Session 1.2a - Gray's Anatomy for Students: Chapter 3 - Thorax - Conceptual overview Flashcards
https://www.clinicalkey.com/#!/content/book/3-s2.0-B9780702051319000031 - General description - Functions - Component parts - Relationship to other regions
What is the shape of the thorax?
An irregularly shaped cylinder
Describe the superior and inferior openings of the thorax.
Narrow opening superiorly
Relatively large opening inferiorly
(Fig. 1)
What is the superior opening of the thorax called?
Superior thoracic aperture
What is the inferior opening of the thorax called?
Inferior thoracic aperture
Which apertures of the thorax are open and closed?
The superior thoracic aperture is open
The inferior thoracic aperture is closed
What is the significance of the superior thoracic aperture being open?
It allows continuity with the neck
What is the significance of the inferior thoracic aperture being closed?
It is closed by the diaphragm
Fig. 3.1
Label and caption the image
- Diaphragm
- Ribs
- Right pleural cavity
- Vertebral column
- Superior thoracic aperture
- Mediastinum
- Left pleural cavity
- Rib I
- Manubrium of sternum
- Sternal angle
- Body of sternum
- Xiphoid process
- Inferior thoracic aperture
Thoracic wall and cavity.
Describe the thorax wall.
The musculoskeletal wall of the thorax is flexible.
What does the thorax wall consists of?
Segmentally arranged vertebrae, ribs, and muscles and the sternum.
What is the thoracic cavity enclosed by?
The thoracic wall and the diaphragm
The thoracic wall and the diaphragm enclosed what? How is this subdivided?
The THORACIC CAVITY is subdivided into three major compartments
What are the three compartments of the thoracic cavity?
- left pleural cavity
- right pleural cavity
- mediastinum
What do the left and right pleural cavities surround?
Each surrounds a lung
Describe the structure of the mediastinum
Thick, flexible soft tissue partition
Where is the mediastinum located?
Oriented longitudinally in a median sagittal position.
What does the mediastinum contain?
- Heart
- Oesophagus
- Trachea
- Major nerves
- Major systemic blood vessels
How are the pleural cavities separated from each other?
They are completely separated from each other by the mediastinum.
What is the clinical significance of the pleural cavities being separated from each other?
Abnormal events in one pleural cavity do not necessarily affect the other cavity.
What is the surgical significance of the pleural cavities being separated from each other by the mediastinum?
The mediastinum can be entered surgically without opening the pleural cavities.
Where do the pleural cavities extend?
Above the level of rib I.
Where does the apex of each lung extend?
Into the root of the neck
What is the signifiance of the apex of the lungs extending into the root of the neck?
Abnormal events in the root of the neck can involve the adjacent pleura and lung, and vice versa.
What are the functions of the thorax?
- Breathing
- Protection of vital organs
- Conduit
What does the thorax contain to aid in breathing?
One of the most important functions of the thorax is breathing. The thorax not only contains the lungs but also provides the machinery necessary - the diaphragm, thoracic wall, and ribs.
As well as the lungs, what is the machinery necessary for breathing, and what do they do?
Diaphragm, thoracic wall, and ribs - for effectively moving air into and out of the lungs.
What movements of the diaphragm change the volume of the thoracic cavity?
Up and down movements of the diaphragm
What movements of the thoracic wall change the volume of the thoracic cavity?
Changes in the lateral and anterior dimensions of the thoracic wall, caused by movements of the ribs
Movements in the diaphragm and thoracic wall alter the volume of the thoracic cavity. These are ___
key elements in breathing.
The thorax houses and protects ___
Vital organs such as:
- heart
- lungs
- great vessels
How does the thoracic wall offer protection?
Because of the domed shape of the diaphragm, the thoracic wall also offers protection to some important abdominal viscera.
What organ(s) lie under the right dome of the diaphragm?
Much of the liver lies under the right dome of the diaphragm
What organ(s) lie under the left dome of the diaphragm?
Stomach and spleen
What organ(s) lie on the diaphragm?
The posterior aspects of the superior poles of the kidneys
Where are the kidneys in relation to the ribs?
