Skull

The skull or known as the cranium in the medical world is a bone structure of the head. It supports and protects the face and the brain. The adult skull has a total of 22 individual bones.

They don’t move and united into a single unit. The skull performs vital functions. Mainly, it supports and protects the head’s soft tissues. The baby’s skull is soft but as the bones developed, the bones of the skull form a tough, fibrous membrane and slowly fuse to form a single skull. The mandible is the only bone that separates from other parts of the skull.

What are the Functions of the Skull?

  • It protects the brain.
  • It provides support to the face.

Anterior View of the Skull

It includes the facial bones, which provides the bony support for the eyes and other facial structures. It focuses on the opening of the orbits and the nasal cavity.

  • Orbit –it is a bony socket housing the eyeball and the eye muscles.
  • Supraorbital margin – It is the upper margin of the anterior orbit.
  • Supraorbital – It is near the midpoint of the supraorbital margin.
  • Infraorbital foramen – It is the point of emergence for the sensory nerve. (1)

Lateral View of the Skull

It is primarily consisting of the large and round brain case above and the upper and lower jaws. The areas are separated by the zygomatic arch; the bridge of bone.

  • Zygomatic arch – it is the bony arch on the side of the skull. It starts from the cheek area to the area above the ear canal.
  • Temporal fossa – It is a shallow space in between the side of the braincase and above the zygomatic arch level.
  • Infratemporal fossa – It is an area below the zygomatic arch level and deep to the vertical part of the mandible.

The Cranial Bones

The part of the skull surrounding the brain is called cranium. There are eight cranial bones – frontal bones, occipital bone, ethmoid bone, two parietal bones and temporal bones, and sphenoid bone. Together, they form a bony wall around the brain. There are only several openings for both the blood vessels and nerves.

The occipital bone has foramen magnum; a hole where the spinal cord attaches to the brain through the skull. The ethmoid, frontal, and sphenoid bones have small hollow spaces called paranasal sinuses. The sinuses reduce the weight of the bones. They also play an important role in increasing the resonance of the voice, especially when you sing and hum.

  1. Frontal bone – It is the bone extending from the forehead to the coronal suture. It forms a joint with the parietal bones.
  2. Ethmoid bone – It is the bone inside the eye cavity just behind the bridge of the nose. It is small and rectangular in shape.
  3. Occipital bone – it forms the back of the head. It connects with the occipital condyles and foramen magnum.
  4. Parietal bone – It is the bone at the side of the skull.
  5. Sphenoid bone – it is located just underneath the frontal bone just behind the eye cavities and nose.
  6. Temporal bone – It forms the inside of the sides of the skull. It is where the cheekbone, ear canal, styloid and mastoid process, and the two points of the temporal bone are located. (2)

The cranium has auxiliary bones. They are the following:

  • Cheekbones/zygomatic
  • The roof of the mouth/palatine
  • Vomer/divides the nasal cavity
  • Nasal/the bridge of the nose
  • Lower bones in the nasal cavity/inferior nasal conchae
  • Maxillary/near the nasal bones forming the top area of the jaw

The Facial Bones

The facial bones are still a part of the skull. The facial muscles and organs are supported by 14 bones. They are the mandible, vomer, two maxillae, and zygomatic bones, two lacrimal and palatine bones, two nasal bones, and two nasal conchae. The mandible is the only one out of the 22 skull bones that is movable. (3)

Bone Markings on the Temporal Bones

The temporal bones have three prominent bone markings – external acoustic meatus, styloid process, and mastoid process.

  • External acoustic meatus – It is the opening leading to the organs of the inner ear.
  • Styloid process – It is a thin and pen-like structure where the neck’s muscles and ligaments are attached.
  • Mastoid process – It is a wide and rough projection that serves as the attachment point of the muscles in the neck.

Cranial Sutures

  • Coronal suture – It is the frontal bone’s articulation point with the two parietal bones.
  • Sagittal suture – It is the articulation mark between two parietal bones.
  • Squamous sutures – It is the articulation point between the temporal bone and the parietal bone.
  • Lamboid suture – It is the articulation point between the two parietal bones and occipital bone.

Skull Fractures

A skull fracture pertains to any type of break in the skull. Many of the skull fractures are not as painful as they seem. However, severe fractures of the skull require surgical intervention. Fracture of the skull includes the following:

  • Depressed – This type of fracture makes the part of the skull looks sunken.
  • Basilar –It is characterized by a break in one of the bones near the base of the skull. Such a type of fracture requires immediate medical attention.
  • Linear – A break in the skull bone is noted but the bone has not moved.
  • Diastatic – The fracture takes place along one of the sutures of the skull.

Fun Facts About Skull

  • There are a total of 22 bones in the skull.
  • The skull is not only made up of bones but also cartilages and ligaments.
  • The facial skeleton does not include the teeth and the cartilage of the nose.
  • The skull contains foramina or canals scattered throughout the skull bones.
  • There is only one bone in the skull that is movable and it is the jaw bone or mandible.
  • In a forensic study, you can tell if the skull belongs to male or female. Make skulls are heavier, larger, and thicker than the female skulls. The skull of a female is rounded and less protruded mandible.
  • Every human skull has fractals or sutures of the skull.
  • The bones of the skull are divided into the cranium and facial bones. Cranium has a total of eight bones while the facial bones have a total of 14 bones.
  • The biggest hole in the skull is found in the area of the vertebral column that joins the skull’s base. It is the foramen magnum.
  • An average of 785 pounds is needed to crush a human skull.
  • A skull with crossbones is used as a symbol of poison or death.
  • The shape and size of the skull differ in every ethnic group. (4)

Conclusion

The skull is a vital bone in the body as it houses the brain – one of the delicate organs in the body. It serves as the protection for the brain and the facial skeleton, which is more delicate as it consists mostly of thin-walled bones.

Some are air-filled cavities called paranasal sinuses. The skull has a space called cranial cavity and contains subtle stuff including the brain filled with arterial blood and drain the venous blood. It also contains cerebrospinal fluid and meninges. The skull provides attachment for the muscles of the head.

Basically, the brain and other delicate structures are protected by the skull. Hence, it is important to take good care of the head as once the skull is broken, a person could be in big trouble. There is a possibility that the brain will be damaged and could result in a fatal condition.

References

  1. https://en.wikipedia.org/wiki/Skull
  2. https://teachmeanatomy.info/head/osteology/skull/
  3. https://faculty.washington.edu/chudler/skull.html
  4. https://www.stanfordchildrens.org/en/topic/default?id=anatomy-of-the-newborn-skull-90-P01840