A&P Ch. 20 (Finished)

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Blood vessels
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Artery definition:

Blood vessel that carries blood away from heart, where it branches into ever-smaller vessels



Hollow passageway through which blood flows.

↑ Diameter lumen = ↓ pressure

↓ Diameter lumen = ↑ pressure


Vasa vasorum:

“vessels of the vessel”

Larger arteries & veins contain these small blood vessels within their walls to provide critical nutrient exchange- functions in outer layers of blood vessel due to high pressure


Tunica intima characteristics of arteries:

(tunica interna)

- Endothelium usually appears wavy due to constriction of smooth muscle
- Internal elastic mb present in larger vessels


Tunica media characteristics of arteries:

- Normally thickest layer in arteries
- Smooth muscle cells & elastic fibers predominate (proportions of these vary with distance from heart)

- External elastic membrane present in larger vessels


Tunica externa characteristics of arteries:

- Normally thinner than tunica media in all but largest arteries
- Collagenous & elastic fibers
- Nervi vasorum & vasa vasorum present


Tunica intima characteristics of veins:

- Endothelium appears smooth
- Internal elastic mb absent


Tunica media characteristics of veins:

- Normally thinner than tunica externa
- Smooth muscle cells & collagenous fibers predominate
- Nervi vasorum & vasa vasorum present
- External elastic mb absent


Tunica externa characteristics of veins:

- Normally thickest layer in veins
- Collagenous & smooth fibers predominate
- Some smooth muscle fibers Nervi vasorum & vasa vasorum present


Internal elastic membrane:

(internal elastic lamina)

- Thick, distinct layer of elastic fibers at boundary with tunica media
- Provides structure while allowing vessel to stretch

- Permeated with small openings allow exchange of materials between tunics.

- Many veins, particularly in lower limbs, contain valves formed by sections of thickened endothelium that are reinforced with CT, extending into lumen.


Under a microscope, how is the difference between veins and arteries determined?

Arteries: will appear wavy because due to partial constriction of smooth muscle in tunica media

Veins: lumen & entire tunica intima will appear smooth


What else does the tunica intima do?

- Composed of simple squamous endothelium
- Regulates capillary exchange & alters blood flow
- Endothelium releases endothelins that constrict smooth muscle within walls of vessel to ↑ blood pressure.

- Uncompensated overproduction of endothelins may contribute to hypertension


What functions does the tunica media perform physiologically?

- Substantial middle layer of vessel wall

- Consists of layers of smooth muscle supported by CT thats primarily made up of elastic fibers'arranged in circular sheets.
- Toward outer portion of tunic, are layers of longitudinal muscle.


Contraction & relaxation will ↑ & ↓ diameter of vessel lumen, what is responsible for this?

Circular muscles


What does vasoconstriction do specifically in arteries?

↓ blood flow as smooth muscle in walls of tunica media contract, thus making lumen narrower & ↑ blood pressure


What does vasodilation do specifically in arteries?

↑ blood flow as smooth muscle in walls of tunica media relax, allowing lumen to widen & ↓ blood pressure


Nervi vasorum:

“nerves of the vessel”

Small vascular nerves that run within walls of blood vessels. Generally all sympathetic fibers, although some trigger vasodilation & induce vasoconstriction

(depends on nature of neurotransmitter & receptors located on target cell)


External elastic membrane:

(external elastic lamina)

Separates tunica media from outer tunica externa in larger arteries. NOT seen in smaller arteries or veins.


Tunica externa:

(tunica adventitia)

- Substantial sheath of CT composed primarily of collagenous fibers + some bands of elastic fibers. In veins, contains groups of smooth muscle fibers.

- Normally thickest tunic in veins

- May be thicker than tunica media in some larger arteries.
- Outer layers of tunica externa not distinct but blend with surrounding CT outside vessel, helping to hold vessel in relative position.


Elastic artery:

- The closer to heart = thicker the walls, contains a ↑ % of elastic fibers in all 3 of their tunics.
- Vessels with 10 mm+ diameter = typically elastic.

- ↑ elastic fibers allow expansion & recoiling

- Recoiling of vascular wall helps to maintain pressure gradient that drives blood through arterial system.


What is an elastic artery also known as?

Conducting artery, due to ↑ diameter of lumen. This enables it to accept a ↑ volume of blood from heart & conduct it to smaller branches.


Muscular artery:

- Farther from the heart, % of elastic fibers in artery’s tunica intima ↓ & amount of smooth muscle in its tunica media ↑.

- Diameter: muscular arteries typically ranges from 0.1mm-10mm.

- Thick tunica media allows these arteries to play leading role in vasoconstriction. However, ↓ quantity elastic fibers = limit on their expansion. Fortunately, blood pressure ↓ by time it reaches these more distant vessels.



- Very small artery that leads to capillary

- Same 3 tunics as larger vessels, but thickness of each greatly diminished.

- Also known as resistance vessels


What do arterioles do?

-Primary site of both resistance and regulation of blood pressure

- Maintains vascular tone- similar to muscular tone of skeletal muscle
- All blood vessels exhibit vascular tone due to partial contraction of smooth muscle.



- Microscopic channel that supplies blood to tissues themselves (perfusion)

- Exchange of gases & other substances occur in these, between blood & interstitial fluid


What's unique about capillaries? And what are the 3 main types Of capillaries?

- To function, their walls must allow substances to pass through (leaky)

- They differ according to their degree of “leakiness:” continuous, fenestrated, & sinusoid capillaries



Blood flow through the capillaries


Continuous capillary:

- Most common type of capillary, found in almost all vascularized tissues

- Characterized by complete endothelial lining with tight junctions between endothelial cells

- Intercellular clefts allow for exchange of H2O, glucose & small hydrophobic molecules like gases, hormones, various leukocytes between blood plasma & interstitial fluid


Continuous capillaries associated with the brain are part of what? What are the characteristics of these capillaries?

- Apart of the B-B barrier

- Tight junctions, NO intercellular clefts, thick basement mb

- Also has astrocyte extensions (end feet); these + ^^ structures combine to prevent movement of nearly all substances.


