Blood Vessels Artery & vein cross section Vascular system within the liver

Blood Vessels Artery & vein cross section Vascular system within the liver www.phwiki.com

Blood Vessels Artery & vein cross section Vascular system within the liver

Norman, Royal, Meteorologist has reference to this Academic Journal, PHwiki organized this Journal Blood Vessels Human Anatomy Chapter 19 The blood vessels of the body as long as m a closed circulatory system. Blood is pumped from the heart to the body in addition to returned to the heart. Blood vessels have the ability to constrict or dilate in addition to increase or decrease pressure. Blood vessels may divide in addition to grow as the body requires. Arteries carry blood away from the heart in addition to veins bring blood towards the heart. I. Structure of blood vessels walls Blood vessels have three layers or tunics in a circular fashion that create a cavity called the lumen: a. Tunica Intima- contains endothelium (simple squamous epithelium). In vessels with a small diameter the endothelium is surrounded by a thin layer of loose connective tissue called subendothelial layer. b. Tunica Media- this layer is the thickest layer composed of smooth muscle arranged in circular sheets in addition to connective tissue. The sympathetic NS controls the smooth muscle activity. Vasoconstriction occurs when the smooth muscle contracts, this decreases the flow of blood. Vasodilation occurs when the smooth muscle relaxes, increases the diameter in addition to thus the blood flow.

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c. Tunica externa- Outer most layer, composed of connective tissue. It is designed to protect, stretches in addition to anchors the blood vessels. d. Lumen- cavity in the middle of the blood vessel that is filled with blood. The diameter of the lumen changes with vasoconstriction or vasodilation. It can also be influenced by plaque build up. Artery & vein cross section Artery Wall- notice thick muscular layer.

Vein Wall Capillary walls II. Types of blood vessels All three vessel types are found in systemic in addition to pulmonary circulation. A. arteries- The closer the artery is to the heart the larger its diameter in addition to the thicker its walls. As the artery branches it becomes smaller in diameter in addition to thinner until it becomes a capillary. Because arteries have a thick muscle layer they have the ability to change blood pressure. 1. Elastic arteries- (2.5-1 cm) largest, closer to the heart, have thick sheets of elastin in the tunica media, also called conducting arteries, able to withst in addition to large fluctuations in blood pressure. 2. Muscular arteries- (1cm-0.33 mm) distal to elastic arteries, they reach the organs, their tunica media is thicker in diameter than the lumen. Also the tunica media is lined with layer of connective tissue of both sides (internal elastic lamina in addition to external elastic lamina). The muscular layer constricts the vessel as needed by each individual organ. 3. Arterioles- (0.3mm-10 mm) They have the smallest diameter, the tunicas are considerably thinner but are still innervated to induce vasoconstriction or vasodilation. They connect to capillaries. Cross-section of elastic artery

B. Capillaries- these are the smallest blood vessels (8-10mm) as long as cing RBC to pass by in one after the other in line. They are thin enough to allow as long as chemical exchange, only composed of a single layer or endothelial cells lined by basal lamina. This is also the site through which WBC exit the blood stream. 1. Capillary beds- this is a network or capillaries that is connected to a terminal arteriole in addition to postcapillary venule. The terminal arteriole branches into the metarteriole (intermediate between arteriole in addition to true capillary) that further branches into the capillary bed. Throughout the metarteriole there are precapillary sphincters (smooth muscle) that control the flow of blood into the true capillaries. The capillaries connect into the thoroughfare channel (intermediate between capillaries in addition to venule) that connects the venule. 2. Capillary permeability- small molecules enter in addition to leave the capillaries through intercellular clefts. To increase permeability capillaries containing pores, called fenestrated capillaries, are located in areas of high exchange. All other capillaries are called continuous, there are no pores. Permeability happens in different as long as ms: a. direct diffusion- as with oxygen in addition to carbon dioxide b. intercellular cleft- as with WBC, most common c. cytoplasmic vesicles (caveolae)- as when large molecules like proteins in addition to carbohydrates are transferred from the intestine into the blood. d. fenestrations- in areas of large exchange as when water exits blood to make synovial fluid within the synovial joints. The capillaries that have the lowest permeability are those of the blood brain barrier. They are only permeable to lipid soluble substances in addition to components such as oxygen in addition to carbon dioxide.

Continous Capillary Fenestrated Capillary Sinusoidal Capillary 3. Sinusoids- wide leaky fenestrated capillaries in areas of extensive change in addition to crossing or large materials. These may be sites in which cells move into the blood like it happens in bone marrow in addition to spleen.

C. Veins-blood vessels that carry blood from the capillaries to the heart. As they move away from the capillaries thay increase in diameter. The blood pressure in veins is less than in arteries in addition to their walls are also thinner than arteries. 1. Venules- (8-100 mm) they are the smallest in addition to thinnest, specially as they are closer to the capillaries. As they approach the veins they become thicker. 2. Veins- lumens vary in size but compared to arteries they are larger. Their tunica externa is thicker than tunica media. The largest veins are the vena cavae the tunica externa also has b in addition to s of smooth muscle. 3. Vein valves- these assist in the transport of blood back to the heart. They prevent back flow. Similar to the valves of the heart, these valve have cusps as long as med by the endothelial cells of the tunica intima. In areas of the body that blood flow is directly against gravity there are more valves. There are no valves in veins of the thoracic in addition to abdominal cavities. 4. Returning blood to the heart- normal body movements produce muscle contractions that bring blood back to the heart. Skeletal muscle contractions as long as ce the valves to open in addition to propel blood towards the heart. D. Vascular Anastomoses- areas where several blood vessels unite or interconnect, they may be arteries or veins. Anastomoses may provide alternative routes as long as blood flow. They occur around organs like the heart, brain, or abdominal organs or around joints. Blood flow blockage of areas where there are no arterial anastomoses may result in severe tissue damage. E. Vasa vasorum- tiny arteries, capillaries, in addition to veins in larger blood vessels to provide their own blood supply in addition to nourishment as long as the outer half of the wall layers. These tiny blood vessels may arise from the same blood vessels it nourishes or those near by. Part 2: Blood vessels of the body- Focus on knowing the names of the blood vessel given to you in the practicum list. Also study the diagrams through out the book so you can visualize the pattern the blood vessels take throughout the body.

I. The pulmonary circulation- blood vessels that travel from the heart to the lungs, within the lungs, in addition to back to the heart. Includes all types of vessels. Arteries carry deoxygenated blood in addition to veins carry oxygenated blood. II. The systemic circulation-blood vessels that travel from the heart throughout the body in addition to back to the heart. Arteries carry oxygenated blood in addition to veins carry deoxygenated blood. A. Systemic arteries 1. aorta 2. arteries of the head in addition to neck 3. arteries of the upper limbs 4. arteries of the thorax 5. arteries of the abdomen 6. arteries of the pelvis in addition to lower limbs B. Systemic veins 1. venae cavae in addition to their major tribuatires 2-6 same as those as long as arteries 7. Portal-systemic anastomoses

Blood Vessels entering or leaving the heart

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View of iliac in addition to femoral arteries

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