Podcast
Questions and Answers
Where does the thoracic duct pass through the diaphragm?
Where does the thoracic duct pass through the diaphragm?
What is the primary nerve responsible for diaphragm innervation?
What is the primary nerve responsible for diaphragm innervation?
Which artery directly branches from the thoracic aorta to supply the diaphragm?
Which artery directly branches from the thoracic aorta to supply the diaphragm?
In what vertebral level does the oesophagus pass through the diaphragm?
In what vertebral level does the oesophagus pass through the diaphragm?
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What structures are located within the right medial fissure of the diaphragm?
What structures are located within the right medial fissure of the diaphragm?
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What is the effect of the diaphragm contracting?
What is the effect of the diaphragm contracting?
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Which of the following veins does NOT contribute to the venous drainage of the diaphragm?
Which of the following veins does NOT contribute to the venous drainage of the diaphragm?
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Where is the aortic hiatus located relative to the arcuate ligaments?
Where is the aortic hiatus located relative to the arcuate ligaments?
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Which of the following structures receives lymph from the bronchopulmonary (hilar) nodes?
Which of the following structures receives lymph from the bronchopulmonary (hilar) nodes?
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What is the most common pathway for lymphatic drainage of the left lung, according to the provided information?
What is the most common pathway for lymphatic drainage of the left lung, according to the provided information?
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Which of the following body regions does the thoracic duct drain lymph from?
Which of the following body regions does the thoracic duct drain lymph from?
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Where should a stethoscope be placed to listen to breath sounds from the superior lobe of both lungs?
Where should a stethoscope be placed to listen to breath sounds from the superior lobe of both lungs?
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Which of the following is NOT a factor contributing to pulmonary embolism, according to Virchow's triad?
Which of the following is NOT a factor contributing to pulmonary embolism, according to Virchow's triad?
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What is the most common source of blood clots that cause pulmonary embolism?
What is the most common source of blood clots that cause pulmonary embolism?
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What is the medical term for a blood clot that forms in a deep vein, usually in the legs?
What is the medical term for a blood clot that forms in a deep vein, usually in the legs?
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Which of the following statements is TRUE regarding the lymphatic drainage of the right lung?
Which of the following statements is TRUE regarding the lymphatic drainage of the right lung?
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What is the name of the syndrome that can result from a Pancoast tumor?
What is the name of the syndrome that can result from a Pancoast tumor?
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Which of the following is NOT a symptom of Horner syndrome?
Which of the following is NOT a symptom of Horner syndrome?
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What is the primary function of the conducting zone of the respiratory tree?
What is the primary function of the conducting zone of the respiratory tree?
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Which of the following structures contains cartilage?
Which of the following structures contains cartilage?
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What is the name of the internal keel-like cartilage found at the bifurcation of the trachea?
What is the name of the internal keel-like cartilage found at the bifurcation of the trachea?
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What is the location of the bifurcation of the trachea?
What is the location of the bifurcation of the trachea?
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Which of the following statements about the right primary bronchus is TRUE?
Which of the following statements about the right primary bronchus is TRUE?
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In which segment of the right lung is an aspirated foreign body most likely to be found?
In which segment of the right lung is an aspirated foreign body most likely to be found?
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Which of the following heart surfaces is mainly composed of the right ventricle and a portion of the left ventricle?
Which of the following heart surfaces is mainly composed of the right ventricle and a portion of the left ventricle?
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What is the thickest layer of the heart wall?
What is the thickest layer of the heart wall?
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Which of the following structures forms the heart crown?
Which of the following structures forms the heart crown?
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What marks the boundary between the atria and ventricles?
What marks the boundary between the atria and ventricles?
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Which of the following structures is located on the right border of the heart?
Which of the following structures is located on the right border of the heart?
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What is the anatomical location of the apex of the heart?
What is the anatomical location of the apex of the heart?
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Which of the following is NOT a layer of the heart wall?
Which of the following is NOT a layer of the heart wall?
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Which of the following structures is part of the anterior surface of the heart?
Which of the following structures is part of the anterior surface of the heart?
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Which of the following is NOT a cyanotic heart defect?
Which of the following is NOT a cyanotic heart defect?
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The pericardial cavity is located between which two layers?
The pericardial cavity is located between which two layers?
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What is the primary function of the fluid within the pericardial cavity?
What is the primary function of the fluid within the pericardial cavity?
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Which of the following structures is NOT directly located within the middle mediastinum?
Which of the following structures is NOT directly located within the middle mediastinum?
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The oblique pericardial sinus is bounded on the right side by which structures?
The oblique pericardial sinus is bounded on the right side by which structures?
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What is the purpose of performing a pericardiacocentesis?
What is the purpose of performing a pericardiacocentesis?
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Cardiac tamponade is defined as:
Cardiac tamponade is defined as:
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What is the function of the pericardiacophrenic ligament?
What is the function of the pericardiacophrenic ligament?
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What is the correct name for the left atrioventricular valve?
What is the correct name for the left atrioventricular valve?
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Which structure connects the cusps of the bicuspid valve to the papillary muscles?
Which structure connects the cusps of the bicuspid valve to the papillary muscles?
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What is the fibrous structure that forms the skeleton of the heart and provides attachment for the valves?
