THE CIRCULATORY SYSTEM

Question 1

The blood vascular system, or cardiovascular system, consists of the following structures:

Answer 1

heart
Arteries
Capillaries
Veins

Question 2

The blood vascular system, or cardiovascular system, consists of the following structures:

The ______ propels blood through the system.

Answer 2

heart

Question 3

The blood vascular system, or cardiovascular system, consists of the following structures:

______, a series of vessels efferent from the heart that become smaller as they branch into the various organs, carry blood to the tissues.

Answer 3

Arteries

Question 4

The blood vascular system, or cardiovascular system, consists of the following structures:

______, the smallest vessels are sites of oxygen, carbon dioxide, nutrients, & waste product exchange between blood & tissues.

Answer 4

Capillaries

Question 5

The blood vascular system, or cardiovascular system, consists of the following structures:

______ result from the convergence of venules into a system of larger channels which continue enlarging as they approach the heart, toward which they carry the blood to be pumped again.

Answer 5

Veins

Question 6

Together with the smallest arterial & venous branches carrying blood to & from them capillaries in almost every organ form a complex network of thin, anastomosing tubules called the ______ or ______.

Answer 6

microvasculature, microvascular bed

Question 7

two major divisions of arteries, microvasculature, and veins make up the ______, where blood is oxygenated in the lungs, and the ______, where blood brings nutrients and removes wastes in tissues throughout the body.

Answer 7

pulmonary circulation, systemic circulation

Question 8

The lymphatic vascular system, introduced with the discussion of interstitial fluid, begins with the ______, which are thin-walled, closed-ended tubules carrying lymph which merge to form vessels of steadily increasing size.

Answer 8

lymphatic capillaries

Question 9

The ______ connect with the blood vascular system and empty into the large veins near the heart.
This returns fluid from tissue spaces all over the body to the blood.

Answer 9

largest lymph vessels

Question 10

The internal surface of all components of the blood and lymphatic systems is lined by a ______ called ______.

Answer 10

simple squamous epithelium, endothelium

Question 11

As the interface between blood and the organs, ______ cells have crucial physiologic and medical importance

Answer 11

cardiovascular endothelial

Question 12

Not only must ______ maintain a selectively permeable, antithrombogenic (inhibitory to clot formation) barrier, they also determine when and where white blood cells leave the circulation for the interstitial space of tissues and secrete a variety of paracrine factors for vessel dilation, constriction, and growth of adjacent cells.

Answer 12

endothelial cells

Question 13

______ in the four chambers of the heart wall contracts rhythmically, pumping the blood through the circulatory system.

Answer 13

Cardiac muscle

Question 14

The right and left ______ propel blood to the pulmonary and systemic circulations.

Answer 14

ventricles

Question 15

right and left ______ receive blood from the body and the pulmonary veins, respectively.

Answer 15

atria

Question 16

The walls of all four heart chambers consist of three major layers: the ______, the ______, and the ______.

Answer 16

internal endocardium, middle myocardium, external epicardium

Question 17

The walls of all four heart chambers consist of three major layers:

The ______ consists of the lining endothelium, its supporting layer of fibroelastic connective tissue with scattered fibers of smooth muscle, and a deeper layer of connective tissue (continuous with that of the myocardium and often called the ______) surrounding variable numbers of modified cardiac muscle fibers which comprise the heart’s impulse conducting system.

Answer 17

endocardium, subendocardial layer

Question 18

The walls of all four heart chambers consist of three major layers:

The ______ consists mainly of typically contractile cardiac muscle fibers arranged spirally around each heart chamber.

Answer 18

myocardium

Question 19

Because strong force is required to pump blood through the systemic and pulmonary circulations, the myocardium is much thicker in the walls of the ______, particularly the ______, than in the atrial walls.

Answer 19

ventricles, left

Question 20

The walls of all four heart chambers consist of three major layers:

The ______ is a ______ supported by a layer of loose connective tissue containing blood vessels and nerves.

Answer 20

epicardium, simple squamous mesothelium

Question 21

The epicardium corresponds to the ______ of the ______, the membrane surrounding the heart.

Answer 21

visceral layer, pericardium

Question 22

Where the large vessels enter and leave the heart, the epicardium is reflected back as the ______ lining the pericardium.

Answer 22

parietal layer

Question 23

During heart movements, underlying structures are cushioned by deposits of ______ tissue in the ______ and friction within the ______ is prevented by lubricant fluid produced by both layers of ______ cells.

