chapter 7

Intervertebral discs

(in′-ter-VER-te-bral; inter = between) are found between the bodies of adjacent vertebrae from the second cervical vertebra to the sacrum (Figure 7.15c). Each disc has an outer fibrous ring consisting of fibrocartilage called the annulus fibrosus (annulus = ring or ringlike) and an inner soft, pulpy, highly elastic substance called the nucleus pulposus (pulposus = pulplike). The discs form strong joints, permit various movements of the vertebral column, and absorb vertical shock. Under compression, they flatten and broaden. During the course of a day the discs compress so that we are a bit shorter at night. While we are sleeping there is less compression so that we are taller when we awaken in the morning. As we age, the nucleus pulposus hardens and becomes less elastic. Decrease in vertebral height with age results from bone loss in the vertebral bodies and not a decrease in thickness of the intervertebral discs. -Since intervertebral discs are avascular, the annulus fibrosus and nucleus pulposus rely on blood vessels from the bodies of vertebrae to obtain oxygen and nutrients and remove wastes. Certain stretching exercises, such as yoga, decompress discs and increase blood circulation, both of which increase the uptake of oxygen and nutrients by discs and the removal of wastes from discs.

State the common name of the vertebral column, its functions, and describe the arrangement of the five regions of the adult vertebral column including the number of vertebrae in each region.

7 cervical vertebrae (cervic- = neck) are in the neck region. 12 thoracic vertebrae (thorax = chest) are posterior to the thoracic cavity. 5 lumbar vertebrae (lumb- = loin) support the lower back. 1 sacrum (SĀ-krum = sacred bone) consists of five fused sacral vertebrae. 1 coccyx (KOK-siks = cuckoo, because the shape resembles the bill of a cuckoo bird), consists of four fused coccygeal vertebrae (kok-SIJ-ē-al). Spine

Mastoid proces

: The mastoid process is a rounded projection of the temporal bone posterior to the external auditory meatus. It serves as a point of attachment for several neck muscles.

Procces that form joints

Condyle: large round protuberence at the end of the bone. EX:Lateral condyle of the femur Facet:Smooth flat articular surface Superior: articular facet of a vertebrae. Head:Rounded articular projection supported on the neck (constircited portion) of a bone. EX: head of femur

Processes that form attachemnt points for ocnnective tissue:

Crest: a prominent ridge or elongated portion. :Median secral crest Epicondyle:Projection above a condyle Ex:Median epicondyle of femur Line:Long,narrow ridge or a border (less prominent than a crest) Ex:Linea aspera of femur Spinous process:Sharp,slender projection,Ex:spinous process of vertebrae Trochanter:Very large protection Ex: Great trochanter femur Tuburcle: Small,rounded projection, Ex:Greater tuburcle of the humerous. Tuberosity:Large,rounded,usually roughened projection Ex:Ischial tuberosity of the hip bone

Tempromandibular joint

Each ramus has a posterior condylar process (KON-di-lar) that articulates with the mandibular fossa of the temporal bone (see Figure 7.3 ) to form the temporomandibular joint (TMJ). It also has an anterior coronoid process (KOR-ō-noyd) to which the temporalis muscle attaches (Figure 7.10). The depression between the coronoid and condylar processes is called the mandibular notch. The alveolar process is an arch containing the alveoli (sockets) for the mandibular (lower) teeth.

State the function of skull surface markings

External auditory meatus,Mastoid process:,Styloid process:,Petrous portion,Internal auditory meatus,Foramen magnum,Occipital Condyle,Sella turcica,Optic foramen,Criborifim plate,Crista gilli,Alveolar process

External auditory meatus:

Inferior to the zygomatic process is an external opening in the temporal bone, the external auditory meatus (meatus = passageway), or ear canal, which directs sound waves into the ear (Figure 7.3)

State the functions of the following components of the vertebral column:

Normal curves:Intervertebral discs:Intervertebral foramina:Processes:

Paranasal sinuses:

Paranasal sinuses:he paranasal sinuses (par′-a-NĀ-zal SĪ-nus-ez; para- = beside), mucous membrane-lined cavities near the nasal cavity, are found within the frontal, sphenoid, ethmoid, and maxillary bones (Figure 7.12). The paranasal sinuses are lined with mucous membranes that are continuous with the lining of the nasal cavity. Secretions produced by the mucous membranes of the paranasal sinuses drain into the nasal cavity. The paranasal sinuses lighten the mass of the skull and increase the surface area of the nasal mucosa to help moisten and cleanse inhaled air. In addition, the paranasal sinuses serve as resonating (echo) chambers that intensify and prolong sounds, thereby enhancing the quality of the voice. The influence of the paranasal sinuses on your voice becomes obvious when you have a cold; the passageways through which sound travels into and out of the paranasal sinuses become blocked by excess mucus production, changing the quality of your voice.

