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
A typical rib has
Head (two facets)
Neck
Tubercle (facet)
Angle
Proximal end- costal cartilage
Anterior articulations of ribs
Rib I to sternum (manubrium):
-fibrous joint- connected by fibrous tissue
- no movement
Ribs 2-7 true ribs:
-synovial (gliding) joints
-radiate sternocostal ligaments- fibrous bands that cross from sternal end of costal cartilage to ventral part of sternum
Ribs 8-10 false: articulate with costal cartilage of rib 7
Rib 11-12: false, floating ribs
Anatomical terminology in a typical rib
A rib makes contact with vertebrae 3 times:
Head (2 facets) connect to the vertebral column: one facet connects to superior vertebrae, other connects to inferior vertebrae
Tubercle (one facet) connects to transverse processes of the vertebrae column, this helps stabilise rib and rib cage
Proximal end of the rib connects to sternum via costal cartilage
Costal cartilage provides flexibility to the rib cage which is essential for movements in breathing
Subcostal groove- indentation of under surface of ribs caused by pulsating of intercostal arteries
Muscles of thoracic region that attach upper limb
These muscles associated with movements of upper limb:
Pectoralis major - attaches to both humerus and anterior body wall of thorax
Pectoralis minor- attaches to body wall and coracoid process of scapula
Subclavius
Serratus anterior
Latissimus dorsi
Rhomboid major
Rhomboid minor
Trapezius
Muscles of the scapula
Terres minor (rotation movement)
Terres major (major and minor attach scapula to humerus)
Deltoid
2 categories of muscles of thoracic region
Muscles that attach the upper limb to axial skeleton
Muscles of respiration
Actions of pectoralis major muscle
Fan shaped muscle
Attaches at clavicle, sternum and humerus
It’s a flexor of the arm, adductor of the arm
Clavicular part of pectoralis major:
-Elevates the shoulder
-Draws arm forward and medially
Sternocostal part of pectoralis muscle:
-Has same actions but also draws shoulder downwards
Serratus anterior
Serrated presentation
Attaches on: lateral surfaces of upper 8/9 ribs and deep fascia overlying the related intercostal spaces, costal surface of medial border of scapula
It is supplied by the long thoracic nerve (root values C5 to C7)
It’s actions are:
-protraction and rotation of the scapula
-keeps medial border and inferior angle of scapula opposed to thoracic wall
-winging of scapula- when long thoracic nerve comes to harm, the medial border and inferior angle of scapula is lost
Muscles of respiration
Intercostal muscles:
-External
-Internal (reinforced by ribs)
-Innermost
Transversus thoracis
Lavatores costarum
Grains of intercostal muscles run in different directions
Grain of internal and innermost are parallel to eachother but perpendicular to external muscle
Changing the grain of muscle fibres brings about strength
The different grains also allow intercostal muscles to perform inspiration and expiration
The neurovascular bundle of intercostal muscles
The neurovascular bundle of intercostal muscles runs on the inferior aspect of the ribs- sub-costal groove
They reside in between internal and innermost intercostal muscles
Vein, artery, nerve VAN
Any procedures on the thoracic wall must be carried out on the upper surface of the ribs
This avoids damage to the neurovascular bundle
Transversus thoracis muscles
Found on deep surface of anterior thoracic wall in same plane as innermost intercostals
Originate from posterior aspect of the xiphoid process, and the adjacent costal cartilages of the lower true ribs
They pass superiorly and laterally to insert into the lower borders of the costal cartilages of ribs III to VI. They most likely pull these latter elements inferiorly
Lie deep to internal thoracic vessels and secure these vessels into the wall
Surface features of pectoral region
External to anterior thoracic wall
Clavicle: subcutaneous, palpable
Sternum:midline
Suprasternal notch
Sternal angle
Nipple: in 4th intercostal space
Whats in pectoral region
Anchors upper limb to the trunk
Skin, superficial fascia containing mammary glands
Pectoral fascia, pectoral muscles
Separated into 4 quadrants: Upper inner, upper outer, lower inner and lower outer
L-mammae: mammary glands
Present in both sexes, well developed in females after puberty
Modified sweat gland (apocrine)
Accessory organ of female reproductive system
In superficial fascia except the axillary tail