Fenestrated capillary:

- Has pores/ fenestrations + tight junctions in endothelial lining. Thus making permeability for larger molecules. # of fenestrations & degree of permeability vary according to location

- Common in SI, kidneys, choroid plexus of brain + many endocrine structures, including hypothalamus, pituitary, pineal & thyroid glands.


Sinusoid capillary:

- Least common type of capillary. Theyre flattened, with extensive intercellular gaps & incomplete basement MB's + intercellular clefts & fenestrations. It literally looks like Swiss cheese


Why do sinusoid capillaries have such large openings in their tunica intima layer?

- Allows for passage of largest molecules; plasma proteins & even cells. Blood flow very slow, ↑ time for exchange of gases, nutrients, & wastes.


Where are sinusoid capillaries found?

- Found in liver, spleen, bone marrow, lymph nodes (where they carry lymph, NOT blood). Also found in pituitary & adrenal glands.

- Without these specialized capillaries, these organs would not be able to provide their wide assortment functions.



- Vessel with structural characteristics of an arteriole + a capillary.

- Slightly larger than typical capillary. Tunica media, is not continuous but forms sphincters prior to entrance to capillaries. Each ___ arises from a terminal arteriole & branches to supply blood


Capillary bed:

Consists of 10–100 capillaries, supplies by the metarteriole capillaries


Precapillary sphincters:

- Circular smooth muscle cells that surround capillary at its origin with metarteriole. Tightly regulates flow of blood from metarteriole to the capillaries it supplies

- Picture this: If all of capillary beds in body were to open simultaneously, they'd collectively hold every drop of blood in body & there would be none in the arteries, arterioles, venules, veins, or the heart itself. That's why these exist. It regulates the supplier


Why will a precapillary sphincter open?

When surrounding tissues need ↑ O2 & have excess waste products

- Allows ↑ blood to flow through & exchange to occur before closing once more


Where does blood flow go when precapillary sphincters are closed?

- Normally, they're closed. Flows from metarteriole → thoroughfare channel → into venous circulation (bypassing capillary bed entirely) - ^^ phenomenon creates a vascular shunt

- An arteriovenous anastomosis may also bypass capillary bed & lead directly to venous system.



- Blood that flows through capillary beds with an irregular, pulsating flow.
- Regulated by chemical signals that are triggered in response to changes in internal conditions, such as O2 , CO2 , H+ ion, & lactic acid levels.



- Extremely small vein, generally 8–100μm in diameter. Postcapillary venules join multiple capillaries exiting from a capillary bed.
- Multiple venules join to form veins.

- Venules & capillaries are also primary sites of diapedesis


What are the structural characteristics of venules?

- Consist of endothelium

- Thin middle layer with few muscle cells & elastic fibers + outer layer of CT fibers that constitute a very thin tunica externa



- Blood vessel that conducts blood toward heart.

- Thin-walled vessels (compared to arteries) with large & irregular lumens. ↓ pressure vessels
- Larger veins commonly equipped with valves that prevent possible back flow & keep flow toward heart.


Why are veins also considered reservoirs?

- Systemic veins contain ~64% of blood volume at any given time.

- Large lumens & relatively thin walls of veins make them far more distensible than arteries

- They're high capacitance vessels due to their capacity to distend readily to store ↑ volumes of blood, even at ↓ pressure.


When blood flow needs redistribution to other areas of the body, how does this work?

- Vasomotor center in medulla oblongata → sends sympathetic stimulation → tunica media in veins, causing venoconstriction
- Less dramatic than vasoconstriction seen in smaller arteries & arterioles
- Essentially “stiffening” of vessel wall. This ↑ pressure on blood within veins, speeding its return to heart.



Factors that impede or slow blood flow


Hydrostatic pressure:

Force exerted by fluid due to gravitational pull, usually against wall of the container in which it is located- blood pressure is a perfect example.


Blood hydrostatic pressure:

Force exerted by blood confined within blood vessels or heart chambers.


Capillary hydrostatic pressure (CHP):

- Pressure exerted by blood against wall of capillary

- Force that drives fluid out of capillariestissues.

- SAME as blood hydrostatic pressure, just more specific

- Will always be ↑ than IFHP from arterial pathways b/c lymphatic vessels are continually absorbing excess fluid from tissues (filtration)


Interstitial fluid hydrostatic pressure (IFHP):

Hydrostatic pressure in interstitial fluid correspondingly in response to fluid out of capillariestissues.


Blood pressure, 2 meanings:

- One form of hydrostatic pressure. Force exerted by blood upon walls of blood vessels or chambers of heart

- Or systemic arterial blood pressure without further clarification (pressure of blood flowing in arteries of systemic circulation)


In clinical practice, what is the measurement for blood pressure and where is it taken?

Measured in mm Hg & usually obtained using brachial artery of the arm.


What are the distinct components of arterial blood pressure?

- Systolic & diastolic pressures

- Pulse pressure

- Mean arterial pressure.


Pulse pressure:

- Systolic pressure - diastolic pressure
- Should be at least 25% of systolic pressure


If a pulse pressure is under 25%, what does this mean?

- Described as low or narrow.
- May occur in patients with low stroke volume, which can be seen in congestive heart failure, stenosis of aortic valve, or significant blood loss following trauma.


If a pulse pressure is over 25%, what does that mean?

- Described as high or wide

- Common in healthy people following strenuous exercise.

- If above 100 mm Hg consistently, consider excessive resistance of arteries, plus a few other disorders. Chronically, it can degrade heart, brain & kidneys- warrants medical treatment.


Mean arterial pressure (MAP):

- “Average” pressure of blood in arteries or average force driving blood into vessels that serve tissues.

- Formula: diastolic BP + (systolic-diastolic BP)/3 or 93.33

- Parameters: 70–110 mmHg. If <60 mmHg for extended time, ischemia occurs, resulting in hypoxia



↓ levels of O2 in arterial blood.


There are 10 common areas that are used to calculate someone's heart rate, what is this called and how does it work?

- Elastic fibers in arteries help maintain ↑ pressure gradient as they expand to accommodate blood, then recoil. This expansion & recoiling effect is known as a pulse.
- S ystolic & diastolic components of pulse are still evident down to level of arterioles.


What is the physiological significance of your pulse?

