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Chapter 21
Chapter 21
29
Physiology
Undergraduate 2
10/11/2012

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Term
Capillaries
Definition
microscopic vessels that usually connect arterioles and venues - permit exchange of nutrients and waste
-found near very cell in body
-distribution varies with metabolic activity in the tissue
Term
Structures that lack capillaries
Definition
cornea, lens, epithelium, and cartilage
Term
Microcirculation
Definition
flow of blood through capillaries - regulated by smooth muscle sphincters in the walls
Term
capillary walls
Definition
composed of single layer of cells (endothelium) and a basement membrane
Term
Capillary network throughout the tissues
Definition
increase surface area- allow rapid exchange of large quantities of materials
Term
Precapillary sphincters
Definition
rings of smooth muscle fibers that regulate blood flow through true capillaries
Term
3 types of capillaries
Definition
continuous, fenestrated, sinusoids
Term
Continuous capillaries
Definition
plasma membrane forms complete tube interrupted by small intercellular gaps - found in muscle and connective tissue
Term
Fenestrated capillaries
Definition
"window" plasma membrane has small pores - choirod plexus, villi, kidneys
Term
Sinusoids
Definition
large fenestrations and gaps in the basement membrane - red bone marrow, liver, and spleen
Term
Venules
Definition
little veins- formed from the union of several capillaries
-merge to form veins
-drain blood from capillaries
Term
Veins
Definition
consist of same three tunics as arteries- but thinner
-less elastic tissue and smooth muscles
-contain valves to prevent back flow of blood
Term
Vascular sinuses
Definition
veins with very thin walls with NO smooth muscle to alter their diameters - coronary sinus of the heart
Term
varicose veins
Definition
weak valves can lead to this- causes=congenital, standing, pregnancy, aging
Term
Arterial Anastomoses
Definition
union of branches of two or more arteries supplying the same region- alternate blood pathways to get to the same region - collateral route of blood (alternate)
Term
Neurosis
Definition
blockage in arteries that dont have anastomoses (end arteries) - arteries die
Term
Blood reservoirs
Definition
Largest portion of the blood is in systemic veins and venules (64%) - collectively called ___ - they store blood and can move it if the body needs it
Term
Capillary exchange
Definition
diffusion, transcytosis, bulk flow
Term
Diffusion
Definition
most important method of capillary exchange- 0c, C02, flucose, amino acids, hormones, and others diffuse down concentration gradient
-small proteins diffuse
-plasma solutes diffuse across capillary walls
-brain-blood-brain barrier exists
Term
Transyctosis
Definition
moves large lipid insoluble molecules across the capillary walls by enclosing substances within tiny vesicles that enter cells by endocytosis and exit by exocytosis -insulin
Term
Filtration
Definition
Out of the blood
Term
Reabsorption
Definition
Into the blood
Term
Bulk Flow
Definition
-interstitial fluid & blood --specific to capillary beds
passive flow of water and solutes in one direction driven by pressure (up pressure to down pressure)
-more important for determining the relative volumes in the blood stream and the interstitial fluid space
-dependent upon hydrostatic and osmotic pressure
Term
Starlings law of capillaries
Definition
balance between two filtration pressures of moving material out and bringing it back in
-hydrostatic pressures and osmotic pressures
Term
Capillary beds
Definition
between ateriole and venules - certain amount of fluid will filter out of the begining capillary and 85% of that fluid will be reabsorbed
Term
Blood flow
Definition
C.O./ min - mL/min
-how much of the cardiac output is distributed to a tissue depends on the interplay of the pressure differences that drives the blood flow and the resistance to blood flow through that tissue
Term
Blood pressure
Definition
is the pressure exerted on the walls of a blood vessel
Term
Factors that affect blood pressure
Definition
cardiac output=increase
blood volume=increase
viscosity=increase
resistance=increase
elasticity of arteries=maintains bp rather than increase
Term
Resistance
Definition
the opposition to blood flow as a result of friction between blood and the walls of blood vessels
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