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Emrg 1230 > Week 6- Blood Vessels Anatomy and Physiology > Flashcards

Week 6- Blood Vessels Anatomy and Physiology Flashcards

1
Q

What 3 separate layers does the blood vessel wall consist of?

A
  1. Tunica Adventitia (outside)
  2. Tunica Media (middle)
  3. Tunica Intima (interior)
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2
Q

As the vessels decrease in diameter….

A
  • the relative thickness of their walls decrease
  • Capillaries are the only exception to this-they consist of only 1 layer
  • 4 structures are always constant regardless of vessel size
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3
Q

What are Lining Endothelial Cells?

A
  • Line entire vessel
  • Provide a smooth luminal surface by inhibiting intravascular coagulation
  • Pores present in their membrane to allow for diffusion and movement of substances into the blood
  • Capable of reproduction- provide new cells to increase blood vessel size or repair damage cells
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4
Q

What are Collagen Fibers?

A
  • Reinforcing strands woven together- similar to the wall of a garden hose
  • Minimally stretch- approx. 2-3%
  • Function to keep the lumen of the vessel open and strengthen the walls
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5
Q

What are Elastic Fibers?

A
  • Made of elastin
  • Rubber-like network- highly elastic and capable of stretching more than 100%
  • Allow for recoil after distension
  • Maintains passive tension- maintain normal BP
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6
Q

What are are Smooth Muscle Fibers?

A
  • Found in the wall of all segments of the vascular system except capillaries
  • Most numerous in elastic and muscular arteries
  • Exert active tension when vessels contracted
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7
Q

Tunica Adventitia (External)- Outer Layer

A
  • Made of strong, flexible, connective tissue
  • Helps hold the vessel open and prevents tearing during body movements

In veins- thickest of all 3 layers
In arteries- 2nd thickest next to the middle layer

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8
Q

Tunica Media- Middle Layer

A
  • Made of smooth muscle tissue sandwiched together with layers of elastic connective tissue
  • The muscle layers allow for changes in blood vessel diameter
  • Innervated by autonomic nerves to control diameter
  • Arteries have a thicker Tunica Media than veins
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9
Q

Tunica Intima- Inner Layer

A
  • Made up of endothelial cells- extremely thin
  • In veins- these cells make up the semilunar valves
  • In capillaries- only this is present (key features as the thinness is required for efficient exchange of materials between the blood plasma and the interstitial fluid)
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10
Q

Arteries

A
  • Thick walled, muscular vessels
  • Vessel that carries blood away from the heart
  • Usually carry oxygenated blood
  • Only exception is: (pulmonary arteries)
  • Arterial walls are highly sensitive to stimulation from the ANS
  • Causes change in their diameter as they relax and contract
  • Regulate BP
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11
Q

What are the type of arteries?

A
  • Elastic arteries
  • Muscular arteries
  • Arterioles
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12
Q

Elastic Arteries

A
  • Largest in the body and include the aorta and some of its major branches
  • These can stretch without injury to accommodate the surge of blood forced into them as the heart contract
  • Recoil- when the ventricles relax- they accommodate
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13
Q

Muscular Arteries

A
  • Also called distributing arteries
  • Carry blood father away from the heart to specific organs
  • Smaller in diameter
  • Walls are thicker than elastic arteries
    Ex. brachial artery, gastric artery, mesenteric artery
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14
Q

Arterioles

A
  • Also called resistance vessels
  • Small arteries
  • Not named individually, but as a group
  • Main function is to regulate blood flow through the body
  • Increased contraction= increased resistance to blood flow, regulates BP and vice versa
  • Also determines quantity of blood that enters an organ
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15
Q

Veins

A
  • Operate on the low pressure side of the system
  • Thinner walls
  • Less capacity to decrease their diameter
  • Thinner walls make veins more likely to distend when exposed to small increases in backpressure
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16
Q

Capillaries

A
  • Microscopic blood vessels
  • Carry blood from the arteries to the venules
  • Walls extremely thin (one cell thick)
  • Transfer of nutrients and other vital substances between blood and tissue cells
  • Over 1 billion in the body- not evenly distributed
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17
Q

Precapillary Sphincter

A
  • Precapillary sphincters regulate the volume of inflow of blood through the capillary
  • Band of smooth muscle encircling the capillary
  • Open= blood flows in
  • Closed/ partially closed= decreased flow
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18
Q

