AP II Lab Exam 2 Flashcards
Blood vessels
Delivery system of dynamic structures that begins & ends at heart
Arteries
Carry blood away from heart
Oxygenated (EXCEPT for pulmonary circulation & umbilical vessels)
Capillaries
Microscopic vessels
Diameters so small only 1 RBC can pass through lumen at a time (single file)
Direct contact with tissue cells
Directly serve cellular needs (gas & nutrient/waste exchange)
Veins
Carry blood toward heart
Deoxygenated (EXCEPT pulmonary circulation & umbilical vessels)
Elastic arteries
“Conducting arteries”: conduct blood from heart to medium sized vessels
Thick-walled
Large + low-resistance lumen
Includes:
Aorta & major branches
Muscular arteries
“Distributing arteries”: deliver blood to body organs
Thickest tunica media (more smooth muscle)
Active vasoconstriction
Arterioles
“Resistance arteries”: change diameters to change resistance to blood flow
Smallest arteries
Control flow into capillary beds via vasodilation & vasoconstriction (smooth muscle)
Continuous capillaries
Least permeable (tight junctions) & most common
Pinocytotic vesicles ferry fluid across endothelial cell
Found in:
Skin
Muscles
Lungs
CNS (BBB)
Fenestrated capillaries
Large fenestrations (pores) in endothelium increase permeability
Occur in areas of active filtration/absorption & areas of endocrine hormone secretion
Found in:
Kidney
Small intestine
Sinusoid capillaries
Most permeable
Large intercellular clefts, fenestrations, & few tight junctions
Incomplete basement membranes
Allow large molecules & cells (RBCs, WBCs, platelets) to pass across walls
Found in:
Liver
Bone marrow
Spleen
Adrenal medulla
Capillary bed
Interwoven network of capillaries between arterioles & venules
Microcirculation
Flow of blood through bed
2 types of vessels that make up capillary bed:
Vascular shunt: channel that connects arteriole directly with venule
True capillaries: actual vessels involved in exchange
Veins
“Capacitance vessels”: act as blood reservoirs & contain up to 65% of blood supply
Carry blood toward heart
Under lower blood pressure than arteries
Formed when venules converge
Thinner walls & larger lumens compared to arteries (make veins good storage vessels)
Thin tunica media
Thick tunica externa
Adaptations of veins that ensure return of blood to heart:
Venous valves: prevent back-flow/pooling of blood
Venous sinuses
Venules
Smaller veins
Capillaries unite to form postcapillary venules
Blood pressure (BP)
Force per unit area exerted on wall of blood vessel by blood (as result of heartbeat)
Measured as systemic arterial BP in large arteries near heart
Pressure gradient provides driving force that keeps blood moving from higher to lower pressure areas
Peripheral resistance
Opposition to flow
Measurement of amount of friction blood encounters with vessel walls
3 sources of resistance:
1) Blood viscosity: thickness/stickiness due to formed elements & plasma proteins
Greater viscosity = increased resistance
2) Total blood vessel length:
Longer vessel = greater resistance encountered
3) Blood vessel diameter:
Radius increases = resistance decreases
Where is systemic pressure highest?
Aorta
Declines throughout pathway
Steepest drop occurs in arterioles
2 factors that determine arterial BP:
1) Elasticity (compliance/distensibility) of arteries close to heart
2) Volume of blood forced into them at any time
What does it mean for BP to be pulsatile?
BP rises/fall with each heartbeat
BP near heart is pulsatile
Venous BP
Small pressure gradient (~15 mmHg)
Low pressure due to cumulative effects of peripheral resistance
Blood oozes out slowly if vein severed
Functional adaptations for venous BP:
1) Muscular pump: contraction of skeletal muscles “milk” blood back toward heart
2) Respiratory pump: pressure changes during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand
3) Sympathetic venoconstriction: smooth muscles constrict to push blood back toward heart
(under sympathetic control)
Mean arterial pressure (MAP)
Pressure that propels blood to tissues
Declines with increasing distance from heart
diastolic pressure + (1/3)(pulse pressure)
Korotkoff sounds
Sounds medical personnel listen for when taking BP
Coordinated heartbeat is a function of:
1) Presence of gap junctions (direct protein connections between cells)
2) Intrinsic cardiac conduction system: network of noncontracile (autorhythmic) cells that initiate + distribute impulses to coordinate depolarization & contraction
Intrinsic control
Control is entirely from within tissue/organ
Uses paracrine or properties of muscle tissue
AKA: autoregulation or local control
Extrinsic control
Control is from outside of tissue/organ
Uses nerves/hormones
Examples where intrinsic & extrinsic control BOTH occur (work together):
1) Stroke volume (total amount of blood pumped from ventricle into systemic circulation)
2) Arteriolar diameter (vasoconstriction/dilation - regulates BP)
3) Glomerular filtration (kidneys)
Electrocardiograph
Detects electrical currents generated by heart
Electrocardiogram (ECG/EKG)
Graphic recording of electrical activity
Composite of ALL action potentials at a given time (NOT tracing of single AP)
Cardiac cycle
Blood flow through heart during 1 complete heartbeat
Atrial systole & diastole followed by ventricular systole & diastole
Series of pressure & blood volume changes
Electrical events PRECEDE mechanical events
Cardiac output (CO)
Volume of blood pumped out by each ventricle in 1 min
Normal = ~5.25 L/min
CO = HR x stroke volume
Stroke volume (SV)
Volume of blood pumped out by 1 ventricle with each beat
3 main factors affecting SV:
1) Preload: degree of stretch of heart muscle (affected by venous return)
2) Contractility: contractile strength at given muscle length (increased Ca2+ & positive inotropic agents increase contractility)
3) Afterload: back pressure exerted by arterial blood (normal aortic pressure = 80 mmHg; pulmonary trunk pressure = 10 mmHg)
Tachycardia
Pulse
Rhythmical throbbing caused by regular contraction & alternate expansion of artery as wave of blood passes through vessel (as result of each heartbeat)
ST elevation & ST depression
Cardiac arrhythmia
May be due to LV hypertrophy, pericarditis, & cardiac ischemia
Tall QRS complexes
Cardiac arrhythmia
Due to hypertrophy, abnormal pacemaker, aberrant HR
1st degree heart block
Cardiac arrhythmia
Slow/delayed electrical conduction from atria to ventricles
2nd degree heart block
Cardiac arrhythmia
Failure of AV node to conduct electrical impulses from atria to ventricles
Ventricular fibrillation
Cardiac arrhythmia
Uncoordinated contraction of myocardium (heart quiver)
Coronary circulation
Functional blood supply to heart muscle itself (receives 1/20 of body’s blood supply)
Shortest circulation in body
Delivered when heart is relaxed
LV receives most of coronary blood supply
Pulmonary circuit
Carries deoxygenated blood to lungs for gas exchange & returns it to heart
Systemic circuit
Supplies oxygenated blood to every organ of body
