Download Notes 1

TISSUES
Tissue: - a group or mass of similar cells having common origin, working together to perform certain common functions.
Division of Labour : In simple organisms, all body functions are done by a single cell itself. But in complex organisms, different tasks are carried out
by different organs and organ systems, thus any work is done more efficiently and work load of cells decrease. Tissues are the first step
towards division of labour in complex organisms.
PLANT TISSUES
Plant tissues are of two main types, viz. meristematic tissue and permanent tissue.
1 - Meristematic Tissue:Plant tissues in which cells keep on dividing are called meristematic tissue. Meristematic tissues are present in those parts of plants which keep on
growing. Meristematic tissues are classified on the basis of their location. They are of three
types:
Apical Meristem:- Apical meristem is present on root apex, stem apex, leaf buds and flower
buds. They are responsible for growth in length (height), i.e. primary growth.
Lateral Meristem: Lateral meristem is present along the side of the stem. They are responsible
for growth in girth, i.e. secondary growth. It is of 2 types:
Beneath the bark – cork cambium and
In vascular bundle – vascular cambium.
c. Intercalary Meristem: Intercalary meristem is present at the base of leaf or internodes. They
are present on either side of the node.
PROPERTIES OF MERISTEMS:
Since cells of meristematic tissue are highly active so they have dense cytoplasm. Vacuole is
absent in these cells. These cells have high metabolic activity and rate of respiration. They grow
and divide repeatedly.
Functions: They take part in growth, produce new leaves, stem, flower, fruit etc , heal injuries
and help in making bent shoots upright again.
2 - Permanent Tissue:
Once the cells of meristematic tissue divide to a certain extent, they become specialized for a particular function. This process is called
differentiation. Once differentiation is accomplished, the cells lose their capability to divide and the tissue becomes permanent tissue. These cells
have definite shape and size and have a large central vacuole.
Permanent tissues are of two types: simple permanent tissue and complex permanent tissue.
(a) Simple Permanent Tissue: Simple permanent tissue is composed of similar types of cells. Simple permanent tissues are of three types, viz.
parenchyma, collenchyma and sclerenchyma.
1) Parenchyma: The cells of parenchyma are live and have thin cell wall. They are loosely packed; with lot of
intercellular spaces between them. Parenchyma makes the largest portion of a plant body. Parenchyma
mainly works are packing material in plant parts. The main function of parenchyma is to provide support
and to store food. In some plant parts, parenchyma has chlorophyll as well. In that case, parenchyma carries
out photosynthesis and is then termed as chlorenchyma. In aquatic plants, large air cavities are present in
parenchyma. This provides buoyancy to the plant, such parenchyma is known as aerenchyma.
(2) Collenchyma: Collenchyma cells are live. Its cell wall is thickened at corners. Intercellular spaces are very
few. Collenchymas provides some degree of structural rigidity with
flexibility. Collenchymas is present in leaf stalk; below the epidermis.
Due to this, the leaf stalk can easily bend but does not break.
(3) Sclerenchyma: The cell wall in sclerenchyma is highly thickened and
hard due to deposits of lignin all around. The cells are dead and
intercellular space is absent. Sclerenchyma provides structural rigidity
and strength to plant parts. Bark is composed of sclerenchyma. They
are found around vascular bundles, veins of leaves, hard covering of
seeds and nuts. For example sclerenchyma can be seen in the coconut
husk.
Protective tissue:
EPIDERMIS SIMPLE TISSUE: It covers the entire body of plant. They protect plant from injury, germs and
water loss. Stomata: The epidermis of leaves and soft part of stem has small pores called stomata. A stoma
is a composed of two guard cells which regulate the opening and closing of stoma. Stomata facilitate exchange of gases and transpiration.
In desert plants, epidermis and cutin (a water proof waxy substance secreted by epidermis) are thicker so water loss is further reduced.
CORK SIMPLE TISSUE – These consist of dead cells with no intercellular space. They form the outer layer of old tree trunks. These cells contain
subenin due to which it can’t be penetrated by gases and water. Cork tissue protects plant from injuries, germs and water loss. Cork is light so is
used for making products like bottle stoppers, shuttle cork.
b) Complex Permanent Tissue:
Complex permanent tissue is composed of different types of cells. Complex permanent tissues are of two types, viz. xylem and phloem. Xylem and
phloem together make the vascular bundle in plants.
