Lung’s pleura

2 pleuras: continuous at hilum

• Parietal pleura –  lines inner surface of the thoracic cavity
• Visceral pleura – lines surface of lung

Pleural cavity: contains pleural fluid which lubricates lungs

4 parts of parietal pleura:

Pleural recesses:

Clinicals:

• Drain fluid – insert needle superior to rib
• Pleuritis
• Pancoast tumor – on lung apex, erodes 1st rib
• Pyothorax (pus), hemothorax (blood), pneumothorax (air), chylothorax (lymph) – collect in pleural cavity

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Lungs

Lung surfaces: Costal, mediastinal, diaphragmatic

Blood supply: Same as visceral pleura

Nerve: Same as visceral pleura

• Sympathetic trunk: Relax bronchial smooth muscle, vasoconstrict vessels
• Vagus: Contract smooth muscles, vasodilate

Bronchial tree: Trachea ⇒ Right and left bronchus ⇒ Lobar bronchus (3 right, 2 left) ⇒ Segmental bronchus ⇒ Interlobular bronchus ⇒ Terminal bronchiole ⇒ Respiratory bronchiole

Lymphatics: 

Bronchopulmonary segment:

Clinicals: Lung resection – remove specific tumor on segment

Apex of lung – relations:

• Anterior – subclavian artery, scalenus anterior, clavicle
• Posterior – posterior intercostal arteries and veins
• Lateral – 1st rib
• Medial – phrenic nerve, vagus nerve, trachea, esophagus
• Superior – brachial plexus

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Right and left lung differences:

Right – 10 segments, Left – 8 segments

Right and left bronchi:

• Right: Shorter, vertical, 3 divisions, enters lung at T5 level
• Left: Longer, horizontal, 2 divisions, enters lung at T6 level

Right and left hilum:

Right and left lung impressions:

Clinicals:

• Pulmonary embolism – dyspnea, chest pain, cough blood
• Clavicle fractures – damage apex of lungs
• Asthma
• Chronic bronchitis
• Cancer – smoking
• Cystic fibrosis
• Bronchoscopy
• Aspiration of foreign object usually in right principal bronchus as it shorter, wider and more vertical than left

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Pericardium

Attachments:

• Anterior – sternopericardial ligament, sternum
• Posterior – posterior mediastinum
• Superior – tunica adventia of great vessels
• Inferior – pericardiophrenic ligament
• Laterally – pulmonary vein adventia

Relations:

• Anterior – sternum, 2-6 costal cartilage
• Posterior – posterior mediastinum
• Superior – thymus, great vessels
• Inferior – pericardiophrenic ligament
• Laterally -phrenic nerve, lungs and pleura pericardiophrenic vessels

Layers:

• Fibrous – prevents over distension of heart
• Parietal – lines pericardium
• Visceral – called epicardium

Sinuses between parietal and visceral layer:

Blood supply:

• Internal thoracic artery – pericardiophrenic and musculophrenic arteries
• Thoracic aorta – bronchial, esophageal, superior phrenic
• Coronary arteries (visceral layer)

Venous:

• Pericardiophrenic – drains into internal thoracic artery
• Azygos venous system

Nerves:

• Fibrous and parietal layer – phrenic nerve, intercostal nerve
• Visceral layer – vagus and sympathetic trunk

Lymphatics: Parasternal, tracheobronchial

Functions of pericardium:

• Fix heart with sternopericardial ligament and pericardiophrenic ligament
• Prevent overfilling of heart
• Lubrication
• Protect from lung infection

Layers of heart wall:

• Fibrous
• Parietal
• Serous fluid
• Visceral/epicardium
• Subepicardial layer
• Myocardium – involuntary striated muscle (Clinicals: myocarditis, infarction)
• Subendocardial layer – Purkinje fibers and vessels
• Endocardium – lines heart cavities and valves (Clinicals: endocarditis)

Clinicals:

• Pericarditis
• Cardiac tamponade – compressed heart and veins
• Pericardial effusion – abnormal accumulation of fluid in the pericardial cavity
• Pericardiocentesis – aspiration of fluid from 5th and 6th intercostal space

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Heart

Divided into 1/3 right and 2/3 left by posterior interventricular sulcus, which contains posterior interventricular artery

Borders and surfaces of the heart:

Surface anatomy of the heart:

Blood supply:

Aortic sinus gives off right coronary artery and left coronary artery

Right coronary artery branches:

• Sino arterial nodal
• Right marginal
• AV nodal
• Posterior interventricular

Left coronary artery branches:

