AP II Lab Exam 2 Flashcards by Rachel Hantz

Blood vessels

Delivery system of dynamic structures that begins & ends at heart

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Arteries

Carry blood away from heart

Oxygenated (EXCEPT for pulmonary circulation & umbilical vessels)

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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)

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Veins

Carry blood toward heart

Deoxygenated (EXCEPT pulmonary circulation & umbilical vessels)

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Elastic arteries

“Conducting arteries”: conduct blood from heart to medium sized vessels

Thick-walled
Large + low-resistance lumen

Includes:
Aorta & major branches

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Muscular arteries

“Distributing arteries”: deliver blood to body organs

Thickest tunica media (more smooth muscle)

Active vasoconstriction

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Arterioles

“Resistance arteries”: change diameters to change resistance to blood flow

Smallest arteries

Control flow into capillary beds via vasodilation & vasoconstriction (smooth muscle)

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Continuous capillaries

Least permeable (tight junctions) & most common

Pinocytotic vesicles ferry fluid across endothelial cell

Found in:
Skin
Muscles
Lungs
CNS (BBB)

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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

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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

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Capillary bed

Interwoven network of capillaries between arterioles & venules

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Microcirculation

Flow of blood through bed

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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

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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

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Adaptations of veins that ensure return of blood to heart:

Venous valves: prevent back-flow/pooling of blood

Venous sinuses

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Venules

Smaller veins

Capillaries unite to form postcapillary venules

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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

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Peripheral resistance

Opposition to flow

Measurement of amount of friction blood encounters with vessel walls

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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