A&PI Chapter 07
Chapter 07
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The Skeletal System: The Axial Skeleton
Lecture Outline
• Familiarity with the names, shapes, and positions of individual bones helps to locate other organs and to understand how muscles produce different movements due to attachment on individual bones and the use of leverage with joints.
• The bones, muscles, and joints together form the musculoskeletal system.
Chapter 7• Axial Skeleton
• Appendicular Skeleton
• The axial skeleton consists of bones arranged along the longitudinal axis of the body. The parts of the axial skeleton, composed of 80 bones, are the skull, hyoid bone, vertebral column, sternum, and ribs (Figure 7.1).
• The appendicular skeleton comprises one of the two major divisions of the skeletal system.It consists of 126 bones in the upper and lower extremities (limbs or appendages) and the pectoral (shoulder) and pelvic (hip) girdles, which attach them to the rest of the skeleton.
Types of Bones
• 5 basic types of bones:
• Sutural bones = in joint between skull bones
• There are two major types of surface markings.
– Processes are projections or outgrowths that either help form joints or serve as attachment points for connective tissue.
• Table 7.2 describe the various surface markings along with examples of each.
Bone Surface Markings• Foramen = opening
• Fossa = shallow depression
• Sulcus = groove
• Meatus = tubelike passageway or canal
• Condyle = large, round protuberance
• Facet = smooth flat articular surface
• Trochanter = very large projection
• Tuberosity = large, rounded, roughened projection
• Learning the terms found in this Table will simplify your study of the skeleton.
• The skull, composed of 22 bones, consists of the cranial bones (cranium) and the facial bones (face) (Figures. 7.3 through 7.8).
• General Features
– Certain skull bones contain mucous membrane lined cavities called paranasal sinuses.
– The only moveable bone of the skull, other than the ear ossicles within the temporal bones, is the mandible.
– Immovable joints called sutures hold the skull bones together.
The Skull
• 8 Cranial bones
– protect brain & house ear ossicles
– muscle attachment for jaw, neck & facial muscles
• 14 Facial bones
– protect delicate sense organs -- smell, taste, vision
– support entrances to digestive and respiratory systems
Frontal
Parietal (2)
Temporal (2)
Occipital
Frontal Bone
• Forehead, roof of orbits, & anterior cranial floor
• Frontal suture gone by age 6 (metopic suture)
• Supraorbital margin and frontal sinus
• A “black eye” results from accumulation of fluid and blood in the upper eyelid following a blow to the relatively sharp supraorbital margin (brow line).
cranial bone functions
• They protect the brain.
– Their inner surfaces attach to membranes that stabilize the positions of the brain, blood vessels, and nerves.
– The outer surfaces of cranial bones provide large areas of attachment for muscles that move the various parts of the head.
– Facial bones form the framework of the face and protect and provide support for the nerves and blood vessels in that area.
• Cranial and facial bones together protect and support the special sense organs.
• Parietal
– sides & roof of cranial cavity
• Temporal
– temporal squama
– zygomatic process forms part of arch
– external auditory meatus
– mastoid process
– styloid process
– stylomastoid foramen(VII)
– mandibular fossa (TMJ)
– petrous portion (VIII)
• Temporal
– carotid foramen– jugular foramen• Occipital
• Base of skull
• Pterygoid processes are attachment sites for jaw muscles
• Body is a cubelike portion holding sphenoid sinuses
• Greater and lesser wings
• Pterygoid processes
• Lesser wing & greater wing
• Sella turcica holds pituitary gland
• Optic foramen
• The ethmoid bone forms part of the anterior portion of the cranial floor, the medial wall of the orbits, the superior portion of the nasal septum, and most of the superior side walls of the nasal cavity. It is a major superior supporting structure of the nasal cavity (Figures 7.11, 7.13).
• Crista galli attaches to the membranes that cover the brain
• Lateral masses contain ethmoid sinuses
• Perpendicular plate is upper part of nasal septum
• Superior & middle nasal concha or turbinates
Nasal (2) Maxillae (2) Zygomatic (2)
Mandible (1) Lacrimal (2) Palatine (2)
Inferior nasal conchae (2) Vomer (1)
• Floor of orbit, floor of nasal cavity or hard palate
• Maxillary sinus
• Alveolar processes hold upper teeth
• Cleft palate is lack of union of maxillary bones
• Cheekbones
• Lateral wall of orbit along with sphenoid
• Part of zygomatic arch along with part of temporal
• Lacrimal bones
• Inferior nasal concha or turbinate (not part of ethmoid)
• Body, angle & rami
• Condylar & coronoid processes
• Alveolar processes for lower teeth
• Mandibular & mental foramen
• The mandible articulates with the temporal bone to form the temporomandibular joint (Figure 7.4).
• Temporomandibular joint (TMJ) syndrome is dysfunction to varying degrees of the temporomandibular joint. Causes appear to be numerous and the treatment is similarly variable.
• Palatine
• Vomer
– posterior part of nasal septum
• The nasal septum is a vertical partition that divides the nasal cavity into right and left sides (Figure 7.11).
• A deviated nasal septum is a lateral deflection of the septum from the midline, usually resulting from improper fusion of septal bones and cartilage.
