Knowt
Chapter 6-Tissues
There are millions of cells present in multicellular creatures. The majority of these cells are specialised to perform particular tasks. A different group of cells performs each specialised function. These cells are extremely effective since they only do one specific task.
In humans, blood flows to deliver oxygen, food, hormones, waste products, and muscle cells contract and relax to generate movement.
Nerve cells also transmit signals.
Vascular tissues of plants transport nutrients and water from one area of the plant to another. Multicellular organisms thus display the division of labour.
In the body, cells with specialised functions are frequently clustered together. This indicates that a group of cells at a time perform a specific function.
This collection of cells, known as a tissue, is arranged and constructed to provide the best level of functional efficiency. Among tissues include blood, phloem, and muscle.
A tissue is basically a collection of cells that have structural similarities and/or cooperate to perform a certain function.
Types of tissue
Plant tissue-These are of two types
MERISTEMATIC TISSUE-There are only a few places where plants can grow. This is due to the fact that only at these places does the dividing tissue, also known as meristematic tissue, exist.So it is located at the growing parts of plant such as stem and roots.Their function is to help in plant growth.
Depending on the region where they are present, meristematic tissues are classified as apical, lateral and intercalary
Apical meristem-Apical meristem is present at the growing tips of stems and roots and increases the length of the stem and the root.
Lateral meristem(also called cambium)-The girth of the stem or root increases due to lateral meristem.It present in stem and roots.
Intercalary meristem- It seen in some plants is located near the node.The intercalary meristem's job is to promote the lengthening of the stem and the growth of the plant's height.
CHARACTERISTICS OF MERISTEMATIC TISSUE
Meristematic tissue cells contain large nuclei
abundant cytoplasm
thin cellulose walls.
They are also exceedingly active.
Vacuoles are not present.
PERMANENT TISSUE-How do the cells created by meristematic tissue behave? They stop being able to divide as they adopt a certain role. They consequently create a permanent tissue.
The process of taking up a permanent shape, size, and a function is called differentiation. Differentiation leads to the development of various types of permanent tissues.
SIMPLE PERMANENT TISSUE-A few layers of cells beneath the epidermis are generally simple permanent tissue.Types-Parenchyma,collenchyma,sclerenchyma
PARENCHYMA
Parenchyma is the most common simple permanent tissue .
It consists of relatively unspecialised cells with thin cell walls.
They are living cells.
They are usually loosely arranged, thus large spaces between cells (intercellular spaces) are found in this tissue.
This tissue generally stores food.
In some situations, it contains chlorophyll and performs photosynthesis, and then it is called chlorenchyma. In aquatic plants, large air cavities are present in parenchyma to help them float. Such a parenchyma type is called aerenchyma.
COLLENCHYMA
The flexibility in plants is due to another permanent tissue, collenchyma.
It allows bending of various parts of a plant like tendrils and stems of climbers without breaking.
It also provides mechanical support.
We can find this tissue in leaf stalks below the epidermis.
The cells of this tissue are living, elongated and irregularly thickened at the corners.
There is very little intercellular space
made up of cellulose and pectin
SCLERENCHYMA
It is the tissue which makes the plant hard and stiff.
We have seen the husk of a coconut.
It is made of sclerenchymatous tissue.
The cells of this tissue are dead.
They are long and narrow as the walls are thickened due to lignin.
Often these walls are so thick that there is no internal space inside the cell .
This tissue is present in stems, around vascular bundles, in the veins of leaves and in the hard covering of seeds and nuts.
It provides strength to the plant parts.
EPIDERMAL CELLS
The epidermis is the outermost layer of cells
Typically, there is only one layer of cells that make up the epidermis.
The epidermis of some plants found in arid environments may be thicker because preventing water loss is so important.
An epidermis is the outer layer that covers a plant's entire surface.
It safeguards every component of the plant.
On their outer surface, epidermal cells on the plant's aerial portions frequently generate a waxy, water-repellent coating. This helps provide defence against water loss, mechanical damage, and invasion by parasitic fungus.
The cells of epidermal tissue create a continuous layer with no intercellular gaps since it has a protective function to play.
The majority of epidermal cells are fairly flat.