Xylem: Xylem is composed of trachieds, vessels, xylem parenchyma and xylem fibres (sclerenchyma). The cells of xylem are dead; except the cells of
xylem parenchyma. Vessels are tubular structures and thick walled and provide a channel for conduction of water and minerals from roots to upper
parts of plant.Trachieds are long elongated cells with tapered endings and transport water through pits. Xylem fibre provides structural support to
the tissue. Xylem parenchyma stores food.
Phloem: Phloem is composed of sieve tubes, companion cells, phloem fibre and phloem parenchyma. Sieve tubes are tubular cells with perforated
walls. Sieve cells are elongated with thin cell wall and do not possess nucleus. They are the conducting elements of phloem. Phloem is responsible
for translocation of food in plants from site of photosynthesis to different parts of plant. The transport of food in phloem is a two way movement.
Phloem parenchyma stores food. Phloem fibres have thick cell wall and provide mechanical support to the plant. All type of cells are living except
phloem fibres.
ANIMAL TISSUESThere are 4 major types of tissue
Epithelial
Connective
Muscle
Nervous
1. Epithelial Tissue
General Characteristics:
- Found throughout the body, covers all body surfaces both inside and out e.g. skin, inner lining of mouth, linings of blood vessels, covering of all
organs and cavities.
- Main glandular tissue.
- Attached to underlying connective tissue by non-cellular nonliving basement membrane.
- Usually has no vascular tissue - blood supply
- Cells reproduce rapidly (rapid healing).
- Cells tightly packed together
Functions: Protection, secretion, selectively permeable in case of absorption and excretion, sensory perception.
Six Specific types of epithelial tissue - categorized based on the shape of the cells and the layers of cells.
A. SIMPLE SQUAMOUS - single layer (simple) of very thin, flattened cells (squamous) with round and flat nucleus. Function: Protect the underlying
parts of body from mechanical injury. It prevents the entry of germs inside the body. It facilitates diffusion of gases and filtration. Found in air sacs
of lungs, walls of capillaries, lining of nose, etc.
B. SIMPLE CUBOIDAL – It consists of single layer of cube-shaped cells. Function: They provide mechanical support to organs and help in excretion
and absorption. Found: Lining of kidney tubules, ducts of glands, covering surface of ovaries
C. SIMPLE COLUMNAR – It consists of single layer, elongated cells with their nuclei in about the same position in each cell (usually near the
basement membrane). Free end of the cells consist of finger like projections. Function: They provide mechanical support and protection to organs,
help in secretion of gastric juices, absorption of nutrients.
Found in the inner lining of digestive tract, stomach, intestine and uterus
- contains scattered goblet cells functioning in the secretion of mucus
- some columnar cells (involved in absorption) have tiny finger-like processes called microvilli (increases surface area)
D. STRATIFIED SQUAMOUS - multi-layered, squamous cells. Thicker tissue.
Functions: protection. Found lining body cavities like the mouth and outer layer of skin
E. PSEUDOSTRATIFIED COLUMNAR – It appear "stratified" but really a single layer with nuclei at various levels giving the appearance of layers. They
are usually ciliated (tiny, hair-like projections for sweeping materials along a surface), contains goblet cells.
- Function: secretion and cilia-aided movement
- Location: lining air passages like the trachea and tubes of the reproductive system
F. TRANSITIONAL EPITHELIUM - thick, layered cuboidal cells. "Stretchable" tissue, it also forms barrier to block diffusion. Found: lining of urinary
bladder.
