Ch 19 notes

Question 1

Pulmonary circulation

Answer 1

Heart and lungs

Question 2

Coronary circulation

Answer 2

Whole body

Question 3

All blood vessels except capillaries have three distinct layers, or tunics (“coats”) surrounding a central cavity called the lumen, through which blood flows. T

Question 4

Tunica Externa, media (myofibers to control diameter of RBC)

Question 5

Blood vessels can be classified into three major groups: (1) Vessels that transport blood away from the heart; these include arteries, arterioles, and metarterioles. (2) Capillaries are vessels where exchange of nutrients and wastes occur between the blood and surrounding tissues. (3) Vessels that transport blood back to the heart; these include thoroughfare channels, venules, and veins.

Question 6

Most arteries carry oxygenated blood (exceptions are pulmonary arteries and umbilical arteries).

Question 7

arteries have relatively thick tunics that allow them to withstand high hydrostatic pressure exerted by the blood flowing through their lumen. Arteries are classified anatomically as either elastic or muscular and are classified by function as either conducting or muscular.

Question 8

Elastic arteries are large-diameter vessels with thick walls and a significant amount of elastic tissue. Examples include the aorta, brachiocephalic, common carotid, subclavian, and common iliac. When the ventricles contract, blood rushing into elastic arteries causes them to stretch then recoil in an event called elastic rebound. The elastic rebound conducts the blood farther along the vessel even as the ventricles are relaxing. In this way, blood flow in the artery does not completely stop during ventricular diastole. Consequently, elastic arteries function as conducting arteries.
Muscular arteries are smaller-diameter vessels that transport blood between the larger elastic arteries and the smaller arterioles. The tunica media in these arteries is the thickest of all vessels; but they contain less elastic tissue than elastic arteries. Examples of muscular arteries include the brachial, mesenteric, femoral, and tibial. As a muscular artery approaches an organ, it branches to form smaller arteries and arterioles; thus, muscular arteries function as distributing arteries.

Question 9

Arterioles (ar-TĒR-ē-ōlz) appear more like capillaries as they approach the tissues they will feed. Large arterioles contain all three tunics, resembling a muscular artery, but the smallest arterioles may contain only smooth muscle and endothelium. Arterioles are the most important regulators of blood pressure. When stimulated by the sympathetic nervous system (SNS), the tunica media of most arterioles contracts, resulting in vasoconstriction. This event increases the resistance to blood flow in that region and, in turn, increases the pressure and blood flow “upstream” from the constricted arterioles. This is how the cardiovascular system can divert blood from one area of the body to another. A lack of stimulation would cause these arterioles to dilate.

Question 10

rterioles branch into smaller vessels called metarterioles that deliver blood to capillaries. They lack uniform muscular tunics, but they possess rings of smooth muscle called precapillary sphincters that regulate blood flow from a metarteriole into a capillary. These sphincters do not receive stimulation from the nervous system, but rather constrict in response to certain hormones, such as epinephrine.

Question 11

Capillaries are the smallest blood vessels, found between metarterioles and thoroughfare channels, and are the sites where exchange of gases, nutrients, and wastes occurs between the blood and surrounding tissues. Capillaries consist of endothelium surrounded by a basement membrane, and the extremely thin capillary wall is necessary to allow diffusion of materials.

Question 12

Fenestrated capillaries have small pores called fenestrations (“windows”) through which materials can readily pass into and out of the blood.

Question 13

Continuous capillaries lack fenestrations and are the most common type of capillaries, existing in all tissues except epithelial tissue and cartilage. In some regions of the body, continuous capillaries contain tight junctions around their endothelial cells. Since many blood-borne nutrients cannot pass between these endothelial cells, they must pass through the cells before reaching tissues outside the vessel. Continuous capillaries in the brain have tight junctions and form a major component of the blood-brain-barrier, which protects the brain tissue.

Question 14

Capillaries unite to form thoroughfare channels, which in turn unite to form larger vessels called venules. Finally, venules unite to form even larger vessels called veins, which transport blood back to the heart.

Question 15

Most veins transport deoxygenated blood (exceptions are the pulmonary veins and umbilical veins)

Question 16

Veins have valves that prevent backflow of blood. Veins have the same tunics as arteries, but they are thinner.

Question 17

A vein has a relatively large lumen that offers little resistance to blood flow,

Question 18

anastomosis (a-nas-tō-MŌ-sis; “furnish with a mouth”) is a union of two or more vessels.

Question 19

hen several arteries supply blood to the same organ, that organ has collateral circulation

Question 20

single artery that is the only source of blood for an organ is an end artery.

Question 21

arteriovenous anastomosis is a direct connection between an artery and a vein and includes regions where metarterioles and thoroughfare channels directly connect to one another.

Question 22

Arterial pressure, which is commonly referred to simply as blood pressure, is the pressure in the arteries that forces blood into the capillaries. In order for blood to flow, blood pressure must be higher than the resistance to blood flow.

Question 23

systolic pressure (pressure during ventricular systole) is the top number,

Question 24

and the diastolic pressure (pressure during ventricular diastole)

Question 25

pulse is a periodic change in a vessel’s blood pressure caused by periodic contraction and relaxation of the heart.

