EXAM 2 Starts: Circulatory System Flashcards
what is the primary function of the circulatory system
transport of O2, CO2 and nutrients/ metabolic waste
what are the secondary functions of the circulatory system
thermoregulation, transport of immune cells/hormones
what does the blood vascular system consist of
heart and blood vessels
what are the two components of the circulatory system
pulmonary circulation and systemic circulation
what is pulmonary circulation
RA -> RV ->pulmonary artery -> lungs -> pulmonary veins -> LA
what is the systemic circulation
LA -> LV -> aorta -> rest of body
what is the lymph vascular system
passive drainage system for returning extravascular fluid (lymph) to blood vascular system
what does the lymph vascular system rely on and why
muscle contractions and body movement because it lacks an intrinsic pump
what are vascular tunics
blood vessels of the circulatory system have common basic structure with 3 concentric layers
what are the 3 vascular tunics from innermost to outermost
- tunia intimia
-tunica media - tunia adeventitia
what is the tunica intima, what type of epithelia, and how thick
innermost layer of simple squamous endothelial cells lining the lumen. very thin 1-2 cells thick
what is the function of the tunica intima
forms a semi-permeable barrier supported by the basement membrane
what are the tight junctions between endothelial cells in the tunica intima called
fascia occludens
what supports the tunica intima
subendothelial connective tissue
where is the internal elastic lamina
separates the tunica intima from the tunica media
what is the internal elastic lamina made of
elastic fibers arranged in an sin wave pattern
what is the tunica media
middle layer made of smooth muscle and fibroblastic connective tissue
what is the thickest layer in arteries and what do arteries contain
tunica media
- may contain reticulin (type 3 collagen) and elastic fibers
where is the external elastic lamina located
between tunica media and adventitia
what is the external elastic lamina composed of
elastic fibers but less organized than internal elastic lamina
what is the tunica adventitia and what does it contain
outermost layer made of loose fibroblastic CT, fibroblasts, collagen, elastic fibers and smooth muscle cells
what is the thinner layer in the arteries
tunica adventitia
what is the thickest layer in veins
tunica adventitia
what are vasa vasorum and where are they located
they are small blood vessels that supply the tunica media and adventitia in both large arteries and veins
what are nervi vasculares and where are they found
autonomic nerves that control smooth muscle contraction in vessel walls in the tunica media
what is vasoconstriction due to
action of sympathetic, post-ganglionic nerve fibers
what happens in vasoconstriction
acts on smooth muscle of tunica media to cause vasoconstriction and decrease lumen diameter
what are the different mechanisms of vasodilation
- passive; occurs in absence or inhibition of sympathetic stimulation
-accomplished via indirect parasympathetic innervation (Ach causes endothelial cells to release NO which causes smooth muscle cells to relax - in response to low O2 tension, smooth muscle in walls of arterioles relaxes
where are baroreceptors and chemoreceptors found
in walls of blood vessels
what do baroreceptors do and where are they located
detect BP located in carotid sinus and aortic arch
what do chemoreceptors do and where are they located
they detect changes in O2, CO2, tension and pH and are located at bifurcation of carotid arteries and in aortic bodies in aortic arch
what are the functions of the arterial system
-conducts blood away from heart to capillary bed
- venous system returns blood from capillaries to heart
what is pulsatile blood flow
cyclical pumping of heart
what is systole
contraction of ventricles
what is diastole
decrease in pressure
what do the expansion and recoil of elastic arteries do
maintain BP
what controls the diameter of blood vessels
sympathetic control of smooth muscle in vessel walls
what do arteries contain and describe their wall
large amounts of elastin and smooth muscle, thick wall relative to lumen diameter
describe elastic arteries and give examples
-large, conducting vessels that receive blood directly from the heart (ex:aorta, common carotid, subclavian, pulmonary artery)
- sheets of elastic tissue in tunica media to maintain BP
-thickest layer
what layers do elastic arteries have
tunica intima, media, and adventitia and internal and external elastic lamina
describe muscular arteries
medium sized
- have more smooth muscle and less elastin in tunica media than elastic arteries
what layers do muscular arteries have and what layer is the thickest
tunica media, intima, and adventitia and distinct internal elastic lamina. larger muscular arteries may also contain external elastic lamina
- thickest: tunica media
describe arterioles
-smallest
- little smooth muscle
-elastic laminae are absent
what are arterioles
terminal branches of arterial system that supply capillary beds
- major sites of vasoconstriction and vasodilation
what is the function of arterioles
regulate distribution of blood to capillaries via pre-capillary sphincters
how do arterioles regulate distribution of blood to capillaries
pre-capillary sphincters
what are pre-capillary sphincters
intermittent rings of smooth muscle within walls of arterioles
what are metarterioles
small diameter arterioles; intermediate in size between arterioles and capillaries
what are metarterioles characterized by
discontinuous layer of smooth muscle in tunica media
what accompanies an increased amount of smooth muscle
increased diameter of vessel and decreased amount of CT
what does microcirculation do
exchange of gases, fluids, nutrients, metabolites, and waste products
where does microcirculation occur
within capillaries but also includes arterioles and venules
what are capillaries
thin walled vessels 8-10 micrometers in diameter
what are capillaries lined with
a thin single layer of endothelial cells supported by basal lamina and small number of pericytes
what are pericytes
contractile, precursor for endothelial cells and can become smooth muscle cells
what are pericytes derived from
the same precursor as endothelial cells
what do capillaries lack
tunica adventitia (no outer CT layer), tunica media (no smooth muscle)
how do vasodilation and vasoconstriction occur in capillaries
