Categories \(\Rightarrow\) Class IX Class X Class XI Mathematics Physics Chemistry Biology

Tissues

Tissue is defined as a group of similar cells that work together to perform a specific function. Tissues are a cellular organisational level that falls between cells and organ systems.

Key Factors - Tissues

  • Tissues are groups of cells that have a similar structure and shape.
  • Tissues are designed to work together to achieve maximum efficiency in their functions.
  • Examples of tissues include blood, muscle, and phloem
  • The study of tissues is known as histology.
  • The word tissue comes from an old French verb meaning “to weave”.

Types of Tissues in Animals

  • Connective Tissue
  • Muscle Tissue
  • Nervous Tissue
  • Epithelial Tissue

How tissues form organs

Organs are created by combining the functional groups of tissues.
For example, blood, muscle, and phloem are all tissues that are specialised for particular tasks.

MERISTEMATIC TISSUE

Meristematic tissue is a plant tissue made of cells that divide continuously to promote plant growth. It occurs in the growing tips of shoots and roots, as well as in the base of leaves.

Types of meristematic tissue

  • Apical meristem: Located at the tips of roots (RAM-Root Apical Meristem) and shoots (SAM-Shoot Apical Meristem), this meristem is responsible for vertical growth.
  • Lateral meristem: Located along the stem, this meristem is responsible for lateral growth or increase in width.
  • Intercalary meristem: Located at the base of leaves or internodes, this meristem increases the length of the plant. Present only in grasses, e.g. sugarcane, bamboo, grasses

Differences between Apical and Lateral Meristems

Apical Meristem Lateral Meristem
Occurs at the apex of the stem, root and their branches Found in lateral positions parallel to the circumference of the organs
It is a primary meristem It is a secondary meristem
Cells divide in different planes Cells divide in one plane periclinally, both on the outer and inner side
It produces primary tissue It gives rise to secondary tissue
It brings growth in length It causes growth in girth and thickness

Functions of meristematic tissue

  • Meristematic tissue helps increase the length and girth of the plant.
  • It generates secondary tissues such as wood and cork.
  • It contributes to the formation of new organs and their development.
  • It restores growth if root development is halted or the root tip is injured.

Final Cell Differentiation

Meristematic cells

Meristematic cells are undifferentiated cells capable of continuous cell division. They have a big nucleus that is absent from the vacuole. There is no intercellular gap between the cells.
Meristematic tissues divide and differentiate to form the permanent tissues.
Undifferentiated cells are immature, unspecialized biological cells that have not yet developed a specific function or structure;

PERMANENT TISSUES

Permanent tissue in plants is tissue that has lost the ability to divide and has differentiated to perform specific functions.
Differentiated cells are specialised cells that have developed from less specialised cells (like stem cells) into a mature, specific cell type with a distinct structure and function.

Characteristics of Permanent Tissues

  • Permanent tissues are derived from meristematic tissues
  • They have thick cell walls and large vacuoles
  • They have different shapes related to the function they perform
  • They have less cytoplasm as compared to meristematic tissues

Types of permanent tissue

Simple permanent tissue
These tissues perform the same function and have a similar shape. They are made up of a single type of cell.
They can be classified into three types:
  • Parenchyma
    • Chlorenchyma: chrorophyl containing Tissue
    • Aerenchyma: Air cavities found in aquatic plants
  • Collenchyma
  • Sclerenchyma
Complex permanent tissue
These tissues are made up of different types of cells. They are also known as vascular tissues as they're formed of vascular bundles.
The two main types of complex permanent tissues are
  • Xylem
  • Phloem

types-of-simple-cell

Diffrenece between Simple and Complex Tissues
Properties Simple Tissue Complex Tissue
Cell Composition Made of a single, homogeneous type of cell Composed of multiple different cell types (heterogeneous) that are arranged into a single tissue
Function Perform basic, uniform functions such as storage and providing support Perform specialised functions, most notably the transport of water, minerals, and food throughout the plant
Origin and Structure All cells in a simple tissue share a common origin and structure The different cells within a complex tissue have different structures and origins
Examples Parenchyma,Collenchyma & Sclerenchyma Xylem and Phloem

How permanent tissues are formed

The process by which the meristematic tissues develop into different types of permanent tissues is called differentiation. This differentiation happens based on the location and requirements of the plant.

