2.4 Circulatory system
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What are the 3 organs of the circulatory system
Circulatory system are dynamic structures that can...(3)
What do the organs of circulatory system transport? (3)
Systematic circulation ) what is the route of blood flow?
Arteries to capillaries to veins
What are capillary beds?
Site of product interchange where O2, CO2, and nutrients/waste exchanged
Where does the interstitial fluid returned by lymphatic system drained into?
Large veins close to the heart
Blood vessel structure) what are the 3 walls called?
Blood vessel structure) how many layers are there?
Blood vessel structure) inner layer
Blood vessel structure) middle layer
Blood vessel structure) outer layer
Blood vessel structure) Inner layer: description
- Intimate contact with blood in the lumen
- *its the innermost layer that's why
Blood vessel structure) Inner layer: what does it contain?
endolethium cells (smooth epithelial cells lining) that nourishes the Luminal lining through blood
Blood vessel structure) Inner layer: in vessels greater than 1 mm, a
subendothelial layer containing a basement is present
Blood vessel structure) Tunica media : what does it contain
It contains smooth muscle for vasoconstriction & vasodilator which controls blood pressure
Blood vessel structure) Adventitia : composed of
Mainly loosely woven collagen fibers that protect and reinforce vessel
Blood vessel structure) Adventitia : in larger veins, a network of elastic fibers is also present which
Allows for stretch & rebound of venous walls
Located in outer layers: nervi vascular
Vasomotor nerves of ANS located in outer layers for innervation of smooth muscle in tunica media
Located in outer layers: vasa vasorum
- It is a blood supply network that nourishes outer layer of larger blood vessels of the body
- *red and blue small dots in schematic
Arteries ) main function
Convey blood away from the heart
Arteries ) characteristics (5)
-smaller lumen than veins of same name
-thicker walls than veins of same name
-resist collapse due to thick walls
-tunics are more distinct than in veins
-tunica media is the thickest of the 3
Arteries ) can be classified as 3 things
Arteries ) Classified: large or elastic
They conduct blood away from the heart
Arteries ) Classified: medium or muscular
distribute blood to different body regions
Arteries ) Classified: small or arterioles
Small diameter creates resistance slowing down the flow of the blood for exchange of products within capillaries
Arteries ) Large or Elastic Arteries : 3 characteristics
-3 distinct tunics
-very elastic walls
Arteries ) Large or Elastic Arteries : what does its elastic walls allow it to do
To stretch with ventrical contraction & then recoil which allows it to maintain blood pressure between contractions
Arteries ) Large or Elastic Arteries : major function
conduct blood away from heart to conducting arteries
Arteries ) Large or Elastic Arteries : where can they be found (3)
-major arteries from aorta
Arteries ) medium or muscular arteries : characteristics (3)
-3 tunics with media being the largest
- -lots of smooth muscle
- *bc media is the largest
Arteries ) medium or muscular arteries : major function
- distirubte blood to organs or working muscles
- *thus AKA distributing arteries
Arteries ) medium or muscular arteries : regulates blood supply by
Contracting and relaxing of smooth muscle (vasoconstriction/dilation) under the influenced of nervi vasculari
Arteries ) medium or muscular arteries : what is significant about how thick its media is?
media is thicker than elastic arteries also thus contains more smooth muscle
Arteries ) small arteries and Arterioles : where can 3 tunics be found in?
Only in the largest of small arteries
Arteries ) small arteries and Arterioles : what can only be found in smallest of small arteries?
Only endothelium and smooth muscle
Arteries ) small arteries and Arterials: small arteries contain...
3-8 layers of smooth muscle
Arteries ) small arteries and Arterioles : arterioles have
1-2 layers of smooth muscle
Arteries ) small arteries and Arterioles : AKA
Arteries ) small arteries and Arterioles : major function
- Regulate the distribution of blood to tissues by vasoconstriction and vasodilation
- *ANS control
Arteries ) small arteries and Arterioles : which tissue do they have the most of?
