Blood vessels

• What are elastic fibres?

  Made of elastin. Can stretch and recoil, helping to maintain blood pressure.
• What’s smooth muscle?

  Contracts or relaxes to change the size of the lumen (constricts/dilates) and control blood flow.
• What’s collagen do?

  Provides structural support and strength to maintain the shape and volume of the vessels and prevent it from bursting
• What are the main types of blood vessels?

  Arteries- carry blood away from heart.

  Arterioles- carry blood from arteries into capillaries

  Capillaries- site of diffusion between blood and body tissues

  Venules- carry blood from capillaries into veins

  Veins- return blood to the heart
• Describe the structure and function of arteries

  Carry blood at high pressure from the heart to the rest of the body.

  Mostly oxygenated blood except for the pulmonary artery carrying deoxygenated blood to the lungs and umbilical artery when pregnant.

  Have thick walls to withstand high pressure.

  Contain high amounts of elastin fibres to stretch and recoil to ensure a more smooth, continuous flow of blood and to maintain high blood pressure.

  Smooth muscle enables the artery to vary blood flow through the size of the lumen by contracting and relaxing.

  Lined with smooth endothelium to reduce friction and ease flow of blood. Collagen provides strength to withstand pressure and prevent bursting.
• Difference between arteries and arterioles

  Arterioles branch off arteries and have more smooth muscle, larger lumen and less elastin in walls as they don’t need to withstand such high pressures and blood here flows at a more constant pressure with little pulse surge. Arteries have thick elastic layer to withstand high pressure.
• What does the smooth tissue in arteries allow?

  Them to expand or contract, controlling the amount of blood flowing to tissues
• Describe the order of blood vessels starting from the heart and going back to the heart

  Arteries branch into arterioles. These branch into capillaries where substances are exchanged. These connect to venules which join together to form veins. They take blood back to the heart.
• Describe the structure and function of a capillary

  Narrow lumen which slows the flow of blood so there’s more time for the exchange of materials between blood and body cells.

  Thin walls, which are one endothelial cell thick, to reduce diffusion distance for rapid exchange of materials.

  Numerous and highly branched providing a large SA to increase the rate of exchange and diffusion.

  Permeate tissues ensuring no cell is far from a capillary, reduces diffusion distance.
• Describe the structure and function of veins

  Carry blood away from cells of body to heart. Mostly deoxygenated blood except for pulmonary vein carrying oxygenated from lungs and umbilical vein carrying oxygenated blood from placenta to fetus. Thin walls (muscle and elastic layers) as they carry blood under low pressure. Valves to prevent backflow of blood. Large lumen to reduce resistance for blood flow and so flows more easily. Lots of collagen.
• What is the endothelium?

  The inner lining made up of endothelial cells
• Compare the structure of a vein and venule

  Venules are smaller in diameter and have thinner walls than veins. Both have values to prevent back flow of blood.
• What’s vasoconstriction?

  The narrowing of blood vessels like arteries and arterioles due to contraction of the smooth muscles in their walls, reducing blood flow.
• What’s vasodilation?

  The widening of those blood vessels due to relaxation of the smooth muscle in their walls, which increases blood flow.
• What adaptations allow the movement of deoxygenated blood to the heart, despite low pressure and movement against gravity?

  Veins have values to prevent back flow of blood. Contraction of skeletal muscles surrounding the veins when the body moves pushed blood towards the heart. Thin walls of veins allow them to easily compressed, aiding flow of blood. Breathing movements of chest act as a pump, pressure changes moving blood in veins of chest and abdomen to heart.