Parenchyma
Parenchyma is a type of tissue found in plants and animals. In plants, it's the most common and abundant tissue that makes up the bulk of leaves, flowers, and the inner parts of stems and roots. In animals, It's the functional tissue of organs like the brain.
    Plant parenchyma
    • Characteristics: Thin-walled, living cells that can divide even when mature
    • Functions: Store food and water, photosynthesis, regeneration and wound healing
    • Location: Leaves, fruits, flowers, soft areas of stems, roots, and leaves
    • Types: Simple parenchyma, chlorenchyma, xylem parenchyma, and phloem parenchyma
    Animal parenchyma
      Characteristics: The functional tissue of organs like the brain
    • Components: Neurons, glial cells, and collagen proteins
    • Functions: Performs the work of the organ
    • Damage: Damage or trauma to the brain parenchyma can result in a loss of cognitive ability or even death
Parenchyma cells are important for regeneration and wound healing because they are living cells that can divide when they are mature.

Collenchyma

Collenchyma is a plant tissue that provides support and structure to young plants. It's made up of elongated cells with thickened cell walls. Collenchyma cells are found in the petioles, midribs, and stems of leaves.

    Characteristics
    • Cell shape: Elongated, spherical, oval, or polygonal
    • Cell wall: Thickened, unevenly, and mostly at the corners
    • Cell contents: Contain cellulose, hemicellulose, and pectin
    • Intercellular spaces: Mostly absent, but can be present in lacunar collenchyma Chloroplasts: Often contain chloroplasts and store food
    Types of collenchyma
    • Tangential: has primary cell thickenings in the internal and external tangential walls Annular: has uniformly thickened cells that appear circular in cross-section Lacunar: has intercellular spaces and more pronounced wall thickening near them Angular: has material that causes thickening deposited at angles or corners of the cell
    Function: Collenchyma provides support and structure to the petiole, leaf veins, and stem of young plants. It allows for easy bending without breakage.

Sclerenchyma

Sclerenchyma is a plant tissue that gives strength and stiffness to plants. It is made up of dead cells with thickened cell walls. Sclerenchyma is found in the stems, roots, leaves, and seeds of plants.

    Characteristics:
    • Sclerenchyma cells have two types of cell walls: primary and secondary.
    • The secondary wall is very thick and made of cellulose, hemicellulose, and lignin.
    • Sclerenchyma cells are long and narrow in shape.
    • Sclerenchyma cells are the main supporting cells in plant tissues that have stopped growing.
      • Sclerenchyma cells are found in the veins of leaves and roots, stems around vascular bundles, and the hard covering of seeds.
    Types of sclerenchyma cells:
    • The two main types of sclerenchyma cells are Fibres and sclereids.
    • Fibres are very elongated cells that can be found in stems, roots, and vascular bundles in leaves.
    Economic importance:
    • Sclerenchyma Fibres are used to make many fabrics, such as flax, hemp, jute, and ramie.
    • Sclerenchyma provides hardness to stony fruits such as nuts, coconuts, and almonds.
Properties Parenchyma Collenchyma Slerenchyma
Cell Wall Thin and flexible, made of cellulose Thickened at the corners due to deposition of cellulose, pectin and hemicellulose Thick, lignified and rigid, made of lignin
Cell Shape Oval or round Elongated Long and Narrow
Cell Viability Living at maturity Living Dead at maturity
Location Found in the soft part of the plant, like leaves, stems and fruits Hypodermic, petioles of leave, stem tendrils Found in the mature part of the plant, providing structural support
Functions Perform various functions like storage, photosynthesis and tissue repair Provides mechanical support and tensile strength to growing organs, helps in the bending of plants Provide structural support and protection, e.g. coconut husk

Xylem

Xylem is a tissue in plants that transports water and nutrients from the roots to the stems and leaves. It also provides structural support to the plant.

    How does xylem work?
    • Xylem is part of the vascular bundle in plants, along with phloem.
    • Xylem is formed from actively dividing cells in the root and shoot tips.
    • In woody plants, secondary xylem forms a ring around the primary xylem as the plant grows.
    • The primary xylem cells die and form a hard skeleton that supports the plant.
    • In the trunk of a tree, the outer secondary xylem conducts water, while the inner part is made of dead primary xylem.
    Types of xylem cells
    • Xylem vessels are long, tube-like dead cells that are placed one above the other.
    • Tracheids are long, tapering dead cells that help conduct water.
    • The parenchyma stores food
    • Xylem Fibres are also dead cells and are mainly supportive in function.

complex-tissue
complex-tissue

Phloem

Phloem is a living tissue in plants that carries food from the leaves to the rest of the plant. It's part of the vascular tissue system.

