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Cardiovascular System > Lecture 7.2: The Peripheral Circulation > Flashcards

Lecture 7.2: The Peripheral Circulation Flashcards

1
Q

What percentage of blood is found in the Heart?

A

10%

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2
Q

What percentage of blood is found in Systemic Arteries?

A

10%

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3
Q

What percentage of blood is found in Capillaries?

A

5%

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4
Q

What percentage of blood is found in Large Systemic Veins?

A

20%

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5
Q

What percentage of blood is found in Small Veins and Venules?

A

43%

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6
Q

What percentage of blood is found in Pulmonary Circulation?

A

12%

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7
Q

What are the 3 layers of arteries and veins walls?

A
  • Tunica Intima
  • Tunica Media
  • Tunica Adventitia
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8
Q

What are the 3 different types of arteries?

A
  • Elastic Artery
  • Muscular Artery
  • Arteriole
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9
Q

Types of Arteries: Elastic Artery Structure

A
  • High proportion of elastic fibres
  • Internal elastic lamina separates
    tunic intima from tunica media
  • Tunica media contains significant
    amounts of elastin
  • Elastin allows expansion and recoil
  • Also known as conducting arteries
  • Generally>10mm diameter
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10
Q

Types of Arteries: Muscular Artery Structure

A
  • High proportion of smooth muscle
    (connected via gap junctions)
  • Innervated by sympathetic ANS
  • Around 0.1 to 10.0 mm diameter
  • Also called a distributing artery
  • Blood supply to the artery itself via
    vasa vasorum
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11
Q

Types of Arteries: Arteriole Structure

A
  • Arterioles are arteries that lead to a
    capillary bed
  • Only a few layers of smooth muscle
  • Resistance vessels
  • About 30μm in diameter
  • Display tone (degree of contraction
    of the smooth muscle)
  • A number of factors determine the
    degree of openness
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12
Q

What is a Metarteriole?

A

A short vessel linking arterioles and capillaries

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13
Q

What is a Pre-Capillary Sphincter?

A

The junction between a metarteriole and a capillary is called a pre-capillary sphincter and is characterised by smooth muscle
encircling it

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14
Q

What is Vasomotor Tone?

A

The end result of a complex set of interactions that control relaxation and contraction of blood vessels

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15
Q

Capillary Structure

A
  • Consist of a single layer of
    endothelium and basement
    membrane
  • Typically, less than 1 mm long
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16
Q

What are the 3 Types of Capillaries?

A
  • Continuous
  • Fenestrated
  • Sinusoid
17
Q

Types of Capillaries: Continuous

A
  • Most common
  • Tight junctions between endothelial
    cells
  • However, tight junctions are
    incomplete (intercellular clefts)
    allowing for movement of material
    between blood and tissues
  • Contribute to BBB (blood-brain-
    barrier)
18
Q

Types of Capillaries: Fenestrated

A
  • Has pores
  • Permeable to larger molecules
  • Found in small intestine and in the
    choroid plexus as well as elsewhere
19
Q

Types of Capillaries: Sinusoid

A
  • Least common
  • Flattened and incomplete
    basement membrane
  • Intercellular gaps
  • Facilitate movement of large
    molecules and cells between
    blood and interstitium eg bone
    marrow
20
Q

What types of molecules pass through the endothelium? What is this route called?

A
  • Gases
  • Small Lipophilic Molecules
  • Transcellular Route
21
Q

What types of molecules pass through pores (intercellular junctions, fenestrae)? What is this route called?

A
  • Water
  • Glucose
  • Ions
  • Paracellular Route
22
Q

What is the role of the Lymphatic System?

A

Maintains fluid levels in our body tissues by removing all fluids that leak out of our blood vessels, returns excess fluid back to the circulation

23
Q

What is interstitial fluid that enters lymph capillaries known as…?

A

Afferent Lymph

24
Q

What is the fluid called after passing through lymph nodes?

A

Efferent Lymph

25
Q

Where is efferent lymph returned to the circulation?

A
  • Via the thoracic duct and the right
    lymphatic duct
  • These enter the subclavian veins
26
Q

What is Diapedesis?

A

The passage of blood cells through the intact walls of the capillaries, typically accompanying inflammation

27
Q

Central Venous Pressure (CVP)

A
  • Veins act as a variable reservoir of
    blood
  • This means they can ‘add to’ larger
    veins
  • This increases CVP, stroke volume
    and arterial pressure
  • Volume sitting in the venous side of
    the circulation depends on venous
    blood pressure and the degree of
    tone in tunica media
28
Q

Smooth muscle in arterioles displays a tonic contraction (tone): what happens when there is an increase in tone?

A

Vasoconstriction

29
Q

Smooth muscle in arterioles displays a tonic contraction (tone): what happens when there is a decrease in tone?

A

Vasodilation

30
Q

Vasomotor tone principally produced by activity of the…?

A
  • The sympathetic ANS (α=receptor
    mediated)
  • NB Sympathetic cholinergic
    vasodilators in sweat gland (M3
    mediated)
  • NB Parasympathetic vasodilators eg
    salivary glands, erectile tissue (M2
    mediated)
  • BUT, also local control – a whole host
    of vasoactive metabolites (local
    chemicals for local vessels)
31
Q

Reactive Hyperaemia

A

Increase in blood flow following arterial occlusion

32
Q

Net fluid movement is driven by pressure gradient:

A
  • Capillary pressure (outward Pc)
  • Interstitial pressure (inward Pi)
  • Oncotic pressure of plasma proteins
    (inward πp)
  • Oncotic pressure of interstitium
    (outward πi)
  • Pressure = (Pc-Pi) – (πp-πi)
  • ~+28mmHg at the arterial end,
    ~+5mmHg at venous end
  • In total about 4-8 L exits the capillaries
    – how is balance maintained?

Cardiovascular System (19 decks)

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