________carry blood away from the heart to the tissues.
What does the wall of an artery consist of?
*tunica media(which maintains elasticity and contractility
Many arteries anastomose, what does that mean?
The distal ends of two or more vessels unite. Anastomoses between arteries provide alternate routes for blood to reach a tissue or organ. Thus, if a vessel is blocked by disease, injury, or surgery, circulation to a part of the body is not necessarily stopped.
What is an alternate blood route from an anastomose called?
What are arteries that do not anastomose called?
What happens if there is an occlusion of an end artery?
It interrupts the blood supply to a whole segment of an organ, producing necrosis(death) of that segment.
Very small, almost microscopic, arteries that deliver blood to capillaries.
How do arterioles assume a key role in regulating blood flow from arteries into capillaries and in altering arterial blood pressure?
Through vasoconstriction(decrease in the size of the lumen of a blood vessel) and vasodialation(increase in the size of the lumen of a blood vessel)
Microscopic blood vessels through which materials are exchanged between blood and tissue cells.
What do capillaries connect?
They usually connect arterioles and venules.
What are capillary walls composed of?
A single layer of cells(endothelium) and a basement membrane.
Capillaries branch to form an extensive network throughout the tissue. What is the purpose of this?
The network increases the surface area, allowing a rapid exchange of large quantities of materials.
How is the flow of blood through capillaries regulated?
By vessels with smooth muscle in their walls.
What are the rings of smooth muscle fibers(cells) that regulate blood flow through true capillaries called?
What are two types of capillaries?
continuous and fenestrated
What are microscopic blood vessels in organs such as the liver, spleen, and bone marrow called?
They are wider than capillaries, more tortuous, and specialized for the functions of the specific organs.
Small vessels that are formed from the union of several capillaries.
What do venules merge to form?
What do veins consist of?
The same thress tunics as arteries, but have a thinner tunica interna and media and a thicker tunica externa. They have less elastic tissue and smooth muscle and are therefore thinner-walled than arteries.
What do veins contain?
Valves to prevent backflow of blood.
What can weak valves lead to ?
Veins with very thin walls with no smooth muscle to alter their diameters. Examples are the brain's superior sagittal sinus and the coronary sinus of the heart.
At rest, where is the largest portion of the blood volume?
Systemic veins and venules, collectively called blood reservoirs.
What happens in cases of hemorrhage?
When blood pressure and volume decrease, vasoconstriction of veins in venous reservoirs helps to compensate for the blood loss.
What are the principle reservoirs?
The veins of the abdominal organs(liver and spleen) and skin.
The volume of blood that flows through any tissue in a given period of time.
The ___________ of blood flow is inversely related to the cross-sectional area of blood vessels.
Velocity; Blood flows most slowly where cross-sectional area is greatest.
Blood flow ___1____ from the aorta to arteries to capillaries and ___2____ as it returns to the heart.
Blood flow is determined by ______ _____and _____.
blood pressure and resistance
How does blood flow?
From regions of higher to lower pressure; the higher the resistance the lower the blood flow.
What is cardiac output (CO) equal to?
Mean aortic blood pressure(MABP) divided by total resistance(R):
The pressure exerted on the walls of a blood vessel.
Blood Pressure (BP)
In clinical use, BP refers to pressure in the arteries.
What are factors that affect blood pressure?
*Elasticity of arteries
As blood leaves teh aorta and flows through systemic circulation, its pressure progressively falls to __ mm Hg by the time it reaches the right atriam.
_______ refers to the opposititon to blood flow as a result of friction between blood and the walls of the blood vessels.
Resistance depends on what?
*Blood vessel length
*Blood vessel radius
_____ ______ ______ refers to all of the vascular resistances offered by systemic blood vessels; most resistance is in arterioles, capillaries, and venules due to their small diameters.
Systemic Vascular Resistance (SVR) (also known as total peripheral resistance)
How do substances enter and leave capillaries?
*Vesicular transport(endocytosis and exocytosis)
*Bulk flow(filtration and absorption)
The movement of water and dissolved substances(except proteins) through capillaries is dependent upon _____ and _____ _____.
