the skeleton part c

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Human Anatomy & Physiology, Sixth EditionElaine N. Marieb

PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky

7The Skeleton

Part C


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

Table 7.2

Movement’s allowed:

Flexion and extension

Rotation (greatest range of movement)


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

Figure 7.17a

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”


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

Figure 7.17b

With the exception of T11 and T12, the transverse process have facet that articulate with the tubercles of the ribs


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

Sacrum (triangular)

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

Coccyx (Tailbone)

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


Characteristics of Cervical,Thoracic and Lumbar Vertebrae (Table 7.2,and Fig, Pag 222)Characteristics Cervical (3-7) Thoracic LumbarBody Small, wide side to

sideLarger 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 Triangular

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



Figure 7.19a



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

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)

Figure 7.22b, c

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


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

the skeleton part c

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