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Anatomy and Physiology 111 > Blood vessels > Flashcards

Blood vessels Flashcards

1
Q

What are the three types of vessels?

A

ARTERIES - carry blood away from heart. (oxygenated except in pulmonary circulation)

CAPILLARIES - connect arteries and veins. Contact point with tissue and site of exchange of materials.

VEINS - carry blood towards heart. (deoxygenated except for pulmonary)

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2
Q

What are the three layers in arteries and veins?

A

tunica intima
tunica media
tunica externa

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3
Q

What layers do capillaries have?

A

they only have one:

tunica intima

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4
Q

What is the lumen?

A

The fluid filled cavity in the center of the vessel

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5
Q

Describe the structure and function of the tunica intima.

A

endothelium lines the lumen of all vessels (simple squamous epithelium)

In vessels > 1mm, a sub endothelial connective tissue basement membrane is present (loose connective tissue)

FUNCTION: reduce friction on the surface.

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6
Q

Describe the structure and function of the tunica media.

A

Circular smooth muscle and sheets of elastin

Sympathetic vasomotor nerve fibers control vasoconstriction/vasodilation of vessels.

FUNCTION: controls diameter of the vessel.

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7
Q

Describe the structure and function of the tunica externa.

A

Loose network of collagen fibers protect and reinforce.

contain nerves, lymph vessels and blood vessels (larger vessels have vasa vasorum)

In large veins has elastin fibers to allow stretch

FUNCTION: anchors and reinforces vessel.

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8
Q

What are the three types of arteries?

A

Elastic (conducting) arteries

Muscular (distributing) arteries

Arterioles

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9
Q

Describe the function and structure of the elastic (conducting) arteries.

A

closest to heart (ex aorta)

large, thick walled. Abundant elastin and smooth muscle.

Large lumen offers low resistance and smooth muscle resists high pressure but vessel doesn’t play a role in vasoconstriction.

FUNCTION:provide low resistance pathway

Act as pressure reservoirs (expand and recoil as blood is ejected from heart)

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10
Q

Describe the function and structure of muscular (distributing) arteries.

A

deliver body to organs (further from heart than elastic)

have thick tunica with more smooth muscle, less stretchy.

FUNCTION: vasoconstriction, control blood flow to different parts of the body.

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11
Q

Describe the function and structure of arterioles:

A

smallest arteries that lead to capillary beds

tunica media has smooth muscle with few elastin fibers (can be very thin)

FUNCTION: control flow into capillary beds by dilating/constricting

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12
Q

What are the two types of arterioles?

A

terminal arteriole - lead to capillaries

metarteriole - connect arterioles and venules
- connect to the thorough fare channel

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13
Q

Describe the structure of capillaries

A

Microscopic blood vessels: only a single RBC can pass at a time

Walls are thin tunica intima, one cell thick squamous epithelial cells.

pericytes: smooth muscle like cells reinforce capillary wall and control permeability.

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14
Q

Where can you find capillaries?

A

in all tissue except cartilage, epithelium, cornea and lens

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15
Q

What are the three types of capillaries? (structural types)

A

CONTINUOS CAPILLARIES

FENESTRATED CAPILLARIES

SINUSOIDAL CAPILLARIES

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16
Q

Describe the continuous capillaries.

A

SKIN AND MUSCLES (abundant)
tight junctions connect endothelial cells (no gaps in wall)
intercellular clefts allow passage of fluids and small solutes.

IN THE BRAIN:
tight junctions are complete forming the blood-brain barrier

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17
Q

Describe the fenestrated capillaries.

A

some of the endothelial cells contain pores called fenestrations.

more permeable than continuous capillaries

FUNCTION: absorption or filtrate formation

found in small intestines, kidneys, and endocrine glands.

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18
Q

Describe the sinusoidal capillaries.

A

Contain fewer tight junctions, has larger intercellular clefts and larger lumens.

Usually fenestrated.

FUNCTION: allow blood cells and large molecules to pass

found in: liver, bone marrow, and spleen.

