Tortora Chapter 7 - Axial Skeleton Structures
Tortora Chapter 7 - Axial Skeleton Structures LS-ANATO 219
Popular in Functional Anatomy I
Popular in LS-ANAT
This 42 page Class Notes was uploaded by Taylor Swifty on Saturday September 17, 2016. The Class Notes belongs to LS-ANATO 219 at University of Missouri - Kansas City taught by Tara Allen in Fall 2016. Since its upload, it has received 9 views. For similar materials see Functional Anatomy I in LS-ANAT at University of Missouri - Kansas City.
Reviews for Tortora Chapter 7 - Axial Skeleton Structures
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 09/17/16
CONTENTS AT A GLANCE 7.1 Divisions of the Skeletal System 165 • Age-related Changes in the Skull 192 7.2 Skull 167 • Sexual Differences in the Skull 193 • General Features and Functions 167 7.3 HyoidBone 194 • Exhibit7.A Cranial Bones—Frontal Bone 168 7.4 VertebralColumn 195 • Exhibit7.B Cranial Bones—Parietal Bones 170 • Normal Curves of the Vertebral Column 195 • Exhibit7.C Cranial Bones—Temporal Bones 172 • IntervertebralDiscs 195 • Exhibit7.D Cranial Bones—Occipital Bone 174 • Parts of a Typical Vertebra 197 • Exhibit7.E Cranial Bones—Sphenoid Bone 176 • Regions of the Vertebral Column 199 • Exhibit7.F Cranial Bones—Ethmoid Bone 180 • Age-related Changes in the Vertebral Column 199 • Exhibit7.G Facial Bones—Nasal, Lacrimal, Palatine, • Exhibit7.J Vertebral Regions—Cervical Vertebrae 200 Inferior Nasal Conchae, and Vomer 182 • Exhibit7.H Facial Bones—Maxillae and Zygomatic • Exhibit7.K Vertebral Regions—Thoracic Vertebrae 202 • Exhibit7.L Vertebral Regions—Lumbar Vertebrae 204 Bones 184 • Exhibit7.M Vertebral Regions—Sacral and Coccygeal • Exhibit7.I FaciaBlones—Mandible 185 Vertebrae 206 • NasalSeptum 186 • Orbits 186 7.5 Thorax 208 • Exhibit7.N ThoracicBones—Sternum 208 • Foramina 188 • Exhibit7.O ThoracicBones—Ribs 210 • Unique Features of the Skull 188 • CranialFossae 192 Key Medical Terms Associated with the Axial Skeleton 212 7.1 DIVISIONS of the body and the other on the left. The skeletons of infants and children have more than 206 bones because some of their OF THE SKELETAL SYSTEM bones fuse later in life. Examples are the hip bones and some bones (such as the sacrum and coccyx) of the vertebral column OBJECTIVE (also known as the backbone). • Describe how the skeleton is organized into axial and Bones of the adult skeleton are grouped into two principal appendicular divisions. divisions: the axial skeleton and the appendicular skeleton The adult human skeleton consists of 206 named bones; most of (appendic-⫽to hang onto). Table 7.1 presents the 80 bones of them are paired, with one member of each pair on the right side the axial skeleton and the 126 bones of the appendicular skeleton. TABLE 7.1 The Bones of the Adult Skeletal System DIVISION OF NUMBER DIVISION OF NUMBER THE SKELETON STRUCTURE OF BONES THE SKELETON STRUCTURE OF BONES Appendicular Upper limbs Axial skeleton Skull skeleton Pectoral (shoulder) girdles Cranium 8 Clavicle 2 Face 14 Scapula 2 Hyoid bone 1 Free upper limbs Auditory ossicles 6 Humerus 2 Vertebral column 26 Ulna 2 Thorax Radius 2 Sternum 1 Carpals 16 Ribs 24 Metacarpals 10 Number of bones ⫽ 80 Phalanges 28 Lower limb Pelvic (hip) girdle Hip, pelvic, or coxal bone 2 Free lower limbs Femur 2 Patella 2 Fibula 2 Tibia 2 Tarsals 14 Metatarsals 10 Phalanges 28 Number of bones ⫽ 126 Total in adult skeleton ⫽ 206 165 166 CHAPTER 7 • THE SKELETAL SYSTEM: THE AXIAL SKELETON Figure 7.1 Divisions of the skeletal system. The axial skeleton is indicated in blue. Note the position of the hyoid bone in Figure 7.4a. The adult human skeleton consists of 206 bones grouped into two divisions: the axial skeleton and the appendicular skeleton. SKULL Cranial portion Facial portion PECTORAL (SHOULDER) GIRDLE Clavicle Scapula THORAX Sternum Ribs FREE UPPER LIMB Humerus VERTEBRAL VERTEBRAL COLUMN COLUMN PELVIC PELVIC (HIP) (HIP) GIRDLE GIRDLE Ulna Radius Carpals Metacarpals Phalanges FREE LOWER LIMB Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges (b) Posterior view (a) Anterior view Which of the following structures are part of the axial skeleton, and which are part of the appendicular skeleton? Skull, clavicle, vertebral column, shoulder girdle, humerus, pelvic girdle, and femur. 