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Femoral Artery - Short Answer Question (SAQ)

Origin

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Course

1. In the Femoral Triangle

• Enters the femoral triangle by passing deep to the inguinal ligament
• Lies within the femoral sheath (lateral compartment), with the femoral vein immediately medial and the femoral nerve lateral (but outside the sheath)
• Reliably bisects the inguinal ligament at its midpoint - useful landmark when no palpable pulse exists
• Pulse is palpable here just inferior to the inguinal ligament

2. In the Adductor Canal (Hunter's Canal)

• Leaves the femoral triangle and enters the adductor canal
• The femoral vein shifts from medial to posterior to the artery as it travels distally
• Accompanied by the saphenous nerve, which crosses the artery within the canal
• The canal is bounded by: vastus medialis (laterally), adductor longus and adductor magnus (medially/posteriorly), sartorius (anteriorly as its roof)

3. Exits via Adductor Hiatus

• Passes through the adductor hiatus in the adductor magnus muscle
• Becomes the popliteal artery in the popliteal fossa behind the knee

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Relations in the Femoral Triangle

• N - Femoral Nerve (outside sheath, most lateral)
• A - Femoral Artery (lateral compartment of sheath)
• V - Femoral Vein (medial compartment of sheath)
• Y - Lymphatics/femoral canal (most medial compartment of sheath)

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Femoral Triangle (Boundaries)

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Femoral Sheath

• Transversalis fascia (anteriorly)
• Iliac fascia (posteriorly)

1. Lateral - Femoral artery
2. Middle - Femoral vein
3. Medial - Femoral canal (contains lymphatics; the femoral ring is its upper opening - site of femoral hernias)

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Branches

Small branches in the femoral triangle:

1. Superficial epigastric artery - runs to the anterior abdominal wall
2. Superficial circumflex iliac artery - runs laterally toward ASIS
3. Superficial external pudendal artery - supplies scrotum/labia majora
4. Deep external pudendal artery - supplies perineum

Major branch:

1. Profunda femoris artery (Deep artery of thigh) - arises from the posterolateral aspect of the femoral artery, approximately 4-5 cm below the inguinal ligament; this is the main blood supply to the thigh muscles

Branches of profunda femoris:

• Medial circumflex femoral artery - provides the principal blood supply to the head and neck of the femur (passes between pectineus/iliopsoas, then obturator externus/adductor brevis)
• Lateral circumflex femoral artery - gives ascending, descending, and transverse branches; participates in the cruciate anastomosis around the hip
• Three perforating arteries - penetrate adductor magnus to supply the posterior compartment of the thigh and form longitudinal anastomotic chains

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Cruciate Anastomosis

• Medial circumflex femoral artery
• Lateral circumflex femoral artery (transverse branch)
• Inferior gluteal artery
• First perforating artery of profunda femoris

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Termination

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Clinical Relevance

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THORAX - Complete MBBS Anatomy Notes

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PART 1: THORACIC WALL & SKELETON

Thoracic Cage Components

• Sternum (anteriorly): Manubrium + Body + Xiphoid process
• 12 pairs of ribs (laterally and posteriorly)
• 12 thoracic vertebrae (posteriorly)

Sternum Landmarks

The Sternal Angle (Angle of Louis) - HIGH YIELD

• Junction of manubrium and body of sternum
• Level of 2nd costal cartilage (rib counting starts here)
• Bifurcation of trachea (carina)
• Arch of aorta begins and ends here
• Divides mediastinum into superior and inferior

Classification of Ribs

Intercostal Space - Contents (VAN)

• V - Vein (most superior)
• A - Artery
• N - Nerve (most inferior - most exposed)

Clinical point: When inserting a chest drain/needle, always go over the upper border of the rib below to avoid the neurovascular bundle sheltered under the upper rib.