Right: anterior to rib XII
Left: anterior to ribs XI and XII
The mediastinum acts as a conduit for ___
for structures that:
- pass completely through the thorax from one body region to another
- connect organs in the thorax to other body regions
Which structures pass between the abdomen and neck, and therefore pass through the mediastinum?
Oesophagus
Vagus nerves
Thoracic duct
The oesophagus, vagus nerves, thoracic duct pass where?
Between the abdomen and neck via the mediastinum
What innervates the diaphragm?
The phrenic nerve
Where do the phrenic nerves pass?
Originate in the neck, penetrate and supplies the diaphragm - therefore passes through the mediastinum
What structures pass within the mediastinum to and from major visceral organs in the thorax?
Trachea
Thoracic aorta
Superior vena cava
The trachea, thoracic aorta and superior vena cava travel where?
These course within the mediastinum en route to and from major visceral organs in the thorax.
What are the component parts of the thorax?
- Thoracic wall
- Superior thoracic aperture
- Inferior thoracic aperture
- Diaphragm
- Mediastinum
- Pleural cavities
What does the thoracic wall consist of?
Skeletal elements and muscles (Fig. 3.1)
What is the thoracic wall made up of posteriorly?
12 thoracic vertebrae and their intervening intervertebral discs
What is the thoracic wall made up of laterally?
Formed by RIBS (12 on each side) and three layers of flat muscles, which span the intercostal spaces between adjacent ribs, move the ribs, and provide support for the intercostal spaces.
How many intercostal muscles are there?
3 layers
What sort of muscles are intercostal muscles?
Flat
Where do the intercostal muscles span?
Intercostal spaces between adjacent ribs
What do intercostal muscles do?
Move the ribs
Provide support for the intercostal spaaces
What is the thoracic wall made up of anteriorly?
The STERNUM
What makes up the sternum?
The manubrium of sternum, body of sternum and xiphoid process.
Where is the manubrium of sternum angled?
Angled posteriorly on the body of sternum at the manubriosternal joint
What is the manubriosternal joint also known as?
The sternal angle
What part of the sternum is a major surface landmark used by clinicians in performing physical examinations of the thorax?
The sternal angle
What is found at the anterior (distal) end of each rib?
Costal cartilage
Where is costal cartilage found?
The anterior (distal) end of each rib
What does costal cartilage contribute to?
The mobility and elasticity of the wall.
What do all ribs articulate with posteriorly?
Thoracic vertebrae
Which ribs have three articulations with the vertebral column?
Rib II to IX (most ribs)
Most ribs (from rib II to IX) have _____ articulations with the vertebral column.
three
What do the head of each rib articulate with?
The body of its own vertebra and the body of the vertebra above (Fig. 3.2)
As the ribs curve posteriorly, what do they also articulate with?
The transverse process of its vertebra
Which part of the rib articulates with the vertebra?
The head
Fig. 3.2
Label and caption the image
- Superior articular process
- Superior costal facet
- Costal facet of transverse process
- Intervertebral disc
- Vertebral body
- Inferior costal facet
- Inferior articular process
- Sternum
- Rib V
- Costal cartilage
Joints between ribs and vertebrae.
Anteriorly, the costal cartilages of rib I to VII articulate with ___?
The sternum
Anteriorly, the sternum articulates with ___?
The costal cartilages of ribs I to VII
The costal cartilages of ribs VIII to X articulate with ___?
the inferior margins of the costal cartilages above them.
Ribs XI and XII are called ________ ____?
Floating ribs
Why are ribs XI and XII called floating ribs?
Because they do not articulate with other ribs, costal cartilages or the sternum.
Describe the costal cartilages of ribs XI and XII.
They are small, only covering their tips
The skeletal framework of the thoracic wall provides extensive attachment sites for muscles of the ___?
Neck, abdomen, back and upper limbs.
Name 2 functions of the muscles that attach to the framework of the thoracic wall.
- A number of these muscles attach to ribs and function as accessory respiratory muscles
- Some of them also stabilise the position of the first and last ribs
Muscles that aid breathing by attaching to the ribs are known as ___?
