Thorax Flashcards
What is the superior thoracic aperture
Narrow opening superiorly
Allows continuity with the neck
Consists of body of vertebra TI posteriorly, medial margin of rib I on each side and manubrium anteriorly
The superior margin of manubrium is ~ the same horizontal plane as intervertebral disc between TII and TIII
Plane of superior thoracic aperture is at an oblique angle
Structures that pass between upper limb and thorax pass over rib I and superior part of pleural cavity as they enter and leave mediastinum e.g. subclavian artery and vein
What is the inferior thoracic aperture
Large and expandable opening inferiorly
Closed by the diaphragm
Structures passing between abdomen and thorax pierce diaphragm or pass posteriorly
Skeletal elements of ITA:
Body of vertebra TXII posteriorly
Rib XII and distal end of XI posterolaterally
Distal cartilaginous ends of ribs VII to X which unite to form the costal margin anterolaterally
Xiphoid process anteriorly
When viewed anteriorly ITA is tilted superiorly
What is the thoracic cavity divided into
Left and right pleural cavity
Mediastinum
What is the mediastinum
Thick, flexible soft tissue partition oriented longitudinally in a median Sagittal position
Contains the heart, oesophagus, trachea, major nerves and systemic blood vessels
Acts as a conduit for structures that pass completely through thorax e.g. oesophagus, vagus nerves, thoracic duct, phrenic nerves
Extends from sternum to thoracic vertebrae and from STA to ITA.
A horizontal plane passing through sternal angle and intervertebral disc between TIV and TV separates it into superior and inferior parts
Inferior part is further divided by pericardium
Middle mediastinum= pericardium and heart
Anterior mediastinum= between sternum and pericardium
Posterior mediastinum= between pericardium and thoracic vertebrae
Pleural cavities
Completely separated from each other by mediastinum
Extend above level of rib, apex of each lung extends into neck
Each pleural cavity is lined by mesothelial membrane=pleura
Each lung remains attached to mediastinum by a root formed by airway, pulmonary blood vessels, lymphatic tissues and nerves
Pleura lining walls of cavity= Parietal pleura more superficial
On surface of lungs= visceral pleura
Functions of thorax
Breathing- up and down movements of diaphragm and changes in lateral anterior dimensions of thoracic wall caused by movements of ribs alter volume of thoracic cavity
Protection of vital organs: because of upward domed shape of diaphragm the thoracic wall also provides protection to some abdominal viscera- liver under right dome, stomach and spleen on left
What is the thoracic wall composed of
Posteriorly it’s composed of 12 thoracic vertebrae and their intervening intervertebral discs
Laterally wall is formed by ribs and 3 layers of flat muscles which span the intercostal spaces between adjacent ribs, move ribs and provide support for intercostal spaces
Anteriorly wall in made up of sternum, consists of the manubrium of sternum, the body of sternum and the xiphoid process
What is the sternal angle
The manubrium of sternum, angled posteriorly on the body of sternum at the manubriosternal joint forming sternal angle
Major surface landmark
Costal cartilage
The anterior end of each rib is composed of costal cartilage
Contributes to mobility and elasticity of wall
Articulation of ribs
Ribs II to IX have 3 articulations with vertebral column: head of each rib articulates with body of its own vertebra with body of one above, as these ribs curve posteriorly also articulates with transverse process of its vertebra
Anteriorly costal cartilages of ribs I to VII articulate with sternum
Costal cartilages of ribs VIII to X articulate with inferior margins of costal cartilages above them
Ribs XI and XII are floating ribs do not articulate with other ribs, costal cartilages or sternum, their costal cartilages are small
Joint between costal margin and sternum
Lies roughly in same horizontal plane as intervertebral disc between vertebrae TIX and TX
The diaphragm
Muscle fibres arise radially from margins of inferior thoracic aperture and converge into large central tendon
Because of oblique angle of ITA the posterior attachment of diaphragm if inferior to anterior attachment
Right dome is higher than left reaching up to rib V as diaphragm contracts height of domes decreases as volume of thorax increases
Oesophagus and inferior vena cava penetrate diaphragm and aorta pass posteriorly
Costodiaphragmatic recess
Lung doesn’t completely fill pleural cavity resulting in recesses, important for accommodating changes in lung volume during breathing
Largest and clinically most important recess, lies inferiorly between thoracic wall and diaphragm
What is the axillary inlet
Gateway to upper limbs
Formed by:
Superior margin of scapula posteriorly
Clavicle anteriorly
Lateral margin of rib I medially
The apex of each triangular inlet is directed laterally and formed by the medial margin of the coracoid process which extends anteriorly from superior margin of scapula
Proximal parts of the brachial plexus also pass between neck and upper limb through axillary inlet
Structures piercing diaphragm
Inferior vena cava pierces central tendon of diaphragm to enter right side of mediastinum near vertebral level TVIII
The oesophagus penetrates the muscular part of diaphragm to leave mediastinum and enter abdomen just to left of midline at TX
Aorta passes posteriorly at midline at vertebral level TXII
Relation between thorax and breast
Branches from internal thoracic arteries and veins perforate anterior chest wall on each side of sternum to supply anterior aspects of thoracic wall