• Anterior interventricular
• Circumflex
• Left marginal (from circumflex)

As blood recoils during ventricular diastole, enters coronary arteries to supply heart

NB: Coronary dominance – The coronary artery that supplies SAN, can be right or left or both

Extracardiac anastomosis: Internal thoracic artery branches, bronchial, esophageal, superior and inferior phrenic arteries

Venous:

Coronary sinus:

• Runs in posterior coronary groove
• Opens in right atrium between AV orifice and IVC orifice
• Tributaries:

1. Great cardiac vein
2. Small cardiac vein
3. middle cardiac vein
4. Left marginal vein
5. Left posterior ventricular
6. Oblique vein of left atrium

Anterior cardiac veins open directly in right atrium

Lymphatics: Tunica media ⇒ Efferent vessels ⇒ tracheobronchial nodes

Nerves: Sympathetic increases heart rate, parasympathetic decreases

Sympathetic: Right and left cardiac branches of sympathetic ganglia

• Cervical: Superior, middle and inferior ganglia
• Thorax: Ganglia 2,3,4

Parasympathetic:

• Vagus: Right and left upper cervical cardiac branches, right and left lower cervical cardiac branches
• Left recurrent laryngeal – 1 branch

1. Superficial cardiac plexus – Below arch of aorta

• Left superior cervical sympathetic nerve
• Left lower cervical cardiac nerve (parasympathetic)

2. Deep cardiac plexus – infront of tracheal bifurcation

• All the remaining nerves mentioned above

Relations: Same as pericardium

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Interior of heart:

(I) Right atrium:

• Crista terminalis (contains SAN)/ Sulcus terminalis – divides atrium into smooth and rough part
• Sinus venarum – smooth – posterior part
• Atrium proper – rough – anterior part
• Pectinate muscles
• SVC, IVC, coronary and AV orifice

(II) Interarterial septum: Fossa ovalis and limbus

Clinicals: Patent foramen ovale

(III) Left atrium:

• Smooth  posterior part – absorbed pulmonary veins
• Rough anterior part – Pectinate muscles

(IV) Right ventricle: Divided into 2 by supraventricular crest

• Outflow part – Infundibulum, smooth walls
• Inflow part – Trabeculae carneae which consists of:

1. Ridges
2. Bridges (eg. moderator band)
3. Three Papillary muscles – attached to valves by chorda tendinea – prevents valve prolapse into atria during ventricular systole

(V) Interventricular septum: Superiorly membranous, inferiorly muscular

(VI) Left ventricle:

• Outflow part – Aortic vestibule, smooth walls
• Inflow part – Trabeculae carneae, 2 papillary muscles

Conducting system of the heart: 

Triangle of koch: In right atrium, anatomical landmark of AV node

Boundaries: Tendon of Todaro, tricuspid valve and coronary sinus opening

Clinicals:

• Myocardial ischaemia
• Angina pectoris
• Coronary bypass graft – radial artery and long saphenous vein
• Angiogram
• Cardiac referred pain – pain felt in the neck, shoulders, and back
• Heart block 1st, 2nd and 3rd degree

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Superior thoracic inlet

Boundaries:

• Anterior – Manubrium
• Posterior – T1 body
• Lateral – 1st rib and costal cartilage

Contents:

• Trachea, esophagus, thoracic duct
• Common carotid artery, subclavian artery and vein, IJV
• Vagus, phrenic, recurrent laryngeal nerves and sympathetic chain
• Apex of lung and pleura

Clinicals: Thoracic inlet syndrome – compression of structures, tumors, enlarged lymph nodes – leads to dysphagia, dyspnea

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Inferior thoracic inlet

Boundaries:

• Anterior – 7-10 costal cartilage, xiphisternal joint
• Posterior – T12 body
• Lateral – 11th and 12th ribs

Contents:

• Abdominal aorta
• Azygos vein
• IVC
• Esophagus
• Vagus nerve
• Thoracic duct

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Ribcage

(I) Costotransverse and costovertebral joints:

Costotransverse joint – Tubercle of rib articulates with transverse process of corresponding vertebrae

Costovertebral joint – Head of rib articulates with superior costal facet of corresponding vertebrae and inferior costal facet of the vertebra above, as well as the adjacent IVD

(II) Types of ribs:

(III) Typical rib:

• Anterior – Costal cartilage (hyaline)
• Posterior – Tubercle and head (2 articular facets)
• Superior – Thick and rounded
• Inferior – Sharp, costal groove

