thoracic wall Flashcards
features of the sternum
manubrium: T2-T4 ( suprasternal/jugular notch & facets for clavicle and first costal cartilages)
body: T5-T8 ( facets for 2nd-7th costal cartilages)
xiphoid process: T9
ribs
12 pairs.
1-7: connected anteriorly to the lateral side of the sternum through their costal cartilages and are TRUE ribs.
8-10: joined to each other and have no direct connection the the sternum (FALSE) ribs
11-12: are floating ribs as they have no connection to the sternum or any other ribs.
Atypical/typical ribs
3-9 are typical ribs:
- two ends: anterior (sternal) & posterior (vertebral).
- head: two facets
- neck
- tubercle
- shaft with costal groove.
1, 2, 10, 11 &12 are atypical (have special features).
1: wide & short, has 2 costal grooves & 1 articular facet.
2: thin, long & has a tuberosity on its superior surface.
10:only has 1 articular facet.
11 & 12: have only one articular facet with no neck.
Thoracic vertebrae
Located: inferior to the cervical vertebrae & superior to the lumbar vertebrae ( middle section of the vertebral column).
Separated by intervertebral discs of fibrocartilage that allow movement in the spine.
There are 12 thoracic vertebrae (T1-T12) in adult humans. Each vertebrae has a corresponding rib attached to it. T2-T8 are typical vertebrae, the rest (1st and last four) are atypical.
Parts of the thoracic vertebrae:
- body
- spinous process
- costal facets: transverse costal facet, superior costal facet and inferior costal facet.
- transverse process
- superior & inferior articular facets
- lamina
- intervertebral foramen
- vertebral foramen.
Muscles of the thoracic cage (intercostal spaces)
5 muscles that make up the thoracic cage:
- the intercostal muscles ( external, internal and innermost)
- the subcostalis muscles
- the transversus thoracis.
the muscles act to change the volume of the thoracic cavity during respiration.
some other muscles that attach to the thoracic wall:
- pectoralis major & minor
- serratus anterior & the scalene muscle.
Elevation of ribs by external intercostal muscle (inspiration)
Depression of the ribs by internal intercostal and other muscles (expiration).
Levatores costarum: 12 pairs, triangular in shap & insert into the rib below.
Serratus posterior muscles: thin, flat muscles that compromise the intermediate layer of muscles in the back.
Types of bones
ribs, manubrium and body of sternum are FLAT bones.
Vertebrae are IRREGULAR.
Clavicle is a long bone.
Thoracic joints
Sternal joints:
- manubriosternal joint (cartilaginous joint) between the manubrium and body of the sternum.
- xiphisternal joint (cartilaginous joint) between the xiphoid process and body of the sternum.
Joints of heads of ribs:
- 1st rib & 3 lowest ribs have a single synovial joint with their corresponding vertebral body.
- 2nd to 9th ribs the head articulates by a synovial joint with the corresponding vertebrae and the one above it.
Joints of tubercles of ribs:
-the tubercle of a rib articulates by a synovial joint with the transverse process of the corresponding vertebra (except on the 11th and 12th ribs).
Joints of costal cartilages:
articulate between the ribs and their costal cartilages (cartilaginous) no movement is possible here.
Joints of costal cartilages with sternum:
- 1st costal cartilages articulate with the manubrium by cartilaginous joints that do not permit movement.
- 2nd to 7th costal cartilages articulate with the lateral border of the sternum by synovial joints
- 6th to 10th articulate with one another along their borders by small synovial joints.
Injury in the thorax
Thoracic cage distortion: the shape of the thorax can be distorted by congenital anomalies of the vertebral column or by the ribs.
Traumatic injury to the thorax: common, especially as a result of automobile accidents.
Rib contusion: bruising of a rib, after trauma, is the most common rib injury.
Rib fractures: common chest injuries. (Rare in children as ribs are highly elastic). Ribs tend to break at their angles (weakest part). Ribs 5-10 are the most commonly fractured ribs.
Arteries of the thoracic wall
- Internal Thoracic artery:
- supplies anterior wall of the body from clavicle to umbilicus.
- branch of the 1st part of the subclavian artery in the neck.
- descends vertically behind the costal cartilages and ends in in 6th intercostal space by dividing into superior epigastric and musculophrenic arteries.
Veins of the thoracic wall
Internal thoracic vein:
-accompanies the internal thoracic artery and drains into the brachiocephalic vein on each side.
Posterior intercostal veins:
-drain into the azygos or hemiazygos veins.
Anterior intercostal veins:
-drain anteriorly into the internal thoracic and musculophrenic veins.
Nerve supply of thoracic wall
Through intercostal nerves. (Supply whole thoracic wall).
-anterior rami of the first 11 thoracic spinal nerves.
-each intercostal nerve enters an intercostal space between the parietal pleura of the lung and the posterior intercostal membrane.
Then runs inferiorly to the intercostal vessels in the subcostal groove of the corresponding rib (between the innermost and internal intercostal muscles).
Thoracic openings
Superior thoracic aperture/ thoracic outlet:
- narrow opening
- outlet as important vessels emerge from the thorax here to enter the neck & upper limb.
- suprapleural membrane: dense fascial layer that closes the thoracic outlet on either side of the structures.
Inferior thoracic aperture:
-large opening that allows the thoracic cavity to communicate with the abdomen.
Endothoracic fascia: thin layer of loose connective tissues that separates the parietal pleura from the thoracic wall.
Intercostal spaces: gaps between adjacent ribs
(7 layers): skin, superficial fascia, deep fascia, intercostal muscles, endothoracic fascia, extrapleural fatty layer, parietal pleura.
Diaphragm
Thin muscular and tendinous septum that separates the chest cavity from the abdominal cavity.
Curves up into right and left domes (cupulae).
MOST important muscle of respiration.
Origin:
-sternal: back of xiphoid process
-costal: lower 6 ribs & costal cartilages
-vertebral:
2 cura:
-right crus: first 3 lumbar vertebrae & intervertebral discs
-left crus: first 2 lumbar vertebrae & intervertebral discs
3 arcuate ligaments:
- median: between the 2 crura
- medial:between each crus and L1 transverse process
- lateral: between L1 transverse process & last rib.
Insertion: central tendon.
Nerve supply:
- motor: left and right phrenic nerves
- sensory nerve supply: phrenic nerves covering central surfaces. Lower 6 intercostal nerves supply periphery.
Action & function.
Pulls down during contraction.
Flattens during contraction (inspiration)
Elevates during relaxation (expiration)
4 main functions:
- muscle of inspiration
- muscle of abdominal straining
- weight lifting muscle
- thoracoabdominal pump
Diaphragm openings:
- aortic opening
- esophageal opening
- vena caval opening.
lymphatic drainage
Internal thoracic lymph nodes:
- along internal thoracic artery
- lymph received from medial portion of breast, intercostal spaces & diaphragm.
Intercostal lymph nodes:
- near head of ribs
- receive lymph from intercostal spaces & pleura
- drain into cisterna Chyli or thoracic duct
Diaphragmatic (prhrenic) nodes:
- lie on thoracic surface of diaphragm & liver
- receive lymph from pericardium, diaphragm & liver.
- drain into sternal & posterior mediastinal nodes.
