VASCULAR LESSON 1 MID Comprehensive Vascular Anatomy and Sonography Study Guide

Ascending Aorta and the Aortic Arch

• Pathway of the Ascending Aorta:     * The ascending aorta begins at the level of the aortic valve.     * It continues upward and backward, crossing the trachea.     * It passes posteriorly on the left side of the trachea, curves downward, and eventually becomes the descending aorta.

• Branches of the Aortic Arch:     * Brachiocephalic Artery: Also known as the innominate artery. It is the first branch and eventually divides into the right common carotid and the right subclavian arteries.     * Left Common Carotid Artery: The second branch arising directly from the aortic arch.     * Left Subclavian Artery: The third branch arising directly from the aortic arch.     * Mnemonics for Branches:         * ABCS: Ascending aorta, Brachiocephalic, common Carotid (left), Subclavian (left).         * BCS: Brachiocephalic, common carotid, subclavian (like the Bowl Championship Series in college football).

• The Right Pulmonary Artery (RPA):     * This is a critical landmark often featured on the echo registry exams.     * In short-axis ultrasound views, the RPA is located posterior to the ascending aorta.

Upper Extremity Arteries

• Subclavian Artery:     * Gives rise to branches supplying the brain, neck, thoracic wall, and shoulder.     * The vertebral artery originates directly from the subclavian artery.     * It continues until the outer border of the first rib, where it changes names to become the axillary artery.

• Axillary Artery:     * Begins at the outer border of the first rib.     * Continues through the axilla (armpit area).

• Brachial Artery:     * Begins at the axilla and continues through the upper arm.     * It extends to approximately $1\,cm$ below the elbow joint.     * Its largest branch is the profunda brachiae (deep brachial artery).     * Termination: The brachial artery "terminates" at its bifurcation into the radial and ulnar arteries.

• Ulnar Artery:     * Courses along the ulnar side (pinky side) of the forearm.     * It predominantly forms the superficial palmar arch in the hand.     * Mnemonic: "UltraSound" (US) — Ulnar supplies the Superficial arch.

• Radial Artery:     * Courses along the radial side (thumb side) of the forearm.     * Thumbs Up Metaphor: Thumbs up is "rad" (radial). The radius and thumb go together.     * It predominantly forms the deep palmar arch.     * Mnemonic: "Registered Diagnostic" or "Registered Doctor" (RD) — Radial supplies the Deep arch.

Upper Extremity Venous System

• Venous Characteristics:     * Veins are highly variable compared to arteries. While everyone's kidney is in the same spot, arm veins differ significantly between individuals.     * Confluence: Unlike arteries that branch/bifurcate, veins unite or form confluences as they travel back toward the heart.     * Vena Comitantes: This Latin term refers to the "corresponding veins" that run in pairs alongside an artery (e.g., two ulnar veins for one ulnar artery).

• Superficial Veins:     * Cephalic Vein: Located on the lateral aspect of the arm. It is often visible on the biceps of bodybuilders. It runs solo (not paired with an artery).     * Basilic Vein: Located on the medial (ulnar) aspect of the arm. It travels along the medial border of the biceps and joins the brachial vein to form the axillary vein.     * Median Cubital Vein: Connects the cephalic and basilic veins at the antecubital fossa (the crease of the elbow). This is the primary site for blood draws, IVs, and catheter placements. It is a common site for clot formation due to needle trauma.

• Deep Veins:     * Radial and Ulnar Veins: Deep, paired veins that follow the path of their respective arteries. They unite at the antecubital fossa to form the brachial veins.     * Brachial Veins: Paired veins running with the brachial artery.     * Axillary Vein: Begins at the junction of the brachial and basilic veins. Usually a single vein.     * Subclavian Vein: A continuation of the axillary vein starting past the outer border of the first rib.     * Brachiocephalic Veins: Formed by the junction of the Internal Jugular Vein (IJV) and the subclavian vein. Unlike arteries (where there is only a right brachiocephalic), there are both right and left brachiocephalic veins.     * Superior Vena Cava (SVC): Formed by the union of the right and left brachiocephalic veins. It courses behind the right side of the sternum.

Vasculature of the Thorax and Abdomen

• Thoracic Aorta:     * The descending aorta becomes the thoracic aorta beyond the arch.     * Branches include: bronchial arteries (lungs), esophageal arteries, phrenic arteries (diaphragm), intercostal arteries (ribs), and subcostal arteries.

• Abdominal Aorta:     * Begins at the level of the $12^{\text{th}}$ thoracic vertebra ($T12$).     * Enters the abdomen through the diaphragmatic hiatus (a hole in the diaphragm).     * Terminates at the level of the $4^{\text{th}}$ lumbar vertebra ($L4$) by bifurcating into the common iliac arteries.