(IV) Atypical ribs:

(V) 1st rib relations:

• Superior – clavicle, subclavian vessels
• Inferior – intercostal vessels
• Medial – sympathetic trunk

(VI) Muscles:

1. Intercostal muscles:

• 11 pairs
• Nerve supply – intercostal nerves (T1-T11)
• Intercostal vein, artery and nerve between internal and innermost intercostal muscles

1. External – in inspiration elevate ribcage
2. Internal – forced expiration
3. Innermost – inspiration

2. Transverse thoracic muscles:

• From posterior inferior sternum to posterior surface of costal cartilage 2-6
• Depress ribs

3. Subcostal muscles:

• From posterior lateral rib to a 2nd or 3rd rib below
• Depress ribs

(VII) Muscles of respiration:

(VIII) Thoracic wall/ Ribcage:

1. Blood supply:

• Thoracic aorta – Posterior intercostals, subcostal artery
• Internal thoracic – Anterior intercostals
• Axillary – Superior and lateral thoracic arteries

2. Venous: Azygos system

3. Nerves:

• Supraclavicular nerve – above 2nd rib
• Anterior rami (T1-T11) intercostal nerves

4. Lymphatics: Intercostal, phrenic nodes

Clinicals:

• Age changes – costal cartilage ossify, xiphoid process ossify
• Paralysis of diaphragm, phrenic nerve damaged – paradoxical movement
• Extra ribs – transverse process of cervical or lumbar vertebrae
• Decreased ribs – failure of 12th rib to form
• Rib fracture – at angle or costal cartilage, most common in ribs 3-10 since they are immobile. 1st and 2nd are protected by clavicle, 11th and 12th are mobile.
• Flail chest – anterolateral chest wall movable due to multiple rib fractures. Moves paradoxically (moves outwards during expiration)
• Funnel chest 
• Pigeon chest
• Sternal puncture – to get bone marrow from manubrium, pierces skin, fascia and periosteum. May injure aorta, heart, or pericardium
• Median sternotomy – vertical incision along sternum for heart and lung surgeries

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Mediastinum

(I) Superior mediastinum:

Relations:

• Superior – Thoracic inlet
• Inferior – Inferior mediastinum
• Anterior – Manubrium
• Posterior – T1-T4
• Lateral – Lungs pleura

Contents: 

• Nerves: phrenic, vagus, recurrent laryngeal
• Vessels: SVC, thoracic duct, aorta, internal thoracic artery and vein
• Trachea, esophagus
• Thymus gland

(II) Anterior mediastinum:

Relations:

• Superior – Superior mediastinum
• Inferior – Diaphragm
• Anterior – Sternum
• Posterior – Pericardium
• Lateral – lungs pleura

Contents: Sternopericardial ligament, internal thoracic artery and branches, thymus gland

(III) Middle mediastinum:

Relations:

• Superior – Superior mediastinum
• Inferior – Diaphragm
• Anterior – Pericardium
• Posterior – Pericardium
• Lateral – lungs pleura

Contents: Heart, tracheal bifurcation, phrenic nerve, SVC, pulmonary artery, pulmonary vein, aorta

(IV) Posterior mediastinum:

Relations:

• Superior – Superior mediastinum
• Inferior – Diaphragm
• Anterior – Pericardium
• Posterior – T5-T12
• Lateral – lungs pleura

Contents: Thoracic aorta, thoracic duct, azygos system, esophagus

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Vessels and nerves

(I) Internal thoracic artery:

• Originates from 1st part subclavian artery
• Anterior to lung apex
• Enters thorax, posterior to clavicle
• Runs downwards and lateral to sternum
• At 6th intercostal space divides into: superior epigastric (rectus muscle) and musculophrenic (diaphragm)
• Branches: Anterior intercostal arteries, perforators of breast, pericardiophrenic and mediastinal

(II) Aortic arch: (connected to pulmonary trunk by ligament arteriosum)

Location: Sternal angle to lower border T4

Relations:

• Superior – Brachiocepahlic trunk, left common carotid, left subclavian artery
• Inferior – Pulmonary trunk
• Left/anterior – Pleura, phrenic nerve and vagus nerve
• Right posterior – trachea, esophagus

Branches: Brachiocepahlic trunk, left common carotid, left subclavian artery, right and left coronary arteries

(III) Thoracic aorta:

Location: Posterior mediastinum (T4-T12)

Relations:

• Anterior – Pericardium
• Posterior – Vertebral column
• Right – Thoracic duct, azygos vein
• Left – Left lung and pleura

