Chapter 11 - Circulatory System Flashcards
Function of the circulatory system
- propels blood to all tissues/organs of the body - heart and blood vessels
- returns tissue fluid to the blood through lymphatic vessles to reach fluid homeostasis
What are the types of tissues present?
- squamous epithelium - endothelium
- connective tissue
- smooth muscle
- blood cells
Fluid movement in the tissues
- fluid moves into tissues from capillary beds
- most returns to circulatory system via lymphatic vessels
Microvasculature vs. microvasculature
- macro - elastic, muscle arteries, muscular veins, large arterioles
- micro - arterioles, capillaries, venules
General properties of Capillaries
- only have tunica intima
- adapted for ga/metabolite exchange - transport occurs by diffusion, pinocytosis, movement of molecules/cells through intercellular clefts of fenestrations
- RBCs pass through one at a time
- several diff types of capillaries to permit diff levels of exchange with the surrounding tissue
Continuous capillaries
tightest
skin, muscle, lung, CNS
continuous basal lamina
tight junctions
Fenestrated capillaries
middle level of tightness
have pored called fenestrations - allow for greater permeability than continuous capillaries
found wherever active capillary absorption occurs or filtrate formation takes place
kidneys, small intestines, endocrine
Sinusoidal capillaries
greatest permability
incomplete basal lamina and large fenestrations
leaky - proteins and cells can pass through
liver, spleen, lymph nodes, bone marrow, adrenal glands
All blood vessels have 3 layers, except which kind? What are those three layers?
- capillaries only have two
- tunica intima
- tunica media
- tunica adventitia
Tunica intima
innermost layer, in direct contact w/ blood
endothelium composed of squamous epithelium
basal lamina underlies endothelium in vessels >1 mm indiameter
Tunica media
middle layer
circular layer made of smooth muscle (the larger the vessel, the more smooth muscle)
collagen and elastic fibers encircle the vessel lumen (larger vessels will have more)
Tunica adventitia
outermost layer of CT
collagen fibers that are oriented longitudinally
elastic fibers
in very large vessels, may contain small blood vessels
What are lumen?
interior of vessels
What are the different types of arteries?
- carry blood away from the heart
- elastic arteries, muscular arteries, arterioles
Elastic arteries
conducting arteries - those that are nearest the heart are thick walled (aorta)
extensive elastic fibers in tunic media that withstand and smooth out large pressure changes
in charge of blood pressure as the ventricle squeezes and relaxes
some of the largest lumens
Muscular arteries
internal elastic lamina is a hallmark of these
distribution arteries
more smooth muscle in tunica media than elastic arteries
prominent internal elastic lamina at innermost part of tunica media
Arterioles
regulate blood flow to capillary beds
precapillary sphincters at the junction of arterioles with capillary beds (contraction/relaxation is regulated by vasoconstrictors/dilators)
have anywhere from 1-3 layers
relatively thin tunica adventitia
in general, smooth muscle tone is very important to regulate blood pressure
Veins
return blood to the heart
not as much elastic tissue or muscle - low pressure and low resistance
volume reservoirs - 60-70% of blood volume is in the venous system
typically have thinner walls and larger lumens
adventitia is thicker in veins than arteries, is the most developed tunic in veins
relative thin tunica media - lumen may appear collapsed
Venules
formed when capillary beds unite
consists of endothelium surrounded by pericytes (minimal tunica adventitia)
larger venules have 1-2 layers of smooth muscle (tunica media)
Hypertension
long term, elevated BP is a risk factor for stroke
BP setpoint determined by smooth muscle tone in arterioles
also influenced by atherosclerosis
Atherosclerosis
accumulation of fatty deposits in tunica media of arteries, proliferation of smooth muscle in tunica media also occurs
normal part of aging
occurs more frequently in persons w elevated cholesterol and plasma lipids
most dangerous when plaques form in coronary and carotid arteries
increases platelet aggregation
gradual occlusion of artiers
aspirin and Plavix decreased formation by decreasing platelet aggregation
What occurs during atherosclerosis?
1- ciruclating monocytes take up lipids, then are called foam cells
2- foam cells adhere to tunica intima and release growth factors
- stimulates further lipid uptake and proliferation of smooth muscle in tunica media that creates plaque
- endothelial cells also take up lipids
- creates abnormality in wall, alerting platelets
Arteriosclerosis
hardening of arteries that occurs when fatty deposits become calcified (atherosclerosis)
as it progresses, smooth muscle in tunica media begins to die and elastic fibers are degraded, replaced by scar tissue
calcium salts accumulate at the site
arteries become rigid
increased risk for MI, stroke, aneurysms
Marfan syndrome
- FBN-1 mutations affect fibrillin, a component of elastic fibers
elastic fibers important in structure/function of large arteries
defective elastic fibers = dissection of large arteries
Lymphatic vessels
thin walled channels that conduct tissue fluid to venous system - thinner than veins
one way
lymphatic capillaries, vessels, and trunks
Lymphatic capillaries
very similar to blood capillaries
transport lymph to even larger lymphatic vessels that empty into the thoracic R lymphatic duct
these then empty into the L and R subclavian veins
Lymphatic vessels
very similar to veins but with thinner walls, also have valves