• Major Branches of the Abdominal Aorta:     * Celiac Trunk (Celiac Artery): First major anterior branch. It divides into the left gastric, splenic, and common hepatic arteries to supply the stomach, spleen, and liver.     * Superior Mesenteric Artery (SMA): Second anterior branch, arising just below the celiac trunk. It supplies the Small intestine (SMA = Small).     * Renal Arteries: Lateral branches arising below the SMA.         * Right Renal Artery (RRA): Longer than the left because the aorta sits on the left of the midline. It courses posterior to the IVC.         * Left Renal Artery (LRA): Shorter course directly to the left kidney.     * Gonadal Arteries (Testicular/Ovarian): Anterolateral branches arising below the renal arteries.     * Inferior Mesenteric Artery (IMA): Last anterior branch, arising $3\,cm$ to $4\,cm$ above the aortic bifurcation. Supplies the large intestine.     * Lumbar Arteries: Four pairs of vessels arising posteriorly to supply the lumbar vertebrae.     * Middle Sacral Artery: A single posterior branch arising just above the bifurcation to supply the sacrum.

Arteries of the Pelvis and Lower Extremities

• Common Iliac Arteries: The bifurcation of the aorta at $L4$. Splits into:     * Internal Iliac Artery (Hypogastric Artery): Supplies the pelvic organs.     * External Iliac Artery: Supplies the lower extremities.

• Femoral System:     * Common Femoral Artery (CFA): Continuation of the external iliac artery after it passes under the inguinal ligament.     * Bifurcation of CFA: Splits into the Superficial Femoral Artery (SFA) and the Profunda Femoris (Deep Femoral Artery).     * Profunda Femoris: Courses posterior and lateral to the SFA; supplies the thigh muscles.     * SFA Passage: Travels distally through the Adductor Canal (also known as Hunter's Canal), protected by a dense fibrous tissue called an aponeurosis.

• Popliteal and Lower Leg Arteries:     * Popliteal Artery: Continuation of the SFA behind the knee in the popliteal fossa. Branches into genicular and sural arteries.     * Anterior Tibial Artery (ATA): First branch of the popliteal. Passes through the interosseous membrane to the shin. Becomes the Dorsalis Pedis at the ankle.     * Tibioperoneal Trunk: The short segment after the ATA takeoff that bifurcates into the Posterior Tibial and Peroneal arteries.     * Posterior Tibial Artery (PTA): Courses medially behind the medial malleolus (the inner ankle bone). Terminates into plantar arteries.     * Peroneal Artery (Fibular Artery): Courses deep along the medial aspect of the fibula (lateral side of the leg).

Veins of the Pelvis and Lower Extremities

• Deep Veins:     * Follow the arterial path (Common Femoral, SFA, Popliteal, PTA, Peroneal, ATA).     * Common Femoral Vein (CFV): Formed by the union of the femoral vein and the profunda femoris vein.

• Superficial Veins:     * Greater Saphenous Vein (GSV): The longest vein in the human body. Drains the superficial leg and enters the CFV.

• Iliac Veins and IVC:     * Internal and External Iliac veins unite to form the Common Iliac Veins.     * May-Thurner Physiology: The left common iliac vein passes beneath the right common iliac artery. The pressure from the artery can compress the vein against the spine, causing swelling or clots in the left leg.     * Inferior Vena Cava (IVC): Formed by the union of the right and left common iliac veins. It courses through the abdomen to the right of the aorta.

Hepatic and Portal Systems

• Liver Blood Supply:     * Hepatic Artery: Carries oxygenated blood ($30\%$ of total liver flow).     * Portal Vein: Carries nutrient-rich blood ($70\%$ of total liver flow). Formed by the Portosplenic Confluence (junction of the Splenic Vein and the Superior Mesenteric Vein).

• Flow Direction Terms:     * Hepatopetal: Blood flow toward the liver (Normal for Portal Vein).     * Hepatofugal: Blood flow away from the liver (Normal for Hepatic Veins).

• Hepatic Veins:     * Comprising Right, Middle, and Left hepatic veins.     * They drain the liver into the IVC.     * The Middle and Left hepatic veins typically form a common trunk before entering the IVC, creating a "bunny ear" appearance on ultrasound.

• Gonadal Vein Asymmetry:     * Right Gonadal Vein: Drains directly into the IVC.     * Left Gonadal Vein: Drains into the Left Renal Vein, which then enters the IVC. Because it drains into a smaller vessel at a right angle, clinical issues like varicoceles occur more frequently on the left side.