G. GLANDULAR EPITHELIUM – These tissues form multi-cellular glands which produce chemicals. E.g. Exocrine Glands | Endocrine Glands
2. Connective Tissue
General Characteristics:
-Most abundant tissue in your body, found throughout
-Binds structures together
-Provides support, protection, framework, fills space, stores fat, produces blood cells, fights infection
-Composed of more scattered cells with intercellular matrix
-Made up of a ground substance (fluid, semi-solid) and fibers
-Most has a good blood supply
-Cells can reproduce
Three common types of cells:
1. mast cells (prevents blood clots)
2. macrophages (phagocytic) and
3. fibroblasts (most abundant, produce fibers)
Main types of fibers:
. collagenous fibers - thick, made of protein collagen, major structural protein in the body, appear in long parallel bundles. Strong, flexible, but not
very elastic, also known as white fibers. (bones, ligaments, tendons)
. elastic fibers - microfibrils in protein elastin, yellow fibers. Not as strong, but very elastic (respiratory and vocal cords)
CATEGORIES OF CONNECTIVE TISSUE
A. LOOSE C.T. or AREOLAR TISSUE – It consists of cells and fibres in matrix. It binds skin to underlying organs
and organs to organs. It is found in between skin and underlying muscles, space between muscles, around
blood vessels, around nerves and bone marrow throughout the body.
B. ADIPOSE TISSUE - aka FAT, beneath skin, around internal organs like kidneys and eyeballs, abdominal
membranes, etc. Function: Protective cushion for internal organs, insulation to preserve body heat and stores
energy. These cells are called adipocytes.
C. FIBROUS C.T. - dense tissue, closely packed, thick collagenous fibers and fine network of elastic fibers. Few cells, poor blood supply, thus slow
healing.
Tendons – It is made up of white fibres. They connect muscles to bones.
Ligaments – It is made up of white and yellow fibres. It connects bones to bones. It is more flexible compared to tendon.
D. SKELETAL CONNECTIVE TISSUE
i. CARTILAGE (all cartilage cells are called chondrocytes). They are soft tissue that smoothens the bone
joints. They have wide spread cells in solid matrix of proteins and sugars. They do not have blood vessels.
They are of 3 types:
. HYALINE CARTILAGE – It has very fine white (collagen) fibers. It is the most common cartilage. It covers
the ends of bones and joints, respiratory passages.
. ELASTIC CARTILAGE - more flexible and elastic, external ear and larynx
. FIBROCARTILAGE – It is very tough, with large numerous collagenous fibers. Intervertebral disks, menisci
ii. BONE TISSUE – Cells are embedded in matrix of calcium and phosphate compounds. Bones form
framework of the body. They facilitate movement of muscles. Bones are hard and inflexible due to
mineral salts. They have blood vessels.
Layers - lamellae, haversian canals, osteocytes
E. FLUID CONNECTIVE TISSUE
i. BLOOD - It is a fluid connective tissue composed of blood cells, platelets and plasma. It circulates throughout the body and transports various
materials like gases, digested food, waste material and hormones. Blood plasma contains 2 types of blood cells: RBCs and WBCs.
ii. LYMPH – It is a whitish fluid obtained from blood itself. It contains blood plasma, WBCs, platelets but no RBCs. Lymph transports food materials,
waste materials and gases which blood cannot transfer.
3. Muscle Tissue
It is composed of elongated cells called muscle fibres. This tissue allows movement in body by contraction and relaxation. Muscle tissue is of 3
types:
A. Skeletal (voluntary or striated): The cells are in the form of long, unbranched fibres. They have multi nucleus. Striations are present on muscle
fibres. These are found in organs where voluntary movement is possible, e.g. hands, legs, etc.
B. Smooth (involuntary): These cells are spindle shaped having one nucleus. Smooth muscles are found in those organs where involuntary
movement occurs, e.g. muscles of stomach.
C. Cardiac – These cells are in the form of branched fibres. These are found in the walls of the heart. Cardiac muscles have many nucleus and
striations are present. Cardiac muscles can move continuously throughout the life in rhythmic pattern.
4. Nervous Tissue – It is composed of specialized cells called neurons.A Neuron consists of a cell body (cyton) with a nucleus and cytoplasm from
which numerous hair like structures arise called dendrites. One long extension is called Axon. Neurons are connected end to end to form nerves.
Nervous tissue is found in brain, spinal cord and nerves. Neuroglia is the tissue that surrounds and supports neurons for protection.
Functions: a) They give us ability to respond to stimuli.
b) They transmit information from body parts to brain.
c) They transmit orders from brain to body parts.
d) Nervous and muscular tissue together control body movement in all animals.