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Anatomy 2 Unit 3 > 9 - Circulatory System Histology > Flashcards

9 - Circulatory System Histology Flashcards

1
Q

Major Function cardiovascular system

A

Transportation
Nutrients and Oxygen
Waste Products
Hormones

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2
Q

Left Side of Heart

A

Pump for the systemic circuit

Left Atrium – receives oxygenated blood

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3
Q

Right Side of Heart

A

Pump for the pulmonary circuit

Right Atrium – receives deoxygenated blood

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4
Q

The heart wall contains:

A

Cardiac muscle
Fibrous skeleton on the heart
Fibrous rings (4) that surround the valve orifices
Fibrous trigones (2) connecting the fibrous rings
Membranous portion of the interventricular and interatrial septa
Conducting system
Coronary vasculature
Serous membrane
Endothelial cells with underlying connective tissue

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5
Q

Epicardium –

A

outer layer

also known as the visceral layer of serous pericardium

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6
Q

Myocardium –

A

middle layer
composed primarily of the cardiac muscle
also contains the fibrous skeleton of the heart

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7
Q

Endocardium –

A

inner layer
Three components:
Endothelial cells – inner layer
Subendothelial Layer – middle layer; contains connective tissue & smooth muscle cells
Subendocardial layer – deeper layer; connective tissue layer containing the intrinsic conduction system

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8
Q

Two Atrioventricular Valves

A

(prevent backflow into atria):

1) Tricuspid Valve
2) Bicuspid or Mitral Valve
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9
Q

Two Semilunar Valves

A

(prevent backflow into ventricles):

1) Aortic Semilunar Valve
2) Pulmonary Semilunar Valve
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10
Q

Heart valves enforce one way blood flow through the heart and open/close in response to

A

pressure changes.

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11
Q

There are NO valves associated with

A

entrances of venae cavae, coronary sinus, and pulmonary veins into the heart!

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12
Q

Histology of Heart Valves:

A

Composed of connective tissue with overlying endocardium

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13
Q

Spongiosa –

A

loose connective tissue covered in endothelium; located on atrial or blood vessels side of valve; loosely arranged collagen and elastic fibers infiltrated with proteoglycans; shock absorber.

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14
Q

Fibrosa –

A

core of valve; contains fibrous extensions from the dense irregular connective tissue of skeletal rings of heart.

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15
Q

Ventricularis –

A

dense connective tissue with layers of elastic fibers covered in endothelium; adjacent to ventricular side of the valve.

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16
Q

The cardiac muscle of the heart is able to depolarize and contract without

A

impulses from the nervous system. Its ability to do so is because of the intrinsic cardiac conduction system.

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17
Q

Composed of the 1% noncontractile cardiac cells called

A

cardiac conducting cells or autorhythmic cells as they are self-excitable, meaning they can generate an action potential without nervous system input.

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18
Q

Two types of cardiac conducting cells:

A

Nodal cardiac cells
Purkinje fibers

These cells are organized into nodes and highly specialized conducting fibers/tracts.

These cells are responsible for the initiation and distribution of impulses throughout heart.

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19
Q

The rate of the intrinsic cardiac muscle contraction set by these pacemaker cells is altered by the

A

sympathetic (accelerates the heartbeat) and by the parasympathetic (decelerates the heartbeat) divisions of the autonomic nervous system; hormones can also impact intrinsic rate.

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20
Q

The following is the excitation sequence that takes place in collections of autorhythmic cardiac cells:

A
  1. Sinoatrial Node – pacemaker of heart; determines heart rate through its sinus rhythm. (Why?)
    ↓↓↓
    2) Atrioventricular Node – impulse travels to the atrioventricular node via the internodal pathway or tracts; impulse delayed here for ~0.1s to allow for the atria to contract.
    ↓↓↓
    3) Atrioventicular Bundle or Bundle of His – impulse travels from atrioventricular node to the right and left bundle branches; only electrical connection between atria and ventricles; travels across the fibrous skeleton.
    ↓↓↓
    4) Right and Left Bundle Branches – branches of the atrioventricular bundle; course toward apex of heart through interventricular septum.
    ↓↓↓
    5) Purkinje Fibers (a.k.a. Subendothelial Branches) – finish pathway in interventricular septum, around apex of heart, and head back towards atria.
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21
Q