What is the fibrous structure that forms the skeleton of the heart and provides attachment for the valves?
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What is the auscultation point for the aortic valve?
What is the auscultation point for the aortic valve?
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What is the first heart sound (S1) produced by?
What is the first heart sound (S1) produced by?
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What is the name for the condition that results from insufficient or stenotic heart valves, leading to abnormal heart sounds?
What is the name for the condition that results from insufficient or stenotic heart valves, leading to abnormal heart sounds?
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What is the primary function of the papillary muscles in the heart?
What is the primary function of the papillary muscles in the heart?
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Which of the following is NOT a fibrous structure found in the cardiac skeleton?
Which of the following is NOT a fibrous structure found in the cardiac skeleton?
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Flashcards
Caval opening
Caval opening
Opening in the diaphragm for inferior vena cava at vertebral level T VIII.
Oesophagus passage
Oesophagus passage
Oesophagus travels through the diaphragm near midline at vertebral level T X.
Aortic hiatus
Aortic hiatus
Aortic opening behind the middle arcuate ligament at vertebral level T XII.
Diaphragm arterial supply
Diaphragm arterial supply
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Diaphragm venous drainage
Diaphragm venous drainage
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Phrenic nerve function
Phrenic nerve function
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Diaphragm contraction
Diaphragm contraction
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Splanchnic nerves
Splanchnic nerves
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Pancoast tumour
Pancoast tumour
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Thoracic inlet syndrome
Thoracic inlet syndrome
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Horner syndrome
Horner syndrome
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Conducting zone
Conducting zone
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Respiratory zone
Respiratory zone
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Trachea
Trachea
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Right primary bronchus
Right primary bronchus
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Carina
Carina
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Congenital heart defects
Congenital heart defects
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Atrial septal defect
Atrial septal defect
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Ventricular septal defect
Ventricular septal defect
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Transposition of great vessels
Transposition of great vessels
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Persistent truncus arteriosus
Persistent truncus arteriosus
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Pericardium
Pericardium
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Pericardial cavity
Pericardial cavity
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Cardiac tamponade
Cardiac tamponade
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Bronchopulmonary nodes
Bronchopulmonary nodes
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Tracheobronchial nodes
Tracheobronchial nodes
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Bronchomediastinal nodes
Bronchomediastinal nodes
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Thoracic duct
Thoracic duct
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Right lymphatic duct
Right lymphatic duct
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Pulmonary embolism
Pulmonary embolism
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Virchow’s triad
Virchow’s triad
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Breath sounds locations
Breath sounds locations
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Anterior surface of the heart
Anterior surface of the heart
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Diaphragmatic surface of the heart
Diaphragmatic surface of the heart
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Right pulmonary surface of the heart
Right pulmonary surface of the heart
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Left pulmonary surface of the heart
Left pulmonary surface of the heart
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Borders of the heart
Borders of the heart
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Three layers of heart wall
Three layers of heart wall
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Heart apex location
Heart apex location
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Surface projections of the heart
Surface projections of the heart
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Bicuspid valve
Bicuspid valve
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Left ventricle function
Left ventricle function
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Trabeculae carneae
Trabeculae carneae
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Chordae tendineae
Chordae tendineae
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Papillary muscles
Papillary muscles
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Aortic vestibule
Aortic vestibule
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Heart sounds S1 and S2
Heart sounds S1 and S2
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Heart murmurs
Heart murmurs
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Study Notes
Thorax
- Netter's clinical Anatomy 2nd ed., J.T. Hansen Elsevier is a reference.
- Clinically oriented anatomy 6th ed. by K.L.Moore, A.F. Dalley, A.M.R. Agur LWW 2010 is a reference.
- Prometheus atlas of anatomy is a reference.
- Gray's Anatomy for students is a reference.
- Sobotta Atlas of human anatomy is a reference.
Skeleton of back and thorax
- Thoracic apertures
- Superior thoracic aperture is the base of the neck
- Posteriorly - Body of T1 vertebra
- Laterally - 1st pair of ribs
- Anteriorly - superior border of manubrium
- Conveys large vessels, nerves, thoracic lymphatic duct, trachea, and esophagus
- Inferior thoracic aperture
- Posteriorly - body of T12
- Posterolaterally - 11th and 12th pairs of ribs
- Anterolaterally - costal cartilages of ribs 7-10
- Anteriorly - xiphisternal joint
- Conveys inferior vena cava, aorta, esophagus, thoracic lymphatic duct
Mediastinum
- Thorax contains two pleural cavities and a central space called the mediastinum
- Superior mediastinum: Above an imaginary horizontal plane passing through the manubrium of the sternum
- Inferior mediastinum: Below the horizontal plane. further subdivided into anterior, middle (heart), and posterior sections
Thoracic Walls
- Topographic lines
- Anterior middle line
- Sternal line
- Parasternal line
- Midclavicular line
- Anterior axillary line
- Middle axillary line
- Posterior axillary line
- Scapular line
- Paravertebral line
- Posterior middle line
Muscles of thorax
- Pectoralis major
- Origins: medial half of clavicle, sternum and related costal cartilages
- Insertion: lateral lip of the intertubercular groove of humerus.