Extent:
-vertical: from 2nd to 6th rib
-horizontal: lateral border of sternum to mid axillary line
-axillary tail of spence: passes through an opening in the deep fascia (foramen of Langer) and extends into axilla at level of 3rd rib
-tail is closely related to long thoracic nerve and axillary lymph nodes
Mammary bed: deep relations of mammary gland
Retromammary space (lake of Mercille) loose areolar (connective) tissue that separates breast from the pectoralis major muscle. Helps mobility of breast, space for implants, passage of vessels
Deep fascia covering pectoralis major muscle
Some part of Serratus anterior and external oblique abdominis muscle
Structure of the breast
Skin: nipple and areola
Parenchyma: compound tubule-alveolar gland, 15-20 lactiferous glands drain into nipple
Stroma: supporting framework, connective tissue and adipose tissue
Skin covering the breast
Nipple: conical projection at level of 4th intercostal space 10cm from midline. Pierced by 15-20 lactiferous ducts. Circular and longitudinal muscles in it, rich nerve supply
Areola: circular, pigmented area surrounding the nipple, modified sebaceous glands in this skin enlarge during pregnancy and lactation: tubercles of Montgomery. Lubrication prevents cracking. Lactiferous sinuses below the areola
No hair or subcutaneous fat underneath nipple and areola
Parenchyma
15-20 lactiferous lobules
Radially arranged, so radial incisions
Lactiferous sinuses: stores milk in lactating breasts
Lactiferous ducts: open separately on nipple
Glandular tissue is more in lactating breast
Myoepithelial cells
Connective tissue stroma
Breast support matrix
Inframammary ligament
Suspensory ligaments of Cooper: support and firmness
Adipose tissue:main bulk, interlobar in position, increase at puberty
Superficial and deep lymphatics mammary gland
Superficial lymphatics: skin except areola and nipple
Deep lymphatics: parenchyma, areola and nipple
Malignant cells can spread through lymphatics
Superficial lymphatics
UO: axillary and infraclavicular nodes
LO: axillary nodes
UI: parasternal and supraclavicular nodes
LI: parasternal, subdiaphragmatic nodes, subperitoneal lymph plexus
Deep lymphatics
Parenchyma: anterior axillary lymph nodes
Subareolar plexus of Sappey: nipple and areola: axillary LN
Deep connective tissue: parasternal, posterior intercostal and supraclavicular LN
Development of the mammary glands
Ectodermal
First appear as bilateral bands of thickened epidermis called mammary lines/ridges/ milk line. From axilla to groin
Polymastia
Having more than normal number of breasts. Supernumeracy breasts
Amastia
Absence of breast and nipple
Polythelia
Presence of additional nipples
Athelia
A condition where person is born without one or both nipples
Macromastia
Breast hypertrophy
Excessively large
Micromastia
Postpubertal underdevelopment of breast
Applied anatomy mammary glands
Well developed axillary tail shouldn’t be mistaken for lipoma (benign tumours of fat) or lump
Mastitis-infection of breast tissue
Breast abscesses: to drain incision should be radial to avoid injury to lactiferous ducts
Fibroadenoma: benign tumour, solid breast lump common in young women
Upper outer quadrant is common site for malignancy
Ca breast- breast cancer
Spread of cancer cells mammary gland
Suspensory ligaments: breast is fixed
Lactiferous ducts: retraction of nipple
Superficial lymphatic vessels: oedema: Peau d’orange sign- hair follicles buried in oedema
Axillary lymph nodes
Opposite breast
Sometimes to abdominal viscera
Screening for breast cancer
Mammogram
Self examination of breasts for early detection
Inspect: symmetry of breasts and nipples, change in colour of skin, retraction of nipple is sign of cancer, discharge from nipple on squeezing it
Palpate: all 4 quadrants with palm of hand, note any palpable lump, raise arm to feel lymph nodes in axilla
Modified radicle mastectomy
Removal of breast tissue and axillary lymph nodes
Parietal pleura
Endothoracic fascia separates the parietal pleura from body wall
Parts: cervical (cupula), costal, mediastinal and diaphragmatic
Cervical pleura is covered by suprapleural membrane
Limits expansion of lungs
Visceral pleura
Close to surface of lungs
Pleural reflections
Margin of lung :
Midclavicular line 6th rib
Midaxilalry line 8th rib
Paravertebral line 10th rib
Margin of pleura:
Mid clavicular line 8th rib
Midaxillary line 10th rib
Paravertebral line 12th rib
