7 2 The Vertebral Column General Characteristics Also

7. 2 The Vertebral Column General Characteristics • Also called spine or spinal column • Functions – transmit weight of trunk to lower limbs – surround and protect spinal cord – provide attachment points for ribs and muscles • Flexible curved structure contains 26 irregular bones called vertebrae in five major regions © 2016 Pearson Education, Inc.

General Characteristics (cont. ) • Regions and curvatures – 28 long vertebral column 1. Cervical: consists of 7 vertebrae 2. Thoracic: 12 vertebrae 3. Lumbar: 5 vertebrae Remember meal times: 7 am, 12 noon, and 5 pm 4. Sacrum: one bone, formed from fusion of several bones, articulates with hip 5. Coccyx: also fused bones that form terminus of column © 2016 Pearson Education, Inc.

Figure 7. 16 The vertebral column. C 1 2 3 4 5 6 7 Cervical curvature 7 vertebrae, C 1: C 7 T 1 Spinous process 2 3 Transverse processes 4 5 6 7 Thoracic curvature 12 vertebrae, T 1: T 12 8 9 10 11 Intervertebral discs Intervertebral foramen 12 L 1 2 3 Lumbar curvature 5 vertebrae, L 1: L 5 4 5 Sacral curvature 5 fused vertebrae sacrum Coccyx 4 fused vertebrae © 2016 Pearson Education, Inc. Anterior view Right lateral view

General Characteristics (cont. ) • Intervertebral discs – Cushion-like pad sandwiched between vertebrae that act as shock absorbers Spinal cord Herniated portion of disc Intervertebral disc Superior view of a herniated intervertebral disc © 2016 Pearson Education, Inc.

Figure 7. 17 d Ligaments and fibrocartilage discs uniting the vertebrae. Intervertebral disc Herniated disc MRI of lumbar region of vertebral column in sagittal section showing herniated disc © 2016 Pearson Education, Inc.

General Structure of Vertebrae • All have common structural pattern consisting of: – Body (centrum), – Vertebral arch composed of: – Vertebral foramen: enclosure formed by body and vertebral arch coming together – Vertebral canal: series of vertebral foramina – Intervertebral foramina: lateral openings between vertebrae for passage of spinal nerves © 2016 Pearson Education, Inc.

Figure 7. 19 Typical vertebral structures. Posterior Spinous process Transverse process Vertebral arch Vertebral

General Structure of Vertebrae (cont. ) Posterior • Vertebrae have processes: Spinous process Transverse process – Spinous process: Vertebral projects arch posteriorly – Transverse processes (2): project laterally Vertebral foramen Body Anterior © 2016 Pearson Education, Inc.

Regional Vertebral Characteristics • Cervical vertebrae – C 1 to C 7: smallest, lightest vertebrae – C 3 to C 7 share following features: • Oval-shaped body • spinous processes are split (bifid) C 2 -C 6 – Except in C 7 • Large, triangular vertebral foramen • C 7 is vertebra prominens; large and can be felt through skin, used as a landmark © 2016 Pearson Education, Inc.

Table 7. 2 -2 Regional Characteristics of Cervical, Thoracic, and Lumbar Vertebrae (continued) ©

Table 7. 2 -3 Regional Characteristics of Cervical, Thoracic, and Lumbar Vertebrae (continued) ©

Figure 7. 21 a Posterolateral views of articulated vertebrae. Dens of axis Transverse ligament of atlas C 1 (atlas) C 2 (axis) C 3 Bifid spinous process Transverse processes C 7 (vertebra prominens) Cervical vertebrae © 2016 Pearson Education, Inc.

Regional Vertebral Characteristics (cont. ) • Cervical vertebrae (cont. ) – C 1 (atlas) and C 2 (axis) have unique features – Atlas (C 1) • No body or spinous process • Superior surfaces articulate with occipital condyles • Movement for nodding head “Yes” © 2016 Pearson Education, Inc.

