L7 Venous_System.pdf

Venous System By: Gan Quan Fu, Lecturer, FMHS  Content Relevance to Healthcare Professionals. Introduction & General Principles of Veins Comparison between arteries, capillaries and veins Types of venous circulation – Syst...

Venous System By: Gan Quan Fu, Lecturer, FMHS  Content Relevance to Healthcare Professionals. Introduction & General Principles of Veins Comparison between arteries, capillaries and veins Types of venous circulation – Systemic Circulation – Portal Circulation Q&A  Importance to Healthcare Professionals To understand the Mechanism of Disease involving the venous systems. To perform certain procedures (eg: IV injection). Communication.  General principles about Veins Veins – Vessels that carry blood towards the heart. – Carry deoxygenated blood (except pulmonary and umbilical veins) Pulmonary Veins – Carry oxygenated blood from the lungs (postnatal). Umbilical Veins – Carry oxygenated blood from placenta to fetus (prenatal). – Begin as venules, which unite into vessels of increasing size to form veins. – Arranged as superficial veins and deep veins draining the superficial and deep parts of the body respectively. – Have valves that allow one way blood flow. – Communicate with each other forming an extensive anastomosis Provides collateral return blood flow in case of venous obstruction. (Ensures alternative routes for blood circulation when there is blockage) Flow of blood depends on the peripheral muscular activity.  Deep and Superficial Veins Deep veins – Paired with arteries Superficial veins – Usually have names and unrelated to those of arteries There are very few superficial arteries.  Differences Between Artery Veins and Capillaries Adventitia Differences Between Arteries and Veins  Venous Circulation Systemic circulation: – Superior and inferior vena cava with their tributaries (branches that feed into them) (blood from heart to rest of body) Portal circulation: – Portal vein (circulation of nutrient-rich blood between the gut and liver-enables liver to remove harmful substance before blood enters systemic circulation) Independent circulation allows specialised functions to be performed effectively. Interconnected facilitates efficient Processing and regulation of substances absorbed from digestive tract before entering the broader systemic circulation SYSTEMIC VEINS VEINS OF VEINS OF VEINS OF VEINS OF AZYGOS VEINS HEAD & NECK UPPER LIMB ABDOMEN LOWER LIMB (Unpaired )  Systemic Veins (Venous Drainage) SVC (Superior Vena Cava) – drains all the blood from head & neck, thorax and upper limbs IVC ( Inferior Vena Cava) – drains blood from abdomen and lower limbs  Systemic Veins (Head & Neck) Two divisions: (paired veins) – Superficial Veins External Jugular veins (EJV) Anterior jugular veins (AJV) – Deep Veins Internal Jugular veins (IJV) Jugular-collarbone/throat/neck  External Jugular Vein Lies superficial to the sternomastoid muscle It passes down the neck Only tributary (branch) of the subclavian vein./only vein that flows into the subclavian vein Drains blood from: – Outside of the skull – Deep parts of the face  Anterior Jugular Vein Begins in the upper part of the neck by the union of the submental (area under the chin) veins. Descends close to the median line of the neck, medial to the sternomastoid muscle. At the lower part of the neck, it passes laterally beneath that muscle to drain into the external jugular vein. Just above the sternum the two anterior jugular veins communicate by a transverse vein to form the jugular arch.  Internal Jugular Vein Most important vein in the neck region Only drainage pathway for blood from brain – Drains blood from the head, brain, face & neck. Begins at the jugular foramen at base of skull as continuation of sigmoid (S shape) sinus (venous drainage system of the brain) Descends in the neck along with: – Internal and common carotid arteries and vagus nerve, within the carotid sheath. Ends by Joining with the subclavian vein to form the brachiocephalic vein.  Internal Jugular Vein (Tributaries) Superior thyroid Lingual Facial Occipital veins Dural venous sinuses (Found between dura matter) Veins of Head and Neck Summary  Systemic Veins (Upper Limbs) Two divisions: – Superficial Veins Basilic Cephalic – Deep Veins  Superficial Veins (Upper Limbs) Cephalic vein – Ascends in the superficial fascia on the lateral side of the biceps. – Drains into the Axillary vein and becomes subclavian vein Basilic vein – Ascends in the superficial fascia on the medial side of the biceps. – Halfway up the arm, it pierces the deep fascia. – At the lower border of the teres major it joins the venae comitantes of the brachial artery (or just say joins brachial veins) to form the Axillary vein. VC-accompanying veins (veins that run parallel to arteries)  Deep Veins (Upper Limb) Venae commitantes – Accompany all the large arteries, usually in pairs. Brachial Vein Ulnar Vein Radial Vein Axillary vein – Formed by the union of basilic vein and the venae comitantes of the brachial artery. This term is used instead of saying brachial vein to avoid confusion that there is only 1 brachial vein. There are multiple veins running alongside the brachial artery Veins of Upper Limb Summary  Systemic Veins (Azygos) Runs up the side of the thoracic vertebral column draining itself towards the superior vena cava Formed by the union of the ascending lumbar veins with the right subcostal veins at the level of the 12th thoracic vertebra. Ascend in the posterior