- In clinical settings, the rate rate & strength of pulse are important

- Pulse strength indicates strength of ventricular contraction & cardiac output.
- Strong pulse = ↑ systolic pressure.
- Weak pulse = systolic pressure ↓ → medical intervention may be warranted.


Korotkoff sounds:

Turbulent blood flow through vessels can be heard as soft ticking while measuring blood pressure. 5 identified sounds, only 2 are normally recorded



Blood pressure cuff attached to measuring device


How are results of taking blood pressure heard then calculated?

- First sound heard through stethoscope- 1st Korotkoff sound (systolic pressure)

- 2nd, last sound heard is recorded as patient’s diastolic pressure.

- As more air is released from cuff, blood is able to flow freely through brachial artery, all sounds disappear.


What are the 5 variables that affect blood pressure & blood flow?

  • C2V2B
  • C ardiac output
  • C ompliance
  • V olume of the blood
  • V iscosity of the blood
  • B lood vessel length & diameter


Ability of any compartment to expand to accommodate increased content


What is Poiseuille’s equation?

Blood fl w = π ΔP r4/ 8ηλ

  • π: pi, constant that is ratio of circle’s circumference to its diameter.
  • ΔP: difference in pressure
  • r4: radius (one-half diameter) of vessel to 4th power. (*)
  • η: eta, represents viscosity of the blood (*)
  • λ: lambda, represents length of blood vessel. (*)

What are the 3 important variables to Poiseuille’s equation?

*Since 8 & π are constants*
- Vessel length (λ or L): changes slowly
- Viscosity (η): changes slowly
- Radius (r4): changes rapidly, vasoconstriction & vasodilation → direct impact on flow & resistance



Low blood volume, may be caused by bleeding, dehydration, vomiting, severe burns, or some medications used to treat hypertension.



- Excessive fluid volume, may be caused by retention of water & sodium.
- Seen in patients with heart failure, liver cirrhosis, some forms of kidney disease, hyperaldosteronism & glucocorticoid steroid treatments.


One of the 2 determinants of blood viscosity are the elements formed within it- such as erythrocytes. Why is this important?

Vast majority of formed elements: erythrocytes- any condition affecting erythropoiesis, such as polycythemia or anemia, can alter viscosity of blood


One of the 2 determinants of blood viscosity are plasma proteins. Why is this important?

Theyre produced by liver- any condition affecting liver function can change viscosity slightly, therefore altering blood flow. Liver abnormalities such as hepatitis, cirrhosis, alcohol damage & drug toxicities result in ↓ levels of plasma proteins, which ↓ blood viscosity.


What is the impact of blood vessel length?

Length is directly proportional to resistance.
Longer the vessel = ↑ resistance, ↓ flow
Shorter the vessel = ↓ resistance, ↑ flow


How many miles of vessels are in 1lb of adipose tissue?

200 miles, if 10lbs is gained, thats an additional 2000-4000 miles of vessels, which ↑ resistance for heart to pump to.


What is the impact of blood vessel diameter?

- Diameter changes according to type of vessel. May change frequently throughout day due to neural & chemical signals that trigger vasodilation & vasoconstriction. Given same volume of blood:

- ↑ vessel diameter = ↓ friction, ↓ resistance which subsequently ↑ flow.

- ↓ vessel diameter = ↑ friction, ↑ resistance which ↑ flow.


Vascular tone:

The contractile state of smooth muscle & primary determinant of diameter → resistance & flow.



- ↓ Compliance, ↑ pressure, ↑ resistance within vessel = ↑ resistance, thus ↑ cardiac workload

- Leading cause of hypertension & coronary heart disease


Skeletal muscle pump:

- Helps lower-pressure veins counteract force of gravity, ↑ pressure to move blood back to heart.
- As leg muscles contract, for example during walking or running, they exert pressure on nearby veins with their numerous one-way valves.


Respiratory pump:

Aids blood flow through veins of thorax & abdomen.

During inhalation, thorax volume ↑, largely through contraction of diaphragm, which moves downward & compresses abdominal cavity.

During exhalation, when air pressure within thoracic cavity ↑ → pressure in thoracic veins ↑ → speeding blood flow into atria of heart & valves in veins prevent blood from flowing backward from thoracic & abdominal veins.


Bulk flow:

Mass movement of fluids in & out of capillary beds involves a transport mechanism far more efficient than mere diffusion. This involves two pressure-driven mechanisms



Volumes of fluid move from area of ↑ pressure in capillary bed → area of ↓ pressure in tissues



- Volumes of fluid move from area of ↑ pressure in tissues → area of ↓ pressure in capillaries

- Osmotic pressure drives this


Reabsorption & Filtration are 2 types of pressures that drive what?

Hydrostatic pressure & osmotic pressure


Osmotic pressure:

- Movement of fluid from interstitial fluid back into capillaries

- Determined by osmotic concentration gradients- difference in solute-to-water concentrations in blood & tissue fluid.


In the case of osmotic pressure, what is the key factor that contributes to concentration gradients?

Plasma proteins. Solutes also move across capillary wall according to concentration gradient, but doesnt have a significant impact on osmosis.
- Due to their large size & chemical structure, they're not solutes b/c they dont dissolve but are dispersed or suspended in their fluid medium, forming a colloid rather than a solution.


Blood colloidal osmotic pressure (BCOP):

- Pressure exerted by colloids suspended in blood within vessel, primary determinant is presence of plasma proteins

- Accounts for reabsorption of H2O

- Always higher than IFCOP


Interstitial fluid colloidal osmotic pressure (IFCOP):

- Pressure exerted by colloids within interstitial fluid, which is low since this fluid contains little proteins

- H2O is drawn from tissue fluid back into capillary, carrying dissolved molecules with it. This difference in colloidal osmotic pressure accounts for reabsorption.


Net filtration pressure (NFP):

- Represents interaction of hydrostatic & osmotic pressures, driving fluid out of capillary.

- Equal to difference between CHP & BCOP.

- Due to function (going out), its a - number

- Changes at different points in a capillary bed


Its inevitable that more net fluid will exit capillaries through filtration at the arterial end than fluid entering through reabsorption at venous end. What is done with this excess fluid?

