Question | Answer |
What is included in the tunica interna (intima)? | Endothelium and connective tissue. |
What is included in the tunica media? | Muscle and connective tissue. |
What is included in the tunica externa (adventitia)? | Thick layer of connective tissue. |
What lines the tunica interna? | Lined by specialized simple squamous epithelium called the endothelium. |
What does endothelium release and what does it do? | Releases endothelins that constrict the smooth muscle within the walls of the vessel to increase blood pressure. |
What is the function of the basal lamina? | Effectively binds the endothelium to the connective tissue. |
What do large arteries also have? | A distinct layer of elastic fibres known as the internal elastic membrane at the boundary with the tunica media. |
What is the function of the internal elastic membrane in larger arteries? | It provides the structure while allowing the vessel to stretch. |
How does the tunica media in veins compare to in arteries? | It is the thickest layer in arteries and it is much thicker in arteries than it is veins. |
What is the tunica media composed of? | Concentric layers of helically arranged smooth muscle cells. |
What is the function of elastic fibres in the tunica media? | To support the muscle cells. |
What is vasoconstriction? | Contraction of the circular muscles in the tunica media. |
What is vasodilation? | Relaxation of the circular muscles in the tunica media. |
What is the tunica externa? | A sheath of longitudinally orientated connective tissue composed primarily of collagen (type 1) fibres. |
How does the tunica externa in veins compare to in arteries? | This is normally the thickest in veins and may be thicker than the tunica media of some larger arteries. |
What are the large arteries mainly composed of? | Elastic tissue. |
How do the large arteries maintain blood pressure? | They expand during systole, while elastic recoil during diastole helps drive blood onwards. |
What is the structure of muscular arteries? | Have a relatively thick layer of circular smooth muscle in their tunica media. |
What is the function of muscular arteries? | Control distribution of blood to regions and organs. |
How do muscular arteries carry out their function? | They regulate blood flow by constriction or relaxation of their walls. |
How do muscular arteries prevent a haemorrhage? | By contracting. |
Can muscular arteries accommodate an increase in diameter? | Yes. |
What are the arteries from the top of the arm to the bottom? | Subclavian, Axillary, Brachial and then Radial and Ulnar. |
Where do the radial and ulnar arteries lead to in the hand? | In the hand, the deep and superficial palmar arches are derived from both the radial and ulnar arteries. |
What does arterial anastomosis ensure? | Ensures supply to the hand and fingers in any position of the upper limb. |
What is an anastomoses? | A communication between two blood vessels without an intervening capillary network. |
What are the three descending large arteries of the trunk? | Descending thoracic aorta, abdominal aorta and common iliac artery. |
Where does the femoral artery lie? | In the groin, the femoral artery lies with its vein medially, and the femoral nerve laterally. |
When are the relations between the different vessels in the groin important? | When taking blood or inserting arterial cannulae. |
What are the descending lower limb arteries above the knee? | (Aorta), common iliac, internal iliac, external iliac, (common) femoral, profunda femoris, (superficial) femoral and popliteal. |
What are the descending lower limb arteries below the knee? | Popliteal, anterior tibial, tibio-peroneal trunk, peroneal and posterior tibial. |
Why is smooth muscle present in the media of all arteries? | The elements of control over distribution and flow remain crucial. |
What defines an arteriole? | Arteries less than 0.5mm in diameter. |
What is the structure of a metarteriole? | Same diameter as capillaries, but with one layer of smooth muscle cells in their walls. |
What is the structure of capillaries? | Tube of endothelium only supported by basal lamina. No smooth muscle on their walls. |
What is the function of capillaries? | Allow exchange of oxygen, carbon dioxide, nutrients and hormones between cells/interstitial fluid and blood. |
How do capillaries allow exchange? | The basal lamina splits to enclose pericytes. |
What regulates blood flow through the capillary? | The pre-capillary sphincter. |
How are veins usually classified? | According to size; the smallest are venules. |
What is the structure of venules? | The media is thin, with only a few smooth muscle fibres. |
What do venules allow the passage of? | Leukocytes can pass through the walls of venules (diapedesis) and escape into surrounding connective tissue. |
