Chapter 21: Vessels

Question 1

What are vessels

Answer 1

A closed system which 5 main vessel types:

• arteries
• arterioles
  -capillaries
• venules
• veins

Question 2

Tunica interna

Answer 2

Layer closest to lumen

Made of simple squamous epithelium, basement membrane, and connective tissue

Question 3

Tunica media

Answer 3

The middle layer

Made of circularly, arranged, smooth muscle fibres which regulates the diameter of the lumen.

Question 4

Tunica externa

Answer 4

Outermost layer

Made of connective tissue that anchors the blood vessel to its surrounding structures

Question 5

Blood pressure

Answer 5

The force exerted by the blood against the wall of a blood vessel. Blood pressure differences within vessels keeps the blood moving.

(Blood pressure decrease the further away it is from the left ventricle)

Question 6

Vasoconstriction

Answer 6

Decreasing the diameter of the lumen which increases blood pressure.

Question 7

Vasodilation

Answer 7

Increases the diameter of the lumen and decreases the blood pressure.

Question 8

Hypertension

Answer 8

Constantly high blood pressure

Primary hypertension - no identifiable cause. (90-95%)

Secondary hypertension - does have an identifiable cause such as kidney disease (5-10%)

Question 9

Systolic pressure

Answer 9

The maximum pressure against the arterial wall during ventricular contraction

Usually 120 mmHg

Question 10

Diastolic pressure

Answer 10

The minimum pressure against the arterial wall during ventricular relaxation

Usually 80mmHg

Question 11

Pulse pressure

Answer 11

The differences between systolic pressure and diastolic pressure

SP - DP = PP

Question 12

Elastic arteries

Answer 12

Arteries which contain many elastic fibres

• tunica media has many smooth muscle layers and many elastic fibres

Includes the pulmonary trunk, and the aorta and its branches.

They are considered conducting arteries.

Question 13

Muscular arteries

Answer 13

Medium sized and branch to various organs.

• Has the thickest tunica media with more smooth muscle than elastic fibres

Considered distributing arteries since they deliver blood to organs.

Question 14

Arterioles

Answer 14

Microscopic vessels that contain mostly smooth muscle and very few elastic fibres.

They regulate flow into capillary beds

Known as resistance vessels

Question 15

Capillaries

Answer 15

Microscopic vessels with a single layer of endothelial cells and a basement membrane.

Have a large surface area in order to function in the exchange of materials between blood and interstitial fluid

Question 16

How many RBC’s can pass through a capillary at a time? Why?

Answer 16

1

The diameter of a capillary and the diameter of a RNC are the same

Question 17

Continuous capillaries

Answer 17

In skin and muscles

Allow only LIMITED passage of fluids and small solutes.

Held by tight junctions (very little gaps)

Question 18

Fenestrated capillaries

Answer 18

In small intestine, kidney

Has a greater permeability (tolerance) to fluids and solutes

Contains fenstrations (pores)

Question 19

Sinusoid capillaries

Answer 19

In liver, bone marrow, lymph tissue

Allow large molecules to pass between blood and tissues (such as blood cells and proteins)

Have LARGE pores (looks destroyed)

Question 20

Capillary exchange

Answer 20

Artery end gets net OUTWARD pressure for filtration.
(Fluid exits capillary)

Venous end gets net INWARD pressure for reabsorption
(Fluid enters capillary)

Question 21

Venules

Answer 21

Receive blood from the capillaries

Question 22

Veins

Answer 22

Made up of venules joined together.

Function to bring blood back to the heart under low pressure (need for venous return)

Question 23

How much blood volume can veins hold

Answer 23

Approx. 60% of blood volume

Question 24

Venous return

Answer 24

Factors that help return blood back to the heart.

• gravity (if above the heart)
• valves in veins
• contraction of skeletal muscles
• respiratory pump

Question 25

Varicose veins

Answer 25

Veins that are dilated and twisted due to leaky valves

aka hemorrhoids

Question 26

Cardiac output (CO)

Answer 26

Refers to the volume of blood pumped per minute by each ventricle of the heart.

CO = stroke volume (SV) x heart rate (HR)

Question 27

End diastolic volume (EDV)

Answer 27

Total volume of blood and ventricle at end of ventricular, relaxation phase (diastolic value)

Question 28

End systolic volume

Answer 28

Total volume of blood ventricle after the ventricle has contracted and ejected about 60% of the blood from its chambers. (Systolic value)

Question 29

Stroke volume

Answer 29

The volume of blood pumped by each ventricle during each heartbeat

Stroke volume = EDV - ESV

Affected by 2 things:
1. Stretching of cardiac muscle fibres
2. Contractility of cardiac muscle fibres.

Question 30

Starlings law

Answer 30

If you increase venous return, you increase the stretch of cardiac muscle fibres, and you increase the force of contraction

Question 31

Baroreceptors

Answer 31

Pressure sensitive neurons located in the carotid sinus and aortic arch. They will communicate with the medulla oblongata to regulate blood pressure

Is BP increases, baroreceptors stretch more (vice versa)

Question 32

Peripheral resistance

Answer 32

Refers to the resistance to blood flow due to friction between the blood and vessel wall.

Effected by:
- blood thickness
- vessel radius

Note: first layer of fluid sticks to vessel wall and moves slower.