Heart Anatomy PDF

Introduction Thorax, Heart, and Vessels of Heart Heart Anatomy Layers of the Heart - Oblique and transverse sinuses. - The heart is made of 4 chambers: left atrium, left ventricle, right atrium, right ventricle. - Atria have protrusions called auricles which increase the capacity when nee...

Introduction Thorax, Heart, and Vessels of Heart Heart Anatomy Layers of the Heart - Oblique and transverse sinuses. - The heart is made of 4 chambers: left atrium, left ventricle, right atrium, right ventricle. - Atria have protrusions called auricles which increase the capacity when needed. - The heart has 4 borders: 1. Superior border – right and left atria, superior vena cava, ascending aorta (aortic arch), pulmonary trunk. 2. Inferior border – right ventricle and part of the left ventricle. 3. Right border – right atrium (between the superior and inferior vena cava). 4. Left border – left ventricle and part of the left auricle. Anterior and Posterior View  - Superior and inferior vena cava open into the right atrium. - Ascending aorta emerges from the left ventricle and has 3 branches: Brachiocephalic trunk – right common carotid and subclavian Left common carotid Left subclavian - Pulmonary trunk emerges medially to the left auricle. - Right pulmonary artery goes under the aortic arch. - Left ventricle is the most anterior portion of the heart. - Right atrium is the most posterior portion of the heart. - Coronary sulcus divides the atria and the ventricles. - Interventricular sulci divide the right and left ventricles. Chambers Right Atrium  - Sulcus terminalis, a groove on the external surface of the right atrium, marks the junction of the primitive sinus venarum with the atrium proper in the embryo and corresponds to a ridge on the internal heart surface, the crista terminalis. - Tricuspid orifice is where the blood flows from the right atrium into the right ventricle. - Superior vena cava – 3rd costal cartilage // Inferior vena cava – 5th costal cartilage. - Coronary sinus opens between the inferior vena cava orifice and the tricuspid orifice. - Right and left atria are separated by the interatrial septum, which has a depression called oval fossa. Right Ventricle - Inflow – trabeculae carneae. - Outflow – conus arteriosus. - Tricuspid orifice is surrounded by a fibrous ring that is continuous with the heart that keeps its shape constant. - Tricuspid valve, attached to the tricuspid orifice, regulates the blood flow from the right atrium to the right ventricle. It has 3 cusps (anterior, posterior, septal) that open and close during systole and diastole. - Choridnae tendinae anchor the cusps to the papillary muscles. - Anterior papillary muscles are the largest and arise from the anterior wall of the right ventricle. Its choridnae tendinae are attached to the anterior and posterior cusps.  - Posterior papillary muscles arise from the posterior wall of the right ventricle. Its choridnae tendinae are attached to the posterior and septal cusps. - Septal papillary muscles arise from the interventricular septum. Its choridnae tendinae are attached to the anterior and septal cusps. [above mentioned → help block the backflow during systole (contraction)] - Interventricular septum (IVS) separates the two ventricles and is made of: Membranous part - Superiorly and posteriorly. - Thin and continuous with the fibrous skeleton of the heart. - Septal cusp is attached to the center. Muscular part - 2-3x thicker than the rest of the right ventricle. - VSD is a defect that is usually in the membranous part of the IVS as it is thin, but it can occur in the muscular part (can heal). - Moderator band (Septomarginal Trabecula) is an isolated band of trabeculae carneae that extends from the IVS to the anterior papillary muscles of the right ventricle, and helps the right ventricle contract properly by making the anterior papillary muscles contract at the same time as the other papillary muscles and it prevents overdistention of the ventricle and carries the right limb (Purkinje fibers) of the atrioventricular (AV) bundle from the septum to the sternocostal wall of the ventricle. Left Atrium - Left atrium is slightly thicker than the right atrium. - Pulmonary veins (left superior, right superior, left inferior, right inferior) enter the right atrium posteriorly and have no valves. - Mitral orifice is where the blood flows from the left atrium into the left ventricle. Left Ventricle  - Left ventricle forms the apex of the heart. - Since the pressure in the left ventricle is higher, the walls are 2-3x thicker than the right ventricle. - Left ventricle has more but finer trabeculae carneae than the right ventricle. - Aortic vestibule is a smooth non muscular wall, which leads into the aortic orifice and aortic valve. (3rd CC) - Mitral valve surrounds the mitral orifice, and is considered a bicuspid valve: anterior and posterior cusps. (4th CC) - Choridnae tendinae anchor the cusps to the papillary muscles. Vessels Pulmonary Trunk and Aorta - Blood travels from the right ventricle into the pulmonary trunk through the pulmonary semilunar valve.  - Blood travels from the left ventricle into the ascending aorta through the aortic semilunar valve. - The pulmonary semilunar valve has an anterior, right and left cusps. - The aortic semilunar valve has a posterior, right and left cusps. - The semilunar cusps are smaller and have no chordae tendineae to support them, compared to tricuspid cusps. - Edges of the cusps → lunule. - Meetpoint of the cusps → nodule. - Superior to each semilunar cusp is a sinus filled with blood to prevent the cusp from sticking to the wall. - The right coronary artery originates from the sinus above the right aortic cusp. - The left coronary artery originates from the sinus above the left aortic cusp. - During ventricular relaxation, the semilunar valves close and the blood is forced back into the heart where the cusps snap close (reverse umbrella) and the coronary arteries are filled with blood. - During ventricular contraction, the semilunar valves open. Nodal Tissue  - The SA node is located anterolaterally at the junction of the superior VC and right atrium, near the superior end of the sulcus terminalis. It is the pacemaker of the heart and establishes the basic heart rhythm. - The AV node is located at the posteroinferior region of the interatrial septum, near the opening of the coronary sinus. - The SA node initiates an impulse in the atria, making them contract. The impulse then spreads to the AV node then to the ventricles to the AV bundle (bundle of Hiss). At the junction of the membranous and muscular parts of the IVS, the AV bundle splits into right and left branches, the purkinje fibers, that further stimulates the IVS and their respective ventricles. Blood Flow - Deoxygenated blood: superior and inferior vena cava → right atrium → tricuspid valve → right ventricle → pulmonary semilunar valve → pulmonary arteries → lungs. (PULMONARY CIRCULATION) - Oxygenated blood: lungs → pulmonary veins → left atrium → mitral valve → left ventricle → aortic semilunar valve → aorta. (SYSTEMIC CIRCULATION) Cases - Aortic coarctation is narrowing of the aorta that causes an inclusion between two parts (3 sign). - Regurgitation occurs when valves aren’t able to fully close to prevent backflow to the heart. - Pericardial effusion occurs when excess fluid builds up in the pericardial sac around the heart. - Atrial fibrillation is an irregular and rapid heart rhythm. Blood accumulates in the auricle of the atria → thrombosis → enter the blood pathway → enter the ventricles → aorta → vessels → stroke. Risks: stasis (no movement) Coronary Arteries Right Coronary Artery - Origin: Right aortic sinus - Course: Runs between the pulmonary trunk and right auricle and descends vertically to the right anterior atrioventricular groove/coronary sulcus up to the junction of the right and inferior border of the heart. At the inferior border of the heart, it turns posteriorly and runs into the posterior atrioventricular groove up to the posterior interventricular groove. It terminates by anastomosing with the left coronary artery. - Branches 1) Right conus artery – supplies the anterior surface of pulmonary conus 2) Anterior ventricular branches – supplies the anterior surface of right ventricle Marginal branch is the largest and runs along the lower margin of the sternocostal surface to reach the apex. 3) Atrial branches Artery of sinoatrial node (60% of cases) 4) Posterior ventricular branches – supplies the diaphragmatic surface of the right and left ventricles 5) Posterior descending artery (posterior interventricular artery) – runs in the posterior interventricular groove up to the apex and supplies the posterior part of the IVS, AV node (60% of cases), and right and left ventricles. Left Coronary Artery - Origin: Left posterior aortic sinus of the ascending aorta above the aortic valve. - Course: Runs between the pulmonary trunk and left auricle and divides into the anterior descending artery (anterior interventricular artery) and descends vertically to the left anterior interventricular groove up to the apex of the heart, where it turns posteriorly to enter the posterior interventricular groove. It terminates by anastomosing with the posterior interventricular artery (branch of the right coronary artery). The circumflex artery winds around the left margin of the heart and continues into the left posterior coronary sulcus up to the posterior interventricular groove. It terminates by anastomosing with the right coronary artery. - Branches  1) Left anterior descending artery (anterior interventricular artery) – supplies the anterior part of the IVS, greater part of the right ventricle and part of the left ventricle, and part of the left AV bundle (bundle of Hiss). 2) Circumflex artery – gives a left marginal artery that supplies the left margin of the left ventricle up to the apex of the heart. 3) Diagonal artery 4) Conus artery – supplies the pulmonary conus. 5) Atrial branches – supply the left atrium. Clinical Correlation - Angina Pectoris: If the coronary arteries are narrowed, the blood supply to the cardiac muscle is reduced. As a result, on exertion, the patient feels severe pain in the region of the left precordium for ~20 minutes. The pain is often referred to the left shoulder and medial side of the arm and forearm. Pain occurs on exertion and is relieved by rest. - Myocardial Infarction: A sudden block of one the largest branches of the coronary artery usually leads to myocardial ischemia followed by myocardial necrosis. The part of the heart suffering from MI stops functioning and often causes death– heart attack or coronary attack. MI mostly occurs at rest. Clinical features 1. Sensation of pressure/sinking and pain in the chest that last more than 30 minutes. 2. Nausea or vomiting, sweating, shortness of breath and tachycardia. 