Circulatory System Giovannucci Block II Unit I

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What are the two portions of the circulatory system?: The cardiovascular system and the lymphatic system.
What does the cardiovascular system consist of?: Heart and blood vessels (arteries, veins and microvasculature)
What are the two circuits of the CV system?: The pulmonary and systemic or peripheral vascular circuit.
What does the lympahtic system consist of?: Lymphatic vessels, lymph nodes and other lymphatic organs.
What is the function of the lymphatic system?: To remove excess interstitial fluid from the extracellular space, filter it adn return it to the CV system.
What the primary composition of the heart? (cell type/lining): Cardiac muscle lined by endothelium.
What are the three layers of the heart?: Endocardium, Myocardium and Epicardium.
What forms the outer wall of the sac of the heart? What is it made of? What tissue type lines it?: The fibrous pericardium forms the outer wall of the sac and is made of fibroelestic connective tissue. Lined by simple squamous epithelium (mesothelium)
What forms the inner wall of the cardiac sac? What type of tissue lines this?: The Epicardium, lined by mesothelium (simple squamous epithelium)
What are the two layers of the internal/extenal lining of the sac? What lies in between them?: Serous layer fibrous pericardium is called parietal layer of serous pericardium.
Serous layer of epicardium is called visceral layer of serous pericardium. In between them lies the pericardial cavity.
Describe the endocardium. (What layer is it, what does it do?): The innermost layer that lines the chambers of the heart. It seperates the blood from the heart wall.
What are the 2 things the endocardium consists of?: 1) Endothelium (simple squamous epithelium with basal lamina)
2) Subendocardial CT (areolar connective tissue that contains purkinje fibers, nerves and adipose cells.
What lines all the internal structures like trabeculae carnae, chorda tendinae and valves?: Endocardium
Describe the myocardium.(What layer is it, what is it made of, and what does it do?): The middle and thickest layer that consists of cardiac muscle cells. These are in a layered structure that spirals around the heart to the apex. This arrangement helps to direct blood out of heart during contraction.
Describe the Epicardium.(What layer is it, what is it made of(2 layers), and what does it do?): The epicardium is the outermost layer of heart wall. It is thin compared to myocardium. It consists of 2 layers, the CT layer and the mesothelium.
What does the CT layer of the epicardium contain?: Adipose cells and named coronary blood vessels.
What tissue type is the mesothelium of the epicardium?: Simple squamous (Visceral layer of serous pericardium) (Outermost layer of heart wall)
What are intercalated discs?: Specialized cell junctions located at the end of cells that connect the adjacent cells.
What do T-Tubules contain?: Contains volatage dependent calcium channels.
What are the types of connections in the transverse and longitudinal portion of the intercalated discs?: Transverse portion
-Fascia adherens
-Macula adherens
Longitudinal portion
-Gap junctions (nexus)
What are the 3 components of the cardiac skeleton?: Annulus fibrosus, Fibrous trigones, and septum membranaceum.
Describe the cardiac skeleton.: Concentrations of dense irregular CT within the heart. Dense irregular CT with large round cartilage-like cells.
Where is the Annulus fibrosus located? What does it do?: The annulus fibrosis is rings of connective tissue around the openings of each valve in the heart. IT has two A-V valves and 2 semilunar valves. It holds valves open and maintains the shape of valves.
Describe the Fibrous Trigones. What important structure goes through it?: The Fibrous trigones is a triangular shaped CT area between the valves. There are left and right trigone and the right trigone is pierced by A-V bundle of His.
What is/where is the Septum membranaceum?: The septum membranaceum is CT extending downward from trigone into top of interventricular septum.
What are the 3 functions of the cardiac skeleton?: 1) Hold valves open and maintain the shape of valves
2) Point of insertion for cardiac muscle cells.
3) Insulation of atria from the ventricles.