    How does phloem work?
    • Phloem carries sugars, amino acids, and signalling molecules.
    • It's responsible for long-distance transport.
    • Phloem carries photosynthates, or soluble organic compounds, from the leaves to the rest of the plant.
    • This process is called translocation.
    • Phloem carries resources to heterotrophic organs, like flowers, fruits, and roots.
    • Phloem also helps the plant respond to internal and external stimuli.
    Where is phloem found in a tree?
    • In a tree, the phloem is the inner bark, or the band of tissue outside of the cambium.
    • The phloem lives for a short time, then dies and turns to cork, becoming part of the protective outer bark.

Difference between Xylem and Phloem

Properties Xylem Phloem
Functions Carries Water and Minerals Carries Food
Cell Type Dead Cell Living Cell
Transport Direction One way-up side of the plan All around the plant
Cell Wall Mage of lignin Made of Cellulose
Structure Long Tubular Vessel Columns of Sieve Tube cells

Sieve Tube

Sieve tubes are living cells in the phloem tissue of vascular plants that tra nsport nutrients throughout the plant. They are made up of elongated cells called sieve tube elements.
    Structure
    • Sieve tubes are made up of elongated cells that are arranged end to end.
    • The ends of the cells are connected by sieve plates, which are porous structures that allow sap to flow between the cells.
    • Sieve tubes are associated with companion cells, which help regulate the function of the sieve tubes.
    Function
    • The main function of sieve tubes is to transport carbohydrates, primarily sucrose, from the leaves to the fruits and roots.
    • Sieve tubes are a major conducting component in the phloem.
    • They work in association with the companion cells to bring about conduction.
    Characteristics
    • Sieve tubes are enucleated, meaning they lack a nucleus at maturity.
    • They have sieve plates at their ends.
    • They are very long and have horizontal end walls.
    • They are shorter and wider so as to provide greater surface area for transport.

Sieve Plates

A sieve plate is a perforated wall that connects sieve tubes in vascular plants. Sieve plates are found in the phloem, a living vascular tissue that transports food throughout the plant.
    How do sieve plates work?
    • Sieve plates are located on the overlapping end walls of sieve tubes.
    • The perforations in sieve plates allow water and dissolved organic solutes to flow through the sieve tubes.
    • Sieve plates are lined with callose, a substance that blocks the pores when the sieve tube is stressed or damaged.
    Why are sieve plates important?
    • Sieve plates connect adjacent tissue cells of phloem.
    • They help pass food and other organic materials to the sieve tubes.
    • They provide support to the phloem tissue.
    How do sieve plates develop?
    • Sieve plates form from the maturity of plasmodesmata, the connection between sieve tubes and companion cells.
    • During early development of young sieve tubes, sieve plates resemble normal cell walls.

Ascent of sap

Ascent of sap is the process by which water and minerals move from the roots of a plant to its leaves and stems. This process occurs against gravity.
    How does it happen?
    • Plants absorb water through their roots.
    • Water is lost from the leaves through transpiration.
    • This creates a transpiration pull, which moves water and minerals up through the xylem tissue of the plant.
    • The xylem tissue is made up of non-living conducting cells, such as tracheids and vessel members.

Translocations

Translocation is a process that occurs in plants to deliver nutrients and other molecules from one place to another throughout the organism. It occurs through the phloem pathway or phloem transport system. The nutrients are translocated in a solute form called phloem sap.

Protective tissue

Plants require protection from the external environment for their survival. Their internal structure and tissues are protected from the external environment by means of specific tissues called protective tissues. These tissues present in a plant's stem, roots, leaves, etc, also help plants by preventing the loss of water.
These tissues protect the plants and also prevent the plants from losing water. There are two types of protective tissue viz.,
  1. Epidermis
  2. Cork (or Phellum)

stem-internal-structure

Epidermis

    A single layer of cells forms the epidermis, and it is the outermost layer of the plant.
    Properties and functions of epidermis:
  • Epidermis cells are mostly flat cells.
  • In epidermis tissue, the outer and sidewalls of the epidermis, cells are thicker than the inner wall.
  • For some plants living in dry habitats, storage of water is significant and critical. So the epidermis layer is thick in those plants to avoid the loss of water.
  • It protects the entire surface of the plant.
  • In aerial parts of the plant, epidermal cells in its outer surface secrete a waxy water-resistant layer. The epidermis of the desert plant has a thick layer of cutin that is called cuticle.
  • In turn, this layer protects the surface of the plant against water loss, mechanical injury, and the parasitic fungi invasion.
  • Epidermal cells is a continuous layer without any intercellular spaces to give protection to the plant.