3. Pain radiates to the medial side of the arm, forearm and hand. Sometimes it may be referred to the jaw or neck. 4. If PDA is damaged – low blood pressure; tachycardia. - AP – plaque not ruptured, vessels are not totally occluded. - MI – plaque ruptured, thrombocytes are clotted, vessels are totally occluded. - Common sites of coronary artery occlusion 1. Left anterior descending artery (anterior interventricular artery) – 40-50% 2. Right coronary artery – 30-40% 3. Circumflex branch of the left coronary artery – 15-20% Venous Drainage - The venous blood of the heart is drained into the right atrium by coronary sinus, anterior cardiac veins, venae cordis minimae (thebasian veins). Coronary Sinus - The principal and largest vein of the heart, lying in the posterior part of the atrioventricular groove. - It develops from the left horn of the sinus venosus and a part of the left common cardinal vein. - Most of the venous blood from the wall of the heart is drained into the right atrium through the coronary sinus. Tributaries 1. Great cardiac vein – accompanies the anterior descending and circumflex arteries to join the left end of the coronary sinus. 2. Middle cardiac vein – accompanies the posterior interventricular artery. 3. Small cardiac vein – accompanies the right marginal artery. 4. Posterior vein of the left ventricle – runs on the diaphragmatic surface of the left ventricle and joins the sinus to the middle cardiac vein. 5. Oblique veins of left atrium (vein of Marshall) – runs downwards on the posterior surface of left atrium to enter the left end of the coronary sinus. It develops from the left common cardinal vein (duct of Cuvier). 6. Right marginal vein – accompanies the marginal branch of the right coronary artery and joins small cardiac vein and drains directly into the right atrium. 7. Left marginal vein – accompanies the marginal branch of the left coronary artery. Anterior Cardiac Veins  - A series of small veins that run parallel to each other across the surface of the right ventricle to open into the right atrium. Venae Cordis Minimae - Extremely small veins in the walls of the chamber of the heart. The Aorta - The aorta begins at the left ventricle and terminates at the level of L4. - Four main sections of the aorta: ascending aorta, aortic arch, thoracic (descending) aorta and abdominal aorta. - Course: originates to the right of the pulmonary trunk from the left ventricle. The aortic arch bends in dorsal direction over the right pulmonary artery and runs in the upper part of thorax, left of the vertebral column and next to the esophagus, it then lies anterior of the vertebral column at the level of the diaphragmatic aperture, which lies more caudal and ventral than the esophagus and inferior vena cava openings. Upon passage through the diaphragm, the aorta is bordered by bundles of diaphragm muscle (crux diafragmatica) arching around it, it then lies in the abdomen directly ventral to the vertebral column, to the left of the inferior vena cava and splits (aortic bifurcation) at the level of L4. Ascending Aorta - Origin: Aortic orifice - Location: Middle mediastinum - Length: 2 in or 5 cm - Branches 1. Right coronary artery 2. Left coronary artery - It travels along with the pulmonary trunk within the pericardial sheath. Aortic arch - Origin: 2nd sternocostal joint - Termination: T4 - Location: Superior mediastinum  - Length: 5 cm - Branches 1. Brachiocephalic trunk Right common carotid artery and right subclavian artery – supply the right side of the head, neck and upper limb. 2. Left common carotid artery – supplies the left side of the head and neck. 3. Left subclavian artery – supplies the left upper limb. - It arches superiorly, posteriorly and inferiorly. - It is connected to the pulmonary trunk by the ligamentum arteriosum. Thoracic (descending) Aorta - Origin: T4 - Termination: T12 - Location: Posterior mediastinum - Length: - Branches 1. Bronchial arteries 2. Mediastinal arteries 3. Esophageal arteries 4. Pericardial arteries 5. Superior phrenic arteries – supply the superior diaphragm 6. Intercostal and subcostal arteries – 9 pairs - Initially begins to the left of the vertebral column but approaches the midline as it descends. - It exits the thorax via the aortic hiatus in the diaphragm where it becomes the abdominal aorta. Abdominal Aorta - Origin: T12 - Termination: L4 - Location: - Length: - Branches 1. Inferior phrenic arteries – supply the diaphragm. – unpaired anterior – 2. Celiac trunk (T12) – supplies the foregut. 3. Superior mesenteric artery (L1) – supplies the midgut.  4. Inferior mesenteric artery (L3) – supplies the hindgut. 5. Middle suprarenal artery 6. Renal arteries 7. Gonadal arteries 8. Median sacral artery 9. Lumbar arteries - It terminates by bifurcating into the right and left common iliac arteries that supply the lower limbs. Aortic Dissection - An aortic dissection is a serious condition which occurs when there is injury in the innermost wall; the tunica intima of the aorta. - This tear creates 2 channels for blood flow: A) Normal lumen of the aorta B) Into the wall where blood remains stationary. - The blood that remains in the wall can result in constriction of the aortic lumen leading to a reduction of blood flow to the rest of the body. - Site: occur anywhere along the aorta but the most common site is the beginning of the ascending aorta. - Clinical picture: tearing chest pain which radiates to the back, stroke or mesenteric ischemia. - Causes: chronic hypertension, a weakened aortic wall (due to Marfan syndrome, pathological processes, or an aortic aneurysm). - Investigations: CT angiogram, MRI angiograms, and transesophageal echocardio. - Treatment: Type A Type B Ascending aorta Descending aorta Surgically remove the dissected aorta Similarly surgery as type A with addition in order to stop blood from leaking of a stent  into the aortic wall and a graft is then used to reconstruct the aorta Medications are used to reduce heart Lifelong medications are used to control rate and lower blood pressure blood pressure Aortic Aneurysm - An aortic aneurysm is a balloon-like bulge or dilation of the aorta to more than 50% times its normal diameter. - Site: occur anywhere in your aorta but the most common site is the abdominal aorta– triple A (abdominal aortic aneurysm). - Clinical picture: back pain, abdominal pain, abdominal pulsations, pain and numbness in the lower limbs (due to compression of the nerve root). - Causes: underlying weakness of the vessel walls, Marfan syndrome, pathological processes, aortic dissection, males smokers above 60-65 need abdominal U/S - Investigations: U/S. - Treatment: surgical replacement of the weakened vessel wall with a piece of synthetic tubing. - Aortic aneurysms that are small usually do not present immediate threat however if left untreated a large aneurysm can rupture, this is a medical emergency and is often fatal. - Aortic arch aneurysm may cause a hoarse voice due to involvement of the left recurrent laryngeal nerve which wraps around the aortic arch. - Left and right atria are close to the laryngeal nerve causing dilation. Aortic Coarctation - Congenital condition - Pathological narrowing of the aorta (usually at the insertion of ligamentum arteriosum). - Narrowing of the vessel → increased resistance to blood flow → increased afterload for the left ventricle (pressure that the heart must work against to eject blood) → left ventricular hypertrophy. - As the coarctation is located distal to the vessels that supply the head, neck and upper limbs, blood supplying to those areas are not compromised. - On the other hand, blood supply to the lower limbs is reduced, resulting in weakness of the lower limbs and a weak delayed femoral pulse. - Treatment: depends on the age of diagnosis and the severity of the condition. - Common interventions are surgical, however balloon angioplasty and stenting may be used as first line. - Stenosis distal to the left subclavian artery results in hypertension (↑ BP) in the upper limbs and the head, and hypotension (↓ BP) in the lower limbs and abdomen. - If coarctation involves the origin of the left subclavian artery, BP in the right side of the head, neck and upper limbs will be higher than in the left arm, lower limbs, and abdomen. - There are 2 forms of aortic coarctation: infant form and adult form. Infant Form - The infant form accounts for about 70% of cases. - The coarctation comes after the aortic arch and before the ductus arteriosus– exists during fetal development and closes after birth but with infantile coarctation the ductus arteriosus is usually still open or patent; pre duck-billed coarctation.  - When the blood is pumped out of the pulmonary artery, it could go through the patent ductus arteriosus and continue down the aorta (higher pressure) OR to continue on down the pulmonary artery (lower pressure). - Due to the coarctation, the area right before the ductus arteriosus is narrower, so blood flowing from the left side has a harder time going through it and so there's a high pressure upstream of the coarctation but low pressure downstream. - So, the blood decides to through the patent ductus arteriosus and into the lower pressure area in the systemic circulation and then continue down to the lower extremities rather than the slightly higher pressure pulmonary artery. - Since deoxygenated blood is being delivered to the lower extremities, infants usually have lower extremity cyanosis. - Without intervention, infants often don't survive past the neonatal period. - Highly associated with Turner syndrome, a genetic abnormality where females only have 1 X chromosome instead of 2. Adult Form - The adult form accounts for about 30% of cases. - Typically developed as an adult and there usually isn't a patent ductus arteriosus and instead it has been long since it closed off and is now known as the ligamentum arteriosus. - There's no mixing of deoxygenated and oxygenated blood but similar to the infant form, there's a high pressure upstream of the coarctation but low pressure downstream, so blood flowing from the left side has a harder time going through it. - Upstream issues Blood flow increases into the aortic branches and therefore blood pressure increases in the head, neck and upper limbs. Increased cerebral blood flow means an increased risk of berry aneurysms. Increased pressure causes the aorta and aortic valve to dilate, increasing the risk of aortic dissection. - Downstream issues: Blood flow decreases downstream from the constriction and therefore blood pressure decreases in the lower extremities → weak pulse, claudication legs, pain and cramping. Reduced perfusion to the kidneys → activating angiotensin aldosterone system; water retention and increasing blood pressure therefore causing hypertension. - Coming off the aorta, there are intercostal arteries that run alongside the ribs and supply blood to the area between the ribs; the intercostal space. - Some of the intercostal arteries branch off above the constriction; anterior intercostal arteries and some branch off below the constriction; posterior intercostal arteries. - Upstream: increased pressure in the aorta → right subclavian artery → internal thoracic artery → anterior intercostal arteries and posterior intercostal arteries for ribs 1 and 2. - Downstream: decreased pressure in the aorta → posterior intercostal