Ch. 13 - The Vascular System Flashcards
Arteries
Describe what arteries are, 3 layers, and perfusion
- Arteries carry blood from the heart to capillaries; smaller arteries are called arterioles. Layers:
- Tunica intima = inner layer that touches blood. Made of simple squamous epithelium (i.e., the endothelium that is also found in the endocardium heart chambers) = smooth = prevents blood clots. Also produces Nitric Oxide (No) = vasodilator (relaxes tunica media layer) and Endothelin (peptide) = vasoconstrictor (balance of the two = maintaining BP)
- Tunica media = middle layer of elastic connective tissue responsible for vasoconstriction and vasodilation d/t chemicals and nerve impulses
- Tunica externa = outer layer - strong fibrous - prevents burstin d/t increased BP
- For the terminal arterioles, those just before capillary networks, the level of oxygen in the surrounding tissue is a regulating factor. Hypoxia in tissues causes systemic arterioles to dilate, which will increase blood flow, called perfusion, to correct the hypoxia. In contrast, pulmonary terminal arterioles constrict in response to hypoxia.
Veines
Describe what veins are 3 layers
- Veins carry blood from capillaries back to the heart; the smaller veins are called venules. Same 3 tissue layers as arteries with a few differences:
- Tunica interna = also has intervals of lining folded to form valves, which prevent backflow
- Tunica media = does not regulate blood pressure, because it’s a lot thinner, but can also constrict a lot to help with hemorrhages
- Tunica externa = also thinner
- Veins have a larger total volume of blood
Anastomoses
Describe what Anastomosis are
Anastomosis is a connection artery to artery or vein to vein, which provides alternative pathways for the flow of blood (like a junction)
Disorders of Arteries
Describe: Arteriosclerosis, Aneurysm, Atherosclerosis
- Arteriosclerosis - arteries lose their elasticity, and their walls become weakened - part of the aging process
- Aneurysm - a weak portion of an arterial wall may bulge out forming a sec or bubble
- Atherosclerosis - buildup of fats, cholesterol and other substances in and on artery walls (called plaque), which causes arteries to narrow, blocking blood flow. The plaque can also burst, leading to a blood clot.
Disorders of Veins
Describe: Phlebitis, Varicose veins
Phlebitis - inflammation of a vein
Varicose veins - swollen and distended veins that occur most often in the superficial veins of the legs. Varicose veins of the anal canal are called hemorrhoids.
Capillaries
Describe what Capillaries are/how they function, Precapilarry sphincters, and sinusoids
- Capillaries carry blood fro arterioles to venules. Their walls are only one cell in thickness; capillaries are actually the extension of the endothelium, the simple squamous lining of arteries and veins. Some issues do not have capillaries; these are the epidermis, cartilage, and the lens and cornea of the eye.
- Blood flow into capillary networks is regulated by smooth muscle cells called precapillary sphincters.These are regulated by the needs of the tissues (automatic responses)
- Some organs have another type of capillary called sinusoids, which are larger and more permeable than are other capillaries - found in the red bone marrow and spleen, where blood cells enter or leave the blood, and in organs such as the liver and pituitary gland, which produce and secrete proteins into the blood.
Exchanges in Capillaries
Describe Diffusion, Filtration, Colloid Osmotic Pressure (COP)
- Gasses move by diffusion, that is, from their area of greater concentration to their area of lesser concentration (O2 from blood to tissue and CO2 from tissue to blood).
- Because the capillary blood pressure is higher, the process of filtration occurs, which forces plasma and dissolved nutrients out of the capillaries and into tissue fluid.
- Albumin contributes to the colloid osmotic pressure (COP) of blood; this is an ‘attracting’ pressure. As the venous end of capillaries, the presence of albumin in the blood pulls tissue fluid into the capillaries, which also brings into the blood the waste products produced by cells.
Pathways of Circulation
Describe: Pulmonary circulation, Systemic circulation, Hepatic protal circulation, and Fetal circulation
- Pulmonary circulation = lungs. Pulmonary veins are the only veins that carry blood with a high oxygen content.