stomta

Epidermis of leaf

    Outermost layer of the leaf
      It consists of small pores called Stomata
    Functions of stomata
    • Stomata are enclosed by two kidney-shaped guard cells that are necessary for gaseous exchange in the leaf.
    • Stomata also facilitate transpiration, the process by which excess water is lost as water vapour through the surface of the leaves.

leaf-anatomy

Epidermis of roots

Epidermal cells of roots form the outermost layer of long hair-like structures, which creates a larger absorptive surface area.
Epidermal cells help in the absorption of water in roots.

Cork

Cork is constituted by a layer of cells formed by the cortex, located in a strip of secondary meristem. Cork cells are dead and compactly arranged without intercellular spaces. Cork has a substance called suberin in their walls that make it impervious to gases and water.

Cuticle

Cuticle is a waxy layer that covers the epidermis of some plant parts. It protects the plant from water loss and extreme climates like droughts
    What is a cuticle in plants?
    • The cuticle is a non-cellular, waxy layer that covers the epidermis of leaves, stems, fruits, and flowers.
    • It is secreted by the epidermis, which is the outermost layer of the plant.
    • The cuticle is water-resistant and impermeable, which prevents plants from losing water through transpiration.
    • It is beneficial for desert plants because they need to conserve water.
    Why is the cuticle absent on roots?
      If a waxy cuticle were present on roots, it would prevent the roots from absorbing water and salts from the soil.
    What is the function of the cuticle?
    • The cuticle protects the epidermis and prevents excessive loss of water from the surface of the leaves.
    • It helps plants survive in extreme climates like droughts.

ANIMAL TISSUES

epithelial-tissue glandular-ephithelium

EPITHELIAL TISSUE

Epithelial tissue, also known as epithelium, is a body tissue that covers internal and external surfaces, and lines the body cavities, and forms glands. It performs many functions, including protection, secretion, and absorption.

Types of epithelial tissue

  • Squamous epithelium: A thin, flat layer of tissue that lines the mouth and oesophagus. It's semi-permeable, which allows for gaseous exchange.
  • Simple columnar epithelium: A single layer of tall, slender cells that line a basement membrane.
    • transitional-epithelium
  • Simple cuboidal epithelium: A single layer of cube-shaped cells that lines the kidney tubules and respiratory bronchioles.
  • Stratified columnar epithelium: it is made up of two or more than two layers of cells and mostly has a protective function.
  • Glandular epithelium: Produces and releases secretory products like sweat, saliva, breast milk, and digestive enzymes.
  • Transitional epithelium: Also known as urothelium, this tissue consists of several layers of cells that can contract or expand
Epithelial tissue functions in protection, secretion, absorption, and sensation.

Types of Epithelial Tissue Location Structure Function
Simple Squamous Blood vessel lining, air sac lining of lungs A single layer of flat cells having irregular boundaries Transport by diffusion and where minimal protection is required
Simple Cuboidal Epithelium The tubular lining of kidneys, glandular ducts A single layer of short cylindrical cells. It may have microvilli, as in proximal convoluted tubules Absorption and secretion
Simple Columnar Epithelium Digestive tract and upper respiratory tract lining A single layer of columnar cells (tall and slender) and often ciliated Protection, absorption, mucus secretion and movement in a specific direction
Stratified Squamous Epithelium The lining of the mouth and vagina Made up of several layers of cells, continuously sloughed off and regenerated. The older layer of cells is pushed upwards and becomes flat. The lower layer is columnar and metabolically active Protection
Stratified Cuboidal Mammary glands, sweat glands and salivary glands The upper layer is cuboid, and other layers may be cuboidal or other types Protection of ducts of various glands
Stratified Columnar Male urethra and lobar ducts of salivary glands There is a layer of columnar cells present on squamous, columnar or cuboidal epithelial cells Protection and secretion
Pseudostratified Columnar Respiratory passage and ducts of many glands Similar to columnar epithelium, but all the cells are not of similar height Protection, secretion and movement of mucous
Transitional epithelia or urothelium Urinary bladder, urethra, ureter Stratified epithelium, which can contract or expand as per the requirement. Cells are cuboidal when not stretched, but when the organ stretches, then the tissue gets compressed, and cells appear irregular and squamous-shaped Stretch readily to accommodate the different volumes of liquids act as a barrier and have tight junctions to prevent reabsorption of toxic substances
Keratinised The outer or apical layer of the cell Mostly dead and devoid of nucleus and cytoplasm. The cytoplasm gets replaced by keratin, which makes the layer waterproof Protection against abrasion