STOMATA
The epidermis of the leaf has tiny pores. We refer to these pores as stomata.
Two kidney-shaped cells termed guard cells surround the stomata.
For the exchange of gases with the atmosphere, they are essential. Stomata are also used for transpiration, which is the loss of water in the form of water vapour from the aerial parts of the plant.
EPIDERMAL CELLS OF ROOTS
The roots' epidermal cells, which are responsible for absorbing water, frequently have long hair-like extensions that significantly enhance the total absorptive surface area.
Some plants, such as desert plants, have epidermis that is covered in a thick waxy covering of a chemical compound called cutin that has waterproof properties.
The protective tissue on the outside of plants changes as they age.
The cork is made up of layers of cells that are formed by a strip of secondary meristem in the cortex. Cork cells are dead, tightly packed together, and devoid of intercellular gaps.
Additionally, they feature a chemical called suberin in their walls that renders them water and gas impermeable.
COMPLEX PERMANENT TISSUE-
More than one type of cell makes for complex tissues. These cells work together in concert to carry out a single task. Examples of such complex tissues are the xylem and phloem. They both make up a vascular bundle and are conducting tissues.
XYLEM
Tracheids, vessels, xylem parenchyma, and xylem fibres make up xylem.
In mature tracheids and vessels, many of the cells are dead and have thick walls.
Tubular structures include vessels and tracheids. They transport minerals and water vertically upward.
Food is kept in the parenchyma.
The function of xylem fibres is mostly supportive.
PHLOEM
Five different cell types make up phloem: companion cells, sieve cells, sieve tubes, phloem fibres, and phloem parenchyma.
Sieve tubes are cells having tubular walls that are perforated.
Food is moved from leaves to other areas of the plant by phloem.
All phloem cells, with the exception of phloem fibres, are alive cells.
Animal tissue
When we breathe we can actually feel the movement of our chest. For this we have specialised cells called muscle cells.The contraction and relaxation of these cells result in movement.
During breathing we inhale oxygen and it is absorbed in the lungs and then is transported to all the body cells through blood.
Blood flows and carries various substances from one part of the body to the other. For example, it carries oxygen and food to all cells. It also collects wastes from all parts of the body and carries them to the liver and kidney for disposal.
Blood and muscles are both examples of tissues found in our body. On the basis of the functions they perform we can think of different types of animal tissues, such as epithelial tissue, connective tissue, muscular tissue and nervous tissue. Blood is a type of connective tissue, and muscle forms muscular tissue.
Types of Animal tissue
EPITHELIAL TISSUE
Animal epithelial tissues serve as the body's covering or protective tissues.
The majority of the body's cavities and organs are covered in epithelium.
Additionally, it functions as a partition to keep various bodily systems apart.
Epithelial tissue is found in the skin, blood vessels, kidney tubules, lung alveoli, and the lining of the mouth.
The cells of epithelial tissue are closely spaced out and form a continuous sheet.
They hardly have any intercellular spaces, and there is very little cementing material between them.
Anything entering or exiting the body must undoubtedly pass through at least one layer of epithelium.
Squamous epithelial tissue
Simple squamous epithelial tissue is a straightforward flat type of epithelium in cells lining blood arteries or lung alveoli, where transit of chemicals happens through a selectively permeable surface.
Simple squamous epithelial cells form a fragile lining and are incredibly flat and thin.
Squamous epithelium also lines the lining of the mouth and the oesophagus.
Squamous epithelium is also a component of the body's protective skin. To prevent deterioration, skin epithelial cells are organised into numerous layers. The epithelium is known as stratified squamous epithelium because of the way its layers are structured.
Columnar epithelial tissue
Tall columnar epithelial cells are present in the inner lining of the intestine and they are responsible for absorption and secretion
This "pillar-like" columnar epithelium makes it easier to pass through the epithelial barrier.
Cilia, which are hair-like projections on the outer surfaces of epithelial cells, are also present in the columnar epithelial tissue of the respiratory tract.
These cilia may move, and when they do, the mucus is forced forward to be cleared.This type of epithelium is thus ciliated columnar epithelium.
Cuboidal epithelial tissue
The lining of kidney tubules and salivary gland ducts is composed of cuboidal epithelium, which provides mechanical support.