Vein System

A
  • Blood passes through all the arteries into capillaries and eventually into the venules
  • Venules= first venous structures to receive blood after it leaves the capillaries
  • Blood exits the venule and goes into the larger vessels called the veins
  • Vein: vessel that carries blood towards the heart
  • Veins become larger as they get closer to the heart
  • Veins have a great ability to stretch- this allows them to accommodate varying amounts of blood with almost no change in BP
19
Q

Peripheral Resistance

A
  • Resistance to blood flow imposed by force of friction between the blood and the vessel walls
  • Develops partially because of viscosity (higher proportion of RBC and protein molecules in bond)
  • Partly from diameter of arterioles and capillaries
20
Q

Vasomotor Mechanism

A
  • Vasoconstriction= reduction in blood vessel diameter caused by an increased contraction of the muscular wall (increases resistance to blood flow thereby decreasing blood flow to the tissues
  • Vasodilation= increases vessel diameter by relaxation of the muscular wall (causes an increase in blood flow to the tissues)
21
Q

Mechanism

A
  • Controlled in the medulla- vasomotor center on vasoconstriction center
  • When stimulated- initiate an impulse outflow by sympathetic fibers that end in the smooth muscles of the vessel walls cause constriction
22
Q

Reservoirs

A
  • In addition to the sympathetic innervation, the body houses blood reservoirs in the venous plexus- located in the skin and abdominal organs
  • These serve as a kind of slow moving stockpile or receive of blood
  • Blood can be moved out of revoirs into arteries that supply the heart and other organs when increased activity demands
23
Q

Vasomotor pressor reflexes

A
  • Changes in arterial blood oxygen or carbon dioxide content sets a chemical vasomotor control mechanism int operation
  • This changes the arterial BP- initiates the vasomotor pressor reflexes
  • 1 of 2 things can happen depending on the body’s needs
24
Q

Increase in Arterial BP

A
  • Stimulation of the aortic and carotid baroreceptors (sense pressure changes)
  • This stimulates the Cardiac Control Center to lower the HR
  • Inhibits vasoconstriction center
  • More impulse per second go out over the parasympathetic fibers to slow the HR and dilate the venues of the blood reservoirs
  • Strives to bring the BP back to normal (homeostasis)
25
Q

Decrease in Arterial BP

A
  • Again, the baroreceptors are stimulated to sense the pressure changes
  • This stimulate the cardiac control center to elevate the HR
  • Sends more impulses to the medulla to stimulate vasoconstriction
  • Stimulate the SNS, increasing HR and vasoconstriction- thereby raising BP to normal levels (homeostasis)
26
Q

Vasomotor Chemoreflexes

A
  • Located in the aortic and carotid bodies
  • Sensitive to excess blood CO2 levels (hypercapnia), less sensitive to low levels of O2 (hypoxia)
  • When either of these 2 occur- impulses are sent via chemoreceptors to the medulla’s vasoconstriction center- vasoconstriction soon follows, HR increases
  • Emergency system when high CO2 or low O2 endangers the stability of the internal environment
27
Q

Venous Return to the Heart

A
  • Refers to the amount of blood returned to the heart by way of the veins
  • Done by several mechanisms:
    1) venous reservoirs- BP drops, walls of the veins adjust and blood flows in to maintain optimal blood return
    2) Elastic nature of the veins- BP rises, vein walls expand to allow them to adapt to the higher pressure
  • Both these are referred to as “stress relaxation effect”
28
Q

Gravity

A
  • Naturally, when a person stands- blood wants to pool in the lower extremities as a result of gravity
  • This is combated by venous pumps
  • Maintain pressure gradients to keep blood moving into the central veins are back to the heart
  • 2 types: respiratory and skeletal
29
Q

Respiratory Venous Pump

A
  • Caused by increasing the pressure gradient between the peripheral veins and the vena cava
  • Inspiration- diaphragm contracts and the thoracic cavity becomes larger and the abdominal smaller
  • As a result- the pressure in the thoracic cavity, vena cava and atria decrease and those in the abdominal cavity (abdominal veins) increase
  • Expiration- opposite
  • This change in pressure between inspiration and expiration acts as a respiratory pump that moves blood along the venous route
30
Q

Skeletal Muscles

A
  • Serves as “booster pumps”
  • As each skeletal muscle contracts, it squeezes the veins inside, thereby “milking” the blood upward/ towards the heart
  • The semilunar valves in veins then close and prevent blood from flowing back as the muscle relaxes
31
Q

Total Blood Volume

A
  • Return of blood to the heart can be influenced by factors that change the total blood volume
  • Most quickly and effectively done by water moving into the plasma (increasing blood volume) or out of the plasma (decreasing blood volume)
  • These are key in maintaining constancy of blood flow
32
Q

