The Axial Skeleton - The Spine & The Thoracic Cage

spine

the spine supports the upper body's weight, provides posture while allowing for movement and flexibility, and protects the spinal cord

function of the thoracic curve

the thoracic curve, a primary curve, provides room for the thoracic organs

true ribs

ribs that are attached directly to the breastbone

atlas

the atlas forms the joint connecting the skull and spine and allows a greater range of motion than normal vertebrae

axis

the axis allows the skull and atlas to rotate to the left and right

function of the cervical curve

the cervical curve, a secondary curve, develops as the infant learns to balance the weight of its head on the vertebrae of the neck

function of the sacral curve

the sacral curve, a primary curve, provides room for various abdominopelvic organs

What are the 4 spinal curves?

-cervical curve -thoracic curve -lumbar curve -sacral curve

What is lordosis?

In lordosis, or "swayback," both the abdomen and buttocks protrude abnormally. This causes an anterior exaggeration of the lumbar curvature. This may occur during pregnancy or result from abdominal obesity or abdominal wall muscle weakness.

What is kyphosis?

Kyphosis is an abnormal posterior exaggeration of the thoracic curvature, producing a "round-back" appearance. This condition can be caused by osteoporosis with compression fractures affecting the anterior portions of vertebral bodies, chronic contractions in muscles that insert on the vertebrae, or abnormal vertebral growth.

What is scoliosis?

Scoliosis is an abnormal lateral curvature of the spine in one or more of the movable vertebrae. Scoliosis is the most common spinal curvature abnormality. This condition may result from damage to vertebral bodies during development, or from muscular paralysis affecting one side of the back. In many cases, the cause of abnormal spinal curvatures is not known.

thoracic vertebrae

The 12 vertebrae in the chest region form the spine's thoracic region. Thoracic vertebrae are larger and stronger than cervical vertebrae but are much less flexible. The spinous processes of the thoracic vertebrae point inferiorly to help lock the vertebrae together. A unique feature of the thoracic vertebrae is that each one forms joints with a pair of ribs to form the sturdy rib cage that protects the organs of the chest.

lumbar vertebrae

The 5 vertebrae in the lower back form the lumbar region of the spine. Lumbar vertebrae are even larger and stronger than thoracic vertebrae but are more flexible due to the lack of ribs in the lumbar region. All of the upper body's weight bears down on the lumbar vertebrae, leading to many back problems in this region despite the size and strength of the vertebrae.

cervical vertebrae

The 7 vertebrae in the neck form the cervical region of the spine. Cervical vertebrae are the thinnest and most delicate vertebrae in the spine but offer great flexibility to the neck. The first cervical vertebra, C1, supports the skull and is named "atlas" after the Greek titan who held the Earth on his shoulders. The skull pivots on the atlas when moving up and down. The second cervical vertebra, C2, is also known as the "axis" because it allows the skull and atlas to rotate to the left and right.

false ribs

The false ribs include both vertebrochondral ribs and vertebral ribs. There are three pairs of vertebrochondral ribs (eighth to tenth) that connect indirectly to the sternum via the costal cartilages of the ribs above them. Their elasticity allows rib cage movement for respiratory activity.

function of the lumbar curve

The lumbar curve, a secondary curve, balances the weight of the trunk over the lower limbs. This curve develops with the ability to stand.

What curves are primary and why are they called primary curves?

The primary curves are the thoracic curves and the sacral curves. They are called primary because they appear in fetal development.

ribs

The ribs are a set of twelve paired bones that form the protective 'cage' of the thorax. They articulate with the vertebral column posteriorly and terminate anteriorly as cartilage (known as costal cartilage). As part of the bony thorax, the ribs protect the internal thoracic organs.

sacrum

The sacral region of the spine contains only the sacrum, a single bone in the adult skeleton that is formed by the fusion of 5 smaller vertebrae during adolescence. The sacrum is a flat, triangular bone found in the lower back and wedged between the 2 hip bones.

What curves are secondary and why are the called secondary curves?

The secondary curves are the cervical curves and the lumbar curves. They are called secondary because they appear several months after birth.

coccyx

The spine's coccygeal region contains only the coccyx, a single bone in the adult skeleton that is formed by the fusion of 4 tiny vertebrae during adolescence. The coccyx is often referred to as the human tailbone, as this region is homologous to the tail bones of animals that have tails. In humans, the coccyx bears our body weight when sitting down and provides attachment points for muscles of the pelvic and gluteal regions. While most people have a coccyx made of 4 fused vertebrae, the coccyx may consist of as few as 3 or as many as 5 vertebrae. The length of the coccyx has no effect on the body's function.

sternum

The sternum is a bone that's located in the middle of the chest. It's also sometimes referred to as the breastbone. The sternum protects the organs of the torso from injury and also serves as a connection point for other bones and muscles.