a and p lecture 10 Flashcards
Structure of artires
- Thicker Tunica media (controlling blood pressure)
- Much more internal and external elastic laminae, under higher pressure
Three classes of each arteial wall depending on size and function
- elastic arteries
- muscular arteries
- Arterioles
Elastic Arteries (conducting)
largest in diameter, inculde aorta and immediat branches, nearest to heart. Highest pressure of any vessels
Muscular arteries (distributing)
Intermediate in diameter, well developed tunica media, mostly smooth muschles. Most smallar branches aorta, include mostly smallar artires supply organs
Pressure receptors (barorceptors)
In the aorta, and also in common carotid artery in the neck. Detect blood oxygen, CO2 and Hydrogen ion concentrations
Vein function
- outnumber arteries (70%) of the body is veins
- larger average diameter
- Function as blood resivars
- Thinner walls, fewer elastic fibers, less smooth muscles and larger lumens than artiers
Venules
smallest veins, drain blood from capillary beds
Tiny postcapillary venules
- Little more then endothelim, some surroundg connective tissie. Enables exchange material with surrounding intertalr fluif
Three tunics
More distinct when venules merge to become larger venules and then veins
Vein structure
- Thin tunica media with few smooth muscle cells, diameter changes only slightly with vasodilation and vasoconstriction
Veins contain
venioles valves, (extensions of the tunica intima) overlap and prevent blood from flowing backward in the venous circuit. High in leg veins where blood flow toward heart opposed by gravity
Capillary wall consist
endothelium ( simple squamous epithelium) basement membrane, layer of loose C.T. scatterd pericappilary cells
Pericapillary cells
Fibroblasts, macrophages, or undifferentiated smooth muscle cells
How does subastance move through capillaires
diffusion
Lipid-soluble and small water-soluble molcue
move through plasma membrain
Larger water-soluble molecules
pass through fenestrate gaps between endothelial cells
Continuous Capillaries
No gaps between endothelial cells, no fenestrate, and less permeable to large molecules than other capillary types. Ex. muscle, nervous tissue
Fenestrated Capillaries
Endothelial numerous fenestrate, cytoplasm is absent and plasma membrane is made of a thin pours diaphragm, highly permeable. Ex. Intestinal villi, the ciliary process of the eye, choroid plexus
Sinusoidal
Large diameter with large fenestrate, less basement membrane. Ex. Endocrine glands (large molecules cross walls)
Sinusoids
Large diameter sinusoidal capillaries, sparse basement membrane. Ex. Liver, bone marroe
Venous sinuses
Similar in structure to sinusoids but even larger. Ex. Spleen
Capillary network
- blood flows through metarterioles > through capillary network > flow through thoroughfare channel ( consistant ehile flow though arterial cappilaries is intemintant
Precapillary sphincters
smooth muscle in arterioles, metartiols that regulate blood flow
Arteriovenous anastomoses
Vascular connections that allow blood to flow directly from arterioles to small veins (skipping capillaries)
Glomus
arteriovenous anastomosis with abundant smooth
muscle in walls; abundant in sole of foot, palm of hand,
terminal phalanges, nail beds; help regulate body temp by
adjusting blood flow through them
Neural innervation
- unmyelinated sympathetic nerve fibers form plexi in tunica adventitia: vasoconstriction
- small artires and areoles inverted
- vessels of penis and clitoris inverted by parasympathetic
- some blood vessels inverted by myelinated fibers and act as baroreceptors that monitor stretch ad detect changes in bp
arteriosclerosis
degenerative changes in arteries make them less elastic
atherosclerosis
Deposition of plaque on walls
Interrelationships between _____ is the dynamics of blood circulation
Flow, resistance, pressure
Flow, resistance and pressure
Control mechanisms that regulate bp and bf
Laminar flow
Streamlined, the interior of B V is smooth and equal in diameter along length, outermost area moving slowest and the center moving fastest
Turbulent flow
Interrupted, rate of flow exceeds critical velocity; fluid passes a constriction, sharp turn, rough surface; partially responsible heart sounds; increases probability of thrombosis
Blood Pressure (BP)
measure of force exerted by blood against the wall
How is blood pressure measured directly
Using cannula into B V
How is B P measured indirectly
Using auscultatory method
Auscultory method
Sphygmomanometer and stethoscope ( at dr office) Korotkoff sounds
Pressure during first sound
Systolic
Pressure where sound disappears
Diastolic
Blood flow equation
Flow=(P1 -P2/R)
What is P1 and P2
Pressures in the vessel at points of one and two
What is R
R is the resistance to flow
Blood flow
Directly proportional to pressure differences, inversely proportional to resistance
Resistance equation
Resistance = 128 (vl)/piD^4)
What is V in resistance equation
Viscosity
What is l in resistance equation
length of vessel
What is D in resistance equation
Diameter of the vessel
Poiseuille’s Law
Flow decreases when resistance increases and vice versa. resistance proportional to blood vessel diameter, constriction of a BV increases resistance thus decreases flow
Flow equation
Flow = ((P1-P2)/R) = (pi (P1-P2)D^4)/128vl)
What happens during exersise
Heart beats with greater force increasing pressure in the aorta. Cappilaries to skeletal muscles increase in diameter decreasing resistance and increasing flow
Increased flow aorta
It can go from 5L/min to 5 times that amount
Viscosity
Measure of resistance of liquid to flow, resistance is proportionate to flow
Increase in viscosity
Increases the pressure required to flow
What is viscosity influenced by
Hematocrit
Hematocrit
Percentage of the total BV composed of red blood cells
What leads to increased viscosity
Dehydration and or uncontrolled production of RBC. Also increases workload on the heart
Critical closing pressure
Pressure at which a BV collapses and BF stops
Laplaces law
Force acting on BV wall is proportional to the diameter of the vessel times the BP
Laplaces law equation
F= D * P; as diameter of vessel increases force on wall increases
Aneurysm
Weekend part of the Vessel wall bulges out
Compliance
increase in volume/ increase in pressure
Vascular Compliamce
Tendency for BV volume to increase as BP increases
The more easly vessel wall streaches
greater its compliance
Venous system
Has large compliance (24 times greater than that of arteries) and acts as a blood reservoir
Physiology of Systematic Circulation
Cross sectional area
Cross-sectional area
- Diameter of vessel decreases total cross-sectional area increases, velocity of BF decreases
-Like a stream flows rapidly through narrow gorge but slowly through a broad plane
-one aorta with cross cross-sectional area of 5cm^2. Total cross-sectional area of millions of capillaries is 2500 cm^2
Blood Pressure average
- 100mm HG in the aorta and then drops to 0mm Hg by time blood gets to the right atrium. due to increased resistance to flow as cross-sectional area increases
Where is the greatest drop in pressure
In arterioles, regulate BF through tissues
Pulse Pressure
Difference between systolic and diastolic pressure
When does PP increase/decrease
Increases when stroke volume increases or vascular compliance decreases. Compliance tends decrease with age
Pulse Pressure (PP) used
Take a pulse and determine heart rate and rhythmicity