Answer 23

adipose, epicardium, pericardium, serous mesothelial

Question 24

Prominent ______ tissue comprising the fibrous ______ separates the musculature of the atria from that of the ventricles, forms part of the ______ and ______ septa, and extends into the ______ and the ______ to which they are attached.

Answer 24

dense irregular connective, cardiac skeleton, interventricular, interatrial, valve cusps, chordae tendineae

Question 25

Various regions of the cardiac skeleton have the following functions:

Answer 25

• Surrounding, anchoring, and supporting all heart valves;
• providing firm points of insertion for cardiac muscle in
• the atria and ventricles; and
• helping coordinate the heartbeat by acting as electrical
• insulation between atria and ventricles.

Question 26

In both the subendocardial layer and the adjacent myo-cardium, modified ______ cells make up the impulse ______, specialized to generate and conduct waves of depolarization which stimulate rhythmic contractions in adjacent myocardial fibers.

Answer 26

cardiac muscle, conducting system of the heart

Question 27

conducting system of the heart

This system consists of two nodes of specialized myocardial tissue in the right atrial wall: the ______ (or ______) and the ______, from which the ______ (bundle of ______) emerges.

Answer 27

sinoatrial (SA) node, pacemaker, atrioventricular (AV) node, AV bundle, His

Question 28

Located in the right atrial wall near the superior vena cava, the SA node is a ______ region of less well-stained cardiac muscle cells with smaller size, fewer myofibrils, and fewer typical intercalated disks than the neighboring contractile fibers.

Impulses initiated by these cells move along myocardial fibers of both ______, stimulating their contraction.

Answer 28

6- to 7-mm3, atria

Question 29

When the impulses reach the slightly smaller ______, located in the floor of the right atrium near the AV valve and composed of cells similar to those of the SA node, they stimulate ______ there.

Answer 29

AV node, depolarization myocytes

Question 30

From the AV node conducting myocytes are grouped into the ______, which passes through an opening in the cardiac skeleton into the ______ where it bifurcates into left and right bundles of ______ located within the myocardium and subendocardial layer.

At the apex of the heart, these bundles subdivide further into a subendocardial conducting network of cardiac muscle fibers, usually called ______.

Answer 30

AV bundle, interventricular septum, myocytes, Purkinje fibers

Question 31

______
- These are pale-staining fibers, larger than the adjacent contractile fibers, with sparse, peripheral myofibrils, and much glycogen.

Answer 31

Purkinje fibers

Question 32

______ mingle distally with contractile muscle fibers of each ventricle and trigger waves of contraction through both ventricles simultaneously.

Answer 32

Purkinje fibers

Question 33

Both ______ and ______ neural components innervate the heart. ______ nerve cells and nerve fibers are present in the regions close to the SA and AV nodes, where they affect heart rate and rhythm, such as during physical exercise and emotional stress.

Answer 33

parasympathetic, sympathetic, Ganglionic

Question 34

Stimulation of the ______ division (______ nerve) slows the heartbeat, whereas stimulation of the ______ nerve accelerates activity of the pacemaker. Between fibers of the myocardium are ______ free nerve endings that register pain, such as the discomfort called ______ that occurs when partially occluded coronary arteries cause local oxygen deprivation.

Answer 34

parasympathetic, vagus, sympathetic, afferent, angina pectoris

Question 35

Abnormalities in the structure of heart valves can be produced by developmental defects, scarring after certain infections, or cardiovascular problems such as hypertension.
Such abnormal valves may not close tightly, allowing slight regurgitation and backflow of blood.
This produces an abnormal heart sound referred to as a ______.

Answer 35

heart murmur

Question 36

If the valve defect is severe, the heart will have to work harder to circulate the normal amount of ______, eventually enlarging to accommodate the increased workload.

Answer 36

blood

Question 37

Defective heart valves often may be repaired ______ or replaced by an ______ or one from a large ______.
Because such valve replacements lack a complete ______ covering, the patients require ______ agents to prevent thrombus formation at these sites.

Answer 37

surgically, artificial valve, animal donor, endothelial, exogenous anticoagulant

Question 38

Walls of all blood vessels except capillaries contain ______ and ______ in addition to the endothelial lining.
The amount and arrangement of these tissues in vessels are influenced by ______ factors, primarily blood pressure, and ______ factors reflecting the local needs of tissues.

Answer 38

smooth muscle, connective tissue, mechanical, metabolic

Question 39

The ______ is a specialized epithelium that acts as a semipermeable barrier between two major internal compartments: the ______ and the ______.