Question 26

During ventricular systole, the pressure in the artery rises and causes the vessel to expand.

Question 27

During ventricular diastole, the pressure in the artery drops and the vessel diameter decreases. Pulse pressure is the difference between systolic pressure and diastolic pressure. If the BP is 120/60, then pulse pressure would be 120-60=60 mmHg.

Question 28

“average” pressure, or mean arterial pressure (MAP),

Question 29

cardiac output (CO) is the amount of blood expelled from a ventricle every minute. Therefore, increasing CO increases the amount of blood pumped through the arteries in a given time, and this will increase the pressure in the arteries

Question 30

Increasing blood volume increases BP in the same way that adding more water to a water balloon increases the pressure inside the balloon, making it more likely to burst.

Question 31

Peripheral resistance refers to factors that oppose blood flow once it leaves the heart, and this resistance makes it harder to pump blood through the arteries.

Question 32

Vascular resistance is the friction between blood and the vessel wall that impedes the flow of blood through the vessel. Factors affecting vascular resistance are vessel length, vessel diameter, and path of flow.

Question 33

Vessel length: There is a positive correlation between vessel length and resistance, the longer the vessel, the greater the resistance.

Question 34

Vessel diameter: There is a negative relationship between vessel diameter and resistance: the greater the diameter, the lower the resistance. Like milkshake through small/large straw

Question 35

Path of flow: When blood flowing through straight vessels suddenly encounters a bend, it encounters more resistance, and the rate of blood flow may decrease. This can be compared to a race being able to go much faster on the straight parts of a racetrack but having to slow down on the curves.

Question 36

Blood turbulence refers to the swirling action of a liquid as it changes direction quickly or flows over irregular surfaces. Blood experiences most turbulence within the heart and large-diameter arteries, such as the aorta.

Question 37

Blood viscosity is the resistance to flow due to its dissolved and suspended items. Compared to pure water, which has a viscosity of 1.0, blood has a viscosity of about 5. This means that blood is about five times “thicker” than pure water. Blood viscosity correlates positively with hematocrit and the concentration of plasma proteins.

Question 38

Venous pressure is the pressure in the veins and is responsible for venous return to the heart.

Question 39

he heart is unable to generate enough force to pump blood through the veins; therefore, there must be a force from outside the vein to help move venous blood. These forces include the skeletal muscle pump and the respiratory pump.

Question 40

Skeletal muscle pump: Phenomenon by which the squeezing force generated on veins when surrounding skeletal muscles contract helps “push” blood toward the heart. When the muscles relax, the vein’s blood tries to backflow, but the valves in the veins prevent this from happening.

Question 41

Respiratory pump: Phenomenon by which inhalation generates a “pulling” force to bring blood back to the heart. This action is based on Boyle’s Law, which states that the volume of a closed container has a negative effect on the container’s pressure. The lungs reside within the thoracic cavity, which is a closed system (not connected to the outside of the body). During inhalation, skeletal muscles contract and cause the thorax to expand. This action increases the thoracic volume, which in turn decrease the thoracic cavity’s pressure. As a result, blood is drawn toward this region of lower pressure. In contrast, during exhalation, the thorax returns to its original position and the thoracic volume decreases and thoracic pressure increases. This action attempts to push blood away from the heart, or at least slow down its movement toward the heart. But again, valves in the veins can help keep the blood from moving “backwards” until the next inhalation.

Question 42

The slow movement of blood in the capillaries allows efficient exchange of materials between the blood and surrounding tissues. However, the movement of blood through capillaries is highly variable and pulse-like due to the periodic contraction and relaxation of precapillary sphincters. This process, called vasomotion (vā-sō-MŌ-shun), occurs in response to the concentrations of various chemicals in the local tissues.

Question 43

The movement of solutes between the capillaries and surrounding tissues occurs through two processes: diffusion and filtration. Both processes can occur through fenestrations in the endothelial cells and/or small gaps (clefts) between those cells. While diffusion involves moving substances from regions of high concentration to regions of lower concentration, filtration involves moving solutes from regions of higher hydrostatic pressure to regions of lower hydrostatic pressure

Question 44

The movement of solutes between the capillaries and surrounding tissues occurs through two processes: diffusion and filtration. Both processes can occur through fenestrations in the endothelial cells and/or small gaps (clefts) between those cells. While diffusion involves moving substances from regions of high concentration to regions of lower concentration, filtration involves moving solutes from regions of higher hydrostatic pressure to regions of lower hydrostatic pressure

Question 45

Movement of water through the capillary wall is due to hydrostatic and osmotic pressure differences between the blood and surrounding tissues. Recall from Chapter 5, hydrostatic pressure (HP) is the force exerted by a fluid’s potential energy, which may be due to (1) the fluid’s volume; the greater the volume, the greater the hydrostatic pressure; and/or (2) a mechanical pump exerting force on the liquid.

Question 46

On the other hand, osmotic pressure (OP) is the pressure exerted by water due to its dissolved solutes (osmolarity);

Question 47

Forces that move fluid from the blood into the interstitial fluid include blood hydrostatic pressure (BHP) and interstitial fluid osmotic pressure (IOP).