Thoracic Apertures

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PART 2: PLEURAL CAVITIES & PLEURA

Pleura Types

• Parietal pleura - lines the walls of the thoracic cavity (has 4 named parts):
  • Costal pleura (lines ribs)
  • Diaphragmatic pleura
  • Mediastinal pleura
  • Cervical pleura (cupola) - extends 2-3 cm above rib I into neck
• Visceral pleura - adheres to lung surface
• Both are continuous at the lung root

Pleural Recesses

• Costodiaphragmatic recess (most important) - between chest wall and diaphragm; site where fluid collects first
• Costomediastinal recess - between costal and mediastinal pleura, anterior

Nerve Supply of Pleura

• Parietal pleura - somatic innervation (intercostal nerves and phrenic nerves) = can feel PAIN
• Visceral pleura - autonomic = INSENSITIVE to pain (visceral afferents only)

Clinical: Pleural Effusion

Clinical: Pneumothorax

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PART 3: MEDIASTINUM

Division of Mediastinum

Superior Mediastinum - Contents

• Thymus gland (or its remnant/fat)
• Brachiocephalic veins (left and right) → form Superior Vena Cava
• Arch of aorta and its 3 branches:
  1. Brachiocephalic trunk (→ right subclavian + right common carotid)
  2. Left common carotid artery
  3. Left subclavian artery
• Trachea (bifurcates at carina at sternal angle level)
• Oesophagus (posterior to trachea)
• Thoracic duct (upper part)
• Phrenic nerves (bilateral)
• Vagus nerves (bilateral)
• Left recurrent laryngeal nerve (hooks under arch of aorta at ligamentum arteriosum)
• Sympathetic trunks (bilateral)
• Lymph nodes

Key clinical: Left recurrent laryngeal nerve passes through the aortopulmonary window. Lung cancer / enlarged lymph nodes here compress it → hoarseness of voice.

Anterior Mediastinum - Contents

• Inferior extension of thymus
• Fat and connective tissue
• Mediastinal branches of internal thoracic vessels
• Sternopericardial ligaments
• Lymph nodes

Masses here: Thymic tumours, Teratoma, Thymoma, Lymphoma ("4 T's of anterior mediastinum")

Middle Mediastinum - Contents

• Pericardium
• Heart (the main occupant)
• Ascending aorta and pulmonary trunk (proximal)
• Superior and inferior vena cava (proximal)
• Pulmonary veins (proximal)
• Phrenic nerves (along pericardium)
• Pericardiacophrenic vessels

Posterior Mediastinum - Contents

• Oesophagus (with oesophageal plexus of vagus)
• Descending thoracic aorta
• Azygos vein (right side) and hemiazygos / accessory hemiazygos veins (left side)
• Thoracic duct
• Thoracic sympathetic trunks
• Splanchnic nerves
• Posterior intercostal vessels
• Lymph nodes

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PART 4: LUNGS

General Features

• Right lung: 3 lobes (upper, middle, lower), 2 fissures (oblique + horizontal), 10 bronchopulmonary segments, shorter and wider
• Left lung: 2 lobes (upper, lower), 1 fissure (oblique), 9-10 bronchopulmonary segments; has lingula (homologue of right middle lobe), cardiac notch on anterior border

Lung Root (Hilum) Contents - Order

Bronchi

• Trachea bifurcates at carina (T4-T5 level, sternal angle)
• Right main bronchus: Shorter, wider, more vertical (foreign bodies enter right side more often)
• Left main bronchus: Longer, narrower, more horizontal

Bronchopulmonary Segments

• A distinct structural and functional unit
• Supplied by its own segmental (tertiary) bronchus
• Has its own segmental artery (branch of pulmonary artery)
• Can be surgically resected independently

Blood Supply of Lungs

• Pulmonary arteries (deoxygenated blood for gas exchange)
• Bronchial arteries (oxygenated blood for lung tissue nutrition) - from thoracic aorta (left) and right intercostal/subclavian (right)

Nerve Supply

• Pulmonary plexus (anterior and posterior) - sympathetic + parasympathetic (vagus)
• Sympathetic = bronchodilation + vasoconstriction
• Parasympathetic = bronchoconstriction + secretion

Surface Markings of Lungs and Pleura

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PART 5: PERICARDIUM & HEART

Pericardium

1. Fibrous pericardium (outer) - tough; apex is continuous with adventitia of great vessels; base is attached to central tendon of diaphragm; attached to sternum by sternopericardial ligaments
2. Serous pericardium (inner) - two layers:
   • Parietal serous pericardium (lines fibrous pericardium)
   • Visceral serous pericardium = Epicardium (covers the heart)