Answer 39

endothelium, blood, interstitial tissue fluid

Question 40

______ cells are squamous, polygonal, and elongated with the long axis in the direction of blood flow.

Answer 40

Vascular endothelial

Question 41

______ with its ______ is highly differentiated to mediate and actively monitor the bidirectional exchange of molecules by simple and active diffusion, receptor-mediated endocytosis, transcytosis, and other mechanisms.

Answer 41

Endothelium, basal lamina

Question 42

Besides their key role in metabolite exchanges between blood and tissues, endothelial cells have several other functions:

Answer 42

nonthrombogenic surface
vascular tone and blood flow
inflammation and local immune responses

Question 43

Besides their key role in metabolite exchanges between blood and tissues, endothelial cells have several other functions:

The endothelium presents a ______ on which blood will not clot and actively secretes agents that control local clot formation (such as ______, ______, and ______).

Answer 43

nonthrombogenic surface , heparin, tissue plasminogen activator, von Willebrand factor

Question 44

Besides their key role in metabolite exchanges between blood and tissues, endothelial cells have several other functions:

The cells regulate local ______ by secreting various factors that stimulate smooth muscle contraction (such as ______ and ______) or relaxation (including ______ and ______).

Answer 44

vascular tone and blood flow, endothelin-1, angiotensin- converting enzyme [ACE], nitric oxide [NO], prostacyclin

Question 45

Besides their key role in metabolite exchanges between blood and tissues, endothelial cells have several other functions:

Endothelium has several roles in ______. In venules endothelial cells induce specific white blood cells to stop and undergo ______ at sites of injury or infection.

Answer 45

inflammation and local immune responses, transendothelial migration

Question 46

TISSUES OF THE VASCULAR WALL

Under those conditions ______ is expressed rapidly on the luminal surface when unique elongated granules, called ______, fuse with the cell membrane.

Answer 46

P-selectin, Weibel–Palade bodies

Question 47

______ is the first step in the activation of white blood cells specifically where they are needed.

Answer 47

adhesion to selectins

Question 48

Endothelial cells also secrete various factors called ______ that affect the activity of local white blood cells during inflammation.

Answer 48

interleukins

Question 49

Under various conditions endothelial cells secrete various ______, including proteins promoting proliferation of specific white blood cell lineages and cells that make up the vascular wall.

Answer 49

growth factors

Question 50

Growth factors such as ______ stimulate formation of the vascular system from embryonic mesenchyme (______), help maintain the vasculature in adults, and promote capillary sprouting and outgrowth from small existing vessels (______) during normal growth, during tissue repair and regeneration, and in tumors and other pathological conditions.

Answer 50

vascular endothelial growth factor (VEGF), vasculogenesis, angiogenesis

Question 51

In both processes other growth factors, called ______, stimulate endohelial cells to recruit smooth muscle cells and fibroblasts to form the other tissues of the vascular wall.

Answer 51

angiopoietins

Question 52

The normal vascular endothelium is ______, allowing adhesion of no blood cells or platelets and preventing blood clot formation.

Answer 52

antithrombogenic

Question 53

When endothelial cells of the microvasculature are damaged by tissue injury, ______ is exposed in the ______ tissues and induces the aggregation of blood ______.

Answer 53

collagen, subendothelial, platelets

Question 54

These ______ release factors which initiate a cascade of events that produce fibrin from circulating plasma fibrinogen.

Answer 54

platelets

Question 55

An intravascular clot, or ______, with a fibrin framework quickly forms to stop blood loss from the damaged vessels.

Answer 55

thrombus

Question 56

From large thrombi, solid masses called ______ may detach and be carried by the blood to obstruct distant vessels.

Answer 56

emboli

Question 57

The integrity of the endothelial layer preventing contact between platelets and the subendothelial connective tissue is an important ______ mechanism.

Answer 57

antithrombogenic

Question 58

Individuals in the initial stages of medical conditions involving thrombus formation, such as myocardial infarct, stroke, or pulmonary embolism, are treated intravenously with ______, commonly abbreviated as ______.
This is a ______ that breaks down fibrin and quickly dissolves the clot.

Answer 58

tissue plasminogen activator, tPA, serine protease

Question 59

______ fibers occur in the walls of all vessels larger than capillaries and are arranged ______ in layers. In arterioles and small arteries, the smooth muscle cells are connected by many more ______ and permit ______ and ______ that are of key importance in regulating the overall blood pressure.

Answer 59

Smooth muscle, helically, gap junctions, vasoconstriction, vasodilation

Question 60

______ components are present in vascular walls in variable amounts and proportions based on local functional requirements.