Accessory respiratory muscles
Some muscles attaching to the framework of the thoracic wall help to stabilise the position of the _____ and _____ ribs
first and last
What is the superior thoracic aperture surrounded by?
Completely surrounded by skeletal elements
What is found posterior to the superior thoracic aperture?
The body of T1
What is found on each side of the superior thoracic aperture?
The medial margin of rib I
What is found anteriorly to the superior thoracic aperture?
Manubrium
Where is the superior margin of the manubrium?
In approximately the same horizontal plane as the intervertebral disc between vertebrae TII and TIII.
How does the first rib articulate with the manubrium?
The first ribs slope inferiorly from their posterior articulation with vertebra TI to their anterior attachment to the manubrium.
How does the plane of the superior thoracic aperture (STA) sit, and why?
At an oblique angle.
The first ribs slope inferiorly from their posterior articulation with vertebra TI to their anterior attachment to the manubrium.
Consequently, the plane of the STA is at an oblique angle, facing somewhat anteriorly.
Where does the STA face?
Somewhat anteriorly (an at oblique angle)
Where do the pleural cavities lie at the STA?
At the STA, the superior aspects of the pleural cavities, which surround the lungs, lie on either side of the entrance to the mediastinum (Fig. 3.3)
Fig. 3.3
Label and caption the image
- Rib II
- Subclavian artery and vein
- Apex of right lung
- Rib I
- Superior thoracic aperture
- Vertebra TI
- Common carotid artery
- Oesophagus
- Trachea
- Internal jugular vein
- Manubrium of sternum
Structures that pass between the upper limb and thorax pass over ___?
Rib I and the superior part of the pleural cavity as they enter and leave the mediastinum
Structures that pass between the upper limb and thorax enter and leave the ___?
mediastinum
Describe the passage of structures that pass between the neck and head and the thorax.
These structures pass more vertically through the STA.
Describe the inferior thoracic aperture (ITA).
It is large and expandable.
What forms the margin of the ITA.
Bone, cartilage and ligaments (Fig. 3.4A).
Fig. 3.4A
Label and caption the image
- Xiphoid process
- Inferior thoracic aperture
- Distal cartilaginous ends of ribs VII to X; costal margins
- Rib XI
- Rib XII
- Vertebra TXII
Inferior thoracic aperture
Fig. 3.4B
Label and caption the image
- Right dome
- Central tendon
- Left dome
- Oesophageal hiatus
- Aortic hiatus
Diaphragm
What is the ITA closed by?
The diaphragm
Structures passing between the abdomen and thorax _______ to the _______
pierce or pass posteriorly to the diaphragm.
Where are the skeletal elements of the ITA?
- Posteriorly
- Posterolaterally
- Anterolaterally
- Anteriorly
What is the skeletal element to the ITA posteriorly?
The body of vertebra TXII
What is the skeletal element to the ITA posterolaterally?
Rib XII and the distal end of rib XI
What is the skeletal element to the ITA anterolaterally?
The distal cartilaginous ends of ribs VII to X, which unite to form the costal margin anterolaterally
What is the skeletal element to the ITA anteriorly?
The xiphoid process
The joint between the ______ ______ and sternum lies roughly in the ____ _________ _____ as the _______________ ____ between vertebrae ___ and __.
The joint between the costal margin and sternum lies roughly in the same horizontal plane as the intervertebral disc between vertebrae TIX and TX.
Describe the relation between the posterior and anterior margin of the ITA.
The posterior margin of the inferior thoracic aperture is inferior to the anterior margin.
When viewed anteriorly, the ITA is tilted __________
When viewed anteriorly, the ITA is tilted superiorly.
What sort of tissue is the diaphragm
Musculotendinous
What does the diaphragm seal?
The ITA (Fig. 3.4B)
Where do muscles fibres of the diaphragm arise?
Generally, they arise radially, from the margins of the ITA.
Where do muscle fibres of the diaphragm converge?
Into a large central tendon (generally)
Describe the posterior and anterior attachments of the diaphragm.
Because of the oblique angle of the ITA, the posterior attachment of the diaphragm is inferior to the anterior attachment.