7.2 SKULL 167 Both divisions join to form the complete skeleton shown in sphenoid bone, and the ethmoid bone. Fourteen facial bones Figure 7.1 (the bones of the axial skeleton are shown in blue). form the face: two nasal bones, two maxillae (or maxillas), two You can remember the names of the divisions if you think of zygomatic bones, the mandible, two lacrimal bones, two palatine the axial skeleton as consisting of the bones that lie around the bones, two inferior nasal conchae, and the vomer. Figures 7.2 longitudinal axis of the human body, an imaginary vertical line through 7.10 in Exhibits 7.A through 7.I illustrate the bones of that runs through the body’s center of gravity from the head to the skull from different views. the space between the feet: skull bones, auditory ossicles (ear bones), hyoid bone (see Figure 7.4a), ribs, sternum (breastbone), General Features and Functions and bones of the vertebral column. The appendicular skeleton consists of the bones of the upper and lower limbs, or append- In addition to forming the large cranial cavity that houses the ages. The limbs are made up of bones that form the limb girdles brain, the skull also forms several smaller cavities, including the and bones that form the free limbs. nasal cavity and orbits (eye sockets), which open to the exterior. We will organize our study of the skeletal system around the Certain skull bones also contain cavities called paranasal sinuses two divisions of the skeleton, with emphasis on how the many that are lined with mucous membranes and open into the nasal bones of the body are interrelated. In this chapter we focus on the cavity. Also within the skull are small middle and inner ear cavities axial skeleton, looking first at the skull and then at the bones of in the temporal bones that house the structures that are involved the vertebral column and the chest. We then take a closer look at in hearing and equilibrium (balance). the appendicular skeleton in Chapter 8. The auditory ossicles, occipital bone, and mandible are the only bones of the skull that are movable. Most of the skull CHECKPOINT bones are held together by sutures, joints that attach the bones 1. On what basis is the skeleton grouped into axial and and that are especially noticeable on the outer surface of the appendicular divisions? skull (see Figure 7.3). The skull has numerous openings through which blood vessels and nerves pass. You will learn the names of important surface markings as the various bones are described. 7.2 SKULL The cranial bones have other functions in addition to protect- ing the brain. Their inner surfaces attach to membranes (me- OBJECTIVES • Name the cranial bones and facial bones and indicate the ninges) that stabilize the positions of the brain, blood vessels, and nerves. The outer surfaces of cranial bones provide large number of each. areas of attachment for muscles that move various parts of the • Describe the following unique features of the skull: sutures, paranasal sinuses, and fontanels. head. The bones also provide attachment for some muscles that are involved in producing facial expressions. Besides forming the • Outline the age-related changes and sexual differences in the skull. framework of the face, the facial bones protect and provide sup- port for the entrances to the digestive and respiratory systems. The skull is the bony framework of the head and contains 22 Together, the cranial and facial bones protect and support the bones, not counting the bones of the middle ears. It rests on the delicate special sense organs for vision, taste, smell, hearing, and superior end of the vertebral column and includes two sets of equilibrium. The auditory ossicles of the middle ear help amplify bones: cranial bones and facial bones (Table 7.2). The cranial sound waves to make hearing possible. The inner ear contains bones (crani-⫽skull) form the cranial cavity, which encloses and sensory structures important for hearing and others that monitor protects the brain. The eight cranial bones are the frontal bone, the position and movement of the head, factors important in the two parietal bones, two temporal bones, the occipital bone, the sense of balance. TABLE 7.2 Summary of Bones of the Adult Skull CRANIAL BONES FACIAL BONES Frontal (1) Nasal (2) Parietal (2) Maxillae (2) Temporal (2) Zygomatic (2) Occipital (1) Mandible (1) Sphenoid (1) Lacrimal (2) Ethmoid (1) Palatine (2) Inferior nasal conchae (2) Vomer (1) The numbers in parentheses indicate how many of each bone are present. The small bones of the middle ear are not included in this summary. 