Chapter 21 - Cardiovascular System: Blood Vessels and Hemodynamics Flashcards
What is hemodynamics?
The forces involved in circulating blood throughout the body
What are the 5 main blood vessels?
- Arteries
- Aterioles
- Capillaries
- Venules
- Veins
How do arteries carry blood?
Away from the heart to other organs
How do veins carry blood?
Away from the tissues and back to the heart
What are the three basic layers of a blood vessel?
- Tunica interna (intima)
- Tunica media
- Tunica externa (adventia)
What is the lumen?
The interior opening of the blood vessel
- in direct contact with the blood as it flows
What is the tunica interna (intima)?
The innermost lining of a blood vessel
- in direct contact with blood as it flows
What is the tunica media?
The middle layer of a blood vessel
- muscular and connective tissue layer
What is the tunica externa (adventia)?
The outermost layer of a blood vessel
What is vasoconstriction?
A decrease in the diameter of the lumen of a blood vessel
- when the smooth muscle in the tunica media contract
What is vasodilation?
An increase in lumen diameter in a blood vessel
What are elastic arteries?
The largest arteries in the body (largest diameter)
- includes the aorta and pulmonary trunk
- as well as the aorta’s initial branches
What is the function of elastic arteries?
Help propel blood onward while the ventricles are relaxing
- also called conducting arteries
What are muscular arteries?
Medium-sized arteries
- capable of great vasocontriction and vasodialation
- able to contract and maintain a partial contraction (vascular tone)
- also called distributing arteries
What is the function of arterioles?
Regulate the flow of blood into the capillary networks of the body’s tissues
What is the metarteriole?
The terminal end of the arteriole
- tapers towards the capillary junction
What is the function of the precapillary sphincter?
Monitors the blood flow into the capillary
What is resistance?
The opposition to blood flow
- arterioles play a key role in regulating blood flow into capillaries
How does vasodilation and vasoconstriction affect blood pressure?
Vasoconstriction = increases blood pressure
Vasodilation =decreases blood pressure
What are capillaries?
The smallest blood vessel
- connect arterial outflow to the venus return
What is microcirculation?
The flow of blood from a metarteriole through capillaries and into a postcapillary venule (venule that receives blood from a capillary)
What is the primary function of capillaries?
The exchange of substances between the blood and interstitial fluid
What is a capillary bed?
A network of 10-100 capillaries that arises from a single metarteriole
What is the thoroughfare channel?
Provides a direct route for blood from an arteriole to a venule, thus by-passing capillaries
What are the three kinds of capillaries?
- Continuous capillaries
- Fenestrated capillaries
- Sinusoids
Describe continuous capillaries.Where are they found?
The plasma membranes of endothelial cells form a continuous tube that is interrupted only by intercellular clefts (gaps between neighbouring endothelial cells)
- found in CNS, lungs, skin, muscle tissue
Describe fenestrated capillaries.Where are they found?
Plasma membranes of the endothelial cells have many small pores (fenestrations)
- found in kidneys, villi of small intestine, choroid plexuses of the ventricles of the brain, ciliary processes of the eyes and most endocrine glands
Describe sinusoids.Where are they found?
Wider and more winding than other capillaries
- liver, spleen, anterior pituitary, parathyroid, adrenal glands
How does blood circulate in a portal system?
Blood passes from one capillary network into another through a vein (portal vein)
What is the function of venules?
Drain the capillary blood and begin the return flow back towards the heart
Describe the major structural differences between veins and arteries.
Vein
- thin walls relative to diameter, blood pressure is lower in veins, lumen is larger in veins
What do veins contain that arteries do not?
Valves!
What is the function of venus valves?
Valves aid in venus return by preventing the backflow of blood
- low blood pressure in veins allows blood returning to the heart to slow and even back up
What is a vascular (venous) sinus?
A vein with a thin endothelial wall that has no smooth muscle
- dense connective tissue replaces the tunica media & tunica externa in providing support
What is an anastomosis?
The union of the branches of two or more arteries supplying the same body region
What is collateral circulation?
The alternative route of blood flow to a body part through an anastomosis
- may also occur between veins/arterioles/venules
How is your blood distributed when your body is at rest?
64% in systemic veins and venules 13% in systemic arteries 7% in systemic capillaries 9% in pulmonary blood vessels 7% in the heart
What function as blood reservoirs of the body?
Systemic veins and venules
- contain a larger percentage of the blood volume
Name the 5 types of blood vessels in order as the leave the heart.
- Arteries
- Arterioles
- Capillaries
- Venules
- Veins
What is capillary exchange?
The movement of substances between blood and interstitial fluid
What are the three basic mechanisms for capillary exchange?
- Diffusion
- Transcytosis
- Bulk flow
What is the most important method of capillary exchange?
Diffusion
- important for SOLUTE exchange
What are some examples of substances that enter and leave capillaries by simple diffusion?
- oxygen
- carbon dioxide
- glucose
- amino acids
- hormones
What is transcytosis?
Method of capillary exchange
- substances in blood plasma become enclosed within tiny pinocytic vesicles that first enter endothetlial cells by endocytosis, then move across the cell and exit on the other side by exocytosis
What is transcytosis important for?
Important for movement of large, lipid in
-soluble molecules that cannot cross capillary walls in any other way
What is bulk flow?
Method of capillary exchange
- passive process in which LARGE numbers of ions, molecules or particles in a fluid move together in the same direction
- move faster than diffusion
When does bulk flow occur?
Occurs from an area of higher pressure to an area of lower pressure
What is bulk flow important for?
Regulation of the relative volumes of blood and interstitial fluid
What is filtration?
Pressure-driven movement of fluid and solutes FROM blood capillaries INTO intersitial fluid
What is reabsorption?
Pressure-driven movement FROM interstitial fluid INTO blood capillaries
What two pressures promote filtration?
- Blood hydrostatic pressure
2. Interstitial fluid osmotic pressure
What two pressures promote reabsorption?
- Blood colloid osmotic pressure
2. Interstitial fluid hydrostatic pressure
What is the net filtration pressure (NFP)?
Balance of filtration and reabsorption
- determines whether the volume of blood and interstitial fluid remains steady or changes
What does blood hydrostatic pressure do (BHP)?
“Pushes” fluid out of capillaries into interstitial fluid
What does interstitial fluid osmotic pressure do (IFOP)?
“Pulls fluid from capillaries into interstitial fluid
- approx. 1 mmHg
What does blood colloid osmotic pressure do (BCOP)?
“Pulls” fluid from interstitial spaces into capillaries
What does interstitial fluid hydrostatic pressure do (IFHP)?
“Pushes” fluid from interstitial spaces into capillaries
- approx. 0 mmHg
What is the equation for determining net filtration pressure (NFP)?
NFP = (BHP+IFOP) - (BCOP+IFHP)
What force opposes BHP?
IFHP (interstitial fluid hydrostatic pressure)
What force opposes BCOP?
IFOP (interstitial colloid osmotic pressure)
When will filtration occur?
If pressure that pushes fluid into capillaries >pressure that pulls fluid into capillaries–> fluid will move from capillaries into interstitial spaces
When will reabsorption occur?
If pressure that pushes fluid out of interstitial spaces >pressure that pulls fluid out of capillaries–> fluid will move from interstitial spaces into capillaries
What is an edema?
An abnormal increase in interstitial fluid volume
- caused if filtration greatly exceeds reabsorption