Since gland cells have the ability to produce chemicals at the epithelial surface, epithelial cells frequently develop further specialisation.
A multicellular gland can form when an area of the epithelial tissue folds inward called glandular epithelium.
CONNECTIVE TISSUE
The cells of connective tissue are loosely spaced and embedded in an intercellular matrix.
The matrix may be jelly like, fluid, dense or rigid.
The nature of matrix differs in concordance with the function of the particular connective tissue.
BLOOD
Blood has a fluid (liquid) matrix called plasma, in which red blood corpuscles (RBCs), white blood corpuscles (WBCs) and platelets are suspended.
The plasma contains proteins, salts and hormones.
Blood flows and transports gases, digested food, hormones and waste materials to different parts of the body.
BONE
Bone is another example of a connective tissue. It forms the framework that supports the body.
It also anchors the muscles and supports the main organs of the body.
It is a strong and nonflexible tissue .
Bone cells are embedded in a hard matrix that is composed of calcium and phosphorus compounds.
TENDONS AND LIGAMENT
Two bones can be connected to each other by another type of connective tissue called the ligament.
This tissue is very elastic.
It has considerable strength.
Ligaments contain very little matrix and connect bones with bones.
Tendons connect muscles to bones and are another type of connective tissue.
Tendons are fibrous tissue with great strength but limited flexibility.
CARTILAGE
Cells in cartilage, another form of connective tissue, are widely spaced.
Proteins and carbohydrates make up the solid matrix.
The nose, ear, trachea, and larynx all contain cartilage.
It smooths the surfaces of bones at joints.
The ear cartilage may be folded, but the bones in our arms cannot.
AREOLAR CONNECTIVE TISSUE
Areolar connective tissue can be found in the bone marrow, around blood vessels and nerves, and between the skin and muscles.
It supports internal organs, fills the space inside the organs, and aids in tissue restoration.
ADIPOSE TISSUE
Under the epidermis and in between internal organs, there is adipose tissue that stores fat.
This tissue has globules of fat inside its cells.
It can function as an insulator by storing lipids.
MUSCULAR TISSUE
VOLUNTARY OR STRIATED MUSCLES
Elongated cells, often known as muscle fibres, make up muscular tissue.
This tissue is responsible for movement in our body.
Contractile proteins are unique proteins found in muscles that contract and relax to produce movement.
These muscles are also called skeletal muscles as they are mostly attached to bones and help in body movement.
Under the microscope, these muscles show alternate light and dark bands or striations when stained appropriately.
As a result, they are also called striated muscles. The cells of this tissue are long, cylindrical, unbranched and multinucleate (having many nuclei).
INVOLUNTARY OR UNSTRIATED MUSCLES
The movement of food in the alimentary canal or the contraction and relaxation of blood vessels are involuntary movements(function)
Such movements are controlled by smooth muscles or involuntary muscles.
They are also found in the iris of the eye, in ureters and in the bronchi of the lungs.
The cells are uninucleate (containing a single nucleus), long with pointed ends, and spindle-shaped. Another name for them is unstriated muscles.
CARDIAC MUSCLES
Throughout life, the heart's muscles show cyclic contraction and relaxation.(function)
These involuntary muscles are called cardiac muscles.
Cylindrical, branching, and uninucleate characterize heart muscle cells.
NERVOUS TISSUE
All cells possess the ability to respond to stimuli.
The nervous system's cells are extremely specialised for receiving stimulation and then rapidly conveying that stimulus throughout the body.(function)
The brain, spinal cord and nerves are all composed of the nervous tissue
The cells of this tissue are called nerve cells or neurons.
A neuron is made up of a cell body, which has a nucleus and cytoplasm, and long, thin portions that resemble hairs. Each neuron typically consists of one long portion, known as the axon, and numerous shorter, branched parts, known as dendrites.
An individual nerve cell may be up to a metre long. Many nerve fibres bound together by connective tissue make up a nerve.
The signal that passes along the nerve fibre is called a nerve impulse. Nerve impulses allow us to move our muscles when we want to.
The functional combination of nerve and muscle tissue is fundamental to most animals. This combination enables animals to move rapidly in response to stimuli.