- Actions: adduction, flexion and medial rotation of the arm, elevation of the ribs (inspiration muscle)
- Innervation: lateral and medial pectoral nerves (C6 – T1)
- Subclavius muscle
- Origin: inferior surface of the shaft of clavicle
- Insertion: first rib
- Action: pulls the tip of the shoulder inferiorly
- Innervation: subclavian nerve (C5, C6)
- Pectoralis minor muscle
- Origin: costal cartilages of the muscles from 2nd to 5th
- Insertion: coracoid process of scapula
- Actions: pulls the tip of the shoulder inferiorly, elevating the ribs.
- Innervation: lateral pectoral nerve (C5 – C6)
- Serratus anterior muscle
- Origins: lateral parts of the ribs from 1st to 9th
- Insertions: medial border of the scapula
- Action: rotates the scapula, protracts scapula, elevates the glenoid cavity, holds the scapula against thoracic wall, elevates the ribs (inspiration muscle).
- Innervation: long thoracic nerve (C5, C6, C7)
- Levatores costarum muscles
- 12 fan-shaped muscles that elevate the ribs.
- Origin: transverse processes from T7 – T11
- Insertion: Post surface and angle of rib below.
- Action: Elevates ribs
- Nerve: Post primary rami C8 – T11
- Intercostal muscles (external and internal)
- External intercostal muscles
- Origin: Inferior border of the ribs; direction to the sternum
- Insertion: Superior border of the ribs
- Action: elevate the ribs during inspiration
- Innervation: intercostal nerves
- Internal intercostal muscles
- Origin: Inferior border of the ribs; direction toward the sternum
- Insertion: Superior border of the ribs
- Action: depress the ribs during expiration
- Innervation: intercostal nerves
- External intercostal muscles
- Internal innermost intercostal muscles
- Origin: Inferior border of the ribs; direction toward the sternum
- Insertion: Superior border of the ribs; outside the subclavian groove.
- Action: depress the ribs during expiration
- Innervation: intercostal nerves
Thoracic Walls (additional info)
- Subcostal muscles: Origin: Internal surface of the lower ribs near their angles. Insertion: Superior border of the 2nd or 3rd ribs below. Action: depress the ribs during expiration. Innervation: intercostal nerves.
- Transverse thoracic muscle: Origin: Posterior surface of the lower sternum. Insertion: Internal surface of costal cartilages from 2nd to 6th. Action: depress the ribs during expiration. Innervation: intercostal nerves
Diaphragm
- Flat muscle separating the thorax and abdomen.
- Attached peripherally to the xiphoid process of sternum, costal arches, floating ribs (XI, XII) and lumbar vertebrae (L1-L3)
- Fibers converge to the central tendon where pericardium is attached
- In the midsagittal plane, it slopes inferiorly.
Structures travelling between the thorax and abdomen
- Structures pass through the diaphragm or between the diaphragm and its peripheral attachments, In the central tendon there is the caval opening which provides inferior vena cava of vertebral level T VIII. The esophagus passes through the muscular part of the diaphragm, just to the left of midline, approximately at vertebral level TX, along with vagus nerves.
Arterial supply to the diaphragm
- Pericardiacophrenic and musculophrenic arteries - branches of internal thoracic arteries.
- Superior phrenic arteries arise directly from the thoracic aorta.
- Small branches from the intercostal arteries contribute to the supply.
- Inferior phrenic arteries branch directly from the abdominal aorta.
Venous drainage of the diaphragm
- Veins generally parallel to the arteries.
- Drain into the brachiocephalic veins in the neck.
- Drain into the azygos system of veins.
- Drain into abdominal veins (left suprarenal vein and inferior vena cava)
Innervation of the diaphragm
- Innervated by phrenic nerves (C3 to C5).
- The phrenic nerves penetrate the diaphragm and innervate from its abdominal surface.
- Contraction of the diaphragm domes flattens the diaphragm, increasing thoracic volume. Diaphragmatic movements are essential for normal breathing.
Arteries of the thoracic wall
- Anterior wall:
- Internal thoracic artery (branch of the subclavian artery)
- Anterior intercostal arteries (I – VI)
- Musculophrenic artery
- Superior epigastric artery
- Pericardiacophrenic artery
- Lateral thoracic artery (from axillary artery)
- Superior thoracic artery (from axillary artery)
- Superior intercostal artery (from costocervical trunk of subclavian artery)
- Posterior wall
- Posterior intercostal arteries (I – XI)
- Subcostal artery
Veins of the thoracic wall
- Anterior intercostal veins drain into the internal thoracic vein and its tributaries (superior epigastric vein and musculophrenic vein).
- Posterior intercostal veins drain into the subclavian vein (right side) and hemiazygos vein (left side).
Nerves of the thoracic wall
- Intercostal nerves (I to XI) and subcostal nerve are anterior branches of the thoracic spinal nerves.
- They innervate intrinsic muscles of the thorax, skin of the anterior thoracic wall and mammary gland, and parietal (costal) pleura.
- Intercostal neurovascular bundle running in the costal groove and consist of: intercostal vein, artery, nerve (VAN)
Thoracic wall puncture
- Intercostal nerve block
- Needle introduced to contact lower border of rib.
- Withdrawn slightly, directed caudally advanced 1/8 inch.
