S1M3 Thoracic Wall Anatomy
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What are the thoracic cavity openings?
What is the clinically relevant opening called and where is it located
- Two openings: throacic inlet (Superior to the manurium) and thoracic outlet(inferior, continuous with the abdominal cavity)
- Clinically we refer to the the thoracic outlet as the superior opening because there are several structures exiting to the upper limbs, (median and ulnar nerve) subclavian vessels.
What are the compartments of the throax?
- 1. Central compartment (mediastinum)
- 2. Right lateral compartment (right
- pleural cavity
- 3. Left lateral compartment (left pleural
What are the functions of the Thoracic Dome?
- 1-Protect vital thoracic & abdominal
- internal organs
- 2-Resists negative internal pressures
- generated by the elastic recoil of the lung
- 3-Provide attachment for & support
- the weight of the upper limb
- 4-Provide anchoring attachment for
- many muscles involved in moving the
- upper limb
What are the components of the Thoracic
- Skin Subcutaneous tissue -Fascia Muscles (except pectoralis muscles)
- Bones (ribs, sternum, manubrium) Cartilage(costal cartilages)
How many ribs do you have in your thoracic wall?
12 throacic ribs AND 12 thoracic vertebrae (with associated costal cartilages)
The sternum consists of what specific parts? What is the sternal angle and what is it's clinical relevance?
- Manubrium (between 1st and 2nd costals) latin handle/ blade of sword
- Body of Sternum
- Xiphoid process**Manubrium is the widest and thickest part of the sternum-
- Very important: the manubrium and the body of the first rib lie in different planes superior and inferior to their junction, forming a Sternal Angle (of Louis)this is easy to palpate and locate the approximate location of the 2nd rib !!!
What is clinically relevavent regarding the sternal angle (or angle of Louie)?
- **The sternal angle (also know as the angle of Louie) is between the manubrium and the body of the sternum and it is clinically relevant because you can PALPATE the angle and definitively locate and mark the 2ND RIB for a procedure. It also marks about T4/T5 vertebrae
Clinical: What is pectus excavatum? What are the 3 causes?**
Don't Miss easy clinical questions.
- It is an anterior chest wall deformity characterized by a concave depression.Caused by:
- 1.) Intrauterine pressure on the chest wall during development
- 2.) Abnormal diaphragm positioning causing a posterior retraction
- 3.) Abnormal Connective Tissue production
Clinical: What is Pectus Carinatum? What are the 4 causes?
- Pt will present with a protrusion of the sternum and costal cartilages
- Caused by:
- 1.)Abnormal anterior cartilage growth
- 2.)Abnormal Sternal growth
- 3.)CT tissue disorders
- 4.)Associated conditions like scoliosis and congenital heart disease
The inferior end of the xiphoid process marks what level of vertebrae?
The xiphoid process is and important landmark clinically
- First: It's junction with the sternal body at the xiphisternal joint tells you where the inferior limit of the central part of the thoracic cavity projected onto the anterior body wall (This is where the infrasternal angle or subcostal angle is formed by the right and left costal margins--look at above picture--The RED triangle indicates where the left and right costal margins are located
- Second: It is a midline marker for the superior limit of the liver, the central tendon of the diaphragm and inferior border of the heart.
Clinical: What is Thoracic Outlet Syndrome (TOS)?
What nerves and arteries can be involved?
- This refers to the clinician's thoracic outlet: the arteries and T1 spinal nerves that emerge from the thorax through this superior aperature to enter the lower neck and limbs.
- TOS: these emerging structures are affected by obstructions of the superior thoracic aperature--can be compression of these structures--
- Typically manifestations of TOS involve the upper limb
- Ulnar N. Median N. and Subclavian vessels can be involved in TOS
What are the three types of ribs?
True, Fales and Floating
What is characteristic of a true rib? Which ribs are true?
- True (vertebrocostal) ribs (1st-7th ribs) are attached directly to the sternum through their OWN costal cartilage
What is characteristic of a false rib?
Which ribs are false?
False (vertebrochondral) ribs (8th, 9th, and usually the 10th)- their cartilages are connected to the cartilage of the rib above them; so their connection with the sternum is indirect.
What is characteristic of your floating ribs?
- Floating (vertebral, free) ribs (11th, 12th and sometimes the 10th ribs) have rudimentary cartilages that do not connect even indirectly with the sternum; instead they end in the posterior abdominal musculature.
What is unique about your 1st rib? (It's an atypical rib)
- 1st: broadest shortest most sharply curved-has a single facet on its head for articulation with T1 vertebra and two transvers grooves crossing its superior surface for the subclavian vessels.
Which ribs are atypical?
1st, 2nd, 10th-12th ribs
Typical ribs #s?
3-9th Ribs are TYPICAL.
What is unique regarding your 2nd rib?
- 2nd: is thinner, less curved body, much longer than the first rib- It's head has two facets (1st rib has only one for T1)
- Most Atypical Feature is a rough area on its upper surface, the tuberosity for serratus anterior, where the muscle originates
What is unique about the 10th-12th ribs?
They are like the first rib they have only one facet on their heads and articulate with a single vertebrae.
What is atypical about the 11th and 12th ribs?
They are short and have NO neck or tubercle.
