Anatomy of Circulation

Arterial System of Brain

• branchiocephalic

  • diverge into subclavian artery and common carotid artery which supply right upper limb and heart/neck respectively

• carotid arteries

  • diverge into internal and external carotid arteries and will supply inside of the skull/brain/anterior circulation and outside of skull, face and scalp respectively

• vertebrobasal arteries

  • the subclavian artery branches out to the vertebrate arteries which go through the foramen transversaria

  • the left and right vertebrate arteries meet at the foramen magnum to form the basilar artery

  • will provide blood to brainstem, cerebellum and occiptial lobes (posterior circulation)

What is the Circle of Willis?

Its a cerebrial arteries circle which interconnects the internal carotid arteries and basilar artery via anastomoses (fusion)

Venous system of brain (Sinuses)

• The superficial cerebral veins of the brain will drain out into the sinuses

• We have inferior and superior sinuses, transverse sinuses and straight sinuses. → they will empty out into the veins (internal jugular vein)

Venous system of brain (Veins)

• Right and Left Internal Jugular Veins (receive blood from deeper structures of the brain)

• Right and Left External Jugular Veins (receive blood from superficial structures of the brain)

• Left/Right Subclavian Vein (receives blood from the left/right limbs)

• Branchiocephalic Vein → branches out of internal jugular vein + subclavian vein

  • Will flow into the Inferior Vena Cava

What are the different Hemorrhages?

• Epidural Hemorrhages → between skull and dura (damage of middle meningal artery) - cause is trauma

• Subdural Hemorrhages → between dura and arachnoid layers (damage of bridging arteries) - can be trauma or atrophy

• Subarachnoid Hemorrhages → aneurysm rupture in the subarachnoid space

• Intercerebral Hemorrhages → brain tissue

Arterial System of Arm

• Subclavian artery → Auxillary → Branchial → Radial (outside) & Ulnar (inside) → Into digital arteries of the hand.

Venous System of Arm

• There are two systems:

  • Superficial: Cephalic + Basal + Medical Cubital

  • Deep: Radial + Ulnar → Branchial → Auxillary

• Both systems will flow into Subclavian → Bronchiocpehalic → SVC → Right Atrium

Arterial System of Thorax

• Subclavian artery branches into the Internal thoracic artery

• Surrounding the ribs we have the intercostal anterior/posterior arteries which supply blood these.

• Bronchial arteries supply blood to bronchi in lungs

• Esophogal Arteries in the Esophogous

Venous System of Thorax - Azygous System

• Right intercostal veins drain into → Azygous Vein

• Left intercostal veins drain into → Hemi-azygous and acessory hemi-zygous veins → both drain back into the Azygous Vein → Superior Vena Cava

Arterial System of Abdomen

• Paired System: Right/Left Renal Arteries, Right/Left Gonadal Arteries, Right/Left Lumbar Arteries

• Unpaired:

  • Celiac Trunk: stomach, esophogous, spleen, liver, pancreas, duodenum

  • Superior mesenteric artery: Small intestine, jejunum, ileum

  • Inferior mesenteric artery: Large intestine, cecum, appendix, colon and rectum.

Venous System of Abdomen

• Goes through the portal vein

• Superior mesenteric vein + splenic vein + Inferiour mesenteric vein → portal vein → liver → hepatic vein → IVC

Process of anastomoses of portocaval system

Cirrhosis -> scarred liver -> portal blood cannot flow through easily -> portal hypertension -> blood rerouted through portocaval anastomoses -> enlarged veins and risk of bleeding.

Arterial System of Lower Extremities

Common illiac artery → external illiac artery → femoral → popliteal → splits into anterior and posterior tibial → fibular

Venal System of Lower Extremities

Small saphenous → Great saphenous → Popliteal → Femoral → External Illiac Artery → Common illiac artery → IVC.

What is significant about the small and great saphenous veins?

• They are prone to varicouse veins because they are long superficial and rely on valves to fight gravity.