2.7 Anatomy Chapter 7

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2.7 Anatomy Chapter 7
2010-09-30 00:53:32
Bones PartI Axial Skeleton

The Skull, Vertebral Column, Thoracic Cage, Disorders
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  1. Skeleton Overview
    Consists of bones, cartilages, joints (articulations), and ligaments

    • 206 bones total, grouped into appendicular (upper and lower limbs) skeleton, and axial (skull, vertebrae, thoracic cage) skeleton
    • 80 bones in axial skeleton
  2. The Skull (Overview/Function)
    Facial bones
    • 1. Cranium: enclose and protect the brain, provide attachment sites for head and neck muscles
    • 2. Facial bones:
    • a. Form the framework of the face
    • b. Form cavities for the sense organs of sight, taste, and smell
    • c. Provide openings for the passage of air and food
    • d. Hold the teeth
    • e. Anchor the muscles of the face
  3. Cranial Bones:
    Parietal Bones and the Major Sutures
    • Sutures:
    • 1. Coronal: (1) where parietal meets frontal bone
    • 2. Squamous: (10) where parietal meets temporal
    • 3. Sagittal (not shown) where right/left parietal bones meet
    • 4. Lamboid (8) where parietal meets occipital (resembles greek lambda)
  4. Cranial Bones:
    Frontal Bone
    • Forms forehead and roofs of the orbits
    • - Supraorbital Ridge (superciliary arches): slight protrusions superior to the orbits, forms eyebrows
    • - Supraorbital Foramen: a hole/notch above the orbits; transmits the supraorbital nerve/artery that supply the forehead
    • - glabella: smooth part between the eyebrows (unibrow area)
  5. Cranial Bones:
    Occipital Bone
    • Posterior part of the cranium/cranial base
    • - internally forms the walls of posterior cranial fossa, which holds the cerebellum
    • - Foramen magnum: "large hole" where the brain connects to the spinal cord
    • - Occipital condyles: rockerlike structures by the foramen magnum; articulate with the first vertebrae to allow head to nod
  6. Cranial Bones:
    Temporal Bones
    • Lie inferior to parietal bones; "time: gray hairs appear first at the temples"
    • - zygomatic process: projects anteriorly to meet zygomatic bone
    • - mandibular fossa: oval basin on the inferior surface of zygomatic process; receives the mandible and forms the temporomandibular joint (jaw)
    • - auditory meatus (acoustic meatus): ear canal; where sound enters the ear
    • - styloid process: needle-like projection below tympanic region; attachment point for muscles of the tongue and pharynx and for a ligament that connects the skull to the hyoid bone of the neck
    • - mastoid process: an anchoring site for some neck muscles
  7. Cranial Bones:
    Sphenoid Bone
    • Spans the width of cranial floor; "bat-like" keystone: articulates with every cranial bone
    • - greater wings: flag-shaped; project laterally, forming parts of middle cranial fossa and orbit
    • - lesser wings: horn-shaped; form part of the floor of the anterior cranial fossa and part of the orbit
    • - sella turcica: saddle-shaped prominence; holds pituitary gland (hypophysis)
  8. Cranial Bones:
    Ethmoid Bone
    • Most deeply situated; anterior to the sphenoid bone, posterior to the nasal bones, between the orbits
    • - cribriform plates: contribute to the roof of nasal cavity and floor of the anterior cranial fossa; perforated for passage of olfactory nerve filaments (site of olfactory bulbs)
    • - crista galli: between cribriform plates; fibrous membrane attaches and helps secure the brain in the cranial cavity
  9. Facial Bones:
    • U-shaped lower jawbone; largest, strongest bone in the face
    • - mental foramen: transmits blood vessels and nerves to lower lip and skin of the chin
    • - madibular foramen: transmits nerve responsible for tooth sensation (dental anesthetic administration site)
    • - mandibular notch: U-shaped depression separating coronoid and condylar processes
    • - mandibular condyle: head of mandible; articulates with the temporal bone to form temporomandibular joint
    • - coronoid process: anterior flat, triangular projection; where temporalis muscle inserts
    • - alveolar sockets: tooth sockets
  10. Facial Bones:
    Maxillary Bones
    • Form upper jaw and central part of facial skeleton; keystones of the facial skeleton: articulates with all other facial bones except mandible
    • - infraorbital foramen: transmits infraorbital nerve to face
  11. Facial Bones:
    Zygomatic Bones
    • Cheekbones; joins zygomatic processes of temporal bone, frontal bone, and maxilla
    • - zygomatic arch: where zygomatic process of temporal bone meets the zygomatic bone
  12. Facial Bones:
    Nasal Bones
    Paired, rectangular bones that join medially to form the bridge of the nose; articulate with frontal bone, maxillae, ethmoid bone
  13. Facial Bones:
    Lacrimal bones
    • Delicate, fingernail-shaped; located in medial orbital walls
    • articulate with frontal, ethmoid, and maxilla
    • - contains deep fossa that contains lacrimal sacs that gathers tears
  14. Facial Bones:
    Palatine Bones
    Lie posterior to the maxillae; forms the posterior part of the hard palate
  15. Facial Bones:
    Slender, plow shaped; lies in the nasal cavity forming the interior nasal septum (below ethmoid)
  16. Facial Bones:
    Inferior Nasal Conchae
    • Thin, curved bones in the nasal cavity that projects medially just inferior to the middle nasal conchae of the ethmoid bone
    • - largest of three pairs of conchae
  17. Paranasal Sinuses
    • Air-filled sinuses surrounding the nasal cavity.
    • - Extensions of the nasal cavity, lined by mucous membrane and probably serve the same function of warming, moistening, and filtering inhaled air.
    • - Also lighten the skull
  18. Orbits
    Superior orbital fissure
    Inferior orbital fissure
    Walls of orbit formed by 7 bones

