The inner lining of the human small intestine has numerous finger-like projections called :
- A.Sphincter
- B.Villi
- C.Enzymes
- D.Plaques
Correct answer
Explanation
The correct answer is B, Villi. Villi are tiny finger-like folds of the inner lining of the small intestine that greatly increase its surface for absorbing digested food.
Each villus is covered by cells that themselves carry still smaller projections called microvilli, and together they give the small intestine an absorbing surface of many square metres. Inside every villus runs a network of blood capillaries, which take up sugars and amino acids, and a lymph vessel called a lacteal, which takes up fats. The small intestine, about six to seven metres long, is the longest part of the gut and the main site of both digestion and absorption.
Option A is wrong because a sphincter is a ring of muscle that closes an opening, such as the pyloric sphincter between the stomach and the small intestine. Option C is wrong because enzymes are chemicals that break down food, not structures of the lining. Option D is wrong because plaques are deposits, as on teeth or inside arteries.
Exam tip: villi absorb in the small intestine; capillaries take sugars and amino acids, lacteals take fats.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
Show answer
In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Liver cells turn the toxic ammonia released from the breakdown of amino acids into urea through the ornithine cycle, also called the urea cycle.
Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
Show answer
Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
Show answer
They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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