Trace the path of the Cardiac conduction system.: Sino-atrial Node -> AV Node - > AV Bundle of HIs -> L&R Bundle branches -> Subendocardial plexus
Describe the sino-atrial node. WHere is it located? What is it innervated by?: Located at junciton of the superior vena cava with atria. These pacemaker cells fire about 70/min. They are innervated by sympathetic and parasympathetic nerves (these nerves modify the rate of depolarization but do NOT initiate the impulse)
Where is the AV Node located? What does it do?: The AV node is located in the lower right atria in atrial septum by tricuspid valve. It picks up the signal from the SA node and sends it to the AV bundle.
Where does the AV bundle of His go? What/where does it divide?: THe AV bundle of His leaves the AV node, pierces the right trigone and enters the ventricular septum. It divides into the left and right bundle branches in the superior portion of the septum.
Where do the left and right bundle branches go? What do they supply?: The left and right bundle branches travel down on each side of the interventricular septum to supply the appropriate ventricle.
What does the subendocardial plexus supply?: Each bundle branch supplies the impusle to each ventricle.
What do pacemaker cells do? What is their size?: Pacemaker cells are responsible for initiating contraction. They are smaller cells than normal cardiac myocytes.
What do follower cells do?: The follower cells pick up the depolarization wave via gap junctions and transfers to the normal atrial myocytes for contraciton wave to travel through the atrial wall.
What are purkinje fibers? Where are they located?: Purkinje fibers are modified cardiac muscle cells that start in the bundle branches and continue into the plexus.
Where does the impulse for the subendocardial plexus start?: The impulse starts at the apex of the heart and spreads upwards towards the base.
Where does contraction push the blood?: Contraction pushes blood towards the base of the heart where outflow tracts of ventricles are located.
How do pacemaker cells perform their task?: They are leaky cells with unstable resting membrane potential. The Na+ ions leak into cells cause depolarization wave.
What happens to follower cells if the S-A node is eliminated?: Typically the A-V node act as follower cells but when the S-A node is eliminated, the A-V node takes over as pacemaker action.
What are purkinje fibers specialized for?: Impulse conduction.
What do purkinje fiber cells look like?: They are large cells that are light staining due to greatly reduced numbers of myofibrils. They have a large perinuclear space but no T-tubules and a reduced sarcoplasmic reticululum. They have lots of gap junctions for impulse transfer to the next cell.
What are the 3 major types of blood vessels and what do they do?: 1) Arteries
- Carry blood away from the heart
-High pressure
2) Veins
-Carry blood back to the heart
-Low pressure
3) Capillaries
-Exchange of materials between blood and parenchyma.
What is the relation of lumen diameter, wall thickness and elastic tissue distribution in arties and veins?: Veins have a larger diameter, arteries have a thicker wall, and there is more elastic tissue in veins.
What are the 3 subgroups of arteries?: Elastic arteries, Muscular arteries, Arterioles.
What is the size of elastic arteries? What is their main purpose?: Elastic arteries are the largest conducting arteries. Their main purpose is to maintain blood pressure within vessels during diastole.
What are elastic arteries characterized by?: Elastic lamellae
What is the main purpose of muscular arteries? What is their size relative to elastic arteries and arterioles?: Muscular arteries are distributing arteries whose main function is to regulate flow to different regions of the body as needed. They are larger than arterioles but smaller than elastic arteries.
What are muscular arteries characterized by?: A thick muscular wall.
What are arterioles surrounded by and what is their function?: Arterioles are surrounded by 1-3 smooth muscle cells whose function is to regulate blood flow into the capillary bed.
What are the three components of the microvascular bed?: 1) Capillaries
- Thin walled for rapid exchange of materials with parenchyma
2) Central channel
- A preferential channel through the capillary bed.
3) Arterioles and venules.
What are the 3 types of veins?: Venules, Medium Veins and Large veins
What are venules?: Small veins that accompany arterioles.
What are medium veins? What do they accompany?: They are thin walled vessels that are compantion vessels to the muscular arteries.
What is greatly reduced on medium veins? Describe their lumen.: The tunica media and the thickness of the wall. Thier lumen is large and irregular.
What makes medium veins special?: Only vessels that contain valves.
What are large veins?: They are large, low pressure, thin-walled vessels that return blood to the heart.
What is the thickest portion of vein's walls?: THe adventitia is the thickest poriton of the wall.
