Simple Epithelium: Squamous, Cuboidal, Columnar and Ciliated
Biology · Structural Organisation in Animals · NEET
Simple epithelium is a single layer of cells resting on a basement membrane. It has four types by cell shape and surface: squamous (flat, thin — lines blood vessels as endothelium and alveoli), cuboidal (cube-like — ducts of glands and kidney tubules), columnar (tall — inner lining of stomach and intestine) and ciliated (columnar/cuboidal cells with cilia — bronchioles and fallopian tubes). Memory hook: "Shape tells the job" — flat = fast diffusion, tall = absorb/secrete, cilia = move things along.
The four types of simple epithelium drawn on one basement membrane: flat squamous (diffusion), cube-like cuboidal (ducts and PCT), tall columnar (stomach and intestine) and ciliated (cilia that move mucus in bronchioles and the ovum in fallopian tubes).
Your doubts, answered
What makes an epithelium 'simple' and not 'compound'?
Simple epithelium is only ONE cell layer thick, so every cell touches the basement membrane. It is made for absorption, secretion and diffusion. Compound (stratified) epithelium has many layers, so most cells do NOT touch the basement membrane, and its main job is protection. If the question says 'single layer', the answer is always simple epithelium.
Is ciliated epithelium a fourth type, or just columnar with cilia?
Both ideas are correct, and NEET tests this. Ciliated epithelium is columnar OR cuboidal cells that carry cilia on their free surface. The cilia beat to move mucus, particles or the ovum in one direction. So it is listed as a type of simple epithelium, but it is really a normal cuboidal/columnar cell that has grown cilia. Location to remember: bronchioles and fallopian tubes.
Where exactly is squamous epithelium found?
Simple squamous epithelium is flat and very thin, so it is found where fast diffusion or filtration is needed. Key locations: walls of blood vessels (here it is called endothelium), the lining of body cavities (mesothelium), and the walls of alveoli in the lungs. NCERT respiration text even names 'the thin squamous epithelium of alveoli' as part of the diffusion membrane.
Which epithelium lines the stomach and intestine?
Simple columnar epithelium. The cells are tall with the nucleus near the base. This shape gives more room for secretion and absorption, which is exactly what the gut wall needs. Note the trap: the DUCTS of glands are cuboidal, but the inner LINING of stomach and intestine is columnar.
Why does cuboidal epithelium in the kidney have a brush border?
In the proximal convoluted tubule (PCT) of the nephron, the cuboidal cells carry many microvilli called a brush border. The microvilli greatly increase surface area for the heavy reabsorption that happens in the PCT. So 'cuboidal + brush border of microvilli' is a NEET code-word for the PCT of the nephron.
⚠️ The NEET trap ✗ Cuboidal epithelium lines the inner surface of the stomach and intestine. ✓ Columnar epithelium lines the inner surface of the stomach and intestine. Cuboidal epithelium lines the ducts of glands and kidney tubules (and the PCT, with a brush border). 🧠 Ducts and tubules = cuboidal; the food tube lining (stomach/intestine) = columnar. Do not swap them in match-the-column questions.
Real NEET questions
NEET 2023
Match List-I with List-II.
List-I: (A) Columnar epithelium (B) Ciliated epithelium (C) Squamous epithelium (D) Cuboidal epithelium
List-II: (I) Ducts of glands (II) Inner lining of stomach and intestine (III) Inner lining of bronchioles (IV) Endothelium
A · (A)-(II), (B)-(III), (C)-(I), (D)-(IV)
B · (A)-(II), (B)-(III), (C)-(IV), (D)-(I) ✓
C · (A)-(III), (B)-(II), (C)-(I), (D)-(IV)
D · (A)-(III), (B)-(II), (C)-(IV), (D)-(I)
Solution: Columnar lines the stomach/intestine (A-II), ciliated lines the bronchioles (B-III), squamous forms the endothelium of blood vessels (C-IV), and cuboidal lines the ducts of glands (D-I). This gives (A)-(II), (B)-(III), (C)-(IV), (D)-(I).
NEET 2019
The ciliated epithelial cells are required to move particles or mucus in a specific direction. In humans, these cells are mainly present in
A · Bile duct and Bronchioles
B · Fallopian tubes and Pancreatic duct
C · Eustachian tube and Salivary duct
D · Bronchioles and Fallopian tubes ✓
Solution: Motile cilia move mucus and particles in one direction, so ciliated epithelium lines the bronchioles (moves mucus out of the airway) and the fallopian tubes (moves the ovum). Bile, pancreatic and salivary ducts are lined by non-ciliated glandular-duct epithelium, so the answer is Bronchioles and Fallopian tubes.
NEET 2020
Cuboidal epithelium with brush border of microvilli is found in:
A · Proximal convoluted tubule of nephron ✓
B · Eustachian tube
C · Lining of intestine
D · Ducts of salivary glands
Solution: Cuboidal cells with a brush border of microvilli increase surface area for reabsorption, which is the job of the proximal convoluted tubule (PCT) of the nephron. The intestine is lined by columnar epithelium, so the answer is the PCT of the nephron.
Solved Structural Organisation in Animals NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Four: squamous, cuboidal, columnar and ciliated. All are a single cell layer on a basement membrane. Ciliated is columnar or cuboidal cells that carry cilia on their free surface.
What is the function of simple squamous epithelium?
Its flat, thin cells allow fast diffusion and filtration. That is why it forms the endothelium of blood vessels, the lining of body cavities and the walls of alveoli where gases are exchanged.
What is the difference between columnar and ciliated epithelium?
Both have tall cells, but ciliated epithelium has cilia on the free surface to move mucus or particles. Plain columnar (no cilia) lines the stomach and intestine for secretion and absorption; ciliated lines the bronchioles and fallopian tubes.
Which simple epithelium has a brush border?
Cuboidal epithelium in the proximal convoluted tubule of the nephron carries a brush border of microvilli. The microvilli increase surface area for reabsorption.
Why is simple epithelium only one cell thick?
Because its jobs — diffusion, filtration, secretion and absorption — work best over a short distance. A single thin layer lets molecules cross quickly, unlike thick compound epithelium which is built for protection.
