Vertebral Column

Vertebral Column

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Vertebral Column...

Vertebral Column:

DIVISIONS AND STRUCTURES OF THE VERTEBRAL COLUMN

The vertebral column consists of 26 vertebrae separated by intervertebral disks. Four curves add strength and resilience to the column. All vertebrae have a common structural pattern although there may be some variations between them.

The divisions are as follows:

1. cervical vertebrae: (7) designated C1-C7. The first two cervical vertebrae are greatly modified and there is no disk between them. The first cervical vertebrae is known as the atlas. It has no body and no spinous process. It is essentially a ring with large facets that articulate with the occipital bone. The axis or C2 has an odontoid process that projects upward from the vertebral body like a tooth. This acts as a pivot joint for rotation of the head. The atlas holds the skull up and permits you to nod “yes”. The axis allows you to rotate and to shake your head side to side to say “no”.

2. thoracic vertebrae: (12) designated T1-T12. The thoracic vertebrae have facets on the transverse processes, for articulation with the ribs. The 12 pairs of ribs, the sternum and the thoracic vertebrae form the bony cage known as the thorax or chest. Each of the 12 pairs of ribs is attached posteriorly to a vertebra. Also, all the ribs except the lower two pairs are attached to the sternum. The first 7 pairs of ribs are attached to the sternum and they are called true ribs. The eighth, ninth, and tenth pairs are attached to the cartilage of the seventh ribs. These are sometimes called false ribs. The last two pairs of ribs are not attached to any costal cartilage but seem to float free in front, this is why they are referred to as floating ribs.

3. lumbar vertebrae: designated L1-L5. These make up the small of the back.

4. sacrum: This is a triangular bone just below the lumbar vertebrae. In the child there are five separate bones but these fuse to form a single bone in the adult. The sacrum articulates with the pelvic girdle laterally, at the sacroiliac joint, and forms the posterior wall of the pelvic cavity.

5. coccyx: This is also called the tail bone and it is the last part of the vertebral column. There are 3-5 coccygeal bones that fuse together to form a single bone in the adult.

APPENDICULAR SKELETON

There are 126 bones of the appendicular skeleton. The bones in the shoulder or pectoral girdle connect the bones of the arm, forearm, wrist and hands to the axial skeleton of the thorax. The hip or the pelvic girdle connects the bones of the thigh, leg, ankle and foot to the axial skeleton of the pelvis. The appendicular skeleton is designed for movement. If a portion is immobilized for a period of time, you can realize how awkward life may be without appendicular movement.

PECTORAL GIRDLE

Each half of the pectoral or shoulder girdle consists of 2 bones: an anterior clavicle and a posterior scapula. The term girdle means something that encircles or a complete ring. Anteriorly, the bones are separated by the sternum. Posteriorly, there is a gap because they do not articulate with each other or with the vertebral column. The bones of the pectoral girdle form the connection between the upper extremities and the axial skeleton.

The clavicle is commonly called the collarbone and the scapula is commonly called the shoulder blade. The lateral end of the scapula has a spine that broadens to form a common landmark known to medical assistants as the acromion process. There is a connection to the sternum with the clavicle called the sternoclavicular joint. This joint is very small and because the upper extremity is capable of a wide range of motion, great pressures can occur at or near the joint. As a result, fractures of the clavicle are very common.

UPPER EXTREMITIES

HUMERUS- is the long bone of the upper arm and the second largest bone in the body.

RADIUS- is a long bone of the forearm that runs on the thumb side or the lateral side of the forearm.

ULNA- is a long bone of the forearm and is on the medial side of the forearm. See page 147. The large bony process of the ulna is the olecranon process or as you may call it the funny bone.

The wrist and the hand have more bones in them for their size than any other part of the body.

CARPALS OR WRIST BONES- there are 8 carpal or wrist bones in each wrist for a total of 16 bones.

METACARPALS- there are 5 metacarpals for each hand. The metacarpals form the support structure for the palm of the hand.

PHALANGES- there are 14 phalanges or finger bones in each hand.

The composition of the bones in the hand is very important structurally. The presence of many small bones in the hand and the wrist along with many joints, make this extremity highly maneuverable.

LOWER EXTREMITIES

HIP OR PELVIC GIRDLE- connects the legs to the trunk. It also provides a strong support system and protection for the urinary bladder, a portion of the large intestine, and the internal reproductive organs which are located in the pelvic cavity.

The pelvic girdle consists of two coxal or hip bones. These two bones, with the sacrum and coccyx behind, provide a strong base of support for the torso. In an infant’s body each coxal bone consists of 3 separate bones; the ilium, the ischium and the symphyis pubis. These bones fuse together to become one bone in an adult.

The female pelvis is shaped to accommodate childbearing. Since the fetus must pass through the pelvic outlet, the physician must carefully measure this opening to make sure there is enough room. If the opening is too small a C-section will be performed.

FEMUR- is a long bone in the thigh. It is the longest bone in the body and articulates with the coxal bone in a deep cup shaped socket called the acetabulum. Distally, the femur articulates with the knee cap or the patella and the tibia. Elderly people, particularly, those with osteoporosis, are susceptible to “breaking a hip”. The femur is a weight bearing bone and when it is weakened, it cannot support the weight of the body and the neck of the femur fractures under the stress. Instead of saying,

“Grandma fell and broke her hip,” many times it is more appropriate to say,

“Grandma broke her hip and fell”.

PATELLA- is an example of a sesamoid bone. It helps to protect the articulating surfaces of the upper and lower legs.

FIBULA- is a slender non-weight bearing bone on the lateral side of the lower leg. This is also a long bone. The lateral malleolus is the rounded projection at the lower end of the fibula commonly called the outer anklebone. Skiers frequently fracture the distal part of the fibula as a result of a twisting, or shearing, force near the ankle. This is called a Pott’s fracture. Sometimes, the force is sufficient to fracture the medial malleolus at the same time.

TIBIA- is also called the shinbone. The tibia forms a sharp edge or crest along the front of the lower leg.

TARSALS- form the heel and the back part of the foot. The largest of the tarsal bones is the calcaneus. There are 7 tarsal bones in each foot. These correspond to the carpals in the wrist. The talus rests on top of the calcaneus and articulates with the tibia.

METATARSALS- form the part of the foot to which the toes attach. There are 5 metatarsal bones in each foot. These bones are not named and are numbered one through five starting on the medial side.

PHALANGES- are the toe bones. There are 14 in each foot. The proximal phalanges articulate with the metatarsals. There are 3 in each toe except for the great or the big toe, where there is two.