Nodal Cardiac Muscle Cells : Found in the

A

SA and AV nodes

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22
Q

Nodal Cardiac Muscle Cells : Modified

A

cardiac muscle cells

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23
Q

Nodal Cardiac Muscle Cells : Smaller than surrounding

A

atrial contractile cardiac cells

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24
Q

Nodal Cardiac Muscle Cells : Contain fewer

A

myofibrils and lack intercalated discs

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25
Q

Purkinje Fibers: Found in

A

AV bundle, bundle branches, and subendothelial branches

See “Shotgun Histology Heart Purkinje Fibers” at

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26
Q

Purkinje Fibers: Modified

A

cardiac muscle cells

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27
Q

Purkinje Fibers: Larger than surrounding

A

ventricular contractile cardiac cells

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28
Q

Purkinje Fibers: Contain myofibrils at

A

periphery of cell

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29
Q

Purkinje Fibers: Nuclei are

A

round and larger than nuclei of regular cardiac fibers

Have associated intercalated discs

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30
Q

Purkinje Fibers: Positive for PAS staining because of large amount of

A

glycogen

With H&E – glycogen-rich center of cell appears homogenous and stains pale

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31
Q

The walls of blood vessels (except the smallest) have three layers or tunics:

A

interna, media, externa

32
Q

Tunica Interna or Tunica Intima

3 parts

A

Three Parts:

	a. endothelium
	b. basal lamina
	c. subendothelial layer

(internal elastic membrane – arteries and some arterioles

33
Q

Tunica Media – contains

A

rings of smooth muscles cells responsible for vasoconstriction and vasodilation; can also contain sheets or lamellae or laminae of elastin

(external elastic membrane – arteries)

34
Q

Tunica Externa or Tunica Adventitia – in larger vessels this tunic contains a

A

vasa vasorum and a nervi vascularis

35
Q

In cross section, arteries will appear more

A

open and veins more collapsed. Additionally, the lumen of the vein is much larger than that of the comparable artery.

36
Q

Arteries – thickest layer is the

A

tunica media

37
Q

Veins – thickest layer is the

A

tunica externa

38
Q

Elastic or Conducting Arteries (Large Arteries) –

A

largest diameter arteries (diameter greater than 10mm); walls contain large amounts of elastic fibers; allows arteries to expand and recoil; important vessels in helping to propel blood onward while ventricles are relaxing; elastic fibers function as pressure reserve.

39
Q

Muscular or Distributing Arteries (Medium Arteries) –

A

medium-sized arteries (2mm to 10mm diameter); walls contain large amounts of smooth muscle; important in regulating the blood flow to specific body regions; smooth muscle cells in circular orientation and are responsible for vasoconstriction (i.e. reduction in lumen diameter) and vasodilation (i.e. increase in lumen diameter).

40
Q

Small Arteries –

A

0.1mm to 2mm in diameter; as many as eight layers of smooth muscle in their tunica media.

41
Q

Arterioles –

A

smallest diameter artery; 10m to 100m diameter; only one or two layers of smooth muscle in the tunica media.

42
Q

Elastic or Conducting Arteries (Large Arteries) – dia. greater than

A

10mm

Tunica intima – has an inconspicuous internal elastic membrane
Tunica media – thickest layer; consists of multiple layers of smooth muscle cells separated by elastic lamellae
Tunica adventitia – thin; may contain a vasa vasorum and nervi vascularis

43
Q

Muscular or Distributing Arteries (Medium Arteries) – dia. 2mm to 10mm

A

Tunica intima – thinner than that of elastic arteries; has a prominent internal elastic membrane.
Tunica media – thickest layer; consists almost entirely of multiple layers of smooth muscle cells separated limited elastic material; has a prominent external elastic membrane.
Tunica adventitia – relatively thick; may contain a vasa vasorum and nervi vascularis.

44
Q

Small Arteries – dia. 0.1mm to 2mm

A

Tunica intima – typically has an internal elastic membrane
Tunica media – as many as eight layers of smooth muscle
Tunica adventitia – thin, ill defined

45
Q

Arterioles – dia. 10m to 100m

A

Tunica intima – may or may not have an internal elastic membrane
Tunica media – only one or two layers of smooth muscle
Tunica adventitia – thin, ill defined

46
Q

Capillaries

A

Smallest diameter of blood vessels; 4μm-10μm.
Thin wall – endothelial cell and its basal lamina.
Their main role is to allow the exchange of materials between the blood and body tissues.