Pericardial Sinuses

• Transverse pericardial sinus - between arteries (aorta + pulmonary trunk) anteriorly and veins (SVC + pulmonary veins) posteriorly. A finger placed here during surgery separates arteries from veins.
• Oblique pericardial sinus - J-shaped recess posterior to left atrium (between pulmonary veins)

Nerve Supply of Pericardium

• Phrenic nerves (C3, C4, C5) carry somatic sensation (pain) from parietal pericardium
• Pain referred to shoulder and lateral neck (C3-C5 dermatomes)
• Also receives vagus nerve and sympathetic trunk fibers (visceral)

Clinical: Pericarditis

• Inflammation of pericardium - diffuse ST elevation on ECG
• Pain relieved by sitting forward (unlike MI)
• Causes: viral, bacterial, post-MI, uraemia, autoimmune

Clinical: Cardiac Tamponade

• Fluid in pericardial sac compresses heart
• Beck's triad: hypotension + raised JVP + muffled heart sounds
• Treatment: pericardiocentesis (needle inserted below xiphoid process at a 45° angle toward left shoulder)

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PART 6: THE HEART

Position and Orientation

• Located in the middle mediastinum
• Base faces posteriorly (at T5-T8 level)
• Apex points inferolaterally to the left
• Apex beat: Left 5th intercostal space, 8-9 cm from midsternal line (mid-clavicular line)

Surfaces of the Heart

Chambers - Key Points

• Receives: Superior vena cava (above) + Inferior vena cava (below) + Coronary sinus
• Internal features: Crista terminalis (divides into sinus venarum and atrium proper), Musculi pectinati, Fossa ovalis (remnant of foramen ovale)
• The crista terminalis marks the SA node location superiorly

• Forms most of anterior surface
• Inflow (rough, trabeculated) + Conus arteriosus/Infundibulum (smooth outflow to pulmonary trunk)
• Valve: Tricuspid valve (3 cusps: anterior, posterior, septal)
• Contains: trabeculae carneae, papillary muscles (3: anterior, posterior, septal), moderator band (septomarginal trabecula) carrying right bundle branch

• Receives 4 pulmonary veins (2 from each lung)
• Predominantly smooth walled; small auricle has pectinate muscles
• Most posterior chamber - esophagus lies directly behind

• Thick-walled (wall thickness ~3x right ventricle)
• Inflow (rough) + Aortic vestibule (smooth outflow)
• Valve: Mitral (bicuspid) valve (2 cusps: anterior and posterior); guarded by 2 papillary muscles

Cardiac Valves - Surface Markings & Auscultation Sites

Coronary Arteries

• Travels in right atrioventricular groove
• Branches: SA nodal artery (60%), right marginal artery, AV nodal artery (most cases)
• Terminates as posterior interventricular artery (PDA) in right-dominant hearts (70%)
• Supplies: Right atrium, right ventricle, SA node, AV node (usually), posterior LV

• Short left main stem → divides into:
  1. Anterior interventricular artery (LAD) - descends in anterior interventricular groove; supplies most of interventricular septum, anterior LV, anterior RV
  2. Circumflex artery (LCx) - travels in left AV groove; supplies left atrium, lateral/posterior LV; gives left marginal artery

• Right dominant: 70%
• Left dominant: 10%
• Co-dominant: 20%

Cardiac Veins

• Great cardiac vein - runs with LAD, drains into coronary sinus
• Middle cardiac vein - runs with PDA
• Small cardiac vein - runs with right marginal artery
• All drain into Coronary sinus → empties into right atrium
• Some small anterior cardiac veins drain directly into right atrium

Cardiac Conduction System

• "Pacemaker of the heart" - intrinsic rate 60-100 bpm
• Located at the superior end of crista terminalis (junction of SVC and right atrium)
• Blood supply: Right coronary artery (60%), LCx (40%)

• Located in the interatrial septum near the opening of the coronary sinus (Triangle of Koch)
• Intrinsic rate 40-60 bpm
• Blood supply: Right coronary artery (usually)

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PART 7: GREAT VESSELS

Arch of Aorta

• Begins and ends at sternal angle (T4-T5 level)
• Arches over the left main bronchus
• 3 branches (right to left):
  1. Brachiocephalic trunk (→ right subclavian + right common carotid arteries)
  2. Left common carotid artery
  3. Left subclavian artery
• Ligamentum arteriosum (remnant of ductus arteriosus) connects arch to left pulmonary artery