Describe the shape of the diaphragm.
it is not flat; rather, it “balloon” superiorly, on both the right and left sides, to form domes.
Which dome of the diaphragm is higher?
The right dome is higher than the left, reaching as far as rib V.
What happens when the diaphragm contracts?
The height of the domes decrease and the volume of the thorax increases
Which structures penetrate the diaphragm?
The oesophagus and inferior vena cava
Where does the aorta pass, in relation to the diaphragm?
Posterior
What is the mediastinum and its borders?
A thick midline partition that extends from the sternum anteriorly to the thoracic vertebrae posteriorly, and from the STA to the ITA.
The mediastinum can be separated into ___?
Superior and inferior parts.
How is the mediastinum separated into superior and inferior parts?
A horizontal plane passing through the sternal angle and the intervertebral disc between vertebrae TIV and TV (Fig. 3.5)
How is the inferior part further subdivided?
By the pericardium
What is the pericardium?
Encloses the pericardial cavity surrounding the heart.
What constitutes the middle mediastinum?
The pericardium and heart
Fig. 3.5
Label and caption the image, including the vertebrae
- Stenal angle
- Superior mediastinum
- Inferior mediastinum
- Diaphragm
- Rib I
- Anterior mediastinum
- Middle mediastinum
- Posterior mediastinum
- TI, TIV, TV, TX, TXII correctly labelled (L1 underneath - note thicker vertebral body).
Subdivisions of the mediastinum.
Where does the anterior mediastinum lie?
Between the sternum and the pericardium
Where does the posterior mediastinum lie?
Between the pericardium and thoracic vertebrae.
Where are the pleural cavities situated?
The two pleural cavities are situated on either side of the mediastinum (Fig. 3.6).
Fig. 3.6
Label and caption the image
- Apex of right lung
- Right main bronchus
- Parietal pleura
- Visceral pleura
- Right pleural cavity
- Costodiaphragmatic recess
- Trachea
- Left pleural cavity surrounding left lung
- Mediastinum
- Diaphragm
Pleural cavities.
What is each pleural cavity lined by?
A mesothelial membrane called the pleura
What type of membrane is the pleura
Mesothelial
During development, the lungs grow where?
The lungs grow out of the mediastinum, becoming surrounded by the pleural cavities. As a result, the outer surface of each organ is covered by pleura.
How does the lung remain attached to the mediastinum?
By a root formed by the airway, pulmonary blood vessels, lymphatic tissues and nerves.
What does the parietal pleura line?
The walls of the cavity
Where does the visceral pleura lie?
It is reflected from the mediastinum at the roots and onto the surfaces of the lungs
What lies between the two pleura?
Only a potential space normally exists between the visceral pleura covering lung and the parietal pleura lining the wall of the thoracic cavity.
Describe the relationship between the lung and the pleural cavity (size-wise).
The lung does not completely fill the potential space of the pleural cavity, resulting in recesses, which do not contain lung.
What is the clinical significance of the recesses formed by the larger size of the pleural cavity compared to the lung?
These are important for accommodating changes in lung volume during breathing.
What is the largest and clinically most important recess?
The costodiaphragmatic recess
The costodiaphragmatic recess is the ___
largest and clinically most important recess.
Where does the costodiaphragmatic recess lie?
Inferiorly between the thoracic wall and diaphragm.
The thorax has a relationship to other regions such as the:
- Neck
- Upper limb
- Abdomen
- Breast
The STA opens directly ___
into the root of the neck (Fig. 3.7)
Fig 3.7
Label and caption the image
- Brachial plexus
- Oesophagus
- SUPERIOR THORACIC APERTURE
- Rib I
- Scapula
- AXILLARY INLET
- Subclavian artery and vein
- Trachea
- Clavicle
- Coracoid process
Superior thoracic aperture and axillary inlet.
Where is the superior aspect of each pleural cavity?
This extends approximately 2-3 cm above rib I and the costal cartilage into the neck.
Where do major visceral structures pass between the neck and superior mediastinum?
Between these pleural extensions
What two major visceral structures lie in the midline of the neck?