- Picked up by capillaries of lymphatic system.
- These extremely thin-walled, has copious numbers of valves that ensure unidirectional flow through ever-larger lymphatic vessels that eventually drain into subclavian veins in neck.

- Important function of lymphatic system is to return fluid (lymph) to blood. Lymph may be thought of as recycled blood plasma


What are the main homeostatic mechanisms that ensure adequate blood flow?

- Blood pressure

- Distribution

- Ultimately perfusion: neural, endocrine & autoregulatory mechanisms


Atrial reflex:

If blood is returning to R-atrium faster than being ejected from L-ventricle, these receptors stimulate cardiovascular centers to ↑ sympathetic firing & ↑ cardiac output until homeostasis is achieved.


How does the endocrine system regulate the cardiovascular system?

Involves the catecholamines, epinephrine & norepinephrine + several hormones that interact with kidneys in regulation of blood volume


Which catecholamines are released by the adrenal medulla and enhance the "fight or flight" response?

- Epinephrine & norepinephrine.
- ↑ heart rate, ↑ force of contraction, while temporarily constricting blood vessels to organs not essential for this response & redirecting blood flow to liver, muscles, and heart.




- Both a hormone & most common NT of sympathetic NS

- Acts mostly on α-receptors, some stimulation of β-receptors

- ↑ rate of contractions of heart & + epinephrine, underlies fight-or-flight response.




- Mostly a hormone (synthesized in adrenal medulla), although small amounts are made in nerve fibers where it acts as a NT. ONLY released during times of stress.

- Relatively nonspecific, stimulating both α & β-1, β-2, β-3 receptors more or less equally.

- By binding to these receptors, it triggers a number of changes, all of which are aimed at either ↑ energy use by body or making ↑ energy available for use.. it affects more things


What is the use of norepinephrine (noradrenaline) in clinical settings?

- ↑ or maintain blood pressure during acute medical situations that cause ↓ blood pressure. Used in combination with other meds
- Situations include: cardiac arrest, spinal anesthesia, septicemia, blood transfusions, drug reactions


What is the use of epinephrine (adrenaline) in clinical settings?

- Used for ↓ blood pressure associated with septic shock, allergic reactions, and in eye surgery to maintain dilation of pupil.


Antidiuretic hormone (ADH):


- Secreted by cells in hypothalamus & transported via hypothalamic-hypophyseal tracts → posterior pituitary where its stored until being released upon stimulation.
- Signals its target cells in kidneys to reabsorb ↑ H2O, thus ↓ fluid loss in urine.
- This ↑ overall fluid levels & helps restore blood volume & pressure. In addition, this hormone constricts peripheral vessels.


What is renin?

- Enzyme, but due to its role in renin-angiotensin-aldosterone pathway, some sources identify it as hormone.


What does Renin do?

- Specialized cells in kidneys found in juxtaglomerular apparatus respond to ↓ blood flow by secreting renin into blood.
- Renin converts plasma protein angiotensinogen → produced by liver, into its active form- angiotensin I.
- Angiotensin I circulates in blood then converted → angiotensin II in lungs. This reaction is catalyzed by enzyme angiotensin-converting enzyme (ACE)


Angiotensin II:

- Powerful vasoconstrictor, greatly ↑ blood pressure.

- Stimulates release of ADH & aldosterone- hormone produced by adrenal cortex

- Stimulates thirst center in hypothalamus, so an individual will likely consume ↑ fluids, ↑ blood volume, ↑ blood pressure.



↑ reabsorption of Na+ into blood by kidneys.

H2O follows Na+ thus, ↑ reabsorption of H2O. This ↑ blood volume, ↑ blood pressure.


Erythropoietin (EPO):

- Released by kidneys when blood flow and/or O2 levels ↓
- Stimulates production of erythrocytes within bone marrow. Erythrocytes are major formed element of blood, 40% of blood volume

- Also a vasoconstrictor


Atrial natriuretic hormone (ANH):

(Atrial natriuretic peptide)

- Secreted by cells in atria of heart

- Secreted when blood volume is ↑ enough to cause extreme stretching of cardiac cells


Cells in the ventricle produce a hormone similar to ANH with similar effects, what is this hormone called and what does it do?

  • B-type natriuretic hormone.
  • Antagonists to angiotensin II
  • Promote loss of Na + & H 2 O from kidneys, suppresses renin, aldosterone, ADH production & release. All of these actions promote ↓ fluid from the body, so blood volume & blood pressure ↓

Myogenic response:

  • Reaction to stretching of smooth muscle in walls of arterioles as changes in blood flow occur through vessel
  • Localized process that serves to stabilize blood flow in capillary network that follows that arteriole
  • Bear in mind, that dilation & constriction of arterioles feeding capillary beds are primary control mechanism

What are the clinical parameters of prehypertension?

Between 120/80 and 140/90 mmHg


What are the clinical parameters of hypertension?

Chronic & persistent blood pressure measurements of >140/90 mmHg


What occurs in response to a significant loss (<20%) of blood pressure and blood volume?

1. Stimuli from baroreceptors trigger cardiovascular centers →

2. Stimulates sympathetic responses to ↑ cardiac output & ↑ vasoconstriction → ↑ heart rate 180-200bpm

3. Sympathetic stimulation also triggers release of epinephrine & norepinephrine, which enhance both cardiac output & vasoconstriction


If there is significant loss of blood volume (but <20%) what is the role of the endocrine system?

  • Angiotensin-renin- aldosterone mechanism stimulates thirst center in hypothalamus, which ↑ fluid consumption to help restore lost blood.
  • More importantly, ↑ renal reabsorption of Na+ & H2O thus ↓ water loss in urine output.
  • Kidneys also ↑ production of EPO, stimulating formation of erythrocytes that not only deliver oxygen to tissues but also ↑ blood volume.

Circulatory shock:

Life-threatening condition in which circulatory system is unable to maintain blood flow to adequately supply sufficient O2 & other nutrients to tissues to maintain cellular metabolism.


What are the symptoms of circulatory shock?

  • ↑ heart rate, ↓ blood pressure (Sometimes BP is maintained)
  • Patient may appear confused or lose consciousness
  • Urine output of <1 mL/kg body weight/hour is cause for concern

What most commonly causes hypovolemic shock?