Crista galli:

Projecting superiorly from the cribriform plate is a triangular process called the crista galli (crista = crest; galli = cock) (Figures 7.5 and 7.8). This structure serves as a point of attachment for the membranes that separate the two sides of the brain.

Processes

Seven processes arise from the vertebral arch (Figure 7.16). At the point where a lamina and pedicle join, a transverse process extends laterally on each side. A single spinous process projects posteriorly from the junction of the laminae. These three processes serve as points of attachment for muscles. The remaining four processes form joints with other vertebrae above or below. The two superior articular processes of a vertebra articulate (form joints) with the two inferior articular processes of the vertebra immediately above them. In turn, the two inferior articular processes of that vertebra articulate with the two superior articular processes of the vertebra immediately below them. The articulating surfaces of the articular processes are referred to as facets (FAS-ets or fa-SETS = little faces) and are covered with hyaline cartilage.

Sutures

Sutures (SOO-churs = seams), found only between skull bones, hold most skull bones together. Sutures in the skulls of infants and children often are movable, but those in an adult usually form immovable joints. Of the many sutures found in the skull, we will identify only four prominent ones:The coronal suture (kō-RŌ-nal; coron- = crown) unites the frontal bone and both parietal bones (see Figure 7.3The sagittal suture (SAJ-i-tal; sagitt- = arrow) unites the two parietal bones on the superior midline of the skull (see Figure 7.6. The sagittal suture is so named because in the infant, before the bones of the skull are firmly united, the suture and the fontanels (soft spots) associated with it resemble an arrow.The lambdoid suture (LAM-doyd) unites the two parietal bones to the occipital bone. This suture is so named because of its resemblance to the Greek letter lambda (λ)(λ), as can be seen in Figure 7.6(with the help of a little imagination). The sagittal and lambdoid sutures may contain small bones called sutural bones (SOO-chur-al; sutur- = seam).The two squamous sutures (SKWĀ-mus; squam- = flat, like the flat overlapping scales of a snake) unite the parietal and temporal bones on the lateral sides of the skull (see Figure 7.3

Alveolar process

The alveolar process (al-VĒ-ō-lar; alveol- = small cavity) of the maxilla is a ridgelike arch that contains the alveoli (sockets) for the maxillary (upper) teeth (see Figure 7.2

State the function of the costal cartilages.

The costal cartilage are segments of cartilage that connect the sternum to the ribs and help to extend the ribs into a forward motion. This cartilage also contributes to elasticity within the walls of the thorax, allowing the chest to expand during respiration.

Cribriform plate:

The cribriform plate (cribri- = sieve) of the ethmoid bone lies in the anterior cranial floor and forms the roof of the nasal cavity (Figures 7.5 and 7.7a).

Nasal septum

The inside of the nose, called the nasal cavity, is divided into right and left sides by a vertical partition called the nasal septum. The three components of the nasal septum are the vomer, septal cartilage, and perpendicular plate of the ethmoid bone (see The anterior border of the vomer articulates with the septal cartilage, which is hyaline cartilage, to form the anterior portion of the nasal septum. The superior border of the vomer articulates with the perpendicular plate of the ethmoid bone to form the remainder of the nasal septum. The term broken nose, in most cases, refers to damage to the septal cartilage rather than the nasal bones themselves.

Internal auditory meatus:

The internal auditory meatus (see Figures 7.5 and 7.7) is the opening in the petrous portion through which impulses for hearing and equilibrium are carried to the brain.

Mandible

The mandible (mand- = to chew), or lower jawbone, is the largest, strongest facial bone It is the only freely movable skull bone (other than the auditory ossicles, the small bones of the ear). In the lateral view shown in Figure 7.10, you can see that the mandible consists of a curved, horizontal portion, the body, and two perpendicular portions, the rami (RĀ-mī = branches; singular is ramus). The angle of the mandible is the area where each ramus meets the body. Each ramus has a posterior condylar process (KON-di-lar) that articulates with the mandibular fossa of the temporal bone to form the temporomandibular joint (TMJ). It also has an anterior coronoid process (KOR-ō-noyd) to which the temporalis muscle attaches (Figure 7.10). The depression between the coronoid and condylar processes is called the mandibular notch. The alveolar process is an arch containing the alveoli (sockets) for the mandibular (lower) teeth.