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19
Q

What are capillary beds?

A

they are interwoven networks of capillaries that form the microcirculation between arterioles and venules

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20
Q

What are the two types of vessels in the capillary beds?

A

VASCULAR SHUNT (metarteriole - thoroughfare channel; both of them that form the bypass): no exchange with tissue.

TRUE CAPILLARIES: carry out exchanges with tissue

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21
Q

What regulates the control of blood flow into true capillaries?

A

precapillary sphincters

These capillaries are regulated by local chemical conditions and vasomotor nerves.

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22
Q

Why is the blood flow in the capillaries so slow?

A

to allow for more effective exchange of materials with tissues.

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23
Q

What are the two types of structures in the Venous system?

A

Venules

Veins

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24
Q

Describe the structure and function of venules.

A

they are the exit when capillary beds unite (opposite of arterioles)

very porous: allow fluids and WBCs to pass into tissues

post capillary venules consist of endothelium and a few pericytes

Larger venules have one or two layers of smooth muscle cells

FUNCTION: collect blood from the capillaries

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25
Describe the structure and function of veins.
Formed when venules converge thinner walls, larger lumens, and lower BP compared to arteries. Thin tunica media and thick tunica externa of collagen and elastic networks (stretchy) FUNCTION: act as blood reservoirs.
26
What is a venous valve?
Valves in the veins that prevent the backflow of blood most abundant in veins of the limbs
27
What is varicose veins?
When the valves in the veins are leaky.
28
What are venous sinus? Give two examples
Flattened veins with extremely thin walls of endothelium CORONARY SINUS: collets deoxygenated blood from cardiac veins DURAL SINUS: collects blood draining from the brain.
29
What are vascular anastomoses?
interconnections of blood vessels. 3 types: ARTERIAL ANASTOMOSES: provide collateral channels. Common at joints, abdominal organs, brain, and heart. ARTERIOUVENOUS ANASTOMOSES: connection between arteries and veins. Ex vascular shunt in capillaries. VENOUS ANASTOMOSES: vein to vein. very common
30
What is blood flow?
Volume of blood flowing through a vessel, organ, or the entire circulation in a given minute. mL/min Relatively constant at rest
31
What is blood pressure?
Force per unit are exerted on the wall of a blood vessel by the blood. expressed in mm Hg
32
What drives blood flow?
the pressure gradient blood flows from high to low pressure
33
What is resistance (peripheral resistance)?
the opposition to flow. (friction)
34
What are the three most important sources of resistance in blood vessels?
Blood viscosity: inc viscosity -> inc resistance Total blood vessel length: inc length -> inc resistance Blood vessel diameter: dec diameter -> inc in resistance
35
How does resistance vary with vessel radius?
inversely to the 4th power Ex if radius is halved, resistance is increased by 16 times
36
What is the major determinant in peripheral resistance?
small diameter arterioles.
37
What is the relationship between blood flow and blood pressure and between blood flow and resistance?
Blood flow is directly proportional to the pressure gradient: inc pressure -> inc blood flow Blood flow is inversely proportional to resistance: inc resistance -> dec blood flow
38
Why is resistance more important in regulating local blood flow?
because it is more easily changed by altering the blood vessel diameter.
39
What is systolic pressure?
pressure exerted during ventricular contraction (systole)
40
What is diastolic pressure?
pressure exerted during ventricular diastole
41
What is pulse pressure
systolic pressure minus the diastolic pressure
42
What is the mean arterial pressure (MAP)?
average pressure that propels the blood through the body MAP = diastolic pressure + 1/3 pulse pressure
43
What is the vasa vasorum and where is it found?
They are small vessels found in the walls of larger vessels that nourish the more external tissues of the vessel wall. Vessel's of the vessels
