Flashcards in 13 - Blood Vessels and Circulation Deck (75):
What are the functions of the circulatory system?
1. Carry blood
2. Exchange nutrients, waste products, and gases with tissues.
3. Transports substances.
4. Helps regulate blood pressure
5. Directs blood flow to the tissues.
Blood vessels outside the heart are divided into two classes:
Pulmonary vessels, which transport blood to the lungs and back to the heart, and the Systemic vessels which transport blood through all parts of the body.
Blood flows through different types of arteries and veins. Name them, starting with the heart.
Arteries - Small Arteries - Arterioles -Capillaries - Venules - Small Veins - Veins
The tunics are the three layers of blood vessel walls. These are present in all but which types of blood vessels?
Tunics are not present in the capillaries and venules.
Name the three different layers of the tunics.
1. Tunica intima, 2. Tunica media, 3. Tunica externa/adventitia
Describe the structure of the tunica intima, the innermost of the tunics.
Consists of an endothelium composed of simple squamous epihelial cells, a basement membrane, and a small amount of connective tissue.
Describe the structure of the tunica media, the middle layer of the tunics.
Consists of smooth muscle cells arranged circularly around the blood vessel. It also contains variable amounts of elastic and collagen fibers.
Describe the structure of the tunica externa/avdentitia
Composed of dense connective tissue, the tissue becomes loose connective tissue toward the outer portion of the blood vessel wall.
The arteries can be divided into two different types. Which?
The elastic arteries and the muscular arteries.
What are the physical properties of elastic arteries?
Elastic arteries are the largest-diameter arteries and have the thickest walls. Compared to other arteries, a greater proportion of their walls is composed of elastic tissue.
What are the functions of elastic arteries?
The elastic recoil of these arteries prevents blood pressure from falling rapidly and maintains blood flow while the ventricles are relaxed.
What are the physical properties of muscular arteries?
The walls are relatively thick compared to heir diameter. Most of the wall's thickness results from smooth muscle cells of the tunica media.
Another name for muscular arteries is distributing arteries. Why?
Because the smooth muscle tissue enables these vessels to control blood flow to different body regions.
What is vasoconstriction?
The contraction of smooth muscle in blood vessels. Decreases blood flow.
What is vasodilation?
The relaxation of smooth muscle in blood vessels. Increases blood flow.
How is blood flow in the capillaries regulated?
By precapillary sphincters located at the origin of the capillary branches.
What are the physical properties of capillaries?
They consists of endothelium walls, which is a layer of simple squamous epithelium surrounded by a delicate loose connective tissue. Also have precapillary sphincters.
What are the physical properties of venules?
They do not have the tunic structure, but constists of endothelium resting on a delicate connective tissue layer.
Which veins have valves?
Those that have a diameter of more than 2mm.
Describe the blood vessels of the pulmonary circulation. Mention the names of the vessels and the exit and entrance to the heart.
Blood from the right ventricle is pumped into a short vessel called the pulmonary trunk. The pulmonary trunk then branches into the right and left pulmonary arteries, each extending to its own lung. Four pulmonary veins exit the lungs and carry the oxygen-rich blood to the left atrium.
What are varicose veins? På norsk: Åreknuter.
Varicose veins result when the veins of the lower limbs become so dilated that the cusps of the valves no longer overlap to prevent the backflow of blood.
Explain how varicose veins can be dangerous to your health.
The blood in varicose veins can become so stagnant that it clots, creating tromboses. Can cause inflammation of the veins, phlebitis(årebetennelse). Can also lead to an infection by anaerobic bacteria: gangrene(koldbrann).
What is an arterial aneurysm?
A localized dilation of an artery that usually develops in response to trauma or a congenital weakness of the artery wall. Rupture of a large aneurysm in the aorta is almost always fatal.
A condition existing at birth. Medfødt lidelse.
The aorta is usually considered in three parts, which?
The ascending aorta, the aortic arch, and the descending aorta.
What is a portal system?
A vascular system that begins and ends with capillary beds and has no pumping mechanism, such as the heart.
What is "the coronary bypass surgery"?
Portions of the great saphenous vein (the vein on the inside of each foot), are grafted to create a route for blood flow that bypasses blocked portions of the coronary arteries. Sometimes the femoral vein is used instead.
What is blood pressure?
Blood pressure is a measure of the force blood exerts against the blood vessel walls. The standard unit for measuring blood pressure is millimeters of mercury (mm Hg).
In arteries, blood pressure values go through a cycle that depends on the rythmic contractions of the heart. Which two types of pressure?
Systolic pressure, when the ventricles contract. Diastolic pressure when the ventricles relax.
Systolic pressure is when the ventricles are...
Diastolic pressure is when the ventricles are...
What is the auscultatory method?
A method to determine blood pressure.
Explain how the auscultatory method works.