Hard Palate

The maxillae form part of the floors of the orbits, part of the lateral walls and floor of the nasal cavity, and most of the hard palate. The hard palate is the bony roof of the mouth and is formed by the palatine processes of the maxillae and horizontal plates of the palatine bones. The hard palate separates the nasal cavity from the oral cavity.

Foramen magnum:

The occipital bone (ok-SIP-i-tal; occipit- = back of head) forms the posterior part and most of the base of the skull (see Figures 7.3, 7.4, and 7.6). The foramen magnum (= large hole) is in the inferior part of the bone (Figure 7.4). Within this foramen, the medulla oblongata (inferior part of the brain) connects with the spinal cord. The vertebral and spinal arteries also pass through this foramen.

Lacrimal(2):

The paired lacrimal bones (LAK-ri-mal; lacrim- = teardrops) roughly resemble a fingernail in size and shape (see Figures 7.2These bones, the smallest bones of the face, are posterior and lateral to the nasal bones and form a part of the medial wall of each orbit. The lacrimal bones each contain a lacrimal fossa, a vertical tunnel formed with the maxilla, through which tears pass into the nasal cavity (see Figures 7.3

Maxialle

The paired maxillae (mak-SIL-ē = jawbones; singular is maxilla) unite to form the upper jawbone. They articulate with every bone of the face except the mandible, or lower jawbone (see Figures 7.2The maxillae form part of the floors of the orbits, part of the lateral walls and floor of the nasal cavity, and most of the hard palate. The hard palate is the bony roof of the mouth and is formed by the palatine processes of the maxillae and horizontal plates of the palatine bones. The hard palate separates the nasal cavity from the oral cavity.(

Sella turcica :

The shape of the sphenoid bone resembles a butterfly with outstretched wings (Figure 7.7b). The body of the sphenoid bone is the hollowed cubelike medial portion between the ethmoid and occipital bones. The space inside the body is the sphenoidal sinus, which drains into the nasal cavity (see Figure 7.12The sella turcica (SEL-a TUR-si-ka; sella = saddle; turcica = Turkish) is a bony saddle-shaped structure on the superior surface of the body of the sphenoid bone (Figure 7.7a). The seat of the saddle is a depression, the hypophyseal fossa (hī-pō-FIZ-ē-al), which contains the pituitary gland.

Explain why the hyoid bone is unique among the bones of the body and how the hyoid bone assists swallowing and speech.

The single hyoid bone (= U-shaped) is a unique component of the axial skeleton because it does not articulate with any other bone Rather, it is suspended from the styloid processes of the temporal bones by ligaments and muscles. Located in the anterior neck between the mandible and larynx (Figure 7.14a), the hyoid bone supports the tongue and provides attachment sites for some tongue muscles and for muscles of the pharynx and larynx. The hyoid bone consists of a body and paired projections called the lesser horns and the greater horns (Figure 7.14b, c). Muscles and ligaments attach to these paired Projections.

the sphenoid bone:

The sphenoid bone (SFĒ-noyd = wedge-shaped) lies at the middle of the base of the skull (Figures 7.4 and 7.7). This bone is the keystone of the cranial floor because it articulates with all of the other cranial bones, holding them together. Viewing the cranial floor from above (see Figure 7.7a), note the sphenoid bone joins anteriorly with the frontal and ethmoid bones, laterally with the parietal and temporal bones, and posteriorly with the occipital bone. It lies posterior and slightly superior to the nasal cavity and forms part of the floor, side walls, and rear wall of the orbit (see Figure 7.11

loctions of just stupid shit

The supraorbital foramen is found on the supraorbital margin of the frontal bone. The optic foramen is in the sphenoid bone. The superior orbital fissure is in the sphenoid bone. The inferior orbital fissure is located between the sphenoid bone, zygomatic bone, and maxilla. The lacrimal fossa is in the lacrimal bone.

Zygomatic Arch

The temporal process of the zygomatic bone projects posteriorly and articulates with the zygomatic process of the temporal bone to form the zygomatic arch (see Figure 7.3

,Palatine(2),:

The two L-shaped palatine bones (PAL-a-tīn) form the posterior portion of the hard palate, part of the floor and lateral wall of the nasal cavity, and a small portion of the floors of the orbits

Inferior nasal conchae

The two inferior nasal conchae are inferior to the middle nasal conchae of the ethmoid bone and are separate bones that are not part of the ethmoid bone These scroll-like bones form a part of the inferior lateral wall of the nasal cavity and project into the nasal cavity. All three pairs of nasal conchae (superior, middle, and inferior) increase the surface area of the nasal cavity and help swirl and filter air before it passes into the lungs.