Those branches associated with second to forth intercostal spaces also supply anteromedial parts of breast
Lymphatic vessels from medial part of breast accompany perforating arteries and drain into parasternal nodes on deep surface of thoracic wall
Vessels and lymphatics associated with lateral parts of breast emerge or drain into axillary region of upper limb
Lateral and anterior branches of 4th to 6th intercostal nerves carry general sensation from skin of breast
The horizontal plane passing through intervertebral disc between TIV and TV is most significant because
Passes through sternal angle anteriorly marking position of anterior articulation of costal cartilage of rib II with sternum
The sternal angle is used to find position of rib II as reference for counting ribs
Separates superior and inferior mediastinum and marks position of superior limit of pericardium
Marks where arch of aorta begins and ends
Passes through site where superior vena cava penetrates pericardium to enter heart
Level where trachea bifurcates into right and left main bronchi
Marks superior limit of pulmonary trunk
Venous shunts from left to right
Blood from left has to cross midline
In adults the left brachiocephalic vein crosses the midline immediately posterior to manubrium and delivers blood from left side head and neck, upper limb and part of left thoracic wall into superior vena cava
The hemiazygos and accessory hemiazygos veins drain posterior and lateral parts of left thoracic wall, pass immediately anterior to bodies of thoracic vertebrae and flow into azygos vein on right hand side which ultimately connects with superior vena cava
Neurovascular supply to thoracic wall
Arteries to the wall arise form two sources:
The thoracic aorta, in the posterior mediastinum
Pair of vessels - the internal thoracic arteries, run along deep aspect of anterior thoracic wall on either side of sternum
Posterior and anterior intercostal vessels branch segmentally from these arteries and pass laterally around wall mainly along inferior margin of each rib, running with these vessels are intercostal nerves (anterior rami of thoracic spinal nerves) which innervate the wall, related parietal pleura and associated skin
Innervation of the diaphragm
By 2 phrenic nerves that originate one on each side as branches of cervical plexus in neck. They arise from anterior rami of cervical nerves C3,4,5, major contribution from C4
The phrenic nerves pass vertically through neck, superior thoracic aperture and mediastinum to supply motor innervation to entire diaphragm, including crura (muscular extensions that attach diaphragm to upper lumbar vertebrae)
In mediastinum phrenic nerves pass anteriorly to roots of lungs
The pectoral region
External to the anterior thoracic wall and helps anchor the upper limb to the trunk
Consists of:
A superficial compartment contains skin, superficial fascia, breasts
A deep compartment containing muscles and associated structures
Nerves, vessels and lymphatics in the superficial compartment emerge from the thoracic wall, the axilla and the neck
What are mammary glands
Modified sweat glands in the superficial fascia anterior to the pectoral muscles and the anterior thoracic wall
Consist of a series of ducts and associated secretory lobules. These converge to form 15 to 20 lactiferous ducts which open independently onto the nipple .
The nipple is surrounded by a circular pigmented area of skin called areola
A connective tissue stroma surrounds the ducts and lobules of the mammary gland, in certain regions this condenses to form well defined ligaments- the suspensory ligaments of breast , which are continuous with dermis of skin and support breast
Tissues in the breast
In nonlactating women the predominant component of breast is fat
In lactating women its glandular tissue
The breast lies on deep fascia related to the pectoralis major muscle and other surrounding muscles
A layer of loose connective tissue ( the retromammary space) separates breast from deep fascia and provides some degree of movement over underlying structures
The base or attached surface of each breast extends vertically from ribs II to VI and transversely from sternum to as far laterally as the mid axillary line
Arterial supply of the breast
Laterally, vessels from the axillary artery- superior thoracic, thoraco-acromial, lateral thoracic and sub scapular arteries
Medially, branches from internal thoracic artery
The second to fourth intercostal arteries via branches that perforate thoracic wall and overlying muscle
Venous drainage of breast
Veins parallel the arteries and drain into axillary, internal thoracic and intercostal veins
Innervation of the breast
Nerve supply and control of lactation
Via anterior and lateral cutaneous branches of the fourth to sixth intercostal nerves, nipple and areola are highly sensitive to touch innervated by 4th intercostal nerve
Secretion/ lactation is regulated by hormones prolactin and oxytocin which are secreted from pituitary
Lymphatic drainage of the breast
~75% via lymphatic vessels that drain laterally and superiorly into axillary nodes
Most of the remaining drainage is into parasternal nodes deep into the anterior thoracic wall and associated with the internal thoracic artery
Some drainage may occur via lymphatic vessels that follow the lateral branches of posterior intercostal arteries and connect with intercostal nodes situated near the heads and necks of ribs
Where do axillary nodes drain into
Subclavian trunks,
parasternal nodes drain into the bronchomediastinal trunks intercostal nodes drain either into the thoracic duct or into the bronchomediastinal trunks