The trachea, which lies immediately anterior to the oesophagus
Major blood vessels and nerves pass in and out of hte thorax at the ___ _____ and _____ to these structures.
STA anteriorly and laterally
What lies either side of the STA?
An AXILLARY INLET, or gateway to the upper limb.
What parts of the thorax communicate superiorly with the root of the neck?
The two axillary inlets and the STA (Fig. 3.7).
What is each axillary inlet formed by?
- Scapula
- Clavicle
- Rib I
What forms the posterior border of the axillary inlet?
The superior margin of the scapula
What forms the anterior border of the axillary inlet?
The clavicle
What forms the medial border of the axillary inlet?
The lateral margin of rib I
Where is the apex of the axillary inlet?
The apex of each triangular inlet is directed laterally
What forms the apex of the axillary inlet?
Medial margin of the coracoid process
Where is the coracoid process?
It extends anteriorly from the superior margin of the scapula.
What forms the base of the axillary inlet?
The base of the axillary inlet’s triangular opening is the lateral margin of rib I.
How do large blood vessels pass between the axillary inlet and STA?
By passing over rib I
What passes between the neck and upper limb through the axillary inlet?
Proximal parts of the brachial plexus
The diaphragm separates ___
the thorax from the abdomen.
Structures that pass between the _____ and _____ either penetrate the diaphragm or ____ ________ ___ ___.
thorax and abdomen; or pass posteriorly to it (Fig. 3.8)
What is the relationship of the inferior vena cava to the diaphragm?
This pierces the CENTRAL TENDON OF THE DIAPHRAGM to enter the right side of the mediastinum near vertebral level TVIII.
Where does the inferior vena cava cross the diaphragm?
To enter the right side of the mediastinum near vertebral level TVIII.
What is the relationship of the oesophagus to the diaphragm?
It penetrates the muscular part of the diaphragm
Where does the oesophagus cross the diaphragm?
It leaves the mediastinum and enters the abdomen just to the left of the midline at vertebral level TX.
What is the relationship of the aorta to the diaphragm?
It passes posteriorly to it
Where does the aorta cross the diaphragm?
At the midline at vertebral level TXII
Numerous other structures that pass between the thorax and abdomen pass _______ or _________ to the _________.
Through, posterior, diaphragm
Fig. 3.8
Label and caption the image.
- Caval opening (vertebral level TVIII)
- Inferior vena cava
- Oesophagus
- Aorta
- Central tendon of diaphragm
- Aortic hiatus (vertebral level TXII)
- LI
- Oesophageal hiatus (vertebral level TX)
Major structures passing between abdomen and thorax.
What do the breasts consist of?
Secretory glands, superficial fascia, and overlying skin
Where are the breasts?
In the PECTORAL REGION on each side of the anterior thoracic wall (Fig. 3.9)
Fig. 3.9A
Label and caption the image
- Axillary process
- Axillary lymph nodes
- Fourth thoracic intercostal nerve
- Lymphatic vessels
- Internal thoracic artery
- Second, third and fourth perforating branches of internal thoracic artery
- Parasternal lymph nodes
Right breast
Fig. 3.9B
Label and caption the image
- Pectoralis major
- Lactiferous sinuses
- Lactiferous ducts
- Secretory glands
- Deep (pectoral) fascia
Right breast
Where do branches of the internal thoracic arteries and veins perforate the chest wall?
Anteriorly, on each side of the sternum
What do branches from the internal thoracic arteries supply?
Anterior aspects of the thoracic wall.
Branches associated mainly with the ___ to ___ intercostal spaces also supply the anteromedial parts of each breast.
2nd to 4th
Branches associated mainly with the 2nd to 4th intercostal spaces also supply the ____________ parts of each breast.
anteromedial
Lymphatic vessels from the medial part of the breast accompany ___
the perforating arteries
Lymphatic vessels drain into ___
the parasternal nodes
Where are the parasternal nodes?
On the deep surface of the thoracic wall
Vessels and lymphatics associated with lateral parts of the breast ______ from or _____ into the _______
emerge from or drain into the AXILLARY REGION of the upper limb.