Hydrostatic and osmotic pressures
Which type of pressure is being used when the heart beats and blood moves?
Which type of pressure is being used when the heart relaxes?
Which type of pressure is greater hydrostatic or osmotic?
The near equilibrium at the arterial and venous ends of a capillary by which fluids exit and enter is called what?
Starling's law of the capillaries
amount+speed going in=amount+speed going out
(except when edema is present)
Occasionally, the balance of filtration and reabsorption between interstitial fluid and plasma is disrupted, allowing an abnormal increase in the interstitial fluid called _____.
Edema may be caused by several factors. Name 5.
1.Increased blood hydrostatic pressure in capillaries due to an increase in venous pressure.
2.Decreased concentration of plasma proteins that lower blood colloid osmotic pressure.
3.Increased permeability of capillaries, allowing greater amounts of plasma proteins to leave the blood and enter tissue fluid.
4.Increased extracellular fluid volume as a result of fluid retention.
5.Blockage of lymphatic vessels postoperatively or due to filarial worm infection.
Name two factors that aid venous return.
*The volume of blood flowing back to the heart from systemic veins
*By increasing the magnitude of the pressure gradient between the venules and the right atrium
Blood return to the heart is maintained by several factors. Name 3.
*skeletal muscle contractions
*valves in the veins(especially in the extremities)
*pressure changes associated with breathing
A group of neurons in the medulla that regulates heart rate, contractility , and blood diameter.
The cardiovascular(CV) center
Where does the CV center receive input from?
higher brain regions and sensory receptors(baroreceptors and chemoreceptors)
Where does output from the CV center flow along?
Sympathetic and parasympathetic fibers
sympathetic impulses along _____ _____ increase heart rate and conrtactility.
Parasympathetic impulses along _____ _____ decrease heart rate.
The sympathetic divison also continually sends impulses to smooth muscle in blood vessel walls via _____ _____. The result is a moderate state of tonic contraction or vasoconstriction, called_____ _____.
Important pressure-sensitive sensory neutons that monitor stretching of the walls of blood vessels and the atria.
The _____ _____ _____ is concerned with maintaining normal blood pressure in the brain and is initiatd by baroreceptors in the wall of the carotid sinus.
Cardiac sinus reflex
The _____ _____ is concerned with general systemic blood pressure and is initiated by baroreceptors in the wall of the arch of the aorta or attached to the arch.
What happens if blood pressure falls?
The baroreceptor reflexes accelerate heart rate, increase force of contraction, and promote vasoconstriction.
The _____ _____ _____ responds to increases in venous blood pressure and is initiated by baroreceptors in the right atrium and venae cavae.
Right heart (atrial) reflex
Receptors sensitive to chemicals are called_____.
What do chemoreceptors monitor?
Blood levels of oxygen, carbon dioxide, and hydrogen ion concentration.
Several hormones affect blood pressure and flow by acting on the heart, altering blood vessel diameter, or adjusting the total blood volume. Among the hormones that help regulat3eblood pressure are__1___,__2___,___3__ _____,__4___,___5__ _____ _____,___6__,and __7___.
5.atrial natriuretic peptide(ANP)
In most body tissues, oxygen is the principal, though not direct, stimulus for _____.
_____,or faint, refers to a sudden temporary loss of consciousness followed by spontaneous recovery. It is most commonly due to cerebral ischemia(lack of sufficient blood flow).
_____ is an inadequate cardiac output that results in failure of the cardiovascular system to deliver adequate amounts of oxygen and nutrients to meet the metabolic needs of body cells.
What can result from this condition?
As a result, cellular membranes dysfunction, cellular metabolism is abnormal, and cellular death may eventually occur without proper treatment.
What are the signs and symptoms of shock?
*clammy, cool, pale skin
*weak, rapid pulse
*hypotension(systemic pressure < 90 mm Hg)
*altered mental status
*decreased urinary output
What are the stages of shock characterized by?
inadequate perfusion of tissues
_____ _____ refers to decreased blood volume resulting from loss of blood or plasma due to acute hemorrhage or excessive fluid loss(as in excess vomiting, diarrhea, sweating, dehydration, urine production, and burns).