What are the layers of the blood vessels from innermost to the outermost?: Tunica intima, Tunica media, Tunica adventitia.
What is the tunica intima lined by?: Endothelial lining - simple squamous
What is the tunica intima composed of from innermost to outer msot?: Endothelial lining, subendothelial CT, Internal elsatic lamina (porous elastic sheet)
What is the function of the tunica media? What sort of fibers and cells does it contain?: The tunica media is the middle layer and consists of smooth muscle cells that are helically oriented and function to reduce the size of the lumen. It also contains elastic and collagen fibers.
What does the tunica adventitia consist of? What seperates it from the tunica media?: The tunica adventitia consists of dense irregular CT. The external elastic lamina seperates the media from the adventitia.
What is the vaso vasorum? What layer is it found in?: The vaso vasorum are small vessels that supply the wall of the large blood vessels. It is found in the tunica adventitia.
Describe the T. Intima of elastic arteries.: Relatively thick portion of total wall, thin endothelium, the subendothelial CT is thickened and the internal elastic lamia is difficult to distinguish due to other elastic lamellae.
Describe the T. Media of elastic arteries.: Characterized by 40-70 layers of elastic sheets (diagnostic).
What are the layers of elastic sheets of T. Media of elastic arteris seperated by? What do these accomplish together?: Smooth muscle cells and collagen fibers. Together they maintain blood pressure within the vessel during diastole due to passive contraction fo elastic lamellae.
Describe the T. intima of muscular arteries.: Their endothlium and CT are hard to see. However they have a prominent scalloped IEL (diagnostic).
Describe the T. media of muscular arteries.: These are thick with 5-20 layers of smooth muscle cells (diagnostic). It also has some scattered elastic lamellae and fibers.
Describe the T. adventitia of elastic arteries.: These are relatively thin and are half the thickness of the mdia. They are composed of collagen and elastic fibers.
What do arteriole's look similar to?: Small muscular arteries.
What is unique about the T. intima of arterioles?: May or may not have IEL.
Describe the T. media of arterioles.: Only 1-3 layers of smooth muscle cells (diagnostic)
What does the T. adventitia of arterioles look like?: It is minimal in arterioles.
What feeds capillary beds?: Terminal arterioles.
What do arteriole's feed?: Either metarteriole or atriovenous shunt.
What is a central channel?: A more direct channel through the capillary bed.
What is a metarteriole?: The beginning poriton of the central channel.
What is the distribution of SMC in metarteriole's? What is its size in relation ot true capillaries? Where does it pour into?: Metarterioles have scattered smooth muscle cells. and are slightly larger than true capillaries. They open into and control blood flow into true capillaries.
What is a thoroughfare channel? Compare/contrast them with metarterioles.: The distal end of the central channel. Like metarterioles in size but do not have smooth muscle cells. They drain the true capillaries into venules.
What are arteriovenous shunts?: An alternate channel with a direct link between arteriole and venule without going thorugh capillaries.
What lines AV shunts?: 2-3 layers of smooth muscle cells.
What is the purpose of AV shunts?: To bypass around capillaries. They are usually employed to conserve heat.
What do capillaries consist of?: A tube of simple squamous epithelium.
What layer do capillaries lack?: No T. media
What cell types are in capillaries?: Pericytes (cells joined by tight junctions) and simple squamous
What are the 3 different types of capillaries?: Continuous, fenstrated and discontinuous.
Describe continuous capillaries. What are they connected by? Describe their basal lamina.: The continuous capillaries are most common in muscle, CT proper and gut. They have a thin cytoplasma and are connected by tight junctions (zonula occludens). Their basal lamina is continuous all around the endothelium.
Describe Fenstrated capillaries. Describe their basal lamina. Where are they located?: Fenestrated capillaries are single endothelial cells that have holes perforateing through the cytoplasm. They are bridged by diaphrams. The basal lamina is continuous all the way around. They are found in endocrine glands, intestinal villi, exocrine pancreas.
Whare are fenestrated capillaries found without diaphrams?: In renal glomeruli.
