Flashcards in Cardiovascular System Deck (37):
What is the Frank-Starling curve?
The Frank-Starling curve shows the relationship between the stroke volume and the ventricular end-diastolic volume. It states that the larger volume of blood in the ventricles, the larger the stroke volume up to a point. After this point, the actin and myosin are no longer perfectly aligned so stroke volume begins to decrease.
What therapies help to reduce the preload on the heart?
Diuretics help to reduce the preload on the heart. This means that the point at which the stoke volume begins to decrease as end diastolic volume increased gets larger. This prevents the ventricles from being damages and expanding.
What is pulmonary oedema?
Pulmonary oedema is when we get fluid in the alveoli of our lungs. When listening with a stethoscope, this sounds bubbly or crackly. It is dangerous for patients with this to lie flat because it will increase venous return so they will struggle to breath. (More fluid will accumulate because gravity.)
Why does left ventricular failure lead to pulmonary oedema?
Failure in the left ventricle causes blood to accumulate in the pulmonary veins. This produces a rise in blood pressure in these veins. If these rise is sustained then it will force fluid form the blood into the alveoli to reduce BP. This also leads to difficulty providing adequate oxygen to the body.
What is paroxysmal nocturnal dyspnoea?
This is a sensation of shortness of breath that awakens the patient after about 1-2 hours of sleep and is usually relived in the upright position.
What is orthopnea?
This is the sensation of breathlessness in the recumbent position. It is relived by sitting or standing
What is left ventricular hypertrophy?
This is the thickening of the mayocardium of the left ventricle. It is dangerous because the left wall becomes more powerful but, there is reduced space which leads to reduced stroke volume.
What is fixed mottling?
This is caused by a lack of blood supply to the affected limb (ischaemia). Initially, the leg will go white because there is no blood. Next, as cells necrose, there is dilation of blood vessels so the limb goes brown. But, since there is no more blood supply, the blood will congeal (go black) which creates the mottling effect.
What could be measured in the blood of urine which might result from the dead muscle in the leg? Why does the limb need to be amputated quickly?
The patient will have raised myoglobin and really increased Creatine Kinase. This also will release potassium into the blood which can cause lots of problems if kidney and heart failure so, to stop this, the limb must be amputated.
What is the role of the cardiovascular system?
The cardiovascular system circulates and transports nutrients, oxygen, carbon dioxide, hormones and blood cells to and from the cells of the body.
It also fights disease, stabilises temperature and pH and helps maintain general homeostasis.
What are the essential components of the human cardiovascular system?
Heart, blood and blood vessels.
What is the pulmonary circulation loop?
This is the “loop” through the lungs where blood is oxygenated.
What is the systemic circulation loop?
This is a “loop” though the rest of the body to provide oxygenated blood and receive deoxygenated blood.
How much blood does the average adult have? What amount g this is red blood cells? Plasma?
The average adult has 5L of circulating blood of which 2L is red blood cells and 3L is plasma.
Where doe s most of our blood lie?
An bag human has 5L of blood. 3.25L will be in the veins, 1L will be in the heart and lungs, 0.5L will be in the peripheral arteries, 0.25L will be in capillaries but have by far the greatest surface ares for substance exchange.
What is an end artery?
An end artery is a terminal artery supplying all or most of the blood to a curtain part of the body without significant collateral circulation (an alternative pathway for blood to flow).
Eg splenic arteries, coronary arteries, cerebral arteries and renal arteries.
What happens in elastic arteries during systole?
Left ventricle contraction causes the blood pressure in the aorta to rise to approximately 120mmHg (systolic pressure). The walls of the elastic aorta (and other elastic arteries) stretch.
What happens to the arteries during diastole?
The aortic semilunar valve closes. The walls of the aorta recoil, maintaining the pressure on the blood and moving it towards the heart and smaller vessels. Aortic pressure drops to 70-80mmHg (diastolic pressure).
So, during diastole, the elastic arteries act as auxiliary pumps giving back the energy stored during systole. They are sometimes called capacitor vessels.
What are are three layers in the walls of arteries and veins?
