lecture 10 & 11 objectives Flashcards
artery
Artery – any of the tubular branching muscular and elastic walled vessels that carry blood from the heart through the body (primarily oxygenated)
capillary
Capillary – a minute thin-walled vessel in the body; any of the smallest blood vessels connecting arterioles with venules and forming networks throughout the body
vein
Vein – any of the tubular branching vessels that carry blood from the capillaries toward the heart
tunica intima
Tunica intima (outer layer) – made of simple squamous epithelium lining the lumen, with a layer of subendothelial connective tissue. Functions to provide a smooth surface for blood flow, regulate the movement of substances between the blood and vessel walls.
tunica media
Tunica media (middle layer) – made of smooth muscle cells, elastic fibers, and collagen fibers. Functions to help with blood pressure regulation by contracting or relaxing muscle cells and help to maintain vessel fluctuations without ruptures.
Vasoconstriction and vasodilation are regulated here. Also regulates stretching
what is most commonly regulated by the tunica media
vasoconstriction and vasodilation
tunica externa
Tunica externa (outer layer) – made of fibroblasts, collagen fibers, and elastic fibers with varying densities. It anchors by attaching blood vessels to provide stability and prevent movement, maintains structural support and integrity by helping it to resist excessive expansion of the walls, it helps with vascular supply by providing nutrients to the outer layers of the vessel walls, and innervates the vessels.
compare and contrast tunica thickness in arteries, capillaries, and veins
o Arteries: have a thick tunica media to withstand and regulate high bp, the tunica intima is relatively thin, and the tunica externa is present but less pronounced than veins.
o Veins: have a tinner tunica media due to less pressure, have a thicker tunica externa to offer structural support and help return blood to the heart
o Capillaries: have a single layer of endothelial cells (intima), and is to facilitate exchange of gases, nutrients, and wastes between blood and tissues
compare and contrast tunica composition in arteries, capillaries, and veins
o Arteries: Tunica media: primarily smooth muscle and elastic fibers which allow for expansion and contraction with hear beat to help maintain bp and flow. Tunica externa has collagen fibers that provide structural support
o Veins: Tunica media is thinner and has less smooth and elastic tissue. The tunica externa is rich in collagen to help with structural support.
o Capillaries: no smooth of elastic, purely endothelial cells and a basement membrane
compare and contrast tunica lumen diameter in arteries, capillaries, and veins
o Arteries: have a relatively large lumen to allow for rapid blood flow at high pressure
o Veins: has a lumen that is larger than arteries and capillaries, but a smaller diameter. This is so that they can accommodate for the large volume of blood in veins
o Capillaries: have a small lumen which allows for efficient transport of different things
structure and function of elastic conducting arteries
Elastic conducting arteries: have a large diameter with thick walls, high content of elastic fibers in the tunica media to allow for stretch and recoil, relatively thin tunica intima and externa. Functions to act as a pressure reservoir by expanding during systole and recoiling during diastole.
- are termed conducting because they conduct blood from the heart to the muscular arteries
example of elastic conducting arteries
aorta, pulmonary arteries
structure and function of muscular distributing arteries
Muscular distributing arteries: are medium sized arteries that have a thicker tunica media than elastic arteries. The tunica media is rich in smooth muscle fibers but few elastic. It has a thick tunica externa. Helps to distribute blood to specific regions of the body, and allows for vasoconstriction and vasodilation and helping regulate blood flow and pressure by adjusting the diameter of the vessel
- are termed distributing arteries because they are what actually distributes and delivers blood to specific locations
examples of muscular distributing arteries
Brachial artery, femoral artery, renal arteries
structure and function of arterioles
Arterioles: are the smallest arteries with a very thin tunica externa and a relatively thicker tunica media composed mostly of smooth muscle. The lumen diameter is narrow in comparison to larger arteries. Works to regulate blood flow to the tissues and bp by contracting or relaxing the smooth muscle in their walls. The primary site of resistance in the circulatory system which helps to influence peripheral resistance and bp.