arteries for ribs 3 and below. - The anterior and posterior intercostal arteries normally link up to form an anastomosis (direct connection). - Under normal circumstances, the pressure is equal in the anterior and posterior arteries so blood flows away from the heart. - But due to the high-pressure system in the anterior arteries and low-pressure system in the posterior arteries, there is a reversed flow in the posterior intercostals, meaning they dilate to accommodate the high pressure and when the heart beats they pulsate and rub up against the ribs slowly wearing away the bone (rib notching; 3-9 and particularly 3 & 4). - Because there's a high pressure in both the anterior and posterior intercostal arteries for ribs 1 and 2, there's no reverse blood flow and there is no rib notching. - Treatment: balloon dilation, surgically remove coarctation. Superior Vena Cava Veins of the Systemic Circulation - The veins of the systemic circulation is to divide them into their own systems 1) Veins of the heart 2) Veins of the inferior vena cava – drains the lower half of the body. 3) Veins of the superior vena cava – drains the upper half of the body. 4) Portal system – drains nutrients from the intestines and waste products from the spleen and dumps them into the liver to be processed, which then lead the blood into the inferior vena cava again. Superior Vena Cava - Short vein. - Large diameter: ~2-3 cm. - It carries deoxygenated blood from the upper half of the body; head, neck, upper limbs, thorax, and upper part of the back, and descends vertically to empty into the right atrium at the level of the 3rd sternocostal joint. Azygos Vein - An unpaired vein located behind the inferior vena cava, on the right side of the vertebral column. - Receives blood from the right ascending lumbar vein, a tributary of the common iliac vein, which becomes the Azygos vein at T12. - Ascends along the right side of the vertebral column and arches anteriorly at the level of T4, to empty into the superior vena cava. - The Greek root zyg refers to a pair / 'A-' means not → a-zygos = unpaired. - Found only on the right side of the vertebral column, while on the left side, is the hemiazygos and its accessory on the left side of the body.  - The azygous and hemiazygous veins are valveless, in contrast to other veins that have valves to prevent backflow of blood, therefore they may function as portocaval and cavo-caval anastomoses. - If there's a liver disease that causes narrowing of the portal vein, the blood starts shunting over to other places since it can't get through the liver, so it goes through esophageal branches of the azygos vein causing esophageal varices. Tributaries Visceral Tributaries 1. Esophageal Veins - Drain the esophagus. 2. Bronchial Veins - Drain into the azygos vein. 3. Pericardial Veins 4. Mediastinal Veins - Drain various structures in the mediastinum like lymph nodes. Parietal Tributaries 1. Hemiazygos Vein - Receives blood from the left ascending lumbar vein at T12 and empties into the azygos vein at around T8 to T9. Acessory Hemiazygos Vein - A little higher up. - Receives blood from the left 4-7th intercostal veins. - It can either anastomose with the left superior intercostal veins of the left brachiocephalic vein, or just start from the 4-7th left intercostal veins. - And in the lower direction; it can either anastomose with the hemiazygos vein or azygos vein. 2. Right Superior Intercostal Veins - Drain the 2nd and 3rd right intercostal spaces (sometimes 4th).  3. Right Posterior Intercostal Veins - Drain the lower 8 right intercostal spaces. 4. Superior Phrenic Vein - Associated with the Diaphragm. Left Thoracic Veins Left Posterior Intercostal Veins - Draining into the accessory hemiazygos vein and the hemiazygos vein. Right Brachiocephalic Vein - As the superior vena cava ascends, it splits into the right and the left brachiocephalic veins, which are formed by a union of the subclavian vein and internal jugular vein. - ~ 3 cm long. Tributaries 1. Right Vertebral Vein - Drains the external and internal vertebral venous plexuses and the deep muscles of the back in the neck region, collecting all of that blood; then it goes down through the transverse foramina together with the vertebral artery and then opens into the right brachiocephalic vein. 2. Right Inferior Thyroid Vein - Originates from a glandular venous plexus at the thyroid gland and then descends superficially to the trachea and inserts into the brachiocephalic veins. 3. Right Internal Thoracic Vein - Follows the same path as the internal thoracic artery. - Descends along the anterior wall of the thoracic cavity, mainly draining the upper 5-6 intercostal spaces; then at the level of the 7th rib, it receives blood from 2 veins: Musculophrenic Vein - Receives blood from the lower 5-6 intercostal spaces, as the anterior intercostal branches. Superior Epigastric Vein - Passes the diaphragm at the sternocostal triangle and communicates with the inferior epigastric vein. * All of these anterior intercostal veins communicate with the posterior intercostal veins. 4. Right Supreme Intercostal Vein - Drain the upper 1-2 intercostal spaces. Left Brachiocephalic Vein - ~ 6 cm long. Tributaries 1. Left Vertebral Vein 2. Left Inferior Thyroid Vein 3. Left Internal Thoracic Vein 4. Left Supreme Intercostal Vein 5. Left Superior Intercostal Vein - Drain the upper 3-4 intercostal spaces of the left side. 6. Thymic Veins - Drain the thymus. 7. Pericardiophrenic Veins - Drain the tributaries from the superior diaphragm and pericardium The Inferior Vena Cava Topography of Inferior Vena Cava - At the level of the L5, the right and left common iliac veins, forming the inferior vena cava. - Largest vein of the human body. - Collects blood from the lower half of the bod, below the diaphragm. - No valves. - Runs on the right side of the vertebral column. - Lies on the right side of the abdominal aorta. - Forms the right sagittal groove on the posterior surface of the liver. - Goes through the diaphragm through the caval opening, together with the right phrenic nerve. Tributaries of Inferior Vena Cava Visceral Tributaries - Drain organs. Hepatic Veins - 3 large intrahepatic veins: 1. Right Hepatic Vein 2. Intermediate Hepatic Vein 3. Left Hepatic Vein - Drain the liver parenchyma into the inferior vena cava. - Blood from the portal system goes into the liver to be filtered and processed then it flows through the hepatic veins into the systemic circulation. Right Suprarenal Vein - Drain the suprarenal gland into the inferior vena cava. Left Renal Vein - Drain the left kidney into the inferior vena cava. - Tributaries (drain into the left renal vein): 1. Left Suprarenal Vein – drain the suprarenal gland. 2. Left Testicular Vein – drain the left testes. 3. Left Ovarian Vein – drain the left ovary. Right Renal Vein - Drain the right kidney into the inferior vena cava. - Tributaries (drain into the right renal vein): 1. Right Testicular Vein – drain the right testes. 2. Right Ovarian Vein – drain the right ovary. * The ovarian and testicular veins drain into the Pampiniform plexus, which lies on the posterior aspect of the ovaries and the testes. Parietal Tributaries - Drain bones and muscles. Lumbar Veins - 4 pairs of lumbar veins, which follow the lumbar arteries (abdominal aorta). - Communicate with the external and internal vertebral venous plexuses to drain the spinal cord and with the ascending lumbar veins, which drain into the azygos and the hemiazygos veins. Inferior Phrenic Veins - Drain the inferior side of the diaphragm into the inferior vena cava. The Portal System - An arrangement of blood vessels such that blood passes from a capillary, into larger blood vessels and then into another capillary bed. - Drain the blood from the unpaired visceral organs of the abdominal cavity; large intestine, small intestine, pancreas, stomach, spleen, gallbladder. - Blood from these organs will go to the portal vein within the hepatoduodenal ligaments into the liver then bifurcate into the right and the left branches and divide into smaller branches to supply the hepatic lobes. Portal Vein - Formed by 3 major veins: 1. Superior Mesenteric Vein 2. Splenic Vein 3. Inferior Mesenteric Vein Superior Mesenteric Vein Tributaries - Passes on the right side of the superior mesenteric artery, goes behind the pancreas and continues down to terminate as the jejunal and ileal veins. 1. Jejunal and ileal veins – drain from the loops of the jejunum and the ilium. 2. Right Colic Vein – drain the ascending colon. 3. Ileocolic Vein – drain the terminal part of the small intestine and the cecum. 4. Appendicular vein – drain the appendix. 5. Middle Colic Vein – drain the transverse colon. 6. Right Gastro-omental Vein – drain the greater curvature of the stomach and the greater momentum of the peritoneum. - All of these veins drain into the superior mesenteric which drains into the portal vein. Inferior Mesenteric Vein Tributaries - Drain into the splenic vein (mainly), superior mesenteric or portal vein. 1. Superior Rectal Vein – drain the superior part of the rectum or the rectal ampulla. 2. Sigmoid Vein – drain the sigmoid colon. 3. Left Colic Vein – drain the descending colon. - All of these veins drain into the inferior mesenteric which drains into the splenic vein. Splenic Vein Tributaries - Originates from the splenic helium then passes behind the stomach and the pancreatic body to join the superior mesenteric vein in forming the portal vein. 1. Left Gastro-omental Vein – communicates with the right gastrointel vein. 2. Short gastric Veins – drain the fundus and the upper greater curvature of the stomach. 3. Pancreatic Veins – arise along the surface of the pancreatic body and drain it into the splenic vein. - All of these veins drain into the splenic vein which drains into the portal vein. Tributaries 1. Left Gastric Vein – drain the lesser curvature. Anastomose with the right gastric vein to form a venous arch along the lesser curvature. 2. Esophageal Veins – drain the abdominal part of the esophagus. 3. Right Gastric Vein – drain the lesser curvature. 4. Prepyloric Vein – drain the pyloric part of the stomach. 5. Pancreaticoduodenal Veins – drain the head of the pancreas and the duodenum. Empties into the portal vein and superior mesenteric vein.  6. Cystic Vein – drain the gallbladder. 7. Paraumbilical Veins – drain the anterior part of the abdominal wall and some parts of the diaphragm into the liver. 2 thin veins passing along the round ligament of the liver. - All of these veins unite to form the portal vein, which then goes into the liver and branches off to various lobes and then the hepatic veins drain blood from the liver into the inferior vena cava. Portal Hypertension Manifestations - Portal hypertension is an increase in the pressure within the portal vein, which carries blood from the digestive organs to the liver. - In the liver, the blood passes through liver sinusoids and finally exits through the hepatic veins, which empty into the vena cava of the general circulation. Causes of Portal Hypertension 1. Hepatic causes Account for over 95% of cases. Cirrhosis, caused by: Increase in intrahepatic vascular resistance – fibrosis narrows the vessels causing blood to back up in the portal venous system, therefore increasing the pressure. Alcoholic liver damage. Nonalcoholic fatty liver disease. Hepatitis C infection. Other metabolic causes. 