  • Adults: Typically from hemorrhage
  • Children: ↑ vomiting or ↑ diarrhea.
  • Treatment: intravenous fluids to restore patient to normal function & various drugs such as dopamine, epinephrine, & norepinephrine to ↑ blood pressure.

What are some other causes of hypovolemic shock?

Extensive burns, exposure to toxins, polyuria related to diabetes insipidus or ketoacidosis.


What are the symptoms of hypovolemic shock?

  • Rapid, almost tachycardic heart rate; a weak pulse often described as “thread;”
  • Cool, clammy skin, particularly in extremities, due to restricted peripheral blood flow
  • rapid, shallow breathing
  • Hypothermia
  • ↑ thirst & dry mouth.

Cardiogenic shock:

  • Inability of heart to maintain cardiac output.
  • Most often, it results from myocardial infarction

What else can cause cardiogenic shock?

Can be caused by arrhythmias, valve disorders, cardiomyopathies, cardiac failure, or simply insufficient flow of blood through cardiac vessels.


What is the treatment for cardiogenic shock?

  • Involves repairing damage to heart
  • or its vessels to resolve underlying cause, rather than treating that condition directly.

What is vascular shock?

  • When arterioles lose their normal muscular tone & dilate dramatically.
  • May arise from variety of causes

What is the treatment for vascular shock?

  • Treatments almost always involve fluid replacement & inotropic or pressor agents, which restore tone to muscles of vessels
  • Alleviation of the condition is required so it might include antibiotics & antihistamines, or select steroids, which may aid in repair of nerve damage.


  • Also called blood poisoning
  • Widespread bacterial infection that results in organismal-level inflammatory response known as septic shock

Neurogenic shock:

Form of vascular shock that occurs with cranial or spinal injuries that damage cardiovascular centers in medulla oblongata or nervous fibers originating from this region


Anaphylactic shock:

Severe allergic response that causes widespread release of histamines, triggering vasodilation throughout body.


Obstructive shock:

When a significant portion of vascular system is blocked. NOT always recognized as distinct condition & may be grouped with cardiogenic shock, including pulmonary embolism & cardiac tamponade.


What are the treatments for obstructive shock?

  • Dependent on underlying cause
  • Administering fluids intravenously, often includes anticoagulants
  • Removal of fluid from pericardial cavity, or air from thoracic cavity

What are the causes of obstructive shock?

  • Pulmonary embolism, (clot lodged in pulmonary vessels)
  • Stenosis of aortic valve
  • Cardiac tamponade (excess fluid in pericardial cavity)
  • Pneumothorax (↑ air present in thoracic cavity, outside of lungs) which interferes with venous return, pulmonary function & delivery of oxygen to tissues.

Pulmonary circuit:

R-atrium → R-ventricle → pumps to lungs for gas exchange


Pulmonary trunk:

  • Single vessel exiting R-ventricle
  • R-ventricle → semilunar valve → pulmonary trunk→ curves posteriorly & rapidly bifurcates → R & L pulmonary artery

What do the right & left pulmonary arteries branch into within the lungs?

Smaller arteries & arterioles → pulmonary capillaries, which surround alveoli- site of O2 & CO2 exchange, it gets oxygenated


Once blood is oxygenated in the alveoli, where does it go from there?

Blood flows from pulmonary capillaries → series of pulmonary venules → 4 larger pulmonary veins (2 on L, 2 on R) that return blood to L-atrium



  • Largest artery in body
  • Arises from L-ventricle → descends to abdominal region → bifurcates at 4th lumbar vertebrae → 2 common iliac arteries.

What does the aorta consist of?

  • Ascending aorta
  • Aortic arch
  • Descending aorta- passes through diaphragm + landmark that divides into → superior thoracic & inferior abdominal components.

What are the components of the aorta in order?

Once exiting heart → ascending aorta → aortic arch → descending aorta → thoracic aorta → abdominal aorta


Ascending aorta:

Moves in superior direction for ~5cm & ends at sternal angle


Aortic arch:

  • Follows ascending aorta, reverses direction, forms arc to left.
  • Descends toward inferior portions of body & ends at level of intervertebral disk between 4th & 5th thoracic vertebra

Descending aorta:

Continues close to bodies of vertebrae & passes through opening in diaphragm (aortic hiatus)


What are the first 2 (of 5) arteries that arise from the aortic arch?

( From L→R )

L-subclavian artery & L-common carotid artery


What are the last 2 (of 5) arteries that arise from the aortic arch?

( From L→R )

  • Brachiocephalic artery gives way to → R-subclavian artery & R-common carotid artery

Brachiocephalic artery:

  • Located only on R-side of body, no corresponding artery on L

Subclavian artery:

  • Supplies blood to arms, chest, shoulders, back & central nervous system.
  • Gives rise to 3 major branches: internal thoracic artery, vertebral artery & thyrocervical artery.

Internal thoracic artery:

(mammary artery)

Supplies blood to thymus, pericardium of heart & anterior chest wall


Vertebral artery (VA):

Passes through vertebral foramen in cervical vertebrae → through foramen magnum into → cranial cavity to supply blood to brain & spinal cord.


What does the vertebral artery arise from?

  • From each subclavian artery → creates anastomosis & forms larger basilar artery at base of medulla oblongata.
  • The subclavian artery also gives rise to the thyrocervical artery that provides blood to the thyroid, the cervical region of the neck, and the upper back and shoulder

Thyrocervical artery:

  • Arises from subclavian artery
  • Provides blood to thyroid, cervical region of neck, upper back & shoulder

Common carotid artery:

  • Divides into internal & external carotid arteries.
  • R-common carotid artery arises from brachiocephalic artery
  • L-common carotid artery arises directly from aortic arch

External carotid artery:

  • Arises from common carotid artery
  • Supplies blood to numerous structures within face, lower jaw, neck, esophagus & larynx.
  • These branches include lingual, facial, occipital, maxillary & superficial temporal arteries.