MUSCULAR TISSUES

muscles Muscular tissue is a type of tissue that is responsible for movement in the body. It is made up of elongated cells called muscle Fibres.

Types of Muscular Tissue

    Striated/Skeletal/Voluntary Muscle
    • These muscles are attached to the skeleton and help in its movement.
    • These muscles are also known as striated muscles because of the presence of alternate patterns of light and dark bands.
    • These light and dark bands are sarcomeres, which are highly organised structures of actin, myosin, and proteins. These add to the contractility and extensibility of the muscles.
    • Skeletal muscles are voluntary muscles composed of muscle Fibres.
    • 40% of our body mass comprises skeletal muscles.
    • Each skeletal tissue contains myofibrils.
    • The cells of these tissues are multinucleated.
    • These are provided with blood vessels and many elongated mitochondria and glycogen granules.
    • They bring about the movement of the organs of the body.
    Smooth/Non Striated/Non Voluntary Muscles
    • These are non-striated, involuntary muscles controlled by the Autonomic Nervous System.
    • It stimulates the contractility of the digestive, urinary, reproductive systems, blood vessels, and airways.
    • The actin and myosin filaments are very thin and arranged randomly, hence no striations.
    • The cells are spindle-shaped with a single nucleus.
    Cardiac muscle
    • These are found only in the heart.
    • These are involuntary muscles, and the heart pumps the blood through cardiac contractions.
    • The cells of the cardiac muscles, known as the cardiomyocytes, are striated.
    • They are single-celled and uninucleated.
    • The ends of the cells are joined, and the junctions are called intercalated discs. The cells are attached to each other by desmosomes.

Difference between striated, unstriated and cardiac muscles
Properties Striated Unstriated cardiac muscles
Structure Cylindrical & unbranched Cell, exhibits light and dark bands called striations, multinucleated, attached to bone and form the bulk of the body's muscle mass Long spindle-shaped and unbranched cells, uninucleated Cylindrical, branched that form a network, exhibits striations but lighter than striated muscles, uninucleated, connected by intercalated discs
Site/Location Found in the limbs, face, tongue, and other parts of the body involved in voluntary movement. Found in the walls of internal organs such as the stomach, intestines, uterus, and blood vessels Exclusively found in the walls of the heart
Control Under conscious or voluntary control Involuntary, meaning they are not under conscious control Involuntary, responsible for the continuous pumping action of the heart

How muscular tissue works

  • Muscle tissue contains contractile proteins that contract and relax to cause movement.
  • Muscle tissue is highly cellular and well supplied with blood vessels.
  • Muscle Fibres can adapt to changing demands by changing size or Fibre type composition.
    Other functions of the muscular system The muscular system also helps maintain posture, blood circulation, and more.

CONNECTIVE TISSUE

Connective tissue is a type of tissue that supports, protects, and binds other tissues and organs in the body. It's made up of cells, Fibres, and a gel-like substance.
Types of connective tissue
  • Bone: A connective tissue that provides structure and support
  • Cartilage: A connective tissue that provides structure and support
  • Blood: A connective tissue that carries oxygen, fights infection, and clots blood
  • Lymphatic tissue: A connective tissue that drains fat and waste materials into the blood
  • Dense connective tissue: A type of connective tissue that supports and protects bones, muscles, and other tissues and organs
  • Areolar Tissue: Areolar connective tissue is found between the skin and muscles, around blood vessels and nerves and in the bone marrow. It fills the space inside the organs, supports internal
  • Adipose Tissue: Adipose tissue, also known as body fat or fatty tissue, is a type of connective tissue that stores energy. It's found throughout the body, including under the skin, between organs, and in bone marrow.
Functions of connective tissue
  • Helps move nutrients and other substances between tissues and organs
  • Helps repair damaged tissue
  • Stores fat
  • Supports, protects, and gives structure to other tissues and organs