2. Pre-haptic causes Affect the portal venous system before it enters the liver: Portal vein thrombosis. Splenic vein thrombosis. Tumor. 3. Post-hepatic causes Anything that affects the draining of the liver.  Hepatic vein thrombosis. Right-sided heart failure – blood will start to build up in the superior and the inferior vena cava which congests the blood inside the portal system. Consequences of Portal Hypertension - If the portal system is blocked for any reason, the blood needs to find a way back to the heart, and so it reverses flow back down the portal system into other veins; the splenic vein, umbilical vein, hemorrhoidal veins, and esophageal veins. - Due to portal hypertension, there may be: 1. Upper gastrointestinal bleeding - These veins are not accustomed to handling such large blood volume and they dilate, causing varices, which are very fragile, and could easily rupture, causing massive upper gastrointestinal bleeding. 2. Hemorrhoids - Veins in the rectum and anal canal enlarge, causing hemorrhoids. 3. Congestive Splenomegaly - As blood backs up into the spleen, it enlarges (congestive splenomegaly), and starts overdoing its job, which causes an increased removal of blood elements and can lead to anemia. 4. Ascites - Endothelial cells lining the blood vessels release more nitric oxide, causing the peripheral arteries to dilate, so blood pressure drops. - This stimulates the release of aldosterone, which tries to bring blood pressure back up by making the kidneys to retain more sodium and water. - As plasma volume expands, fluid in blood vessels gets pushed into large open spaces like the peritoneal cavity, leading to ascites. Porto-Caval Anastomoses - Anastomoses between veins of the portal venous system (tributaries of the portal vein) and veins of the caval venous system (tributaries of the superior or inferior vena cava).  - Under normal conditions, there is minimal/no blood flow through these anastomoses. - Under portal hypertension, the blood needs to escape the portal system through the porto-caval anastomosis as it is not flowing through the liver efficiently, this causes increased pressure within the caval veins, leading to varices or ascites. Esophageal Veins - Anastomoses between the left gastric vein (portal system) and the azygos and hemiazygos veins (caval system), which empty into the superior vena cava. - Manifests esophageal varices in portal hypertension. Rectum and Anal Canal - Anastomoses between the: Superior rectal vein (portal system) – drain into the inferior mesenteric vein. Middle rectal vein (caval system) – drain into the internal iliac. Inferior rectal vein (caval system) – drain into the internal pudendal vein. - Manifests internal hemorrhoids (hemorrhoidal plexus) or anorectal varices in portal hypertension. Paraumbilical Veins and the Subcutaneous Veins Around the Umbilicus - Anastomoses between the paraumbilical veins (portal system) and the superior and inferior epigastric veins (caval system). - Manifests caput medusae (enlarged veins around the umbilicus) and ascites in portal hypertension. Colonic Veins - Anastomoses between the colonic veins (portal system) and the retroperitoneal veins (caval system). - Manifests colonic varices in portal hypertension. TIPS Procedure - Transjugular Intrahepatic Portosystemic Shunt (TIPS) between the portal vein and hepatic vein relieves portal hypertension by shunting blood to the systemic circulation, bypassing the liver. - Patients of portal hypertension may be asymptomatic or symptomatic due to variceal bleeding, ascites, encephalopathy, or hypersplenism. - Variceal hemorrhage occurs most commonly at the gastroesophageal junction and results in death. - Procedure: Incision is made in the neck to access the internal jugular vein. Guide wire is inserted to the right hepatic vein and then a catheter is inserted after. Wire is removed and a balloon at the tip of the catheter measures the indirect pressure. After the catheter is removed, a wire is inserted and thrusted against the wall of the hepatic vein and parenchyma into a major branch of the portal vein to confirm proper placement. Pigtail is inserted and direct pressure is measured in the portal vein. Balloon catheter is used to dilate the track between the hepatic and portal veins. Stent is placed after the balloon is removed. The Lymphatic System - The lymphatic system is a one-direction, open-ended network of vessels acting as a drainage system that removes excess fluid from body tissues and returns it to the bloodstream. - It is a mix of the circulatory and immune system. Lymphatic Vessels - Lymphatic vessels begin as lymphatic capillaries made of endothelial cells that function as a one-way valve. - As interstitial pressure increases, the endothelial cells are pressed inward, opening the gaps, thus allowing backflow.  - As capillary pressure increases, the endothelial cells are pressed outward, closing the gaps, thus preventing backflow. - The gaps in lymphatic capillaries are so large that they allow bacteria, immune cells; macrophages, to enter the bloodstream. - The recovered fluid that enters the lymphatic vessels is called lymph. - Lymph flow is enabled by the same forces that facilitate blood flow in the veins, it goes from lymphatic capillaries to larger and larger lymphatic vessels and eventually drains into the bloodstream via the subclavian veins. - Lymphatic vessels ultimately converge as 2 large trunks: 1. Thoracic Duct Begins in the abdomen at the cisterna chyli, which is the dilated junction of the intestinal, lumbar, and descending intercostal trunks. Drains the lower limbs, pelvis, abdomen, left sides of the thorax, upper limb, head and neck. Passes through the aortic opening of the diaphragm and ascends through the posterior mediastinum between the aorta and the azygos vein. Arches laterally over the apex of the left pleura and between the left carotid sheath in front and the vertebral artery behind, runs behind the left internal jugular vein, and then empties into the junction of the left internal jugular and subclavian veins. 2. Right Lymphatic Duct Drains the right sides of the thorax, upper limb, head, and neck. Empties into the junction of the right internal jugular and subclavian veins. Lymph Nodes - Lymph nodes are small bean-shaped structures, which serve as filters, scattered throughout the lymphatic network, most prominent in the areas where the vessels converge. - Lymph passes through lymph nodes to cleanse it before it reaches the bloodstream. - Lymph nodes contain: Macrophages Dendritic cells – directly “swallow up” any pathogens.  Lymphocytes – T-cells and B-cells, which are involved in adaptive immune response to produce activated lymphocytes and antibodies specific to the invading pathogen, which are then carried by the lymph to the bloodstream to be distributed. Lymphoid Organs - Primary lymphoid organs – sites of lymphocyte production, maturation and selection: Thymus Bone marrow - Selection – the process in which lymphocytes distinguish between self and non-self, so they can recognize and destroy pathogens without attacking the body’s own cells. - Secondary lymphoid organs: Lymph nodes Spleen Lymphoid nodules The Diaphragm - Structures perforating diaphragm: At T8 – IVC, right phrenic nerve. At T10 – esophagus, vagus (CN 10; 2 trunks). At T12 – aorta, thoracic duct, azygos vein. Blood Supply of the Upper Limbs Arteries of the Upper Limbs Axillary Artery - As the right and left subclavian arteries cross the lateral border of the 1st rib to enter the axilla, they become known as the axillary artery. - The pectoralis minor muscle runs in front of the axillary artery and divides it into 3 parts. First Part - Lies proximal to the pectoralis minor. - 1 branch: Superior thoracic artery. Second Part - Lies underneath the pectoralis minor. - 2 branches: Acromial thoracic trunk (thoracoacromial artery) Lateral thoracic artery Third Part - Lies distal to the pectoralis minor. - 3 branches: Anterior circumflex humeral artery – in front of the surgical neck of the humerus. Posterior circumflex humeral artery. Subscapular artery – largest branch of the axillary artery. Brachial Artery - At the level of the lower border of the teres major muscle, which marks the lower boundary of the axilla, the axillary artery becomes the brachial artery.  - The brachial artery runs down the arm to end at the level of the neck of the radius, where it then divides into the radial and ulnar arteries. Profunda Brachii Artery - The deep artery and largest branch of the arm. - Passes posteriorly to supply the posterior compartment of the arm. - Terminates by dividing into 2 branches: 1. Radial collateral artery – anastomoses anteriorly with the radial recurrent artery (branch of the radial artery). 2. Middle collateral artery – anastomoses posteriorly with the interosseous recurrent artery (branch of the posterior interosseous artery). Humeral Nutrient Artery Superior Ulnar Collateral Artery - Coming off superiorly from the brachial artery. - Anastomoses with anterior ulnar recurrent artery (branch of ulnar artery). Inferior Ulnar Collateral Artery - Coming off inferiorly from the brachial artery. - Anastomoses with posterior ulnar recurrent artery (branch of ulnar artery). Clinical Correlation - If the brachial artery is tied off distal to the inferior ulnar collateral artery, sufficient blood reaches the ulnar and radial arteries via the existing anastomoses around the elbow. - The brachial artery may be felt for pulse or blood pressure on the brachialis against the humerus but medial to the biceps and its tendon. Radial and Ulnar Arteries - The brachial artery terminates by dividing into the radial and ulnar arteries. Radial Proximal Branches 1. Radial recurrent artery – anastomoses with the radial collateral artery. Ulnar Proximal Branches 1. Anterior ulnar current artery – anastomoses with superior ulnar collateral artery. 2. Posterior ulnar current artery – anastomoses with inferior ulnar collateral artery. 3. Common interosseous artery – divides into 2 branches: A) Anterior interosseous artery B) Posterior interosseous artery Interosseous recurrent artery – anastomoses with the middle collateral artery (branch of profunda brachii artery). Radial and Ulnar Distal Branches - The radial artery supplies the thumb and the lateral half of the index finger. - The ulnar artery supplies the medial half of the index finger and fingers three four and five. - The distal branch of radial and ulnar arteries form 3 arches of the hand: 1. Superficial palmar arterial arch Lies superficial to the flexor tendons and deep to the palm aponeurosis. Formed by an anastomosis between the ulnar artery and the superficial palmar branch of the radial artery. The ulnar artery terminates by forming it. 2. Deep palmar arterial arch Lies deep to the flexor tendons and is between the flexor tendons and the metacarpal bones. Formed by an anastomosis between the radial artery and the deep palmar branch of the ulnar artery.  