- To slip under rib and enter intercostal space.
- To avoid pneumothorax, aspirate before injecting anesthetic.
Breast
- Female breast extends from 2nd to 6th rib and from parasternal to midaxillary line.
- Mammary tissue composed of 15-20 lobes separated by connective tissue septa.
- Breast - fatty tissue containing glands that produce milk; lies in the superficial fascia, which lies above the deep pectoral fascia, enveloping the pectoralis major muscle.
- Areola: pigmented skin surrounding the nipple.
- Nipple: site of opening for the lactiferous ducts at the level of 4th intercostal space.
- Axillary tail: extension of mammary tissue superolaterally toward the axilla.
- Deep pectoral fascia: envelopes the pectoralis major muscle.
- Lobules of mammary gland (lactating): contained within the breast tissue.
- Fat lobule : fat tissue within the breast tissue.
- Lactiferous ducts: transport milk.
- Lactiferous sinus: storage area for milk.
Breast (additional info)
- Cooper ligaments: suspensory ligaments attaching the mammary gland to the skin and deep fascia.
- Tumor distortion of Cooper ligaments can cause dimpling of the skin (orange peel appearance)
- Long thoracic nerve damage during procedures like radical mastectomy - resulting in wing scapula and weakness in abduction of the arm above 90 degrees.
- Thoracodorsal nerve injury during mastectomy – resulting in weakness of extension and medial rotation of the arm.
- Arterial supply: internal thoracic artery (internal mammary) and lateral thoracic artery (branch of axillary artery).
- Venous drainage into internal thoracic vein and lateral thoracic vein.
- Lateral drainage: most lymph from the lateral, superior, and inferior quadrants drains to the axillary nodes, especially the pectoral group.
- Medial drainage: most lymph drains to the parasternal nodes, which lie along the internal thoracic vessels.
Lower respiratory development complications
- Pulmonary hypoplasia or aplasia: Incomplete development of lung tissue, characterized by a reduction in the number of lung cells, airways, and alveoli. This results in a smaller organ size and weight.
- Can be unilateral or bilateral.
Pleura and pleural cavity
- Parietal pleura: Lines the inner surface of the chest wall, diaphragm, and mediastinum. Divided into costal, diaphragmatic, and mediastinal parietal pleura (dome of pleura/pleural cupola)
- Visceral pleura: Adheres to and covers the lung.
- Pleural cavity: potential space between parietal and visceral pleura. Contains serous fluid lubricating opposing layers.
Pleura and pleural cavity (additional info)
- Innervation of parietal pleura: intercostal nerves (costal pleura), phrenic nerve (central portion of the diaphragmatic pleura and mediastinal pleura).
- Innervation of visceral pleura: visceral sensory nerves accompanying autonomic nerves.
Pleural Cavity
- Potential space between parietal and visceral layers of the pleura.
- Contains serous fluid that lubricates layers aiding in lung movement, respiration and breathing.
- Introduction of air into the pleural cavity causes lung collapse, resulting in pneumothorax.
Pneumothorax
- Open pneumothorax: occurs when a pneumothorax is associated with a chest wall defect thus communicating with the exterior.
- Pathophysiology: during inspiration, air is entrained into the chest cavity not through the trachea, but through the chest wall defect resulting in less resistance to flow which leads to inadequate oxygenation and progressive build up of air within the pleural space.
Pneumothorax (additional information)
- Tension pneumothorax: progressive build up of air in the pleural space; usually due to lung laceration; air escapes into the pleural space, but not to return, creating a one-way valve effect.
- Build up of pressure pushes the mediastinum to the opposite hemithorax and obstructs venous return to heart; leading to circulatory instability and traumatic arrest. This results in clinical findings: deviation of the trachea away from the affected side, hyper-expanded chest.
- Increased percussion note and little movement with respiration. Central venous pressure is usually raised, but can be normal or low in hypovolaemic states.
Lungs
- Surfaces and regions
- Costal surface
- Mediastinal surface (contains cardiac impression and root of the lung).
- Diaphragmatic surface (base)
Lungs (additional info): Lobes and fissures
- Right lung: 3 lobes (superior, middle, inferior) separated by oblique and horizontal fissures.
- Left lung: 2 lobes (superior, inferior) separated by oblique fissures; lingula of the upper lobe equivalent to the middle lobe of the right lung.
- Right lung is slightly larger than left due to the cardiac impression on the left.
- Superior lobe of the right lung projects to the chest wall above the 4th cartilage and the middle lobe projects anteriorly below the 4th rib.
- Almost entire inferior lobe projects to the posterior chest wall, with the small portion anteriorly below the 6th cartilage.
- Horizontal fissure is present only on the right lung along the 4th rib.
- Oblique fissure extends from T2 to the 6th costal cartilage and is present on both lungs.
- Impressions are made by adjacent structures.
- Hilum is where structures enter or exit the lungs (bronchi, pulmonary artery, pulmonary veins, bronchial arteries and veins, autonomic nerves, and lymphatics).
Lungs (additional information): Additional features
- Lingula: tongue-shaped feature of the left lung.
- Cardiac notch: irregularity in the anterior margin of the left lung.
