The Vertebral Column and the Bony Thorax The Skeleton Part B The Vertebral Column and the Bony Thorax

The Vertebral Column

The Vertebral Column Flexible curved structure Extends from Skull to Pelvis 26 irregular bones in adults 33 separate bones in the fetus and infants 9 of the 33 fuse to form the sacrum and coccyx

The Vertebral Column Transmits weight from trunk to lower limbs Surrounds and protects the spinal cord Provides attachment points for ribs and muscles of the back and neck

The Vertebral Column Vertebrae separated by intervertebral discs (fibrocartilage) Each vertebrae is given a name according to its location

The Vertebral Column Has five major divisions Cervical vertebrae 7 bones in neck Thoracic vertebrae 12 bones in torso Lumbar vertebrae 5 bones in lower back

The Vertebral Column Has five major divisions Sacrum Bone inferior to the lumbar Articulates with hip bones

The Vertebral Column Has five major divisions Coccyx 4 (sometimes 3 to 5) fused bones Everyone has same number of cervical vertebrae, but other areas vary in number in 5% of people

All mammals have 7 cervical vertebrae

The Vertebral Column Vertebrae has four curvatures Sinusoid shaped (S-shaped) Cervical and lumbar curvatures are Concave Thoracic and Sacral curvatures are Convex

The Vertebral Column Abnormal spine curvatures

Abnormal spine curvatures Scoliosis Abnormal lateral curve

Abnormal spine curvatures Kyphosis hunchback

Abnormal spine curvatures Lordosis swayback

Vertebral Column Major Supporting Ligaments Anterior and posterior longitudinal ligaments continuous bands down the front and back of the spine from the neck to the sacrum Short ligaments connect adjoining vertebrae together

Vertebral Column: Ligaments Figure 714a

Intervertebral Discs Cushionlike pad composed of two parts Nucleus pulposus – inner gelatinous nucleus that gives the disc its elasticity and compressibility Annulus fibrosus – surrounds the nucleus pulposus with a collar composed of collagen and fibrocartilage

Vertebral Column: Intervertebral Discs Nucleus pulposus Figure 7.14b

Vertebral Column: Intervertebral Discs Annulus fibrosus Figure 7.14b

Intervertebral Discs Acts as shock absobers Thickest in the lumbar and cervical regions Enhances the flexibility of these regions

Intervertebral Discs Account for about 25% of the height of the vertebral column Flatten some during the day We are always a few centimeters shorter at night

Intervertebral Discs Herniated (prolapsed) disc Commonly called ‘slipped disc’

Intervertebral Discs Slipped discs Usually involves rupture of the annulus fibrousus followed by protrusions of the spongy nucleus pulposus If protrusion presses on spinal cord or on spinal nerves, numbness or excruciating pain may result

General Structure of Vertebrae Spinous processes project posteriorly, and transverse processes project laterally Superior and inferior articular processes – protrude superiorly and inferiorly from the pedicle-lamina junctions Intervertebral foramina – lateral openings formed from notched areas on the superior and inferior borders of adjacent pedicles

General Structure of Vertebrae Body or centrum – disc-shaped, weight-bearing region Figure 7.15

General Structure of Vertebrae Vertebral arch – composed of pedicles and laminae that, along with the centrum, enclose the vertebral foramen Figure 7.15

General Structure of Vertebrae Vertebral foramina – make up the vertebral canal through which the spinal cord passes Figure 7.15

General Structure of Vertebrae Spinous processes project posteriorly Attachment sites for muscles that move the vertebral column and for ligaments that stabilize it Figure 7.15

General Structure of Vertebrae Transverse processes project laterally Figure 7.15

General Structure of Vertebrae Spinous and transverse processes are attachment sites for muscles that move the vertebral column and for ligaments that stabilize it

General Structure of Vertebrae Superior and inferior articular processes Protrude superiorly and inferiorly from the pedicle-lamina junctions

General Structure of Vertebrae Intervertebral foramina Lateral openings formed from notches areas on the superior and inferior borders of adjacent pedicles Spinal nerves from spinal cord pass through

Structure of a Typical Vertebrae Figure 5.16 Slide 5.29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

The Vertebral Column and the Bony Thorax The Skeleton Part B - 2 The Vertebral Column and the Bony Thorax