Pleural cavity and pleural recesses
Pleural cavity: thin film of fluid for reducing friction, 5-10 ml fluid
Pleural recesses are the reflection points where lung does not extend fully into pleural space
-Costodiaphragmatic recess
-costomediastinal recess
Nerve supply of the pleura
Parietal pleura: innervated by the somatic afferent nerves, sensitive to pain
So inflammation of the parietal pleura causes referred pain to the cutaneous distribution of these nerves i.e to the thoracic wall, neck or anterior abdominal wall
Visceral pleura: innervated by visceral nerves so it’s sensitive to stretch but insensitive to pain
Clinical anatomy of pleura
Normally the two pleural layers are in close apposition and the space between them is only a potential one
Accumulation of excessive fluid (pleural effusion)- no space for expansion lung
Air in pleural cavity (pneumothorax)
Blood (haemothorax)
Pus (empyema)
Lymph (chylothorax)
Drain excess pleural fluid
Triangle of safety: lateral edge of pectoralis major, base of axilla, lateral edge of latissmus dorsi, 5th intercostal space
Incision is made
Thoracostomy is a small incision of chest wall most commonly used for the treatment of pneumothorax
Lungs gross anatomy
Pair of respiratory organs
Surrounded by pleural sac and attached to mediastinum only by root of lung
Mediastinum is area between 2 lungs and pleura
Spongy
Lungs surface and borders
Apex
Base
2 surfaces: medial/mediastinum surface, lateral/costal surface
3 borders: anterior border :thin, straight, posterior border: rounded, inferior border: thin and c shaped
Hilum of lung
Point of entry on each lung for the bronchus, blood vessels (pulmonary arteries (deoxygenated) and veins (oxygenated)) , nerves and lymphatics
Visceral pleura is reflected as parietal here
In middle of lung
Root of lung
Short tubular collection of structures that connect lung to structures in mediastinum
Covered by sleeve of mediastinal pleura that reflects on lung surface as visceral pleura
Pulmonary ligament
Thin fold of pleura projects inferiorly from root of lung and extends from hilum to mediastinum
May stabilise position of inferior lobe and may accommodate the down and up translocation of structures in root during breathing
Lobes of lungs
Right lung has 3 lobes and 2 fissures: oblique fissure separates inferior from superior and middle lobes
Horizontal fissure separates superior from middle
Left lung is smaller and has 2 lobes separated by oblique fissure
The inferior portion of the medial surface of left lung is notched because of hearts projection into left pleural cavity from middle mediastinum. Cardiac notch
From the anterior border of lower part of superior lobe a tongue like extension (lingula of left lung) projects over heart bulge
Trachea
In the neck and superior mediastinum C6 to T4
Trachea is radiolucent as it contains air black on X-ray
May be compressed or displaced by pathological enlargement of neighbouring structures
Foreign bodies and aspirated material tend to pass into the right bronchus as its wider and more in line with trachea
Splits into bronchi at T4/T5
Right upper bronchus is wider and shorter
Bronchopulmonary segments
Smallest functionally independent unit of lung aerated by one tertiary bronchus
10BP segments on each side
Blood supply and lymphatic drainage of lungs
Bronchial arteries and bronchial veins
Pulmonary arteries carry deoxygenated blood to lungs and pulmonary veins carry oxygenated blood back to heart
Lymphatics are drained into tracheobronchial group of lymph nodes
Nerve supply of lungs
By pulmonary plexus
Sympathetic from upper thoracic spinal segments: bronchodilators
Parasympathetic by vagus bronchoconstrictor and secretomotor to glands
Respiratory epithelium
Ciliated pseudostratified columnar epithelium
Boundaries of the mediastinum
Superiorly: superior thoracic aperture
Inferiorly: diaphragm
Anteriorly: sternum
Posteriorly: thoracic vertebrae, vertebral column
Laterally: mediastinal pleura
Contents of the mediastinum
Thymus gland, pericardial sac, the heart, the trachea, major arteries and veins
Angle of Louis
Sternal angle/ manubriosternal angle
Leydigs plane: sternal angle to lower border of T4: divides the mediastinum into superior and inferior mediastinum
2nd rib articulation: helps in counting ribs
Arch of aorta starts and ends
Tracheal bifurcation
Azygous vein opens into SVC
Thoracic duct deviates to left
Bifurcation of pulmonary trunk