BONE

Bone is a specialised connective tissue that provides structure and support to the body. It's made of cells, Fibres, and a mineralised matrix.
Functions of bone
  • Support: Bone provides structure and support to the body.
  • Protection: Bone protects vital organs.
  • Movement: Bone enables movement by providing attachment sites for muscles and tendons.
  • Storage: Bone stores minerals, fat, and blood-forming cells.
  • Energy absorption: Bone's collagen framework absorbs energy.
  • Deformation resistance: Bone's mineral matrix resists deformation.
Bone composition
  • Organic matrix, Similar to other connective tissues, containing collagen and elastic Fibres
  • Inorganic matrix consists of mineral salts, mostly calcium salts, that give bone its hardness
Bone cell types
    Types-of-Bone-Cells
  • Osteogenic Cells: They are undifferentiated and can divide and differentiate into osteoblasts.
  • Osteoblasts: Form bone
  • Osteoclasts: Degrade bone
  • Osteocytes: Live within healthy bone tissue and help osteoblasts and osteoclasts perform their jobs

Bone tissue types
    Bone-Tissue-type
  • Compact tissue (Cortical Bone)
  • Cancellous (Spongy Bone) tissue
  • Subchondral tissue

Cartilage

Cartilage is a flexible, strong, and supportive connective tissue that protects bones and joints. It's less rigid than bone, but more stable than muscle.
How it's made
  • Chondroblasts are cells that produce the extracellular matrix of cartilage.
  • When chondroblasts become trapped in the matrix, they are called chondrocytes.
  • Chondrocytes produce and maintain the cartilage matrix.
  • The number of chondrocytes in cartilage determines how flexible it is.
Types of cartilage
    cartilage
  • Hyaline cartilage: The most common type of cartilage, it's found in the nose, ribs, larynx, and trachea. It's bluish white and glassy in appearance.
  • Elastic cartilage: Also known as yellow cartilage, it provides strength and elasticity.
  • Fibrocartilage: The most rigid type of cartilage, it's made of a mixture of white fibrous tissue and cartilaginous tissue.
Cartilage's functions
  • Protects joints and bones
  • Reduces friction between bones
  • Acts as a shock absorber
  • Provides structural support and protection

Adipose/Fat

adipose-tissue Fat connective tissue, also known as adipose tissue, is a type of loose connective tissue that stores fat and insulates the body. It's made up of fat cells called adipocytes.
Function
  • Energy storage: Adipose tissue stores energy in the form of fat.
  • Insulation: Adipose tissue insulates the body from heat and cold.
  • Cushioning: Adipose tissue cushions internal organs and muscles.
  • Endocrine organ: Adipose tissue produces hormones that communicate with other organs.
Location
  • Subcutaneous fat: Found under the skin
  • Visceral fat: Found between internal organs
  • Bone marrow adipose tissue: Found in the inner cavities of bones
Types of fat cells
  • White adipocytes: The most common type of fat cell in the human body
  • Brown adipocytes: More metabolically active than white adipocytes, and contain more mitochondria
Factors Affecting Fat Distribution
  • Genetics: Genes influence where the body tends to store fat, with approximately 50% of fat distribution is determined by genetic factors.
  • Sex and Hormones: Sex: Men and women naturally have different fat distribution patterns, with men typically accumulating more abdominal fat.
    Estrogen promotes fat storage in the hips and thighs in premenopausal women, while the decrease in estrogen after menopause leads to a shift in fat towards the abdomen, similar to men.
  • Lifestyle and Environment:
    • Diet: The composition and overall intake of your diet regulate fat tissue growth and lipid composition.
    • Alcohol and Smoking: Excessive alcohol intake and cigarette smoking can alter fat distribution.
    • Stress: Psychosocial stress, particularly chronic stress, can activate the hypothalamic-pituitary-adrenal (HPA) axis, leading to increased abdominal fat, insulin resistance, and metabolic complications.

