NDA Biology · Human Physiology
Body Tissues — the Building Blocks
A tissue is a group of similar cells doing one job; the body builds every organ from four tissue types — epithelial (covering), connective (support), muscle (movement), and nervous (signalling).
Why this matters
Start here — every organ system later in the chapter is made of these tissues, so the NDA tests them directly (8 PYQs). The connective-tissue family is the highest-yield cluster: blood, cartilage, bone, tendon and ligament are all connective, and the bank loves to swap tendon with ligament or ask where cartilage is NOT found. All EASY or MODERATE — pure recall.
Concept 1 of 4
Levels of organization — cells to organ systems
Intuition
The body is built in a hierarchy. Similar cells group into a tissue; different tissues combine into an organ; organs that share a job form an organ system. Knowing the ladder tells you what KIND of thing each exam term is — 'epithelium' is a tissue, 'stomach' is an organ, 'digestive system' is an organ system.
Definition
The structural hierarchy of the body, smallest to largest:
- Cell — the basic unit of life.
- Tissue — a group of similar cells performing a common function (four types: epithelial, connective, muscle, nervous).
- Organ — different tissues working together (heart, stomach, kidney).
- Organ system — organs sharing one overall job (circulatory, digestive, excretory).
Worked example
Place these in order from smallest to largest unit: stomach, digestive system, muscle tissue, a single gland cell.
Concept 2 of 4
The four types of animal tissue
Intuition
Every tissue in the human body is one of four kinds. Each has a signature job: epithelium covers and lines, connective tissue supports and binds, muscle contracts, and nervous tissue carries signals. Most NDA tissue questions just ask 'which type is this?' — so learn the one-line job of each.
Definition
Four primary animal tissues, classified by function. Note the surprises the bank tests: blood is a connective tissue (fluid matrix), and the contractile proteins actin and myosin are found only in muscle tissue.
| Tissue type | Function | Examples |
|---|---|---|
| Epithelial | Covering and lining of surfaces; protection, absorption, secretion | Skin surface, lining of mouth, oesophagus, intestine, glands |
| Connective | Support, binding, transport; cells in a matrix | Blood, bone, cartilage, tendon, ligament, adipose (fat) Blood is a CONNECTIVE tissue — fluid matrix (plasma) with cells (RBC, WBC, platelets) suspended in it. |
| Muscle | Contraction and movement; contains actin + myosin | Skeletal, smooth, cardiac muscle |
| Nervous | Conducting electrical signals | Neurons (brain, spinal cord, nerves) |
The 'odd one out' answers the bank tests: blood = connective, not a fluid of its own category; contractile proteins = muscle only.
Practice this conceptself-check · 4 quick reps
From the bank · past-year question
Blood is a type of
[Q78 · Sep · 2019]
Blood is connective tissue, not 'a fluid' of its own
A classic distractor lists blood as epithelial, muscular or nervous. It is connective — defined by cells suspended in a non-living matrix, which for blood is the plasma. Bone and cartilage are connective for the same reason.
Concept 3 of 4
The connective-tissue family — tendon, ligament, cartilage, bone
Intuition
Connective tissue is the body's support department, and the NDA mines it for recall questions. Two facts carry most marks: tendon connects MUSCLE to BONE while ligament connects BONE to BONE, and cartilage appears in specific named places (nose, ear, larynx, trachea, knee) but NOT in others. Get the tendon/ligament direction right and the cartilage locations memorised and this cluster is free.
Definition
Members of the connective-tissue family and the facts the bank tests:
- Tendon — connects muscle to bone; made of tightly packed collagen fibres (high tensile strength).
- Ligament — connects bone to bone at a joint; more elastic than tendon.
- Cartilage — flexible support; found in the nose, ear (pinna), larynx, trachea, and joints (knee). NOT in the urinary bladder (smooth muscle) and NOT in the bronchioles (only the larger bronchi have cartilage).
- Bone — rigid calcified connective tissue; the skeleton.
- Blood — fluid connective tissue (plasma + cells).
| Tissue | Connects / role | Key fact |
|---|---|---|
| Tendon | Muscle to bone | Made of collagen; high tensile strength |
| Ligament | Bone to bone | Elastic; holds joints together |
| Cartilage | Flexible support | In nose, ear, larynx, trachea, knee NOT in the urinary bladder or the bronchioles. |
| Bone | Rigid framework | Calcified; the skeleton |
| Blood | Transport | Fluid matrix (plasma) + cells |
Practice this conceptself-check · 4 quick reps
From the bank · past-year question
Which one among the following tissues help to connect two bones ?