A blood pressure cuff is wrapped around the patient's arm, and a stethoscope is placed over the brachial artery. No sound is heart because the artery is completely blocked. Then, gradually, pressure is lowered. As soon as the pressure in the cuff declines below the systolic pressure, blood flows through the constricted area and a sound can be heart. The pressure at which the first sound is heart is the systolic pressure.
What is hypertension? (Norsk: Hypertensjon/Høyt blodtrykk)
Blood pressure above normal values. Hypertension requires the heart to perform a greater-than-normal amount of work because of the increased afterload. The extra work leads to hypertrophy of cardiac muscle, especially in the left ventricle, and can result in heart failure. Also increases the rate of arteriosclerosis development.
What is a normal blood pressure value?
Less than 120mm Hg systolic, and 80 mm Hg diastolic
What is the greatest factor contributing to the decrease of blood pressure as the blood circulates?
The diameter of the vessel.
Blood pressure is very low in the veins. How does blood continue to flow into the heart?
1. Valves that prevent the backflow, 2. skeletal muscle movements that periodically compress veins.
What is the pulse pressure?
The difference between the systolic and diastolic pressures. I.E: 120 mm Hg sys, 80 mm Hg dia = 40 mm Hg pulse pressure.
Which two factors affect pulse pressure?
Stroke volume(slagvolum), and vascular compliance.
What is stroke volume?
The amount of blood pumped by each contraction of the heart.
What is vascular compliance?
The elasticity of the blood vessel wall.
What is arteriosclerosis?
A hardening of the artieries. Arterial pressure in this condition will increase rapidly and fall rapidly. This effects blood pressure because it substantially increases the systolic pressure. This also leads to a greater load on the heart, because the heart must produce such high pressure.
Not only nutrients diffuse through the capillary wall. Fluid also moves out in the arterial end, and in the venous end. What makes this possible?
In the arterial end the blood pressure is the main cause of fluid movement out of the capillaries. In the venous end, fluid moves into the capillaries due to the osmotic pressure of the blood - the blood contains a large concentration of plasma proteins.
Where does the fluid that exits the capillaries go?
Approximately 9/10 of the fluid reenters the capillary at its venous end. The remaining 1/10 enters the lymphatic capillaries and is eventually returned to the general circulation.
What is an edema?
Explain how inflammation causes edema.
Inflammation increases the permeability of capillaries. Proteins, mainly albumin, leak out of the capillaries into the interstitial spaces. This upsets the normal osmotic balance, resulting in less of the fluid returning to the capillaries.
Mechanisms that control blood flow through tissues are classified as..
1. local control
2. nervous and hormonal control.
How is local control of blood flow achieved?
Through the contraction and relaxation of the precapillary sphincters. These react to many different states of the tissue spaces: by-product concentration, concentration of oxygen & nutrients, carbondioxide, decreases in pH, and so on.
Most blood vessels of the body, except the capillaries, are innervated by nerve cells. What structure in the brain is responsible for the mediation of blood pressure?
The vasomotor center in the medulla oblongata.
What is vasomotor tone?
The vasomotor center in the medulla oblongata continually transmits a low frequency of action potentials to the sympathetic nerve fibers. As a consequence, the peripheral blood vessels are continually in a partially constricted state, a condition called vasomotor tone.
Why is the mean arterial blood pressure, MAP, less than the average of the diastolic and systolic pressures?
It is slightly less that the average of the systolic and diastolic pressures, because the diastole lasts longer than the systole.
What is the body's MAP (mean arterial blood pressure).
MAP = CO x PR ; where CO is the cardiac output, and PR is the peripheral resistance.
What is the cardiac output?
CO = HR x SV ; where HR is heart rate and SV is stroke volume.
Explain the formula: MAP = HR x SV x PR
The main arterial blood pressure, MAP, is equal to the heart rate times the stroke volume times the peripheral resistance. This means that if any of those factors increase, so does the blood pressure. During hemorrhage (blødning), the heart can increase its rate to counter the loss of blood pressure.
What are baroreceptors?
Receptors that are scattered along the walls of most large arteries of the neck and thorax, in the carotid sinus and the base of the aortic arch. They respond to the stretch in arteries cause by increased pressure. Action potentials travel from the baroreceptors to the medulla oblongata.
What are the functions of carotid and aortic bodies?
They are chemoreceptors that are sensitive to extreme changes in blood oxygen / carbon dioxide -concentrations. As a part of the chemoreceptor reflex they innervate vasomotor and cardiovascular centers of the medulla oblongata, which in turn can increase heart rate, stroke volume and vasomotor tone.
List the four important hormonal mechanisms that help control blood pressure.
1. Adrenal Medullary Mechanism
2. Renin-Angiotensin-Aldosterone Mechanism
3. Antidiuretic Hormone Mechanism
4. Atrial Natriuretic Mechanism.
What is the Adrenal Medullary Mechanism?
