1. Bones & Joints 

1.1. Identify the bones that make up the thoracic cage/ walls:

1.1.1. Ribs & costal cartilages 
1.1.2. Sternum 
1.1.3. Thoracic vertebrae

1.1.4. Why do the ribs of infants and children not fracture as often in crushing injuries of the chest when compared to elders?
because the ribs of a child is more cartilaginous and elastic. costal catilage calcifies as we get older and is therefore less resilient in the elderly

1.2. Broadly classify & identify ribs as follows

1.2.1. True ribs - have sternal attachment (1-7)
1.2.2. False ribs- have costal margin attachments (8-10)
1.2.3. Free/floating ribs- not attached to sternum (11-12)

1.2.4. Why are the upper two and lower two ribs least commonly injured in a crushing injury of the chest?







the first and second rib are protected by the clavicle
the 11th and 12th rib are not attached to the sternum (not attached anteriorly) this allows them to swing freely during compression

1.3. Identify a typical rib 


1.3.1. Which ribs are typical?
ribs 3 to 9

1.3.2. What are the characteristic features of a typical rib?
A typical rib has the following characteristics:

• head -- articulates with bodies of vertebrae
• neck
• tubercle -- articulates with transverse processes
• angle -- a point just lateral to the
  tubercle where the shaft bends forward;
• costal groove -- lodges intercostal vessels and nerves

1.3.3. Where do fractures of ribs commonly occur?
it usually fractures 5cm in front of the tubercle as it is the weakest part of the rib

1.3.4. What is a ‘flail chest’?
1.3.5. What is paradoxical respiration?

A flail chest is a life-threatening medical condition that occurs when a segment of the rib cage breaks under extreme stress and becomes detached from the rest of the chest wall. It occurs when multiple adjacent ribs are broken in multiple places, separating a segment, so a part of the chest wall moves independently. The number of ribs that must be broken varies by differing definitions: some sources say at least two adjacent ribs are broken in at least two places,^[1] some require three or more ribs in two or more places.^[2] The flail segment moves in the opposite direction as the rest of the chest wall: because of the ambient pressure in comparison to the pressure inside the lungs, it goes in while the rest of the chest is moving out, and vice versa. This so-called "paradoxical motion" can increase the work and pain involved in breathing. Studies have found that up to half of people with flail chest die. Flail chest is invariably accompanied by pulmonary contusion, a bruise of the lung tissue that can interfere with blood oxygenation.^[3] Often, it is the contusion, not the flail segment, that is the main cause of respiratory failure in patients with both injuries. 
1.4. Identify the 1st rib (an atypical rib).

1.4.1. Locate the important structures related to the 1st rib
The first rib is atypical. It is found to be short, flat and more sharply curved than any of the others. It has upper and lower surfaces, with outer and inner borders, and on its head there is one articular facet only. The upper surface has two grooves for the subclavian artery and subclavian vein, separated by the scalene tubercle for the attachment of the scalene anterior muscle.

This rib has very little movement during respiration and serves as a base attachment for the intercostal muscles and the ribs below. In other words, during respiration, the muscles in the first intercostal space contract, drawing up on the rib below, which in turn allows its muscles to pull up on the rib below it and so forth, until all ribs have moved through a small distance. The combined movements increase the transverse and anteroposterior diameters of the thoracic cavity.

1.4.2. What is a ‘cervical rib”? Give its incidence and its significance.
a cervical rib in humans is a supernumerary (or extra) rib which arises from the seventh cervical vertebra. Sometimes known as "neck ribs"^[1] , their presence is a congenital abnormality located above the normal first rib. A cervical rib is present in only about 1 in 500 (0.2%) of people;^[2] in even rarer cases, an individual may have two cervical ribs.

The presence of a cervical rib can cause a form of thoracic outlet syndrome due to compression of the lower trunk of the brachial plexus or subclavian artery. These structures are entrapped between the cervical rib and scalenus muscle.

Compression of the brachial plexus may be identified by weakness of the muscles around the muscles in the hand, near the base of the thumb. Compression of the subclavian artery is often diagnosed by finding a positive Adson's sign on examination, where the radial pulse in the arm is lost during abduction and external rotation of the shoulder.

1.4.3. What are the boundaries of the ‘thoracic inlet’ (superior thoracic aperture)?
The superior thoracic aperture refers to the superior opening of the thoracic cavity. It is also referred to anatomically as the thoracic inlet and clinically as the thoracic outlet. The clinical entity called the Thoracic outlet syndrome refers to the superior thoracic aperture, not the inferior thoracic aperture.

