The cardiovascular system is the transport system that carries blood and lymph to and from the tissues of the body. What are its components?
hear, blood vessels, and lymphatic vessels
In the capillary beds, there is two directional exchange of fluid called ____ ____ where oxygen, CO2, metabolites, and waste are exchanged.
Describe the pattern of lymph drainage.
Fluid that escapes from the capillary bed goes into lymph capillaries and is returned to the blood by coursing into larger and larger lymphatic vessels that evetullay drain into veins of the neck.
What vessels do WBCs leave circulation to go into tissues?
True or false: Each organ has a patterns or blueprint for blood flow which is characteristic for that organ. (liver, spleen, kidney, etc.)
What is the composition and function of the fibrous skeleton of the heart?
It is composed of dense irregular CT. It provides attachment sites for the leaflet of all four valves of the heart (aortic, pulmonic, tricuspid, mitral). Also provides attachment for the myocardium. Extends into the membranous portion of the interventricular septum where it lies adjacent to a portion of the conduction system. Also acts as an electrical insulator by preventing flow of electrical impulses btwn atria and ventricles.
What is included in the impulse conduction system of the heart? What are these parts made of? What are they controlled by?
1. made up of the SA node, AV node, bundle of His, right and left bundle branches, Purkinje fibers
2. highly specialized cardiac muscle cells NOT NERVE CELLS!
3. regulated by the autonomic nervous system
What are the 3 layers of the heart and what are their compositions?
From outside in: epidcardium, myocardium, endocardium
epicardium: outermost layer of mesothelial cells (simple squamous epithelium), small amount of CT, blood vessels (coronary arteries for example), nerves, fat
myocardium: cardiac muscle and accompanying CT, specialized fibrous skeleton in certain locations
endocardium: fibroelastic CT in a loose arrangement, impulse conduction system elements (in certain locations), innermost layer is endothelium (simple squamous epithelium) facing the lumen of each chamber and covering the valves as well, may include bundles of Purkinje fibers
True or false: The contraction of cardiac muscle is vigorous, rhythmic, and under the contol of both the ANS and circulating hormonse. The structrual arrangment of intercalated discs allows the heart to contract in a wringing fashion.
What is the flow of blood through the varying sizes of arteries and veins?
Blood flows from the heart into large (elastic) arteries that lead to muscular (distributing) arteries and then to arterioles. Capillary beds vary in permeability and have some specializations for exchange properties. Blood enters the venous side by passing into venules (also sites for exchange) and then into veins of increasing size.
What are the 3 layers/tunics of vessels?
What is located in the tunica intima, tunica media, and tunica adventicia?
tunica intima: endothelium linging with its basal lamina. Adjacent, a subendothelial layer consisting of loose CT. In arteries and arterioles, there is also an internal elastic lamina which is a sheetlike lamina of fenestrated elastic membrane.
tunica media: Contains circumferentially arranged smooth muscle cells. Also contains collagen, elastin, reticular fibers (type III collagen) and proteoglycans interwoven with the smooth muscle. Arteries have organized layers of elastic fibers in the tunica media. The fenestrations in these sheets of elastic allow for passage of molecules and can house bundles of smooth muscle interwoven within this layer. The boundaries of the tunica media in an artery extend from the internal elastic membrane to the exernal elastic membrane. This layer is larger in arteries than in veins.
tunica adventicia: longitudinally arranged collagenous tissue with elastic fibers. These CT elements wil erge with the CT surrounding the vessel. In large vessels, this layer contains the vasa vasorum (vessels contained within the wall of a vessel) and nervi vascularis (nerve fibers in the wall of a vessel). In veins, this layer is thicker than the companion artery and in large veins, smooth muscle may be present in this layer.
What are the types of vessels?
What are some features of large elastic arteries? Name one example in the body.
Aorta is a large elastic artery.
-relativley thick tunica intima
-thick tunica media with prominent elastic laminae
-tunica adventitia with vasa vasorum and nervi vascularis
please see pg 85 of course notes for another pic
What are some features of muscular arteries? Where are they found in the body?
Most arteries are muscular arteries.
-thinner tunica intima (than elastic arteries)
-prominent internal elastic lamina
-thick tunica media
-external elastic lamina (sometimes visible)
What are some features of arterioles?
Arterioles regulate flow to capillary beds.
