Tissues
- Tissues are groups of cells that have a similar structure and act together to perform a specific function
- A group of cells having a common origin and similar in structure and function is known as tissue.
Difference between Plants and Animals Tissue
Plants
1. Stationary or Fixed
2. Growth in a limited region
3. Needless energy to survive
4. Most of the tissues are dead
Animals
1. They can move.
Tissues are two types:-
(1) Plant Tissues
(2) Animal Tissues
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(1) Plant tissues
Plant tissues are primarily classified into two groups: -
(a) Meristematic Tissue
(b) Permanent Tissue
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1. (a) Meristematic Tissue -
- These are simple living tissues capable of the division and formation of new cells.
- Ex-roots, growing branches, etc.
- Meristematic cells are capable of dividing continuously to produce new cells.
- The meristematic tissues are present only at the growing regions such as shoot tip, root tip, and cambium.
- The cells of meristematic tissue are very active, have dense cytoplasm, thin cellulose walls, and prominent nuclei.
Meristematic Tissues are three types: -
(i) Apical meristem
(ii) Intercalary meristem
(iii) Lateral meristem
(i) Apical meristem
- It is present at growing tips, of stems and roots
- This tissue leads to the elongation of stems and roots
- This evolved in the primary growth of plants
(ii) Intercalary meristem
- It is present at the internodes,
- It is part of Apical meristem which is left behind during growth
- It helps in the longitudinal growth of the plant
(iii) Lateral meristem
- It occurs along the side of the longitudinal axis of the plant
- It gives rise to vascular tissues
- It causes growth in girth of stem and Roots
- This is responsible for secondary growth.
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1. (b) Permanent Tissue -
It is composed of those cells which have lost their capability to divide they have a definite shape, size, and thickness. It may be dead or living.
Permanent Tissue is two types :
(i) Simple permanent tissue
(ii) Complex permanent tissue
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(i) Simple Permanent Tissue -
These are made up of the same types of cells which are similar in structure and also in function
Simple Permanent Tissue includes two types of tissues
(A) Protective Tissues
(B) Supportive Tissues
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(A) Protective Tissues -
- Epidermis
- Cork or Phloem
Epidermis
It is the outermost single cell layer of plant organs such as leaves, flowers, roots, etc. It is covered by Cutile (waterproof layer)
Stomata -
The epidermis has small pores on its surface. These pores are called Stomata. These are enclosed by two kidney-shaped cells called guard cells.
Functions of Epidermis
- It protects the plant from desiccation and infection
- Cuticle cuts the rate of transpiration and evaporation of water
- Stomata allow gaseous exchange during photosynthesis
- Stomata also help in transpiration
Cork or Phloem -
- It is made up of dead cells with thick walls and does not have intercellular spaces.
- Cell walls in Cork deposit a waxy substance called suberin.
- The cell wall is impermeable. It does not have any protoplasm
Functions of Cork and Phellem
- It prevents plants from infection or mechanical injury
- It is a shock absorber, insulator for plants
- Provide toughness to plants
- Cork used in making of sports goods like - Cricket ball, table tennis, wooden paddles, etc
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(B) Supporting Tissues
- Parenchyma
- Collenchyma
- Sclerenchyma
Parenchyma -
It is a thin-walled cell, composed of living cells, oval and spherical in structure. It has large central vacuoles, found in leaves, the pith of stems, and roots.
Functions -
- Storage foods in large vacuoles
- Provide turgidity to cells
- Photosynthesis
- Wound repair and new growth
- Buoyancy control in aquatic plants
Collenchyma -
It forms filler tissue in soft parts of plants present in the cortex, pith primary stems, and roots It is found below the epidermis. Cells of this tissue are living, wait thickened at the corners.
Functions -
- Provide flexibility to plant parts.
- Also, provide mechanical support
- Filling the vacant place
Sclerenchyma -
It is strengthening tissue composed of extremely thick-walled cells made up of lignin. Its cells are dead
Present in stems, around vascular bundles, in the veins of leaves, and hard covering seeds and nuts.
Functions -
- Provide strength to plant parts
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(ii) Complex Permanent Tissue
- It consists of more than one type of cell which works together as a unit.
- It is also known as conducting or vascular tissue
- It helps in transporting organic material, water, and minerals up and down in the plant
Complex Permanent Tissue is of two types :
- Xylem
- Phloem
Xylem
Xylem is the vascular tissue in plants that transports water and dissolved nutrients upward from the roots.
Xylem consists of four types of cells
(i)Tracheids: -- Elongated angular dead cells involved in the conduction of water
(ii)Vessles:- These are cylindrical tube-like structures placed one above the other end which forms the channel for conduction of water
(iii)Xylem parenchyma:- Thick cells used for storage of food (starch)
(iv)Xylem sclerenchyma:- Non-living fibers with thick walls and narrow cavities provide mechanical support.
