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CHI 108 > Lecture 20: Blood Vessels > Flashcards

Lecture 20: Blood Vessels Flashcards

1
Q

Describe the three kinds of vessels found in the body and give their function

A

Arteries: carries blood away from the heart; oxygenated except for pulmonary circulation and umbilical vessels of fetid
Capillaries: contact tissue cells and directly serve cellular needs
Veins: carry deoxygenated blood towards the heart

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2
Q

Structure of blood vessel walls:
Arteries and veins
Lumen
Capillaries

A

Arteries and veins:
-Tunica intima: endothelium lines the lumen of all vessels
-Tunica media: smooth muscle and sheets of elastin.
-Tunica externa: collagen fibres protect and reinforce
Lumen: central blood containing space
Capillaries: endothelium of one cell thickness
Refer to slide 6 for image

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3
Q

Elastic arteries:

A
  • Large thick walled arteries with elastin in all three tunics
  • aorta and its major branches
  • large lumen offers low resistance
  • acts as pressure reservoirs- expand and recoil as blood is ejected from the heart
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4
Q

Muscular arteries and arterioles

A
  • Distal to elastic arteries; deliver blood to body grabs
  • have thick tunica media with more smooth muscle
  • arterioles: smallest arteries and lead to capillary beds
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5
Q

Capillaries

A

Microscopic blood vessels

  • walls of thin tunica intima, only one cell thick
  • size of lumen allow only a single red blood cell to pass at a time
  • found in all tissues except for cartilage, epithelia, cornea and lens of eye
  • functions: exchange of gases, nutrients, wastes, hormones etc
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6
Q

What are the three structural types of capillaries?

A
  1. Continuous capillaries: tight junctions connect endothelial cells: in blood brain barrier.
    -intercellular clefts allow for passage of fluids and small solutes
  2. Fenestrated capillaries:
    -some endothelial cells contain pores (fenestrations)
    -more permeable than continuous capillaries
    -function in absorption or filtrate formation (small intestine, endocrine glands and kidneys)
  3. Sinusoidal capillaries:
    -fewer tight junctions, larger intercellular clefts, larger lumens
    -allow large molecules and blood cells to pass between blood and surrounding tissue
    -found in liver, bone marrow and spleen
    Refer to slides 13-15 for pictures
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7
Q

Venules:

A
  • Formed when capillary beds unite
  • very porous; allow fluid and WBCs into tissues
  • larger venules have one or two layers of smooth muscle cells
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8
Q

Veins:

A
  • formed when venules converge
  • have thinner walls, larger lumen compared with arteries
  • blood pressure is lower than in arteries
  • thin tunica media and thick tunica externa consisting of collagen fibres and elastic networks
  • blood reservoirs; contain about 60% of the blood volume
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9
Q

What are the veins adaptions that ensure return of blood to he heart?

A
  1. Large diameter lumens offer little resistance
  2. Valve prevents backfow of blood
    -most abundant in veins of the limbs
    Venous sinuses: flattened veins with extremely thin walls eg coronary sinus of the heart and dural sinuses of the brain)
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10
Q

Vascular anastomoses:

A

-interconnections of blood vessels
Arterial anastomoses provide alternative pathways to a given body region
-common at joints, in abdominal organs, brain, and heart
Vascular shunts of capillaries shunts of capillaries are examples of arteriovenous anastomoses
-venous anastomoses are common

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11
Q

Factors aiding in venous return

A
  1. Respiratory pump: pressure changes created during breathing moves blood towards the heart be squeezing abdominal veins as thoracic veins expand
  2. Muscular pump: contraction of skeletal muscles “milk” blood toward the heart and valves prevents backfow
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12
Q

The Vasomotor centre

A

A cluster of sympathetic neurons in the medulla oblongata that oversee changes in blood vessel diameter
-part of the cardiovascular centre
Receives input from:
-baroreceptors: walls of large arteries of the neck and thorax ie carotid and aorta
-chemoreceptors: large arteries of neck ie carotid and aorta, chemoreceptors respond mainly to rise in CO2

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13
Q

Short term mechanisms: hormonal control

A 
Adrenal medulla hormones: 
-norepinephrine 
-epinephrine 
Kidney: 
-angiotensin 2
Posterior pituitary: 
-antidiuretic hormone (vasopressin)
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14
Q

Monitoring circulatory efficiency:

A 
Vital signs: pulse and blood pressure, along with respiratory rate and body temperature 
Pulse: pressure wave caused by the expansion and recoil of arteries
Need to identify the following pulses: 
-radial pulse
-ulnar pulse 
-carotid pulse
-brachial pulse 
-femoral pulse 
-dorsal pedal pulse 
-posterior tibia pulse
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15
Q

Systemic blood pressure:

A

The pumping action of the heart generates blood flow
-pressure results when flow is opposed by resistance of the arterial wall
Systemic pressure:
-is highest in the aorta
-declines throughout the pathway
-is 0mm Hg in the right atrium

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16
Q

Arterial blood pressure:

A

Reflects two factors of the arteries close to the heart
-elasticity
-volume of blood forced into them at any time
Systolic pressure: pressure exerted during ventricular contraction
Diastolic pressure: lowest level of arterial pressure

17
Q

Blood flow: brain

A

Blood flow to the brain is constant, as neurons are intolerant of ischemia
-capillaries have tight junctions and are continuous, thus protective as the blood: brain barrier

18
Q

Blood flow: skin

A

Blood flow through the skin:

  • supplies nutrients to cells
  • helps maintain body temperature
  • provides a blood reservoir
  • is controlled by sympathetic nervous system reflexes, initiated by temperature receptors and the central nervous system
19
Q

Temperature regulation

A

As temperature rises

  • hypothalmic signals reduce vasomotor stimulation of the skin vessels
  • heat radiates from the skin
  • sweat also causes vasodilation

As temperature decreases, blood is shunted to deeper, more vital organs

20
Q

Blood flow: lungs

A

Pulmonary circuit is unusual in that:

  • the pathway is short
  • arteries/ arterioles are more like veins/ venules (thin walled, with large lumens)
  • arterial resistance and pressure is low
21
Q

Blood flow: heart
During ventricular systole
During strenuous exercise

A 
During ventricular systole:
-coronary vessels are compressed 
-myocardial blood flow ceases
During strenuous exercise
-coronary vessels dilate 
-blood flow may increase
22
Q

Differences between arteries and veins:

A

H

CHI 108 (24 decks)

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