Chapter 20 Review: Blood Vessels

0.0(0)
studied byStudied by 3 people
learnLearn
examPractice Test
spaced repetitionSpaced Repetition
heart puzzleMatch
flashcardsFlashcards
Card Sorting

1/39

encourage image

There's no tags or description

Looks like no tags are added yet.

Study Analytics
Name
Mastery
Learn
Test
Matching
Spaced

No study sessions yet.

40 Terms

1
New cards

List the layers of a blood vessel from the outermost to the innermost layer.

  1. Tunica Externa (Adventitia)

  2. Tunica Media

  3. Tunica Intima

  4. Lumen

2
New cards

Tunica Intima

  • Innermost layer, simple squamous epithelium called endothelium

  • Cells fit together like tiles on a floor & minimizes friction w/ blood

3
New cards

Tunica Media 

  • Middle layer thicker in arteries than in veins

  • Made of smooth muscles, elastic fibers, & is responsible for changing diameter of vessels 

    • Contains Vasoconstriction & Vasodilation

4
New cards

Vasoconstriction

decreases the diameter of vessel, increasing pressure & reducing blood flow

5
New cards

Vasodilation

increases the diameter of vessel, decreasing pressure & increasing blood flow

6
New cards

Tunica Externa (Adventitian)

A sheath of connective tissue on surface of vessel, containing collagen & elastic fibers for protection & anchoring of vessel

7
New cards

Lumen

  • Central space within vessel which blood flows

  • Larger in a vein than an artery

  • The thicker walls & smaller diameters give atrial lumens a more rounded appearance in cross section than the lumens of veins

8
New cards

Arteries

  • a vessel that conducts blood away from the heart 

  • They have relatively thick walls to withstand the high pressure of blood from heart

  • Types: Elastic, Muscular, Arterioles

9
New cards

Elastic Arteries

  • These are the thick walled, large diameter, arteries near the heart

  • They expand when the ventricles contract, then recoil to maintain blood pressure while the ventricles relax (closest to the heart)

10
New cards

Muscular Arteries

  • Typically ranges from 0.1 mm to 10 mm 

  • Elastic arteries give way to these arteries (further away from the heart)

  • These are most of the smaller arteries in rest of the body

  • The thick tunica media allows muscular arteries to undergo vasoconstriction and vasodilation

  • Decreased quantity of elastic fibers limits ability to expand

11
New cards

Arterioles

  • Very small arteries that lead to a capillary, 0.3 mm to 10um (micrometer)  in diameter

  • They control how much blood is going to a tissue

  • Almost shut off blood supply or increase blood supply 

    • (For example, blushing involves vasodilation of arterioles in the face)


12
New cards

Capillaries

  •  Are microscopic, they are the smallest blood vessels

  • Walls are only an endothelial layer, surrounded by a basement membrane with occasional smooth muscle fibers

  • Very thin-walled and narrow, RBCs pass through in single file

  • Site of exchange of gases and other substances between the blood and the surrounding cells and their tissue fluid

  • Types: Continuous, Fenestrated, & Sinusoidal

    • Remember that arteries and veins are only a transport system

13
New cards

Continuous Capillaries

  • Found in skin and muscles

  • These the most common type

  • Uninterrupted lining of endothelial cells form tight junctions

  • Contains very small gaps that allow substances to leak through 

    • i) metabolic products (glucose, water)

    • ii) small hydrophobic molecules (gases and hormones)

    • iii) some leukocytes


14
New cards

Fenestrated Capillaries

  • Walls of these capillaries have pores

  • Permits greater permeability of fluids and larger molecules

  • Found in areas where absorption or secretion takes place

  • Ex: in the intestines and kidneys and endocrine structures, like the hypothalamus, pituitary, pineal gland, and thyroid glands

15
New cards

Sinusoidal Capillaries

  • Least common type of capillaries

  • Have extensive intercellular gaps and incomplete basement membranes

  • Very large openings allow for the passage of the large molecules, including plasma proteins and even cells