44
What is an arteriovenous shunt?
it bypasses capillary beds to direct blood where it is needed. Ex when exercising, blood bypasses the digestive capillary beds to inc blood flow to the muscles
45
What is the blood pressure at the start of the capillaries and at the end and what is the significance of these values?
40 mm Hg entering 20 mm Hg leaving Low pressure is necessary because capillaries are fragile and otherwise too much fluid would be forced out of capillaries.
46
What can be said about venous blood pressure?
changes little during cardiac cycle low pressure gradient, about 15mm Hg low pressure is due to cumulative effects of peripheral resistance
47
How is venous return aided?
by the: action of skeletal muscles (squeeze vessels) and venous valves respiratory pump (inc in thoracic volume causes blood to enter area) vasoconstriction of veins
48
explain the short-term neural control mechanism for maintaining blood pressure
The brain will control the peripheral resistance with two main goals: 1) maintaining adequate MAP by altering blood vessel diameter 2) altering blood distribution to respond to specific demands The center that controls this in the vasomotor center It responds to changes in BP and chemical changes
49
What is the vasomotor control center (VCC)?
A cluster of sympathetic neurons in the medulla that oversee changes in blood vessel diameter. (part of the cardiovascular center) - receives input from baroreceptors, chemoreceptors, ad higher brain centers. - also maintains vasomotor tone
50
What is vasomotor tone?
it is a state of slight constriction in the blood vessels maintained by the sympathetic nerves connecting it to the vasomotor control center (VCC) that allows the VCC to relax/constrict the muscles to affect diameter. if BP rises - VCC decreases sympathetic stimulation to relax smooth muscle and inc diameter If BP drops - VCC increases stimulation and causes muscles to contract
51
What is a baroreceptor?
Increased blood pressure stimulates baroreceptors to increase input to the vasomotor center - this inhibits vasomotor causing arteriole dilation and venodilation - stimulates the cardoinhibitory center this is a negative feedback
52
Where are baroreceptors located and why these areas?
carotid sinuses, aortic arch, and large arteries of neck and thorax. These locations protect blood supply to the brain.
53
What are chemoreceptors?
located in the carotid sinuses, aortic arch, and large arteries of the neck respond to rise in CO2, drop in pH or O2 -> then inc BP via VCC and the cardioacceleratory center (CAC); VCC: inc constriction of vessels CAC: inc cardiac output more important in regulation of respiratory rate than BP
54
How do higher brain centers interact with blood pressure?
Higher brain centers can influence BP by influencing medulla, which houses BP regulation
55
What do adrenal medulla hormones do and give 2 examples.
EPNIEPHRINE, NOREPINEPHRINE cause generalized vasoconstriction and inc CO (inc BP)
56
What does atrial natriuretic peptide hormone (ANP) do?
causes blood volume and blood pressure to dec and causes general vasodilation (dec BP)
57
What does antidiuretic hormone do (ADH)?
causes intense vasoconstriction, stimulates kidneys to retain fluid. (inc BP) IMPORTANT IN LONG TERM BP REGULATION
58
What does angiotensin II do?
generated by kidney release of renin causes vasoconstriction (inc BP) IMPORTANT IN LONG TERM BP REGULATION
59
What are endothelium derived factors and what do they do?
Chemicals released from damaged vessels that cause vasoconstriction (inc BP) ex. endothelin and PDGF
60
What do inflammatory chemicals do?
from damaged tissues which cause vasodilation (dec BP) this inc blood flow to area.
61
What does alcohol do to blood pressure?
causes vasoconstriction (inc BP)
62
What is the long term control mechanism for blood pressure? Explain how it works.
RENAL REGULATION: control by altering blood volume -increased BP -> dec blood volume and vise versa There are two mechanisms: Direct Renal mechanism and indirect renal mechanism
63
Explain the direct renal mechanism.
It alters blood volume independently of hormones (by urine elimination) increased BP or blood volume causes increased elimination of urine-> decr blood volume -> dec BP decreased BP/blood volume causes reverse
64
What is the indirect renal mechanism?