blood-cells

Blood

Blood is a type of connective tissue that connects the body's systems. It's considered a fluid connective tissue because it has a fluid matrix called plasma.
How does blood function?
  • Transports oxygen and nutrients to all parts of the body
  • Removes waste products
  • Forms blood clots to prevent excess blood loss
  • Carries cells and antibodies that fight infection
How is blood made up?
  • Blood is made up of red blood cells, white blood cells, and platelets
  • These cells and cellular constituents are blended into an extracellular matrix, or ground substance, called plasma
Why is blood considered connective tissue?
  • It connects the body's systems
  • It supports, protects, and gives structure to other tissues and organs in the body
  • It helps move nutrients and other substances between tissues and organs
  • It helps repair damaged tissue

lymph-cappilaries

Lymphatic Tissue

Lymphatic connective tissue is a specialised tissue that helps maintain fluid levels, transport substances, and fight infections. It's made of reticular Fibres and contains white blood cells called lymphocytes.
How lymphatic tissue works
  • Fluid balance: Lymphatic tissue returns excess fluid and protein to the bloodstream.
  • Immune response: Lymphatic tissue helps the body recognise antigens and activate lymphocytes.
  • Waste clearance: Lymphatic tissue helps clear waste products like bacteria and proteins.
  • Transport: Lymphatic tissue helps transport substances like fat from the intestines to the bloodstream.
Examples of lymphatic tissue
  • Lymph nodes: Filter lymph fluid and scan for infections. They're located in the neck, armpits, chest, abdomen, and brain.
  • Tonsils: Part of the immune system that protects against pathogens inhaled or ingested.
  • Gut-associated lymphoid tissue (GALT): Scans for microbes ingested into the body.
  • Bronchus-associated lymphoid tissue (BALT): Scans for microbes inhaled into the body.
The lymphatic system is part of the circulatory system.

Fibre-tissue

Dense Connecting Tissue

Dense connective tissue is a type of tissue that provides structural support and is made up of a high concentration of Fibres. It's found in tendons, ligaments, and other parts of the body.
Types of dense connective tissue
  • Dense regular connective tissue Also known as white connective tissue, this tissue is made up of thick collagen fibres. It's found in tendons, ligaments, and aponeuroses.
  • Dense irregular connective tissue This tissue has fibres that aren't arranged in parallel bundles. It has less ground substance than loose connective tissue.
  • Elastic tissue This tissue contains more elastic fibres than collagen. It's found in the wall of the aorta and the elastic ligament of the spine.
Functions of dense connective tissue
  • Structural support: Dense connective tissue provides structural support to the body.
  • Mechanical support: Dense connective tissue provides mechanical support to the body.
  • Tearing resistance: Dense connective tissue is resistant to tearing along its longitudinal axis.
  • Stretching resistance: Dense connective tissue resists stretching forces.
Examples of dense connective tissue tendons, ligaments, organ capsules, nerve sheaths, and the reticular layer of the dermis.

Ligament

skeletal-ligament-tissue a type of dense connective tissue that connects one bone to another bone, essentially holding joints together and providing stability by limiting their range of motion; it is made up primarily of strong collagen Fibres bundled together, allowing for flexibility while maintaining strength.

Tendon

A tendon is the tough, thick band of fibrous tissue that connects muscle to bone. Tendons are made up of collagen Fibres. It functions to transmit the force generated by muscle contraction to bone. Tendons are strong and durable, but also flexible because they can stretch and recoil without rupturing. The extensibility of tendons means that they absorb much of the force generated by muscle contractions, as well as minimise energy consumption during locomotion and other movements.
Ligament vs Tendon
Ligaments Tendons
Connects bones to Connects skeletal muscles to bones
Elastic Tough and elastic
Connects the ends of the bones at joints Connects the end of the muscles to bones
Each joint contains many ligaments Each muscle contains only one tendon.
Proteoglycan content is comparatively more Proteoglycan content is low
Yellow in colour White in colour
Blood supply is just as poor Blood supply is poor
Fibroblasts are scattered Fibroblasts lie in a continuous row
They are not arranged in parallel bundles but are compactly packed The fibres are compact and present in parallel bundles

Areolar Tissue

areolar-tissue Areolar connective tissue is a type of loose connective tissue that connects and supports organs and tissues in the body. It's found in many places, including under the skin, around blood vessels, and in bone marrow.
Structure
  • Areolar tissue is made up of cells, fibres, and a gel-like matrix
  • The cells include fibroblasts, white blood cells, mast cells, macrophages, and fat cells
  • The fibres include collagen, elastin, and reticular fibres
  • The matrix is called ground substance
Function
  • Areolar tissue supports and cushions organs
  • It provides nutrition to cells
  • It helps repair tissues in the skin and muscles
  • It fills spaces inside organs
  • It provides strength, elasticity, and flexibility to body parts
Location
  • Areolar tissue is found beneath the skin
  • It's found around blood vessels and nerves
  • It's found in bone marrow
  • It's found in the lamina propria in many body locations