3. Dorsal carpal arterial arch Formed by an anastomosis between the dorsal carpal branch of the radial artery and the dorsal carpal branch of the ulnar artery. Radial Pulse - The radial pulse may be felt: Proximal to the wrist between the tendons of the brachioradialis and flexor carpi radialis muscles. In the anatomic snuffbox between the tendons of the extensor pollicis longus and brevis muscles. Veins of the Upper Limbs Veins of the Hand Superficial Veins 1. Dorsal digital veins – unite to form dorsal metacarpal veins. 2. Palmar digital veins – drain into the dorsal digital veins via intercapitular branches. 3. Dorsal venous network Deep Veins 1. Superficial venous palmar arch (palmer venous network) 2. Deep venous palmar arch 3. Dorsal metacarpal veins – drain into the dorsal venous network. 4. Palmar metacarpal veins Veins of the Forearm Superficial Veins 1. Cephalic vein – arise laterally from the dorsal venous network.  2. Basilic vein – arise medially from the dorsal venous network. - They curve round anteriorly, just before the elbow joint; at the antecubital fossa, the cephalic and basilic veins are joined; there's a lot of anatomical variation from individual to individual. 3. Median antebrachial vein – drains the palmar venous network and ascends splitting into 2 veins: A) Median cephalic vein. B) Median basilic vein. - The cephalic vein may directly drain into the basilic vein via the median cubital vein. - The median antebrachial vein may directly drain into the basilic vein rather than forming these 2 veins. - The veins in the antecubital fossa are common sites for venipuncture, as they are large and superficial. Deep Veins 1. Anterior interosseous veins 2. Posterior interosseous veins 3. Ulnar veins 4. Radial veins Veins of the Arm and Axilla Superficial Veins 1. Cephalic vein – ascends lateral to the biceps brachii muscle, passing through the deltopectoral groove, between the deltoid muscle and the pectoralis major muscle, then passes into the deltoid pectoral triangle (clavicle triangle) where it pierces the clavi-pectoral fascia to drain into the axillary vein. * The deltoid pectoral triangle is a triangle bordered by the pectoralis major muscle, the deltoid muscle, and the clavicle. 2. Basilic vein – ascends medially and it pierces the brachial fascia to enter the deep compartment of the arm to drain into the deep brachial veins. Deep Veins 1. Brachial veins – paired veins which accompany the brachial artery and drain into the axillary vein at the level of the inferior margin of the teres major muscle. 2. Axillary vein – a continuation of the brachial vein after the point where the basilic vein drains into, it then becomes the subclavian vein. 3. Subclavian vein – joins the internal jugular vein to drain into the brachiocephalic veins (innominate veins) that drain into the superior vena cava into the right atrium. Clinical Correlation - Venipuncture may be performed on the: Axillary vein – locate the central line. Median cubital vein – draw blood. Dorsal venous network – long-term introduction of fluids or intravenous feeding. Cephalic vein – long-term introduction of fluids or intravenous feeding. Basilic vein – long-term introduction of fluids or intravenous feeding. Axillary Lymph Nodes Blood Supply of the Lower Limbs Arteries of the Lower Limbs  - The abdominal aorta splits into right and left common iliac arteries, which further divide into internal and external common iliac arteries. Arteries of the Thigh External Iliac Artery - As it crosses under the inguinal ligament to enter the femoral triangle, it becomes the common femoral artery. Common Femoral Artery 1. Profunda femoris artery – deep branch of common femoral artery. A) Lateral circumflex artery B) Medial circumflex artery C) Perforating branches – termination of the profunda femoris artery, they perforate the adductor magnus muscle. 2. Superficial femoral artery – travels through the adductor canal, a muscular tunnel beginning at the femoral triangle and ending at the adductor hiatus. Arteries of the Leg Popliteal Artery - As the SFA enters the posterior compartment of the thigh through the adductor hiatus, it becomes the popliteal artery. - It passes between the gastrocnemius and popliteus muscles. - It terminates by dividing into several branches: 1. Genicular branches – supply the knee joint. 2. Anterior tibial artery – descends in the anterior compartment of the leg through a gap in the interosseous membrane, and enters the foot becoming the dorsalis pedis artery.  3. Posterior tibial artery – descends in the posterior compartment of the leg and enters the foot via the tarsal tunnel, winding behind the medial malleolus and splitting into the lateral and medial plantar arteries. Fibular artery (peroneal artery) – supply the lateral compartment of the leg. Arteries of the Foot Dorsalis Pedis Artery - A continuation of the anterior tibial artery as it descends to the foot. 1. Deep plantar artery Between the first and second metatarsals. Anastomoses with the lateral plantar artery to form the deep plantar arch. Lateral and Medial Plantar Arteries - A continuation of the posterior tibial artery as it descends to the foot. Veins of the Lower Limbs Superficial Veins Great Saphenous Vein (long) - Arises from the medial aspect of the dorsal venous arch. - Passes in front of the medial malleolus to ascend up the medial aspect of the leg, along the entire length of the lower limb. - Drains into the femoral vein. Small Saphenous Vein (short) - Arises from the lateral aspect of the dorsal venous arch. - Passes behind the lateral malleolus to ascend up the posterior aspect of the leg. - Drains into the popliteal vein behind the knee joint. * Dorsal venous arch – drains the dorsal aspect of the foot. * Plantar venous network – drains the plantar aspect of the foot. Perforating Veins - Small little veins which pass directly from the superficial to the deep venous system. Deep Veins Veins of the Foot 1. Deep dorsal veins Drain into the anterior tibial vein. 2. Deep plantar veins Drain into the posterior tibial vein. Lateral and medial plantar veins that form the deep plantar venous arch, accompanying the lateral and medial plantar veins that form the deep plantar arterial arch. Veins of the Leg 1. Anterior tibial veins Accompanies the anterior tibial artery. Drains into the popliteal vein. 2. Posterior tibial veins Accompanies the posterior tibial artery. Runs behind the medial malleolus. Drains into the popliteal vein. 3. Fibular veins Accompanies the fibular artery. Drains the lateral compartment of the leg. Veins of the Knee 1. Popliteal vein Accompanies the popliteal artery.  Passes from the posterior compartment to the anterior compartment of the thigh through the adductor hiatus → becomes the femoral vein. Veins of the Thigh 1. Femoral vein A) Profunda femoris vein – accompanies the profunda femoris artery. Lateral circumflex vein. Medial circumflex vein. Perforating branches. 2. External Iliac vein A continuation of the femoral vein as it crosses under the inguinal ligament to enter the femoral triangle. 3. Internal Iliac vein * The external iliac vein then joins the internal iliac vein to become the common iliac vein. The left and right common iliac veins then unite to form the inferior vena cava. Clinical Correlation - Deep vein thrombosis (DVT) – clot in deep veins of the leg → deep veins of the thigh → iliac system → inferior vena cava → right side of the heart → pulmonary circulation → pulmonary infarct → pulmonary embolus. - Femoral Necrosis – the lateral and medial circumflex arteries of the femoral artery. Valves - To prevent the backflow of blood from the deep (high pressure) to the superficial system (low pressure), there are valves: Between the great saphenous vein and the femoral vein. Between the small saphenous vein and the popliteal vein. - If these valves become incompetent, the superficial veins dilate up and take on a tortuous appearance, because of the backflow of blood → varicose vein. Blood Supply of the Upper Limbs Arteries of the Upper Limbs Axillary Artery - As the right and left subclavian arteries cross the lateral border of the 1st rib to enter the axilla, they become known as the axillary artery. - The pectoralis minor muscle runs in front of the axillary artery and divides it into 3 parts. First Part - Lies proximal to the pectoralis minor. - 1 branch: Superior thoracic artery. Second Part - Lies underneath the pectoralis minor. - 2 branches: Acromial thoracic trunk (thoracoacromial artery) Lateral thoracic artery Third Part - Lies distal to the pectoralis minor. - 3 branches: Anterior circumflex humeral artery – in front of the surgical neck of the humerus. Posterior circumflex humeral artery. Subscapular artery – largest branch of the axillary artery. Brachial Artery - At the level of the lower border of the teres major muscle, which marks the lower boundary of the axilla, the axillary artery becomes the brachial artery.  - The brachial artery runs down the arm to end at the level of the neck of the radius, where it then divides into the radial and ulnar arteries. Profunda Brachii Artery - The deep artery and largest branch of the arm. - Passes posteriorly to supply the posterior compartment of the arm. - Terminates by dividing into 2 branches: 1. Radial collateral artery – anastomoses anteriorly with the radial recurrent artery (branch of the radial artery). 2. Middle collateral artery – anastomoses posteriorly with the interosseous recurrent artery (branch of the posterior interosseous artery). Humeral Nutrient Artery Superior Ulnar Collateral Artery - Coming off superiorly from the brachial artery. - Anastomoses with anterior ulnar recurrent artery (branch of ulnar artery). Inferior Ulnar Collateral Artery - Coming off inferiorly from the brachial artery. - Anastomoses with posterior ulnar recurrent artery (branch of ulnar artery). Clinical Correlation - If the brachial artery is tied off distal to the inferior ulnar collateral artery, sufficient blood reaches the ulnar and radial arteries via the existing anastomoses around the elbow. - The brachial artery may be felt for pulse or blood pressure on the brachialis against the humerus but medial to the biceps and its tendon. Radial and Ulnar Arteries - The brachial artery terminates by dividing into the radial and ulnar arteries. Radial Proximal Branches 1. Radial recurrent artery – anastomoses with the radial collateral artery. Ulnar Proximal Branches 1. Anterior ulnar current artery – anastomoses with superior ulnar collateral artery. 2. Posterior ulnar current artery – anastomoses with inferior ulnar collateral artery. 