Chapter 6-Tissues
There are millions of cells present in multicellular creatures. The majority of these cells are specialised to perform particular tasks. A different group of cells performs each specialised function. These cells are extremely effective since they only do one specific task.
In humans, blood flows to deliver oxygen, food, hormones, waste products, and muscle cells contract and relax to generate movement.
Nerve cells also transmit signals.
Vascular tissues of plants transport nutrients and water from one area of the plant to another. Multicellular organisms thus display the division of labour.
In the body, cells with specialised functions are frequently clustered together. This indicates that a group of cells at a time perform a specific function.
This collection of cells, known as a tissue, is arranged and constructed to provide the best level of functional efficiency. Among tissues include blood, phloem, and muscle.
A tissue is basically a collection of cells that have structural similarities and/or cooperate to perform a certain function.
Types of tissue
Plant tissue-These are of two types
MERISTEMATIC TISSUE-There are only a few places where plants can grow. This is due to the fact that only at these places does the dividing tissue, also known as meristematic tissue, exist.So it is located at the growing parts of plant such as stem and roots.Their function is to help in plant growth.
Depending on the region where they are present, meristematic tissues are classified as apical, lateral and intercalary
Apical meristem-Apical meristem is present at the growing tips of stems and roots and increases the length of the stem and the root.
Lateral meristem(also called cambium)-The girth of the stem or root increases due to lateral meristem.It present in stem and roots.
Intercalary meristem- It seen in some plants is located near the node.The intercalary meristem's job is to promote the lengthening of the stem and the growth of the plant's height.
CHARACTERISTICS OF MERISTEMATIC TISSUE
Meristematic tissue cells contain large nuclei
abundant cytoplasm
thin cellulose walls.
They are also exceedingly active.
Vacuoles are not present.
PERMANENT TISSUE-How do the cells created by meristematic tissue behave? They stop being able to divide as they adopt a certain role. They consequently create a permanent tissue.
The process of taking up a permanent shape, size, and a function is called differentiation. Differentiation leads to the development of various types of permanent tissues.
SIMPLE PERMANENT TISSUE-A few layers of cells beneath the epidermis are generally simple permanent tissue.Types-Parenchyma,collenchyma,sclerenchyma
PARENCHYMA
Parenchyma is the most common simple permanent tissue .
It consists of relatively unspecialised cells with thin cell walls.
They are living cells.
They are usually loosely arranged, thus large spaces between cells (intercellular spaces) are found in this tissue.
This tissue generally stores food.
In some situations, it contains chlorophyll and performs photosynthesis, and then it is called chlorenchyma. In aquatic plants, large air cavities are present in parenchyma to help them float. Such a parenchyma type is called aerenchyma.
COLLENCHYMA
The flexibility in plants is due to another permanent tissue, collenchyma.
It allows bending of various parts of a plant like tendrils and stems of climbers without breaking.
It also provides mechanical support.
We can find this tissue in leaf stalks below the epidermis.
The cells of this tissue are living, elongated and irregularly thickened at the corners.
There is very little intercellular space
made up of cellulose and pectin
SCLERENCHYMA
It is the tissue which makes the plant hard and stiff.
We have seen the husk of a coconut.
It is made of sclerenchymatous tissue.
The cells of this tissue are dead.
They are long and narrow as the walls are thickened due to lignin.
Often these walls are so thick that there is no internal space inside the cell .
This tissue is present in stems, around vascular bundles, in the veins of leaves and in the hard covering of seeds and nuts.
It provides strength to the plant parts.
EPIDERMAL CELLS
The epidermis is the outermost layer of cells
Typically, there is only one layer of cells that make up the epidermis.
The epidermis of some plants found in arid environments may be thicker because preventing water loss is so important.
An epidermis is the outer layer that covers a plant's entire surface.
It safeguards every component of the plant.
On their outer surface, epidermal cells on the plant's aerial portions frequently generate a waxy, water-repellent coating. This helps provide defence against water loss, mechanical damage, and invasion by parasitic fungus.
The cells of epidermal tissue create a continuous layer with no intercellular gaps since it has a protective function to play.
The majority of epidermal cells are fairly flat.