Lateral and anterior branches of the ___ to ___ intercostal nerves carry _______ from the skin of the breast
4th to 6th; general sensation from the skin of the breast
What are some key features of the thorax?
- Vertebral level TIV/V
- Venous shunts from left to right
- Segmental neurovascular supply of thoracic wall
- Sympathetic system
- Flexible wall and inferior thoracic aperture
- Innervation of the diaphragm
Why are vertebral levels important clinically?
When working with patients, physicians use vertebral levels to determine the position of important anatomical structures within body regions.
Broadly, what occurs at TIV/V clinically?
The horizontal plane passing through the disc that separates thoracic vertebrae TIV and TV is one of the most significant planes in the body (Fig. 3.10).
The horizontal planes passing through the disc between TIV/V is is significant clinically because it marks the level or involvement of these structures:
(more detail another card)
- sternal angle (and rib II)
- superior/inferior mediastinum
- pericardium
- arch of aorta
- superior vena cava/pericardium
- trachea/main bronchi
- pulmonary trunk
What does the disc that separates TIV and TV mark in regards to the sternal angle?
It passes through the sternal angle anteriorly
What does the disc that separates TIV and TV mark in regards to the rib II?
It passes through the sternal angle anteriorly, marking the position of the anterior articulation of the costal cartilage of rib II with the sternum.
What is the sternal angle used for?
To find the position of rib II as a reference for counting ribs.
Why is rib II (found via the sternal angle) used as a reference for counting ribs?
Because of the overlying clavicle, rib I is not palpable.
What does the disc that separates TIV and TV mark in regards to the mediastinum?
Separates the superior mediastinum from the inferior mediastinum
What does the disc that separates TIV and TV mark in regards to the pericardium?
Marks the position of the superior limit of the pericaridum
What does the disc that separates TIV and TV mark in regards to the arch of aorta?
Marks where this begins and ends
What does the disc that separates TIV and TV mark in regards to the superior vena cava?
Passes through the site where the superior vena cava penetrates the pericardium to enter the heart
What does the disc that separates TIV and TV mark in regards to the trachea?
Level at which trachea bifurcates into right and left main bronchi
What does the disc that separates TIV and TV mark in regards to the pulmonary trunk?
Marks the superior limit of the pulmonary trunk
Fig. 3.10
Label and caption the image.
- Sternal angle
- Aortic arch
- Superior mediastinum
- Trachea
- Rib II
- TIV
- TV
- Inferior mediastinum
Vertebral level TIV/V.
What does the right atrium do?
It is the chamber of the heart that receives deoxygenated blood returning from the body.
Where does the right atrium lie?
On the right side of the midline
What are the two major veins that drain into the right atrium?
The superior and inferior venae cavae.
Where are the superior and inferior venae cavae located?
On the right side of the body (they drain into the right atrium).
To get to the right side of the body, blood coming from the left sides must ___?
All blood coming from the left side has to cross the midline.
Blood travelling from the left side to get to the right side is called ___?
Left-to-right shunting
How is left-to-right shunting carried out?
By a number of important and, in some cases, very large veins, several of which are in the thorax.
Fig. 3.11
Label and caption the image
- Inferior vena cava
- Azygos vein
- Right atrium
- Superior vena cava
- Left internal jugular vein
- LEFT BRACHIOCEPHALIC VEIN
- Intercostal vein
- ACCESSORY HEMIAZYGOS VEIN
- HEMIAZYGOS VEIN
Left-to-right venous shunts.
In adults, the left brachiocephalic vein crosses the midline ___________ and delivers blood from the left side.
Immediately posterior to the manubrium
The left brachiocephalic vein delivers blood from ___
The left side of the head and neck, the left upper limb, and part of the left thoracic wall
Where does the left brachiocephalic vein drain into?
The superior vena cava.
What do the hemiazygos and accessory hemiazygos drain?
Posterior and lateral parts of the left thoracic wall
Where do the hemiazygos and accessory hemiazygos pass?
Immediately anterior to the bodies of thoracic vertebrae.
What do the hemiazygos and accessory hemiazygos vein on the left side drain into?