What are the components of the typical ribs? (ribs 3-9) KNOW these components
- They have a head, neck, tubercle, body (curved at the costal angle) and a costal groove
What is clinically significant regarding the fracture of the first rib?
- The short, broad first rib, posteroinferior to the clavical, is rarely fractured because it is protected (it can't be palpated)
- When you fracture the first rib, damage can occur to the brachial plexus of nerves and subclavian vessels of the upper limb.
What is clinically significant regarding the middle ribs?
What part of the middle ribs are most commonly fractured?
- The middle ribs are most commonly fractured.
- Rib fx caused by blows or crushing injuries.
- weakest part of rib: just anterior to its angle (although direct violence can damage a rib anywhere)
- Damaged ribs can injure internal organs like the LUNG and SPLEEN.
- Rib Fx Suck because they are extremely painful because the broken parts move during respiration, coughing, laughing and sneezing
Fractures of the lower ribs can cause what?
Lower rib fxs can tear the diaphragm and result in diaphragmatic hernia (where abdominal contents move into the chest cavity)
Dislocation of Ribs ("slipping rib" syndrome) is what?
- The displacement of costal cartilage from the sternum---the dislocation of a sternocostal joint or the displacement of the interchondral joints.
- Common in body-contact sports
- Complications: pressure to nerves, vessels and muscles nearby
- If the trauma is severe enough to disslocate a rib, it often injures underlying structures like the liver or diaphagm (causes severe pain)
What is "Rib Separation"?
- It refers to the disslocation of costo-chondral junctions between the rib and its costal cartilage.
- In separations of the 3rd-10th ribs tearing of the perichondrium and periosteum usually occurs, as a result, the rib can move superiorly overriding the rib above and causing pain.
What is Supernumary Ribs?
Supernumerary Ribs can affect identification of vertebral levels in diagnositic imaging
- Normally we have 12 ribs on each side
- We may have extra cervical ribs which can affect the neurovascular structures exitign the superior thoracic aperature.
- Can also have lumbar ribs (less common)
Describe Sternal Fractures
- Not Common
- Occur in Crush Injuries
- Typically Comminuted Fracture (Sternum broken into many pieces)
Think of persons chest being forced against the steering column during an accident!
Displacement of bone fragments is uncommon
due to the deep fascia
What is the most common fracture location on the sternum?
The sternal angle!
What is a Median Sternotomy?
- To gain access to the thoracic cavity for surgical operations in the mediastinum (for coronary artery bypass grafting) the sternum is divided in the median plane and retracted.
- What allows this? The flexibility if the ribs and costal cartilages!
- This splitting also gives foor access for removing tumors in the superior lobes of the lungs.
- After surgery- two halves of the sternum are joined by wire sutures.
What is the purpose of a Sternal Biopsy?
- The body of the sternum is often used for bone marrow needle biopsy because of its breadth and sub-q position (so close to the skin)
- The needle pierces the thin cortical boen and enters the vascular spongy bone
- Sternal biopsy is commonly used for detection of metastatic cancer and blood dyscrasias (abnormalities)
There are several joints of the chest wall, what is the clinical significance if any of these joints are disturbed?
**During normal respiration the range of movement of these joints is small, but if any of them are distrubed it reduces the mobility of the joint and interferes with respiration
- Costovertebral joints
- -Sternoclavicular joints
- -Manubriosternal symphysis
- -Costochondral joints
- -Chondrosternal joints
- -Xiphisternal joint
*Clinical: What is Ankylosing Spondylitis?
- Chronic inflammatory disease affecting the joints of the axial skeletonLimits spinal range of motion, causes exercise intolerance sometimes
- Leads to bone protuberances (extraarticular manifestations)
- Tx: Preventitive and supportive
What is the main muscle for inspiration?
- It is a dome shaped structure separating thoracic cavity from the abdominal cavity and is attached to the lower ribs and sternum
*You also use the external intercostals, serratus posterior superior and levator costorum for inspiration
What muscles do you use for forced inspiration?
- External intercostals
- Scalene Anterior, middle, posterior
What muscles do you use for expiration?
None, it's a passive process dummy!
What muscles do you use for forced expiration?
- Internal intercostals
- Abdominal wall muscles (external, internal, oblique, transversus abdominis)
- Serratus posterior inferior
Movements of the thoracic wall and diaphragm during inspiration produce increases in what?
- Intrathoracic volume and diameters of the thorax!
Contraction of the diaphragm
results in what?
increase in the vertical dimension!
Contraction of the external intercostal muscles results in what?
- An increase in the AP dimension of the thorax, think of the pump handle movement in the picture above!
The rise of the lateral part of the ribs
results in what?
Increases the transverse dimension! *Think of the bucket handle movement in the above picture!
When the diaphragm and intercostal muscles relax what occurs?
Passive Expiration: which decreases intrathroacic volume and increases intrathoracic pressure!
CLINICAL: What if you injure the phrenic nerve?
- You could have paralysis of half the diaphragm (one dome or hemideiaphragm) due to injury of the motor supply of the phrenic n.
- Why doesn't it affect the other half?
- Because each dome has a separate nerve supply.
CLINICAL: What if you injure the phrenic nerve?
You could have paralysis of half the diaphragm which would result in the paralyzed diaphagm dome move superiorly due to the abdominal viscera (instead of descending during inspiration)
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