Zygomat: T

The two zygomatic bones (zygo- = yokelike), commonly called cheekbones, form the prominences of the cheeks and part of the lateral wall and floor of each orbit (see Figures 7.2 . They articulate with the frontal, maxilla, sphenoid, and temporal bones. The temporal process of the zygomatic bone projects posteriorly and articulates with the zygomatic process of the temporal bone to form the zygomatic arch (2)

Zygomatic process:

The two zygomatic bones (zygo- = yokelike), commonly called cheekbones, form the prominences of the cheeks and part of the lateral wall and floor of each orbit (see Figures 7.2 They articulate with the frontal, maxilla, sphenoid, and temporal bones. The temporal process of the zygomatic bone projects posteriorly and articulates with the zygomatic process of the temporal bone to form the zygomatic arch

Vomer(1)

The vomer (VŌ-mer = plowshare) is a roughly triangular bone on the floor of the nasal cavity that articulates superiorly with the perpendicular plate of the ethmoid bone and sphenoid bone and inferiorly with both the maxillae and palatine bones.

Distinguish between the components of the axial skeleton and appendicular skeleton and describe bone surface markings.

There are two principle divison of the skeleton. The axial skeleton and the appendicular skeleton. The axial skeleton consists of the skull bone,auditory ossicles,hyoid bone,ribs,sternum, and bones of the vertebral column. The appendicule skeleton consists of bones of the upper limb,and lower limb,plus forming the girdles that connect the limbs to the axial skeleton. There is 126 boneds in the appendicular skeleton 80 skeleton bones in the appendicular skeleton Fissure narrow slit adjacent pars of the bones through which blood vessels or nerves pass.Ex:Superior orbital fissure of the sphenoid bone Foramen:Opening through the which blood vessels,nerves,or ligaments pass. EX: Optic foramen of the sphenoid bone. Fossa: Shallow depression EX: Coronoid fossa of humans. Sulcus:Furrow along a bone surface that accomadate a blood vessel,nerve or tendon. Ex :interbecular sulcus of humans Meatus:Tube like opening of the meatus: External auditory meatus of the temporal bone

Intervertebral foramina:

Two short, thick processes, the pedicles (PED-i-kuls = little feet), project posteriorly from the vertebral body and then unite with the flat laminae (LAM-i-nē = thin layers) to form the vertebral arch. Together, the vertebral body and the vertebral arch surround the spinal cord by forming the vertebral foramen. The vertebral foramen contains the spinal cord, adipose tissue, areolar connective tissue, and blood vessels. Collectively, the vertebral foramina of all vertebrae form the vertebral canal. When the vertebrae are stacked on top of one another, they form an opening between adjoining vertebrae on both sides of the column. Each opening, called an intervertebral foramen, permits the passage of a single spinal nerve carrying information to and from the spinal cord (

State what organ the vertebral foramina enclose and collectively what they form.

Vertebral foramina:Spinal cord, they form the spinal canals collectively. Protecintg the spinal cord

Normal curves:

When viewed from the side, the adult vertebral column shows four slight bends called normal curves (Figure 7.15b). Relative to the front of the body, the cervical and lumbar curves are convex (bulging anteriorly), and the thoracic and sacral curves are concave (curving posteriorly). The curves of the vertebral column increase its strength, help maintain balance in the upright position, absorb shocks during walking, and help protect the vertebrae from fracture.

Define scoliosis, kyphosis, and lordosis.

a sideways curvature of the spine that occurs most often during the growth spurt just before puberty. While scoliosis can be caused by conditions such as cerebral palsy and muscular dystrophy, the cause of most scoliosis is unknown. excessive outward curvature of the spine, causing hunching of the back. Lordosis in the human spine makes it easier for humans to bring the bulk of their mass over the pelvis. This allows for a much more efficient walking gait than that of other primates, whose inflexible spines cause them to resort to an inefficient forward leaning "bent-knee, bent-w aist" gait.

the ethmoid bone

all of the orbit (see Figure 7.11 and the ethmoid bone: The ethmoid bone (ETH-moyd = like a sieve) is spongelike in appearance and is located in the anterior part of the cranial floor medial to the orbits (Figure 7.8). It is anterior to the sphenoid and posterior to the nasal bones. The ethmoid bone forms (1) part of the anterior cranial floor; (2) the medial wall of the orbits; (3) the superior portions of the nasal septum, which divides the nasal cavity into right and left sides; and (4) most of the superior sidewalls of the nasal cavity.