Clinical: Coarctation of Aorta

• Narrowing usually just distal to origin of left subclavian artery (juxtaductal)
• Collateral circulation via intercostal arteries → rib notching on X-ray (lower borders of 3rd-9th ribs)
• Higher BP in arms vs legs; radio-femoral delay

Pulmonary Trunk

• Arises from right ventricle, passes upward and left
• Divides at T5-T6 (under arch of aorta) into right and left pulmonary arteries
• Right PA: passes posterior to ascending aorta and SVC → right lung
• Left PA: passes anteriorly to descending aorta → left lung

Superior Vena Cava (SVC)

• Formed by union of left + right brachiocephalic veins
• Drains: Upper half of body
• SVC syndrome: Obstruction causes facial and upper limb edema, dilated chest wall veins

Azygos Vein System

• Azygos vein (right side): drains posterior thoracic wall, enters SVC at T4 level
• Hemiazygos vein (left side, lower): crosses midline at T9 to join azygos
• Accessory hemiazygos (left side, upper): crosses midline at T8 to join azygos
• The azygos system is a major collateral pathway when IVC or SVC is obstructed

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PART 8: DIAPHRAGM

Structure

• Musculotendinous dome separating thorax from abdomen
• Peripheral muscle + Central tendon
• Two domes: Right dome higher (T8-T9) due to liver; Left dome lower (T9-T10)

Attachments (origins of muscular parts)

• Sternal part: posterior surface of xiphoid process
• Costal part: inner surfaces of lower 6 ribs and costal cartilages
• Vertebral part: by crura (right crus from L1-L3, left crus from L1-L2) and arcuate ligaments

Openings and Levels - HIGH YIELD EXAM TOPIC

Nerve Supply

• Motor: Phrenic nerve only (C3, C4, C5 - "C3, 4, 5 keeps the diaphragm alive")
• Sensory:
  • Central (tendinous) portion - phrenic nerve (referred pain to shoulder, C3-C5)
  • Peripheral portion - lower 6 intercostal nerves

Blood Supply

• Superior surface: Pericardiacophrenic, musculophrenic, superior phrenic arteries
• Inferior surface: Inferior phrenic arteries (from abdominal aorta or coeliac)

Diaphragmatic Hernias

• Hiatus hernia - stomach herniation through esophageal hiatus (most common)
  • Sliding (type I) - 90%: gastroesophageal junction moves up
  • Rolling/Para-oesophageal (type II): gastric fundus herniates alongside normal GEJ
• Bochdalek hernia (congenital, posterolateral) - left side more common
• Morgagni hernia (congenital, anterior) - right side more common

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PART 9: KEY NERVES IN THORAX

Phrenic Nerve (C3, C4, C5)

• Right phrenic: Down right of SVC → along right side of pericardium → exits through caval foramen (T8) with IVC
• Left phrenic: Crosses over aortic arch superficial to left vagus → along left side of pericardium → pierces diaphragm near apex

Vagus Nerve (CN X) in Thorax

• Right vagus: Crosses anterior to right subclavian artery → gives right recurrent laryngeal nerve (hooks under right subclavian) → passes posteriorly → joins oesophageal plexus → exits as posterior vagal trunk through oesophageal hiatus (T10)
• Left vagus: Crosses aortic arch → gives left recurrent laryngeal nerve (hooks under arch of aorta at ligamentum arteriosum) → passes posteriorly → joins oesophageal plexus → exits as anterior vagal trunk

Clinical: Left RLN: hoarseness in lung cancer, aortic aneurysm. Right RLN: hoarseness in right apex lung cancer.

Thoracic Duct

• Largest lymphatic vessel
• Enters thorax through aortic hiatus (T12)
• Ascends in posterior mediastinum between oesophagus and azygos vein
• Crosses midline at T5, ascends in superior mediastinum
• Drains into left venous angle (junction of left internal jugular + left subclavian veins)
• Drains ALL lymph EXCEPT: right side of head/neck/thorax + right upper limb (drained by right lymphatic duct)

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PART 10: CLINICAL ANATOMY SUMMARY TABLE

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