- Systemic circulation = rest of body. Some of the arteries in the head contribute to an important arterial anastomosis, the circle of Willis, which is a ‘circle’ of arteries around the pituitary gland.
- Hepatic portal circulation = digestive. Subdivision of systemic circulation in which blood from the abdominal digestive organs and spleen circulates through the liver before returning to the heart. Example: portal circulation takes blood from the stomach and intestine to the liver, the organ that can detoxify the alcohol and prevent its detrimental effect on the brain.
- Fetal circulation = baby. The site of exchange between fetus and mother is the placenta, which contains fetal and maternal blood vessels that are very close to one another. The umbilical arteries carry blood from the fetus to the placenta. In the placenta, carbon dioxide and waste products in the fetal blood enter maternal circulation, and oxygen and nutrients from the mother’s blood enter fetal circulation. The umbilical vein carries this oxygenated blood from the placenta to the fetus.
Pulse Sites
Describe: Pulse, Apical pulse, Pulse deficit
- A pulse is the heartbeat that is felt at an arterial site. What is felt is not actually the force exerted by the blood, but the force of ventricular contraction transmitted through the walls of the arteries.
- If the heart is beating weakly, a radial pulse may be lower than an apical pulse (listening to the heart itself with a stethoscope). This is called a pulse deficit and indicates heart disease of some kind.
- Abnormal rhythms may reflect cardiac arrhythmias, and the force of the pulse (strong or weak) is helpful in assessing the general condition of the heart and arteries.
Velocity of Blood Flow
Describe velocity of blood flow as it relates to capillaries
Capillaries = highest b(many branches) = blood flows more slowly = more time for nutrients/waste/gas exchange
Blood Pressure
Desecribe: Blood pressure, Systolic vs. Diastolic, Normal levels
- Blood pressure is the force the blood exerts against the walls of the blood vessels. Filtration in capillaries depends upon blood pressure.
- Systolic pressure is always the higher of the two and represents the blood pressure when the left ventricle is contracting. The lower number is the diastolic pressure, when the left ventricle is relaxed and does not exert force.
- As blood travels farther away from the heart, blood pressure decreases.
- Normal is 120/80. Lower = hypotension. Higher = hypertension.
- Pulmonary blood is always low. Important to prevent filtration in pulmonary capillaries, which in turn prevents tissue fluid from accumulating in the alveoli of the lungs.
Maintenance of Systemic Blood Pressure
Describe Venous Return
- Venous return - the amount of blood that returns to the heart by way of the veins. Venous return is important because the heart can pump only the blood it receives.
- Three mechanisms help promote venous return:
- Veins contain smooth muscle, which enables them to constrict and force blood toward the heart; the valves prevent backflow of blood.
- Skeletal muscle pump - deep veins of the legs - surrounded by skeletal muscles that contract and relax during normal activities such as walking. Contractions of the leg muscles squeeze the veins to force blood toward the heart.
- Respiratory pump affects veins that pass through the chest cavity. The pressure changes of inhalation and exhalation alternately expand and compress the veins, and blood is returned to the heart.
Maintenance of Systemic Blood Pressure
Describe Heart rate and force
Heart rate and force - in general, if heart rate and force increase, blood pressure increases; this is what happens during exercise
Maintenance of Systemic Blood Pressure
Describe Peripheral resistance
Peripheral resistance - this term refers to the resistance the vessels offer to the flow of blood - usually slightly constricted. This is why strenuous exercise should be avoided right after eating; there is not enough blood to completely supply oxygen to exercising muscles and an active digestive tract at the same time.
Maintenance of Systemic Blood Pressure
Describe Elasticity of the large arteries
Elasticity of the large arteries - when the left ventricle contracts, the blood that enters the large arteries stretches the arteries’ walls. The arterial walls are elastic and absorb some of the force. When the left ventricle relaxes, the arterial walls recoil or snap back, and this helps keep diastolic pressure within the normal range. Normal elasticity, therefore, lowers systolic pressure, raises diastolic pressure, and maintains a normal pulse pressure (pulse pressure is the difference between systolic and diastolic pressure)