168 CHAPTER 7 • THE SKELETAL SYSTEM: THE AXIAL SKELETON EXHIBIT 7.A Cranial Bones—Frontal Bone (Figure 7.2) suture (its joint with the paired parietal bones) on top of the skull OBJECTIVE • Identify the location and surface features of the frontal (see Figure 7.3b), then angles abruptly and becomes almost verti- cal above the orbits. At the superior border of the orbits the fron- bone. tal bone thickens, forming the supraorbital margin (supra-⫽above; orbital⫽circular). From this margin the frontal bone extends pos- Description teriorly as a horizontal plate of bone to form the roof of the orbit The frontal bone forms the forehead (the anterior part of the and part of the floor of the cranial cavity. Within the supraorbital cranium), the roofs of the orbits (eye sockets), and most of the margin, slightly medial to its midpoint, is a hole called the su- anterior part of the cranial floor (Figure 7.2). In most individuals praorbital foramen through which the supraorbital nerve and ar- it is an unpaired bone. Soon after birth the left and right sides of tery pass. Sometimes this foramen is incomplete and is called the the frontal bone are united by a suture called the metopic suture supraorbital notch. Near the midline, within the vertical portion of (me-TO-pik; metophoron⫽forehead), which usually disappears the frontal squama, the bone is hollow. These hollow spaces are between the ages of 6 and 8. the paranasal sinuses called the frontal sinuses. Paranasal sinuses, mucous membrane–lined cavities within certain skull bones, will Surface Features be discussed later in the chapter. If you examine the anterior view of the skull in Figure 7.2, you will note the frontal squama, a thick, scalelike plate of bone that CHECKPOINT forms the forehead. It gradually slopes inferiorly from the coronal 2. What structures pass through the supraorbital foramen? Figure 7.2 Anterior view of the skull. The skull consists of cranial bones and facial bones. FRONTAL BONE Frontal squama Coronal suture Supraorbital foramen PARIETAL BONE Supraorbital notch Supraorbital margin Squamous suture Optic foramen (canal) Superior orbital fissure Orbit TEMPORAL BONE ETHMOID BONE SPHENOID BONE NASAL BONE PALATINE BONE Inferior orbital fissure LACRIMAL BONE Middle nasal concha Zygomaticofacial Infraorbital foramen foramen ZYGOMATIC BONE MAXILLA Perpendicular plate of ethmoid bone Alveolar process INFERIOR NASAL of maxilla CONCHA VOMER Alveolar process of mandible Mental foramen MANDIBLE (a) Anterior view EXHIBIT 7.A 169 FRONTAL BONE Frontal squama Supraorbital foramen PARIETAL BONE Supraorbital margin Optic foramen Superior orbital fissure Supraorbital notch TEMPORAL BONE SPHENOID BONE Orbit ETHMOID BONE ZYGOMATIC BONE LACRIMAL BONE Inferior orbital fissure Perpendicular plate of ethmoid bone Middle nasal concha VOMER Infraorbital foramen INFERIOR NASAL CONCHA MAXILLA Alveolar process of maxilla Alveolar process of mandible MANDIBLE Mental foramen (b) Anterior view PARIETAL BONE FRONTAL BONE LACRIMAL BONE OCCIPITAL BONE NASAL BONE SPHENOID BONE TEMPORAL BONE ETHMOID BONE PALATINE BONE VOMER ZYGOMATIC BONE INFERIOR NASAL CONCHAE BONE MAXILLA MANDIBLE (c) Anterior view of disarticulated skull Which of the bones shown here are cranial bones? 170 CHAPTER 7 • THE SKELETAL SYSTEM: THE AXIAL SKELETON EXHIBIT 7.B Cranial Bones—Parietal Bones (Figure 7.3) OBJECTIVE Surface Features • Identify the location and surface features of the parietal The external surface of each of these bones is slightly convex bones. (curved outward, like the outside of a sphere), while the inter- nal surface is concave. The internal surfaces of the parietal bones Description contain many protrusions and depressions that accommodate the The two parietal bones (pa-RI -e-tal; pariet-⫽wall) are large, blood vessels supplying the dura mater, the superficial membrane quadrilateral (four-sided) bones that form the greater portion (meninx) covering the brain. of the sides and roof of the cranial cavity (Figure 7.3). Each bone articulates with five other bones. The inferior border forms a beveled articular surface, while the anterior, poste- rior, and superior borders form deeply denticulate (toothlike) CHECKPOINT articular surfaces. 