Answer 60

Connective tissue

Question 61

______ are found in the subendothelial layer, between the smooth muscle layers, and in the outer covering.

Answer 61

Collagen fibers

Question 62

______ provide the resiliency required for the vascular wall to expand under pressure.

Answer 62

Elastic fibers

Question 63

______ is a major component in large arteries where it forms parallel lamellae, regularly distributed between the muscle layers.

Answer 63

Elastin

Question 64

Variations in the amount and composition of ground substance components such as ______ and ______ also contribute to the physical and metabolic properties of the wall in different vessels, especially affecting their ______.

Answer 64

proteoglycans, hyaluronate, permeability

Question 65

The walls of all blood vessels larger than the ______ have many components in common and similar organization.

Answer 65

microvasculature

Question 66

Branching of the vessels helps produce reductions in their ______ that are accompanied by gradual changes in the composition of the vascular wall. Transitions such as those from “______” to “______” are not clear-cut.

However, all of these larger vessels have walls with ______ concentric layers, or ______.

Answer 66

size, small arteries, arterioles, three, tunics

Question 67

However, all of these larger vessels have walls with three concentric layers, or tunics (L. tunica, coat):

The innermost tunica ______ consists of the endothelium and a thin subendothelial layer of loose connective tissue sometimes containing smooth muscle fibers.

Answer 67

intima

Question 68

In arteries the intima includes a thin layer, the ______, composed of ______, with holes allowing better diffusion of substances from blood deeper into the wall.

Answer 68

internal elastic lamina, elastin

Question 69

However, all of these larger vessels have walls with three concentric layers, or tunics (L. tunica, coat):

The tunica ______, the middle layer, consists chiefly of concentric layers of helically arranged smooth muscle cells.

Interposed among the muscle fibers are variable amounts of ______ and ______, ______, and ______, all of which are produced by the smooth muscle cells.

Answer 69

media, elastic fibers, elastic lamellae, reticular fibers, proteoglycans

Question 70

In arteries the media may also have an ______ separating it from the outermost tunic.

Answer 70

external elastic lamina

Question 71

However, all of these larger vessels have walls with three concentric layers, or tunics (L. tunica, coat):

The outer ______, or ______, is connective tissue consisting principally of type I collagen and elastic fibers.

Answer 71

adventitia, tunica externa

Question 72

The ______ is continuous with and bound to the stroma of the organ through which the blood vessel runs.

Answer 72

adventitia

Question 73

Just as the heart wall is supplied with its own ______ for nutrients and O2, large vessels usually have ______ (“______”): arterioles, capillaries, and venules in the adventitia and outer part of the media.

Answer 73

coronary vasculature, vasa vasorum, vessels of the vessel

Question 74

The ______ are required to provide metabolites to cells in those tunics in larger vessels because the wall is too thick to be nourished solely by diffusion from the blood in the lumen.

Answer 74

vasa vasorum

Question 75

______ alone does provide the needs of cells in the intima. Because they carry deoxygenated blood, large veins commonly have more ______ than arteries.

Answer 75

Luminal blood, vasa vasorum

Question 76

The adventitia of larger vessels also contains a network of ______ autonomic nerve fibers, the ______ nerves, which release the vasoconstrictor ______.

The density of this innervation is greater in ______ than in veins.

Answer 76

unmyelinated, vasomotor, norepinephrine, arteries

Question 77

______ are the aorta, the pulmonary artery, and their largest branches; these large vessels are also called ______ because their major role is to carry blood to smaller arteries.

Answer 77

Elastic arteries, conducting arteries

Question 78

the most prominent feature of elastic arteries is the thick ______ in which elastic lamellae alternate with layers of smooth muscle fibers. The adult aorta has about ______ elastic lamellae (more if the individual is ______).

Answer 78

tunica media, 50, hypertensive

Question 79

ELASTIC ARTERIES

The ______ is well developed, with many smooth muscle cells in the subendothelial connective tissue, and often shows folds in cross section as a result of the loss of blood pressure and contraction of the vessel at death.

Answer 79

tunica intima

Question 80

ELASTIC ARTERIES

Between the intima and the media is the ______, which is more well-defined than the elastic laminae of the media

Answer 80

internal elastic lamina

Question 81

ELASTIC ARTERIES

The ______ is much thinner than the media.

Answer 81

adventitia

Question 82

ELASTIC ARTERIES

The numerous elastic laminae of these arteries contribute to their important function of making the blood flow more ______.

Answer 82

uniform

Question 83

During ______ (______) blood is moved through the arteries forcefully and the elastin is stretched, distending the wall within the limit set by the wall’s collagen.

Answer 83

ventricular contraction, systole

Question 84

When the ventricles ______ (______) ventricular pressure drops to a low level, but the elastin rebounds passively, helping to maintain arterial pressure.

