Vessel Structure Flashcards
What are the 3 classes of blood vessels?
- arteries
- capillaries
- veins
Arteries carry blood _______ the heart and become progressively __(size)___ as they_________.
- away from
- smaller
- branch and finally result in capillaries
Veins carry blood _______ the heart and become progressively ___(size)____ as they_________.
- towards
- larger
- merge and are closer to the heart
What are the layers in artery and vein walls called?
- tunics
Name the layers of tunic from inner to outer.
- tunica intima
- tunica media
- tunica externa
What is the endothelium?
simple squamous epithelium lining the blood vessel lumen
Describe the tunica intima.
composed of endothelium and a subendothelial layer of areola connective tissue
Describe the tunica media.
- comprised of circularly arranged smooth muscle
- sympathetic input causes this smooth muscle to contract resulting in vasoconstriction
- parasympathetic input results in vasodilation
Describe the tunica externa.
- connective tissue that help anchor the blood vessel to an organ
- vasa vasorum run through the tunica externa
What is the vasa vasorum?
small arteries that supply the larger arteries
Do arteries or veins have thicker walls?
arteries
What is the thickest tunic in arteries?
tunica media
What is the thickest tunic in veins?
tunica externa
Do arteries or veins have valves?
veins
Do arteries or veins have higher blood pressure?
arteries
Describe blood oxygen levels in arteries.
- systemic arteries transport blood high in O2
- pulmonary arteries transport blood low in O2
Describe blood oxygen levels in veins.
- systemic veins transport blood low in O2
- pulmonary veins transport blood high in O2
What are the 3 types of arteries?
- elastic arteries
- muscular arteries
- arterioles
Which type of arteries are the largest?
elastic arteries
Name some elastic arteries near the heart.
- aorta
- pulmonary artery
- brachiocephalic artery
- common carotid arteries
- subclavian arteries
What do the elastic fibres in elastic arteries allow for?
in all 3 tunics. Allow for stretching under increased pressure generated by blood ejected from the heart
Elastic arteries branch into ______ arteries.
muscular
Name the elastic fibres in muscular arteries.
- internal elastic lamina: separates tunica intima and tunica media
- external elastic lamina: separates tunica media and tunica externa
Which type of arteries are the smallest?
arterioles
Describe vasoconstriction in the arterioles.
sympathetic innervation to the muscle fibre cells of the tunica media causes vasoconstriction resulting in elevation of blood pressure
Describe vasodilation in the arterioles.
parasympathetic innervation to the muscle fibre cells of the tunica media causes vasodilation resulting in lowering of blood pressure
What is the only type of blood vessel where metabolic exchange can occur between blood and tissues?
capillaries
Describe capillaries
- smallest blood vessels
- diameter only slightly larger than an erythrocyte
- wall consists solely of the tunica intima (single layer of endothelial cells)
Each capillary bed is fed by a _______.
metarteriole
What are true capillaries?
branches from the metarteriole that begin with a ring of smooth muscle on their walls
What are the 3 types of capillaries?
- continuous
- fenestrated
- sinusoids
Describe continuous capillaries.
- most common
- endothelial cells
- continuous, complete lining aided by the presence of tight junctions
Describe fenestrated capillaries.
- contain pores called fenestrations
- allows fluid exchange between blood and interstitial fluid
Describe sinusoid capillaries.
- have large gaps between endothelial cells
- allows transport of large molecules and cells to and from the blood
- basement membrane is discontinuous or absent
The body’s veins hold about __% of the body’s blood.
- 60%
- veins function as blood reservoirs
What are the smallest veins?
venules
What are the smallest venules?
postcapillary venules
What occurs through the walls of postcapillary venules?
diapedesis: leukocyte travel to damage/infection
Venules merge to form ____.
veins
What are companion vessels with arterioles?
venules
Smaller and medium sized _____ travel with muscular arteries, while large ____ travel with elastic arteries.
veins
Why do valves exist in veins, and where are they formed from?
- blood pressure in veins is low, have valves to prevent pooling
- formed from the tunica intima
What 2 pumps assist with venous return (along with valves)?
- skeletal muscle pump
- respiratory pump
Describe the skeletal muscle pump.
- skeletal muscles contract
- the first valve closes
- the pressure build up causes the second valve to open
Describe the respiratory pump.
INHALATION
- increases blood flow into thoracic veins through decreased intrathoracic pressure, diaphragm contracting, increased intra-abdominal pressure
EXHALATION
- increases blood flow into heart and abdominal veins though increased intrathoracic pressure, diaphragm relaxing, decreased intra-abdominal pressure