3. How do the parietal bones relate to the cranial cavity? Figure 7.3 Superior and right lateral view of the skull. The zygomatic arch is formed by the zygomatic process of the temporal bone and the temporal process of the zygomatic bone. View Zygomatic bone Frontal bone Temporal bone Coronal suture Sagittal suture PARIETAL BONES Parietal foramina Lambdoid suture Sutural bone Occipital bone (a) Superior view (b) Superior view EXHIBIT 7.B 171 Zygomatic arch Coronal suture FRONTAL BONE PARIETAL BONE SPHENOID BONE ZYGOMATIC BONE Temporal squama ETHMOID BONE LACRIMAL BONE Squamous suture Lacrimal fossa TEMPORAL BONE Zygomatic process NASAL BONE Lambdoid suture Temporal process Mastoid portion Mandibular fossa OCCIPITAL BONE MAXILLA External occipital Articular tubercle protuberance External auditory meatus Mastoid process MANDIBLE Styloid process Occipital condyle (c) Right lateral view Coronal suture Zygomatic arch PARIETAL BONE Squamous suture FRONTAL BONE Temporal squama TEMPORAL BONE SPHENOID BONE NASAL BONE Lambdoid suture Zygomatic process Mastoid portion Temporal process OCCIPITAL BONE ZYGOMATIC BONE Articular tubercle External occipital protuberance MAXILLA External auditory Mandibular fossa meatus Mastoid process Styloid process Mental foramen MANDIBLE (d) Right lateral view What are the major bones on either side of the squamous suture, the lambdoid suture, and the coronal suture? 172 CHAPTER 7 • THE SKELETAL SYSTEM: THE AXIAL SKELETON EXHIBIT 7.C Cranial Bones—Temporal Bones (Figure 7.4) inferior portion of the temporal squama is the zygomatic process, OBJECTIVE • Identify the location and surface features of the temporal which articulates (forms a joint) with the temporal process of the zygomatic (cheek) bone. Together, the zygomatic process of the bones. temporal bone and the temporal process of the zygomatic bone form the zygomatic arch. You can easily palpate this horizontal Description arch of bone immediately anterior to the ear. The two temporal bones ( tempor-⫽temple) form the inferior On the inferoposterior surface of the zygomatic process of the lateral aspects of the cranium and part of the cranial floor. The temporal bone is a socket called the mandibular fossa. Anterior to terms temporal and temple are derived from the Latin word tempus, the mandibular fossa is a rounded elevation, the articular tubercle meaning “time,” in reference to the graying of hair in the temple (see Figure 7.3c, d). The mandibular fossa and articular tubercle area, a sign of time’s passing. articulate with the mandible (lower jawbone) to form the tempo- romandibular joint (TMJ). The mastoid portion ( mastoid⫽breast-shaped) (see Figure Surface Features 7.3c, d) is located posterior and inferior to the external auditory In the lateral view of the skull (see Figure 7.3c, d), note the tem- meatus (meatus⫽passageway), or ear canal, which directs sound poral squama, the thin, flat portion of the temporal bone that waves into the ear. In the adult, this portion of the bone con- forms the anterior and superior part of the temple (the region tains several mastoid air cells that communicate with the hollow of the cranium around the ear). Projecting anteriorly from the space of the middle ear (tympanic cavity). These tiny air-filled Figure 7.4 Medial view of sagittal section of the skull. Although the hyoid bone is not part of the skull, it is included in the illustration for reference. The cranial bones are the frontal, parietal, temporal, occipital, sphenoid, and ethmoid bones. The facial bones are the nasal bone, maxillae, zygomatic bones, lacrimal bones, palatine bones, mandible, and vomer. Coronal suture FRONTAL BONE Sagittal Sella turcica: plane Dorsum sellae Tuberculum sellae Hypophyseal fossa View Frontal sinus ETHMOID BONE: Crista galli Cribriform plate PARIETAL BONE Temporal squama Perpendicular Squamous suture plate Lambdoid suture NASAL BONE TEMPORAL BONE Internal auditory