The thoracic inlet is essentially a hole surrounded by a bony ring, through which several vital structures pass.
The superior thoracic aperture is bounded by:

a) the first thoracic vertebra (T1) posteriorly
b) the first pair of ribs laterally (more specifically, the first ribs form lateral C-shaped curves posterior to anterior)
c) the costal cartilage of the first rib and the superior border of the manubrium anteriorly.

 1.5. Identify the typical thoracic vertebrae.


 1.5.1. What are the characteristic features of a typical thoracic vertebra?

• body (1)
• superior and inferior demifacets (2,3)
• pedicle (4)
• superior and inferior articular processes (5, 6)
• transverse process (with an articular process) (7,10)
• lamina (8)
• spinous process (9)
• superior and inferior notches (13,12)
• vertebral canal(14)
• not a bone but an integral part of the vertebral column is the intervertebral disk (11) 

1.6. Identify the parts of the sternum (manubrium, body, xiphisternum).
 

• jugular notch (1)
• facet for head of first rib
• manubrium (2)
• facet for head of second rib
• manubriosternal joint (sternal angle) (3)
• body (made up of several fused sternabrae) (4)
• xiphoid process (xiphisternum) (5)

1.6.1. What is the role played by the sternum in cardiopulmonary resuscitation (CPR)?
in cardiac arrest, firm pressure is placed on the lower part of the sternum forcing blood from the ventricles into the great vessels

1.6.2. Why is the sternum the preferred site for bone marrow aspiration?
because it is subcutaneous and readily accessible as red marrow is present in adults here

1.7. Identify the major joints of the thoracic walls including the following thoracovertebral joints

Costovertebral joints- the articulations that connect the heads of the ribs with the bodies of the thoracicvertebrae. Joining of ribs to the vertebrae occurs at two places, the head and the tubercle of the rib. Two convex facets from the head attach to two adjacent vertebrae
 
Costotransverse joints- The facet of the tubercle of the rib forms an articulation with the adjacent transverse process of a thoracic vertebra. This is a plane type synovial joint

1.7.1.1. What types of joints are these and what movements are possible?
1.7.2.1. What types of joints are these and what movements are possible?

costotransverse joints are ball and socket joints except in the false ribs where they are plane joints

1.7.2. Sternum-related joints: Sternocostal joints (1st, 2-7th) Sternoclavicular joint Manubriosternal joint Other joints of the thoracic cage – costochondral,interchondral joints

manubriosternal joint- joint between manubrim and sternum (secondary cartilaginous joint-symphysis)

sternoclavicular joint- saddle type synovial joint

sternocostal
- 1st joint is a primary cartilaginous or synchondroses joint (moves with manubrim to give stability to upper limb)
- 2-7th joint is a synovialsecondary cartilaginous joint (hinge movement for breathing)

costochondral- primary cartilaginous joint (no movement)

interchondral- synovial plane joint



2. Muscles 

2.1. Identify the 3 layers of intercostal muscles and their features:



External Internal Innermost (including subcostal, transverse thoracis)

1. external intercostal muscles aid in quiet and forced inhalation. They originate on ribs 1-11 and have their insertion on ribs 2-12. The external intercostals are responsible for the elevation of the ribs, and expanding the transverse dimensions of the thoracic cavity.
2. internal intercostal muscles aid in forced expiration (quiet expiration is a passive process). They originate on ribs 2-12 and have their insertions on ribs 1-11. The internal intercostals are responsible for the depression of the ribs decreasing the transverse dimensions of the thoracic cavity.
3. innermost intercostal muscle, the deep layers of the internal intercostal muscles which are separated from them by a neurovascular bundle. This in turn is composed of:
   • transversus thoracis muscle
   • intercostal space
   • subcostalis muscle

2.1.1. How are the muscle fibres arranged?

external intercostal fibres are arranged anteroinferiorly directed obliquely, but pass in a direction opposite to those of the internal intercostal muscles

internal intercostal muscles are arranged in a anterosuperior manner in which they help pull down the ribcage 

The innermost intercostal muscle is arranged rudimentarily with few scattered laterally including those called subcostals (posteriorly) and transversus (anteriorly)

2.1.2. What are the actions of these muscles?
external icm- pulls ribs upwards during inspiration
internal icm- pulls ribs downwards during expiration
innermost icm- pulls ribs downwards during expiration

2.1.3. What is their nerve supply?
intercostal nerve

2.2. Identify the boundaries of a typical intercostal space.
The intercostal space (ICS) is the space between two ribs (Lat. costa). Since there are 12 ribs on each side, there are 11 intercostal spaces, each numbered for the rib superior to it.

2.2.1. In what plane are its contents located?

2.2.2. What is the relationship of its contents?

2.3. Identify the diaphragm.
In the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm (Ancient Greek: διάφραγμα diáphragma "partition"), is a sheet of internal skeletal muscle^[2] that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity (heart, lungs & ribs) from the abdominal cavity and performs an important function in respiration: as the diaphragm contracts, the volume of the thoracic cavity increases and air is drawn into the lungs.