STOMATA
The epidermis of the leaf has tiny pores. We refer to these pores as stomata.
Two kidney-shaped cells termed guard cells surround the stomata.
For the exchange of gases with the atmosphere, they are essential. Stomata are also used for transpiration, which is the loss of water in the form of water vapour from the aerial parts of the plant.
EPIDERMAL CELLS OF ROOTS
The roots' epidermal cells, which are responsible for absorbing water, frequently have long hair-like extensions that significantly enhance the total absorptive surface area.
Some plants, such as desert plants, have epidermis that is covered in a thick waxy covering of a chemical compound called cutin that has waterproof properties.
The protective tissue on the outside of plants changes as they age.
The cork is made up of layers of cells that are formed by a strip of secondary meristem in the cortex. Cork cells are dead, tightly packed together, and devoid of intercellular gaps.
Additionally, they feature a chemical called suberin in their walls that renders them water and gas impermeable.
COMPLEX PERMANENT TISSUE-
More than one type of cell makes for complex tissues. These cells work together in concert to carry out a single task. Examples of such complex tissues are the xylem and phloem. They both make up a vascular bundle and are conducting tissues.
XYLEM
Tracheids, vessels, xylem parenchyma, and xylem fibres make up xylem.
In mature tracheids and vessels, many of the cells are dead and have thick walls.
Tubular structures include vessels and tracheids. They transport minerals and water vertically upward.
Food is kept in the parenchyma.
The function of xylem fibres is mostly supportive.
PHLOEM
Five different cell types make up phloem: companion cells, sieve cells, sieve tubes, phloem fibres, and phloem parenchyma.
Sieve tubes are cells having tubular walls that are perforated.
Food is moved from leaves to other areas of the plant by phloem.
All phloem cells, with the exception of phloem fibres, are alive cells.
Animal tissue
When we breathe we can actually feel the movement of our chest. For this we have specialised cells called muscle cells.The contraction and relaxation of these cells result in movement.
During breathing we inhale oxygen and it is absorbed in the lungs and then is transported to all the body cells through blood.
Blood flows and carries various substances from one part of the body to the other. For example, it carries oxygen and food to all cells. It also collects wastes from all parts of the body and carries them to the liver and kidney for disposal.
Blood and muscles are both examples of tissues found in our body. On the basis of the functions they perform we can think of different types of animal tissues, such as epithelial tissue, connective tissue, muscular tissue and nervous tissue. Blood is a type of connective tissue, and muscle forms muscular tissue.
Types of Animal tissue
EPITHELIAL TISSUE
Animal epithelial tissues serve as the body's covering or protective tissues.
The majority of the body's cavities and organs are covered in epithelium.
Additionally, it functions as a partition to keep various bodily systems apart.
Epithelial tissue is found in the skin, blood vessels, kidney tubules, lung alveoli, and the lining of the mouth.
The cells of epithelial tissue are closely spaced out and form a continuous sheet.
They hardly have any intercellular spaces, and there is very little cementing material between them.
Anything entering or exiting the body must undoubtedly pass through at least one layer of epithelium.
Squamous epithelial tissue
Simple squamous epithelial tissue is a straightforward flat type of epithelium in cells lining blood arteries or lung alveoli, where transit of chemicals happens through a selectively permeable surface.
Simple squamous epithelial cells form a fragile lining and are incredibly flat and thin.
Squamous epithelium also lines the lining of the mouth and the oesophagus.
Squamous epithelium is also a component of the body's protective skin. To prevent deterioration, skin epithelial cells are organised into numerous layers. The epithelium is known as stratified squamous epithelium because of the way its layers are structured.
Columnar epithelial tissue
Tall columnar epithelial cells are present in the inner lining of the intestine and they are responsible for absorption and secretion
This "pillar-like" columnar epithelium makes it easier to pass through the epithelial barrier.
Cilia, which are hair-like projections on the outer surfaces of epithelial cells, are also present in the columnar epithelial tissue of the respiratory tract.
These cilia may move, and when they do, the mucus is forced forward to be cleared.This type of epithelium is thus ciliated columnar epithelium.
Cuboidal epithelial tissue
The lining of kidney tubules and salivary gland ducts is composed of cuboidal epithelium, which provides mechanical support.