Divisions of mediastinum
Superior
Inferior:
Anterior -posterior to sternum, anterior to pericardial sac
Middle -pericardial sac and contents
Posterior- posterior to pericardial sac and diaphragm , anterior to vertebral column
Superior mediastinum
Phrenic and vagus nerves
Thoracic duct
Brachiocephalic veins
Superior vena cava
Arch of aorta
Thymus
Trachea
Lymph nodes
Oesophagus
Left recurrent laryngeal nerve
Anterior mediastinum
The thymus (may only be seen in children)
Loose areolar(connective) tissue
Sterno-pericardial ligaments (pass from posterior surface of body of sternum to fibrous pericardium)
Lymph nodes
Internal thoracic vessels
Middle mediastinum
Heart with the pericardium and roots of great vessels
Ascending aorta
Pulmonary trunk
Superior vena cava
Inferior vena cava
Pulmonary veins
Posterior mediastinum
Thoracic aorta- descending aorta and its branches
Azygous system of veins (drain blood from body walls and mediastinal viscera and empties it into SVC)
Thoracic duct
Oesophagus with vagus nerves (plexus)
Sympathetic trunk and thoracic splanchnic nerves (provide sympathetic supply to abdomen)
Outer fibrous Pericardium
Apex fused with outer connective tissue layer of great blood vessels (Adventitia)
Base fused with central tendon of diaphragm
Anteriorly it gives attachment to sterno-pericardial ligaments
Maintains central position of the heart
Prevents overdistension of heart
Serous pericardium: inner serous sac
Developing heart invaginates this serous sac
Parietal layer: close to fibrous pericardium, supplied by somatic nerves, sensitive to pain
Visceral layers: epicardium, supplied by visceral nerves, not sensitive to pain
Pericardial cavity
Between parietal and visceral layers
Contains thin film of serous fluid which allows friction free expansion
Pericarditis and pericardial effusion
Pericarditis: inflammation of the serous pericardium
Effusion: collection of excess fluid
Cardiac tamponade: compression- build up of fluid in pericardium resulting in compression of heart
Pericardiocentesis: drain the excess fluid
The heart
4 chambers
Atria: thin walled, receive blood
Ventricles: thick walled, pump blood into pulmonary or systemic circulation
Right atrium: receives deoxygenated blood from SVC, IVC and coronary sinus
Right ventricle: pumps blood in pulmonary trunk
Left atrium: receives oxygenated blood from pulmonary veins
Left ventricle: pumps blood into aorta
Heart surfaces and borders
Anterior surface (sternocostal): formed by right atrium, right ventricle and left ventricle, left atrium
Posterior surface (base): related with T5-8 vertebral bodies formed mainly by left atrium some part of right
Inferior surface (diaphragmatic): right and left ventricles
Right border: from SVC to IVC, formed by right atrium
Left border: formed by left atrium and left ventricle
Inferior border: IVC to apex, right and left ventricles
Apex: in left 5th intercostal space, 1-2cm medial to midclavicular line formed by left ventricle, here cardiac impulse can be felt as apex beat
Cardiothoracic ratio CTR
The ratio of the transverse heart dimension A to the maximum transverse dimensions of chest B
CTR= A/B
More than 0.5 is cardiomegaly
Blood supply of heart
Right and left coronary arteries: branches from aortic sinuses
Cardiac veins mainly drain into coronary sinus which will drain into the right atrium
Narrowing of the coronary vessels can cause angina or myocardial infarction
Coronary angiography can locate the narrowing/block
Lymphatics drain into brachiocephalic and tracheobronchial nodes
Mediastinum: clinical anatomy
Moveable partition: mediastinal shift
Mediastinitis: infections of neck can travel up to posterior mediastinum
Mediastinal syndrome: engorged veins, dysphagia (swallowing), dysphonia (speaking), dyspnoea (breathing)
Mediastinal widening
Cervical rib
Occurs in some people
If present may compress lower trunk of brachial plexus at superior thoracic aperture
International thymic malignancy interest group ITMIG
3 compartment cross sectional imaging model of the mediastinal compartments to diagnose mediastinal pathologies
Prevascular-anterior (anterior and superior)
Visceral- middle (middle and some part of posterior)
Paravertebral- posterior
Tissue layers of mediastinum
Fibrous pericardium
Parietal layer of serous pericardium
Pericardial cavity
Visceral layer of serous pericardium- epicardium
Myocardium- muscular component of heart
Endocardium- lines chambers