mediastinum, and arching over the right main bronchus posteriorly at the root (hilum) of the right lung to join the superior vena cava. Systemic Veins (Azygos)  Veins of Abdomen Drains most of the blood from the body below the diaphragm into the right atrium. Formed by the union of the 2 common iliac veins behind the right common iliac artery at the level of the 5th lumbar vertebra. Ascends on the right side of the aorta Pierces the central tendon of diaphragm at the level of the 8th thoracic vertebra. The abdominal aorta is primary arterial counterpart to the inferior vena cava  Tributaries of Inferior Vena Cava Two common iliac veins Median sacral vein Four paired lumbar veins Right gonadal vein (*left gonadal vein drains into the left renal vein) Paired renal veins Right suprarenal vein (*left suprarenal vein drains into the left renal vein) Hepatic veins Paired inferior phrenic vein  Systemic Veins (Lower Limb) Two divisions: – Superficial Veins Great Saphenous Vein Small Saphenous Vein – Deep Veins  Great Saphenous Vein Longest vein Begins from the medial end of the dorsal venous arch of the foot. Passes upward in front of the medial malleolus with the saphenous nerve. Ascends in accompany with the saphenous nerve in the superficial fascia over the medial side of the leg. Ascends obliquely upwards, and lies behind the medial border of the patella. Passes behind the knee and curves forward around the medial side of the thigh. Hooks through the lower part of the saphenous opening in the deep fascia to joins the femoral vein about 1.5 in. (4 cm) below and lateral to the pubic tubercle.  Great Saphenous Vein Connected to the small saphenous vein by one or two branches that pass behind the knee. Numerous perforating veins connect the great saphenous vein with the deep veins. – Perforating veins have valves which allow blood flow from superficial to deep veins. Saphenous veins in venous grafting and saphenous cut down (take care of the saphenous nerve)  Small Saphenous Vein Arises from the lateral end of the dorsal venous arch. Ascends behind the lateral malleolus in company with the sural (calf) nerve. Follows the lateral border of the tendocalcaneus and then runs up to the middle of the back of the leg. Pierces the deep fascia in the lower part of the popliteal fossa. Drains into the popliteal vein Has numerous valves along its course. Anastomosis freely with great saphenous vein.  Deep Veins of Lower Limb Comprise the venae comitantes. – Accompany all the large arteries – Usually in pairs. – Unite to form the popliteal vein, which continues as the femoral vein. Receive blood from superficial veins through perforating veins. These veins are: – Femoral Vein – Popliteal vein – Peroneal vein – Anterior tibial vein – Posterior tibial vein  Applications (Venous Return from Lower Limb Mechanism) Much of the saphenous blood passes from superficial to deep veins through the perforating veins Blood is pumped upwards in the deep veins by the contraction of the calf muscles (calf pump). – Action of ‘calf pump’ is assisted by the tight sleeve of deep fascia surrounding these muscles. Varicose (twisted) veins: (swollen, enlarged, twisted) – Valves in the perforating veins become incompetent, blood flow backwards and pool in veins – Direction of blood flow is reversed and the veins become varicosed. – Most common in posterior & medial parts of the lower limb, particularly in old people.  Portal Venous System Drains blood from the gastrointestinal tract and spleen. Formed by the union of the superior mesenteric and splenic veins. Immediately before reaching the liver, the portal vein divides into right and left that enter the liver. Tributaries: – Gastric – Cystic veins (relating to gallbladder) Portal Circulation  Portocaval (portal vein + vena cava) Anastomosis Also known as portal systemic anastomosis Specific type of anastomosis that occurs between the veins of portal circulation and those of systemic circulation. Anastomotic channels become dilated (varicosed) in case of portal hypertension.  Portocaval Anastomosis (Sites) Lower end of esophagus: – Esophageal Vein – Azygos vein Lower part of rectum: (Hemorrhoids) – Superior and middle rectal veins – Inferior rectal vein Para umbilical region: (Caput Medusae) – Para umbilical veins – Superficial epigastric vein Retroperitoneal: – Veins draining colon – Veins of the posterior abdominal wall Patent ductus venosus: – Left branch of portal vein – Inferior vena cava.  Portocaval Anastomosis Summary Region Name of clinical condition Portal circulation Systemic circulation Esophageal branch of left Esophageal branches Esophageal Esophageal varices gastric vein of Azygos vein Middle rectal Rectal Rectal Varices Superior rectal vein veins and inferior rectal veins Paraumbilical Caput medusae Paraumbilical veins Superficial epigastric vein Renal vein, suprarenal Splenorenal Shunt Splenic vein vein, paravertebral vein, Retroperitoneal and gonadal vein Right colic vein, middle colic Retroperitoneal veins of (no clinical name) vein, left colic vein Retzius Hepatic pseudolesions Perihepatic veins of Sappey Superior epigastric vein Intrahepatic Patent ductus venosus Left branch of portal vein Inferior vena cava  Assignments & Self Directed Learning Take out a piece of paper, try drawing a schematic diagram of the venous system. Discuss it with your peers. (Reference: Saladin, 8th edn. Page 767,772, 776, 781, 782, 787, 791 gives good schematic diagrams about the venous system.) Thank You