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Histology > Histology of the Cardiovascular System > Flashcards

Histology of the Cardiovascular System Flashcards

1
Q

What is the main role of the circulatory system?

A

Pumps and directs blood cells and substances carried in the blood to all tissues of the body

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2
Q

Main components of the circulatory system.

A
  • heart, arteries, capillaries, veins

- blood and lymphatic vascular systems

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3
Q

Characteristics of Arteries

A
  • a series of vessels efferent from the heart
  • become smaller as they branch into various organs
  • carry blood to the tissues
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4
Q

Characteristics of Veins

A
  • carry blood back to the heart to be pumped again

- organized in the pulmonary circulation and the systemic circulation

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5
Q

Characteristics of Capillaries

A
  • smallest vessels
  • sites of O2, CO2, nutrient, and waste product exchange between blood and tissues
  • form a complex network of thin, anastomosing tubules called the microvasculature (in almost every organ)
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6
Q

How are Veins formed?

A

Results from the convergence of venules into a system of larger channels

Continue enlarging as they approach the heart

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7
Q

What are the two types of circulation?

A

(1) Pulmonary Circulation

(2) Systemic Circulation

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8
Q

Pathway of Pulmonary Circulation

A

The right side of the heart pumps blood through pulmonary vessels, through the lungs for oxygenation

Comes back to the left side of the heart

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9
Q

Pathway of Systemic Circulation

A

Pumps blood from the left side of the heart through vessels

Supplies either the head and arms or the lower body

Comes back to the right side of the heart

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10
Q

What are the 3 layers of heart chambers?

A

(1) Internal endocardium
(2) Middle myocardium
(3) External epicardium

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11
Q

What are the histological characteristics of the endocardium?

A
  • endothelium
  • a thin layer of connective tissue with smooth muscle cells
  • subendocardial layer
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12
Q

What are the histological features of the subendocardial layer?

A

Lies below the endothelium and myoelastic layer

Contains the conducting (Purkinje) fibers in the ventricles

Myofibrils are displaced to the periphery due to glycogen filling much of the cytoplasm

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13
Q

What are Purkinje Fibers?

A

Cardiac muscle cells joined by intercalated disks

Role: specialized for impulse conduction

In the atria, Purkinje fibers are closer to the endothelium and intermingle with the contractile fibers within the myocardium

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14
Q

Give the histological features of epicardium (aka. visceral pericardium)

A
  • forms the external tunic of the heart
  • site of coronary vessels
  • contains considerable adipose tissue
  • consists of loose connective tissue containing autonomic nerves and variable amount of fat
  • covered by simple mesothelium that also lines the pericardial space
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15
Q

What cells are responsible for the secretion of the pericardial fluid?

A

Mesothelial cells secrete a lubricant fluid

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16
Q

What is the significance of pericardial fluid?

A

This fluid prevents friction as the beating heart contacts the parietal pericardium on the other side of the pericardial cavity

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17
Q

What is the role of the cardiac skeleton?

A

Connective tissue:

  • anchors the valves
  • surrounds the two atrioventricular canals, maintaining their proper shape
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18
Q

Histology of the cardiac skeleton

A

dense irregular CT, primarily in the endocardium

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19
Q

Where do Chordae Tendineae attach?

A

Chordae tendineae attach to the atrioventricular valve

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20
Q

What is the histology of Chordae tendineae?

A

These structures are largely dense connective tissue covered with a thin layer of endothelium

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21
Q

What are the 3 tunics of arteries and veins?

A

(1) Intima
(2) Media
(3) Adventitia (or externa)

(these tunics correspond roughly to the heart’s endocardium, myocardium, and epicardium

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22
Q

How do arteries and veins differ?

A

ARTERIES: thicker media, relatively narrow lumen

VEINS: larger lumen, adventitia is the thickest layer, intima of veins is often folded to form valves

CAPILLARIES: only an endothelium, with no subendothelial layer or other tunics

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23
Q

What is the role of the internal elastic lamina

A

Separate the intima from the media

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24
Q

What is elastic lamina comprised of?

A
  • internal elastic lamina = a sheet of elastic
  • Simple squamous endothelial cells line the intima that has subendothelial loose connective tissue
  • media contains many elastic lamellae and elastic fibers alternating with layers of smooth muscle
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25
Q

Compare the histological features of a LARGE artery and vein.

