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What Is Tissue

A group of similar cells working together for a specific function.
Different tissues → division of labour → increases efficiency & enables complex life processes.

Why are Plant and Animal Tissues Different?

Why Plant and Animal Tissues Differ

Tissues for Growth in Plants

Types of Meristems

Cell Structure of Meristematic Tissue

➽ Small cells, thin cell walls
➽ Large nucleus, dense cytoplasm
➽ No vacuoles (vacuoles store water/waste; absence allows more space for organelles needed for rapid division)
➽ Tightly packed, no intercellular space ➜ All these features allow continuous & rapid cell division

Differentiation

The process by which meristematic tissue that becomes specialised to perform specific functions is called differentiation.

➽ Some new cells remain meristematic
➽ Others lose the ability to divide ➜ change in structure & function → become permanent tissue
➽ Permanent tissues perform specific functions ➜ support, transport, storage

Meristematic tissue ➜ (differentiation) ➜ Permanent tissue

Permanent Tissues

➽ Formed by the differentiation of meristematic tissue
➽ Each tissue is specialised for a specific function

Types of Permanent tissues

I. Protective Tissues

Epidermis — Protective tissue

➽ Outermost layer of the plant body
➽ Single layer of flat, rectangular, tightly packed cells
➽ Protects against: mechanical injury, water loss, microorganisms, extreme conditions

Cuticle

➽ A waxy layer of cutin covering epidermal cells
➽ Thick cuticle in dry habitat plants ➜ reduces water loss
➽ Also protects against mechanical injury & parasites

Key Structures of Epidermis

Stomata are the pores in leaves that help in gaseous exchange and transpiration

Transpiration (via Stomata)

➽ Evaporation of water vapour through stomata
➽ Creates transpiration pull in xylem ➜ aids water transport
➽ Also helps eliminate waste from the plant body

II. Supporting tissue — Simple permanent tissues

3 types
Parenchyma, Collenchyma, Sclerenchyma

Comparison

Functions of Supporting Tissue

Parenchyma

➽ Stores food
➽ Performs photosynthesis (in green parts)
➽ In aquatic plants ➜ forms air spaces ➜ helps them float

Collenchyma

➽ Provides support & flexibility
➽ Allows bending without breaking (stems, tendrils)

Sclerenchyma

➽ Makes plant parts hard & strong
➽ Found in stems, leaf veins, and seed coats
➽ Examples: coconut husk, walnut shell

Fresh twig bends ➜ collenchyma (flexible) Dry twig breaks ➜ sclerenchyma (rigid/dead cells)

III. Conducting tissues — Complex permanent tissues

Made of different types of cells working together ➜ called complex

Xylem vs Phloem

Key Components of Xylem and Phloem

1. Xylem

➽ Tracheids & vessels ➜ tubular, thick-walled, dead (sclerenchymatous)
➽ Xylem parenchyma ➜ only living component

2. Phloem

➽ Sieve tubes ➜ long, tubular, joined end-to-end with perforated walls ➜ transport food
➽ Companion cells ➜ regulate sieve tube functions; monitor loading/unloading of sugars
➽ Phloem fibres ➜ sclerenchymatous ➜ provide strength

Plant tissues are organised into three tissue systems

Animal Tissues

Groups of similar cells specialised for different functions

1. Epithelial tissues — Structure and functions

➽ Forms the outer covering of the body (skin) & lines the internal organs
➽ Cells are closely packed with very little space
➽ Prevents germ entry, reduces water loss, aids absorption & secretion

Types of Epithelial Tissue

How are various parts connected in our body? – Connective Tissues

2. Connective Tissue
Connects and supports other tissues.
Key feature: matrix (determines consistency)

Blood

Matrix is watery/jelly-like → fluid consistency
Red colour → haemoglobin (iron-rich protein in RBCs)

Types of Connective Tissue

Key distinction:
Blood = fluid matrix ➜ flows Bone = rigid matrix ➜ hard & strong

Can we control movement in our body? – Muscle Tissue

Voluntary movements
Are under our conscious control, such as running, writing or lifting objects

Involuntary movements
Occur automatically without conscious control, for example
the movement of food in the intestine and the beating of the heart