- Pulmonary ligament: hangs up from the root and directs the visceral pleura into parietal pleura, created by the double layer of parietal pleura. Each lung has 10 bronchopulmonary segments (supplied by segmental bronchus, artery and vein for pulmonary circulation).
Lung Circulation
- Lungs have double circulation (systemic and pulmonary circulation)
- Systemic circulation is provided by the pulmonary artery (from the pulmonary trunk).
- Pulmonary veins superior and inferior,
- Nutrient circulation is provided by the bronchial arteries (anterior from the internal thoracic artery and posterior from the thoracic aorta).
- Bronchial veins (drainage of blood into the internal thoracic vein, brachiocephalic vein tributary and posterior into azygos veins).
Lung Innervation
- Lungs are innervated by autonomic nerves coming from two sources - sympathetic trunk (thoracic part) for bronchodilators muscles and parasympathetic fibres from vagus nerves (increasing mucus secretion and bronchoconstrictors muscles).
Lymphatic Drainage of the Lungs
- Drains by way of superficial and deep plexuses.
- Superficial plexus – placed immediately under the visceral pleura.
- Deep plexus is placed deep within the lungs and drains through pulmonary lymph nodes.
- Major nodes involved: bronchopulmonary (hilar) nodes, tracheobronchial nodes, and bronchomediastinal nodes on the right and left side of the trachea draining to the right lymphatic duct and thoracic ducts.
Lymphatic Drainage
- Left lung lymph drains to the right bronchomediastinal lymphatic trunk and nodes, then to the right lymphatic duct.
- This is the most important analysis of the metastases of lung cancer.
Thoracic Duct
- Carries lymph from the inferior part of the body (under the diaphragm: lower limbs, pelvis, abdomen) and left side of the superior part of the body (left superior limb, left half of the thorax, and left half of the head).
Breath Sounds
- Superior lobe of both lungs: place stethoscope on the superior area of the anterior chest above 4th cartilage.
- Middle Lobe of Right Lung: anterior chest wall, inferior to the 4th cartilage.
- Inferior lobes of both lungs: posterior chest wall
Pulmonary Embolism
- Pulmonary embolism is when one or more pulmonary arteries in your lungs become blocked.
- Most commonly caused by blood clots that travel to the lungs from the legs (deep vein thrombosis).
- Causes are called Virchow's triad: venous stasis, trauma, and coagulation disorders.
- Pulmonary embolism can be life-threatening.
Lung Cancer
- Bronchogenic tumor may impinge adjacent structures.
- Pancoast tumor arises in the lung apex and invades the surrounding soft tissues.
- May result in thoracic-inlet syndrome: injuries to the subclavian vessels and brachial plexus, nerve palsy (most often C8-T1 roots, ulnar or Horner's syndrome).
- Symptoms: miosis (constricted pupils), ptosis (minor drooping of the upper eyelid), anhidrosis (lack of sweating), and flushing (subcutaneous vasodilation).
Respiratory Tree
- Conducting zone: nose, pharynx, trachea, bronchi, bronchioles, and terminal bronchioles
- Cartilage present only in trachea and bronchi.
- Warms, humidifies, and filters air.
- Anatomical dead space.
- Conducting airways contain smooth muscle.
- Respiratory zone: respiratory bronchioles, alveolar ducts, and alveoli.
- Participates in gas exchange.
Trachea
- Single airway tube starting at level of cricoid cartilage to its bifurcation at T4, sternal angle of Louis.
- 16-20 C-shaped cartilages connected by annular ligaments.
- Anterior to the esophagus, and posterior to the aortic arch.
- Carina: internal keel-like cartilage at bifurcation.
- Posterior wall composed of membranous wall, created by longitudinal and circular muscular fibers, making up tracheal muscles.
Bronchi
- Aspiration of a foreign body more commonly occurs in the right primary bronchus because of shape differences.
- Right bronchus shorter, wider, and more vertically located than the left.
- Foreign body usually lodged in the posterior basal segment of the right inferior lobe.
- Main bronchi (primary - divide into lobar/secondary (2 or 3) - divisional bronchi (tertiary for 10 bronchopulmonary segments).
- Bronchi and respiratory airways continue to divide until reaching the alveolar sacs
Fetal Circulation
- Oxygenated blood from placenta to fetus passes through the umbilical vein.
- Three vascular shunts develop in the fetal circulation: ductus venosus, foramen ovale, and ductus arteriosus.
- Ductus venosus: Bypass of the liver sinusoids into the inferior vena cava.
- Foramen ovale: Allows oxygenated blood to bypass pulmonary circulation in the right to left direction.
- Ductus arteriosus: Shunts deoxygenated blood from pulmonary trunk to the aorta to bypass pulmonary circulation.
- Right to left pressure gradient facilitates blood passing through the foramen ovale and ductus arteriosus.
Postnatal Circulation
- Change in pressure gradient causes the shunts (foramen ovale, ductus arteriosus) to close.
- Foramen ovale closure due to increased left atrial pressure and reduced right atrial pressure.
- Ductus arteriosus closure due to the contraction of smooth muscles in its walls (oxygen tension)
Fetal Circulation remnants
- Medial umbilical ligaments - after closure of umbilical arteries.