A
  • media is much thicker in large arteries than veins, with relatively more elastin
  • elastic fibers are also present in the outer tunica adventitia, which is relatively thicker in large veins
  • the adventitia of large arteries is also supplied more sparsely with small sympathetic nerves for control of vasoconstriction
  • media also has muscle fibers and elastic lamellae
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26
Q

Where is the vasa vasorum?

A

Vasa vasorum are seen in the adventitia of the aorta

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27
Q

What is the vasa vasorum’s role?

A

The microvessels bring O2 and nutrients to local cells that are too far form the lumen to be nourished by blood there

28
Q

What is the vasa vasorum comprised of?

A

It is the microvasculature of the adventitia of larger arteries (aorta): capillaries, arterioles, and venules

29
Q

What are the histological features of elastic artery?

A
  • a large elastic artery shows a thick media with many well-developed elastic lamellae
  • the intima of the empty aorta is typically folded
  • the dense irregular conenctive tissue of the adventitia is thinner than the media
30
Q

What is the advantage of elastic lamellae in elastic arteries?

A
  • the largest arteries contain considerable elastic material and expand with blood when the heart contracts
  • strong pressure of blood pulsating into such arteries during systole expands the arterial wall
  • this expansion reduces the pressure and allows strong blood flow to continue during diastole
31
Q

Where is the glomus body located?

A

The glomus bodies are two small (0.5-5mm diameter) ganglion-like structures found near the common carotid arteries

32
Q

What is the glomus body comprised of?

A
  • large capillaries intermingled with clusters of large glomus cells
  • glomus cells filled with vesicles of various neurotransmitters
  • supportive satellite cells with elongated nuclei that ensheath each glomus cell
33
Q

What is the role of the glomus body?

A
  • specialized regions in the walls of certain elastic arteries contain tissues acting as chemoreceptors
  • chemoreceptors - provide information to the brain regarding blood chemistry
34
Q

What do glomus cells sense and how is the message relayed to the brain?

A

Glomus cells form synaptic connections with sensory fibers

Significant changes in the blood CO2, O2, or H+ concentrations are detected by these chemoreceptive cells

Release a neurotransmitter that activated the sensory nerve to relay this information to the brain

35
Q

What are the histological features of the muscular artery?

A

Arteries have relatively less elastin and more smooth muscle in their walls

Slightly folded intima with only sparse connective tissue between the endothelial cells and internal elastic lamina

Multiple layers of smooth muscle in the media that are thicker than the elastic lamellae and fibers

Vasa vasorum are seen in the adventitia

(most arteries are of mucular type)

36
Q

What are the components of microvasculature?

A

Arterioles

Capillaries

Venules

37
Q

What is the significance of microvasculature?

A

In almost every organ, molecular exchange takes place between blood and the interstitial fluid of the surrounding tissues

38
Q

What are the histological features of capillaries?

A

Lack media

Adventitia tunics with diameters of only 4-10um

39
Q

How are capillaries identified?

A

Can be recognized by nuclei adjacent to small lumens or by highly eosinophillic red blood cells in the lumen

40
Q

What are the histological features of lymphatic vessels?

A

Thin-walled

Irregularly shaped

41
Q

What is the role of lymphatic vessels?

A

Help in draining interstitial fluid

42
Q

Give the histological features of arterioles.

A

Classified as microvessels

Can be various sizes

Intima - consists of only endothelium comprised of cells with rounded nuclei

media - consists of only 1-2 layers of smooth muscle

Have thin inconspicuous adventitia

Adventitia merges with neighboring connective tissue

43
Q

Give the histological features of a large mesenteric arteriole

A

Endothelial cells

1-2 layers of smooth muscle cells

44
Q

What are the histological features of capillaries?

A

Consist only of an endothelium across which molecular exchange occurs between blood and tissue fluid

Endothelial cells have more flattened nuclei in capillaries

Normally associated with perivascular contractile cells: pericytes

45
Q

What are pericytes

A

Perivascular contractile cells

Have a variety of functions, but ultimately a symbiotic relationship with endothelial cells

46
Q

What are the histological characteristics of pericytes?

A

Bigger nuclei than endothelial cells

47
Q

How are pericytes and endothelial cells of capillaries differentiated?

A

The more flattened nuclei belong to endothelial cells

48
Q

What are the 3 types of capillaries and their common location?

A

CONTINUOUS CAPILLARY: common in almost all organ systems

FENESTRATED CAPILLARY: intestinal walls, choroid plexus, restricted to endocrine organs

SINUSOID CAPILLARY: bone marrow, liver, spleen

49
Q

What are the histological features of a continuous capillary?

