissue with many layers that protects against injury, friction, and microbes.
Secretory Epithelium	Epithelial tissue specialised for producing and releasing substances like mucus, enzymes, hormones, sweat, or saliva.
Sensory Epithelium	Epithelial tissue with receptor cells that help in smell, taste, sound, and balance.
Absorptive Epithelium	Epithelial tissue specialised for absorbing nutrients and water, especially in the intestine.

Connective Tissue

Keyword	Definition
Blood	A fluid connective tissue that transports gases, nutrients, hormones, and wastes.
Plasma	The liquid part of blood that carries dissolved substances.
Red Blood Cells / RBCs	Blood cells that contain haemoglobin and transport oxygen.
Haemoglobin	An iron-rich protein in RBCs that gives blood its red colour and helps carry oxygen.
White Blood Cells / WBCs	Blood cells that help fight infections.
Platelets	Blood components that help in clotting at the site of injury.
Bone	A hard connective tissue that supports the body and protects internal organs.
Cartilage	A flexible connective tissue that cushions joints and provides flexibility.
Tendon	A connective tissue that connects muscle to bone.
Ligament	A connective tissue that connects bone to bone and stabilises joints.

Muscular Tissue

Keyword	Definition
Voluntary Movement	Movement that is under conscious control, such as walking or writing.
Involuntary Movement	Movement that happens automatically without conscious control, such as heartbeat or movement of food in the intestine.
Skeletal Muscle	A voluntary muscle attached to bones; it helps in body movement.
Muscle Fibre	A long muscle cell that helps in contraction and movement.
Striated Muscle	Muscle tissue showing light and dark bands.
Smooth Muscle	An involuntary muscle found in internal organs like the stomach and intestine.
Cardiac Muscle	Involuntary muscle found only in the heart; it works rhythmically throughout life.

Nervous Tissue

Keyword	Definition
Neuron	A nerve cell that receives and transmits messages.
Cell Body	The part of a neuron that contains the nucleus and controls cell activities.
Dendrites	Branch-like parts of a neuron that receive signals from other neurons.
Axon	A long fibre of a neuron that carries messages away from the cell body.
Axon Terminals	End branches of an axon that transmit messages to other cells.
Brain	The control centre of the body that coordinates activities, memory, and responses.
Nerve Impulse	A message transmitted through a neuron.

Musculoskeletal System and Joints

Keyword	Definition
Musculoskeletal System	The system made up of bones, muscles, joints, cartilage, tendons, and ligaments.
Skeleton	The framework of bones that supports and protects the body.
Skeletal System	The body system made up of bones that provides support, shape, and protection.
Joint	A place where two or more bones meet.
Ball and Socket Joint	A joint that allows movement in many directions, such as the shoulder joint.
Hinge Joint	A joint that allows movement in one direction, like the elbow and knee.
Pivot Joint	A joint that allows rotation, such as the joint between the skull and backbone.
Fixed Joint	A joint that does not allow movement, such as joints between skull bones.
Shoulder Girdle	The structure formed by the shoulder joint and collarbone that connects the arm to the skeleton.
Kneecap	A small bone that protects the knee joint.
Skull	The bony structure that protects the brain, eyes, and ears.
Vertebral Column	The backbone or spine made of small bones called vertebrae.
Vertebrae	Small bones that form the vertebral column.
Cartilage Disc	A cushion-like structure between vertebrae that allows flexibility and prevents injury.
Rib Cage	A protective cage formed by 12 pairs of ribs.
Sternum	The breastbone to which ribs are attached in the front.

Advanced Keywords

Keyword	Definition
Totipotency	The ability of a single plant cell to divide and develop into a complete plant.
Totipotent Cell	A cell that has the ability to develop into a complete organism under suitable conditions.
Dedifferentiation	The process in which specialised cells regain the ability to divide.
Redifferentiation	The process in which dividing cells again become specialised to form tissues and organs.
Plant Tissue Culture	A technique of growing plant cells or tissues in a nutrient medium under controlled conditions.
Nutrient Medium	A solution or gel containing nutrients and growth substances needed for cells to grow.
Crown Gall Disease	A plant disease in which tumour-like swellings develop due to uncontrolled cell division.
Agrobacterium tumefaciens	A bacterium that causes crown gall disease and is also used in genetic engineering of plants.
Genetic Engineering	A technique used to introduce useful genes into organisms to improve their characteristics.