Branches: Posterior intercostals, bronchial, esophageal, pericardial, mediastinal, superior phrenic, subcostal

(IV) Brachiocephalic trunk:

Location: Posterior to manubrium

Relations:

• Anterior – Manubrium
• Posterior – Trachea
• Right – SVC
• Left – Left common carotid

Branches: Right common carotid and right subclavian

(V) SVC:

Extent: 1st-3rd costal cartilage

Location: Anterior and right of superior mediastinum

Relations:

• Anterior – Ascending aorta, right lung
• Posterior – Trachea
• Lateral – Right lung and pleura

Tributaries: Right and left brachiocephalic veins, azygos vein, right and left supreme intercostal veins

(VI) Azygos venous system:

• Azygos vein formed from right subcostal vein and right ascending lumbar vein
• Hemiazygos and accessory hemiazygos drain into azygos vein
• Azygos vein enters thorax via aortic hiatus
• Ascends right of T12 – T4
• Drains into SVC

(VII) Thoracic duct: Main lymphatic trunk

• Continues as cisterna chyli in abdomen
• Enters thorax via aortic hiatus
• In posterior mediastinum, right to thoracic aorta snd posterior to esophagus
• Crossed from right to left at T4
• In superior mediastinum
• Joins junction of left IJV and left subclavian to form left brachiocephalic vein

Territory of drainage: all except superior right quadrant

Clinicals: Laceration – thin wall tears, chyle accumulates in posterior mediastinum

(VIII) Phrenic nerve:

• Origin: Anterior rami of C3,C4,C5
• Begins at lateral border of anterior scalene muscle
• Descends anterior to anterior scalene, deep to prevertebral layer

Right phrenic nerve:

• Passes anterior to 2nd part of subclavian artery
• Enters thorax via superior mediastinum
• Right side of brachiocephalic vein, SVC and pericardium
• Descends anterior to lung root
• Pierce diaphragm near caval opening

Left phrenic nerve:

• Passes anterior to 1st part of subclavian artery
• Enters thorax via superior mediastinum
• Crosses aortic arch and vagus nerve
• Descends anterior to lung root
• Pierce diaphragm

Phrenic nerve distribution:

• Motor and sensory – Diaphragm
• Sensory:

1. Parietal pleura
2. Parietal pericardium
3. IVC
4. Suprarenal glands
5. Biliary apparatus

Clinicals: Referred pain

(IX) Thoracic sympathetic chain:

• Runs over neck of ribs and transverse process of vertebrae
• Pierce diaphragm to supply abdomen

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Trachea, esophagus and thymus gland

Esophagus:

Constrictors: Cricopharyngeal sphincter, arch of aorta, left main bronchus, diaphragmatic constriction

Clinicals of esophagus: Cancer, compression due to right atrium hypertrophy – dysphagia

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Diaphragm

Attachments:

• L1 and L2
• 7-12 rib’s costal cartilage
• Xiphoid process of sternum
• Right (L1-L3) and left (L1-L2) crus – combine to form central tendon

Openings:

Blood supply:

• Internal thoracic – Pericardiophrenic, musculophrenic
• Thoracic aorta – Superior phrenic
• Abdominal aorta – Inferior phrenic
• Lower intercostal arteries

Nerves: Phrenic (motor), intercostal nerves and subcostal nerve (sensory)

Lymphatics: Parasternal, anterior and posterior diaphragmatic

Action: 

• Contract, flatten
• Relax, dome shaped

Functions of diaphragm:

• Muscle of inspiration – increase verticle diameter
• Muscle of abdominal straining – helps anterior abdominal muscles to contract, therefore raise intraabdominal pressure for micturition, defecation or parturition
• Weight lifting muscle
• Thoracoabdominal pump – as diaphragm increases intraabdominal pressure and decreases intrathoracic pressure, it compresses blood in IVC and forces it upwards. Thoracic duct also aided.

Relations:

• Superior – Pericardium, lungs
• Inferior – Liver, adrenals, kidney, stomach, spleen
• Posterior – Aorta, azygos vein, esophagus

Clinicals:

• Paralysis (suffocation)
• Hiccups  -involuntary contractions of diaphragm, irritation
• Referred pain – shoulder region
• Hiatal hernia – stomach enters thorax via th esophageal hiatus
• Median arcuate ligament syndrome – abdominal pain due to compression of celiac artery

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These are summarized notes from various sources, mainly TeachMeAnatomy and Wikipedia