An important hormonal mechanism that help control blood pressure by release of epinephrine and norepinephrine by the adrenal medulla.
What is the Renin-Angiotensin-Aldosterone Mechanism?
An important hormonal mechanism that help control blood pressure by the kidneys releasing the hormone renin. Renin acts on the blood protein angiotensinogen to produce angiotensin I. Large organs have enzymes that convert angiotensin I into angiotensin II, which is a potent vasoconstrictor. Angiotensin II also acts of th eadrenal cortex to increase the secretion of aldosterone, which decreases the amount of water the kidneys remove from the blood.
What is the Antidiuretic Hormone Mechanism?
An important hormonal mechanism that help control blood pressure by the hypothalamus secreting ADH /vasopressin. ADH acts on the kidneys and causes them to absorb more water, this helps maintain blood volume and blood pressure.
What is the Atrial Natriuretic Mechanism?
An important hormonal mechanism that help control blood pressure by the secretion of atrial natriuretic hormone from specialized cells in the right atrium in response to elevated blood pressure. It causes the kidneys to promote the loss of Na+ and water in urine, increasing urine volume. This causes a loss in blood volume, decreasing blood pressure.
What is a circulatory shock?
An inadequate blood flow throughout the body that causes tissue damage due to lack of O2.
What is meant by circulatory shock sometimes causing a positive-feedback cycle?
In the most severe cases of shock, the regulatory mechanisms are not adequate to compensate for the effects. As a consequence, a positive-feedback cycle begins to develop: the blood pressure regulatory mechanisms lost their ability to control the blood pressure, and shock worsens. As the shock becomes worse, the effectiveness of the regulatory mechanisms deteriorates even further.
Five types of shock are classified based on their cause. Mention them:
1. Hypovolemic shock, 2. Neurgenic shock, 3. Anaphylactic shock, 4. Septic shock, 5. Cardiogenic shock.
What is an hypovolemic shock?
A shock as a result of reduced blood volume. Can be cause by hemorrhage, plasma loss, or insterstitial fluid loss.
What is a neurogenic shock?
A shock caused by vasodilation in response to emotional upset of anesthesia.
What is an anaphylactic shock?
A shock caused by an allergic response that results int he release of inflammatory substances that cause vasodilation and increased capillary permeability. Large amounts of fluid move into the interstitial spaces.
What is a septic shock?
A shock caused by infections that release toxic substances into the circulatory system. (norsk: blodforgiftning). This also leads to vasodilation and increased capillary permeability.
What is a cardiogenic shock?
A shock caused by a decrease in cardiac output as a result of events that decrease the heart's ability to function. Hear attack is a common cause of cardiogenic shock.
What is atherosclerosis?
Atherosclerosis results from the deposition of material in the walls of arteries that form plaques. The material is composed of fatlike substances containing cholesterol. The fatty material can eventually be dominated by the deposition of dense connective tissue and calcium salts. Atherosclerosis greatly increases resistance to blood flow. It can also cause trombosis.
What are the risk factors of atherosclerosis?
Lack of exercise, smoking, obesity, genes, and a high-cholesterol/fats diet.
High blood pressure can be cause by advanced atherosclerosis of the renal arteries, even though blood flow appears sufficient to allow a normal volume of urine to be produced. Explain how atherosclerosis of the renal arteries can result in high blood pressure.
Reduced blood flow to the kidney stimulates renin secretion. Renin acts on angiotensinogen to produce angiotensin I. Angiotensin I is converted to angiotensin II by the action of angiotensin-converting enzyme. Angiotensin II causes vasoconstriction, which increases blood pressure. In addition, angiotensin II stimulates the secretion of aldosterone from the adrenal cortex. Aldosterone acts on the kindey, causing the reabsorption of Na+ and water, thus increasing blood volume . The increased blood volume results in increased blood pressure.
Hugo Faster ran a race during which his stroke volume and heart rate increased. Vasoconstriction occurred in his viscera, and his blood pressure rose, but not dramatically. Explain these changes in the circulatory system.
During exercise, vasoconstriction occurs in the viscera, but vasodilation occurs in the exercising muscles. Even though cardiac output in increased because of the increased stroke volume and heart rate, the blood pressure does not go up as much as it would if vasoconstriction occured in the viscera without vasodilation of the blood vessels in the exercising skeletal muscles.
Nitroglycerin is often given to people who experience angina pains. This drug causes vasodilation of arteries and veins, which reduces the amount of work the heart performs and increases blood flow through the coronary arteries. Explain why dilation of arteries and veins reduces the heart's amount of work.
Dilation of arteries and veins allows blood to accumulate in the dilated blood vessels. Consequently, less blood is returned to the heart (decreased venous return). Because the venous return is reduced, the stroke volume of the heart decreases. Consequently the heart does less work and less O2 is required to support the contraction of the heart. Therefore, angina pains, which are cause by inadequate O2 delivery to the heart muscle, are reduced.