- Ligamentum teres of the liver - after closure of umbilical vein
- Ligamentum venosum - after closure of ductus venosus
- Fossa ovalis - after closure of foramen ovale
- Ligamentum arteriosum - after closure of ductus arteriosus
Atrial Septal Defect (ASD)
- Congenital heart defect more common in females.
- Result in left to right shunting and non-cyanotic conditions.
Ventricular Septal Defects (VSD)
- Membranous VSD results in left-to-right shunting of blood.
- Patients complain of excessive fatigue upon exertion.
- It is not a cyanotic condition but causes increased blood flow and pressure to the lung (pulmonary hypertension), which in result provides to proliferation of the tunica intima in pulmonary muscular arteries.
- Pulmonary resistance is higher than systemic. This results in right-to-left shunting, which is already cyanotic, and development of Eisenmenger complex.
Patent Ductus Arteriosus (PDA)
- Ductus arteriosus fails to close after birth.
- In fetal period, shunt is right to left.
- In neonatal period, lung resistance decreases, and it becomes left-to-right (from the aorta to the pulmonary trunk), and is not cyanotic.
- Infants may present with a “machine-like” murmur.
- Patency maintained by prostaglandin E2 (PGE2) synthesis and low oxygen tension.
- PDA may be intentionally kept open in some heart defects, such as transposition of great vessels, with prostaglandin E2 administration.
- Endomethacin, acetylcholine, histamine, and catecholamines end PDA patency.
Tetralogy of Fallot
- Most common cyanotic congenital heart defect.
- Pulmonary stenosis.
- Right ventricular hypertrophy.
- Overriding of aorta (receives blood from both ventricles).
- Ventricular septal defect (membranous).
Transposition of Great Vessels
- Occurs due to failure of aortopulmonary septum to spiral.
- Most infants die within the first few months of life without surgical correction.
- Aorta arises from the right ventricle and pulmonary trunk arises from the left ventricle.
- Right-to-left shunt and cyanosis.
- Not compatible with life unless a shunt is present to allow adequate mixing of blood (e.g., VSD, PDA, patent foramen ovale.)
Persistent Truncus Arteriosus
- Partial development of aorticopulmonary septum
- Results in a single vessel leaving the heart that receives blood from both the right and the left ventricles.
- Right-sided shunt causes cyanosis.
- Always accompanied by membranous VSD.
Heart
- Middle mediastinum, containing pericardium, heart, great vessels (ascending aorta and pulmonary trunk), and phrenic nerves.
- Fibrous pericardium is the outer layer lined by serous pericardium which adheres directly to the heart as visceral layer.
- Pericardial cavity contains a little amount of fluid facilitating heart movement and beat.
Heart (Additional Information)
- Pericardial sinus: transverse sinus (passage between the anterior walls of the atria and the posterior walls of the aorta and pulmonary trunk), and oblique sinus (passage limited to superior vena cava and right pulmonary veins inferiorly and superiorly and left pulmonary veins inferiorly and superiorly).
Heart Wall Structure
- Three layers: Endocardium (innermost layer), Myocardium (middle, thickest layer), Epicardium (outermost layer).
Heart Wall
- Composed of three muscular layers: external oblique, intermediate circular, and internal longitudinal.
Heart
- Position: Lies at the level of T6-T9 vertebrae posterior to the superior part of the chest on the right side.
- Basis: forms the heart crown, including origins of the great vessels.
- Apex: mainly formed by the left ventricle, posterior to the left fifth intercostal space and medially to the midclavicular line.
- Atria and ventricles are demarcated by anterior and posterior interventricular grooves.
Heart surfaces
- Anterior (sternocostal surface): predominantly right ventricle, right atrium, and a portion of the left ventricle with the apex, ascending aorta, superior vena cava (SVC), and pulmonary trunk.
- Diaphragmatic (inferior) surface: largely left ventricle and partly the right ventricle, the right atrium with the termination of the inferior vena cava (IVC), and related to the central tendon.
- Right pulmonary surface: chiefly the right atrium.
- Left pulmonary surface: primarily the left ventricle, which forms the cardiac impression in the left lung.
Heart Borders
- Right border: right atrium between the superior and inferior vena cava (SVC and IVC)
- Inferior border: right ventricle and left ventricle.
- Left border: left ventricle and left auricle.
- Superior border: both atria and auricles; ascending aorta; and pulmonary trunk.
Heart Chambers
- Right atrium: receives blood from superior vena cava (SVC), inferior vena cava (IVC), and coronary sinus.
- Right auricle: muscular pouch projecting from the right atrium that increases its capacity, derived from the fetal atrium.
- Anterior muscular wall is formed from pectinate muscles.
- Sinus venarum: a smooth-walled portion of the atrium formed from the openings of the SVC and IVC.
Right Atrium
- Crista terminalis: Crest that separates the smooth part from the rough part of the right atrium. Extends longitudinally from the openings of the inferior vena cava (IVC) and superior vena cava (SVC).
- The sinoatrial (SA) node is located in the upper portion of the crista terminalis.
- Fossa ovalis: Remnant of the foramen ovale, present in fetal circulation.
- Tricuspid valve communicates with the right ventricle.
Right Ventricle
- Creates a large part of the anterior surface of the heart.
- Superiorly tappers into the conus arteriosus, leading into the pulmonary trunk.