    Superior orbital fissure: part of sphenoid bone; allows passage of cranial nerves and vein

    Inferior orbital fissure: part of Maxilla; permits maxillary branch of cranial nerve V, zygomatic nerve, and blood vessels
  19. Hyoid Bone
    • U-shaped bone just under the mandible.
    • Has a body and two pairs of horns: the greater and lesser horns
    • - acts as a movable base for the tongue
    • - body and greater horns are points of attachment for neck muscles that raise and lower the larynx during swallowing
  20. The Vertebral Column
    • General Characteristics:
    • - 26 bones
    • - extends from skull to the pelvis
    • - 33 bones in fetus/infant, nine later fuse to become sacrum and coccyx

    • Functions:
    • - main support of the body axis
    • - transmits weight of the trunk to the lower limbs
    • - surrounds and protects spinal cord
    • - provides attachment points for ribs and muscles of the neck and back
  21. The Vertebral Column
    Regions and Normal Curvatures
    • 5 major regions:
    • - Cervical: 7 vertebrae of the neck
    • - Thoracic: 12 vertebrae
    • - Lumbar: 5 vertebrae that support the lower back
    • become progressively larger from cervical to lumbar regions as weight supported increases
    • - Sacrum: articulates with the hip bones of the pelvis
    • - Coccyx: tailbone

    • S-shaped: cervical and lumbar regions are concave posteriorly, thoracic and sacral curvatures are convex
    • - increase resilience of the spine, allowing it to function like a spring rather than a rod.

    • Primary curvatures: thoracic and sacral curvatures are well developed at birth (convex = C-shaped as infant)
    • Secondary curvatures: cervical and lumbar, develop during first 2 years of childhood (when baby first holds head up; 3mo. & when baby learns to walk; 1yr)
  22. The Vertebral Column:
    Intervertebral Discs
    • A cushion-like pad composed of an inner sphere (nucleus pulposus) and an outer collar of about 12 concentric rings (anulus fibrosis)
    • - nucleus pulposus: gelatinous, acts like rubber ball, absorbs compressive stress.
    • - anulus fibrosis: outer rings are ligaments, inner rings are fibrocartilage; main function is to contain nucleus pulposus, also bind successive vertebrae, resisting tension, and absorbing compressive forces

    act as shock absorbers; thickest in lumbar and cervical regions; 25% vertebral height, shorten 1-2 cm during the day
  23. The Vertebral Column
    Herniated Disc
    Involves rupture of anulus fibrosus followed by protrusion of nucleus pulposus.

    Caused by: severe or sudden physical trauma to the spine; aging causes nucleus pulposus to lose its cushioning properties over time and weakens and tears anulus fibrosus.