Sphenoidal sinus meatus SPHENOID BONE External occipital protuberance INFERIOR NASAL Mastoid portion CONCHA OCCIPITAL BONE VOMER Hypoglossal canal MAXILLA PALATINE BONE Occipital condyle Styloid process Pterygoid processes MANDIBLE Mandibular foramen HYOID BONE (a) Medial view of sagittal section EXHIBIT 7.C 173 compartments are separated from the brain by thin bony parti- At the floor of the cranial cavity (see Figure 7.6a, b) is the tions. Middle ear infections that go untreated can spread into petrous portion ( petrous⫽rock) of the temporal bone. This por- the mastoid air cells, causing a painful inflammation referred to tion is pyramidal (having the shape of a pyramid) and located as mastoiditis (mas⬘ -toy-DI-tis). at the base of the skull between the sphenoid and occipital The mastoid process is a rounded projection of the mastoid por- bones. The petrous portion houses the internal ear and the tion of the temporal bone posterior and inferior to the external middle ear, structures involved in hearing and equilibrium. auditory meatus that serves as a point of attachment for several The middle ear contains three small auditory ossicles, the mal- neck muscles (see Figure 7.3c, d). The internal auditory meatus leus,incus, and stapes. It also contains the carotid foramen, (Figure 7.4) is the opening through which the facial (VII) and through which the carotid artery passes (see Figure 7.6a–d). vestibulocochlear (VIII) cranial nerves pass. The styloid process Posterior to thecarotid foramen and anterior to the occipi- (styl-⫽stake or pole) projects inferiorly from the inferior sur- tal bone is the jugular foramen, a passageway for the jugular face of the temporal bone and serves as a point of attachment for vein, formed by adjacent notches in the temporal and occipital muscles and ligaments of the tongue and neck (see Figure 7.3c, bones (see Figure 7.6c). d). Between the styloid process and the mastoid process is the stylomastoid foramen, through which the facial (VII) nerve and CHECKPOINT stylomastoid artery pass (see Figure 7.6c, d). 4. What structures form the zygomatic arch? Incus Malleus FRONTAL BONE Stapes Sella turcica: Dorsum sellae Tuberculum sellae PARIETAL BONE Hypophyseal fossa Frontal sinus Squamous suture ETHMOID BONE: Crista galli Cribriform plate TEMPORAL BONE Perpendicular plate Lambdoid suture NASAL BONE OCCIPITAL BONE SPHENOID BONE External occipital Sphenoidal sinus protuberance Internal auditory meatus VOMER Mastoid portion SPHENOID BONE MAXILLA Hypoglossal canal PALATINE BONE Occipital condyle MANDIBLE Pterygoid process (b) Medial view of sagittal section With which bones does the temporal bone articulate? 174 CHAPTER 7 • THE SKELETAL SYSTEM: THE AXIAL SKELETON EXHIBIT 7.D Cranial Bones—Occipital Bone (Figure 7.5) OBJECTIVE Surface Features • Identify the location and surface features of the occipital The foramen magnum (⫽large hole) is in the inferior part of the bone. bone. Within this foramen, the medulla oblongata (inferior part of the brain) connects with the spinal cord. The vertebral arter- Description ies, spinal arteries, and accessory (XI) nerve also pass through The occipital bone (ok-SIP-i-tal; occipit-⫽back of head) forms this foramen. The occipital condyles are two oval processes with the posterior part and most of the base of the cranium. When convex surfaces, one on either side of the foramen magnum (see viewed from behind, it appears as a platelike bone with a some- Figure 7.6a–d). They articulate with depressions on the first cer- what triangular shape. Its inferior portion is a thick, blocklike vical vertebra (atlas) to form the atlanto-occipital joints. Superior region that surrounds the junction of the brain and spinal cord to each occipital condyle on the inferior surface of the skull is the (Figure 7.5; also see Figure 7.3c, d). hypoglossal canal (hypo-⫽under; -glossal⫽tongue), through which Figure 7.5 Posterior view of the skull. The sutures are exaggerated for emphasis. The occipital bone forms most of the posterior and inferior portions of the cranium. Sagittal suture PARIETAL BONES Sutural bones OCCIPITAL BONE Lambdoid suture Superior nuchal line External occipital protuberance TEMPORAL BONE Inferior nuchal line Mastoid process Foramen magnum