smooth muscle contraction in arterioles and pre-capillary sphincters which result in passive changes in capillary diameter
what are continuous capillaries and where are they found
endothelium forms continuous lining. found in muscle, lung CNS
what are fenestrated capillaries and where are they found
endothelial cells possess pores or fenestrae within cells. found in endocrine glands and GI tract
what are discontinuous capillaries and where are they found
basal lamina not continuous; endothelial cells separated by large gaps between cells. can form sinusoids. found in liver, spleen, bone marrow
how does transport across capillaries occur
via fenestrae, transcytosis or diapedesis
what does the venous system function as
low pressure collecting systtem returning blood from capillary beds to the heart
describe veins
thinner walled vessels with larger lumen than arteries
describe the tunica media in veins compared to arteries
fewer layers of smooth muscle in tunica media than arteries
what is the thickest tunic in veins
tunica adventitia
where are valves located and what do they do
in veins they prevent backflow, especially in limbs and thorax
what are varicose veins
valve failure in legs
what are venules and describe them
small veins, lack elastic laminae and smaller venules may lack tunica media
what are post capillary venules and where are they located
located after capillaries and tunica media and adventitia are reduced or absent
what do post capillary venules do
-site for diapedesis
- drain into large collecting venules then muscular venules
describe muscular venules
thin smooth muscle layer in tunica media, thicker tunia adventitia
what are examples of vasoactive substances and what do they do
histamine or serotonin and they act on venules to enlarge intercellular spaces and increase the permeability of the vessel
what are muscular veins
large and medium sized veins
describe small muscular veins
may or may not contain internal elastic laminal and does not have external elastic lamina
describe medium muscular veins
contain internal elastic lamina only
describe large muscular veins
contain internal and external elastic laminae
what controls the lumen diameter of muscular veins and venules
smooth muscle in tunica media
what do AV shunts do
direct connections between arterial and venous system to bypass a capillary bed
what are AV shunts and where are they located
type of anastomosis; common in skin, function in thermoregulation
what are portal vessels and give examples
vein or artery directly connecting two capillary beds
ex: hepatic portal vein, venous portal system
what is atherosclerosis
when endothelium of vessel damaged, cholesterol adheres to exposed proteins
what are the steps in atherosclerosis
-when endothelium of vessel is damaged, cholesterol adheres to exposed proteins
- once endothelium heals, cholesterol patch reabsorbed
- phagocytosis by macrophages and later by foam cells
- if inflammatory response becomes chronic -> atherosclerosis and plaque formation
what are foam cells
endothelial and subintimal cells
what is atherosclerosis later accompanied by
smooth muscle cells and formation of fibrous CT capsule
what happens when cells within the atherosclerotic plaque die
necrosis and calcification
why is atherosclerosis often associated with hypertension
from decrease in lumen diameter and increase in systolic BP
what is the most common cause of ischemic heart disease
atherosclerosis
what happens with coronary artery in ischemic heart disease
coronary artery lumen may be decreased by 90%
what is stenosis
gradual narrowing by plaque
what is thrombosis
occlusion of vessel
what happens as plaque enlarges or if endothelium is damaged in atherosclerosis
underlying collagen is exposed
what is the series of events of atherosclerosis
-plaque formation
- initiates clotting cascade which forms a thrombus
- if a piece of thrombus breaks off it becomes an embolus
- occlusion by an embolus is an acute ischemic event
what does sudden occlusion of an artery cause
decrease in O2 to the heart and thus chest pain
what happens in myocardial infarction
portion of muscle dies in heart as a result of occlusion
how does healing occur in the heart
fibrosis
why does the repair of heart muscle after ischemic attack still result in decreased or partial loss of function
because CT is less contractile than muscle
what is endocarditis
inflammation and thickening of AV valves often associated with valvular incompetence
what is valvular incompetence
increased turbulence, regurgitation which results in vegetative endocarditis and thromboembolic disease
what is a stroke
blood clot in the brain
what does a cerebral infarct result in
cell death and loss of function
what determines the symptoms and severity of a stroke
the location of the clot
what are aneurisms
blood vessels dilate to form thin-walled, balloon like regions that commonly burst
where are aneurisms common
aorta or brain
describe the lymph vascular system
structurally similar to veins, but endothelial cells are thinner and have greater permeability
- thin tunica media
- valves present
- BM and pericytes may or may not be present
what do lymph endothelial cells do
active in phagocytosis
what is the function of the lymph vascular system
drain excess fluid from ECS and return it to the blood stream
what is lymph formed as a result of
high hydrostatic pressure in arterioles;exceeds colloidal oncotic pressure exterted by plasma proteins which results in the leakage of water, electrolytes, and plasma proteins from capillaries into ECS
what is lymph high in
proteins
where do lymphatic vessels converge
thoracic duct and right lymphatic ducts
where does lymph return to the bloodstream
at the junction of the left internal jugular vein and left subclavian vein
how is lymph moved
skeletal muscle contraction and body movement
what can immobility lead to
peripheral edema
where are lymph nodes located
interspersed along lymph vessels
what tunics do lymph vessels contain
tunica media
what do lymph nodes contain
lymphoid tissue for antigenic sampling and recognition, activation of immune cells and production of anitbodies
how do tumors metastasize
asymmetrical lymph drainage
how do you identify lymph vessels
thin walled, lack blood, contain smooth eosinophilic, proteinaceous fluid, occasional WBCs
what happens in elephantiasis
pericytes set up in lymphatics to restrict lymph flow from peripheral tissues
