Structure & Function of Blood Vessels - Lecture 5 Flashcards
What are the three main layers of a blood vessel wall?
○ Tunica intima
○ Tunica media
○ Tunica adventitia
Components of the tunica intima
○ Endothelium (simple squamous epithelium)
○ Basal lamina of the epithelial cells
○ Subendothelial connective tissue
Components of the tunica media
○ Smooth muscle fibres in loose connective tissue
○ May contain elastic fibres
Components of the tunica externa/adventia
○ Connective tissue
○ Merges with surrounding connective tissue
○ May contain vasa vasorum
Key differences between arteries and veins
○ Arteries: High pressure, thick walls, smaller lumen, maintain shape, more resilient, no valves
○ Veins: Low pressure, thin walls, larger lumen, may have valves to prevent backflow
what are the three types of arteries
○ Elastic (conducting) arteries
○ Muscular (distributing) arteries
○ Arterioles (resistance vessels)
Describe elastic (conducting) arteries
○ Examples: Aorta, brachiocephalic & common carotid
○ Up to 2.5cm
○ Function: Withstand pressure changes during the cardiac cycle and ensure continuous blood flow
○ Structural Adaptations: Thick tunica media with many elastic fibres and few smooth muscle cells
Describe muscular (distributing) arteries
○ Examples: Most named arteries, e.g., brachial & femoral
○ Diameter: 0.5mm - 0.4cm
○ Function: Distribute blood to muscles and organs, capable of vasodilation and vasoconstriction
○ Structural Adaptations: Smooth muscle cells +++ in tunica media, distinct internal and external elastic laminae, thick tunica externa
Describe arterioles (resistance vessels)
○ Capable of vasoconstriction & vasodilation
○ Control blood flow to organs
○ Involved in blood pressure control
○ Diameter: ≤ 30µm
○ Structural Adaptations: one to two layers of smooth muscle cells in tunica media, poorly defined tunica externa
What are capillaries and what is their function?
○ Connect arterioles and venules (microcirculation)
○ Site of gaseous exchange
○ Thin walls facilitate diffusion, blood flow is slow
○ Blood flow through capillaries is slow
○ 2- way exchange
○ 8µm in diameter
What are the three types of capillaries?
○ Continuous
○ Fenestrated
○ Sinusoidal
Describe continuous capillaries
○ Majority of capillaries are continuous
○ Found in skeletal and smooth muscle, connective tissue, and the lungs
Describe fenestrated capillaries
○ Contain pores in the endothelial lining, facilitating rapid exchange of water or large solutes
○ Found in the kidney, choroid plexus, and endocrine glands
Describe sinusoidal capillaries
○ Have spaces between endothelial cells, incomplete or absent basement membrane, allow for exchange of large solutes
○ Specialized lining cells (e.g. in the liver)
○ Blood moves slowly through sinusoid
What are metarterioles?
○ Supplies a single capillary bed
○ Continues as a thoroughfare channel
○ Constriction = reduced blood flow to whole capillary bed