• Divides nasal cavity into left and right sides
• Formed by vomer, perpendicular plate of ethmoid and septal cartilage
• Deviated septum does not line in the midline
• The orbits contain the eyeballs and associated structures and are formed by seven bones of the skull (Figure 7.12).
• Five important foramina are associated with each orbit
• Table 7.4 describes major openings of skull
• In which bone would you find the following and what is their function?
• Sutures are immovable joints found only between skull bones and hold skull bones together.
• Sutures include the coronal, sagittal, lamboidal,and squamous sutures, among others (Figures 7.4, 7.6).
• Lamboid suture unites parietal and occipital
• Sagittal suture unites 2 parietal bones
• Coronal suture unites frontal and both parietal bones
• Squamous suture unites parietal and temporal bones
• Paranasal sinuses are cavities in bones of the skull that communicate with the nasal cavity.
• Paired cavities in ethmoid, sphenoid, frontal and maxillary
• Lined with mucous membranes and open into nasal cavity
• Resonating chambers for voice, lighten the skull
• Sinusitis is inflammation of the membrane (allergy)
• Paired cavities in ethmoid, sphenoid, frontal and maxillary
• Lined with mucous membranes and open into nasal cavity
• Resonating chambers for voice, lighten the skull
• Sinusitis is inflammation of the membrane (allergy)
• Fontanels are dense connective tissue membrane-filled spaces between the cranial bones of fetuses and infants. They remain unossified at birth but close early in a child’s life (Figure 7.14).
• Fontanels have two major functions.
• Dense connective tissue membrane-filled spaces
• Unossified at birth but close early in a child's life.
• The hyoid bone is a unique component of the axial skeleton because it does not articulate with any other bones.
• The hyoid bone consists of a horizontal body and paired projections, the lesser and greater horns. (Figure 7.15)
Hyoid Bone
• The vertebral column, along with the sternum and ribs, makes up the trunk of the skeleton.
• The 26 bones of the vertebral column are arranged into five regions: cervical, thoracic, lumbar, sacral, and coccygeal (Figure 7.16a).
Vertebral Column
• Backbone or spine built of 26 vertebrae
• Five vertebral regions
– cervical vertebrae (7) in the neck
• Between adjacent vertebrae absorbs vertical shock
• Permit various movements of the vertebral column
• Fibrocartilagenous ring with a pulpy center
• The four normal vertebral curves are the cervical and lumbar (anteriorly convex curves) and thoracic and sacral (anteriorly concave curves) (Figure 7.16b).
• Between adjacent vertebrae, from the first cervical (atlas) to the sacrum, are intervertebral discs that form strong joints, permit various movements of the vertebral column, and absorb vertical shock (Figure 7.16d).
• Parts of a typical vertebra include a body, a vertebral arch, and several processes (Figure 7.17).
• Body
• Vertebral arch
• Vertebral foramen
• Seven processes
• Vertebral notches
• Spinal canal is all vertebral foramen together
• Intervertebral foramen are 2 vertebral notches together
• There are 7 cervical vertebrae (Figure 7.18a).
• Smaller bodies but larger spinal canal
• Transverse processes
– shorter, with transverse foramen for vertebral artery
• Spinous processes of C2 to C6 often bifid
• 1st and 2nd cervical vertebrae are unique - atlas & axis
• Atlas -- ring of bone, superior facets for occipital condyles
• Axis -- dens or odontoid process is body of atlas
• There are 12 thoracic vertebrae (Figure 7.19).
• These vertebrae articulate with the ribs.
Thoracic Vertebrae• Larger and stronger bodies
• Longer transverse & spinous processes
• Facets or demifacets on body for head of rib
• Facets on transverse processes (T1-T10) for tubercle of rib
• There are 5 lumbar vertebrae (Figure 7.20).
• They are the largest and strongest vertebrae in the column.
• Table 7.4 summarizes the major structural differences among the cervical, thoracic, and lumbar vertebrae.
• Strongest & largest
• Short thick spinous & transverse processes
• The sacrum is formed by the union of 5 sacral vertebrae (Figure 7.21a) and serves as a strong foundation for the pelvic girdle.
• Table 8.1 shows the differences between the male and female sacrum.
• Union of 5 vertebrae (S1 - S5) by age 30
• Sacral canal ends at sacral hiatus
• Auricular surface & sacral tuberosity of SI joint
• The coccyx is formed by the fusion of 4 coccygeal vertebrae (Figure 7.21).
• Caudal anesthesia (epidural block), frequently used during labor (in childbirth), causes numbness in the regions innervated by the sacral and coccygeal nerves (approximately from the waist to the knees).
• Union of 4 vertebrae (Co1 - Co4) by age 30
• Caudal or epidural anesthesia during delivery
• The term thorax refers to the entire chest.
• The skeletal part of the thorax (a bony cage) consists of the sternum, costal cartilages, ribs, and the bodies of the thoracic vertebrae (Figure 7.22).
• The thoracic cage encloses and protects the organs in the thoracic and superior abdominal cavities. It also provides support for the bones of the shoulder girdle and upper limbs.
• The sternum is located on the anterior midline of the thoracic wall.
• It consists of three parts: manubrium, body, and xiphoid process (Figure 7.22).
• Manubrium
• Body
• Xiphoid
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