They flow into the azygos vein on the right side, which ultimately connects with the superior vena cava.
The arrangement of vessels and nerves that supply the thoracic wall reflect what?
The segmental organisation of the wall.
Arteries to wall arise where?
From two sources:
- thoracic aorta
- internal thoracic arteries
Where is the thoracic aorta?
In the posterior mediastinum
What are the internal thoracic arteries?
A pair of vessels which run along the deep aspect of the anterior thoracic wall on either side of the sternum
Where are the internal thoracic arteries siutated?
Either side of the sternum, along the deep aspect of the anterior thoracic wall.
Posterior and anterior intercostal vessels branch segmentally from the thoracic aorta/internal thoracic arteries, and pass ___?
Laterally around the wall, mainly along the inferior margin of each rib (Fig. 3.12A).
What runs with the intercostal vessels?
The intercostal nerves
Specifically, which intercostal nerves run with the intercostal vessels?
The anterior rami of thoracic spinal nerves.
What do the intercostal nerves innervate?
The wall, related parietal pleura, and associated skin.
Why is it important to know where these nerves and vessels run?
The position of these nerves and vessels relative to the ribs must be considered when passing objects, such as chest tubes, through the thoracic wall.
Give an example of an object (medically) that might pass through the thoracic wall.
A chest tube
Fig. 3.12A
Label and caption the diagram
- INTERCOSTAL NERVE
- POSTERIOR INTERCOSTAL ARTERY
- Lateral cutaneous branch
- Arch of aorta
- Right subclavian artery
- Left common carotid artery
- Internal thoracic arteries
- ANTERIOR INTERCOSTAL ARTERY
- Anterior cutaneous branch
Segmental neurovascular supply of thoracic wall.
Fig. 3.12B
Label and caption the diagram. Label the dermatome innervation of T1-T12.
- Supraclavicular nerves
- Xiphoid process
- Costal margin
- Umbilicus
- Anterior superior iliac spine
- Inguinal ligament
- Pubic tubercles
T1-T12 correctly labelled.
Anterior view of thoracic dermatomes associated with thoracic spinal nerves.
Fig. 3.12C
Label and caption the diagram. Label the dermatome innervation of T2-T12.
- Xiphoid process
- Costal margin
- Umbilicus
T2-T12 correctly labelled
Lateral view of dermatomes associated with thoracic spinal nerves.
Describe the link between the dermatomes and the segmental organisation of the spinal nerves.
Dermatomes of the thorax generally reflect the segmental organisation of the thoracic spinal nerves (Fig. 3.12B).
Where is the exception of the dermatomes of the thorax and the segmental organisation of the thoracic spinal nerves?
The exception occurs, anteriorly and superiorly, with the first thoracic dermatome, which is located mostly in the upper limb, and not on the trunk.
The anterosuperior region of the trunk receives what innervation?
Branches from the anterior ramus of C4
The anterosuperior region of the trunk receives innervation from C4 - how?
Via supraclavicular branches of the cervical plexus.
What is the highest thoracic dermatome on the anterior chest wall?
T2
T2 is the _______ thoracic dermatome on the _______ _____ ____.
highest; anterior chest wall.
Where does the T2 dermatome lie?
It is the highest thoracic dermatome on the anterior chest wall, and also extends into the upper limb.
What is skin over the xiphoid process innervated by?
In the midline, skin over the xiphoid process is innervated by T6.
Dermatomes of __ to ___ follow the contour of the ribs onto the _______ _____ ____.
Dermatomes of T7 to T12 follow the contour of the ribs onto the anterior abdominal wall (Fig. 3.12C).
All preganglionic nerve fibres of the sympathetic system are carried out of the spinal cord in _______
spinal nerves T1 to L2 (Fig. 3.13).
All _______ ____ _____ of the ______ system are carried out of the spinal cord in spinal nerves T1 to L2.
preganglionic nerve fibres; sympathetic (Fig. 3.13).
All preganglionic nerve fibres of the sympathetic system are carried out of the spinal cord in spinal nerves T1 to L2. This means that sympathetic fibres found ________ in the body ________ emerge from the ______ ____ as ______ of these spinal nerves.