  • Found in liver, bone marrow, lymph tissue, some endocrine glands

  • Very leaky capillaries and blood flow is very slow through them 


16
New cards

Veins

  • A blood vessel that conducts blood toward the heart

  • Usually, but not always, contain un-oxygenated blood 

  • They are thin-walled vessels, with large and irregular lumens

  • Contain back-flow valves that maintain the unidirectional flow of blood toward the heart and prevent backflow toward the capillaries 

  • Low blood pressure

  • contains Venules

17
New cards

Venules

  • Are extremely small veins, generally 8-100 um in diameter

  • Very porous to permit the movement of WBCs & fluid 

  • Multiple of these join to form veins

18
New cards

Blood Flow

  • Refers to the movement of blood through a vessel

  • Actual volume of blood flowing through a vessel, organ, or body per unit of time, ml/min

19
New cards

Blood Pressure

  • Force per unit area exerted by the blood on the walls of a blood vessel, mm Hg

20
New cards

Resistance 

Opposition to flow, a measure of the amount of friction the blood encounters as it flows through vessels

21
New cards

What factors affect Blood Flow

  • Cardiac Output

    • Increase: ↑ BP & flow (more blood from heart)

    • Decrease: ↓ BP & flow

  • Compliance

    • Increase: ↓ resistance, ↑ flow

    • Decrease: ↑ resistance (less elastic), ↓ flow

  • Blood Volume

    • Increase: ↑ BP & flow

    • Decrease: ↓ BP & flow

  • Viscosity

    • Increase: ↑ resistance, ↓ flow

    • Decrease: ↓ resistance, ↑ flow

  • Vessel Diameter

    • Increase: ↓ resistance, ↑ flow (vasodilation)

    • Decrease: ↑ resistance, ↓ flow (vasoconstriction

  • Total Blood Vessel Lenghth

22
New cards

What Factors Increase Resistance in Blood Vessels

  • ↑ Blood viscosity

    • Increases resistance

  • ↑ Total blood vessel length

    • Increases resistance

  • ↓ Vessel diameter

    • decreases ressitance

  • ↓ Arterial compliance

    • decreases ressitance

  • Plaque buildup or vascular disease

23
New cards

Cardiac Output

  • How much blood flows from ventricles 

  • Anything that causes output to increase, by elevating heart rate and/or stroke volume, will raise blood pressure and increase flow

  • Increase: ↑ BP & flow (more blood from heart)

  • Decrease: ↓ BP & flow

24
New cards

Compliance

  • The ability of any compartment to expand and accommodate increased. 

    • (Ex: a balloon is compliant and a metal pipe is not)

  • Arteries with greater compliance are able to expand to accommodate surges in blood flow, without increased resistance or blood pressure

  • Veins are more compliant than arteries

  • Vascular disease reduces compliance, because the arteries stiffen, increasing resistance to blood flow

  • The result of reduced compliance is more turbulence and higher pressure within the vessel, reducing blood flow

  • Increase: ↓ resistance, ↑ flow

  • Decrease: ↑ resistance (less elastic), ↓ flow

25
New cards

Blood Volume

  • As blood volume increases, blood pressure and flow increase

  • Increase: ↑ BP & flow

  • Decrease: ↓ BP & flow

26
New cards

Blood Viscosity

  • Is the thickness of a fluid which affects its ability to flow. Ex: water is less viscous than molasses and flows faster

  • The more viscous the blood, the greater the resistance and less the flow

  • The two primary components of blood viscosity are the formed elements and plasma proteins

    • Increase: ↑ resistance, ↓ flow

    • Decrease: ↓ resistance, ↑ flow

27
New cards

Blood Vessel Diameter

  • Not constant

  • Fluid close to the walls encounters more resistance

  • Smaller vessels have more resistance because more fluid contracts the sides of the vessel

  • Capillaries cause the most resistance because they have the smallest diameters 

  • Large diameter vessels near the heart have very little resistance due to vessel diameter, because relatively little of the blood is in contact with the sides

