Chapter 7: Axial Skeleton

C2

The second cervical (________) vertebra is called the axis, because it serves as the axis for rotation when turning the head toward the right or left.

nucleus pulposus

Inside is the ________, consisting of a softer, more gel- like material.

braincase bones

As the ________ grow in the fetal skull, they remain separated from each other by large areas of dense connective tissue, each of which is called a fontanelle.

broad U

The ________- shaped curve located between the coronoid and condylar processes is the mandibular notch.

temporal bone

On the interior of the skull, the petrous portion of each ________ forms the prominent, diagonally oriented petrous ridge in the floor of the cranial cavity.

sella turcica

The rounded depression in the floor of the ________ is the hypophyseal (pituitary) fossa, which houses the pea- sized pituitary (hypophyseal) gland.

pedicle

Each ________ forms one of the lateral sides of the vertebral arch.

Optic canal This opening

________ is located at the anterior lateral corner of the sella turcica.

bony ribs

The ________ do not extend anteriorly completely around to the sternum.

**skeleton**

consists of the bones of the body.

**axial skeleton**

forms the vertical, central axis of the body and includes all bones of the head, neck, chest, and back.

**ear ossicles**

(three small bones found in each middle ear).

**appendicular skeleton**

includes all bones of the upper and lower limbs, plus the bones that attach each limb to the axial skeleton.

It is formed by the junction of two bony processes

a short anterior component, the temporal process of the zygomatic bone (the cheekbone) and a longer posterior portion, the zygomatic process of the temporal bone, extending forward from the temporal bone

**cranium**

(skull) is the skeletal structure of the head that supports the face and protects the brain.

**mandible**

lower jaw

**supraorbital margin**

The upper margin of the anterior orbit is the

**supraorbital foramen**

Located near the midpoint of the supraorbital margin is a small opening called the

 **infraorbital foramen**

which is the point of emergence for a sensory nerve that supplies the anterior face below the orbit.

**zygomatic arch**

is the bony arch on the side of skull that spans from the area of the cheek to just above the ear canal.

**temporal fossa**

On the lateral side of the brain case, above the level of the zygomatic arch, is a shallow space called the

**cranial cavity**

The interior space that is almost completely occupied by the brain is called the

**calvaria**

skull cap

**temporal bone**

forms the lower lateral side of the skull.

**External acoustic meatus**

ear canal

**Internal acoustic meatus**

This opening is located inside the cranial cavity, on the medial side of the petrous ridge.

**Mandibular fossa**

This is the deep, oval-shaped depression located on the external base of the skull, just in front of the external acoustic meatus.

**Articular tubercle**

The smooth ridge located immediately anterior to the mandibular fossa.

**Styloid process**

Posterior to the mandibular fossa on the external base of the skull is an elongated, downward bony projection called the styloid process, so named because of its resemblance to a stylus (a pen or writing tool).

**Stylomastoid foramen**

This small opening is located between the styloid process and mastoid process.

**Carotid canal**

The carotid canal is a zig-zag shaped tunnel that provides passage through the base of the skull for one of the major arteries that supplies the brain.

**frontal bone**

is the single bone that forms the forehead

**glabella**

At its anterior midline, between the eyebrows, there is a slight depression called the

**occipital bone**

is the single bone that forms the posterior skull and posterior base of the cranial cavity.

**external occipital protuberance**

which serves as an attachment site for a ligament of the posterior neck.

**foramen magnum**

On the base of the skull, the occipital bone contains the large opening of the **___**, which allows for passage of the spinal cord as it exits the skull.

**occipital condyle**

On either side of the foramen magnum is an oval-shaped

**sphenoid bone**

is a single, complex bone of the central skull.

**sella turcica**

(“Turkish saddle”) is located at the midline of the middle cranial fossa.

**greater wings of the sphenoid bone**

extend laterally to either side away from the sella turcica, where they form the anterior floor of the middle cranial fossa.

**ethmoid bone**

is a single, midline bone that forms the roof and lateral walls of the upper nasal cavity, the upper portion of the nasal septum, and contributes to the medial wall of the orbit.

**crista galli**

(“rooster’s comb or crest”) is a small upward bony projection located at the midline.

**suture**

is an immobile joint between adjacent bones of the skull.

**coronal suture**

runs from side to side across the skull, within the coronal plane of section.

**sagittal suture**

extends posteriorly from the coronal suture, running along the midline at the top of the skull in the sagittal plane of section.

**lambdoid suture**

extends downward and laterally to either side away from its junction with the sagittal suture.

**squamous suture**

is located on the lateral skull.

**maxillary bone**

often referred to simply as the maxilla (plural = maxillae), is one of a pair that together form the upper jaw, much of the hard palate, the medial floor of the orbit, and the lateral base of the nose.

**alveolar process of the maxilla**

The curved, inferior margin of the maxillary bone that forms the upper jaw and contains the upper teeth is the

**palatine process**

On the inferior skull, the **___** from each maxillary bone can be seen joining together at the midline to form the anterior three-quarters of the hard palate.

