The Skeleton Part C 7

Seven vertebrae (C1-C7) are the smallest, lightest vertebrae Cervical Vertebrae Seven vertebrae (C1-C7) are the smallest, lightest vertebrae C3-C7 are distinguished with an small oval body, short bifid spinous processes (except C7), and large, triangular vertebral foramina. Each transverse process contains a transverse foramen Superior facets directed superoposteriorly foramina Inferior facets directed inferoanteriorly

Cervical Vertebrae: Anatomical characteristics Movement’s allowed: Flexion and extension Rotation (greatest range of movement) Table 7.2

Cervical Vertebrae: The Atlas (C1) The first two cervical vertebrae, the atlas and the axis have no intervertebral disc between them, and they are highly modified, reflecting their special functions. The atlas is a ring bone, 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 , thus “ They carry the skull, just as Atlas supported the heavens in Greek mythology”. This joint allow you to nod “yes”. The inferior articular surfaces form joints with the axis.

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

Cervical Vertebrae: The Axis (C2) The axis has a body, spine, and vertebral arches as do other cervical vertebrae. It is not as specialized as atlas Unique to the axis is the dens, or odontoid process, which projects superiorly from the body and is cradled in the anterior arch of the atlas The dens is a pivot for the rotation of the atlas

Cervical Vertebrae: The Axis (C2) Figure 7.16c

Cervical Vertebrae: Anatomical view The spinous p. of C7 is much larger than those of other cervical vertebrae. Because it is visible through the skin C7 can be used as a landmark for counting the vertebrae and it is called “v. prominent” Figure 7.17a

Thoracic Vertebrae There are twelve vertebrae (T1-T12) all of which articulate with ribs. The first looks much like C7 and the last four like the lumbar vertebral structure. Increase in size from the first to the last Major markings include: two facets and two demifacets on the heart-shaped body (except T10-T12, have only a single facet), the circular vertebral foramen, transverse processes, and a long spinous process (points sharply downward) The location of the articulate facets prevents flexion and extension, but allows rotation of this area of the spine

Thoracic Vertebrae With the exception of T11 and T12, the transverse process have facet that articulate with the tubercles of the ribs Figure 7.17b

Lumbar Vertebrae The five lumbar vertebrae (L1-L5) are located in the small of the back and have an enhanced weight-bearing function. This region receives the most stress They have short, thick pedicles and laminae, flat hatchet-shaped spinous processes, and a triangular-shaped vertebral foramen Orientation of articular facets locks the lumbar vertebrae together to provide stability

Lumbar Vertebrae Figure 7.17c

Sacrum (triangular) Sacrum Consists of five fused vertebrae (S1-S5), which shape the posterior wall of the pelvis It articulates with L5 superiorly, and laterally with the auricular surfaces of the two hip bones to form the sacroiliac joints of the pelvis Major markings include the sacral promontory, transverse lines, alae, dorsal sacral foramina, sacral canal, and sacral hiatus

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

Sacrum and Coccyx: Anterior View Figure 7.18a

Sacrum and Coccyx: Posterior View Figure 7.18b

Cervical (3-7) Thoracic Lumbar Body Spinous process Vertebral foramen Characteristics of Cervical,Thoracic and Lumbar Vertebrae (Table 7.2,and Fig, Pag 222) Characteristics Cervical (3-7) Thoracic Lumbar Body Small, wide side to side Larger than cervical, heart shaped, bears two costal demifacets Massive, kidney shaped Spinous process Short bifid, projects directly posteriorly Long, sharp, projects inferiorly Short, blunt, projects directly posteriorly Vertebral foramen Triangular Circular Transverse process Contain foramina Bear facets for ribs (except T11-T12) Thin and tapered Sup. and inf. art. process Sup facet→ sup-pos Inf facet → inf-ant Sup facets→ posterior Inf. facets → anterior Sup facet→ posmed Inf. facet → ant-lat Movements Flex and extension, lateral flex, rotation Rotation, limited lateral flex (ribs), flex & ext prevented Flex and ext, some lat flexion, rotation prevented

Homeostatic Imbalance Herniated (prolapsed) disc. Severe or sudden physical trauma to the spine, may result in hernation of one or more discs. A herniated disc (slipped disc) usually involves rupture of the annulus fibrosus followed by protrusion of the spongy nucleus pulposus through the annulus (Fig 7.14). If the protrusion presses on the spinal cord or on spinal nerves exiting from the cord, numbness or excruciating pay result. Treatments: moderated exercise, massage, heat ther. and painkillers if this fail→ surgery

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

All ribs attach posteriorly to the thoracic vertebrae There are twelve pair of ribs forming the flaring sides of the thoracic cage All ribs attach posteriorly to the thoracic vertebrae The superior 7 pair (true, or vertebrosternal ribs) attach directly to the sternum via costal cartilages Ribs 8-10 (false, or vertebrocondral ribs) attach indirectly to the sternum via costal cartilage 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

Appendicular Skeleton Although the bones of upper and lower limbs differ in their functions and mobility, they have the same fundamental plan: each limb is composed of three major segments connected by movable joints. The appendicular skeleton is made up of the bones of the limbs and their girdles Pectoral girdles attach the upper limbs to the body trunk Pelvic girdle secures the lower limbs

Pectoral Girdles (Shoulder Girdles) The pectoral girdles consist of the anterior clavicles and the posterior scapulae They attach the upper limbs to the axial skeleton in a manner that allows for maximum movement They provide attachment points for muscles that move the upper limbs

Pectoral Girdles (Shoulder Girdles) Figure 7.22a

Clavicles (Collarbones) “ Little keys” The clavicles are slender, doubly curved long bones lying across the superior thorax The acromial (lateral) end articulates with the scapula, and the sternal (medial) end articulates with the sternum They provide attachment points for numerous muscles, and act as braces to hold the scapulae and arms out laterally away from the body

Clavicles (Collarbones) Each clavicle is cone shaped at its medial sternal end, which attaches to the sternal manubrium, and flattened at its lateral acromail end in which articulate with scapula Figure 7.22b, c

Scapulae (Shoulder Blades) The scapulae are thin triangular, flat bones lying on the dorsal surface of the rib cage, between the second and seventh ribs Scapulae have three borders and three angles: 1.- superior (shortest, sharpest), 2.- medial (borders parallels to the vertebra col, 3.- lateral or axillary (were articulates with humerus) Major markings include the suprascapular notch, the supraspinous and infraspinous fossae, the spine, the acromion, and the coracoid process

Scapulae (Shoulder Blades) Figure 7.22d, e