**Core Concept**
The Tanner staging system is a method of classifying the physical development of a child, particularly the development of secondary sex characteristics during puberty. It is primarily used in pediatric and adolescent medicine to assess the growth and development of children.

**Why the Correct Answer is Right**
The Tanner staging system evaluates the development of the genital area, breast tissue, and pubic hair in boys and girls. It consists of five stages, with each stage representing a specific level of physical development. Stage 1 represents prepubertal development, while stages 2-5 represent increasing levels of pubertal development. The system is widely used in clinical practice to assess the normal growth and development of children and to identify any potential abnormalities.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the Tanner staging system is not used for assessing the development of the genital area in newborns. Newborns are typically assessed using the Anatomical Scale for Scoring Erythema (ASSE) or the Neonatal Behavioral Assessment Scale (NBAS).

**Option B:** This option is incorrect because the Tanner staging system is not used for assessing the development of the brain or nervous system in children. The development of the brain and nervous system is typically assessed using other methods, such as magnetic resonance imaging (MRI) or electroencephalography (EEG).

**Option C:** This option is incorrect because the Tanner staging system is not used for assessing the development of the musculoskeletal system in children. The development of the musculoskeletal system is typically assessed using other methods, such as radiographs or ultrasound imaging.

**Option D:** This option is incorrect because the Tanner staging system is not used for assessing the development of the cardiovascular system in children. The development of the cardiovascular system is typically assessed using other methods, such as echocardiography or electrocardiography.

**Clinical Pearl / High-Yield Fact**
The Tanner staging system is an essential tool for pediatricians and adolescent medicine specialists to assess the normal growth and development of children. It is a useful clinical tool for identifying potential abnormalities and for providing guidance on the timing and progression of pubertal development.

**Correct Answer:** C.