2.3.1. Briefly describe the (sternal, costal and vertebral) attachments of the diaphragm.

Part	Origin
sternal	two muscular slips from the back of the xiphoid process
costal	the inner surfaces of the cartilages and adjacent portions of the lower six ribs on either side, interdigitating with the Transversus abdominis.
lumbar	aponeurotic arches, named the lumbocostal arches, and from the lumbar vertebrae by two pillars or crura.

2.3.2. Identify major openings of the diaphragm and associated vertebral levels.


2.3.3. What structures pass through the major openings?
2.3.4. Briefly list minor openings of the diaphragm and the structures passing through.

opening	level	structures
caval opening	T8	inferior vena cava, and some branches of the right phrenic nerve
esophageal hiatus	T10	esophagus, the anterior and posterior vagal trunks, and some small esophageal arteries
aortic hiatus	T12	the aorta, the azygos vein, and the thoracic duct

Three large openings — the aortic, the esophageal, and the vena cava — and a series of smaller ones are described.


Diaphragm is the primary respiratory muscle of the body. It, on contraction, increases the vertical diameter of the chest cavity by pulling its central tendon downwards. In this way, the lungs get extra space to expand and air rushes into them


2.4. Briefly explain the dynamic interaction between bones, joints and muscles of the thoracic cage involved in the mechanics of respiration.

2.4.1 why is respiration in the first 2 years of life almost entirely abdominal? adult thorax is oval and can therefore increase its diameter by thoracic breathing. in children the thorax is round and so the surface area cannot be increased as length remains constant because the ribs are straight and not oblique

2.5. Identify the accessory muscles of respiration attached to the thoracic cage: Pectoralis major Pectoralis minor Serratus anterior 2.5.1. Why does a dyspnoeic patient feel comfortable in a sitting position and by leaning forward and fixing the arms? in sitting position the diaphragm occupies the lowest sitting position thus maximum excursion and ventilation. by bending forward with arms crossed the patient is fixing his scapula allowing serratus anterior, pec major and pec minor to assist in respiration. 3. Breast 3.1.1. What is the normal extent of the breast T2-T6 3.1.2. With the help of a model identify the different structures and tissue present in the breast?  3.1.3. What is the arterial supply of the breast?  anterior intercostal branches of the internal thoracic (mammary) arteries (from the subclavian artery)  lateral thoracic artery and thoracodorsal artery (from the axillary artery) 3.2. SPREAD OF BREAST CANCER 3.2.1. How may the carcinoma spread via lymphatics,via veins? 3.2.2. How may Cooper’s ligaments involvement be evident in breast carcinoma?  invasive carcinoma may involve coopers ligaments and cause retraction of the ligaments and dimpling of the overlying skin giving it an "orange peel" like texture 4. Vessels 4.1. Identify the internal thoracic artery. 4.1.1. Locate its origin subclavian artery 4.1.2. What are its main branches and area of supply? pericardacophrenic artery internal thoracic artery around the sixth intercostal space it divides into the musculophrenic artery that supplies the pericardium, diaphragm, and muscles of the abdominal wall and the superior epigastric artery supplies the anterior part of the abdominal wall and some of the diaphragm. 4.2. Identify the anterior & posterior intercostal arteries. 4.2.1. What is the origin of these arteries? internal thoracic and aorta 4.2.2. What do they supply? muscular branches to the intercostal, serratus anterior, and pectoral muscles 4.3. Identify the intercostal veins. 4.3.1. Which major veins do these drain into? Azygos vein 5. Nerves 5.1. The thoracic spinal nerves are typical spinal nerves. 5.1.1. Draw a labelled schematic diagram showing a typical thoracic spinal nerve with all its communications ( including the intercostal nerves). 5.2. Identify and trace the origin of the intercostal nerves. thoracic spinal nerves T1-T11 5.2.1. What is the distribution of the following intercostals nerves?  5.2.2. 1st  - forms lower trunk of brachial plexus with C8 5.2.3. 2nd - forms intercostobrachial nerve 5.2.4. 3-6th - supplies the thoracic wall 5.2.5. 7-11th- supplies the anterior abdominal wall 5.3. Identify the phrenic nerve. 5.3.1. What is its origin/root value? C3-C5 5.3.2. What structures does it supply? motor innervation to the diaphragm and sensory innervation to the pericardium, mediastinal pleura & diaphragm 5.3.3. Where is referred pain from the phrenic nerve commonly sited? skin of the ipsilateral supraclavicular region (top of shoulder on the same side) 5.3.4. What are the effects of phrenic nerve injury? paralysis of diaphragm and breathing difficulties