Bones ossified at birth -a) Lower end of femurb) Calcaneumc) Upper end of tibiad) Upper end of humeruse) Lower end of humerus
**Core Concept**
The question is testing the knowledge of bone development and ossification centers in the human body. Ossification is the process by which cartilage or fibrous tissue is replaced by bone tissue, leading to the formation of a mature bone. In humans, bones ossify at different times during fetal development and growth.
**Why the Correct Answer is Right**
The correct answer involves understanding the timing of ossification centers in the human body. The bones that ossify at birth are those that have already reached a certain level of maturity in the fetus. The lower end of the femur (thigh bone) is one such bone that ossifies in the womb, around 36 weeks of gestation. This early ossification allows the bone to support the growing fetus and facilitate movement. In contrast, other bones, such as the upper end of the tibia (shin bone), ossify later in childhood.
**Why Each Wrong Option is Incorrect**
* **Option A:** The lower end of the femur is indeed one of the bones that ossify at birth, making this option correct. Therefore, we will not discuss it further.
* **Option B:** The calcaneum (heel bone) begins to ossify postnatally, around 2-3 months after birth, making this option incorrect.
* **Option C:** The upper end of the tibia ossifies in late childhood, around 10-15 years of age, making this option incorrect.
* **Option D:** The upper end of the humerus (upper arm bone) begins to ossify around 3-4 months after birth, making this option incorrect.
**Clinical Pearl / High-Yield Fact**
It is essential for medical students to remember that the timing of ossification centers can be crucial in assessing the age of a child or identifying developmental issues.
**Correct Answer: B. Calcaneum**