    • Increase: ↓ resistance, ↑ flow (vasodilation)

    • Decrease: ↑ resistance, ↓ flow (vasoconstriction

28
New cards

Total Blood Vessel Length

  • Longer the length of a vessel the greater the resistance and lower the flow

  • The total length of the circulatory system is relatively constant

    • Flow is greatest at output side of the heart

    • Flow is zero at input side of the heart

29
New cards

How is the body designed to aid blood movement in the relatively low pressure

  • Venous Valves: Prevent backflow

  • Respiratory Pump: Inhalation increases ↑ abdominal pressure increases, pushing blood to heart

  • Muscular Pump: Skeletal muscles contract to push blood upward toward heart

30
New cards

Respiratory Pump

  • Inhaling increases abdominal pressure, squeezing the abdominal blood vessels and forcing blood to the heart

  • Valves in the veins prevent backflow during exhalation

31
New cards

Muscular Pump

  • Skeletal muscles contract and relax, and they squeeze the blood towards the heart

  • The muscular pump is the most important of these two pumps

32
New cards

How to maintain Blood Pressure

  1. Cardiac output - by increasing or decreasing heart rate

  2. Peripheral resistance - by changing the diameter of blood vessel 

  3. Blood volume - by increasing or decreasing the volume of the blood

33
New cards

Vasomotor Center

  • located in the medulla

  • Controls blood vessel diameter

  • Transmits action potentials to the smooth muscles of the arterioles

  • These smooth muscles are always in a slight state of constriction

    • Thus they can always either increase or decrease in diameter

    • Increasing the number of action potentials causes muscles to constrict, decreasing diameter of the vessel

    • Decreasing the number of action potentials causes muscles to relax, increasing diameter of the vessel

34
New cards

Barorecptors

  • These are pressure receptors

  • Located in the aorta and most of the large elastic arteries 

  • Increased arterial blood pressure causes these receptors to send action potentials to the vasomotor center

  • A decrease in blood pressure causes the opposite reaction

  • System functions to protect against rapid changes in blood pressure

    • Like when you stand up too quickly

  • ↑ BP increases→ sends signals to vasomotor center to ↓ vessel resistance and lower BP

  • ↓ BP decreases → opposite effect

35
New cards

Chemoreceptors

  • When O2 and CO2 levels rise and pH decreases

    • Chemoreceptors in the aortic arch and neck send action potentials to the vasomotor center

    • Vasoconstriction occurs

  • Increased blood pressure speeds up the flow of blood to the heart and lungs

  • ↓ O₂ / ↑ CO₂ → trigger vasoconstriction to raise BP and speed up circulation

36
New cards

Epinephrine and Norepinephrine

  • Secreted by adrenal medulla as part of the fight or flight response

  • Effect heart by increasing cardiac output

  • Causes vasoconstriction in arterioles

  • Vasodilatation in large veins, cardiac, and skeletal muscle

  • Overall increases blood pressure

  • ↑ BP → ↑ cardiac output + vasoconstriction (arterioles)

37
New cards

Angiotensin II Hormone

  • Effects peripheral resistance to causes vasoconstriction in arterioles 

  • Increases blood pressure

  • ↑ BP → Strong vasoconstrictor

38
New cards

Antidiuretic Hormone (ADH)

  • Stimulates kidney to conserve water and increase blood volume

  • Effects peripheral resistance when there is extreme blood loss 

  • Causes vasoconstriction in arterioles

  • ↑ BP → Retains water + vasoconstriction during blood loss

39
New cards

Nitric Oxide

  • Vasodilation

  • Very short lived

  • Released in response to high rates of blood flow

  • May be a major factor involved in maintaining blood pressure

  • ↓ BP → Short-lived vasodilation

40
New cards

Alcohol

  • Causes drop in blood pressure

  • Inhibits antidiuretic hormone release

  • Depresses the vasomotor control center and causes vasodilatation

  • ↓ BP → Inhibits ADH + vasodilation