A

Does NOT have any perforations

  • a prominent endothelial cell nucleus
  • abundant tight or occluding junctions in the junctional complexes at folds between the endothelial cells
  • numerous transcytotic vesicles
50
Q

What are the advantages of a continuous capillary?

A

Exert the tightest control over what molecules enter and leave the capillary lumen

All the material that crosses continuous capillary endothelium must pass through the cells, usually by diffusion or transcytosis

51
Q

What is the advantage of a fenestrated capillary?

A

Specialized for uptake of molecules such as hormones in endocrine glands or for outflow of molecules, such as in kidney’s filtration system

Allows a freer exchange of molecules than continuous capillaries

52
Q

What are the histological features of a fenestrated capillary?

A
  • Typical fenestrae closed by diaphragms
  • a continuous basal lamina surrounding the endothelial cell
  • Golgi apparatus, nucleus, and centrioles
53
Q

What are the main features of sinusoidal capillaries?

A
  • have a much greater diameter than most capillaries
  • surrounded by tissue containing adipocytes and masses of hematopoietic cells (in bone marrow)
  • the endothelial cells are very thin
  • cell nuclei are more difficult to find than in smaller capillaries
  • have large fenestrations through cells
  • large discontinuities between the cells and through the basal lamina
54
Q

What are the specialized roles of Sinusoidal capillaries?

A
  • maximal molecular exchange between blood and surrounding tissue
  • easy movement of blood cells across the endothelium
55
Q

What are the differences between an arteriole and a venule?

A
  • venules are larger and more organized
  • venules lie between capillaries and veins
  • postcapillary venules have large lumens compared to arterioles and intima of simple endo-cells with occasional pericytes
  • larger collecting venules have much greater diameters than arterioles
  • arterioles have thicker walls than venules
56
Q

What are the main features of a muscular venule?

A
  • a better defined tunica media
  • 3 layers of smooth muscle in some areas
  • a very thin intima of endothelial cells
  • a more distinct adventitia
57
Q

What are the main features of a small vein?

A
  • relatively large lumen compared to the small muscular artery (artery has a thick media and adventitia)
  • its wall is very thin (contains only 2-3 layers of smooth muscle)
  • valves
58
Q

How are valves formed?

A

Valves are thin folds of intima projecting well into the lumen of a vein

Act to prevent backflow of blood

59
Q

How is interstitial fluid formed?

A

Produced when plasma forced from the microvasculature by hydrostatic pressure

All of this fluid does not return to blood by the action of osmotic pressure

60
Q

What is lymph composed of?

A

Rich in proteins and other materials

61
Q

What are the main histological features of lymphatic capillaries?

A

Wall of endothelial cells - quite variable in diameter (10-50um)

Filled with lymph

Openings between endo-cells (that are held in place by anchoring filaments containing elastin - where interstitial fluid enters)

Lymphatic endothelial cells are typically larger than those of blood capillaries

62
Q

What are the differences between a venule and a lymphatic vessel?

A

Lymphatic vessels: have very thin walls - formed by the merger of lymphatic capillaries

Venules have thick walls compared to lymphatic vessels

Lymphatic vessels do not contain red blood cells (in contrast to venules)

There is a valve that is resonsible for the unidirecitonal flow of lymph

63
Q

What are the changes happening in an atherosclerotic artery that can contribute to ischemic heart disease?

A
  • Atheromatous deposits in the coronary arteries (of adults)
  • Asymptomatic, but can progress
  • Cause acute myocardial infarction and its complications: dysrhythmia, heart failure
64
Q

What are the 2 main consequences of coronary atherosclerosis?

A

ANGINA - chest pain caused by cardiac ischemia

MYOCARDIAL INFARCTION

65
Q

What is angina?

A

A type of temporary chest pain, pressure, or discomfort

Pain: chest, arm, and neck (due to exertion, cold, and excitement)

Caused when the oxygen supply to the myocardium is insufficient

66
Q

What are the changes in a coronary artery that can lead to myocardial infarction?

A

Coronary arteries become blocked by thrombus - lipid deposits once they start forming also attract platelets, then a clot can form

Cardiac myocytes rely on aerobic metabolism, and they die if ischemia occurs from thrombus

67
Q

What are the 2 common consequences of myocardial infarction?

A

Common cause of death:

(1) Mechanical failure of the ventricle
(2) Dysrhythmia - electrical system going haywire and pumping lots

Histology (3 decks)

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