Chapter 7: Axial Skeleton

C2

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.

jugular (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