-have only 1-2 layers of smooth muscle in the tunica media
-very thin tunica intima
-no internal elastic lamina
-thin tunica adventicia
see pg 87 of course notes for another pic
What are features of capillaries?
-lumen is typcially 8-12 micrometers in diameter and permits only a single RVC to maneuver through the lumen at a time
-vessel wall is a simple tube comprised of endothelium and basal lamina (tunica intima)
-may have a tunica media comprised of a pericyte
What is a pericyte?
- CT cell that is similar to mesenchymal cells
- surrouds capillary endothelium within the basal lamina providing physical stability
- has contractile ability
- participates in physical and chemical signaling within the endothelium
- may give rise to endothelial cells and smooth muscle cels during wound healing (angiogenesis)
What are the 3 types of capillaries and where in the body are they typically found?
1. continuous capillary: fat, muscle, lung, nervous system (CNS)
2. fenestrated capillary: intestinal vili, endocrine glands, kidney glomeruli
3. discontinuous/sinusoidal: liver, bone marrow, spleen
What are the features of continuous capillaries?
- numerous pinocytic vesicles
- tight junctions
- located in muscle, lung, CNS, fat
What are features of fenestrated capillaries?
- less pinocytic veislces than continuous (bc have fenstrations)
- may have diaphragms across fenestrations
- locations include endocrine glands, GI tract, kidney glomeruli
What are features of sinusoidal capillaries?
- large diameter lumen
- spaces btwn endothelial cells
- incomplete basal lamina
- locations include spleen, liver, bone marrow
How is the flow through microvessels controlled? What is the effect of vasodilating agents on aterioles and what effect does this have on capillaries?
Flow through the microvessel network is under local and systemic control. Arterioles respond to vasodilating agents (NO, O2) by relaxation of smooth muscle and results in increased flow. This increased pressure within the capillary drives plasma into the surrounding tissue resulting in edema.
How is blood flow to capillaries locally controlled as it pertains to AV shunts and metarterioles? Why may AV shunts be used?
Arteriovenous anastamosis (shunt) is a communication btwn an artery and a vein. Allows blood to bypass capillary circulation. Serves as function of phasic activity of an organ. When active, AV shunts are close and blood circulates through capillaries and are open when organ is inactive in order to bypass the capillary bed. Also used for temperature regulation in shunting heat away from skin to conserve for organs.
Metarterioles are preferential thoroughfares (way or place for passage, main road) in capillary beds. Smooth muscle sphincters called capillary sphincters are located on the origin of capillaires coming off of metarterioles. Blood flow to capillaries is controlled by these sphincters.
What are features of veins?
Have walls with tunics but layers are not as distinct or as well defined as arteries. When compared to accompanying arteries, veins have the following features:
- veins have a larger lumen
- have thinner walls (much less t. media)
- often are irregular or collasped
Capillaries--->post-capillary venules--->venules--->small/medium veins---> large veins---> heart
What is the fxn and composition of post-capillary venules? What chemicals act here and what are their effects? What process occurs here? What are the features?
- receive blood from capillaires
- endothelium is the site of action for histamine and serotonin which results in:
- 1. exit of fluids into tissue from these vessels
- 2. extravasation of WBCs into tissue from these vessels
- in lymph nodes, post-capillary venles are the sites of migration of lymphocytes
- lumen is 10-15 micrometers in diameter
- wall is a simple endothelial tube-T. initma
- may have a T. media comprised of a pericyte (no smooth muscle)
What are the features of venules?
- lumen up to 100 micrometers in diameter
- very thin wall-t. intima
- no smooth muscle (no T. media)
- look like dilated capillaries, T. adventicia blends in
What are features of small to medium veins? (note that most veins are of this type)
- lumen diameter up to 10 mm
- T. media has smooth muscle, elastic and collagen fibers
- T. adventicia is thicker than the media and has network of collagen and elastic fibers. blends in with surrounding CT.
What are features of large veins? What are some examples?