Answer 84

relax, diastole

Question 85

The ______ and ______ valves prevent backflow of blood into the heart, so the rebound continues the blood flow away from the heart.

Answer 85

aortic, pulmonary

Question 86

______ and ______ decrease and become less variable as the distance from the heart increases.

Answer 86

Arterial blood pressure, blood velocity

Question 87

______ are slight dilations of the bilateral internal carotid arteries where they branch from the (elastic) common carotid arteries; they act as important ______ monitoring arterial blood pressure.

At these sinuses the tunica media is ______, allowing greater distension when blood pressure rises, and the adventitia contains many sensory nerve endings from cranial nerve IX, the ______.

Answer 87

Carotid sinuses, baroreceptors, thinner, glossopharyngeal nerve

Question 88

The brain’s ______ process these afferent impulses and adjust vasoconstriction, maintaining normal blood pressure.

Functionally similar baroreceptors present in the aortic arch transmit signals pertaining to ______ via cranial nerve X, the ______.

Answer 88

vasomotor centers, blood pressure, vagus nerve

Question 89

Histologically more complex ______ which monitor blood CO2 and O2 levels, as well as its pH, are found in the ______ bodies and in the ______ bodies, located in the walls of the carotid sinuses and aortic arch, respectively.

These structures are parts of the autonomic nervous system called ______ with rich capillary networks.

Answer 89

chemoreceptors, carotid, aortic, paraganglia

Question 90

The capillaries are closely surrounded by large, neural crest-derived ______filled with dense-core vesicles containing dopamine, acetylcholine, and other neurotransmitters, which are supported by smaller satellite cells.

Answer 90

glomus cells

Question 91

Ion channels in the glomus cell membranes respond to stimuli in the arterial blood, primarily ______ (low O2), ______ (excess CO2), or ______, by activating release of neurotransmitters.

Answer 91

hypoxia, hypercapnia, acidosis

Question 92

Sensory fibers branching from the ______ nerve form synapses with the ______ cells and signal brain centers to initiate cardiovascular and respiratory adjustments that correct the condition.

Answer 92

glossopharyngeal, glomus

Question 93

The ______, also called ______, distribute blood to the organs and help regulate blood pressure by contracting or relaxing the smooth muscle in the media. The intima has a thin ______ and a prominent ______.

Answer 93

muscular arteries, distributing arteries, the subendothelial layer, internal elastic lamina

Question 94

The media may contain up to ______ layers of large smooth muscle cells interspersed with a variable number of elastic lamellae (depending on the size of the vessel).

Answer 94

40

Question 95

An external elastic lamina is present only in the larger muscular ______.

Answer 95

arteries

Question 96

The adventitial connective tissue contains ______, ______, and ______, all of which may penetrate to the outer part of the media.

Answer 96

lymphatic capillaries, vasa vasorum, nerves

Question 97

Muscular arteries branch repeatedly into smaller and smaller arteries, until reaching a size with ______ or ______ layers of medial smooth muscle.

Answer 97

three, four

Question 98

The smallest arteries branch as ______, which have only one or two smooth muscle layers; these indicate the beginning of an organ’s ______ where exchanges between blood and tissue fluid occur.

Answer 98

arterioles, microvasculature

Question 99

Arterioles are generally less than ______ in diameter, with lumens approximately as wide as the wall is thick.

Answer 99

0.1 mm

Question 100

The ______ is very thin, elastic laminae are absent, and the media consists of the circularly arranged smooth muscle cells. In both small arteries and arterioles the ______ is very thin and inconspicuous.

Answer 100

subendothelial layer, adventitia

Question 101

______ almost always branch to form anastomosing networks of capillaries that surround the ______ cells of the organ.

Answer 101

Arterioles, parenchymal

Question 102

At the ends of arterioles the smooth muscle fibers act as ______ and produce periodic ______ into capillaries

Answer 102

sphincters, blood flow

Question 103

______ normally keeps arterioles partially closed, resisting blood flow, which makes these vessels the major determinants of systemic blood pressure.

Answer 103

Muscle tone

Question 104

In certain tissues and organs, arterioles ______ from this simple path to accommodate various specialized functions.

For example, ______ by the skin involves arterioles that can bypass capillary networks and connect directly to ______.

Answer 104

deviate, thermoregulation, venules

Question 105

The media and adventitia are thicker n these ______ (or ______) and richly innervated by sympathetic and parasympathetic nerve fibers.

Answer 105

arteriovenous shunts, arteriovenous anastomoses

Question 106

The autonomic fibers control the degree of ______ at the shunts, regulating blood flow through the capillary beds.