The development of shock occurs in _____ principle stages, which merge with one another.
What is Stage I of shock?
Compensated (nonprogressive) shock, in which negative feedback systems restore homeostasis.
1.If the initiating cause does not get any worse, a full recovery follows.
2.Compensatory adjustments include activation of the sympathetic division of the ANS, the renin-angiotensin pathway, release of antidiuretic hormone(ADH), and release of vasodilator factors in response to hypoxia.
What is Stage II of shock?
Decompensated(progressive)shock, in which positive feedback cycles intensify the shock and immeadiate medical intervention is required.
1.It occurs when there has been a reduction in blood volume of 15-25%.
2.Among the positive feedback cycles that contribute to decreased cardiac output and blood pressure are depression of cardiac activity, depression of vasoconstriction, increased permeability of capillaries, intravascular clotting, cellular destruction, and acidosis.
What is Stage III of shock?
Irreversible shock, in which there is rapid deterioration of the cardiovascular system than cannot be helped by compensatory mechanisms or medical intervention.
_____ is the alternate expansion and elastic recoil of an artery wall within each heartbeat.
Where can the pulse be felt?
It may be felt in any artery that lies near the surface or over a hard tissue, and is strongest in the arteries closest to the heart.
The _____ ______ is the most commonly used to feel the pulse.
What is a normal resting pulse(heart)rate?
Between 70 and 80 beats per minute.
Tachycardia means a rapid resting heart or pulse rate of what?
> 100 beats per minute
Bradycardia indicates a slow resting heart or pulse rate of what?
< 60 beats per minute
_____ _____ is the pressure exerted by blood on the wall of an artery when the left ventricle undergoes systole and then diastole.
How is blood pressure measured?
By the use of a sphygmomanometer usually in one of the brachial arteries.
_____ _____ _____ is the force of blood recorded during ventricular contraction.
Systolic blood pressure(SBP)
_____ _____ _____ is the force of blood recorded during ventricular relaxation.
Diastolic blood pressure(DBP)
The various sounds that are heard while taking blood pressure are called _____ _____.
What is the normal pressure of a young adult male?
120/80 mm Hg
_____ _____ is the difference between systolic and diastolic pressure. It normally is about 40 mm Hg and provides information about the condition of the arteries.
What is the largest circulatory route?
the systemic system
What are five of the several subdivisions of the systemic circulation?
(1)coronary(cardiac)circulation-supplies the myocardium of the heart
(2)cerebral circulation-which supplies the brain
(3)hepatic portal circulation-extends from the gastrointestinal tract to the liver
The _____ _____ takes oxygenated blood from the left ventricle through the aorta to all parts of the body, including some lung tissue(but does NOT supply the air sacs of the lungs) and returns the deoxygenated blood to the right atrium.
What are the divisions of the aorta?
*arch of the aorta
Blood vessels develop from isolated masses of mesenchyme in the mesoderm called _____ _____.
Blood plasma and blood cells are produced by the _____ _____ of blood vessels, a function later assumed by the liver,spleen, bone marrow, and lymph nodes.
What is the most common disease affecting the heart and blood vessels? It is classified as primary(essential) or secondary.
Hypertension, or high blood pressure
_____ _____ is a persistently elevated blood pressure that cannot be attributed to any particular organic cause.
primary(essential) hypertension (approximately 90-95% of all hypertension cases)
Only _____ _____ has causes that are identifiable.
What are two of these causes?
kidney disease and adrenal hypersecretion
An _____ is a think, weakened section of the wall of an artery or a vein that bulges outward, forming a balloon like sac of the blood vessel.
What can happen if an aneurysm is left untreated?
It may burst, causing massive hemorrhage with shock, severe pain, cardiovascular accident(CVA, or stroke), or death.
_____ _____ _____ is a condition in which the heart muscle receives inadequate oxygen due to blockage of its blood flow.
Coronary artery disease (CAD)
_____-_____ _____ is a blood clot (thrombus) in a deep vein, especially in the lower extremities.
What are two serious complications of deep-venous thrombosis?
pulmonary embolism and postphlebitic syndrome
What are the three areas of heart problems?