Anatomy: Thoracic Spine

Where is the thoracic spine located

- the middle section of the spine- it starts at the base of the neck and ends at the bottom of the ribs- it is the longest section of the spine

What does the thoracic spine consist of

12 vertebrae labaled T1-T12

The thoracic vertebrae, as a group produce

a kyphotic curve (concave anteriorly as viewed from the side)

thoracic spine protect

the spinal cord and branching spinal nerves

thoracic spine provides attachment for

the ribs

how does the thoracic spine allow movement of the body

The soft intervertebral disks between the vertebrae make it possible to twist and bend without sacrificing the supportive strength of the vertebral column

thoracic spine supports

the chest and abdomen

The thoracic spine helps stabilize

the rib cage

The thoracic spine and ribcage protect

heart and lungs

The joints in the thoracic spine are

tight enough to protect these vital organs but loose enough to allow for the movements of breathing — inhaling and exhaling

Thoracic facets

- inferior face: anterior, inferior, and medial & are best in side-bending- superior face: posterior, superior, and lateral

The atypical thoracic vertebrae display

variation in the size, location, and a number of their superior and inferior costal facets

Atypical vertebrae: T1

Superior facet is not a demifacet, as this is the only vertebrae to articulate with the 1st rib

atypical vertebrae: T10

A single pair of whole facets is present which articulate with the 10th rib. These facets are located across both the vertebral body and the pedicle.

atypical vertebrae: T11 and T12

Each has a single pair of entire costal facets, which are located on the pedicles

The superior and inferior costal facets are located...

on the sides of each vertebral body

what do the superior and inferior costal facets consist of

cartilage-lined depressions, which articulate with the heads of the ribs

The superior facet articulates with...

the head of the adjacent rib, and the inferior facet articulates with the head of the rib below

In the majority of the vertebrae (T2-T9) these facets are

demi-facets

Are there some atypical vertebrae that posses whole facets?

yes

Where are demifacets

articulation with ribs

what shape is the vertebral body

heart shaped

how are prominent spinous processes angled

following "rules of 3

Rule of 3s

- Spinous process of T1-T3 even with transverse process of same level vertebra- T4-T6 spinous processes are found one half level below transverse processes of same level- T7-T9 spinous processes are one full level below transverse process of same level- T10 is full level below- T11 is one half level below- T12 is level

Joints common in the vertebrae

- facet joints- intervertebral disks

facet joints

These spinal joints have cartilage (a slippery connective tissue) that allows vertebrae to slide against each other. Facet joints let you twist and turn, and they provide flexibility and stability

intervertebral disks

These flat, round cushions sit between the vertebrae and act as the spine's shock absorbers. Each disk has a soft, gel-like center surrounded by a flexible outer ring

Joints unique to the thoracic spine

- costovertebral and costotransverse

Costovertebral joint consists of

the head of the rib

Costovertebral joint consists of the head of the rib articulating with

•Superior costal facet of the corresponding vertebra•Inferior costal facet of the superior vertebra•Intervertebral disc separating the two vertebrae•The intra-articular ligament of the head of the rib attaches the rib head to the intervertebral disc.•Only slight gliding movements can occur at these joints

Costotransverse joints are formed by

- the articulation of transverse processes of a thoracic vertebra and the tubercle of the adjacent rib.-- They are present in all vertebrae except T11 and T12.

where do costotransverse and costovertebral joints have articulations between

rib and transverse process and vertebral body respectively

thoracic cage (rib cage) consists of

•12 thoracic vertebrae•12 pairs of ribs•Associated costal cartilages•Sternum

The main functions of the thoracic cage

•support thorax and protect the vital structures•Attachment point for many muscles•Support the weight of the upper limbs•Breathing

rib cage joints

- xiphisternal- intervertebral- sternochondral- sternoclavicular- manubriosternal- costochondral- costovertebral- interchondral

Xiphisternal joint

xiphoid process and body of sternum

Intervertebral joint

between the vertebrae

Sternochondral joint

sternum and costal cartilages

Sternoclavicular joint

manubrium and clavicles

Manubriosternal

manubrium and body of sternum

Costochondral joint

costal cartilage and rib

Costovertebral joint

formed by the ribs and bodies of the vertebrae

Interchondral joint

joining the costal cartilages to one another

what kind of bones are the ribs

long, flat bones that enclose most of the thoracic cage

Anteriorly, the ribs are

elongated with their costal cartilages which then connect with the sternum

The first seven (and sometimes the 8th) cartilages attach

directly and independently to the sternum

The 8th, 9th, and 10th cartilages articulate with

the costal cartilages

•According to their structure, the ribs can be divided into

- Typical and atypical (1st, 2nd, 10th-12th).- True/False/Floating: the top seven pairs connect to your sternum. These are known as "true ribs" The next three pairs of ribs are known as "false ribs". Ribs 11 and 12 are floating ribs

The sternocostal (Sterno-chondral) joints are formed by

the lateral borders of the sternum and the costal cartilages of- the 1st to 7th ribs, and sometimes the 8th rib

The first pair of costal cartilages articulate with

the manubrium by means of a thin dense layer of tightly adherent fibrocartilage interposed between cartilage and the manubrium, the synchondrosis of the first rib

The second to seventh pairs of costal cartilages articulate with

the sternum at synovial joints with fibrocartilaginous articular surfaces on both the chondral and sternal aspects, allowing movement during respiration

where are intercostal spaces

the spaces between the ribs

what do intercostal spaces separate

the ribs and their costal cartilages from one another and allow smooth expansion of the cage during inspiration

how many intercostal spaces are there

There are 11 intercostal spaces, and each space is named according to the rib which is the superior border of the space.-- For example, the 6th intercostal space is located between the 6th and 7th rib.