The paired posterolateral fontanels

are located laterally between the parietal, occipital, and temporal bones. They begin to close 1 to 2 months after birth, but closure is generally not complete until 12 months.

Describe fontanels.

d the mesenchyme-filled spaces between incompletely developed cranial bones are called called fontanels (fon-ta-NELZ = little fountains), or, more commonly, "soft spots" (Figure 7.13). As bone formation continues after birth, the fontanels are eventually replaced with osseous tissue by intramembranous ossification, and the junctions that remain between neighboring bones become the sutures. Functionally, fontanels provide some flexibility to the fetal skull, allowing the skull to change shape as it passes through the birth canal and later permitting rapid growth of the brain during infancy. Although an infant may have many fontanels at birth, the form and location of six are fairly constant:

Orbit

even bones of the skull join to form each orbit (eye socket), which contains the eyeball and associated structures (Figure 7.11). The three cranial bones of the orbit are the frontal, sphenoid, and ethmoid; the four facial bones are the palatine, zygomatic, lacrimal, and maxilla. Associated with each orbit are five openings:

FRONTAL and parietal

he frontal bone forms the forehead (the anterior part of the cranium), the roofs of the orbits (eye sockets), and most of the anterior part of the cranial floor two parietal bones: The two parietal bones (pa-RĪ-e-tal; pariet- = wall) form the greater portion of the sides and roof of the cranial cavity (Figure 7.3). The internal surfaces of the parietal bones contain many protrusions and depressions that accommodate the blood vessels supplying the dura mater, the superficial membrane covering the brain.

the occpital bone:

he occipital bone (ok-SIP-i-tal; occipit- = back of head) forms the posterior part and most of the base of the skull (see Figures 7.3, 7.4, and 7.6). The foramen magnum (= large hole) is in the inferior part of the bone (Figure 7.4). Within this foramen, the medulla oblongata (inferior part of the brain) connects with the spinal cord. The vertebral and spinal arteries also pass through this foramen. The occipital condyles are oval processes with convex surfaces, one on either side of the foramen magnum (Figure 7.4). They articulate with the first cervical vertebra (atlas), which allows you to nod your head "yes." Superior to each occipital condyle on the inferior surface of the skull is the hypoglossal canal (hypo- = under; -glossal = tongue), a passageway for impulses that control movement of the tongue

,two temporal bones:

he paired temporal bones (tempor- = temple) form the inferior lateral sides of the cranium and part of the cranial floor (Figure 7.3). Projecting from the inferior portion of the temporal bone is the zygomatic process, which articulates (forms a joint) with the temporal process of the zygomatic (cheek) bone. Together, the zygomatic process of the temporal bone and the temporal process of the zygomatic bone form the zygomatic arch.

Optic foramen:

he passage through the orbit of the eye in the lesser wing of the sphenoid bone that is traversed by the optic nerve and ophthalmic artery. — called also optic canal. — see chiasmatic groove.

Facial bones

nasal, 1 maxillae, 2 zygomatic, 1 mandible, 2 lacrimal, 2 palatine, (2)inferior nasal conchae, 1 vomer

The unpaired anterior fontanel,

ocated at the midline between the two parietal bones and the frontal bone, is the largest fontanel. It usually closes 18 to 24 months after birth.

The unpaired posterior fontanel is

ocated at the midline between the two parietal bones and the occipital bone. It generally closes about 2 months after birth.

The paired anterolateral fontanels,

ocated laterally between the frontal, parietal, temporal, and sphenoid bones, are small. Normally, they close about 3 months after birth.

Occipital condyle: of the brain)

onnects with the spinal cord. The vertebral and spinal arteries also pass through this foramen. The occipital condyles are oval processes with convex surfaces, one on either side of the foramen magnum (Figure 7.4). They articulate with the first cervical vertebra (atlas), which allows you to nod your head "yes."

Styloid process: he styloid process (styl- = stake or pole)

projects from the inferior surface of the temporal bone and serves as a point of attachment for muscles and ligaments of the tongue and neck (Figures 7.3 and 7.4).

Supraorbital foramen

s found on the supraorbital margin of the frontal bone.

cranial bones

the ethmoid bone:sphenoid bone:the occpital bone:,two temporal bones:two parietal bones:frontal bone;

Petrous portion

vAt the floor of the cranial cavity (see Figure 7.7a) is the petrous portion (petrous = rock) of the temporal bone. The petrous portion is triangular and located at the base of the skull between the sphenoid and occipital bones. The petrous portion houses the internal ear and the middle ear, structures involved in hearing and equilibrium (balance).