47
Q

Three types of capillaries based on their morphology:

A

Continuous capillaries
Fenestrated capillaries
Discontinuous capillaries (a.k.a. sinusoidal capillaries or sinusoids)

48
Q

Continuous Capillaries

A

Found in muscle, lung, and central nervous system
Uninterrupted endothelial cell lining with tight or occluding junctions
See pinocytotic vessels
May see associated pericytes

49
Q

Fenestrated Capillaries

A

Found in endocrine glands and at sites of fluid and metabolite absorption
Have oval pores (80nm to 100nm in diameter) called fenestrations
See pinocytotic vessels

50
Q

Discontinuous Capillaries (a.k.a. sinusoidal capillaries or sinusoids)

A

Found in the liver, spleen, and bone marrow

Larger diameter and more irregularly shaped than other capillaries

51
Q

The flow of blood from an arteriole through a capillary network to a postcapillary venule is called

A

microcirculation. Three items (i.e., the arteriole, the capillary network, and the postcapillary venule) form a functional unit called the microcirculatory bed or microvascular bed.

52
Q

Two Types of Vessels in the Capillary Network:

A

True Capillaries
Arteriovenous (AV) Anastomoses or Shunts
(a.k.a. Metarteriole-Thoroughfare Channel)

53
Q

The More the Precapillary Sphincters Relax (and the smooth muscle of the AV shunt contract)  the more

A

blood will pass through the true capillaries in the capillary beds.

54
Q

The More the Precapillary Sphincters Contract (and the smooth muscle of the AV shunt relax)  the more

A

blood will pass through the arteriovenous anastomoses and bypass the true capillaries.

55
Q

There are four types of veins:

A

venule, small, med large

56
Q

Venule –

A

smallest diameter veins (diameter of 10μm to 100 μm); receive blood from capillaries; two types:
Postcapillary Venule – endothelial cell with basal lamina and pericytes; no tunica media and no adventitia.
Muscular Venule – possess a tunica media with one or two layers of smooth muscle and a thin tunica adventitia; typically no pericytes here.

57
Q

Small Veins – 0.1mm to 1mm in diameter; receive

A

blood from muscular venule.

58
Q

Medium Veins – 1mm to 10mm in diameter; all

A

three layers present.

59
Q

Large Veins – larger than 10mm in diameter;

A

all three layers present

60
Q

Medium Veins – dia. 1mm to 10mm

A

Tunica intima – endothelium and its basal lamina, thin subendothelial layer with an occasional smooth muscle cell, and, in some cases, a thin internal elastic membrane.
Tunica media – thinner than the associated artery; several layers of smooth muscle (most circularly arranged, with the occasionally longitudinally arranged) with interspersed collagen and elastic fibers.
Tunica adventitia – thicker than the intima and media; collagen and networks of elastic fibers.

61
Q

Large Veins – dia. greater than 10mm

A

Tunica intima – endothelium and its basal lamina, along with thin subendothelial layer with some smooth muscle cells.
Tunica media – relatively thin; circularly arranged smooth muscle cells
Tunica adventitia – thicker than the intima and media; collagen and elastic fibers with an occasional smooth muscle cell.

62
Q

Most veins in limbs have valves (i.e.,

A

thin folds of tunica intima; endothelial cells over a thin layer of connective tissue) that prevent backflow of blood.

63
Q

Serous membrane formed by

A

specialized squamous epithelium - mesothelium on loose connective tissue

64
Q

Pericardium viscera has

A

nerves and blood vessels

65
Q

Subendocardial layer has

A

conduction - purkinje fibers found here

66
Q

IF you look at heart anteriorly, pulmonary trunk in front

A

looks a bit like a T

67
Q

Spongiosa facing outflow is

A

arterialis

68
Q

Atria spongiosa

A

auricularis **

69
Q

Spongiosa collagen dampens

A

vibration of valve opening and closing

70
Q

AV BUNDLE OF HIS

A

ONLY ELEcrtical signal between atrium and ventricle - no gap junctions between cells of atrium and ventricle

71
Q

If SA node is damaged, than

A

AV node takes over

72
Q

Tunica interna- internal elastic membrane

A

exactly as it sounds, at the interior of some tunica internas (usually on larger arteries/veins)

73
Q

external elastic membrane

A

between tunica media and externa

74
Q

Endothelium long axis in the direction of

A

bloodflow

75
Q

Muscular arteries external elastic membrane

A

a bit sporadic - fibers in many different directions

76
Q

continuous capillaries

A

have pinocytotic vessels carry things across ONLY

77
Q

Pericytes in

A

basal lamina - unspecialized stem cell. Can form endothelial or smooth muscle cells - in continuous cap, help in vessel growth.

Anatomy 2 Unit 3 (14 decks)

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