- Interior ridges (trabeculae carneae).
- Papillary muscles: project into the ventricular cavity and attach to the cusps of the atrioventricular (AV) valve (tricuspid valve in the right ventricle) via chordae tendineae.
Right Ventricle (Additional Information)
- Anterior papillary muscle: the largest one, arises from the anterior wall, and its tendinous cords attach to the anterior and posterior cusps of the tricuspid valve.
- Posterior papillary muscle: smaller muscle with several parts, arising from the posterior wall. Its cords (chordae tendinae) connect to the posterior and septal cusps.
- Septal papillary muscle: arises from the interventricular septum and its chordae tendinae attach to the anterior and septal cusps of the tricuspid valve.
Right Ventricle (Additional Information)
- Interventricular septum (IVS): thicker muscular part and a thinner membranous part; forms the wall of each ventricle. Septal cusp of the tricuspid valve attaches to the membranous part of the septum.
- Septomarginal trabecula: muscular bundle that traverses the right ventricle from the lower part of the IVS to the base of the anterior papillary muscle. Contains the right bundle branch of the atrioventricular bundle (AV bundle), which carries its part.
Left Atrium
- Creates the base of the heart.
- Right and left pulmonary veins (superior and inferior) drain oxygenated blood from the lungs.
- Tubular muscular left auricle with a trabeculated wall and pectinate muscles.
- The bicuspid (mitral) valve lies between the left atrium and left ventricle at the left atrioventricular orifice.
Left Ventricle
- Blood enters the left ventricle through the mitral (bicuspid) valve.
- Blood is pumped out to the aorta.
- Trabeculae carneae are usually thicker than in the right ventricle.
- Papillary muscles (anterior and posterior): are attached to cusps of the bicuspid valve.
- Chordae tendineae: Connect papillary muscles to the posterior and septal cusps.
- Aortic vestibule: Leads to the aortic semilunar valve.
Cardiac Skeleton and Valves
- Heart has 4 valves attached to fibrous rings of dense collagen forming the fibrous skeleton of the heart.
- Created by fibrous rings (right and left atrioventricular valves and aortic and pulmonary rings for semilunar).
- Fibrous trigons (left and right), tendon of infundibulum, and membranous part of IVS.
Cardiac Skeleton and Valves (additional info)
- Valves:
- Right atrioventricular (tricuspid): Auscultation point - 5th intercostal space on the right/left sternal line
- Left atrioventricular (bicuspid/mitral): Auscultation point - 5th intercostal space on the left midclavicular line
- Aortic valve: Auscultation point - 2nd intercostal space on the right sternal line.
- Pulmonary valve: Auscultation point - 2nd intercostal space on the left sternal line.
- Heart sounds - first sound (S1) results from closing atrioventricular valves, second sound (S2) is from closing of aortic and pulmonary valves.
- Heart Murmurs are a heart disease that results from insufficiency and stenosis of valves.
Coronary Arteries
- Coronary arteries arise from the aortic sinuses (right and left) of the ascending aorta.
- Blood flow into the coronary arteries occurs during diastole
- Right coronary artery courses through the coronary sulcus supplying major parts of the right atrium and right ventricle.
- Major branches: sinoatrial (SA) nodal, right marginal, and posterior interventricular (posterior descending) and atrioventricular (AV) nodal.
- Left coronary artery: travels between the left auricle and the left ventricle dividing into 2 branches, Left anterior descending (LAD) artery and circumflex artery.
Coronary Arteries (Additional Information)
- Left anterior descending (LAD) artery descends within the anterior interventricular groove, supplying the anterior left ventricular wall, anterior two-thirds of the interventricular septum, the bundle of His, and the apex.
- The circumflex artery courses around the left border of the heart in the coronary sulcus and supplies the left border of the heart by marginal branches to the posterior aspect. Supplies the posterior-inferior wall of the left ventricle and posterior-inferior aspect of the left ventricular wall.
Coronary Occlusion
- Myocardial infarction (MI) commonly associated with; LAD occlusion (50% of cases), right coronary artery occlusion (30% of cases), and circumflex artery obstruction (20% of cases).
Cardiac Veins
- Venous drainage of the heart by veins that accompany the arteries.
- Coronary sinus: Largest coronary vein, lies in the posterior coronary sulcus, drains into the right atrium.
- Great cardiac vein: anterior interventricular groove with the left anterior descending (LAD) artery, drains into coronary sinus.
- Middle cardiac vein: posterior interventricular groove with the posterior interventricular artery; drains into coronary sinus.
- Venae cordis minimae (Thebesian veins) and anterior cardiac veins open directly into the heart chambers.
Cardiac Conduction System
- Created by specialized cardiac muscle cells and fibers (not by nervous tissue).
- Initiates and conducts impulses rapidly.
- Components: SA node, AV node, AV bundle (bundle of His), and Purkinje fibers.
Cardiac Conduction System (Additional Information)
- SA (sinoatrial) node: initiates heart impulses, pacemaker, located at superior end of the crista terminalis at the point of SVC opening to the right atrium. Generates impulses for 60-100 beats per minute.
- Sympathetic stimulation speeds up the heart.
- Parasympathetic stimulation slows down the heart (vagal stimulation)
- Arterial supply from the right coronary artery.