[Q53 · Sep · 2024]
Tendon ↔ ligament — the direction is the answer
Tendon = muscle to bone (think: 'Tendon Tugs the muscle'). Ligament = bone to bone. The bank swaps these constantly; if you only remember one, remember tendon = collagen, muscle-to-bone.
'Cartilage is NOT found in ___' — know the exceptions
Cartilage IS in the nose, ear, larynx, trachea and joints. It is NOT in the urinary bladder (2020) or the bronchioles (2024) — the small airways lose their cartilage even though the larger bronchi keep it.
Concept 4 of 4
Epithelium and skin
Intuition
Epithelial tissue covers the body and lines its tubes and cavities. It is named by cell shape — squamous (flat, scale-like), cuboidal (cube), columnar (tall). The skin is the body's largest epithelial organ, and its pigment melanin is a recall favourite: it blocks ultraviolet radiation.
Definition
Epithelial types by cell shape, plus the skin's UV defence:
- Squamous — flat, scale-like cells; line surfaces where smooth flow or thin diffusion is needed (oesophagus, alveoli, blood vessels).
- Cuboidal / Columnar — cube-shaped / tall cells; line glands and the intestine (absorption, secretion).
- Melanin — the brown skin/hair/iris pigment; it absorbs ultraviolet (UV) radiation, protecting cells from UV-induced DNA damage.
| Feature | Detail |
|---|---|
| Squamous epithelium | Flat cells; lines the oesophagus, alveoli, blood vessels |
| Columnar epithelium | Tall cells; lines the intestine and stomach (absorption/secretion) |
| Skin pigment | Melanin — gives colour to skin, hair, iris |
| Melanin's role | Absorbs ultraviolet (UV) radiation — not infrared, X-ray or radio NDA 2017 — melanin protects against ULTRAVIOLET radiation specifically. |
Practice this conceptself-check · 3 quick reps
From the bank · past-year question
Squamous epithelial cells are found in the inner lining of
[Q71 · Apr · 2021]
Melanin blocks UV, not infrared or X-rays
The distractors offer infrared, X-ray and radio radiation. Melanin's job is specifically ultraviolet absorption — the band of sunlight that damages DNA and causes sunburn.
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (3)
The four types of animal tissue4 rows
| Tissue type | Function | Examples |
|---|---|---|
| Epithelial | Covering and lining of surfaces; protection, absorption, secretion | Skin surface, lining of mouth, oesophagus, intestine, glands |
| Connective | Support, binding, transport; cells in a matrix | Blood, bone, cartilage, tendon, ligament, adipose (fat) Blood is a CONNECTIVE tissue — fluid matrix (plasma) with cells (RBC, WBC, platelets) suspended in it. |
| Muscle | Contraction and movement; contains actin + myosin | Skeletal, smooth, cardiac muscle |
| Nervous | Conducting electrical signals | Neurons (brain, spinal cord, nerves) |
The 'odd one out' answers the bank tests: blood = connective, not a fluid of its own category; contractile proteins = muscle only.
The connective-tissue family — tendon, ligament, cartilage, bone5 rows
| Tissue | Connects / role | Key fact |
|---|---|---|
| Tendon | Muscle to bone | Made of collagen; high tensile strength |
| Ligament | Bone to bone | Elastic; holds joints together |
| Cartilage | Flexible support | In nose, ear, larynx, trachea, knee NOT in the urinary bladder or the bronchioles. |
| Bone | Rigid framework | Calcified; the skeleton |
| Blood | Transport | Fluid matrix (plasma) + cells |
Epithelium and skin4 rows
| Feature | Detail |
|---|---|
| Squamous epithelium | Flat cells; lines the oesophagus, alveoli, blood vessels |
| Columnar epithelium | Tall cells; lines the intestine and stomach (absorption/secretion) |
| Skin pigment | Melanin — gives colour to skin, hair, iris |
| Melanin's role | Absorbs ultraviolet (UV) radiation — not infrared, X-ray or radio NDA 2017 — melanin protects against ULTRAVIOLET radiation specifically. |
Watch out for (4)
- Blood is connective tissue, not 'a fluid' of its own→ The four types of animal tissue
- Tendon ↔ ligament — the direction is the answer→ The connective-tissue family — tendon, ligament, cartilage, bone
- 'Cartilage is NOT found in ___' — know the exceptions→ The connective-tissue family — tendon, ligament, cartilage, bone
- Melanin blocks UV, not infrared or X-rays→ Epithelium and skin
Drill every past-year question on this subtopic
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