Examples include subclavian veins, portal vein, vena cava
- T. intima as endothelium and subendothelial CT with internal elastic lamina
- T. media has circumfirential smooth muscle, collage, fibroblasts. thin relative to lumen size
- T. adventicia is the thickest tunic-has collagen, elastic fibers, fibroblasts and bundles of longitudinally oriented smooth muscle fibers
please see pg 97 of notes for another pic
Lymphatic vessels convey a fluid called lymph throughout the body. Lymphatic circulation is a unidirectional system-from the tissues back to the blood vascular system and typically have valves to aid in the direction of flow. The walls resemble veins and lack a distinct separation twn the 3 tunics. Endothelium lines this system throughout. Most lymphatic vessels are associated with lymph nodes. What types of vessels does it consist of? What are the largest lymphatic vessels?
1. lymphatic capillaries, including lacteals
2. lymphatic vessels-small to large
largest lymphatic vessels are the right lymphatic trunk and the thoracic duct
What are features of lymphatic capillaries? Where are they found and what is their fxn?
Lymphatic capillaries are most numerous in loose CT under the epithelium of skin and mucous membranes. (respiratory, GI tract). Permeable and are effective (given these locations) in conveying protein rich fluid. Are also interspersed in capillary beds.
-simple endothelial tubes
-have anchoring filaments (contain elastic fibers)
-have discontinuous basal lamina
Where are lacteals found and what is their fxn?
In the villi of the small intestine, lacteals convey proteins and lipids that are too large to cross fenestrations of the blood capillaries.
What are the features of small to medium lymphatic vessels?
- simple endothelial tubes
- have anchoring filaments (contain elastic fibers)
- may have valves
What are features of the thoracic duct? Where does it empty its contents? How does it compare to veins?
Empties contents into venous circulation at the base of the neck. Compared to veins of similar diameter, the thoracic duct (which is 4-6 mm) have thinner walls overall and indistinct separation btwn tunics. T. media has both circular and longitudinal bundles of smooth muscle and T. adventicia has scattered smooth muscle.
What are the characteristics of endothelial cells in vessels? What specialized organelle do they contain and what is its purpose? What disease can result if there are issues with this organelle?
- are elongated parallel to the direction of blood flow
- have junctions to adjacent cells (zonula occludens/tight junctions, zonula adherens/adhering junctions, macula adherens/desmosomes)
- anchored to basal lamina via hemidesmosomes
- contained the specialized oorganelle: Weibel-Palade body. Weibel-Palade bodies contain von Willebrand factor which plays and important role in blood coagulation. Deficiency results in von Willebrand Disease. please see pg 101 of course notes for pic
What are the properties and fxns of the endothelium? What is endothelial activation?
Endothelial activation is the term collectively used to describe the multiple processes and fxns of the endothelium.
These cells can:
- respond to stimuli (bacterial and viral antigens, lipid products, hypoxia, cytotoxins)
- maintain selective permeability barrier
- maintain non-thrombogenic barriers btwn platelets and subendothelial tissue
- modulate blood flow and vascular resistance
- regulation of cell growth (secretes growth factors)
- modulate immune responses
- maintains ECM (basal lamina, glycocalyx)
- inactivates/converts compounds in the blood (Angiotensin I to Angiotensin II)
- modification of lipoproteins
Endothelial activation is also responsible for the pathogenesis of any vascular diseases.
a weakening in the vessel wall that is usually related to the T. media layer and a specific defect in collagen
ischemic heart disease
usually caused by coronary artery obstruction with diminished blood flow to the myocardium. may result in angina pain and possible MI
backflow of blood from deep veins into superficial veins due to fault valves. results in dilated veins-alteraltion in the vessel wall and valvular incompetence in veins
Transplanted heart: dennervated organ-no ANS innervation to modulate and coordinate the organ with the environment. Immune response-cellular rxn?
What is atherosclerosis? What are the processes that lead to it? What diseases may result?
Atherosclerosis is a very common lesion of blood vessels wherein deposits of plaques (atheromas) are present in the intima of large and medium sized arteries. Blockage or obstruction of flow is likely a related problem. Lesions develop in the T. intima and consist of a thick layer of fibrous CT containing macrophages, foam cells, lymphocytes, and cell debris. Depending upon location of vessel, can lead to variety of pathologic conditions including MI, CVA, gangrene of limbs.
How it happens:
High levels of lipid inteh blood produce a cascade of events. Endothelial cells initiate monocyte migration. Platelet-derived growth factor (PDGF) and other growth factors stimulate migration of smooth muscle cells into the T. intima. Macrophages and smooth muscle cells accumulate LDLs forming foam cells. Thickening of T. intima with roughened surface of vessel lumen can be called a plaque.