Smooth muscle makes the bulk of wall
Capillaries ) characteristics (3)
-smaller blood vessels
-single layer of endothelial cells
-3 types of of capillaries
What are the 3 types of capillaries ?
Continuous Capillaries : Characteristics (3)
-located in most tissues
-endothelial cells linked by tight junctions which provides an uninterrupted lining of the vessel
-least permeable most common
Continuous Capillaries : how are products exchanged?
Thru cleft between junctions & cytoplasm of endothelial cells
Which of the 3 capillaries is the most common?
Where are continuous capillaries found in?
Skin, muscle, lung
Fenestrated capillaries: what does fenestra mean?
Fenestra capillaries ) Porous
endothelial cells contain little oval pores in cell membrane that allow for easy formation of filtrate or absorption of fluids from intercellular environment
Fenestra capillaries ) what do they deliver? (3)
Hormones, collect nutrients, and form urine
Fenestra capillaries ) where are these located?
- In places where products must be easily emptied into the blood
- *endocrine delivering hormones
Discontinuous capillaries) leaky capillaries
allow large molecules and blood cells to pass through
Discontinuous capillaries ) basement membrane
It has an incomplete membrane
Discontinuous capillaries ) what does it large irregular lumens do?
Slows the speed of flow
Discontinuous capillaries ) where are these found?
In areas requiring filtration of large products & cells across the capillaries
What is capillary bed?
Network of capillaries formed by precapillary arterioles & post capillary venue
Capillary bed: sequence (2)
Each individual capillary branching from metaarterioles contains a cuff of smooth muscle, precapillary sphincter. When precapillary sphincter opened, they allow rich O2 blood to flow into true capillaries bed for product exchange between microcirculation & interstitial environment.
-low O2 blood received by post capillary venue by way of thoroughfare channel
Ateriovenous shunt) process
Capillary beds are bypassed altogether by atriovenous shunt. Arterial blood will shunt directly into venous system for delivery elsewhere in body
Ex) exercise under sympathetic control opens capillary bed in working muscle. At the same time, this shunt is active in gut b/c they only work under parasympathetic
Veins) main function
Return blood towards the heart
Veins) characteristics (6)
-larger lumens than arteries of same name
-thinner walls than same arteries
-tunics are less distinct
-tunica adventitia is the thickest layer
- -contain valves
- *one way process
Veins) 3 ways they are classified
Veins) small veins: (4) composed
-composed of leaky endothelium
- -thin tunica media
- *little smooth muscle
-do not contain valves
Veins) small veins: which are the smallest?
Post capillary venules
Veins) small veins: without elastic tissue,
They convey blood to veins
Veins) medium veins: composition (3)
-thickest layer is the adventitia
-contain valves to facilitate correct flow of blood back to heart
-named veins of the viscera and distal extremities often accompany artery of same name
Veins) medium veins: where can these be found?
Veins) larger veins: (2) composition
-thickest layer is the adventitia
-central body veins do not contain valves
Pumps blood from the lower extremity upwards
Calf Pump) What's another organthat does this also
- *that's why when people who suffer from venous insufficiency are often told to take walks & breathing techniques
Veins are capacitance vessels AKA
What percent of blood volume is in veins
How can veins hold so much blood?
Possible bc they ae able to stretch & hold under low pressure situations
What are varicose veins
Veins that have become diluted due to incompetent valves so it allows back flow of blood, pooling.
Factors that contribute to varicose veins (4)
What are venous sinuses?
Large vessels that collect blood
What are the 2 venous sinuses
Anastomoses) arterial: (2)
-alternate channels to insure blood flow for vital organs
-more than one supply
Anastomoses) veins: (3)
Have numerous anastomoses to facilitate blood return
-numerous between superficial and deep veins
-blood can easily be recruited around damage areas
2 things systematic circulation does
-retrieves waste products CO2
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