Unit 6
Animal Tissues
Chapter 6.1
Introduction; Types of Animal TissuesClass 12 Biology – Introduction; Types of Animal Tissues Notes PDF
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Introduction
Animal tissues are broadly classified into epithelial, connective, muscular and nervous tissues.
1. Epithelial Tissue
Epithelial tissue forms coverings, linings and glands. Its cells are closely packed with little intercellular material and usually rest on a basement membrane.
Main Functions
- Protection
- Absorption
- Secretion
- Excretion
- Diffusion and filtration
- Sensory reception in specialized regions
Fig. 1 – Major Types of Epithelium
2. Connective Tissue
Connective tissue contains cells dispersed in an extracellular matrix. The matrix may be fluid, soft, fibrous or hard depending on the tissue.
Loose Connective Tissue
Includes areolar and adipose tissue; fills spaces, binds structures and stores energy.
Dense Connective Tissue
Contains abundant fibres; forms structures such as tendons and ligaments.
Supporting Connective Tissue
Cartilage and bone provide support, protection and framework.
Fluid Connective Tissue
Blood and lymph transport materials and participate in defence and homeostasis.
Fig. 2 – Areolar Connective Tissue
Fig. 3 – Compact Bone and Cartilage
3. Muscular Tissue
Muscle tissue is specialized for contraction. It contains elongated cells or fibres with contractile proteins.
| Type | Main Features | Location / Role |
|---|---|---|
| Skeletal muscle | Striated, long fibres, multinucleate, voluntary | Attached to bones; body movement |
| Smooth muscle | Non-striated, spindle-shaped, single nucleus, involuntary | Walls of internal organs and blood vessels |
| Cardiac muscle | Striated, branched, involuntary, intercalated discs | Heart wall |
Fig. 4 – Three Types of Muscle Tissue
4. Nervous Tissue
Nervous tissue is specialized for receiving stimuli, processing information and conducting nerve impulses. Its principal functional cell is the neuron, supported by neuroglial cells.
Fig. 5 – Structure of a Neuron
Parts of a Neuron
- Dendrites: receive signals.
- Cell body: contains nucleus and cytoplasm.
- Axon: carries impulses away from the cell body.
- Myelin sheath: insulates many axons and increases conduction speed.
- Axon terminals: transmit signals to another cell across a synapse.
5. Comparison of Major Animal Tissues
| Tissue | Key Feature | Main Function |
|---|---|---|
| Epithelial | Closely packed cells, little matrix | Covering, lining, protection, absorption, secretion |
| Connective | Cells dispersed in matrix | Binding, support, transport, storage |
| Muscular | Contractile fibres | Movement and force generation |
| Nervous | Excitable cells with processes | Communication and coordination |
Fig. 6 – Classification of Animal Tissues
6. Quick Revision & Exam Points
- Define tissue and animal tissue.
- Classify animal tissues.
- Describe types of epithelial tissue.
- Write the functions of connective tissue.
- Differentiate skeletal, smooth and cardiac muscles.
- Draw and label a neuron.
- Compare epithelial, connective, muscular and nervous tissues.
- Epithelial → covering and lining.
- Connective → cells + extracellular matrix.
- Blood = fluid connective tissue.
- Bone/cartilage = supporting connective tissue.
- Skeletal muscle = voluntary + striated.
- Smooth muscle = involuntary + non-striated.
- Cardiac muscle = involuntary + striated + branched.
- Neuron conducts nerve impulses.
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