Internal carotid artery:

  • Initially forms carotid sinus (just superior to internal & external carotid bifurcation) containing carotid baroreceptors & chemoreceptors.
  • Like aortic sinus counterparts, information provided by these receptors are critical to maintaining cardiovascular homeostasis

Transient ischemic attack (TIA):

Resulting in loss of consciousness or temporary loss of neurological function. In some cases, damage may be permanent.


Cerebrovascular accident (CVA):

Loss of blood flow for longer periods, typically between 3 & 4 minutes, will likely produce irreversible brain damage or a stroke


Arterial circle:

(Circle of Willis)

  • Both carotid & vertebral arteries branch once they enter cranial cavity, and some of these branches form an anastomosis thats similar to traffic circle that sends off branches (in this case, arterial branches to brain).
  • Branches to anterior portion of cerebrum: fed by internal carotid arteries
  • Remainder of brain receives blood flow from branches associated with vertebral arteries.

The internal carotid artery continues through the carotid canal of the temporal bone and enters the base of the brain through the carotid foramen where it gives rise to 3 artery branches, what are they?

  • Anterior cerebral artery
  • Middle cerebral artery
  • Ophthalmic artery

What does the anterior cerebral artery supply blood to?

Frontal lobe of cerebrum


What does the middle cerebral artery supply blood to?

Temporal & parietal lobes (most common sites of CVAs)


What does the anterior cerebral artery supply blood to?

Provides blood to eyes


Anterior communicating artery:

R & L- anterior cerebral arteries join together to form this anastomosis


How is the anterior portion of the arterial circle formed?

With the initial segments of anterior cerebral arteries & anterior communicating artery


How is the posterior portion of the arterial circle formed?

  • By L&R-posterior communicating artery that branches from posterior cerebral artery, which arises from basilar artery
  • Provides blood to posterior portion of cerebrum & brain stem

Basilar artery:

Anastomosis that begins at junction of the 2 vertebral arteries & sends branches to cerebellum & brain stem. It flows into posterior cerebral arteries.


Where does the thoracic aorta start?

  • T5-T12, initially traveling within the mediastinum to left of vertebral column.
  • Gives rise to several branches, collectively referred to as visceral branches & parietal branches

Visceral branches:

  • Supplies blood primarily to visceral organs.
  • Includes bronchial arteries, pericardial arteries, esophageal arteries & mediastinal arteries (each named after tissues it supplies)

Bronchial artery:

  • Typically 2 on L & 1 on R
  • Systemic branch from aorta, provides O2'ed blood to lungs + pulmonary circuit that brings blood for oxygenation
  • Follows same path as respiratory branches, beginning with bronchi & ending with bronchioles

Pericardial artery:

  • Branch of thoracic aorta
  • Supplies blood to pericardium

Esophageal artery:

  • Branch of thoracic aorta
  • Supplies blood to esophagus

Mediastinal artery:

  • Branch of thoracic aorta
  • Supplies blood to mediastinum

Parietal branches:
(Somatic branches)

Group of arterial branches of thoracic aorta; includes those supplying blood to thoracic wall, vertebral column & superior surface of diaphragm


What arteries make up the visceral branches?

  • Bronchial
  • Esophageal
  • Mediastinal
  • Pericardial

What arteries make up the somatic or parietal branches?

  • Intercostal artery → provides blood to muscles of thoracic cavity & vertebral column
  • Superior phrenic artery → Provides blood to superior surface of diaphragm
  • Inferior phrenic artery → provides blood to inferior surface of diaphragm

When is the thoracic aorta considered the abdominal aorta?

When it crosses diaphragm at aortic hiatus


Abdominal aorta, where does it remain once through the aortic hiatus and what does it give rise to?

  • Remains to L of vertebral column → Embedded in adipose tissue behind peritoneal cavity → Ends at ~ L4 → gives rise to several branches → Bifurcates to form common iliac arteries.

Celiac trunk (artery):

  • Major branch of abdominal aorta → gives rise to L- gastric artery, splenic artery & common hepatic artery →
  • → Forms hepatic artery to liver, R-gastric artery to stomach, & cystic artery to gall bladder

Superior mesenteric artery:

  • Arises ~2.5cm after celiac trunk
  • Branches into several major vessels that supply blood to SI (duodenum, jejunum & ileum), pancreas, and majority of LI

Inferior mesenteric artery:

  • Arises ~5cm superior to common iliac arteries
  • Supplies blood to distal segment of LI, including rectum

Inferior phrenic artery:

  • Each are branches of abdominal aorta
  • Supplies blood to inferior surface of diaphragm

Adrenal artery:

  • Arises near superior mesenteric artery
  • Branch of the abdominal aorta
  • Supplies blood to the adrenal (suprarenal) glands

Renal artery:

  • Each ~2.5cm inferior to superior mesenteric arteries
  • Branch of abdominal aorta
  • Supplies each kidney

Gonadal artery:

  • Branch of abdominal aorta
  • Each supplies blood to gonads or reproductive organs; also described as ovarian arteries or testicular arteries

Ovarian artery:

  • Branch of abdominal aorta
  • Supplies blood to ovary, uterine (Fallopian) tube & uterus
  • Located within suspensory ligament of uterus

Testicular artery:

  • Branch of abdominal aorta
  • Longer since it travels outside body cavity to testes & forms 1 component of spermatic cord
  • Longer than ovarian artery

Lumbar artery:

  • Branches of abdominal aorta
  • Supplies blood to lumbar region, abdominal wall & spinal cord

Common iliac artery:

Branch of aorta that leads to internal & external iliac arteries


Median sacral artery:

Continuation of aorta into sacrum


Internal iliac artery:

  • Branch from common iliac arteries
  • Supplies blood to urinary bladder, walls of pelvis, external genitalia, & medial portion of femoral region
  • In females, provides blood to uterus & vagina

External iliac artery:

  • Branch of common iliac artery that leaves body cavity & becomes femoral artery
  • Supplies blood to lower limbs

What are the paired arteries in the thoracic aorta?

  • Intercostal
  • Superior phrenic

What are the unpaired arteries of abdominal aorta within the celiac trunk?

  • L-gastric
  • Splenic
  • Common hepatic

What are the paired arteries of the abdominal aorta?