Styloid process Occipital condyle Inferior nasal concha Hard palate: Horizontal plate of palatine bone VOMER Palatine process of maxilla MANDIBLE (a) Posteroinferior view EXHIBIT 7.D 175 the hypoglossal (XII) nerve and a branch of the ascending pha- occipital protuberance to the seventh cervical vertebra. Extend- ryngeal artery pass (see Figure 7.4). ing laterally from the protuberance are two curved lines, the The external occipital protuberance is the most prominent mid- superior nuchal lines, and below these are two inferior nuchal lines, line projection on the posterior surface of the bone just superior which are areas of muscle attachment (Figure 7.5b). It is possi- to the foramen magnum. You may be able to feel this structure ble to view the parts of the occipital bone, as well as surrounding as a definite bump, the most prominent protrusion on the back structures, in the inferior view of the skull in Figure 7.6c, d. of your head, just above your neck (Figure 7.5b). A large fi- brous, elastic ligament, the ligamentum nuchae ( nucha-⫽nape of CHECKPOINT 5. What structures pass through the hypoglossal canal? neck), which helps support the head, extends from the external PARIETAL BONES Sagittal suture Sutural bones OCCIPITAL BONE Lambdoid suture External occipital Superior nuchal line protuberance TEMPORAL BONE Inferior nuchal line Foramen magnum Mastoid process Zygomatic arch Middle nasal concha Styloid process INFERIOR NASAL CONCHA VOMER Hard palate: Horizontal plate of palatine bone MANDIBLE Palatine process of maxilla (b) Posteroinferior view Which bones form the posterior, lateral portion of the cranium? 176 CHAPTER 7 • THE SKELETAL SYSTEM: THE AXIAL SKELETON EXHIBIT 7.E Cranial Bones—Sphenoid Bone (Figure 7.6) OBJECTIVE bone. The sphenoid bone lies posterior and slightly superior to • Identify the location and surface features of the sphenoid the nasal cavity and forms part of the floor, sidewalls, and rear wall of the orbit (see Figure 7.12). bone. Description Surface Features ˉ The sphenoid bone (SFE-noyd⫽wedge-shaped) lies at the mid- The shape of the sphenoid resembles a butterfly with outstretched dle part of the base of the skull (Figure 7.6a–d). This bone is wings (Figure 7.6e, f). The body of the sphenoid is the hollowed, called the keystone of the cranial floor because it articulates with cubelike medial portion between the ethmoid andoccipital bones. all the other cranial bones, holding them together. When you The hollow of the body is the sphenoidal sinus, which drains via a view the floor of the cranium superiorly (Figure 7.6a, b), note the narrow opening into the superior aspect of the nasal cavity (see sphenoid articulations: anteriorly with the frontal and ethmoid Figure 7.13c). The sella turcica (SEL-a TUR-si-ka; sella⫽ saddle; bones, laterally with the temporal and parietal bones, anterola- turcica⫽Turkish) is a bony, saddle-shaped structure on the su- terally with the parietal bones, and posteriorly with the occipital perior surface of the body of the sphenoid (Figure 7.6a, b). Figure 7.6 Sphenoidbone. The sphenoid bone is called the keystone of the cranial floor because it articulates with all other cranial bones, holding them together. View Transverse plane FRONTAL BONE ETHMOID BONE: Crista galli Olfactory foramina Cribriform plate Coronal suture SPHENOID BONE: Greater wing Lesser wing Tuberculum sellae Superior orbital fissure Hypophyseal fossa Sella Foramen rotundum turcica Dorsum sellae Foramen ovale Foramen spinosum Squamous suture Foramen lacerum TEMPORAL BONE: Petrous portion Hypoglossal canal Internal auditory meatus Foramen magnum Jugular foramen PARIETAL BONE OCCIPITAL BONE Lambdoid suture (a) Superior view of sphenoid bone in floor of cranium EXHIBIT 7.E 177 The an terior part of the sella turcica, which forms the horn Between the body and lesser wing just anterior to the sella tur- of the saddle, is a ridge called the tuberculum sellae. The seat of cica is the optic foramen or canal ( optic⫽eye), through which the the saddle is a depression, the hypophyseal fossa (h ¯-po-FIZ-e ˉ-al), optic (II) nerve and ophthalmic artery pass into the orbit (Figure which contains the pituitary gland. The posterior part of the 7.6e, f). Lateral to the body between the