3. Muscle Tissue

Muscle cells = muscle fibres
Responsible for movement in the body

A. Skeletal Muscle

➽ Attached to the skeleton
➽ Controls voluntary movements ➽ (running, writing, lifting)
➽ Cells: long, cylindrical, unbranched
➽ Multinucleate (many nuclei)
➽ Striated (light & dark bands)

B. Smooth Muscle

➽ Found in internal organs (stomach, intestines)
➽ Controls involuntary movements (digestion, food movement)
➽ Cells: spindle-shaped, unbranched
➽ Single nucleus, no striations
Produces slow, continuous movements

C. Cardiac Muscle

➽ Found only in the heart
➽ Involuntary, works throughout life without fatigue
➽ Cells: cylindrical, branched
➽ Single nucleus, faint striations
➽ Contracts rhythmically

How does the body sense, communicate and respond?

4. Nervous Tissue
●The cells of nervous tissue are called neurons
●Forms the body’s control & coordination network
●Specialised to receive, process & transmit messages

Brain

➽ Acts as a control centre
➽ Coordinates activities, memory & responses
➽ Example:
During exercise ➜ brain signals the heart to beat faster for more oxygen

Structure of a Neuron

➽ Cell body
Contains nucleus, controls cell activities

➽ Dendrites
Receive signals from other neurons

➽ Axon
A long fibre that carries messages away from the cell body

➽ Axon terminals
Transmit messages to other cells

Signal flow: Dendrites ➜ Cell body ➜ Axon ➜ Axon terminals ➜ Next cell

● Muscles (voluntary & involuntary) cannot work independently
● They depend on instructions from nervous tissue

The Musculoskeletal System

➽ Made of: bones, muscles, joints, cartilage, tendons & ligaments
➽ Works under the control of the nervous system
➽ Functions:
●Standing upright
●Movement
●Posture
●Protecting organs

How Movement Occurs

Muscle contracts ➜ Tendon transmits force ➜ Bone moves at the joint

➽ Muscles are attached to bones via tendons
➽ Joints = the junction between two or more bones
➽ Joints allow movement, but cannot move bones on their own ➜ muscles do

Body Composition

Types of Joints

A joint = a junction between two or more bones

1. Ball & Socket Joint

➽ The round top of the upper arm fits into the shallow hollow of the shoulder bone
➽ Allows:
● Forward Movement
● Backwards Movement
● Sideways Movement
● Circular Movement

➽ Shoulder + collarbone = shoulder girdle (connects arm to skeleton)
➽ Location: shoulder, hip

2. Hinge Joint

➽ Works like a door hinge ➜ moves in one direction only
➽ The knee has a small kneecap bone that protects the joint
➽ Location: elbow, knee

3. Pivot Joint

➽ Allows side-to-side rotation
➽ Skull connected to the backbone through this joint
➽ Works like a doorknob turning in its socket
➽ Location: neck

4. Fixed Joint

➽ No movement at all
➽ Bones are fused/joined together
➽ Keeps brain, eyes & ears safe even when the body moves
➽ Location: skull bones

Skeletal System

A framework of bones that provides strength & protects internal organs.
Includes:
Skull
Vertebral column
Rib cage.

1. Vertebral Column (Backbone/Spine)

➽ Extends from the base of the skull
➽ Made of small bones called vertebrae
➽ Functions: supports the body, helps stand upright
➽ Between each vertebra ➜ cartilage disc

Cartilage disc

➽ Acts as a cushion
➽ Allows flexibility (bending & twisting)
➽ Protects the spinal cord

2. Rib Cage

➽ 12 pairs of ribs
➽ Protects vital organs ➜ heart & lungs

Structure of the Rib Cage

➽ Ribs are attached to the spine at the back
➽ Ribs are attached to the sternum (breastbone) at the front
➽ Joined by flexible cartilage

Function of the Rib Cage

➽ Cartilage allows the rib cage to expand & contract during breathing
➽ Expansion ➜ air moves into the lungs
➽ Contraction ➜ air moves out of lungs

Injury to ribs ➜ makes breathing painful & difficult

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