Phloem
Phloem is the vascular tissue in plants that conducts sugars and other metabolic products, upward and downwards from the leaves
It consists of four types of cells
(i) Sieve tubes:- Transport organic compounds (sugar) made during photosynthesis
(ii) Companion cells:- Regulate the activity of sugar in sieve tubes
(iii) Phloem fibers:- Provide mechanical support to sieve tubes
(iv) Phloem parenchyma:- It stores food
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ANIMAL TISSUES
1. Epithelium Tissue
2. Connective Tissue
3. Muscular Tissue
4. Nervous Tissue
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Epithelium Tissues are classified into four parts: -
(i) Squamous Epithelium
- Cells arranged end to end like - tiles on the floor
- It forms the lining of cavities - mouth, esophagus, nose, alveoli, etc
- It also forms blood vessels, covering of tongue and skin
- Epithelial cells are arranged in many layers to prevent wear and tear in the skin
(ii) Cubical Epithelium
- Cell of this tissue are cube in shape
- It is found in the kidney, thyroid vesicles, and in glands (salivary glands, sweat glands, etc).
- It also provides mechanical support
- It forms germinal epithelium like - testes and ovaries
(iii) Columnar Epithelium
- Pillar like structure
- It forms the lining of the stomach
- It also forms small intestine, large intestine, etc
- It has threads on its surface which help in the absorption
(iv) Stratified Squamous Epithelium
- It consists of squamous Epithelial arranged in layers
- Present in the uterine, esophagus, etc.
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2. Connective Tissue is classified into four parts:-
The cells of the connective tissue are widely spaced The basic function is to provide support and connect different organs.
(i) Areolar Tissue
- This tissue fills spaces inside organs and is found between the skin and muscles, around blood vessels, nerves, and in the bone marrow.
(ii) Adipose Tissue
- It is found below the skin around the heart, brain and below eyeballs, It acts as an insulator and prevents loss of heat from the body
(iii) Skeletal Tissue
Bone
- It forms the framework that supports the body.
- It is non-flexible. Made up of calcium and phosphorus compounds.
Ligaments
- Two bones are connected to each other by a ligament
- This is very elastic
Tendons
- It connects muscles to bones.
- It is fibrous with great strength and limited flexibility.
Cartilage
- This is elastic, less hard to other bones.
- It is composed of protein and sugars. It is present in the nose, ear, and larynx
(iv) Fluid / Vascular Tissue -Types of blood cells
- Blood helps in the transportation of many substances like - gases, hormones, etc.
- Blood has a fluid matrix called Plasma In which RBCs, WBCs, Platelets are suspended. It also contains proteins, salts, and hormones.
RBCs - It contains red-colored respiratory pigment called hemoglobin that helps in the transportation of oxygen
WBCs - They protects our body from harmful bacteria
Platelets - It is involved in the clotting of blood.
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3. Muscular Tissue
- Movement happens in our body with the help of muscular tissue.
- They are capable of contraction and relaxation.
Muscular Tissue are three types :
(i) Striated Muscles / Skeletal Muscles
- These muscles are attached to the skeleton by tendons, Voluntary.
- These muscles get tired and need rest. Cells of this are multinucleated and unbranched.
- It contains a special protein called contractile protein, which contracts and relax to cause movement.
(ii) Smooth Muscles
- These muscles are involuntary, uninucleated, and spindle-shaped.
- These are found in the walls of the stomach, intestine, bronchi, iris of the eye
(iii) Cardiac Muscles
- These muscles are involuntary.
- Only found in the wall of the heart.
- These are uninucleated and branched.
- In these muscles, rhythmic contraction and relaxation occur throughout life.
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4. Nervous Tissue
Cells of the nervous tissue are highly specialized for being stimulated and then transmitting to stimulus very rapidly from one place to another. The brain, spinal cord, and nerves are all composed of nervous tissue.
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SOME MORE IMPORTANT TERMS
1. Division of Labour in Multicellular Organisms. In multicellular organisms cells are differentiated into a different group of cells, called tissues, to perform different functions i.e., division labor in carrying out life processes. While in unicellular organisms a single cell performs all the life processes.
2. Cell Differentiation. The process by which cells are specialized to do the specific functions and form permanent tissues is called cell differentiation.
3. Pits. Oblique Thin areas (unlignified) found in the walls of sclerenchyma cells and tracheids and vessels of xylem are called pits.
4. Corpuscles. The cells found in the blood plasma are called corpuscles. These are red blood corpuscles (RBC) and white blood corpuscles (WBC)
5. Matrix. Matrix means a medium in which cells are dispersed. It may be solid bone or cartilage and fluid as in blood.
6. Cyton. The cell body of a neuron has a nucleus and cytoplasm
7. Dendrites: The fine fibers arising cell body of a neuron.
8. Axon. The single elongated fiber, also called nerve fiber, arises from the cell body of a neuron.
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