3. Common interosseous artery – divides into 2 branches: A) Anterior interosseous artery B) Posterior interosseous artery Interosseous recurrent artery – anastomoses with the middle collateral artery (branch of profunda brachii artery). Radial and Ulnar Distal Branches - The radial artery supplies the thumb and the lateral half of the index finger. - The ulnar artery supplies the medial half of the index finger and fingers three four and five. - The distal branch of radial and ulnar arteries form 3 arches of the hand: 1. Superficial palmar arterial arch Lies superficial to the flexor tendons and deep to the palm aponeurosis. Formed by an anastomosis between the ulnar artery and the superficial palmar branch of the radial artery. The ulnar artery terminates by forming it. 2. Deep palmar arterial arch Lies deep to the flexor tendons and is between the flexor tendons and the metacarpal bones. Formed by an anastomosis between the radial artery and the deep palmar branch of the ulnar artery.  3. Dorsal carpal arterial arch Formed by an anastomosis between the dorsal carpal branch of the radial artery and the dorsal carpal branch of the ulnar artery. Radial Pulse - The radial pulse may be felt: Proximal to the wrist between the tendons of the brachioradialis and flexor carpi radialis muscles. In the anatomic snuffbox between the tendons of the extensor pollicis longus and brevis muscles. Veins of the Upper Limbs Veins of the Hand Superficial Veins 1. Dorsal digital veins – unite to form dorsal metacarpal veins. 2. Palmar digital veins – drain into the dorsal digital veins via intercapitular branches. 3. Dorsal venous network Deep Veins 1. Superficial venous palmar arch (palmer venous network) 2. Deep venous palmar arch 3. Dorsal metacarpal veins – drain into the dorsal venous network. 4. Palmar metacarpal veins Veins of the Forearm Superficial Veins 1. Cephalic vein – arise laterally from the dorsal venous network.  2. Basilic vein – arise medially from the dorsal venous network. - They curve round anteriorly, just before the elbow joint; at the antecubital fossa, the cephalic and basilic veins are joined; there's a lot of anatomical variation from individual to individual. 3. Median antebrachial vein – drains the palmar venous network and ascends splitting into 2 veins: A) Median cephalic vein. B) Median basilic vein. - The cephalic vein may directly drain into the basilic vein via the median cubital vein. - The median antebrachial vein may directly drain into the basilic vein rather than forming these 2 veins. - The veins in the antecubital fossa are common sites for venipuncture, as they are large and superficial. Deep Veins 1. Anterior interosseous veins 2. Posterior interosseous veins 3. Ulnar veins 4. Radial veins Veins of the Arm and Axilla Superficial Veins 1. Cephalic vein – ascends lateral to the biceps brachii muscle, passing through the deltopectoral groove, between the deltoid muscle and the pectoralis major muscle, then passes into the deltoid pectoral triangle (clavicle triangle) where it pierces the clavi-pectoral fascia to drain into the axillary vein. * The deltoid pectoral triangle is a triangle bordered by the pectoralis major muscle, the deltoid muscle, and the clavicle. 2. Basilic vein – ascends medially and it pierces the brachial fascia to enter the deep compartment of the arm to drain into the deep brachial veins. Deep Veins 1. Brachial veins – paired veins which accompany the brachial artery and drain into the axillary vein at the level of the inferior margin of the teres major muscle. 2. Axillary vein – a continuation of the brachial vein after the point where the basilic vein drains into, it then becomes the subclavian vein. 3. Subclavian vein – joins the internal jugular vein to drain into the brachiocephalic veins (innominate veins) that drain into the superior vena cava into the right atrium. Clinical Correlation - Venipuncture may be performed on the: Axillary vein – locate the central line. Median cubital vein – draw blood. Dorsal venous network – long-term introduction of fluids or intravenous feeding. Cephalic vein – long-term introduction of fluids or intravenous feeding. Basilic vein – long-term introduction of fluids or intravenous feeding. Axillary Lymph Nodes Blood Supply of the Lower Limbs Arteries of the Lower Limbs  - The abdominal aorta splits into right and left common iliac arteries, which further divide into internal and external common iliac arteries. Arteries of the Thigh External Iliac Artery - As it crosses under the inguinal ligament to enter the femoral triangle, it becomes the common femoral artery. Common Femoral Artery 1. Profunda femoris artery – deep branch of common femoral artery. A) Lateral circumflex artery B) Medial circumflex artery C) Perforating branches – termination of the profunda femoris artery, they perforate the adductor magnus muscle. 2. Superficial femoral artery – travels through the adductor canal, a muscular tunnel beginning at the femoral triangle and ending at the adductor hiatus. Arteries of the Leg Popliteal Artery - As the SFA enters the posterior compartment of the thigh through the adductor hiatus, it becomes the popliteal artery. - It passes between the gastrocnemius and popliteus muscles. - It terminates by dividing into several branches: 1. Genicular branches – supply the knee joint. 2. Anterior tibial artery – descends in the anterior compartment of the leg through a gap in the interosseous membrane, and enters the foot becoming the dorsalis pedis artery.  3. Posterior tibial artery – descends in the posterior compartment of the leg and enters the foot via the tarsal tunnel, winding behind the medial malleolus and splitting into the lateral and medial plantar arteries. Fibular artery (peroneal artery) – supply the lateral compartment of the leg. Arteries of the Foot Dorsalis Pedis Artery - A continuation of the anterior tibial artery as it descends to the foot. 1. Deep plantar artery Between the first and second metatarsals. Anastomoses with the lateral plantar artery to form the deep plantar arch. Lateral and Medial Plantar Arteries - A continuation of the posterior tibial artery as it descends to the foot. Veins of the Lower Limbs Superficial Veins Great Saphenous Vein (long) - Arises from the medial aspect of the dorsal venous arch. - Passes in front of the medial malleolus to ascend up the medial aspect of the leg, along the entire length of the lower limb. - Drains into the femoral vein. Small Saphenous Vein (short) - Arises from the lateral aspect of the dorsal venous arch. - Passes behind the lateral malleolus to ascend up the posterior aspect of the leg. - Drains into the popliteal vein behind the knee joint. * Dorsal venous arch – drains the dorsal aspect of the foot. * Plantar venous network – drains the plantar aspect of the foot. Perforating Veins - Small little veins which pass directly from the superficial to the deep venous system. Deep Veins Veins of the Foot 1. Deep dorsal veins Drain into the anterior tibial vein. 2. Deep plantar veins Drain into the posterior tibial vein. Lateral and medial plantar veins that form the deep plantar venous arch, accompanying the lateral and medial plantar veins that form the deep plantar arterial arch. Veins of the Leg 1. Anterior tibial veins Accompanies the anterior tibial artery. Drains into the popliteal vein. 2. Posterior tibial veins Accompanies the posterior tibial artery. Runs behind the medial malleolus. Drains into the popliteal vein. 3. Fibular veins Accompanies the fibular artery. Drains the lateral compartment of the leg. Veins of the Knee 1. Popliteal vein Accompanies the popliteal artery.  Passes from the posterior compartment to the anterior compartment of the thigh through the adductor hiatus → becomes the femoral vein. Veins of the Thigh 1. Femoral vein A) Profunda femoris vein – accompanies the profunda femoris artery. Lateral circumflex vein. Medial circumflex vein. Perforating branches. 2. External Iliac vein A continuation of the femoral vein as it crosses under the inguinal ligament to enter the femoral triangle. 3. Internal Iliac vein * The external iliac vein then joins the internal iliac vein to become the common iliac vein. The left and right common iliac veins then unite to form the inferior vena cava. Clinical Correlation - Deep vein thrombosis (DVT) – clot in deep veins of the leg → deep veins of the thigh → iliac system → inferior vena cava → right side of the heart → pulmonary circulation → pulmonary infarct → pulmonary embolus. - Femoral Necrosis – the lateral and medial circumflex arteries of the femoral artery. Valves - To prevent the backflow of blood from the deep (high pressure) to the superficial system (low pressure), there are valves: Between the great saphenous vein and the femoral vein. Between the small saphenous vein and the popliteal vein. - If these valves become incompetent, the superficial veins dilate up and take on a tortuous appearance, because of the backflow of blood → varicose vein. Blood Supply of the Head and Neck Arteries of Head and Neck Subclavian Artery - Asymmetrical origins: Right subclavian artery – arises from the brachiocephalic trunk. Left subclavian artery – aortic arch. Vertebral Artery * - Ascends through the apex of the triangle between the anterior scalene and longus colli muscles, entering the transverse foramen of the cervical vertebra. - Ascends through the suboccipital triangle, entering the foramen magnum. - Supplies the cerebellum and the posterior part of the cerebrum → posterior circulation the brain. - Both vertebral arteries come together to make up the basilar artery. Thyrocervical Trunk 1. Inferior thyroid artery – supplies the thyroid. 2. Transverse cervical artery – supplies the traps, levator, and rhomboids. 3. Suprascapular artery – supplies the shoulder. - Courses between the anterior and middle scalene muscles. ➔ Subclavian Steal Syndrome Caused by the reversed blood flow from the basilar artery through the vertebral artery into the subclavian artery in the presence of an occlusion of the subclavian artery proximal to the vertebral artery. When there is few blood flow through the vertebral artery, it may steal blood flow from the carotid, circle of Willis, and basilar circulation and divert it into the  subclavian artery into the upper extremities → vertebrobasilar insufficiency + cerebral and brain stem ischemia and stroke. Loss of blood supply to the posterior circulation of the brain through the vertebral artery → dizziness, ataxia, vertigo, diplopia, visual disturbances, dysarthria, motor deficit, confusion, aphasia, headache, syncope, arm weakness, and arm claudication with exercise. Treated by a carotid-subclavian bypass. ➔ Thoracic Outlet Syndrome Neurovascular compression of the lower trunk of the brachial plexus and the subclavian vessels in the thoracic outlet (space between clavicle and 1st rib) between the base of the neck and axilla. Caused by: 1) Abnormal insertion of the anterior and middle scalene muscles → ischemic muscle pain in the upper limb. 2) Cervical rib (cartilaginous elongation of the transverse process of C7) compressing the subclavian artery → impaired circulation. 3) Fractured clavicle → subclavian venous bleeding and thrombosis → pulmonary embolism. 