Thorax walls Flashcards
What are the layers of the chest wall?
- Skin
- Superficial fascia - loose layer of fatty connective tissue that wraps other organs
- Limb muscle - pectoralis, latissimus, serratus
- Ribs and intercostal muscles
- Pleura - lines the chest wall
What is the superficial fascia?
Adipose tissue covering the chest and abdominal wall
Attached to the muscles by fibrous tissue
Within this layer you can find the glandular tissue and fatty connective tissue of the breast
What is the composition of breast tissue in non-lactating women?
50% fat
50% glandular tissue
What is the composition of breast in lactating women?
33% fat
67% glandular tissue
What is a unique presentation of breast cancer?
Orange peel
Cooper suspensory ligaments attach breasts to the chest wall
Invasion of these ligaments causes the characteristic dimpling effect seen in breast cancer
What are possible signs of breast cancer?
Lumps Nipple discharge Dimpling Breast or nipple pain Nipple retraction or inversion Redness Changes to the skin's texture Lymph node changes Swelling
What structures do the lymph vessels from the breast drain to?
Axillary nodes
Opposite breast
Deep thoracic nodes in the stomach
During which occassions will the lymph node size increase?
Infection
Cancer metastasis
Which arteries supply the breast?
Arteries of the chest wall
Arteries of the arm
What are the two types of muscle in the thorax?
Limb muscles - muscles of the arm that are attached to the chest wall
Intercostal muscles - musculoskeletal core of the body
What are the 3 main limb muscles of the chest wall?
Pectoralis
Latissimus dorsi
Serratus anterior
What is the role of the pectoralis muscle?
Attaches the arm to the chest wall
What is the role of the Latissimus dorsi?
Attaches arm to the chest wall
What is the role of the serratus anterior?
Originates from the upper ribs and attaches to the back of the shoulder blade
Helps maintain the shoulder in its place, and stops the scapula from winging outwards
What is the function of the thoracic cage?
Protects the thoracic and upper abdominal contents (liver, lungs, spleen)
May be perforated if the ribs are broken
What are the components of the thoracic cage?
12 ribs
Sternum
What are the different types of ribs in the rib cage?
1 to 7 true ribs attached directly to the sternum
8 to 10 false ribs not directly attached to the sternum but to the cartilage that surrounds the sternum
11 to 12 are free ribs and is not attached to the sternum
What are the 3 parts of the sternum?
Manubrium - top part of the sternum, gap between clavicles
Body
Xiphisternum - cartilagenous end piece that becomes harder as it calcifies with age
What types of joints exist between the ribs and the sternum?
The joints betwwen the ribs and sternum are synovial
Except the joint between the manubrium and the body of the sternum = firbocartilaginous and allows flexion during breathing
What is the joint between the manubrium and the body of the sternum called?
The manubriosternal joint
Describe how intermembrane muscle become membranous?
External intercostal muscles become membranous anteriorly to form the external intercostal membrane
Internal intercostal muscles become membranous posteriorly to form the internal intercostal membrane
Therefore, when you look at the front of the lungs, you see the internal intercostal muscles first since they are seen through the external intercostal membrane
What are ribs an example of?
Segmentation of the mesoderm
What two arteries supply the intercostal muscles?
Posterior intercostal arteries
Anterior intercostal arteries
What is the origin of posterior intercostal arteries?
Near the spinal cord
Branch from the aorta
What is the origin of anterior intercostal arteries?
Near the sternum
Branch from the internal thoracic arteries (which are branches of the subclavian arteries)
What can be found in the intercostal space?
Intercostal vein
Intercostal arteries
Intercostal nerve - from the spinal column supplying muscles in that space, as well as giving off branches of the skin to form the dermatome
These nerves send sensoy fibres to the parietal pleura internally and to the skin in a segmental pattern
How are intercostal contents arranged within the space?
Vein
Artery
Nerve
Explain the drainage system of the posterior thoracic wall
Posterior intercostal veins drain to azygous veins running down one side of the aorta, which drain to the superior vena cava
What are hemiazygous veins?
Sometimes the azygous veins are paired
What is the parietal pleura?
The serous lining of the rib cage
Describe the shape of the thorax
Conical
- the top is conical
- the sides are formed by the ribs
- the base is closed by the diaphragm
Describe the shape of the diaphragm
Double-domed, musculotendinous tissue
What is the origin of the muscular components of the diaphragm?
The diaphragm is formed by muscle slips that converge one a central tendon in a colver lead shape.
These muscle slips originate from:
- The ribs - costal ribs
- The lumbar vertebrae - crura
- Sternum - sternal slips
- Thick fascia over the muscles in the back (arcuate ligaments)
What are the 3 openings of the diaphragm?
- Inferior vena cava + right phrenic nerve
- Oesophagus + right/left vagus nerve, esophageal branches of left gastric artery
- Aorta + thoracic duct/azygous vein
At what level does the inferior vena cava enter the diaphragm?
Level T8
Through the central tendon
At what level does the oesophagus enter the diaphragm?
Level T10
Through the crura
At what level does the aorta enter the diaphragm?
Level T12
Passess behind the diaphragm
How does congenital diaphragmatic hernia develop? `
Develops when component parts of the diaphragm fail to develop properly, leading to:
- compressed lung
- liver partially up into chest
- small intestine in the left chest pushing heart and lungs to the heart
Which nerve supplies the diaphragm?
Phrenic nerves
What type of innervation does the phrenic nerve supply to the diaphragm?
Sensory to the central part of the diaphragm
Motor to all the diaphragm
What type of nerve is the phrenic nerve?
Somatic
What type of muscle is the diaphragm?
Skeletal muscle
Apart from the diaphragm, what other structures does the phrenic nerve innervate?
Sensory to the pleura of the heart
Sensory to the parietal pleura
Peritoneum layer and underneath the diaphragm
What is the serous membrane called in separate parts of the body?
Pleura in the thorax
Peritoneum in the abdomen
What are the 4 main embryonic components of the development of the diaphragm
- Septum transversum - forms the central tendon to which all the other components come together
- Pleuroperitoneal folds - folds in to close the pericardioperitoneal canal
- Mesentery of the esophagus
- Muscle cells from the somites of the cervical region
What is the septum transversum?
Sheet of fibrous tissue between the heart and liver
Gives rise to the central tendon of the diaphragm
What explains the complicated innervation of the phrenic nerve?
Embryology
Skeletal muscle that makes up the diaphragm comes from myotomes in the neck
These invade the pleuroperitoneal membran and the esophageal mesentery
As they invade, they drag their nerve supply with them from the neck into the thorax