also called the renin-angiotensin II mechanism dec in arterial BP -> release of renin by kidney renin -> causes production of angiotensin II affects of angiotensin II: - systemic vasoconstrictor (inc peripheral resistance->inc BP) - stimulates inc aldosterone secretion by adrenal cortex -> inc renal reabsorption of Na+ -> stimulates reabsorption of water -> inc blood volume and pressure - stimulates ADH by posterior pituitary -> inc reabsorption of water by kidney -> inc BP and volume
65
What is the normal range for BP in an adult at rest?
110-140 / 75-80 mm Hg
66
explain what happens to BP in the morning?
it is higher due to hormone levels BP cycles over a 24 hr period
67
What is hypotension and what are the 3 types?
it is low blood pressure (< 100 mm Hg) ORTHOSTATIC (temp low pressure because sympathetic nervous system cannot respond fast enough to changes in body position. Inc with old age) CHRONIC may be nutritional or hormonal ACUTE sign of circulatory shock
68
What is hypertension and what are the two types?
High blood pressure (140/90 or higher) may be an adaptation during fever, exertion, and emotional upset PRIMARY (ESSENTIAL) - 90% of cases. caused by hereditary, obesity, age, stress, diet, smoking, diabetes SECONDARY - less common. Causes kidney disease, arteriosclerosis, hormone disorders
69
What are the effects of long term hypertension?
Constant high blood pressure increases strain on heart and can cause heart failure, vascular disease, stroke, renal failure, and dec flow to the tissues over time
70
Why does blood flow slow in the capillaries?
to allow for material exchange between the blood and the tissues.
71
What is autoregulation and what are the three methods?
it is how organs regulate their own blood flow by dilating or constricting arterioles METABOLIC MYOGENIC ANGIOGENESIS (long-term autoregulation
72
what is the METABOLIC control mechanism (autoregulation)?
vasodilation of arterioles and relaxation off precapillary sphincters occur in response to: - declining tissue O2 levels - inc waste substances from tissues (H+, K+, CO2) how does it affect it? relaxation of vascular smooth muscle NO (nitrous oxide) released by endothelial cells (vasodilator) Vasoconstriction due to sympathetic stimulation and endothelins
73
What is the MYOGENIC control mechanism (autoregulation)?
Vascular smooth muscle responds directly to pressure and volume changes. (BP and volume cause changes in degree of stretch of smooth muscle) inc BV or BP -> dec stretch -> vasodilation -> inc flow to area and visa versa
74
What is ANGIOGENESIS?
also called long-term autoregulation. adaptations that develop when short term autoregulation cannot meet tissue demands - inc blood vessels in the region - existing vessels enlarge
75
When is ANGIOGENESIS common?
in the heart after a coronary vessel is occluded in people living at high altitudes
76
Describe blood flow in skeletal muscle at rest and during exercise.
at rest flow = 1L/min with 25% capillaries open During exercise flow is 10x greater this phenomena is called EXERCISE HYPEREMIA and results from dec O2 and inc metabolic waste
77
Describe the traits of cerebral flow.
is constant; neurons are intolerant of ischemia 750 mL/min neurons are very metabolically active and can not store nutrients Metabolic controls: dec pH, inc CO2 causes vasodilation Myogenic controls: decreased MAP -> cerebral vessels dialate. Inc MAP -> vessels constrict brain is vulnerable to extreme systemic pressure changes -MAP 160 mm Hg can cause cerebral edema
78
Describe blood flow through the skin.
autoregulated in response to O2 need Maintains body temp (neutrally controlled): temp inc hypothalamus signals medulla to reduce constriction of vessels -> blood flows to skin and heat is lost Sweat stimulates release of NO by endothelial cells (vasodilator) temp decreases -> sympathetic stimulation inc causing constriction sending blood to core Also has shunts that are thermoregulated that open when warm to allow inc flow to skin BLOOD FLOW VARIES FROM 50 mL/min and 2500 mL/min as needed
79
Describe blood flow through the lungs.
- short pathway (low arterial resistance and pressure) - arteries/arterioles are thin walled with large lumens (more like veins/venules) - autoregulation is reverse: dec O2 cause vasoconstriction and vice versa blood will be diverted away from low O2 areas in the lung because it is a sign of ineffective gas exchange.
