Chapter 19 - Blood Vessels Flashcards Preview

Anatomy and Physiology 2 > Chapter 19 - Blood Vessels > Flashcards

Flashcards in Chapter 19 - Blood Vessels Deck (59)
Loading flashcards...

Closed System

The blood never directly bathes the tissues, a small amount of fluid is forced across the walls of the capillaries and that is what bathes the tissues.


Dual Circulatory System

Two different circuits. The pulmonary circuit and the systemic circuit.


Pattern of Flow

Arteries carry blood away from the heart, they then divide into smaller arteries and then arterioles. The arterioles supply the capillaries and the capillaries are then drained by venules which join to form veins, which return the blood to the heart.


Structure of a blood vessel

Three layers, or tunics. The tunica intima, tunica media, and tunica adventitia


Tunica Intima

The innermost layer of the blood vessels. A simple layer of squamous epithelium, or endothelium. It is continuous throughout the heart and all the way to the capillary walls.


Tunica Media

Layer of smooth muscle and elastic fibers.


Tunica Adventitia (Externa)

A thin outer layer of connective tissue. It contains collagen and elastic fibers.


Elastic Arteries

Largest arteries in the body. Have a thick tunica media rich in elastic fibers, actually have more elastic tissue than muscle. The main arteries leaving the heart: the aorta, pulmonary trunk, pulmonary arteries, etc.


Muscular Arteries

Medium sized arteries. They distribute blood to the organs. They have more smooth muscle than elastic tissue. They constitute most of the named arteries.



Smallest arteries, their main function is to regulate the blood flow into the capillaries



Consist of nothing more than an endothelium, because of that they are able to move material across their walls.


Continuous Capillaries

Found in most parts of the body. The epithelial cells are held together by tight junctions


Fenestrated Capillaries

They have pores, which means they can have extensive filtration. Found in sites of heavy filtration, like the kidneys.


Sinusoidal Capillaries

Have wide flat channels through which blood flows very slowly. A special type of fenestrated capillary, found in the liver because of the extensive exchange.



Blood flow through the capillaries is not a continuous flow, but a series of impulses. It can be controlled by a change in the concentrations of chemicals and gasses dissolved in the interstitial fluid.



Consist of endothelium surrounded by a small amount of connective tissue. As they get larger, they begin to have a tunica media.



They have all 3 layers, but the tunica media is very thin, only a few muscle cells, and the tunica adventitia is the thickest layer. THey are thin walled and more distensible than arteries. The tunica intima will form valves which prevent the backflow of blood.


Blood Flow

Represents the volume of blood passing though an area per unit of time.


Blood Velocity

The larger the cross-sectional area, the slower the flow.


Factors Which Affect Flow

Pressure- the energy imparted by the pumping of the heart
Resistance - The friction that blood has to overcome while traveling through the vessels


Types of Resistance

Blood viscosity - The blood's internal resistance to flow
Vessel resistance - Vessel length, diameter, and turbulence.


Relationship between flow, pressure, and resistance

Flow is equal to pressure divided by resistance. In order for blood to flow, the pressure at the end of the vessel must be loss that at the beginning of the vessel.


Mean Arterial Pressure

The average between the two different blood pressure, systolic and diastolic.


Blood Pressure

Essential for blood flow. Refers to the arterial blood pressure. Two different values, systolic and diastolic, and expressed in mmHg. Ex: 120/80mmHg


Pulse Pressure

The difference between systolic and diastolic pressure. Responsible for what we perceive as our pulse. A large difference means a strong pulse, a small difference creates a weak pulse.


Factors That Affect Blood Pressure:
Blood Volume

The higher the volume, the greater the pressure


Factors That Affect Blood Pressure:
Viscosity of Blood

The more viscous, the greater the pressure. Due mostly to the formed elements. The higher hematocrit, the higher viscosity.


Factors That Affect Blood Pressure:

The elasticity of vessels buffers the blood pressure from having extreme systolic and diastolic numbers


Factors That Affect Blood Pressure:

Blood moving upwards has to work against the pull of gravity


Factors That Affect Blood Pressure:
Cardiac Output

The more blood put into the arterial tree per minute, the greater the pressure