Quick Summary
Animal tissues are groups of similar cells performing a specific function. The four main types — epithelial, connective, muscular, and nervous — form organs and organ systems. Histology (study of tissues) is tested directly in NEET, with questions on types, locations, and special features of each tissue.
Epithelial Tissue
Function: Covering body surfaces, lining cavities, secretion, absorption Features: Cells closely packed, little intercellular matrix, basement membrane below
Types of Epithelium
| Type | Cell Shape | Location | Function |
|---|---|---|---|
| Simple squamous | Flat, scale-like | Bowman's capsule, blood vessels | Diffusion, filtration |
| Simple cuboidal | Cube-shaped | Kidney tubules, salivary glands | Secretion, absorption |
| Simple columnar | Tall, column-like | Small intestine lining | Absorption, secretion |
| Ciliated columnar | Columnar + cilia | Respiratory tract, oviduct | Move mucus/egg |
| Stratified squamous | Multiple layers of flat cells | Skin (keratinised), mouth, oesophagus | Protection |
| Transitional | Can stretch | Urinary bladder, ureter | Allows stretching |
| Glandular | Secretory cells | Glands | Secretion |
Connective Tissue
Function: Binding, supporting, filling spaces between organs Features: Cells scattered in abundant extracellular matrix (fibres + ground substance)
Loose Connective Tissue
Areolar tissue:
- Most common; packing material between organs
- Cells: fibroblasts, mast cells, macrophages, plasma cells
- Fibres: collagen (strength), elastic (flexibility), reticular
Adipose tissue:
- Cells: adipocytes (fat-filled)
- Below skin (hypodermis), around kidneys and heart
- Functions: energy store, insulation, padding
Dense Connective Tissue
- Dense regular: Collagen fibres in parallel rows (tendons — connect muscle to bone; ligaments — connect bone to bone)
- Dense irregular: Fibres in all directions (dermis of skin)
Specialised Connective Tissue
| Type | Matrix | Features | Location |
|---|---|---|---|
| Cartilage | Chondrin (firm, non-vascular) | Chondrocytes in lacunae | Ear, nose, larynx, trachea, joints |
| Bone | Osteoid (hard, calcium + phosphate) | Osteocytes in lacunae; Haversian system | Skeleton |
| Blood | Plasma (fluid matrix) | RBC, WBC, platelets; no fibres | Blood vessels |
| Lymph | Lymph (fluid) | Lymphocytes | Lymph vessels |
Muscular Tissue
Function: Movement and locomotion
| Type | Name | Control | Nuclei | Location | Feature |
|---|---|---|---|---|---|
| Striated | Skeletal muscle | Voluntary | Many (multinucleate) | Attached to skeleton | Alternating dark/light bands |
| Unstriated | Smooth muscle | Involuntary | Single (uninucleate) | Visceral organs (gut, uterus) | No striations |
| Cardiac | Cardiac muscle | Involuntary | Single (uninucleate) | Heart only | Intercalated discs, never fatigues |
Nervous Tissue
Function: Impulse generation and transmission Unit: Neuron (nerve cell)
Structure of a Neuron
- Cell body (soma/cyton): Contains nucleus; Nissl granules (rough ER)
- Dendrites: Short extensions; receive impulses
- Axon: Long extension; transmits impulses away from cell body
- Myelin sheath: Insulating layer (Schwann cells); nodes of Ranvier between segments
- Synapse: Junction between neurons; neurotransmitter released
Types of Neurons
| Type | Direction | Example |
|---|---|---|
| Sensory (afferent) | Receptor → CNS | Smell, pain neurons |
| Motor (efferent) | CNS → effector | Nerve to muscle |
| Interneuron | Within CNS | Brain, spinal cord |
Neuroglia: Supporting cells of nervous tissue (Schwann cells, astrocytes, microglia)
Important Questions
One Mark
- Name the tissue that lines the small intestine.
- What is the matrix of cartilage called?
- Where are intercalated discs found?
- Name the connective tissue cells that store fat.
Short Answer (3 marks)
- Distinguish between striated, unstriated, and cardiac muscle on the basis of three characters.
- What is areolar tissue? Name its cellular components and functions.
- Compare tendons and ligaments.
Long Answer (5 marks)
- Describe the types of epithelial tissue with their location and function.
- Describe the structure of a neuron with a labelled diagram. Name the different types of neurons.
Common Mistakes
- Tendons connect muscle to bone; ligaments connect bone to bone — students often confuse these.
- Cardiac muscle: uninucleate (not multinucleate like skeletal) — has intercalated discs, which are unique.
- Blood is a connective tissue — its matrix is the plasma (liquid), not cells.
- Ciliated epithelium in oviduct moves the egg — students often write "allows egg production" (wrong function).
Board Exam Tips
- Muscle types comparison table (striated, smooth, cardiac — 3–4 characters) is a standard 3-mark question.
- Neuron diagram with labels is a standard 3-mark or 5-mark question.
- Epithelial tissue types (location + function) table is a reliable 5-mark question.
- NEET: Tissue types, their locations, and special features contribute 2–3 questions per paper.
Frequently Asked Questions
Epithelial (covering and lining), Connective (binding and support), Muscular (movement), Nervous (impulse transmission). These arise from the three germ layers: ectoderm, mesoderm, endoderm.