Major Veins Reference Materials

Major veins ● ● ● Drainage pattern goes from superficial to deep (major large veins) Heart is the last destination for venous flow Very numerous to prevent blood pooling ○ Needs multiple pathways in case a vein is kinked (due to joint movement), there are alternate ways to bring blood back to the heart * tick off the ones that you recognise ➔ Superficial veins do not have a matching artery (because they are close to the surface of the skin) Superior vena cava ● Enters through right side of the heart ● All veins from the head, neck, upper limbs will drain in the superior vena cava before it goes to the heart Inferior vena cava ● Enters through the right side of the heart ● Veins from the lower limbs, pelvic organs and abdominal organs will drain in the inferior vena cava before it goes to the heart Superficial veins ● Closer to the surface of the skin, so they don’t have a matching artery covered in sheath ● Superficial veins start at the dorsal surface for both the upper and lower limbs ○ Thumb is on the lateral side but big toe is on the medial side Superficial veins of the upper limbs ● Cephalic vein ○ Thumbs up, it follows the arch from the wrist all the way down the arm and to the head ● Basilic vein ○ Runs on the little finger side ○ Medial part of the arm to the axillary vein ○ Basilic remember 'base' ● Median cubital vein ○ Crease of elbow on anterior surface ○ Communicates between the cephalic and basilic vein ○ If there's pressure on the cephalic or basilic (due to joint movement)= alternate pathway Superficial veins of the lower limbs ➔ Be careful with what’s superficial and deep → the popliteal vein goes to the femoral vein (not the great saphenous vein), which is deep ● Great saphenous vein ○ Originates from the middle part of the dorsum of the foot ○ Goes up the leg through this vein until it reaches the femoral vein (superficial until it joins the top of the thigh and then it can become part of the venous system again ● Small saphenous vein ○ Comes of the lateral side of the dorsum of the foot ○ Only goes to the back of the knee ○ Drains into the popliteal vein Mechanisms of venous return ● Needs valves and pumps to drive blood back to the heart (needs to go against gravity) ● There is also less tunica media (less muscle and power to bring it back) ● Valves → veins are segmented so it helps to continue the path of blood back to the heart (only drops to that segment and doesn’t go all the way back down) ● Major pumps: ○ Thoracic pump ○ Muscular pump ○ Arterial pump Thoracic pump ● Bring blood to the thoracic cavity and directly to the heart ● There are no valves close to the heart ● Inhaling changes the pressure (creates a negative pressure) and draws blood up into the last major veins and then into the heart (like a straw) Muscular pump 1. Muscle contracts and squeezes onto the vein 2. Draws up blood through the valve and into the next section of the vein 3. Muscle relaxes and the valves close ● Blood goes back downwards (but the ones already in the valve can't go down anymore) 4. Another muscle squeezes and this process continues as the blood goes up Arterial pump ● When blood is going away from the heart, it goes through a pulse wave (like a blood bubble) ● Increases the size of the blood vessel (vasodilation) and increases blood volume in that area ● At the point where the blood bubble passes through, it pushes up against the wall of the vein next to it, opening the valve ○ Squeezes the wall of the vein and the blood is driven back to the heart ○ Artery bubble squeezes the tube of the vein (like the muscular pump) to drive the blood back to the heart ○ Needs the neighbouring structures to move the blood through the vessel Classify blood as a tissue ● Blood = specialised connective tissue ● Why is it a connective tissue? ○ Has an ECM ○ Connects all of the body systems together - continuous tubular structure through bringing blood and oxygen around the body ○ Originates from the mesoderm ● ECM is more fluid (fluid part is known as plasma) → like the ground substance ● Has no protein fibres ● Has its own protein fibre derivative → RBC erythrocytes, WBC leukocytes and platelets (to enable blood clotting) Term Definition Tributaries Vein that empties into another vein Tunics Layers of the blood vessel walls Plasma Fluid ECM of blood Vena cava Large, hollow veins that feed directly into the heart Great Larger or higher Lesser Smaller or lower