Intercostal spaces are mainly occupied by

intercostal muscles and membranes

what do intercostal spaces also contain

11 intercostal nerves and intercostal blood vessels

The space inferior to the 12th rib is referred to as

the subcostal space

The subcostal space hosts the

anterior ramus of the spinal nerve T12 runs through this space, and it is thus referred to as the subcostal

The sternum consists of three distinct bony parts

•The manubrium•The body of the sternum•The xiphoid process

The manubrium is the

superior part of the sternum

•The manubrium forms articulations with

•The clavicle (sternoclavicular joint)•Body of the sternum (manubriosternal joint)•First rib and superior half of the second rib (sternocostal joints)

The body of the sternum extends from

•the manubrium to the xiphoid process (at the level of vertebrae T5-T9)

Superiorly the sternum-body articulates with

the manubrium and forms the manubriosternal joint and an anterior projection called the sternal angle (of Louis)

The sternal body bilaterally articulates with

six ribs (2nd to 7th rib) on its lateral borders

Inferiorly the body articulates with

the xiphoid process and forms the xiphisternal joint

The xiphoid process is the

smallest and most inferior portion of the sternum

where is the xiphoid process positioned at

the level of the T10 vertebra

The xiphoid process is part of the

inferior margin of the thoracic cavity and marks the infra-sternal angle (subcostal angle) of the inferior thoracic aperture

muscles of the thorax (movers of the ribs)

- levatores costarum- serratus posterior inferior- subcostales- innermost intercostals- internal intercostals- transversus thoracis

muscles of the anterior abdominal wall

- external oblique- internal oblique- rectus abdominis- transversus abdominis

The joint capsule resembles

a sac-like envelope that forms a sleeve around the synovial joint and encloses its cavity

how many layers does the joint capsule consist of

- 2- fibrous layer (outer)- synovial layer (inner)

Fibrous layer (outer)

- Consists of white fibrous tissue, the capsular ligament.- It holds together the articulating bones and supports the underlying synovium

Synovial layer (inner)

- Highly vascularized layer of serous connective tissue.- It absorbs and secretes synovial fluid.- it mediates nutrient exchange between blood and joint- Also known as the synovium

ligaments present throughout vertebral column

- Anterior and posterior longitudinal ligaments- Ligamentum flavum- Interspinous ligament- Supraspinous ligament

Anterior and posterior longitudinal ligaments

long ligaments that run the length of the vertebral column, covering the vertebral bodies and intervertebral discs.

ligamentum flavum

connects the laminae of adjacent vertebrae

interspinous ligament

connects the spinous processes of adjacent vertebrae

supraspinous ligament

connects the tips of adjacent spinous processes

Ligaments that support the costovertebral joints

- Radiate ligament of head of the rib- costotransverse ligament- Lateral costotransverse ligament- Superior costotransverse ligament

Radiate ligament of head of the rib

Fans outwards from the head of the rib to the bodies of the two vertebrae and intervertebral disc

Costotransverse ligament

Connects the neck of the rib and the transverse process

Lateral costotransverse ligament

Extends from the transverse process to the tubercle of the rib

Superior costotransverse ligament

Passes from the upper border of the neck of the rib to the transverse process of the vertebra superior to it

An intervertebral disc lies between

adjacent vertebrae in the vertebral column

Each disc forms

a fibrocartilaginous joint (a symphysis)

disc functions

- Allow slight movement of the vertebrae.- Acts as a ligament to hold the vertebrae together.- Functions as a shock absorber for the spine

Thoracic Disc Syndrome

Intervertebral disc degeneration primarily causes thoracic discogenic pain syndrome

causes of thoracic disc syndrome

- Trauma- Metabolic abnormalities- Genetic predisposition- Vascular problems- infections

Common conditions and disorders that affect the thoracic spine

- Kyphosis- Scoliosis- Thoracic radiculopathy- Bone spurs (osteophytes)- Herniated disk- Myelopathy- Osteomyelitis- Spinal cord injury- Spinal stenosis- Vertebral compression fractures (VCFs) are the most common injury to the thoracic spine

The spinal cord runs throughout the

thoracic spine and transmits nerve roots beneath the pedicles of the named vertebrae- for example, the T10 nerve roots exit beneath the pedicle of the T10 vertebra

The T1 nerves supply sensation of

the ulnar forearm and T2 supplies the axilla

T1 motor innervation is associated with

interosseous muscle function in the hands

Successive thoracic dermatomes supply the

trunk with the T4 dermatome associated with the region of the nipples, T7 at the inferior aspect of the sternum, and T10 at the level of the umbilicus

The superficial abdominal reflex is controlled by

the distal thoracic nerve roots from T7 to T12