Tunica intima next to the lumen
Tunica media in the middle
Tunica adventitia as the outer layer
What is an aneurysm and where do they most commonly occur?
An aneurysm is a dilation of a blood vessels. The most common site for an aneurysm is the infrarenal abdominal aorta (an anatomical weak spot).
What are the main layers in the tunica intima?
Endothelium, subendothelial layer, thick internal lamina.
What is the main feature of the tunica media?
40 layers of smooth muscle cells. These cells are connected by gap junctions for coordinated contraction. There is also a prominent external elastic lamina.
What is the main feature of the tunica adventitia?
A thin layer of fibroelastic connective tissue contains vasa vasorum (not very prominent), lymphatic vessels and nerve fibres.
How is vasoconstriction stimulated?
Vasoconstriction is stimulated by the sympathetic nerve fibres. Neurotransmitter (noradrenaline) is released at the endings and it diffuses though fenestrations in the external elastic lamina into the external tunica media. This depolarised some of the superficial smooth muscle cells. This depolarisation is propagated to all cells of the tunica media via gap junctions.
What are arterioles?
Arterioles are arteries with a diameter of less than 0.1mm. Arterioles have only one to three layers of smooth muscle in their tunica media.
What are metarterioles?
These are arteries that supply blood to capillary beds.
What is a precapillary sphincter?
These are individual muscle cells that are spaced apart and each encircle the endothelium of a capillary arising form the metateriole.
Each separate smooth muscle cells is believed to function as a sphincter, upon contraction, controlling blood flow into the capillary bed.
When the precapillary sphincter are open, there is a plentiful blood flow though the capillary bed whereas, when they are closed, the blood flow to the capillary bed is greatly reduced.
What are Capillaries and how are they adapted for gas exchange?
A capillary is a tube to allow the passage of one blood cell at a time. This minimises diffusion path and significantly increases surface area to allow for efficient gas exchange. Blood also travels quite slowly through capillaries and they made of a single layer of endothelium and its basement membrane. These things further increase the effectiveness of diffusion in capillaries.
What are pericytes?
Pericytes are contractile cells that wrap around the endothelial cells that line the capillaries and venules throughout the body. They form a branching network on the outer surface of the endothelium. They are capable of dividing into muscle cells or fibroblasts during angiogenesis (development of new blood vessels), tumour growth and wound healing.
What are post capillary venules?
They are blood vessels that receive blood from the capillaries and are even more permeable than the capillaries. Their wall is similar to that of capillaries with an endothelial lining and associated pericytes.
Does fluid flow into or out of post capillaries venules? When is there an exception to this rule?
Fluid drains into them. This is because their pressure is lower than that of the capillaries or surrounding tissue.
But, when an inflammatory response is operating, fluid and leukocytes emigrate.
Postcapillary venules are the preferred location for emigration if leukocytes from the blood.
What is different between the structure of veins and the structure of arteries?
Veins have a larger diameter than any accompanying artery. They also have a thinner wall that has more connective tissue and fewer elastic tissue and muscle fibres.
What are differences between small and large veins?
Small and medium sized veins have a well developed adventitia. The tunica intima is thin as is the tunica media (it is only 2 or 3 layers of smooth muscle).
Whereas in large veins (vein eight diameter of more than 10mm) the tunica intima is thicker. Also, most large veins do not have a well developed tunica media but have a well developed tunica adventitia.
What veins are the exception to their expected structure?
The exception are the superficial veins of the leg. These have a well defined muscular wall, possibly to resist distension caused by gravity.
What is capacitance and what are veins known as capacitance vessels?
Capacitance is defined as the ability of a blood vessel to increase the volume of blood it holds without a significant increase in pressure. It is inversely proportional to elasticity.
Veins are capacitance vessels because they have a thin, non-elastic wall so they can stretch a great deal.
How does venous blood get from the legs back to the heart in a standing human?
The calf muscle acts as a pump for deep leg veins. Blood flow is caused by its contraction. Also, the valves present in the veins prevent backflow when the muscles are relaxed.