Chr. 21 - Blood Vessels and Hemodynamics Flashcards
[21.1] What are arteries?
Blood vessels carrying blood away from the heart.
[21.1] What are arterioles?
Smaller arteries more distal from the heart.
[21.1] What are capillaries?
Tiny blood vessels with thin walls to allow exchange of substances with tissues.
[21.1] What are venules?
Small veins forming from capillaries as blood begins to return to the heart.
[21.1] What are veins?
Blood vessels carrying blood to the heart.
[21.1] What are the layers of a blood vessel’s structure?
- Tunica interna
- Tunica media
- Tunica externa.
[21.1] Describe the tunica interna.
The inner lining of a blood vessel in direct contact with blood, comprised of multiple layers: endothelium and the basement membrane.
[21.1] Describe the tunica media.
The middle layer of blood vessels comprised of muscular and connective tissues, varying among blood vessels. Provides ability of vasoconstriction and vasodilation.
[21.1] Describe the tunica externa.
The outer covering of a blood vessel consisting of elastic and collagen fibers, nerves, and blood vessels supplying themselves - vasa vasorum.
[21.1] What is the internal elastic lamina?
A layer of elastic fibers in between the tunica interna and tunica media.
[21.1] What is the external elastic lamina?
A layer of elastic fibers in between the tunica media and tunica externa.
[21.1] Describe elastic arteries.
Largest arteries in the body diameter-wise, but with thin walls and large internal/external elastic laminae and a proportionally thicker tunica media that incorporates elastic lamellae. Also known as conducting arteries.
[21.1] What is the function of elastic arteries, and how is this achieved?
Aid in propelling blood to the body as the ventricles relax. Done by forming a pressure reservoir, stretching as blood is pumped into them by the heart. Once stretched, their elastic nature recoil and squeeze blood further along , exerting the stored pressure as they return to normal shape.
[21.1] Describe muscular arteries.
Medium-sized arteries containing higher amounts of smooth muscle and fewer elastic fibers. Capable of greater vasoconstriction and vasodilation and feature thicker internal elastic lamina while having thinner external elastic lamina. Tunica externa thicker than tunica media and contains fibroblasts and collagen fibers allowing for changes in diameter of vessel without causing negative effects.
[21.1] What is anastomoses?
The union of two or more arteries supplying the same body region.
[21.1] What is collateral circulation?
The alternative blood flow to a body part through anastomoses.
[21.1] What are end arteries?
Arteries that do not anastomoses.
[21.1] What is a metarteriole?
The terminal end of an arteriole as it reaches the capillary junction.
[21.1] What is the precapillary junction?
A sphincter formed by muscle cells of the arteriole monitoring blood flow into the capillary.
[21.1] What is resistance in terms of blood vessel?
Opposition of blood flow due to friction of blood and blood vessels. Inversely related to blood vessel size.
[21.1] What is a postcapillary venule?
A venule receiving blood from a capillary.
[21.1] What is microcirculation?
The flow of blood from a metarteriole into a capillary, then into a postcapillary venule.
[21.1] What are exchange vessels?
Capillaries, as they are the primary site of substance exchange with interstitial fluid.
[21.1] What is a capillary bed?
A network of 10-100 capillaries arising from a single metartiole.
[21.1] What is vasomotion?
The intermittent contraction and relaxation of smooth muscle in arterioles promoting blood flow into capillaries.
[21.1] What is a thoroughfare channel?
The distal end of the main channel of a capillary branching from the arteriole, containing no smooth muscle.
[21.1] What are the types of capillaries?
- Continuous capillaries
- Fenestrated capillaries
- Sinusoids.
[21.1] What are continuous capillaries?
Majority of capillaries, defined by the plasma membrane of endothelial cells forming a continuous tube interrupted by intercellular clefts.
[21.1] What are intercellular clefts?
Gaps in neighbouring endothelial cells.
[21.1] Describe fenestrated capillaries.
Capillaries with small pores, fenestrations, in their plasma membranes.
[21.1] Describe sinusoids.
Wider and more winding capillaries with large fenestrations and intercellular clefts, allowing for proteins and blood cells to enter and exit the blood.
[21.1] What is a portal system?
When blood passes from one capillary network to a different capillary network.
[21.1] What are muscular venules?
Venules extending from postcapillary venules featuring smooth muscle.
[21.1] What are the differences in the structure of veins compared to arteries?
While composed of the three basic layers, the tunica interna and tunica media of veins are considerably thinner, and lack internal/external elastic laminae.
[21.1] What are valves in relation to blood vessels?
Thin folds of the tunica interna within veins preventing backflow of blood in veins due to lower pressures.
[21.1] What is a vascular sinus?
A vein with thin endothelial wall and no smooth muscle and extra dense connective tissue providing support.
[21.1] What are anastomotic veins?
Vein connections between venous channels, forming a ladder-like connection between two veins following an artery.
[21.1] What are superficial veins?
Veins in the subcutaneous layer unaccompanied by parallel arteries.
[21.1] What are deep veins?
Veins travelling between skeletal muscle.
[21.1] What are blood reservoirs?
A large portion of blood volume that remains in veins that can be diverted quickly by venoconstriction.
[21.2] What is capillary exchange?
The movement of substances between blood and interstitial fluid.
[21.2] What are the basic mechanisms of capillary exchange?
Diffusion, transcytosis, and bulk flow.
[21.2] What is transcytosis in terms of capillary exchange?
Substances are enclosed in pinocytic vesicles of endothelial cells, transported across the cell, and expelled by exocytosis.
[21.2] What is bulk flow in terms of capillary exchange?
The pressure-driven passive process of a large amount of ions or molecules flowing in the same direction and is mostly used for solute exchange between blood and interstitial fluid.
[21.2] What is filtration?
Bulk flow from blood capillaries into interstitial fluid.
[21.2] What is reabsorption?
Bulk flow from interstitial fluid into capillaries.
[21.2] What are the pressures of fiiltration?
Blood hydrostatic pressure and interstitial fluid osmotic pressure.
[21.2] What is blood hydrostatic pressure?
Pressure exerted on blood by the pumping action of the heart, pushing fluid into interstitial fluid.
[21.2] What is interstitial fluid osmotic pressure?
The pressure exerted by concentration of solutes within interstitial fluid pulling fluid into the interstitial fluid. Usually low or negligble.
[21.2] What are the pressures of reabsorption?
Blood colloid osmotic pressure and interstitial hydrostatic pressure.
[21.2] What is blood colloid osmotic pressure?
Pressure exerted by the concentration of solutes within the blood, pulling fluid into the blood
[21.2] What is interstitial fluid hydrostatic pressure?
A negligible pressure exerted by interstitial fluid pushing fluid into the blood.
[21.2] What is net filtration pressure?
Balance between filtration pressures and reabsorption pressures indicating the direction of fluid movement. Mainly calculated by blood hydrostatic pressure and blood colloid osmotic pressure.
[21.2] Describe the action of net filtration pressure as it travels through a capillary.
At the metarteriole, net filtration pressure favours filtration as blood hydrostatic pressure is higher than blood colloid osmotic pressure. As it travels to the postcapillary venule end, BHP drops under BCOP and favours reabsorption.
[21.3] What is hemodynamics?
The forces involved in circulating blood.
[21.3] What is blood flow?
The volume of blood that flows through any tissue during a given time period.
[21.3] What is blood pressure?
The hydrostatic pressure exerted by blood on the walls of blood vessels.
[21.3] What is systolic blood pressure?
The pressure on blood vessels during ventricular contraction.