Nervous Tissue

Nervous Tissue Nervous tissue, also known as neural tissue, is made up of nerve cells and glial cells. It's found in the brain, spinal cord, and nerves. Nervous tissue controls and coordinates many of the body's activities, including movement, memory, and emotions.
Neurons
    Also known as nerve cells, these cells receive and transmit impulses. They have a cell body, dendrites, and an axon.
Glial cells
    Also known as neuroglial cells, these cells support neurons. They bind neurons together, insulate them, and protect them from pathogens.
Function
  • Communication: Neurons communicate with each other and with target cells by releasing chemical signals.
  • Impulse transmission: Neurons transmit impulses to and from the nervous system.
  • Support: Glial cells support neurons by providing nutrients and insulating them.
Nervous system
    The nervous system has two main parts: the central nervous system and the peripheral nervous system.
  • Central nervous system (CNS): Includes the brain and spinal cord.
  • Peripheral nervous system (PNS): Includes the nerves that connect the central nervous system to the rest of the body.
  • Sympathetic nervous system: Prepares the body for physical and mental activity
  • Parasympathetic nervous system: Responsible for bodily functions when you are at rest
Other functions
    The nervous system also controls muscles and glands, maintains homeostasis, and integrates sensory input.

Central Nervous System

The central nervous system (CNS) is the brain and spinal cord that control the body's functions. The CNS is the body's main processing centre. Parts of the CNS
  • Brain:Controls thinking, learning, movement, and feeling. The brain has many folds and grooves that store information
  • Spinal Cord: Carries messages between the brain and the nerves that run throughout the body. The spinal cord is divided into four regions: cervical, thoracic, lumbar, and sacral.
    CNS function
      The CNS sends messages from the brain to the body and back again to regulate thoughts, memory, learning, feelings, movement, and more.

Peripheral Nervous System

    The Peripheral nervous system (PNS) is that part of your nervous system that lies outside your brain and spinal cord. It plays a key role in both sending information from different areas of your body back to your brain, as well as carrying out commands from your brain to various parts of your body.

NERVOUS TISSUE

  • They are highly specialised tissues due to which the animals are able to perceive and respond to the stimuli.
  • Their functional unit is called as never cell or neuron.
  • The Cell body is a cyton covered by a plasma membrane.
  • Short, hair-like extensions starting from cyton are dendrons, which are further subdivided into dendrites.
  • Axon is a long, tail-like, cylindrical process with fine branches at the end. Axon is covered by a sheath.
  • Axon of one neuron is very closely placed to the dendrons of another neuron to carry impulses from one neuron to another neuron in the form of electrochemical waves. This close proximity is called a synapse
Function of Nervous Tissue
    Though all cells possess the ability to respond to a change in environment (stimulus), the Cells of Nervous tissue receives and transmits stimuli very rapidly from sense organs to the brain and spinal cord in the form of impulses. This message is interpreted by the brain and spinal cord, and the message for response is transmitted to the organs. The functional combination of nerve and muscle tissue enables multicellular animals to move rapidly in response to stimuli.

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    Frequently Asked Questions

    Tissues are groups of similar cells that work together to perform a specific function in plants and animals.

    The term 'tissue' was coined by Bichat.

    Plant tissues are of two types: meristematic and permanent tissues.

    These are tissues with actively dividing cells responsible for plant growth.

    Apical, intercalary, and lateral meristem.

    It is found at root and shoot tips and causes increase in length.

    It increases the girth or thickness of stems and roots.

    Permanent tissues are made of mature cells that have lost the ability to divide.

    Simple permanent and complex permanent tissues.

    Tissues made of similar cells performing the same function like parenchyma, collenchyma, sclerenchyma.

    Parenchyma is a living simple permanent tissue that stores food and provides support.

    Collenchyma provides flexibility and mechanical support to the plant.

    Sclerenchyma is a dead supporting tissue with lignified walls providing rigidity and strength.

    Xylem and phloem that help in transport of materials in plant are complex tissues.

    Xylem transports water and minerals from roots to other parts of the plant.

    Tissues – Learning Resources

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