Answer 106

vasoconstriction

Question 107

High capillary blood flow in the skin allows more ______ from the body, while reduced capillary blood flow ______—important functions when the environmental temperature is hot or cold, respectively.

Answer 107

heat dissipation, conserves heat

Question 108

Another important alternative microvascular pathway is a ______, in which blood flows through two successive capillary beds separated by a ______.

This arrangement allows for hormones or nutrients picked up by the blood in the first capillary network to be delivered most efficiently to cells around the second capillary bed before the blood is returned to the heart for general distribution.

Answer 108

venous portal system, portal vein

Question 109

venous portal system

The best examples are the ______ of the liver and the hypothalamic- ______ in the anterior pituitary gland, both of which have major physiologic importance.

Answer 109

hepatic portal system, hypophyseal portal system

Question 110

______ permit and regulate metabolic exchange between blood and surrounding tissues.

These smallest blood vessels always function in networks called ______, whose size and overall shape conforms to that of the structure supplied.

Answer 110

Capillaries, capillary beds

Question 111

The density of the capillary bed is related to the ______ of the tissues.

Answer 111

metabolic activity

Question 112

Tissues with high metabolic rates, such as the kidney, liver, and cardiac and skeletal muscle, have abundant ______; the opposite is true of tissues with low metabolic rates, such as ______ and ______.

Answer 112

capillaries, smooth muscle, dense connective tissue

Question 113

Capillary beds are supplied preferentially by one or more terminal arteriole branches called ______, which are continuous with ______ connected with the ______.

Answer 113

metarterioles, thoroughfare channels, postcapillary venules

Question 114

Capillaries branch from the ______, which are encircled by scattered ______ cells, and converge into the thoroughfare channels, which lack muscle.

Answer 114

metarterioles, smooth muscle

Question 115

The metarteriole muscle cells act as ______ that control blood flow into the capillaries.

These sphincters contract and relax cyclically, with ______-______ cycles per minute, causing blood to pass through capillaries in a pulsatile manner.

Answer 115

precapillary sphincters, 5, 10

Question 116

When the sphincters are closed, blood flows directly from the metarterioles and thoroughfare channels into ______.

Answer 116

postcapillary venules

Question 117

Capillaries are composed of the simple layer of ______ rolled up as a tube surrounded by ______.

Answer 117

endothelial cells, basement membrane

Question 118

The average diameter of capillaries varies from ______, which allows transit of blood cells only one at a time, and their individual length is usually not more than ______.

These minute vessels make up over ______% of the body’s vasculature, with a total length of more than ______ and a total surface area of approximately ______.

Answer 118

4 to 10 μm, 50 μm, 90, 100,000 km, 5000 m2

Question 119

Because of the cyclical opening and closing of the sphincters, most capillaries are essentially empty at any given time, with only about ______% (~______ mL in an adult) of the total blood volume moving through these structures.

Their thin walls, extensive surface area, and slow, pulsatile blood flow optimize capillaries for the exchange of water and solutes between blood and tissues.

Answer 119

5, 300

Question 120

In addition to the endothelial properties mentioned earlier in this chapter, capillary cells have many features specialized for molecular transfer by mechanisms ranging from ______ to ______.

Answer 120

simple diffusion, transcytosis

Question 121

The average thickness of the cells is only ______ and their nuclei are often distinctively curved to accommodate the very small tubular structure.

Answer 121

0.25 μm

Question 122

The ______ contains mitochondria and other organelles, as well as a large population of membranous vesicles typically. Along with the basal lamina, ______ between the cells maintain the tubular structure, with variable numbers of ______ having an important role in capillary permeability.

Answer 122

cytoplasm, junctional complexes, tight junctions

Question 123

Major structural variations in capillaries occur in organs with various functions that permit very different levels of ______. Capillaries are generally grouped into ______ histologic types, depending on the continuity of the ______ cells and their ______.

Answer 123

metabolic exchange, three, endothelial, basement membrane

Question 124

Capillaries are generally grouped into three histologic types, depending on the continuity of the endothelial cells and their basement membrane:

______ have many tight, well-developed occluding junctions between slightly overlapping endothelial cells, which provide for continuity along the endothelium and well-regulated metabolic exchange across the cells.

Answer 124

Continuous capillaries

Question 125

Capillaries are generally grouped into three histologic types, depending on the continuity of the endothelial cells and their basement membrane:

______
- This is the most common type of capillary and is found in muscle, connective tissue, lungs, exocrine glands, and nervous tissue.

