Blood Vessels

• What are the main types of blood vessels in the body?

  Arteries, arterioles, veins, venules, capillaries
• What is the primary function of arteries?

  Transport blood away from the heart
• How do arterioles function in the circulatory system?

  They transport blood into capillaries
• What is the role of veins in the circulatory system?

  Transport blood to the heart
• What do venules do in the circulatory system?

  Transport blood from capillaries to veins
• What is the lumen of a blood vessel?

  The hollow interior through which blood flows
• How does the size of the lumen vary among blood vessels?

  Arteries have narrow lumens, veins have wider ones
• What is the composition of the tunica intima?

  Endothelial layer, connective tissue, elastic fibres
• How thick is the endothelium in blood vessels?

  One cell thick
• What is the function of the endothelium in blood vessels?

  Reduces friction for free blood flow
• What is the structure of the tunica media in arteries?

  Made up of smooth muscle cells and elastic tissue
• Why do arteries have a thick layer of elastic & muscle tissue?

  To withstand high pressure and enable contraction
• How does elastic tissue function in arteries?

  Maintains blood pressure by stretching and recoiling
• What is the tunica adventitia made of?

  Mostly collagen
• What is the function of collagen in blood vessels?

  Protects vessels from damage by over-stretching
• Why do arteries have a narrow lumen?

  To maintain high blood pressure
• What is a pulse?

  A rhythmic expansion in arteries
• What allows arterioles to regulate blood flow?

  A muscular layer that can contract
• How do arterioles respond during exercise?

  Reduce blood flow to stomach and intestines
• How do arterioles differ from arteries?

  Lower proportion of elastic fibres, more muscle cells
• What is the primary function of veins?

  Return blood to the heart
• Why do veins have thinner layer of muscle & elastic tissue?

  No need for thick layer due to low pressure
• How does the lumen of veins compare to arteries?

  Veins have a much larger lumen
• What is the effect of a larger lumen in veins?

  Ensures adequate speed of blood return
• How does a larger lumen affect friction in veins?

  Reduces friction between blood and endothelium
• What is the relationship between blood flow rate and lumen size in veins?

  Slower flow but equal volume delivered
• What is the function of valves in veins?

  Prevent backflow of blood
• What do venules connect?

  Connect capillaries to veins
• What is the structure of venules?

  Few or no elastic fibres and large lumen
• Why do venules not require a muscular layer?

  Blood is at low pressure after capillaries
• What are capillaries?

  Thin-walled blood vessels in the circulatory system
• What is the primary function of capillaries?

  Allow substances to leave blood to tissues
• What are capillary beds?

  Networks of capillaries for substance exchange
• How does the small diameter of capillaries affect blood flow?

  Forces blood to travel slowly for diffusion
• Why is a large number of capillaries beneficial?

  Short diffusion distance between blood and cells
• How does the thickness of capillary walls affect diffusion?

  Reduces diffusion distance for gases
• What is the wall structure of capillaries?

  Made solely from a single layer of endothelial cells
• What are pores in capillary walls?

  Gaps allowing blood plasma to leak out
• What do arteries have on their exterior?

  Collagen to provide the artery with strength & stop bursting