- can also be termed resistance vessels because they help to control changing pressure and how things move
examples of arterioles
Found throughout the body, are just before the capillaries
structure and function of capillaries
Capillaries: the smallest and thinnest blood vessels with walls of a single layer of endothelial cells and a thin basement membrane, no smooth or elastic tissue. Allows for easy exchange of gases, nutrients and waste across the walls; allows for diffusion.
- are seen as the spot for change or exchange
examples of capillaries
Present throughout the body, especially in the tissues like muscles, lungs, and kidneys
structure and function of venules
Venules: are small veins formed by the convergence of capillaries, thinner walls than veins, small amount of smooth muscle and elastic fibers. Thin Tunica median, and less developed tunica externa. They collect deoxygenated blood from the capillaries and work to return it to the heart, and serve as a transition point between the capillaries and larger veins
structure and function of veins
Veins: larger vessels with wide lumen, relatively thin walls, thin tunica media, prominent tunica externa, has valves to prevent backflow of blood. It has smooth muscles in the media, and collagen and elastic in the externa. Carry deoxygenated blood back to the heart, have wide lumen to hold a large volume of blood, rely on skeletal muscle contraction and valves to facilitate the return of blood to the heart
- veins are termed the blood reservoir because they hold around 65% of all blood capacity and help blood to get back to the heart
examples of veins
Superior and inferior vena cava, jugular veins, femoral veins
vasoconstriction
Constriction – reduces blood supply to the skin, can be in response to cold
- when the blood vessel narrows
vasodilation
Dilation – increases blood supply to the skin, is when muscles around the vessels relax, can be in response to hot temperatures
- when the blood vessel widens
continuous capillaries
Continuous capillaries: The walls are continuous and made up of endothelial cells that are tightly joined by tight junctions. The basement membrane is also continuous and intact. These capillaries have small intercellular clefts (gaps) that allow for the passage of small molecules like glucose, ions, and gases. Function in exchange of small molecules and gases but prevent movement of larger molecules, have tight junctions to limit permeability and what exits the cell. Mostly in the tissue, including the muscles, skin, lungs, and brain
- often have associated pericytes
fenestrated capillaries
Fenestrated capillaries: the endothelial cells have pores (fenestrae) in their walls, which make these capillaries more permeable than continuous capillaries. These pores are often covered by a thing diaphragm but still allow for the passage of larger molecules. They are adapted for more rapid movement or larger molecules.
- often found in areas that need rapid absorption and filtration like the kidneys, small intestine, endocrine glands
sinusoidal discontinuous capillaries
Sinusoidal discontinuous capillaries: These have larger gaps between the endothelial cells and a discontinuous basement membrane. This allows for the passage of large molecules, including blood cells, across the capillary walls. The lumen of sinusoidal capillaries is often wider than that of continuous or fenestrated capillaries. Are specialized for the exchange of large molecules and cells (blood cells and proteins), are vital for the immune responses and blood cell formation. Are found in many specialized organs like the spleen, liver, bone marrow, and certain lymphoid tissues.
- this is where it is easiest for things to slide through because not only are the walls thin, but there is also minimal pressure so it is easy for things to go through
Describe how muscular compression and the respiratory pump aid venous return.
Muscular compression, also known as the “skeletal muscle pump,” and the respiratory pump both work together to facilitate venous return by squeezing veins, increasing pressure within them, and pushing blood towards the heart, primarily through the action of surrounding muscles contracting and the pressure changes in the thoracic cavity during breathing, respectively; with the help of one-way valves in veins preventing backflow
Explain the mechanisms of capillary exchange of gases, nutrients, and wastes.
