Thorax Flashcards
Thoracic cage
The bony framework of the chest
Structure of the thoracic cage
Thoracic vertebrae posteriorly, ribs laterally, and sternum + costal cartilages anteriorly
Function of the thoracic cage
A bony cage that protects the thoracic viscera, supports the shoulder girdle and upper limb, and provides attachments for many upper body muscles
What does the thoracic cage house?
The intercostal muscles that elevate and depress the thorax during respiration
What three parts of the somites divided into?
Sclerotome
Dermatome
Myotome
Sclerotome “Hard piece”
Cells migrate medially, gather around the notochord and neural tube, which then become the vertebrae and ribs
Dermatome “Skin piece”
Cells migrate to more superficial layers and become the dermis of the skin on the dorsum of the body
Mytome “Muscle piece”
Remaining cells that form the trunk and limb musculature
What are the 5 major vertebral regions?
Cervical
Thoracic
Lumbar
Sacrum
Coccyx
Cervical
7 vertebrae of neck
Thoracic
12 vertebrae of thorax
Lumbar
5 vertebrae of lower back
Sacrum
5 fused vertebral segments; articulate with hip bones
Coccyx
4 fused segments
Sternum
A flat bone formed from 3 sections
Manubrium
Superior section
- Articulates with the medial ends of the clavicles
- Also articulates with ribs 1 and 2
Body
Middle portion
- Sides are notched at articulations for the costal cartilages of ribs 2-7
Xiphoid process
Inferior end of sternum
- a plate of hyaline cartilage
- fully ossifies around age 40
What are the 3 anatomical landmarks of the sternum?
Jugular notch (suprasternal notch)
Sternal angle
Xiphisternal joint (deep to this joint, the heart lies on the diaphragm)
Sternal angle
- Easily accessible clinical landmark: lies anterior to arch of aorta, marks the start and end of aortic arch
- Anterior to carina (bifurcation of trachea)
Corresponds to IV disc b/n T4 and T5 vertebra - Marks inferior boundary of superior mediastinum
How do all 12 pairs of ribs attach to the thoracic vertebrae?
Posteriorly
True ribs
Superior seven pairs
- attach directly to the sternum by costal cartilages
False Ribs
Inferior five pairs (8-12)
- Attach to the sternum either indirectly or not at all
Floating Ribs
Have no anterior attachments, embedded in the muscles of the lateral body wall (ribs 11-12)
What is the structure/definition of a typical rib?
Head: Articulates with the vertebral bodies by two facets
Tubercle: Articulates with the transverse process of the thoracic vertebra of the same number
Shaft: The bulk of the rib
Costal groove: Located on the inferior border; houses the intercostal. nerves and vessels
Thoracic cavity communicates with neck and upper limb through what?
Thoracic Inlet
Thoracic Inlet
Passage of trachea, esophagus, vessels, and nerves
Thoracic Outlet
Esophagus and aorta
Intercostal space
An intercostal vein, artery, and nerve travel in the costal groove on the inferior surface of a rib, between the internal and innermost intercostal muscles
What branches from the thoracic aorta?
Posterior intercostal arteries and subcostal artery
What comes from the internal thoracic artery?
Anterior intercostal arteries
What comes from the subclavian artery
Internal thoracic artery
The right side of the intercostal veins drain into…
Azygous vein to the superior vena cava (SVC)
The right side of the intercostal veins drain into…
Accessory hemiazygos and hemiazygos veins that drain into the azygos vein
How many thoracic spinal nerves?
12 pairs
What forms the intercostal nerves?
Anterior (ventral) rami of T1-T11
What forms the subcostal nerves?
Anterior rami of T12 nerves
Posterior (dorsal) rami of thoracic spinal nerves supply…
Bones, joints, deep back muscles, and skin of the back in the thoracic region
Diaphragm
The most important muscle of respiration
- Flattens as it contracts, increases the volume of the thoracic cavity