Since gland cells have the ability to produce chemicals at the epithelial surface, epithelial cells frequently develop further specialisation.
A multicellular gland can form when an area of the epithelial tissue folds inward called glandular epithelium.
CONNECTIVE TISSUE
The cells of connective tissue are loosely spaced and embedded in an intercellular matrix.
The matrix may be jelly like, fluid, dense or rigid.
The nature of matrix differs in concordance with the function of the particular connective tissue.
BLOOD
Blood has a fluid (liquid) matrix called plasma, in which red blood corpuscles (RBCs), white blood corpuscles (WBCs) and platelets are suspended.
The plasma contains proteins, salts and hormones.
Blood flows and transports gases, digested food, hormones and waste materials to different parts of the body.
BONE
Bone is another example of a connective tissue. It forms the framework that supports the body.
It also anchors the muscles and supports the main organs of the body.
It is a strong and nonflexible tissue .
Bone cells are embedded in a hard matrix that is composed of calcium and phosphorus compounds.
TENDONS AND LIGAMENT
Two bones can be connected to each other by another type of connective tissue called the ligament.
This tissue is very elastic.
It has considerable strength.
Ligaments contain very little matrix and connect bones with bones.
Tendons connect muscles to bones and are another type of connective tissue.
Tendons are fibrous tissue with great strength but limited flexibility.
CARTILAGE
Cells in cartilage, another form of connective tissue, are widely spaced.
Proteins and carbohydrates make up the solid matrix.
The nose, ear, trachea, and larynx all contain cartilage.
It smooths the surfaces of bones at joints.
The ear cartilage may be folded, but the bones in our arms cannot.
AREOLAR CONNECTIVE TISSUE
Areolar connective tissue can be found in the bone marrow, around blood vessels and nerves, and between the skin and muscles.
It supports internal organs, fills the space inside the organs, and aids in tissue restoration.
ADIPOSE TISSUE
Under the epidermis and in between internal organs, there is adipose tissue that stores fat.
This tissue has globules of fat inside its cells.
It can function as an insulator by storing lipids.
MUSCULAR TISSUE
VOLUNTARY OR STRIATED MUSCLES
Elongated cells, often known as muscle fibres, make up muscular tissue.
This tissue is responsible for movement in our body.
Contractile proteins are unique proteins found in muscles that contract and relax to produce movement.
These muscles are also called skeletal muscles as they are mostly attached to bones and help in body movement.
Under the microscope, these muscles show alternate light and dark bands or striations when stained appropriately.
As a result, they are also called striated muscles. The cells of this tissue are long, cylindrical, unbranched and multinucleate (having many nuclei).
INVOLUNTARY OR UNSTRIATED MUSCLES
The movement of food in the alimentary canal or the contraction and relaxation of blood vessels are involuntary movements(function)
Such movements are controlled by smooth muscles or involuntary muscles.
They are also found in the iris of the eye, in ureters and in the bronchi of the lungs.
The cells are uninucleate (containing a single nucleus), long with pointed ends, and spindle-shaped. Another name for them is unstriated muscles.
CARDIAC MUSCLES
Throughout life, the heart's muscles show cyclic contraction and relaxation.(function)
These involuntary muscles are called cardiac muscles.
Cylindrical, branching, and uninucleate characterize heart muscle cells.
NERVOUS TISSUE
All cells possess the ability to respond to stimuli.
The nervous system's cells are extremely specialised for receiving stimulation and then rapidly conveying that stimulus throughout the body.(function)
The brain, spinal cord and nerves are all composed of the nervous tissue
The cells of this tissue are called nerve cells or neurons.
A neuron is made up of a cell body, which has a nucleus and cytoplasm, and long, thin portions that resemble hairs. Each neuron typically consists of one long portion, known as the axon, and numerous shorter, branched parts, known as dendrites.
An individual nerve cell may be up to a metre long. Many nerve fibres bound together by connective tissue make up a nerve.
The signal that passes along the nerve fibre is called a nerve impulse. Nerve impulses allow us to move our muscles when we want to.
The functional combination of nerve and muscle tissue is fundamental to most animals. This combination enables animals to move rapidly in response to stimuli.
