the skull Flashcards
(13 cards)
there are two partsof skull
The skull is formed by two sets of bones. The cranium encloses and protects the fragile brain tissue. The facial bones form a cradle for the eyes that is open to the anterior and allow the facial muscles to show our feelings through smiles or frowns. All but one of the bones of the skull are joined together by sutures, which are interlocking, immovable joints. Only the mandible (jawbone) is attached to the rest of the skull by a freely movable joint.
the cranium
The cranium is made up of eight flat bones. Most of these are single bones, except for the parietal and temporal bones, which are paired.
the frontal bone
The frontal bone forms the forehead, the bony projections under the eyebrows, and the superior part of the eye sockets (orbits).
the pariatal bone
The sagittal suture divides the parietal bone into left and right halves, while the coronal suture connects the parietal bones to the frontal bone.
the temporal bone
The temporal bones lie inferior to the parietal bones and join them at the squamous sutures. Several important bone markings appear on the temporal bones
the external acoustic meatus
The external acoustic meatus is a canal that leads to the eardrum and the middle ear. It is the route by which sound enters the ear.
styloid bones
The styloid process, a sharp, needlelike projection, is just inferior to the external auditory meatus. Many neck muscles use the styloid process as an attachment point.
zygomatic
The zygomatic (zi″go-mat′ik) process is a thin bridge of bone that joins with the cheekbone (zygomatic bone) anteriorly.
mastoid bone
The mastoid (mas′toid) process, which is full of air cavities (the mastoid sinuses), is a rough projection posterior and inferior to the external acoustic meatus. It provides an attachment site for some muscles of the neck.
The mastoid sinuses are so close to the middle ear—a high-risk spot for infections—that they may become infected too, a condition called mastoiditis. Also, this area is so close to the brain that mastoiditis may spread to the brain.
the jugular formen
is located between the occipital and temporal bones, and it allows the jugular vein to pass through. This vein drains blood from the brain and carries it back toward the heart.
occipital bones
Occipital Bone – Key Points:
The occipital bone is the back and base of the skull — it’s the most posterior bone of the cranium.
It connects to the parietal bones at the lambdoid suture.
There’s a big hole at the base called the foramen magnum, which allows the spinal cord to connect to the brain.
On either side of the foramen magnum are the occipital condyles — rounded structures that sit on the first vertebra (called the atlas) and allow the head to nod up and down.
shepnoid bone
Shape & Location:
It’s butterfly-shaped and stretches across the width of the skull.
It forms part of the floor of the cranial cavity (the base of the skull where the brain rests).
Important Structures in the Sphenoid:
Sella Turcica (“Turk’s Saddle”)
A small depression in the center of the sphenoid.
It holds the pituitary gland, one of the body’s most important hormone-producing glands.
Foramen Ovale
A large oval opening near the back of the sella turcica.
Allows cranial nerve V (trigeminal nerve) to pass through.
This nerve helps control chewing muscles.
👁️ Eye-Related Structures (visible from the outside near the eye sockets):
Optic Canal
Lets the optic nerve (cranial nerve II) pass from the brain to the eyes.
Superior Orbital Fissure
A slit-like opening near the optic canal.
Transmits cranial nerves III, IV, and VI, which control eye movement.
💨 Sinuses:
Sphenoidal Sinuses
The central part of the sphenoid bone is filled with air cavities called sphenoidal sinuses.
These connect to the nasal passages and help lighten the skull and resonate sound.