  • Inferior phrenic
  • Adrenal
  • Renal
  • Gonadal
  • Lumbar
  • Common iliac

Axillary artery:


  • Continuation of subclavian artery as it penetrates body wall & enters this region
  • Supplies blood to region near head of humerus (humeral circumflex arteries); majority of vessel continues into brachium and becomes brachial artery (2a)

Brachial artery:


  • Continuation of axillary artery (1a) in brachium
  • Supplies blood to bulk of brachial region → gives off several smaller branches which provide blood to posterior surface of arm in elbow region
  • Bifurcates → radial (3a) & ulnar (4a) arteries at coronoid fossa

Radial artery:


  • Formed at bifurcation of brachial artery (2a) → parallels radius → gives off smaller branches til reaching carpal region
  • → fuses with ulnar artery forming superficial & deep palmar arches (5a)
  • Supplies blood to lower arm & carpal region

Ulnar artery:


  • Formed at bifurcation of brachial artery (2a) → parallels ulna → gives off smaller branches til reaching carpal region
  • → Fuses with radial artery forming superficial & deep palmar arches (5a)
  • Supplies blood to lower arm & carpal region

Palmar arches:

(superficial and deep)


  • Formed from anastomosis of radial (3a) & ulnar (4a) arteries
  • Supplies blood to hand & digital arteries (6a)

Digital arteries:


  • Formed from superficial & deep palmar arches (5a)
  • Supplies blood to de digits

Femoral artery:


  • Continuation of external iliac artery post-body cavity → divides into several smaller branches- lateral deep femoral artery (1b) & genicular artery (4b)

As the femoral artery passes through the posterior knee what does it become?

Popliteal artery


Deep femoral artery:


  • Branch of femoral artery (1b)
  • Gives rise to lateral circumflex arteries (3b)

Lateral circumflex artery:


  • Branch of deep femoral artery (2b)
  • Supplies blood to deep muscles of thigh, ventral regions, lateral regions of integument

Genicular artery:


  • Branch of femoral artery (1b)
  • Supplies blood to region of knee

Popliteal artery:


  • Continuation of femoral artery (1b) posterior to knee
  • Branches into anterior & posterior tibial arteries

Anterior tibial artery:


  • Branches from popliteal artery (5b)
  • Supplies blood to anterior tibial region → becomes dorsalis pedis artery (7b)
  • Located between tibia & fibula

Dorsalis pedis artery:


  • Forms from anterior tibial artery (6b)
  • Branches repeatedly to supply blood to tarsal & dorsal regions of foot

Posterior tibial artery:


  • Branches from popliteal artery (5b)
  • Gives rise to fibular or peroneal artery
  • Supplies blood to posterior tibial region

Medial plantar artery:


  • Arises from bifurcation of posterior tibial arteries (8b)
  • Supplies blood to medial plantar surfaces of foot

Lateral plantar artery:


  • Arises from bifurcation of posterior tibial arteries (8b)
  • Supplies blood to lateral plantar surfaces of foot

Dorsal/ arcuate arch as well as plantar arch:


  • Both formed from anastomosis of dorsalis pedis artery (7b) and medial (9b) & plantar arteries (10b)
  • Branches supply distal portions of foot & digits
  • Take this literally as it sounds*

Superior vena cava:


  • Large systemic vein
  • Drains blood from most areas superior to diaphragm
  • Empties into R-atrium

Subclavian vein:


  • Located deep in thoracic cavity
  • Formed by axillary vein as it enters thoracic cavity from axillary region
  • Drains axillary & smaller local veins near scapular region → leads to brachiocephalic vein (3c)

Brachiocephalic veins:


  • Pair of veins that form from fusion of external (4D) & internal jugular veins (1D) + subclavian vein (2c)
  • Subclavian, external and internal jugulars, vertebral & internal thoracic veins flow into it
  • Drains upper thoracic region → leads to superior vena cava (1c)

Vertebral vein:


  • Arises from base of brain & cervical region of spinal cord
  • Passes through intervertebral foramina in cervical vertebrae → drains smaller veins from cranium, spinal cord & vertebrae
  • Leads to brachiocephalic vein (3c) → counterpart of vertebral artery

Internal thoracic veins:

(internal mammary veins)


  • Drains anterior surface of chest wall
  • Leads to brachiocephalic vein (3c)

Intercostal vein:


  • Drains muscles of thoracic wall
  • Leads to azygos vein (9c)

Esophageal vein:


  • Drains inferior portions of esophagus
  • Leads to azygos vein (9c)

Bronchial vein:


  • Drains systemic circulation from lungs
  • Leads to azygos vein (9c)

Azygos vein:


  • Originates in lumbar region & passes through diaphragm into thoracic cavity on R-side of vertebral column
  • Drains blood from intercostal veins, esophageal veins, bronchial veins, and other veins draining mediastinal region
  • Leads to superior vena cava (1c)

Hemiazygos vein:


  • Smaller vein complementary to azygos vein (9c)
  • Drains esophageal veins from esophagus and L- intercostal veins
  • Leads to brachiocephalic vein (3c) via superior intercostal vein

Internal jugular vein:


  • "Counterpart" of common carotid artery
  • Passes through jugular foramen & canal
  • Primarily drains blood from brain, receives superficial facial vein
  • Empties into subclavian vein (2c)

Temporal vein:


  • Drains blood from temporal region
  • Flows into external jugular vein (4d)

Maxillary vein:


  • Drains blood from maxillary region
  • Flows into external jugular vein (4d)

External jugular vein:


  • Drains blood from more superficial portions of head, scalp & cranial regions
  • Leads to subclavian vein (2c)

Superior sagittal sinus:


  • Enlarged vein located midsagittally between meningeal & periosteal layers of dura mater within falx cerebri
  • Receives most of blood drained from superior surface of cerebrum → leads to inferior jugular vein (1d) & vertebral vein (4c)
  • Can be mistaken for subarachnoid space

Great cerebral vein:


Receives bulk of smaller vessels from inferior cerebral veins & leads to straight sinus (3e)


Straight sinus:


  • Enlarged vein that drains blood from brain
  • Receives most of blood from great cerebral vein (2e)
  • Leads to L or R transverse sinus (7e)

Cavernous sinus:


