Which of the following statements is true ?
(a) The adult human skeleton consists of 208 bones.
(b) Vertebrae and facial bones are irregular type of bones.
Answer options :

Question

UnlockIAS · Accepted Answer

Correct — option (2), 'Only (b)'. Only two statements are printed here, so the whole question turns on settling each of them. Statement (a) says the adult human skeleton consists of 208 bones, and that is wrong: the standard count is 206. The figure is worth holding as its two halves, because that is how it is usually tested — the axial skeleton has 80 bones, made up of the skull with 22, the six ear ossicles, the single hyoid, the vertebral column with 26, the sternum and the 24 ribs; the appendicular skeleton has 126, made up of 30 bones in each limb, four in the pectoral girdle and two in the pelvic girdle. Eighty and 126 give 206. A newborn has many more, of the order of three hundred separate elements, and the number falls to 206 in adulthood as bones such as those of the sacrum, the coccyx and the hip bone fuse; that is exactly why the statement specifies the adult skeleton, and why an inflated figure looks superficially reasonable. Statement (b) says vertebrae and facial bones are of the irregular type, and that is right. Bones are classified by shape into long, short, flat, irregular and sesamoid, and the irregular class is the one reserved for bones of complicated shape that fit none of the others — the vertebrae, with their body, arch and several processes, and the bones of the face, are its standard examples. Since statement (a) is false and statement (b) is true, the option that names statement (b) alone is the answer.

Why the other options are wrong — (a) This option accepts both statements, and it fails on the number alone. The adult human skeleton has 206 bones, not 208, and the figure is one of the few in human anatomy that examinations expect to be known exactly. A candidate who chooses this option has usually recognised the truth of the second statement — which is genuinely correct — and then let it carry the first, which is the standard failure in a two-statement question: each statement must be settled on its own before any option is read.  (c) This option keeps the false statement and rejects the true one, so it is wrong twice. The count of 208 is not the accepted figure, and the classification of vertebrae and facial bones as irregular bones is standard: irregular is precisely the category created for bones whose shape is too complex to be called long, short or flat. Anyone selecting this has probably misremembered the total as 208 and then, being confident of it, doubted the shape classification unnecessarily.  (d) Rejecting both statements is right about the first and wrong about the second. Vertebrae and facial bones genuinely are irregular bones, so a blanket rejection cannot stand. This option tempts a candidate who has correctly spotted that 208 is not the right number and then assumes that a question printing one false statement must be printing two — an assumption the format never justifies. An escape option of this kind is only safe when every printed statement has been positively disproved.

Concept: The human skeleton is described in two ways at once, and both are examinable. By division it is axial and appendicular: the axial skeleton, of 80 bones, is the skull with 22 bones, the six ear ossicles, the hyoid, the vertebral column of 26 bones, the sternum and the 24 ribs, and the appendicular skeleton, of 126 bones, is the two limbs with 30 bones each and their girdles, four in the pectoral and two in the pelvic, giving 206 in all in the adult. By shape it is classified into five types: long bones such as the humerus and femur, in which length exceeds breadth and which act as levers; short bones such as the carpals and tarsals, roughly cubical and built for stability; flat bones such as the sternum, the ribs, the scapula and the bones of the cranial vault, which protect underlying organs and provide broad surfaces for muscle attachment; irregular bones such as the vertebrae and the bones of the face, whose complex shape suits them to no other category; and sesamoid bones, which develop within tendons, the patella being the largest. The count of 206 applies only to the adult, because a newborn's skeleton contains a far larger number of separate elements that later fuse — the five sacral vertebrae into the sacrum, the coccygeal into the coccyx, and the ilium, ischium and pubis into a single hip bone on each side.

State PCS 2024 Q64 — Science & Technology PYQ with Answer

State PCS 2024 Q64 — Science & Technology PYQ with Answer