4) Physical trauma and repetitive strain injury. Symptoms: pain, numbness, tingling, and weakness in the upper limb. Its treatment involves physical measures, medications, and surgery. Common Carotid Artery - Asymmetrical origins: Right common carotid artery – arises from the brachiocephalic trunk. Left common carotid artery – aortic arch. - Located within the carotid sheath (cross-section through the C6 cervical vertebrae) along with the internal jugular vein and the vagus nerve. - Carotid pulse – occurs during systole when the left ventricle contracts and forces blood into the common carotid artery and expands it  Palpitation on the side of the neck by the laryngeal cartilage or the Adam's apple. Determination of the heart rate. Internal Carotid Artery * - Hasa carotid sinus and carotid body. - Supplies the anterior part of the brain → anterior circulation of the brain. - Supplies the orbit and part of the forehead of the scalp. Carotid Sinus - Located at the origin of the internal carotid artery. - Baroreceptor → senses changes in blood pressure. Baroreflex: baroreceptor senses changes in blood pressure → CN IX sends signals from the carotid sinus (aortic arch) to the brain stem (solitary nucleus of medulla) → brainstem releases a sympathetic discharge → increases mean arterial pressure → increases heart rate → affects the kidney → renin angiotensin aldosterone system helps to bring blood pressure back to normal. Opposite is true: brainstem also takes parasympathetic or vagal tone to reduce heart rate. ➔ Carotid Sinus Syncope Temporary loss of consciousness or fainting caused by diminished cerebral blood flow. Results from hypersensitivity of the carotid sinus → exaggerated response to pressure applied to the carotid sinus. Carotid Body - Located between the internal and external carotid arteries. - Chemoreceptor: senses changes in blood O2 and CO2 levels. ➔ Carotid Endarterectomy Encision of atherosclerotic thickening of intima of the internal carotid artery. Prevention of stroke in patients with obstructive disease of the carotid artery. External Carotid Artery - Supplies the neck and the face. 1. Superior thyroid artery 2. Superior laryngeal artery 3. Lingual artery – supplies the tongue. 4. Facial artery 5. Ascending pharyngeal artery – smallest branch. 6. Occipital artery – passes through the occipital triangle; the sternocleidomastoid, the traps, and the omohyoid muscle. 7. Posterior auricular artery 8. Maxillary artery – supplies the meninges, muscles, orbit (inferior orbital artery), nasal cavity, maxilla, maxillary teeth and gum, palate, and mandibular teeth, gums and skin. 9. Superficial temporal artery – supplies the temporal region (superficially). ➔ Temporal Arteritis Inflammation with multinucleated giant cells, affecting the medium-sized arteries, especially the temporal artery. Symptoms: severe headache, excruciating pain in the temporal area, temporal artery tenderness, visual impairment, transient diplopia, jaw claudication, fever, fatigue, and weight loss. Cause is unknown. Diagnosed by temporal artery biopsy. Treated with corticosteroids; prednisone. Aortic Arches - The embryo has 2 primitive aortae right and the left, each with 3 parts: ventral aorta, dorsal aorta, and arch. - As the embryo develops, the ventral aorta fuses to form the aortic sac.  - The aortic sac has right and left horns from which the aortic arches arise. - The aortic sac lies superior to the truncus arteriosus of the heart tube. - The dorsal artery caudal to aortic arches fuses to form a single vessel to form the future descending thoracic aorta. Veins of the Head and Neck - Superior vena cava divides into right and left brachiocephalic veins, formed by the internal jugular and the subclavian vein. - The subclavian vein passes below the clavicle to give rise to the external jugular vein. Veins of the Head Internal Jugular Vein - Passes through jugular foramen. - Drains from the sigmoid sinus. 1. Lingual Vein A) Dorsal lingual vein B) Deep lingual vein C) Sublingual vein  2. Common facial vein A) Facial vein Deep facial vein – towards the infratemporal fossa and form pterygoid plexus, that continues posteriorly as… Maxillary vein – connects with the retromandibular vein and form… Superficial temporal vein – supplies parietal and frontal region. B) Anterior root of retromandibular vein – connects with the posterior root of retromandibular vein to form the retromandibular vein. External Jugular Vein 1. Posterior auricular vein 2. Posterior root of retromandibular vein – connects with the anterior root of retromandibular vein to form the retromandibular vein. Occipital Vein - Drains into the posterior auricular vein. - Posterior auricular vein + occipital vein → posterior root of the external jugular vein. - Drains into the internal jugular vein. Veins of the Neck Internal Jugular Vein - Medical Schools Let Confident People In: 1. Middle thyroid vein 2. Superior thyroid vein 3. Lingual vein 4. Common facial vein 5. Pharyngeal vein – drains pharyngeal plexus.  6. Inferior petrosal sinus – drain into cavernous sinus → internal jugular vein. + Sternocleidomastoid vein External Jugular Vein - PAST: 1. Posterior external jugular vein 2. Anterior jugular vein – right and left branches form a jugular venous arch. 3. Suprascapular vein 4. Transverse cervical vein ➔ Central Venous Line An IV needle and catheter placed into a large vein to give fluids or medication. A central line is inserted in the apex of the triangular interval between the clavicle and the clavicular and sternal heads of the sternocleidomastoid muscle into the IJV through which the catheter is threaded into the SVC. A central line is also inserted into the retroclavicular portion of the right subclavian vein, and it should be guided medially along the long axis of the clavicle to reach the posterior surface where the vein runs over the first rib. Cardiac Embryology Heart Morphogenesis - First functional organ in vertebrate embryos. - Beats spontaneously by week 4 of development. Cardiac Looping - Primary heart tube loops to establish left-right polarity in week 4 of development. - Defect in left-right dynein can lead to dextrocardia, seen in Kartagener syndrome. - Initially, the heart consists of a simple tube anchored at one end by the differentiating arterial trunks and at the other end by extensive venous channels, which drain into the atrium. - At both ends, the cardiac tube grows rapidly in length and the embryonic ventricle is bent into a loop to the right of the midline. - As development continues, the ventricular region swings back to the midline and expands and grows in length to cover the atrium and great veins. - Extensive saculations projecting laterally will become the RA and LA. - The future LV lies to the left of the interventricular groove and the embryonic right ventricular region communicates with the truncus arteriosus. Separation of Chambers - Externally a deep groove separates the atrium from the ventricle. - Within the heart, the atrioventricular groove appears as a deep invagination which constricts the atrioventricular canal at its waist. - Endocardial cushions extend from opposite sides of the atrioventricular aperture and ultimately fuse into a column dividing the channel between the atrium and ventricle. Atria 1. Septum primum, rapidly grows toward the endocardial cushions constricting the opening between the atria; the foramen primum. 2. Before the foramen premium becomes obliterated, a new opening forms in septum primum; the foramen secundum, which provides uninterrupted shunting of blood from the RA directly into the LA. 3. Septum secundum develops on the right side of septum primum. 4. Septum secundum expands and covers most of the foramen secundum, leaving a small opening; the foramen ovale. 5. The remaining portion of septum premium acts as a unidirectional membranous valve, thus blood can float only from the RA to the LA. 6. After birth, septum primum closes against septum secundum, because of ↑ LA pressure and ↓ RA pressure. 7. During infancy/early childhood, septum primum and septum secundum fuse, forming the atrial septum. - Patent foramen ovale – caused by failure of septum primum and septum secundum to fuse after birth, which can lead to paradoxical emboli (embolus travels through right-to-left shunt) as in ASD. Ventricles 1. From the interventricular ridge, a proliferating muscular interventricular septum forms. 2. An opening; interventricular foramen, persists between the ventricular cavities. 3. Aorticopulmonary septum spirals and fuses with superior margin of the muscular interventricular septum to form the membranous interventricular septum, closing the interventricular foramen by masses of endocardial tissue from the ventricular septum, endocardial cushions and aorticopulmonary septum. Outflow Tract Formation - Originally, the right and LVs share a common outflow channel; truncus arteriosus, which gives rise to the aortic arches. - The bifurcation of the truncus arteriosus represents two of the aortic arches; fourth forms the aorta and the sixth forms the pulmonary artery. - Neural crest cell migrations → a pair of ridges (truncal and bulbar) spiral down the truncus arteriosus → aorticopulmonary septum → ascending aorta and pulmonary trunk. - Blood from the LV enters the aorta, which passes to the right, behind the pulmonary artery. - Blood from the RV enters the pulmonary artery, which passes in front of the aorta, turning posteriorly on the left side of the mediastinum. - Conotruncal abnormalities associated with failure of neural crest cells to migrate: Transposition of great vessels. Tetralogy of Fallot. Persistent truncus arteriosus. Valve Development - Aortic/pulmonary – derived from endocardial cushions of outflow tract. - Mitral/tricuspid – derived from fused endocardial cushions of the AV canal. Fetal Circulation - Umbilical veins have a PO2, of = 30 mm Hg and is 80% saturated with O2. - Umbilical arteries have low O2 saturation. - 3 important shunts: 1. Ductus venosus 2. Foramen ovale 3. Ductus arteriosus  - The circulatory pattern throughout fetal development: Deoxygenated blood → SVC and IVC → RA → RV→ pulmonary artery → ductus arteriosus → descending aorta OR → lungs → pulmonary veins → LA Oxygenated blood from placenta → ductus venosus → IVC → RA → foramen ovale → LA (mixture of venous and oxygenated blood) → LV → aorta - After birth, the supply of oxygenated blood from the placenta is interrupted and respiratory exchange in the lungs must be established. - At birth, infant takes a breath → ↓ pulmonary vascular resistance → ↑ LA pressure and ↓ RA pressure → foramen ovale closes. - Indomethacin → closes patent ductus arteriosus → ligamentum arteriosum. - Prostaglandins E1 and E2 → keeps PDA open. - Constriction of the ductus arteriosus diverted the entire right ventricular output into the pulmonary circulation. Heart Embryology Embryonic structure Gives rise to Truncus arteriosus Ascending aorta and pulmonary trunk Bulbus cordis Smooth parts the ventricles Primitive ventricle Trabeculated parts of the ventricles Primitive atrium Trabeculated part of the atria Left horn of sinus venous Coronary sinus Right horn of sinus venous Smooth part of RA (sinus venarum) Endocardial cushion Atrial septum, membranous interventricular septum; AV and semilunar valves Right common cardinal vein and right SVC anterior cardinal vein  Posterior, subcardinal, and supracardinal IVC veins Primitive pulmonary vein Smooth part of LA Fetal-postnatal Derivatives Fetal Structure Postnatal Derivative Notes Ductus arteriosus Ligamentum arteriosum Near the left recurrent laryngeal nerve Ductus venosus Ligamentum venosum Foramen ovale Fossa ovalis Allantois → urachus Median umbilical ligament Urachus is part of allantois between bladder and umbilicus Umbilical arteries Medial umbilical ligaments Umbilical vein Ligamentum teres hepatis Contained in falciform ligament (round ligament) Congenital Diseases Right-to-left Shunts - A right-to-left shunt allows the deoxygenated blood to bypass the lungs and return to the body → early cyanosis. Persistent Truncus Arteriosus - The truncus arteriosus is a structure present during fetal development and later divides to form two separate arteries: the aorta and the pulmonary artery. - A persistent truncus arteriosus occurs when it fails to divide and so there is one giant artery that branches off from both the right and the LVs and only then splits off into the aorta and pulmonary artery. - Due to PTA (usually accompanied with VDS), the oxygenated and deoxygenated blood mix, so deoxygenated blood enters the systemic circulation → cyanosis.  - Before birth, since the fetus doesn't use its lungs yet, deoxygenated blood gets sent to the mother and then oxygenated blood comes from the mother and is sent through the foramen ovale into the right side of the heart, therefore there's high vascular resistance and high pressure in the pulmonary circulation. - So even if there's mixing of oxygenated and deoxygenated blood, the fetus is able to cope since the pressures in the two circuits are similar meaning that both circulations get about the same amount of blood. - After birth, the mother stops supplying blood and the foramen ovale closes and the baby starts to rely on their own lungs, therefore there is a low vascular resistance and low pressure in the pulmonary circuit, which is normal. - Now there's a pressure differential between the left and the right side, where the left side is higher than the right side, which is also normal. - However due to TA, the blood is still able to mix and more blood goes to the lungs (lower pressure) and less goes to the body (higher pressure). - Extra blood volume on the right side → fluid overload → beginning of heart failure. - It's associated with chromosome 22q11 deletion → diGeorge syndrome. Transposition of Great Vessels - Transposition of the great arteries or TGA is when the aorta and the pulmonary artery swap locations due to the failure of the aorticopulmonary septum to spiral. - Due to TGA, the one big circuit becomes two smaller circuits. - Left side: blood from LV → pulmonary artery → lungs → LA → LV → restarts. - Right side: blood from RV → aorta → body → RA → RV → restarts. - Therefore, blood on the right side never gets oxygenated and blood on the left side never gets deoxygenated → complete TGA or dextro-TGA (d-TGA). Dextro-TGA  - Before birth, babies are asymptomatic because they're not using their lungs yet and rely on oxygenated from the mother's blood through 3 shunts: foramen ovale, ductus arteriosus or ductus venosus. - After birth, babies start to use their lungs and normally these shunts go away and become ligaments, leading to death, unless there's a way for blood between the pulmonary and systemic circulations to mix and deliver some oxygenated blood to the tissues, such as: Surgical opening of foramen ovale or ductus arteriosus. Ventricular septal defect – 1/3 of cases. Administration of prostaglandin E to keep ductus arteriosus open – short-term. - However, the shunt system isn't very efficient as a significant amount of deoxygenated blood is still sent to the body's tissues → cyanosis. - If a shunt is large enough, the initial symptoms aren't noticed and the TGA isn't repaired → congestive heart failure. - Because the roles of the ventricles have been switched: RV is built for low pressure systems but pumps out to the higher pressure systemic circuit → hypertrophy. LV is built for high pressure systems but pumps out to the lower pressure pulmonary circuit → atrophy. Levo-TGA - The aorta is primarily to the left of the pulmonary artery → levo-TGA (L-TGA) - The great arteries are still connected to the wrong ventricle but it's the ventricles that have transpositioned places along with their atrioventricular valves. - Unlike d-TGA, circulation is preserved, acyanotic, asymptomatic at birth → congenitally corrected TGA. - Because the ventricles and their atrioventricular valves have been switched: RV and tricuspid valve are built for low pressure systems but pump out to the higher pressure systemic circuit → hypertrophy. LV and mitral valve are built for high pressure systems but pump out to the lower pressure pulmonary circuit → atrophy.  - Cause: unknown. - Risk factors: Pregnant women: Has diabetes, rubella, and poor nutrition. Consuming alcohol. > 40 years old. Adults are at a greater risk of heart failure. - Diagnosis: Echocardiogram. Check for TGA, if: Cyanotic at birth. Later symptoms of heart failure later in life. Tricuspid Atresia - Absence of tricuspid valve and hypoplastic RV. - Requires both ASD and VSD for viability. Tetralogy of Fallot - Tetralogy of flow (ToF) is a congenital heart condition causing 4 heart abnormalities. 1) Stenosis - Narrowing of the right ventricular outflow tract into the pulmonary artery; by narrowing of the valve or infundibulum. - Harder for deoxygenated blood to get to the pulmonary circulation. 2) Right Ventricular Hypertrophy - In response to 1, the myocardium of the RV hypertrophes. - Contract harder and push blood past the stenosis → boot-shaped heart. 3) Large Ventricular Septal Defect - This gap between the ventricles allows shunting of blood between them.  - Without ToF – oxygenated blood is shunted from the left side to the right side because the pressure on the left is higher than the pressure on the right. - With ToF – deoxygenated blood is shunted from the right side to the left side because the right ventricular outflow obstruction might block the normal blood flow so much that the pressure in the RV has to be really high to get past it and the left side of the heart becomes the path of least resistance. 4) Overriding Aorta - The aorta overrides the VSD. - The critical feature is the degree of right ventricular outflow obstruction: With less obstruction – oxygenated blood is shunted from the left side to the right side and enters the pulmonary circulation. With more obstruction – deoxygenated blood is shunted from the right side to the left side and enters the systemic circulation. - Shunting can be severe → oxygen saturation falls below 80% → cyanosis. - ToF is the most common cause of ~50 to 70% cyanotic congenital heart defects and ~10% of all congenital heart defects. - It's associated with chromosome 22q11 deletion → diGeorge syndrome. - Signs & symptoms: Cyanosis around their lips and fingernail beds at birth. Clubbing of their fingers and toes within a few months. Feeding difficulty. Failure to gain weight and develop normally. No severe right ventricular outflow obstruction → acyanotic. Tet Spells - Babies with ToF will experience symptoms and cyanosis in tet spells. - O2 demand increases → heart pumps more blood → sudden decrease in O2 saturation → cyanosis → squat down → slightly kinks the femoral arteries in the legs → increases vascular resistance in the peripheral arteries → increases pressure in the systemic circulation → increases pressure in the LV → pressure on the left side > the right side → shunt temporarily reverses → reduces cyanosis. - During a serious hypercyanotic episode or tet spell, they can be treated by:  Keeping them calm. Giving them O2, IV fluids, and medications improves pulmonary blood flow. - Diagnosis: echocardiogram (prenatally). - Treatment: Cardiac repair surgery in the first year of life by: Closing VDS with a patch. Enlarging right ventricular outflow tract. Left-to-right Shunts - A left-to-right shunt allows the oxygenated blood to return directly to the lungs rather than being pumped to the body → late cyanosis. Ventricular Septal Defect - A ventricular septal defect is when the ventricular septum has a gap in it after development. - The septum is formed during development from a muscular septum of tissue growing upward from the apex and then fusing with a membranous septum (usually affected) growing downward from the endocardial cushions → separates the ventricles. - If these structures don’t fuse, a gap is left between the ventricles → VSD. - Deoxygenated blood → RA → RV → pulmonary artery (low P) OR → LV (high P) - Oxygenated blood → LA → LV → aorta (high P) OR → RV (low P) - Oxygenated blood prefers to flow to the lower pressure RV → increased O2 saturation in the RV and pulmonary artery → pulmonary hypertension. - VSDs is the most common congenital defect ~50 to 70% among babies, but 30-50% of VSDs close during childhood, which makes VSDs less common with adults.  - It is associated with fetal alcohol syndrome, Down syndrome, and other cardiac deformities as well. - VSD can be heard as a holosystolic murmur at the lower left sternal border. - Small VSD may be asymptomatic. - As the size of the VSD increases, the symptoms get more severe and earlier. - Treatment: surgical closure of the VSD. Atrial Septal Defect - The most common type of ASD is a secundum ASD. - A secundum atrial defect is when the septum secundum has a gap in it after development. - After birth, if the patent foramen ovale does not close, a gap is left between the atria → ASD. - This opening allows blood to move between the atria: Increases blood flow to the lungs. Leads to heart enlargement. Damages the blood vessels in the lungs. Leads to abnormal heart rhythm due to injury to the heart muscle. - Most children are asymptomatic but those with a large ASD can have slow growth and rarely a congestive heart failure. - Treatments: Medications for symptoms. Closure by: Cardiac catheterization – A catheter is inserted through a small incision in the groin to the heart. An atrial septal occluder is placed across the defect to plug the hole and prevent blood from crossing between the atria. Surgery – An incision is made in the chest to close the hole with a patch. Patent Ductus Arteriosus  - In the fetal period, shunt is right-to-left (normal). - In neonatal period, ↓ pulmonary vascular resistance → shunt becomes left-to-right → RVH, LVH and HF. - Patency is maintained by prostaglandin E and low O2 tension. - Uncorrected PDA → late cyanosis in the lower extremities (differential cyanosis). Eisenmenger Syndrome - Uncorrected left-to-right shunt (VSD, ASD, PDA) → pressure increases to a point where the pressure on the right side > the left side → direction of blood flow through the VSD switches from being left-to-right to right-to-left → Eisenmenger syndrome. - Causes late cyanosis, clubbing, and polycythemia. - Age of onset varies depending on size and severity of initial left-to-right shunt.