80
Describe blood flow through the heart.
During diastole blood flows through coronary arteries to the myocardium during ventricular systole no blood can move through (heart relies on O2 stored in myoglobin during this phase) During strenuous exercise inc CO2 -> vasodilation -> inc blood flow 3-4x which maintains coronary perfusion
81
Describe blood flow through the capillaries.
slow and intermittent which reflects the on/off opening and closing of precapillary sphincters. controlled by autoregulation
82
How do materials move in and out of capillaries from tissue
mainly by diffusion from high to low concentration: - O2 and nutrients from blood to tissues - CO2 and metabolic waste from tissues to blood - lipid soluble molecules diffuse directly through the endothelial membranes - water soluble solutes pass through clefts and fenestrations large molecules move by active transport (endo/exo cytosis)
83
What does the direction and rate of fluid flow depend on in the capillaries?
it depends on two opposing forces: HYDROSTATIC pressures COLLOID OSMOTIC pressures
84
What are HYDROSTIC PRESSURES?
Two types: Capillary hydrostatic pressure (HPc) also called capillary blood pressure: it is the force that pushes fluid through capillary walls is greater at the arterial end of bed than at the venule end INTERSTITIAL fluid hydrostatic pressure (HPif) force that pushes fluid into capillaries (assumed 0 because of lymphatic vessels) so we consider the net
85
What are COLLOID OSMOTIC pressures?
pressure of osmosis CAPILLARY colloid osmotic pressure (OPc): created by nondiffusible plasma proteins which draw water toward themselves from interstitial fluid into capillary approx. 26 mm Hg INTERSTITIAL fluid osmotic pressure (OPif) force that tries to pull water into the tissue. very low (approx. 1 mm Hg) due to low protein content
86
What is the NET FILTRATION pressure (NFP)?
It is the net of all the pressures (trend of movement of fluid) acting on the fluid in the capillary bed. ``` NFP= net HP - net OP NFP = (HPc - HPif) - (OPc - OPif) ```
87
What is the trend of net filtration pressure at the beginning and end of the capillary beds?
at arterial end of bed: hydrostatic forces dominate and fluid moves out of capillary at venous end of bed: Osmotic forces dominate and fluid moves back into capillary
88
What is circulatory shock?
any condition in which: blood vessels are not adequately filled blood cannot circulate normally blood flow cannot meet tissue demands uncompensated shock can be fatal (5 kinds)
89
What is hypovolemic shock?
circulatory shock due to a large loss of blood
90
What is vascular shock?
extreme vasodilation and decreased peripheral resistance caused by anaphylactic allergic reaction
91
What is septic shock?
circulatory shock as a result of a severe bacterial infection. bacteria release toxins that cause vasodilation
92
What is cardiogenic shock?
results when an inefficient heart cannot sustain adequate circulation
93
What is transcient vascular shock?
can result after prolonged sunbathing (blood pools in skin) become dizzy when you stand up
94
What are the three circulations?
Pulmonary systemic coronary
95
What is the normal pattern for blood vessels?
vessels form two parallel networks (arterial and venous) with capillary beds joining the two. (blood flows through one capillary bed before returning for reoxygination)
96
What is a portal system for blood vessels?
blood passes through two capillary beds before returning to the heart 2 types: HEPATIC portal system: nutrient rich, oxygen poor blood from the capillary beds of the digestive tract is connected by the hepatic portal vein and carried to the capillary bed of the liver for processing before returning to the heart. PITUITARY portal system: connects hypothalamus with anterior pituitary
97
What are the differences between arteries and veins?
``` ARTERIES delivery: blood pumped into single systemic artery the aorta location: deep and protected by tissues pathways: fairly distinct supply/drainage: predictable supply ``` VEINS: delivery: blood returns via superior AND inferior vena cavae and the coronary sinus location: deep and superficial pathways: numerous interconnections supply/drainage: similar to arteries except dural sinuses and hepatic portal circulation

Anatomy and Physiology 111 (9 decks)

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