Sympathetic fibres found anywhere in the body ultimately emerge from the spinal cord as components of these spinal nerves.
Preganglionic sympathetic fibres destined for the head are carried _____
out of the spinal cord in spinal nerve T1.
_______ _______ fibres destined for the ____ are carried out of the spinal cord in spinal nerve T1.
Preganglionic sympathetic; head
Fig. 3.13
Label the systematic image and caption it
- Paravertebral sympathetic trunk
- T1
- Spinal cord
- Spinal nerve
- L2
Sympathetic trunks
Fig. 3.13
Label the detailed image and caption it
- Gray ramus communicans
- Spinal cord
- Spinal nerve
- Thoracic sympathetic ganglion
- Sympathetic trunk
- White ramus communicans
Sympathetic trunks
Why is the thoracic wall expandable?
- most ribs articulate with other components of the wall by true joints that allow movement
- the shape and orientation of the ribs
(Fig. 3.14).
What is it about rib articulation that makes the thoracic wall expandable?
Most ribs articulate with other components of the wall by true joints that allow movement
What is it about the ribs themselves that makes the thoracic wall expandable?
The shape and orientation of the ribs
Fig. 3.14
Label and caption the image.
- Elevation of lateral aspect of ribs in inspiration
- Sternum moves forward in inspiration because of rib elevation
- Diaphragm descends to increase thoracic capacity in inspiration
Flexible thoracic wall and inferior thoracic aperture.
Which attachment of the rib is more superior?
The posterior attachment is more superior than the anterior attachment.
What occurs to the thoracic wall when a rib is elevated?
When a rib is elevated, it moves the anterior thoracic wall forward relative to the posterior wall, which is fixed.
Which part of the rib is inferior to the other?
The middle part of each rib is inferior to its two ends
What happens when the middle part of each rib is elevated?
When this region of the rib is elevated, it expands the thoracic wall laterally.
How does the volume of the thorax change vertically?
From the diaphragm, because it is muscular.
How does the thoracic wall change volume, and what is this important for?
- When ribs are elevated, the anterior thoracic wall moves forward relative to the fixed posterior thoracic wall
- The middle part of each rib is elevated, which is inferior to its two ends, expandind the thoracic wall laterally
- Muscular diaphragm allows change of volume in the vertical direction
Changes in the anterior, lateral and vertical dimensions of the thoracic cavity are important for breathing.
What is the diaphragm innervated by?
Two phrenic nerves, one on each side
Where do the phrenic nerves originate?
As branches of the cervical plexus in the neck on each side (Fig. 3.15).
Specifically where do the phrenic nerves arise?
From the anterior rami of cervical nerves C3, C4 and C5, with the major contribution coming from C4
Which is the major contribution to the phrenic nerve, from the cervical nerves?
C4
Fig. 3.15
Label and caption the image
- Right phrenic nerve
- Pericardial branch of phrenic nerve
- Diaphragm
- C3
- C4
- C5
- Left phrenic nerve
- Pericardium
Innervation of the diaphragm
Where do the phrenic nerves pass?
Vertically through the neck, the STA, and the mediastinum
What do the phrenic nerves supply?
Motor innervation to the entire diaphragm, including the crura
What are the crura?
Muscular extensions that attach the diaphragm to the upper lumbar vertebrae.
Where do the phrenic nerves pass in relation to the mediastinum?
In the mediastinum, the phrenic nerves pass anteriorly to the roots of the lungs.
Where are the tissues that initially give rise to the diaphragm?
These are in an anterior position on the embryological disc before the head fold develops
i.e. the tissue that gives rise to the diaphragm originates superior to the ultimate location of the diaphragm
Why is there a cervical origin of nerves that innervate the diaphragm?
The tissues that initially give rise to the diaphragm are in an anterior position on the embryological disc before the head fold develops, which explains the cervical origin of the nerves that innervate the diaphragm.
Spinal cord injuries ___ do not affect movement of the diaphragm
Spinal cord injuries below the level of the origin of the phrenic nerve do not affect movement of the diaphragm.