Capillary exchange refers to the process by which gases, nutrients, and wastes are exchanged between the blood and the tissues across the walls of capillaries. This process occurs via several mechanisms, depending on the size, solubility, and concentration gradients of the substances being exchanged.
diffusion
filtration
reabsorption
transcytosis
diffusion in muscular compression and the respiratory pump aiding in venous return
Diffusion – the primary process for exchange where substances move from areas of higher concentration to lower concentration. Oxygen will go from capillaries to interstitial fluid to tissues. Carbon dioxide will go from the tissues to the capillaries to the lungs for exhalation. Nutrients like glucose and amino acids diffuse from the blood to the tissues.
filtration in muscular compression and the respiratory pump aiding in venous return
Filtration – the process by which fluids and small solutes move from the blood to the interstitial fluid. It is primarily in the arterial end of the capillaries where hydrostatic pressure is greater than osmotic pressure. Filtration helps to deliver oxygen, nutrients, and other small molecules to tissues.
reabsorption in muscular compression and the respiratory pump aiding in venous return
Reabsorption – the process by which fluid and solutes are drawn back into capillaries from the interstitial fluid due to osmotic pressure. Typically, on the venous ends of the capillaries where osmotic pressure is greater than hydrostatic pressure. This pulls fluid and waste products back into the bloodstream. Works to prevent the loss of essential blood components and helps return excess fluid into circulation. Also for reabsorption of waste products from tissues which are then transported to organs like the kidneys for excretion.
transcytosis in muscular compression and the respiratory pump aiding in venous return
Transcytosis - involves the active transport of large molecules across the endothelial cells of the capillaries. In this process, substances such as proteins or large lipid-soluble molecules are encapsulated in vesicles at one side of the endothelial cell and then transported across the cell to be released on the other side. Especially important for the exchange of larger molecules that cannot simply diffuse through. Plays a large role in the transport of hormones, antibodies, and lipid-soluble substances
define anastomosis
Anastomosis – a interconnection between two structures (specifically between blood vessels)
what is the functional significance of anastomosis
Significance - An anastomosis is a surgical connection between two structures. It usually means a connection that is created between tubular structures, such as blood vessels or loops of intestine. For example, when part of an intestine is surgically removed, the two remaining ends are sewn or stapled together (anastomosed).
Provides an alternate route for blood if one direction is blocked or cut.
Big in heart, brain, abdominal organs, and around the joints. Not around retina, spleen, and kidneys.
the forces that create capillary filtration and reabsorption
Capillary filtration and reabsorption are primarily driven by two opposing forces: hydrostatic pressure which pushes fluid out of the capillary (filtration), and colloid osmotic pressure (oncotic pressure) which draws fluid back into the capillary (reabsorption); the balance between these forces determines the net movement of fluid across the capillary wall, with filtration dominating at the arterial end and reabsorption at the venous end of the capillary
hydrostatic pressure
colloid osmotic pressure
hydrostatic pressure in the forces that create capillary filtration and reabsorption
Hydrostatic pressure - This is the pressure exerted by the fluid within the capillary, pushing against the capillary walls and tending to force fluid out into the interstitial space. At the arterial end of the capillary, where blood pressure is highest, hydrostatic pressure is greater, promoting filtration.
colloid osmotic pressure in the forces that create capillary filtration and reabsorption
Colloid osmotic pressure - This pressure is created by the presence of large plasma proteins within the capillary, which draw water back into the capillary due to their high solute concentration. Since these proteins are largely unable to leave the capillary, their osmotic pull is constant, promoting reabsorption
Explain how changes in net filtration pressure (NFP) can result in edema and how a functional lymphatic system normally prevents edema.
Edema occurs when there is an increase in net filtration pressure (NFP), causing excessive fluid to leak out of capillaries into the interstitial spaces, leading to tissue swelling; a healthy lymphatic system prevents edema by actively draining this excess fluid back into the bloodstream, maintaining fluid balance within tissues
This means that if not enough fluid is taken out by the capillaries, an edema can occur which the lymphatic system gets rid of the wastes that cause this fluid build up thus helping prevent edema.
