Cardiovascular Blood Vessels Flashcards
(27 cards)
What are the Vessels of the Body
Vessels of the Body: Made of Same Tissue Layers
*Blood vessels
- Transport blood
- Continuous circuit between heart and capillaries
* Lymph vessels
- Transport lymph (fluid that has accumulated in tissues)
- One way→not a circuit
What are the Layers of Vessel Walls?
- Tunica intima
- Endothelium (simple squamous epithelium)
- Subendothelial layer (loose areolar CT)
- Tunica media
- Smooth muscle
- Arranged circularly for vasoconstriction
- Tunica external
- Loose areolar CT
- Some large vessels have own blood supply =
vasa vasorum
What are the structures of the vessels?
*Tunica externa of veins
- Is of equal thickness or thicker than arteries
*Tunica intima of veins form valves
*Tunica media of artery is thicker with more elastic fibers
- Arterial walls are thicker and stronger than a comparable vein
- They are under high pressure
*Arteries appear rounder than veins in cross-section (see image on left)
What is an Elastic Artery?
- Elastic arteries are found right off of the ventricles
- Ex. Aorta, pulmonary trunk
- The ability to expand and recoil helps smooth out pressure surges
- Tunica media has significant amount of elastin
What are Muscular Arteries?
*Supply organs and skeletal muscles
*Have all three tunics
*Tunica media
- Less elastin and more smooth muscle
- More control over lumen size of vessel to adjust
blood flow to organs
*Examples include radial artery, femoral artery
What are Arterioles?
*Are branches of muscular arteries
*Constrict and dilate quickly to regulate blood flow to capillaries
*Larger arterioles
- Have all 3 tunics and elastic in tunica intima
*Smaller arterioles
- Have tunica media and endothelium only
What are the components of Capillaries?
*Approximate diameter of single red blood cell
*Lack tunica media and tunica externa layers
- Thin, good for diffusion of gases
- Made of only a single layer of endothelial cells
* Often form capillary beds
What are Precapillary sphincters?
*Precapillary sphincters (smooth muscle) regulate
blood flow
- Sphincters open →blood fills capillary beds
What happens when Precapillary sphincters close?
Precapillary sphincters closed
* Blood passes through capillary bed via the metarteriole a “thoroughfare channel”
* Tissue supplied by this capillary bed are bypassed
- This occurs in response to tissue needs for glucose/oxygen
What is the anatomy of capillaries?
Capillaries:
*Thin walls allow for exchange between components of blood & interstitial fluids of tissue
*Endothelium (simple squamous epithelium)
*Basement membrane (CT)
*3 types based on levels of
permeability:
1. Continuous
2. Fenestrated
3. Sinusoidal
What is a Continuous Capillary?
- Most common
- Found in skeletal muscles, skin, nervous system
- Tight junctions connect cells
- Decrease permeability (continuous capillaries are the least permeable)
- Intercellular clefts
- Areas where no cell junction(s)
- Allow small molecules to pass in and out of capillary
- Complete basement membrane
- Have pericytes
- Spider-shaped contractile stem cells
- Help control capillary permeability
- Can give rise to new blood vessels
What is Fenestrated Capillary?
*Have tight junctions and intercellular clefts AND pores through endothelial cells called fenestrations (= windows)
*Found where there is a high rate of molecular exchange between tissue and blood
- Ex. Small intestine
What are Sinusoid Capillaries?
- Special fenestrated capillary
- Allows passage of large materials (proteins, blood cells)
- Discontinuous; follow twisted path
- Most permeable
- Allows for blood slowing and multiple exchanges across walls
- Large intercellular clefts
- Incomplete basement membrane
- Fewer tight junctions
- Locations:
- Spleen, bone marrow, lymph nodes, liver
What is the Blood Brain Barrier?
Low-permeability continuous capillaries
* Have tight junctions
* Do not have intercellular clefts
* Only vital molecules (such as glucose) are allowed through (highly selective transport mechanisms)
* Non-charged and lipid soluble molecules can pass through the endothelial cells into brain (ex. Oxygen, carbon dioxide, anesthesia)
Prolonged emotional stress disrupts the BBB
* Tight junctions are opened→toxic substances enter into brain
* Associated with Gulf War Syndrome (chronic fatigue, dizziness, memory loss, depression)
What is the Portal System?
*Blood passes through 2nd capillary bed before returning to heart
*Example:
- Hepatic portal system (of digestive system)
What are veins?
Thinner walls than comparable arteries →lower blood pressure
* Comparing veins of similar size to arteries:
- Lumen of vein is larger
- Tunica media is smaller
What are Venules?
Venules:
* Drain capillaries
* Smallest are made of only endothelium (with
surrounding pericytes)
* Larger venules have endothelium and tunica media
What are Medium veins?
Medium veins:
* Drain venules
* Have all three tunics
* Endothelium forms valves
What are Large veins?
Large veins:
* Medium veins return blood to large veins
* Large veins have all three tunics
* Endothelium forms valves
* Under extremely low pressure
What are the components of veins?
Veins
*Have valves
*Are folds of tunica intima
*Keep blood moving forward (toward heart) under low pressure
What Mechanisms counter low venous
pressure?
Mechanisms to counter low venous
pressure:
* Valves
* Squeezing of veins by adjacent organs
* Ex. When skeletal muscles contract and deep
breathing (respiratory pump)
What are Varicose Veins?
*Most commonly affected veins are superficial veins of lower leg
*Incompetent valves in veins →blood pools, stretching veins and causing misshapen vessels
What are Anastomoses?
*Anastomosis = “coming together”
*Arterial anastomoses
- Provide alternative pathways (collateral
channels) for blood to reach a given body region
– If one branch were blocked, then there is an
alternative source of blood
– Occur in brain, abdominal organs, heart
— Because of anastomoses in the heart, a
coronary artery may be 90% occluded before
a myocardial infarction occurs
*Vein anastomoses more common than arterial
- Ex. Back of your hand (dorsum)
What is Blood Pressure?
Blood Pressure
* Systolic: arterial pressure when left ventricle contracts
* Diastolic: arterial pressure when left ventricle relaxes