Diffusion, Osmosis and Filtration

A
  • Diffusion- oxygen and CO2 pass through capillary walls from higher to lower concentration
  • Fluid movement across a capillary walls determined by a combination of hydrostatic or osmotic pressure
  • Osmotic Pressure- movement of water into and out of the cell from high concentration to low
  • Filtration is forcing of some water and dissolved substances through capillary walls by blood pressure
33
Q

Filtration and Osmotic Pressure

A

as blood enters the capillary bed on the arteriole end, the blood pressure in the capillary vessel is greater than the osmotic pressure of the blood in the vessel. The net result is that fluid moves from the vessel to the body tissue

34
Q

Gas Exchange

A

at the middle of the capillary bed, blood pressure in the vessel equals the osmotic pressure of the blood in the vessel. The net result is that fluid passes equally between the capillary vessel and the body tissue. Gasses, nutrients, and wastes are also exchanged at this point

35
Q

Blood Pressure

A
  • High pressure in the arteries must be maintained to keep blood flowing through the system
  • Chief determinant is the blood volume
  • Blood volume and BP are directly proportional
  • Systolic & diastolic pressure
  • Pulse pressure= difference between the two
  • Pulse is the expansion and contraction of the arterial wall during these phases of contraction and relaxation
  • Cardiac output and Peripheral Resistance are the 2 most important factors affecting BP (4 total)
36
Q

What are the four factors affecting BP?

A
  • Cardiac output
  • Blood volume
  • Peripheral resistance
  • Blood viscosity
    An increase in any one relates to an increase in the BP
37
Q

Cardiac Output

A

CO= SV (amt/beat) x HR (beat/min)
- Affects blood entering the arteries
- If CO increases, the amount of blood entering the arteries increases, and tends to increase the volume of blood in the arteries

This causes an increase in arterial blood volume= increase in arterial BP

38
Q

Blood Volume

A
  • Reduced by severe hemorrhage, vomiting, diarrhea, reduced water intake
  • When the volume is replaced the BP returns to normal
  • With too much fluid BP and volume increases
39
Q

Peripheral Resistance

A
  • Friction of blood against the vessel walls
  • Affects blood leaving the arteries
  • If PR increases, it tends to decrease the amount of blood leaving the arteries, which tends to increase the amount of blood left in them- leads to an increase in arterial blood volume= increase BP
  • Arterioles change their diameter and play an important role in BP regulation
  • As arterioles constrict, peripheral resistance and BP increases
40
Q

Hormonal Control of BP- Antidiuretic Hormone (ADH)

A
  • increases water reabsorption in the kidneys, thus increasing blood volume (the more water absorbed into the blood, the greater the plasma volume becomes)
  • Response to decrease in blood volume and BP
  • Works to vasoconstrict blood vessels as well to raise BP (known as vasopressor)
41
Q

Aldosterone

A
  • If a decrease in BP is detected, works to increase blood volume by increasing reabsorption of sodium ions and water (from sweat, urine and the GI system)
  • Secreted by the adrenal gland
  • Increases osmolarity= pushes fluid back into the system
  • This then increases the BP as a result of the increase in blood volume
42
Q

Renin-Angiotensin-Aldosterone-System (RAAS)

A
  • In the kidneys and responsible for mostly long term BP adjustments

Utilizes:
- Renin
- Angiotensin I
- Angiotensin II
- Angiotensin Converting Enzyme (ACE)

  • When the kidneys detect a low BP (by a decrease in renal blood flow) they stimulate the release of RENIN
  • Renin then activates ANGIOTENSIN I (vasoconstrictor) and stimulates minor changes in BP
  • It then stimulates ANGIOTENSIN II- powerful vasoconstrictor
  • Finally- stimulates the release of Aldosterone which is also a strong vasoconstrictor
  • These all function to raise BP long term
43
Q

Histamine

A
  • Increases blood flow
  • Released when tissues are injured
  • Mast cells release histamine
  • This causes the vasculature to dilate and increase permeability
  • This allows the plasma and WBC to leave the cell at the injury site to encourage healing
  • When SNS stimulation is withdrawn- histamine is released- vasodilation
  • Lowers BP
44
Q

Kinins

A
  • Kalinin’s, Bradykinin
  • Produce relaxation in the smooth muscles of the arteries, increase the capillary permeability, vasoconstrictor the venules
  • Lowers BP
  • ACE inhibitors work to lower BP- for pt’s with high BP
  • ACE inhibitors fall into this category (Captopril, Lisinopril, Enalapril)

Emrg 1230 (24 decks)

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