Breast in men
Rudimentary and consists only of small ducts, often composed of cords of cells, that normally do not extend beyond the areola
Staging the tumour means defining the
Size of the primary tumour
Exact site of primary tumour
Number and sites of lymph node spread
Organs to which the tumour may have spread
Muscles of the pectoral region
Each pectoral region contains the pectoralis major, pectoralis minor and subclavius muscles
All originate from the anterior thoracic wall and insert into bones of upper limb
Pectoralis major
Largest and most superficial of pectoral region muscles
Directly underlies breast and is separated from it by deep fascia and the loose connective tissue of the the retromammary space
Innervation by medial and lateral pectoral nerves
Function: Adduction, medial rotation, flexion of humerus at shoulder joint
Has a broad origin includes the anterior surfaces of the medial half of clavicle, the sternum, and first 7 costal cartilages
Muscle fibres converge to form a flat tendon which inserts into the lateral lip of the intertubercular sulcus of humerus
Subclavius and pectoralis minor
Underlie pectoralis major
The subclavius is small and passes laterally from the anterior and medial part of rib I to the inferior surface of clavicle
The pectoralis minor passes from the anterior surfaces of ribs III to V to the coracoid process of scapula
Both pull tip of shoulder inferiorly
A continuous layer of deep fascia= clavipectoral fascia encloses the subclavius and pectoralis minor and attaches to clavicle above and to floor of axilla below
Muscles of pectoral region form anterior wall of axilla
Nerves, vessels and lymphatics that pass between pectoral region and axilla pass through clavipectoral fascia between subclavius and pectoralis minor or pass under inferior margins of major and minor
Prominent features of chest wall anterior view
The clavicle
Roundedness of shoulders
Pectoralis major
Manubro-sternal joint- sternal angle (T4 T5 IVD)
Sternoclavicular joint
Nipples T4 Dermatome, typically 4th intercostal space
Sternum
Suprasternal notch/ jugular notch
Decreasing width of chest with fall in height
Intercostal spaces by surface palpation
Prominent features of chest wall posterior view
The scapulae: blades of scapulae, inferior angles of scapulae
Undulations of the vertebral column: knowledge of normal trajectory of central gutter is important, central gutter is indicative of locations of spinous processes of vertebrae
Back muscles
Vertebra prominens
Roundedness of shoulders
Decreasing width of chest with fall in height
What is the vertebra prominens
7th cervical vertebra
Long and prominent spinous process which is palpable from skin surface
Palpable structures of chest wall
T1- superior angle of scapula
T2- jugular/ suprasternal notch
T3- root of spine of scapula
T4/5 sternal angle; manubriosternal joint, trachea bifurcation
T7 inferior angle of scapula
T10 xiphoid process of sternum
Boundaries of thorax
Superior- superior thoracic aperture
Inferior- thoracic side/ upper part diaphragm
Antero-latero-posterior- ribs
Posterior- thoracic vertebrae
What is the jugular/ suprasternal notch
Also known as fossa jugularis sternalis
Occurs at T2
Large visible dip between neck and the two collar bones
Occurs at superior border of the manubrium of the sternum, between clavicular notches
Tissue layers of thorax from skin to parenchyma of lung
Skin
Superficial fascia and fat
Serratus anterior muscle
External intercostal muscle
Internal intercostal muscle
Innermost intercostal muscle
Endothoracic fascia
Parietal pleura
Pleural cavity
Visceral pleura
Lung
10 layers of tissues in chest wall
Skin
Superficial fascia
Pectoral fascia (deep fascia)
Pectoralis major muscle
Clavipectoral fascia (deep fascia)
Pectoralis minor muscle
External intercostal muscle
Internal intercostal muscle and ribs
Innermost intercostal muscle
Endothoracic fascia (or Transversalis fascia)
The two most superficial layers of fascia in thoracic wall
Known as fascia pectoralis
Made up of pectoral fascia and clavipectoral fascia
Superficial layer= pectoral fascia- covers outside of pectoralis major muscle, separates thoracic piece of pectoralis major from breast tissue which lies in superficial fascia
Deep layer= clavipectoral fascia- separates pectoralis major from minor, at top it’s fused with clavicle and coracoid process. In subclavian area from 2 sides surrounds a small chest muscle and subclavius muscle
Also goes on to form axillary= fascia axillaris
What is the deepest layer of fascia of thoracic wall
Endothoracic fascia
Endothoracic fascia
Deepest layer of fascia in thoracic region
A layer of loose connective tissue deep into intercostal spaces and ribs
Separates internal thoracic wall from underlying pleura
Forms outermost membrane of thoracic cavity
Bones of the thorax
Manubrium
Sternum
Xiphoid process
Coastal cartilages
Clavicles
Ribs - 12 pairs
Thoracic vertebrae -12
What are the atypical ribs
Rib I - widest, shortest, sharpest curve,flat in horizontal plane, slopes inferiorly to its attachment to manubrium has only one articular surface, superior surface of rib has tubercle- scalene tubercle which separates the two smooth grooves that cross rib midway along shaft
Rib II- flat but twice as long, articulates typically
Rib X-head of rib has a single facet for articulation with its own vertebra
Rib XI and XII- articulate only with body of own vertebrae have no tubercles or necks, both are short, little curve, pointed anteriorly
What are the two grooves on rib I caused by
Anterior groove is caused by subclavian vein
Posterior groove is caused by subclavian artery