  • Enlarged vein that receives blood from bulk of other cerebral veins & eye socket
  • Leads to petrosal sinus (5e)

Petrosal sinus:


  • Enlarged vein that receives blood from cavernous sinus (4e)
  • Leads into internal jugular veins (1d)

Occipital sinus:


  • Enlarged vein that drains occipital region near falx cerebelli
  • Leads to L & R transverse sinuses (7a) as well as vertebral veins (4c)

Transverse sinuses:


  • Pair of enlarged veins near lambdoid suture that drains the occipital, sagittal & straight sinuses
  • Leads to sigmoid sinuses (8e)

Sigmoid sinuses:


  • Enlarged vein that receives blood from transverse sinuses (7e)
  • Leads through jugular foramen → internal jugular vein (1d)

Digital veins:


Drains digits → leads to palmar arches (2f) of hand & dorsal venous arch of foot


Palmar venous arches:


Drains hand & digits → leads to radial vein (3f), ulnar veins (4f), & median antebrachial vein (6f)


Radial vein:


  • Vein that parallels radius & radial artery (3a)
  • Arises from palmar venous arches (2f) → leads to brachial vein (5f)

Ulnar vein:


  • Vein parallels the ulna & ulnar artery (4a)
  • Arises from palmar venous arches (2f) → leads to brachial vein (5f)

Brachial vein:


  • Deeper vein of the arm that forms from radial (3f) & ulnar (4f) veins in lower arm → leads to axillary vein (11f)

Median antebrachial vein:


  • Vein that parallels ulnar vein (4f) but more medial in location
  • Intertwines with palmar venous arches (2f) → leads to basilic vein (7f)

Basilic vein:


  • Superficial vein of arm that arises from median antebrachial vein (6f) → intersects with median cubital vein (8f), parallels ulnar vein (4f)
  • Continues into upper arm along with brachial vein (5f) → leads to axillary vein (11f)

Median cubital vein:


  • Superficial vessel located in antecubital region.
  • Links cephalic vein (9f) to basilic vein (7f) in form of a V
  • Frequent site from which to draw blood

Cephalic vein:


  • Superficial vessel in upper arm
  • Leads to axillary vein (11f)

Subscapular vein:


  • Drains blood from subscapular region
  • Leads to axillary vein (11f)

Axillary vein:


  • Major vein in axillary region
  • Drains upper limb → becomes subclavian vein (2c)

Inferior vena cava:


  • Large systemic vein that drains blood from areas largely inferior to diaphragm
  • Empties into R-atrium

Lumbar veins:


  • Series of veins that drain lumbar portion of abdominal wall & spinal cord
  • Ascending lumbar veins drain into azygos vein (9c) on R & Hemiazygos vein (10c) on L
  • Remaining lumbar veins drain directly into inferior vena cava

Renal vein:


  • Largest vein entering inferior vena cava (1g)
  • Drains kidneys & flows into inferior vena cava (1g)

Adrenal vein:


  • Drains adrenal or suprarena
  • R- adrenal vein enters inferior vena cava (1g) directly
  • L- adrenal vein enters L-renal vein (3g)

Testicular vein:


  • Drains testes & forms part of spermatic cord
  • R-testicular vein empties directly into inferior vena cava (1g)
  • L-testicular vein empties into L-renal vein (3g)

Ovarian vein:


  • Drains ovary
  • R-ovarian vein empties directly into inferior vena cava (1g)
  • L-ovarian vein empties into the L-renal vein (3g)

Gonadal vein:


  • Generic term for vein draining a reproductive organ
  • May be either an ovarian vein or a testicular vein, depending on sex of individual

Phrenic vein:


  • Drains diaphragm
  • R-phrenic vein flows into inferior vena cava (1g)
  • L-phrenic vein empties into L-renal vein (3g)

Hepatic vein:


  • Drains systemic blood from liver & flows into inferior vena cava (1g)

Plantar veins:


  • Drains foot
  • Flows into plantar venous arch (3h)

Dorsal venous arch:


  • Drains blood from digital veins (1f) & vessels on superior surface of foot

Plantar venous arch:


  • Formed from plantar veins (1h)
  • Flows into anterior & posterior tibial veins (4h & 5h) through anastomoses

Anterior tibial vein:


  • Formed from dorsal venous arch (2h)
  • Drains area near tibialis anterior muscle & flows into popliteal vein (8h)

Posterior tibial vein:


  • Formed from dorsal venous arch (2h)
  • Drains area near posterior surface of tibia & flows into popliteal vein (8h)

Fibular vein:


  • Drains muscles & integument near fibula & flows into popliteal vein (8h)

Small saphenous vein:


  • Located on lateral surface of leg
  • Drains blood from superficial regions of lower leg & foot
  • Flows into the popliteal vein (8h)

Popliteal vein


  • Drains region behind knee & forms from fusion of fibular (6h), anterior & posterior tibial veins (4h & 5h)
  • Flows into femoral vein (12h)

Great saphenous vein:


  • Prominent surface vessel located on medial surface of leg & thigh
  • Drains superficial portions of these areas & flows into femoral vein (12h)

Deep femoral vein:


  • Drains blood from deeper portions of thigh & flows into femoral vein (12h)

Femoral circumflex vein:


  • Forms loop around femur just inferior to trochanters
  • Drains blood from areas around head & neck of femur
  • Flows into femoral vein (12h)

Femoral vein:


  • Drains upper leg
  • Receives blood from great saphenous vein (9h), deep femoral vein (10h) & femoral circumflex vein (11h)
  • Becomes external iliac vein when it crosses body wall

External iliac vein:


  • Formed when femoral vein (12h) passes into body cavity
  • Drains legs & flows into common iliac vein (16h)

Internal iliac vein:


  • Drains pelvic organs & integument
  • Formed from several smaller veins in region
  • Flows into common iliac vein (16h)

Middle sacral vein:


  • Drains sacral region
  • Flows into L-common iliac vein (16h)

Common iliac vein:


  • Flows into inferior vena cava (1g) at level L5
  • L-common iliac vein drains sacral region
  • Formed from union of external and internal iliac veins (13h & 14h) near inferior portion of sacroiliac joint'