Blood Vessels Flashcards
Blood Flow Circuit
Flows away from the heart through the arteries, back to the heart through the veins
Smaller blood vessels called capillaries form junctions between arteries and veins
Capillaries
Connection vessels between aerial and venous systems
Aka exchange vessels
Transfers nutrients & gases to organs, tissues & cells
Picks up and transfers waste products from organs, tissues & cells
Blood Flow (vessels in size order)
Arteries -> Veins -> Arterioles -> Venules -> Capillaries
Three Layers of Arteries & Veins
Tuncia Intima
Tunica Media
Tunica Externa
*All vessels are lined with endothelial cells
Tunica Intima
Innermost layer
Simple, squamous endothelial cells
Internal plastic membrane (arteries)
Tunica Media
Smooth muscle (for vasocontriction & vasodilation) Thickness of muscles depends on size-diameter of vessel & blood pressure
Tunica Externa (adventitia)
Outermost layer
Contains collagen (thicker in veins)
Blends/sticks to adjacent tissues - stabilises and holds vessels in place
Elastic vs. Muscular Arteries
Elastic - stretches & recoils when pressure changes
Muscular - distributes blood, thicker tunica media will alter luminal size
Arterioles
Tunica externa is minimal/absent
Smooth muscle cells which change diameter
Capillaries
Exchange vessels
Thin walls for quick diffusion
3 types:
- Continuous
- Fenestrated (small pores for filtration/absorption)
- Sinusoidal (big gaps for fluid/nutrients to leak out)
Venules
Collect blood draining from capillary beds
Little/no tunica media
Arterial System
High pressure
Blood pressure in medium/large veins is low so it doesn’t overcome gravity
Veins contain valves
Multi-directional blood flow
Venous System
Contains almost 2/3 of the body’s blood volume
Veins more stretchy and act as reservoirs to accomodate for changes in blood volume
Lymphatic System
Carry lymph from peripheral tissues to venous system
Absorption rather than secretion/diffusion
Lymphatic capillaries are closed vessels (rather than blood vessels which are connected and make up a circuit)
Right lymphatic duct - delivers to the top right side of body, above the diaphragm
Thoracic duct - delivers to the rest of the body, inferior to the diaphragm, on the right side