Answer 125

Continuous capillaries

Question 126

Capillaries are generally grouped into three histologic types, depending on the continuity of the endothelial cells and their basement membrane:

Continuous capillaries
- Ultrastructural studies show numerous vesicles indicating ______ of macromolecules in both directions across the endothelial cell cytoplasm.

Answer 126

transcytosis

Question 127

Capillaries are generally grouped into three histologic types, depending on the continuity of the endothelial cells and their basement membrane:

______ have a sieve- like structure that allows more extensive molecular exchange across the endothelium.

Answer 127

Fenestrated capillaries

Question 128

Capillaries are generally grouped into three histologic types, depending on the continuity of the endothelial cells and their basement membrane:

Fenestrated capillaries
- The endothelial cells are penetrated by numerous small circular openings or fenestrations (L. fenestra, perforation), approximately ______ in diameter.

Answer 128

80 nm

Question 129

Capillaries are generally grouped into three histologic types, depending on the continuity of the endothelial cells and their basement membrane:

Fenestrated capillaries
- Some fenestrations are covered by very thin diaphragms of ______; others may represent membrane invaginations during ______ that temporarily involve both sides of the very thin cells.

Answer 129

proteoglycans, transcytosis

Question 130

Capillaries are generally grouped into three histologic types, depending on the continuity of the endothelial cells and their basement membrane:

Fenestrated capillaries
- The basement membrane however is ______ and covers the ______. Fenestrated capillaries are found in organs with rapid interchange of substances between tissues and the blood, such as the kidneys, intestine, choroid plexus, and endocrine glands.

Answer 130

continuous, fenestrations

Question 131

Capillaries are generally grouped into three histologic types, depending on the continuity of the endothelial cells and their basement membrane:

______, commonly called ______, permit maximal exchange of macromolecules as well as allow easier movement of cells between tissues and blood.

Answer 131

Discontinuous capillaries, sinusoids

Question 132

Capillaries are generally grouped into three histologic types, depending on the continuity of the endothelial cells and their basement membrane:

Discontinuous capillaries
- The endothelium here has large ______ without ______ and irregular ______, forming a discontinuous layer with spaces between and through the cells.

Answer 132

perforations, diaphragms, intercellular clefts

Question 133

Capillaries are generally grouped into three histologic types, depending on the continuity of the endothelial cells and their basement membrane:

Discontinuous capillaries
- Unlike other capillaries sinusoids also have highly discontinuous ______ and much larger diameters, often ______, which slows blood flow.

Answer 133

basement membranes, 30-40 μm

Question 134

Capillaries are generally grouped into three histologic types, depending on the continuity of the endothelial cells and their basement membrane:

Discontinuous capillaries
- Sinusoidal capillaries of this type are found in the ______, ______, some ______, and ______

Answer 134

liver, spleen, endocrine organs, bone marrow

Question 135

At various locations along continuous capillaries and postcapillary venules are mesenchymal cells called ______, with long cytoplasmic processes partly surrounding the endothelial layer.

Answer 135

pericytes

Question 136

Pericytes secrete many ______ components and form their own ______, which fuses with the basement membrane of the endothelial cells.

Answer 136

ECM, basal lamina

Question 137

Well-developed cytoskeletal networks of ______, ______, and ______ indicate that pericytes also dilate or constrict capillaries, helping to regulate blood flow in some organs.

Answer 137

myosin, actin, tropomyosin

Question 138

Within the CNS pericytes are important for maintaining the endothelial ______.

Answer 138

blood-brain barrier

Question 139

After injuries, ______ proliferate and differentiate to form smooth muscle and other cells in new vessels as the ______ is reestablished.

Answer 139

pericytes, microvasculature

Question 140

In many organs the pericyte population also includes ______ cells important for regeneration of other tissues.

Answer 140

mesenchymal stem

Question 141

The transition from capillaries to venules occurs ______.

Answer 141

gradually

Question 142

______ are similar to capillaries with pericytes but larger, ranging in diameter from ______.

Answer 142

Postcapillary venules, 15 to 20 μm

Question 143

______ are the primary site at which white blood cells adhere to endothelium and leave the circulation at sites of infection or tissue damage.

Answer 143

postcapillary venules

Question 144

Postcapillary venules converge into larger ______ that have more distinct contractile cells.

Answer 144

collecting venules

Question 145

With increasing size venules become surrounded by a recognizable tunica media with two or three smooth muscle layers and are called ______.

Answer 145

muscular venules

Question 146

A characteristic feature of all venules is the large diameter of the ______ compared to the overall thinness of the wall.

