The skull is a bony structure that forms the head in vertebrates. It supports the structures of the face and provides a protective cavity for the brain. The adult human skull is generally made up of 22 bones, excluding the tiny middle ear ossicles. Anatomists divide these bones into two primary groups: the neurocranium, which encloses and shields the brain, and the viscerocranium, which forms the facial skeleton and supports the upper and lower jaws. Aside from protection, the skull houses vital sensory organs for vision, hearing, balance, taste, and smell. In midwifery practice, understanding skull anatomy is crucial because the fetal head is the most common presenting part during childbirth, requiring specific adaptations to navigate the maternal pelvis.
The neurocranium acts as the bony vault surrounding and protecting the brain and the brainstem. It consists of eight bones: one frontal, two parietals, one occipital, two temporals, one sphenoid, and one ethmoid. Some of these bones develop in membrane, while others form via cartilage. The base of the neurocranium is formed by the sphenoid, ethmoid, occipital, and temporal bones, creating a sturdy floor that supports the brain. The roof, known as the calvaria, is formed by the frontal, parietal, and occipital bones. Together, these elements create a rigid enclosure that absorbs mild impacts, though severe trauma can still cause intracranial bleeding or fractures.
The viscerocranium comprises the 14 facial bones that support the eyes, nose, and mouth, while also providing attachment sites for muscles of mastication and facial expression. Unlike the braincase, these bones shape the front and lower portions of the skull.
In an adult, the bones of the skull are firmly joined together by fibrous joints called sutures, such as the sagittal, coronal, and lambdoid sutures. These joints allow virtually no movement. In contrast, the newborn skull features large, membrane-filled spaces between the cranial bones known as fontanelles. These soft spots, notably the diamond-shaped anterior fontanelle and the triangular posterior fontanelle, allow the rigid cranial bones to overlap during birth, a process called molding. Molding protects the brain from excessive pressure during delivery and accommodates the rapid growth of the infant brain after birth. Midwives routinely palpate these fontanelles during labor to determine the position and attitude of the fetal head.
The internal floor of the cranial cavity is divided into three distinct steps known as the cranial fossae, which accommodate the varying contours of the brain. The anterior cranial fossa sits highest, supporting the frontal lobes of the cerebrum. The middle cranial fossa is stepped lower, holding the temporal lobes and housing key structures like the pituitary gland in the sella turcica. The posterior cranial fossa is the largest and deepest, supporting the cerebellum, pons, and medulla oblongata. A clinician examining skull base fractures looks for signs like bruising behind the ears or around the eyes, which often indicate damage to these delicate bony compartments.
The base of the skull is perforated by numerous holes called foramina, which allow cranial nerves, blood vessels, and spinal pathways to enter and exit the cranial vault. For example, the foramen magnum in the occipital bone is the largest opening, allowing the spinal cord to connect with the brainstem. The optic canal transmits the optic nerve from the eye to the brain, while the jugular foramen lets major venous blood and multiple cranial nerves leave the skull. Recognizing these anatomical passageways helps healthcare providers understand how pressure or trauma can affect specific cranial nerves and blood flow.
Midwives and nurses caring for mothers or newborns must remain vigilant for signs of head injury or abnormal intracranial pressure (ICP). In neonates, a bulging fontanelle can indicate increased intracranial pressure, hydrocephalus, or intracranial hemorrhage, whereas a sunken fontanelle often points to dehydration. Following birth trauma or maternal accidents, healthcare workers monitor for neurological changes, unequal pupil response, and altered levels of consciousness. Prompt identification of these clinical red flags ensures timely medical intervention and prevents permanent neurological damage.