Regional Characteristics of Vertebrae Figure 5.17a, b Slide 5.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Cervical Vertebrae Seven vertebrae (C1-C7) are the smallest, lightest vertebrae C3-C7 are distinguished with an oval body, short spinous processes, and large, triangular vertebral foramina Each transverse process contains a transverse foramen

Regional Characteristics of Vertebrae Figure 5.17a, b Slide 5.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Cervical Vertebrae: The Atlas (C1) The atlas has no body and no spinous process It consists of anterior and posterior arches, and two lateral masses The superior surfaces of lateral masses articulate with the occipital condyles

Cervical Vertebrae: The Atlas (C1) Figure 7.16a, b

Cervical Vertebrae: The Atlas (C1) Figure 7.17a

Cervical Vertebrae: The Axis (C2) The axis has a body, spine, and vertebral arches as do other cervical vertebrae Unique to the axis is the dens The dens is a pivot for the rotation of the atlas

The Axis (C2) The dens projects superiorly from the body and is cradled in the anterior arch of the atlas

Cervical Vertebrae: The Axis (C2) Dens Figure 7.17a

Cervical Vertebrae C3 through C7 Table 7.2

Regional Characteristics of Vertebrae Thoracic Figure 5.17c, d Slide 5.30b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Thoracic Vertebrae There are twelve vertebrae (T1-T12) all of which articulate with ribs Figure 7.17b

Thoracic Vertebrae Major markings include two facets and two demifacets on the heart-shaped body, the circular vertebral foramen, transverse processes, and a long spinous process Figure 7.17b

Thoracic Vertebrae The location of the articulate facets prevents flexion and extension, but allows rotation of this area of the spine Figure 7.17b

Regional Characteristics of Vertebrae Lumbar Figure 5.17c, d Slide 5.30b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Lumbar Vertebrae The five lumbar vertebrae (L1-L5) are located in the small of the back and have an enhanced weight-bearing function Figure 7.17c

Lumbar Vertebrae They have short, thick pedicles and laminae, flat hatchet-shaped spinous processes, and a triangular-shaped vertebral foramen Figure 7.17c

Lumbar Vertebrae Orientation of articular facets locks the lumbar vertebrae together to provide stability Figure 7.17c

Sacrum Consists of five fused vertebrae (S1-S5), which shape the posterior wall of the pelvis Figure 7.18a

Sacrum It articulates with L5 superiorly, and with the auricular surfaces of the hip bones Figure 7.18a

Sacrum Major markings include the sacral promontory, transverse lines, alae, dorsal sacral foramina, sacral canal, and sacral hiatus Figure 7.18a

Coccyx - Tailbone The coccyx is made up of four (in some cases three to five) fused vertebrae that articulate superiorly with the sacrum Figure 7.18a

Sacrum and Coccyx Anterior view

Sacrum and Coccyx Posterior View Figure 7.18b

The Bony Thorax Thoracic cage Rib cage

The Bony Thorax Made up of three parts Sternum Ribs Thoracic vertebrae

The Bony Thorax The thoracic cage is composed of the thoracic vertebrae dorsally, the ribs laterally, and the sternum and costal cartilages anteriorly

Bony Thorax (Thoracic Cage) Functions Forms a protective cage around the heart, lungs, and great blood vessels Supports the shoulder girdles and upper limbs Provides attachment for many neck, back, chest, and shoulder muscles Uses intercostal muscles to lift and depress the thorax during breathing

Bony Thorax (Thoracic Cage) Figure 7.19a

Bony Thorax (Thoracic Cage) Figure 7.19b

Sternum (Breastbone) A dagger-shaped, flat bone that lies in the anterior midline of the thorax Results from the fusion of three bones – the superior manubrium, the body, and the inferior xiphoid process Anatomical landmarks include the jugular (suprasternal) notch, the sternal angle, and the xiphisternal joint

Ribs There are twelve pair of ribs forming the flaring sides of the thoracic cage All ribs attach posteriorly to the thoracic vertebrae

Ribs The superior 7 pair (true, or vertebrosternal ribs) attach directly to the sternum via costal cartilages

Ribs Ribs 8-10 (false, or vertebrocondral ribs) attach indirectly to the sternum via costal cartilage

Ribs Ribs 11-12 (floating, or vertebral ribs) have no anterior attachment

Ribs Figure 7.19a

Structure of a Typical True Rib Bowed, flat bone consisting of a head, neck, tubercle, and shaft Figure 7.20

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