Chapter 21 - The Cardiovascular System: Blood Vessels and Hemodynamics Flashcards
What are the Layers of a Blood Vessel?
In general, a Blood Vessel has 3 layers:
1- Tunica Interna (Tunica Intima):
Innermost layer
Adjacent to Lumen
2- Tunica Media:
Middle layer
Smooth muscle and Elastic Fibers
Thicker in arteries than in veins
3- Tunica Externa:
Outermost layer
Adjacent to surround tissue
(veins have more blood flow because of larger lumen compared to arteries)
What is Components of Tunica Interna in Arteries?
From deep to superficial:
1- Endothelium
2- Basement Membrane
3- Internal Elastic Lamina
What is Components of Tunica Media in Arteries?
From deep to superficial:
1- Smooth Muscle
2- External Elastic Lamina
What is Components of Tunica Interna in Veins?
From deep to superficial:
1- Endothelium
Valves made from Endothelium
2- Basement Membrane
What is Components of Tunica Media in Veins?
Smooth Muscle
What is Components of a Capillary?
From deep to superficial:
1- Endothelium
2- Basement Membrane
What is Artery?
Artery:
Carry blood away from heart to tissues
Walls of arteries are elastic, which allows them to absorb the pressure created by ventricles of the heart as they pump blood into the arteries
Because of smooth muscle in the Tunica Media, arteries can regulate their diameter
What are the Types of Arteries?
1- Elastic Arteries (Conducting Arteries):
Large diameter
More elastic fibers
Less smooth muscle
Function as pressure reservoirs
2- Muscular Arteries (Distributing Arteries):
Medium diameter
More smooth muscles
Fewer elastic fibers
Distribute blood to various parts of the body
What is Anastomosis?
Anastomosis:
Union of the branches of 2 or more arteries supplying the same region of the body
Provide alternative route for blood flow
End Arteries:
Arteries that do not form an Anastomosis
If an End Artery is blocked, blood cannot get to that particular region of the body, and Necrosis can occur
What is Capillary?
Thin Squamous Cells
Capillaries:
Microscopic vessels that usually connect Arterioles and Venules
Capillary Wall:
Composed of a single layer of cells and a Basement Membrane
Because their walls are so thin, Capillaries permit the exchange of nutrients and wastes between blood and tissue cells
What is Blood Flow Through Capillaries?
Capillaries branch to form an extensive capillary network throughout the tissues and are found near almost every cell in body
Eases off BP
1- If Precapillary Sphincters relaxed:
Arteriole
Metarteriole
Capillary and Thoroughfare Channel
Postcapillary Venule
Venule
2- If Precapillary Sphincters contracted:
Arteriole
Metarteriole
Thoroughfare Channel
Postcapillary Venule
Venule
What is Types of Capillaries?
1- Continuous Capillary:
Basement Membrane complete
Pinocytic Vesicles
Intercellular Clefts small
2- Fenestrated Capillary:
Basement Membrane complete
Pinocytic Vesicles
Intercellular Clefts small
Fenestrations (pores)
3- Sinusoid Capillary:
Basement Membrane incomplete
No Pinocytic Vesicles
Intercellular Clefts large
Bigger molecules can pass through
What is Venule?
Venules:
Small vessels that are formed by the union of several capillaries
Darin blood from capillaries into Veins
What is Vein?
Veins:
Formed by union of several Venules
Compared to arteries, veins have:
Thinner Tunica Interna and Tunica Media
Thicker Tunica externa
Less Elastic tissue
Less smooth muscle
Contain Valves that allow blood to flow through
What is Size, Description of Layers, and Function of Elastic Artery?
1- Size:
Largest in body
2- Tunica Interna:
Well-defined Internal Elastic Lamina
3- Tunica Media:
Thick dominated by elastic fibers
Well-defined External Elastic Lamina
4- Tunica Externa:
Thinner than Tunica Media
5- Function:
Conduct blood from heart to Muscular Arteries
What is Size, Description of Layers, and Function of Muscular Artery?
1- Size:
Medium-sized arteries
2- Tunica Interna:
Well-defined Internal Elastic Lamina
3- Tunica Media:
Thick dominated by smooth muscle
Thin External Elastic Lamina
4- Tunica Externa:
Thicker than Tunica Media
5- Function:
Distribute blood to Arterioles
What is Size, Description of Layers, and Function of Arterioles?
1- Size:
Microscopic
2- Tunica Interna:
Thin with a Fenestrated Internal Elastic Lamina that disappears distally
3- Tunica Media:
1 or 2 layers of circularly oriented smooth muscle
Distalmost smooth muscle cell forms a Precapillary Sphincter
4- Tunica Externa:
Loose collagenous connective tissue and sympathetic nerves
5- Function:
Deliver blood to capillaries
Help regulate blood flow from arteries to capillaries
What is Size, Description of Layers, and Function of Capillary?
1- Size:
Microscopic
Smallest in body
2- Tunica Interna:
Endothelium
Basement Membrane
3- Tunica Media:
None
4- Tunica Externa:
None
5- Function:
Permit exchange of nutrients and wastes between blood and interstitial fluid
Distribute blood to Postcapillary Venules
What is Size, Description of Layers, and Function of Postcapillary Venule?
1- Size:
Microscopic
2- Tunica Interna:
Endothelium
Basement Membrane
3- Tunica Media:
None
4- Tunica Externa:
None
5- Function:
Pass blood into Muscular Venules
Permits exchange of nutrients and wastes between blood and interstitial fluid
Function in WBC Emigration (Diapedesis)
What is Size, Description of Layers, and Function of Muscular Venule?
1- Size:
Microscopic
2- Tunica Interna:
Endothelium
Basement Membrane
3- Tunica Media:
1 or 2 layers of circularly oriented smooth muscle
4- Tunica Externa:
Sparse
5- Function:
Pass blood into Veins
Act as a reservoir for accumulating large volumes of blood along with Postcapillary Venules
What is Size, Description of Layers, and Function of Veins?
1- Size:
0.5mm to 3cm
2- Tunica Interna:
Endothelium
Basement Membrane
No Internal Elastic Lamina
Contain Valves
Lumen larger than in accompanying artery
3- Tunica Media:
Much thinner than arteries
No External Elastic Lamina
4- Tunica Externa:
Thickest of the 3 layers
5- Function:
Return blood to heart
Facilitated by Valves in limb veins
What is Blood Distribution?
At rest, largest portion of blood is in Systemic Veins and Venules, which are considered Blood Reservoirs
1- Systemic Veins and Venules: 64%
2- Systemic Arteries and Arterioles: 13%
3- Pulmonary Vessels: 9%
4- Heart: 7%
5 Systemic Capillaries: 7%