deck_16298212 Flashcards
Blood vessel functions (2)
- deliver blood to organs/tissues
- maintain homeostasis - vasoconstriction/vasodilation
Efferent vessels carry where?
away from heart
Afferent vessels carry where?
Towards the heart
Why high blood pressure refers to arterial system?
Less pressure in veins/capillaries
Arteries are which kind of vessel?
efferent
Arteries bring blood to where?
Arterioles
Arterioles regulate flow into where?
Capillary beds
What happens at capillary sites?
Exchange of gases and nutrients b/w blood and tissue
Capillaries are composed of what?
Endothelial cells
Arteries are composed by?
Thick elastic walls
What are arterioles? are they more or less elastic?
Small arteries
Less elastic
Venules and veins are which kind of vessel?
Afferent
What do veins and venules regulate?
Cardiac filling (return to heart)
name blood vessel wall layers innermost to outermost
Tunica Intima
Tunica Media
Tunica Externa
Name 3 components of the Tunica Intima
Endothelium
Basement membrane
Internal elastic lamina
What is the Tunica Media composed of?
Smooth muscle and elastic fibres
What does the external elastic lamina seperate?
Separates Tunica Externa from Tunica Media
Tunica Media can do what?
- Limit pressure and blood flow - by contract/dilate
- Help limit blood loss w/ injury
What is Tunica Externa composed of?
Elastin & collagen fibres. nerves, blood vessels
Vasa vasorum located in Tunica Externa, does what?
small vessels that supply blood to blood vessels
Main difference between composition of Arteries and Veins
Arteries: Thicker walls
Veins: Thicker lumen
How does blood move in arteries and veins
- Arteries: Pressure from heart
- Veins: Valves & skeletal muscle contractions
How thick are the walls of Capillaries, which have the thinnest walls?
One cell layer thick
Arteries have high compliance which means?
more ability to stretch, due to elastic fibres
What innervates smooth muscle, allowing for vasoconstriction and vasodilation
Autonomic nervous system - sympathetics decrease or increase diameter
Main differences between Elastic and Muscular arteries?
Elastic: Bigger, conduct blood away from heart
Muscular: Smaller, distribute blood to other organs
Main function of Elastic Arteries?
Stretch and squeeze back to conduct blood during Ventricle Systole
Structure of Muscular Arteries?
Less elastic, more muscles
Main function of Muscular Arteries?
- Distribute blood to organs
- Greater vasoconstriction and vasodilation for blood flow
Size of Arterioles
not much bigger than capillaries
Arterioles also have what in the Tunica Externa?
Sympathetic nerves
Main function of Arterioles?
Regulate flow of blood into capillary networks
Order of movement from Arterioles to capillaries
Ateriole, Metarteriole, Precapillary-sphincter, capillary
How does vasoconstriction effect blood pressure in arterioles?
Increases blood pressure
Main function of Capillaries aka Exchange Vessels
Exchange of gases and nutrients
Capillaries are small but have large surface area because?
to contact all body cells
more capillaries to more active cells
Capillary walls are made up of?
Single endothelial cell layer and basement membrane
What is a capillary bed?
Network of capillaries supplying an organ/tissue
What is the function of the Metarteriole in the Capillary Bed
Initial segment of connection passageway
Smooth muscles adjusts flow rate through capillary bed
What is the arteriovenous shunt?
Connection b/w arteriole and venule
Blood bypasses capillary bed
What is the thoroughfare channel?
Most direct passageway through capillary bed
Contains no muscle
What are Precapillary sphincters?
Bands of smooth muscle
Control flow into capillary bed
The capillary bed may be supplied by multiple arteries called?
Collaterals
The process that blood vessels join together is called?
Arterial anastomosis
What is a terminal artery or end artery?
Artery that is only supplier to a tissue/organ
Three types of capillaries?
Continuous, Fenestrated, Sinusoids
Continuous capillaries are found where?
Brain, lungs, skeletal/smooth mm, CT
Continuous capillaries main function?
Permits diffusion of substances
Prevents blood cell/plasma protein loss
Where are Fenestrated capillaries found
Brain/thyroid glands, intestines, kidneys
Fenestrated capillaries contain what?
Windows for rapid exchange of water/large solutes
Sinusoidal capillary characteristics
Wider fenestrations, no basement membrane,
Where are Sinusoidal capillaries found?
RBM, spleen, liver, pituitary, parathyroid
What do portal systems do?
Lets blood pass from one capillary network to another (shortcut)
Two locations where Portal systems are found?
Liver, Pituitary gland
Hepatic Portal System does what?
Transports blood to liver from GI tract and spleen
Hypophyseal Portal System does what?
Connects capillary beds of hypothalamus and pituitary gland
What are Venules
Small veins that draw from capillaries to return to heart
Blood flow through smallest vessels occurs in all tissues/organs except?
Cornea and epidermis
Characteristics of veins?
Larger diameter lumen and thinner walls, less contraction
Veins and venules are under low pressure, so blood tends to do what?
stop and pool
One way valves are used in veins for?
Preventing backflow and keeping blood moving forward
Mechanisms that maintain flow of blood in veins against gravity?
Valves, skeletal muscles, respiratory pumps,
What is vascular sinus?
Vein with no smooth muscle
Double veins connect via channels called?
Anastomotic veins
What are varicose veins? What causes them?
Pooling of blood due to valves not working
Where are varicose veins m/c found?
Lower extremities/esophagus
Varicose vein causes
mechanical, stress, pregnancy, eating habits
What is angiogenesis?
Growth of new blood vessels for wound/uterine healing
What are tumor angiogenesis factors?
Blood vessel growth for nourishment of tumor cells
Where is more blood volume contained?
Systemic venous system
Where are blood reservoirs located?
Venous networks from digestive organs to liver
What is the function of vasoconstriction in the venous system?
Maintain blood volume in arterial system even w/ blood loss