Describe discontinuous capillaries (sinusoids). What type of junctions do they have? Describe their basal lamina. Where are they located?: Discontinuous capillaries have a larger diameter, irregular shape (due to molding by surrounding tissue). They have large gaps between thick endothelial cells but tight junctions. They have a DIScontinuous basal lamina that does NOT cross gaps between cells. They are located in spleen, liver, bone marrow, and lymph nodes.
What are the 2 functions of capillaries?: Transport and secretion.
Describe endothelial cells. What is their cell type/shape?: Endothelial cells are simple squamous epithelium that are diamond shaped and thin and flat. They have nuclear bulges and marginal folds overlap on the upstream edge of the cell.
What are the 4 types of transport materials across cells?: Diffusion, transcytosis, receptor-mediated transport and direct channels formed from fused vesicles.
Describe diffusion.: Transport between cells.
Describe transcytosis.: Pinocytotic vesicles form adluminal to abluminal surface that are non selective and very numerous.
Describe receptor mediated transport.: Receptors on surface for specific molecules transport them into vesicles.
Are endothelial cells secretory cells?: YES!
What do the endothelial cells help to secrete? (4): 1)It helps to form the basal lamina so it so collagen adhesion molecules etc.
2) IT produces signals for extravasation and diapedesis (p-selectin, PAF, CAMs)
3) Substances that affect vascular tone (endothelin I - vasoconstrictor, prosta cyuclin, NO -vasodialator)
4)Produce clotting factors (VWF - found in Weibel Palade bodies in endothelial cells of arteries.
What are venules? What are they usually found with?: Venules are small vessels that collect the blood from the capillary beds. They are companion vessels to arterioles.
Compare venules to arterioles.: Venules- more irregular lumen, larger, thinner wall, no T. media, preferred place of exit for most WBCs.
What are medium sized veins usually found with?: Muscular arteries.
Compare muscular arteries and medium sized veins.: Medium sized veins - thinner wall, larger, and irregular shaped lumen.
Describe the T. intima of medium veins.: Thin endothelium
No well defined IEL
Describe the T. media of medium sized veins.: Relatively thin, few circularly oreinted SMCs.
Describe the T. Adventitia of Medium sized veins.: Often the thickes layer with no EEL.
What special structure do medium veins contain?: Valves.
What are valves? What are they made of?: Protrusions of the T. intima into the lumen of the vessel. The center portion consists of CT of T. intima and are coverd by endothelium on each side.
What are valve sinuses?: Dialation of wall behind leaflets.
What is the function of valves?: Prevent back pressure on capillaries and prevent back flow of blood in veins.
What are varicose veins?: Large tortuous veins on surface of legs. Caused by escess pressure in the veins. The hydrostatic pressure causes distension and dilatation of vessel walls. Leaflets can not meet in center to prevent backflow. This distension and dialation causes lengthening and toruou appearance.
What do large veins usually accompany?: Elastic arteries.
Compare elastic arteries and Large veins.: Large veins- No valves present, relatively thin wall, longitudinal-oriented SMC's in adventitia.
Describe the T. intima of Large veins.: Thin typical endothelium, no apparent IEL.
Describe the T. Media of Large veins.: Quite reduced in thickness. Few circularly oriented SMC's.
Describe the T. adventitia of large veins.: The thickes t layer of wall with bundles of longitudinally oriented SMC's (diganostic). The vaso vasorum peneterates the wall deeper in toward the lumen.
Describe the layout of the Lymphatic system.: Delicate, blind ended lymphatic capillaries drain nto larger vessels which take the fluid to lymph nodes for filtering prior to returning it to the blood vascular system.
What are the two major ducts of the the lymphatic system?: Left = thoracic duct
Right duct
Describe the thoracic duct. What does it drain into/drain?: Starts as cisterna chyli at the level of the diaphram. It drains 2/3 of the body. It empties into blood vascualr ssytem on the venous side and drains into the left subclavian vein where it joins with the left internal jugular veins.
What does the right duct drain/drain into?: The right duct drains the upper 1/3 of the body into the right subclavian vein.

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