Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

Musculoskeletal System
Skull
Skull of the Newborn - Age and Sex-Related Features of the Skull

The cranial cavity volume in a newborn infant averages 350–375 cm³. During the first 6 months of life, the cranial volume doubles, and by 2 years of age, it triples. In an adult, it is 4 times larger than the cranial cavity volume of a newborn. The Proportions of the neurocranium and viscerocranium differ between adults and newborns. The newborn's face is short (due to the absence of Teeth) and broad.

After birth, skull growth proceeds unevenly. From birth to 7 years of age, the skull grows rapidly. Throughout the first year of life, skull growth is more or less uniform. From one to three years, the posterior part of the skull grows with particular intensity, which is associated with the transition to bipedal locomotion during the second year of life. During the 2nd and 3rd years, as primary tooth eruption concludes and masticatory Muscle Function increases, the height and width of the facial Skeleton expand significantly. From 3 to 7 years of age, the growth of the entire skull continues, especially its base. By age 7, longitudinal growth of the cranial base is largely complete, reaching a size nearly identical to that of an adult. Between the ages of 7 and 12–13 years, the child's skull grows uniformly and at a slower pace. During this period, growth primarily involves the cranial vault, and the volume of its cavity reaches 1200–1300 cm¹.

After 13 years of age, the frontal region of the neurocranium and the facial skeleton undergo active growth. Obliteration of the cranial sutures begins between the ages of 20 and 30, occurring slightly earlier in men than in women. The sagittal suture closes at 32–35 years of age, the coronal suture at 24–41 years, the lambdoid suture at 26–42 years, and the occipitomastoid suture at 30–81 years. The squamous suture typically does not ossify.

In the elderly and senile, the surface relief of the cranial bones smooths out. The bones become thinner, the spongy substance undergoes partial resorption, and bone elasticity decreases. The skull becomes more fragile and lightweight. This is related to tooth loss and the resorption of dental alveoli, a decline in masticatory function, and partial Atrophy of the masticatory Muscles. Skull Asymmetry is also observed due to the preferential use of masticatory muscles on one side of the HEAD.

In males, the facial skeleton grows more in length than in females. While the faces of both boys and girls are rounded prior to Puberty, after puberty the male face typically becomes elongated, whereas the female face retains its rounded shape. Due to greater overall body size, the male skull is larger than the female skull. The neurocranium is more developed in females, whereas the viscerocranium is more prominent in males. Typically, the male skull features pronounced bony landmarks due to greater muscle attachment development, whereas the female skull surface is smoother.

Review and Self-Assessment Questions:

1. Name the bones that form the neurocranium. Which adjacent bones does each bone articulate with?

2. Name the BONES OF THE viscerocranium. Which adjacent bones does each bone articulate with?

3. What foramina are visible on the external cranial base? What structures pass through these openings (canals)?

4. Describe the cranial fossae (on the internal cranial base), specifying their boundaries and the openings located within them.

5. Name the bones that contribute to The formation of the orbital walls.

6. Name the bones that form the walls of the Nasal cavity. Describe the arrangement of the nasal conchae and nasal meatuses.

7. What movements can the Mandible perform at the temporomandibular joints?

8. Name the fontanelles present in the newborn skull. Which bones bound each fontanelle, and at what age do they close?

9. Describe the age-related transformations of the skull during postnatal ontogeny. What factors influence these age-related changes across different periods of human life?

10. Name the distinguishing Features of the male skull compared to the female skull.