What is the structure of the valves in the venules? | Two valve leaflets can be seen in the lumen arising from the intima and covered by endothelium. |
How do the valves in the venules work? | When the blood pressure proximal to the leaflets is greater than that distal to them they close, preventing backflow. |
What are venae comitantes? | A vein that is paired with the sides of an artery. The pulsation of the artery therefore aids venous return to the heart. |
How does a thrombus form? | Plaques of atheroma may form within arteries and lead to the formation of thrombus (blood clot) and vascular occlusion. |
What are deep veins? | Accompany the limb arteries, which are situated deeply and have the same names as the arteries. |
What are superficial veins? | Lie immediately under the skin. |
What are the superficial veins in the lower limbs? | The Great (Long) Saphenous Vein and the Small (Short) Saphenous Vein. |
What is the function of perforating veins? | To connect deep and superficial veins. |
What is the direction of blood flow in veins? | Venous flow is from superficial to deep veins, due to valves in perforating veins. |
What causes varicose veins? | Incompetency of the valves. |
What factors help venous return to the heart against gravity? | The valves inside the veins, contraction of muscles, arterial pulsation and negative intrathoracic pressure. |
What are superficial veins in the upper limbs used for? | Phlebotomy. |
Define phlebotomy. | The surgical opening or puncture of a vein in order to remove blood or to infuse fluids. |
Which veins in the upper limb can be used for phlebotomy? | The cephalic, the basilic and median cubital veins. |
Why must care be taken when performing phlebotomy in the upper arm? | Not to puncture the brachial artery or median nerve posteriorly. |
What is the function of the vena cava? | Drains the venous blood of the head, neck and upper limbs to the right atrium. |
What does the azygos vein do? | Drains the venous blood of the thoracic wall to the superior vena cava. |
What are the thoracic veins? | Superior vena cava, azygous vein and inferior vena cava. |
Where does venous blood from the GI tract and the spleen go? | Into the (Hepatic) Portal Vein, which takes the venous blood through the liver before it joins the inferior vena cava. |
What is the vasa vasorum? | The network of small blood vessels that supply the walls of large blood vessels, such as elastic arteries. |
What is the lymphatic system part of? | The immune system of the body. |
What is the lymphatic system formed of? | Lymph vessels, lymph nodes, tonsils, thymus, spleen and intestinal wall. |
What is the function of the lymphatic system? | Helps veins to remove the interstitial fluid, which is then called lymph. |
How is lymph formed? | Interstitial fluid is absorbed by lymph capillaries. |
What is the structure of lymph capillaries? | Thin-walled, endothelial tubes. |
What type of lymph vessels are associated with veins? | Superficial lymph nodes. |
What type of lymph vessels are related to arteries? | Deep lymph nodes. |
What does drainage in the lymphatic system depend on? | Drainage depends upon adjacent muscle activity and valves prevent backflow. |
What disease can spread in the lymph nodes? | Tumour may well spread in the lymphatics and seed in the nodes. |
What is the position of the inguinal lymph node? | Superficial, inferior to the inguinal ligament and alongside the great saphenous vein in the groin. |
What is the position of the deep inguinal lymph node? | Alongside the femoral vein. |
What drains into the inguinal lymph nodes? | Lower limb and buttock; external genitalia; lower back and abdominal wall below umbilicus. |
Where does the superficial inguinal node drain into? | Into the deep inguinal nodes. |
What is the position of the axillary lymph nodes? | Grouped in the axilla related to the axillary vein and artery; lateral to, deep to or medial to pectoralis. |
What drains into the axillary lymph nodes? | Upper limb, anterior and posterior thoracic walls, plus upper abdominal wall above umbilicus (breast). |
What is the position of the cervical lymph nodes? | Superficial: under jaw; over parotid; behind ear; occipital. Deep: alongside internal jugular vein (jugulo-digastric; jugulo-omohyoid). |
What drains into the cervical lymph nodes? | The head and neck structures. |
Which lymph nodes communicate with axillary and thoracic nodes? | Inferior deep cervical nodes. |
Where does all lymph drain into? | Drained by lymph vessels that eventually return to the lymph to the venous system. |
What is the largest lymph vessel? | The Thoracic Duct. |
What is the position of the thoracic duct? | Opens at the junction of the left subclavian and internal jugular veins. |