Figure 7. 20 a The first and second cervical vertebrae. C 1 Posterior Vertebral

Figure 7. 20 b The first and second cervical vertebrae. Posterior Transverse process Vertebral

Regional Vertebral Characteristics (cont. ) – Axis (C 2) • Has body and processes like other vertebrae • Dens knoblike feature that projects superiorly into arch of atlas – Dens is the “missing” body of atlas • Dens is a pivot for rotation of atlas • Movement allows side to side rotation for saying “No” © 2016 Pearson Education, Inc.

Figure 7. 20 c The first and second cervical vertebrae. Posterior C 2 Spinous

Figure 7. 20 d The first and second cervical vertebrae. Posterior Transverse foramen in

Figure 7. 21 a Posterolateral views of articulated vertebrae. Dens of axis Transverse ligament of atlas C 1 (atlas) C 2 (axis) C 3 Inferior articular process Bifid spinous process Transverse processes C 7 (vertebra prominens) Cervical vertebrae © 2016 Pearson Education, Inc.

Regional Vertebral Characteristics (cont. ) • Thoracic vertebrae – T 1 to T 12 increase in size and articulate with ribs – Unique characteristics: • Body is heart shaped • Vertebral foramen is circular • Long, sharp spinous process points inferiorly © 2016 Pearson Education, Inc.

Figure 7. 21 b Posterolateral views of articulated vertebrae. Transverse process Transverse costal facet (for rib) Intervertebral disc Body Spinous process Thoracic vertebrae © 2016 Pearson Education, Inc. Inferior costal facet (for rib)

Regional Vertebral Characteristics (cont. ) • Lumbar vertebrae – L 1 to L 5 “small of back”; receives most stress, so bodies are massive – Other characteristics: • Flat, hatchet-shaped spinous processes point posteriorly • Vertebral foramen is triangular © 2016 Pearson Education, Inc.

Figure 7. 21 c Posterolateral views of articulated vertebrae. Transverse process Spinous process Lumbar

Regional Vertebral Characteristics (cont. ) • Sacrum: triangular bone shapes posterior wall of pelvis; made from five fused vertebrae (S 1–S 5) – Articulates with L 5 – Articulates inferiorly with coccyx and laterally with hip bones © 2016 Pearson Education, Inc.

Regional Vertebral Characteristics (cont. ) • Sacrum (cont. ) – Sacral canal: continuation of vertebral canal – Sacral hiatus: large opening at end of canal • Coccyx: tailbone formed from three to five fused vertebrae; articulates superiorly with sacrum – Very little function © 2016 Pearson Education, Inc.

Figure 7. 22 a The sacrum and coccyx. Ala Body of first sacral vertebra

Figure 7. 22 b The sacrum and coccyx. Ala Sacral canal Coccyx © 2016

7. 3 Thoracic Cage • Composed of: – Thoracic vertebrae posteriorly – Sternum and costal cartilages anteriorly – Ribs laterally • Functions – Protects vital organs of thoracic cavity – Supports shoulder girdles and upper limbs – Provides attachment sites for muscles of neck, back, chest, and shoulders © 2016 Pearson Education, Inc.

Figure 7. 23 a The thoracic cage. Clavicular notch Sternum • Manubrium • Body True ribs (1– 7) • Xiphoid process False ribs (8– 12) Intercostal spaces © 2016 Pearson Education, Inc. L 1 Floating Vertebra ribs (11, 12) Skeleton of the thoracic cage, anterior view Costal cartilage

Sternum • Also called the breastbone; consists of three fused bones: – Manubrium: superior

Ribs • 12 pairs form sides of thoracic cage • All attach posteriorly to bodies and transverse processes of thoracic vertebrae • True ribs (pairs 1– 7) – Attach directly to sternum by individual costal cartilages • False ribs (pairs 8– 10) – Attach indirectly to sternum by joining costal cartilage of rib above • Vertebral (floating) ribs (pairs 11– 12) – No attachment to sternum © 2016 Pearson Education, Inc.

Figure 7. 23 a The thoracic cage. True ribs (1– 7) False ribs (8–

Figure 7. 24 b Ribs. tubercle of rib Spinous process Shaft (for tubercle of rib) Neck of rib Head of rib (for head of rib) Body of thoracic vertebra Superior view of the articulation between a rib and a thoracic vertebra © 2016 Pearson Education, Inc.