Answer 146

lumen

Question 147

______ carry blood back to the heart from microvasculature all over the body.

Answer 147

Veins

Question 148

Blood entering veins is under very ______ and moves toward the heart by ______ of the smooth muscle fibers in the media and by external ______ from surrounding skeletal muscles and other organs.

Answer 148

low pressure, contraction, compressions

Question 149

Most veins are classified as ______ or ______ veins, with diameters of ______ or less.

These veins are usually located close and parallel to corresponding muscular ______.

Answer 149

small, medium, 10 mm, arteries

Question 150

VEINS

The ______ is usually thin, the ______ has small bundles of smooth muscle cells mixed with a network of reticular fibers and delicate elastic fibers, and the collagenous ______ layer is thick and well developed.

Answer 150

tunica intima, media, adventitial

Question 151

The big venous trunks, paired with elastic arteries close to the heart, are the ______.

Answer 151

large veins

Question 152

large veins
- These have well-developed ______ layers, but relatively thin ______ with alternating smooth muscle and connective tissue.

Answer 152

intimal, media

Question 153

The tunica ______ is thicker than the media in large veins and frequently contains longitudinal bundles of smooth muscle.

Answer 153

adventitia

Question 154

large veins
- Both the media and adventitia contain ______, and an ______ like those of arteries may be present.

Answer 154

elastic fibers, internal elastic lamina

Question 155

An important feature of large and medium veins are ______, which consist of thin, paired folds of the tunica intima projecting across the lumen, rich in elastic fibers and covered on both sides by endothelium.

Answer 155

valves

Question 156

The ______, which are especially numerous in veins of the legs, help keep the flow of venous blood directed toward the heart.

Answer 156

valves

Question 157

In addition to the blood vasculature, the body has a system of very thin-walled channels, the ______, which collect excess interstitial fluid from the tissue spaces as lymph and return it to the blood.

Answer 157

lymphatic capillaries

Question 158

Like the interstitial fluid, ______ is usually rich in lightly staining proteins but does not normally contain ______, although ______ and other ______ may normally be present.

Answer 158

lymph, red blood cells, lymphocytes, white blood cells

Question 159

With exceptions such as the bone marrow and most of the CNS, most tissues with blood microvasculature also contain ______ (or ______).

Answer 159

lymphatic capillaries, lymphatics

Question 160

______ originate locally as tubes of very thin endothelial cells which lack tight junctions and rest on a discontinuous basal lamina.

Answer 160

Lymphatic capillaries

Question 161

Fine anchoring filaments of ______ extend from the basal lamina to the surrounding connective tissue, preventing collapse of the vessels. ______ enters lymphatic capillaries by flowing between endothelial cells and by ______.

Answer 161

collagen, Interstitial fluid, transcytosis

Question 162

Specific domains of adjacent endothelial cells also lack ______ connections to the basal lamina and extend into the ______ to form leaflets of valves facilitating fluid entry and preventing most backflow of lymph.

Answer 162

hemidesmosome, lumen

Question 163

Lymphatic capillaries converge into larger ______ with thin walls and increasing amounts of connective tissue and smooth muscle which never form clearly distinct outer tunics.

Answer 163

lymphatic vessels

Question 164

Like veins lymphatic vessels have valves comprised of complete ______ folds. Interposed in the path of these larger lymphatic vessels are ______, where lymph is processed by cells of the immune system .

Answer 164

intimal, lymph nodes

Question 165

In histological sections lymphatic vessels are often dilated with ______.

Answer 165

lymph

Question 166

As in veins, ______ is aided by external forces (eg, contraction of surrounding skeletal muscle) with the valves keeping lymph flow ______.

Answer 166

lymphatic circulation, unidirectional

Question 167

Lymphatic vessels ultimately converge as two large trunks: the ______ and the ______, which empty lymph back into the blood.

Answer 167

thoracic duct, right lymphatic duct

Question 168

The ______ connects with the blood circulatory system near the junction of the left internal jugular vein with the left subclavian vein, whereas the ______ enters near the confluence of the right subclavian vein and the right internal jugular vein.

Answer 168

thoracic duct, right lymphatic duct

Question 169

The structure of these largest lymphatic vessels is similar to that of ______.
The ______ is relatively underdeveloped, but contains ______ and a ______.

Answer 169

small veins, adventitia, vasa vasorum, neural network

Question 170

Besides gathering interstitial fluid as lymph and returning it to the blood, the ______ is a major distributor of lymphocytes, antibodies, and other immune components that are carried through many organs to and from lymph nodes and other lymphoid tissues.

Answer 170

lymphatic vascular system