    • What happens: rupture proceeds toward spinal nerve roots exiting the spinal cord, pressure causes pain/numbness
    • Treatment: exercise, physical therapy, massage, heat therapy, painkillers
  24. The Vertebral Column
    General Structure of Vertebrae
    • All vertebrae share a common structural pattern:
    • - Body (centrum): disc-shaped, weight bearing region
    • - Vertebral foramen: an opening that forms the vertebral canal that houses the spinal cord
    • - Pedicles: "little feet"; short bony walls that project posteriorly from the vertebral body
    • - Laminae: "sheets"; flat roof plates that complete the vertebral arch posteriorly
    • - Spinous process: a median, posterior projection arising at the junction of the two laminae
    • - Transverse process: projects laterally from each pedicle-lamina junction
    • Both processes are attachment sites for muscles allowing movement, and ligaments that help stabilize
  25. The Vertebral Column
    Cervical Vertebrae
    • The 7 cervical vertebrae (C1-C7) are the smallest and lightest.
    • atlas: lacks body and spinous process; essentially a ring of bone with anterior/posterior arches and a lateral mass on each side. Superior articular facets receive occipital condyles and "carry" the skull (like the Greek giant Atlas carries the heavens). Participate in flexion and extension of the head on the neck. (nod head to say "yes")
    • axis: has knob-like dens ("tooth") projecting superiorly from its body (which is actually the "body" of the atlas) that acts as a pivot for the rotation of the atlas and skull; allows head to rotate side to side on the neck's axis (shake head to say "no")
    • Other vertebrae:
    • - body is wider laterally
    • - spinous process is short, except for C7, and bifid (split in two)
    • - foramen is large and generally triangular
    • - transverse process contains a hole (foramen) where blood vessels pass to serve the brain
    • - superior articular facets face superoposteriorly, inferior articular facets face inferoanteriorly to allow neck movements

    C7 is larger, called vertebra prominens, used physically as landmark
  26. The Vertebral Column
    Thoracic Vertebrae
    • All 12 thoracic vertebrae (T1-T12) articulate with ribs.
    • - vertebral body is roughly heart-shaped
    • - head of ribs articulate with costal facets
    • - spinous process is long and points inferiorly
    • - vertebral foramen is circular
  27. The Vertebral Column
    Lumbar Vertebrae
    • The small of the back (L1-L5); receives most stress
    • - bodies are massive and appear kidney-shaped
    • - pedicles and laminae are shorter and thicker
    • - spinous processes are short, flat, and hatchet-shaped
    • - vertebral foramen is triangular
  28. The Vertebral Column
    • Sacrum
    • Curved, triangular bone that shapes the posterior wall of the pelvis.
    • - articulates superiorly with L5 via superior articular processes, inferiorly with coccyx
    • - composed of 5 fused vertebrae

    • Coccyx
    • Small and triangular tailbone.
    • - consists of 4 fused vertebrae
    • - generally useless
  29. The Thoracic Cage
    • Bony framework of the chest, roughly barrel-shaped.
    • Includes thoracic vertebrae, ribs, sternum, and costal cartilages

    • Functions: protective cage around heart, lungs, other organs.
    • - Supports shoulder girdles and upper limbs
    • - Provides attachment points for muscles of the back, neck, chest, shoulders, and for breathing
  30. The Thoracic Cage
    • The breastbone; dagger-shaped
    • Consists of three sections:
    • - manubrium: "knife handle"; the superior section, shaped like the knot in a necktie; clavicular notches articulate with clavicles; articulates below with 1st and 2nd ribs
    • - body: midportion that makes up bulk of sternum; formed from 4 separate bones that fuse after puberty; sides are notched where it articulates with ribs 2-7
    • - xiphoid process: forms inferior end of sternum; tongue-shaped plate of hylaine cartilage, doesn't fully ossify until age 40.

    • Anatomical landmarks:
    • - Jugular notch: groove at base of neck; lies between 2nd and 3rd thoracic vertebrae
    • - Sternal angle: joint between manubrium and body; in line with disc between 4th and 5th thoracic vertebrae; at the level of the 2nd ribs
  31. 1The Thoracic Cage
    Twelve pairs of ribs, all attach to thoracic vertebrae posteriorly
  32. True ribs: superior 7 pairs that attach directly to the sternum via costal cartilages
    • False ribs: inferior 5 pairs that attach to the sternum indirectly or not at all
    • - Floating ribs: have no anterior attachments