Cardiac Conduction System (Additional Information)
- AV (atrioventricular) node: receives impulses from the SA node, located in the right atrium within the interatrial septum over the right fibrous trigone.
- Generates impulses for the heart of about 50 beats per minute.
- Supplied by the right coronary artery.
- Bundle of His: origination in the AV node, conducting impulses to the right and left ventricles, supplied by the left anterior descending (LAD) artery.
- In right ventricle: septomarginal trabecula contains right bundle branch.
- Purkinje fibers spread from the bundle branches and reach the papillary muscles and ventricular myocardium.
Cardiac Conduction System Innervation
- Cardiac plexus is created by sympathetic and parasympathetic fibers.
- Sympathetic stimulation increases heart rate and fibers follow the spinal cord segments T1–T5,
- Parasympathetic stimulation slows the heart rate -Sensory nerves taking part in reflex arches of heart travel with the vagus nerve.
Mediastinum
- Central space between the pleural cavities.
- Superior mediastinum: Space between the manubrium of the sternum and the bodies of the superior thoracic vertebrae (T1-T4). Contains:
- Thymus (visible in children, then becomes atrophic and replaced by fat)
- Brachiocephalic veins and tributaries (subclavian veins and jugular veins, venous angles – beginning of superior vena cava).
- Inferior mediastinum
- Anterior mediastinum: Located between the sternum and the anterior surface of the pericardium. Contains areolar tissue, anterior mediastinal lymph nodes (parasternal), and internal thoracic artery and vein.
- Posterior mediastinum: Located between the posterior surface of the pericardium and vertebrae T5-T12. Contains the descending thoracic aorta, esophageal, posterior intercostal and bronchial branches. Aortic hiatus which passes into abdominal aorta.
Mediastinum (additional information)
- Superior mediastinum contains the vagus and phrenic nerves.
- Vagus nerve gives off recurrent laryngeal nerve that passes in the groove between the esophagus and trachea to reach the larynx.
- Right recurrent laryngeal nerve passes under the right subclavian artery, and the left recurrent laryngeal nerve passes under the aortic arch.
Mediastinum (Additional Information)
- The phrenic nerves arise from the C3-C5 ventral rami of the spinal nerves and supply the diaphragm with motor and sensory fibers.
Mediastinum (Additional Information)
- Branches of the arch of aorta: Brachiocephalic trunk (dividing into right common carotid artery and right subclavian artery), left common carotid artery, and left subclavian artery.
- Trachea: located posterior to the aortic arch, beginning at the level of C6 and bifurcating at T4, forming the carina (internal cartilage projection at bifurcation). The esophagus is posterior to the trachea and then to the left bronchus.
Mediastinum (Additional Information) - Anterior Mediastinum
- Anterior mediastinum: located between the sternum and the anterior surface of the pericardium, contains areolar tissue, anterior mediastinal lymph nodes, and the internal thoracic artery and vein.
Mediastinum (Additional Information) - Posterior Mediastinum
- Posterior mediastinum is located between the pericardium and the T12 vertebrae and contains the descending thoracic aorta, bronchial branches, esophagus, Posterior intercostal, and esophageal branches, and passes through the aortic hiatus at the T12 vertebral level becoming the abdominal aorta.
Mediastinum (Additional Information) - Posterior Mediastinum (aorta)
- Descending aorta is located in the posterior mediastinum; is the continuation of the arch of aorta and ascending aorta leaving the left ventricle
- Branches: bronchial, esophageal, and posterior intercostal branches. Passes through the aortic hiatus at the T12 vertebral level, continuing as abdominal aorta.
Mediastinum (Additional Information) - Posterior Mediastinum (veins)
- Azygos system of veins drains the posterior thoracic wall. Starting in the abdomen (connection with ascending lumbar vein and a small branch of the left renal vein).
- Ascends on the right side of the vertebral column, enters the mediastinum through the medial right diaphragmatic crus fissure.
- Right intercostal veins.
- Right subcostal vein
- Esophageal veins
- Posterior pericardial veins
- Superior right intercostal vein.
- Reaches the superior vena cava at the T5 level, terminating by arching over the root of the right lung.
- Hemiazygos vein is located on the left, starting in the abdomen, connecting to ascending lumbar vein and a branch of left renal vein.
- Ascends on the left side of the vertebral column and enters the mediastinum by the medial left diaphragmatic crus fissure.
Mediastinum (Additional Information) – drainage
- Left intercostal veins
- Left subcostal vein
- Esophageal veins
- Posterior pericardial veins
- Drains to the Azygos vein at the T7 level
- Created by the superior left intercostal vein
- Drainage: superior left intercostal vein over T6
Thorax CT
- Imaging modality for visualizing structures.
- Enables visualization of superior vena cava, right atrium, left atrium, left ventricle, right ventricle, pulmonary trunk, arch of aorta, descending aorta, trachea, esophagus, interventricular septum etc. and the various important structures in the thorax.
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Test your knowledge on the anatomy and physiology of the diaphragm with this quiz. Covering topics such as innervation, blood supply, and lymphatic drainage, this quiz is essential for students of human anatomy. Prepare to explore how the diaphragm interacts with other thoracic structures and its role in respiration.