**hard palate**

is the bony plate that forms the roof of the mouth and floor of the nasal cavity, separating the oral and nasal cavities.

**palatine bone**

is one of a pair of irregularly shaped bones that contribute small areas to the lateral walls of the nasal cavity and the medial wall of each orbit.

**horizontal plate**

The largest region of each of the palatine bone is the

**zygomatic bone**

is also known as the cheekbone.

**nasal bone**

is one of two small bones that articulate (join) with each other to form the bony base (bridge) of the nose.

**lacrimal bone**

Each **__** is a small, rectangular bone that forms the anterior, medial wall of the orbit.

**lacrimal fossa**

The anterior portion of the lacrimal bone forms a shallow depression called the

**ramus of the mandible**

Each side of the mandible consists of a horizontal body and posteriorly, a vertically oriented **__** (ramus = “branch”). 

**angle of the mandible**

The outside margin of the mandible, where the body and ramus come together is called the

**mandibular notch**

The broad U-shaped curve located between the coronoid and condylar processes is the

**Alveolar process of the mandible**

This is the upper border of the mandibular body and serves to anchor the lower teeth.

**Mental protuberance**

The forward projection from the inferior margin of the anterior mandible that forms the chin (mental = “chin”).

**Mental foramen**

The opening located on each side of the anterior-lateral mandible, which is the exit site for a sensory nerve that supplies the chin.

**Mylohyoid line**

This bony ridge extends along the inner aspect of the mandibular body.

**Mandibular foramen**

This opening is located on the medial side of the ramus of the mandible.

**Lingula**

This small flap of bone is named for its shape (lingula = “little tongue”).

**nasal septum**

consists of both bone and cartilage components.

**Optic canal**

This opening is located at the anterior lateral corner of the sella turcica.

**Superior orbital fissure**

This large, irregular opening into the posterior orbit is located on the anterior wall of the middle cranial fossa, lateral to the optic canal and under the projecting margin of the lesser wing of the sphenoid bone.

**Foramen rotundum**

This rounded opening (rotundum = “round”) is located in the floor of the middle cranial fossa, just inferior to the superior orbital fissure.

**Foramen ovale of the middle cranial fossa**

This large, oval-shaped opening in the floor of the middle cranial fossa provides passage for a major sensory nerve to the lateral head, cheek, chin, and lower teeth.

**Foramen spinosum**

This small opening, located posterior-lateral to the foramen ovale, is the entry point for an important artery that supplies the covering layers surrounding the brain.

**Carotid canal**

This is the zig-zag passageway through which a major artery to the brain enters the skull.

**Foramen lacerum**

This irregular opening is located in the base of the skull, immediately inferior to the exit of the carotid canal.

**hypoglossal canal**

Located at the anterior-lateral margin of the foramen magnum is the

**frontal sinus**

is located just above the eyebrows, within the frontal bone.

**maxillary sinus**

The largest sinus is the

**sphenoid sinus**

is a single, midline sinus.

**intervertebral disc**

* It consists of a sequence of vertebrae (singular = vertebra), each of which is separated and united by an

**secondary curve**

develops gradually after birth as the child learns to sit upright, stand, and walk.

**cervical**

The **_ curve** of the neck region develops as the infant begins to hold their head upright when sitting.

**kyphosis**

(an excessive posterior curvature of the thoracic region)

**lordosis**

(an excessive anterior curvature of the lumbar region)

**scoliosis**

(an abnormal, lateral curvature, accompanied by twisting of the vertebral column).

**vertebral arch**

forms the posterior portion of each vertebra.

**pedicle**

forms one of the lateral sides of the vertebral arch.

**lamina**

Each **_** forms part of the posterior roof of the vertebral arch.

**transverse foramen**

Each transverse process also has an opening called the

**Lumbar vertebrae**

carry the greatest amount of body weight and are thus characterized by the large size and thickness of the vertebral body.

**intervertebral disc**

is a fibrocartilaginous pad that fills the gap between adjacent vertebral bodies.

**anulus fibrosus**

is the tough, fibrous outer layer of the disc.

**anterior longitudinal ligament**

runs down the anterior side of the entire vertebral column, uniting the vertebral bodies.

**posterior longitudinal ligament**

is found anterior to the spinal cord, where it is attached to the posterior sides of the vertebral bodies.

**manubrium**

is the wider, superior portion of the sternum.

j**ugular (suprasternal) notch**.

The top of the manubrium has a shallow, U-shaped border called the

**clavicular notch**

is the shallow depression located on either side at the superior-lateral margins of the manubrium.

**xiphoid process**

The inferior tip of the sternum is the

**head of the rib**

The posterior end of a typical rib is called the

**body of the rib**

The remainder of the rib is the **___** (shaft)

**true ribs**

Ribs 1–7 are classified as