THE CIRCULATORY SYSTEM Flashcards
1
Q
The blood vascular system, or cardiovascular system, consists of the following structures:
A
heart
Arteries
Capillaries
Veins
2
Q
The blood vascular system, or cardiovascular system, consists of the following structures:
The ______ propels blood through the system.
A
heart
3
Q
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.
A
Arteries
4
Q
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.
A
Capillaries
5
Q
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.
A
Veins
6
Q
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 ______.
A
microvasculature, microvascular bed
7
Q
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.
A
pulmonary circulation, systemic circulation
8
Q
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.
A
lymphatic capillaries
9
Q
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.
A
largest lymph vessels
10
Q
The internal surface of all components of the blood and lymphatic systems is lined by a ______ called ______.
A
simple squamous epithelium, endothelium
11
Q
As the interface between blood and the organs, ______ cells have crucial physiologic and medical importance
A
cardiovascular endothelial
12
Q
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.
A
endothelial cells
13
Q
______ in the four chambers of the heart wall contracts rhythmically, pumping the blood through the circulatory system.
A
Cardiac muscle
14
Q
The right and left ______ propel blood to the pulmonary and systemic circulations.
A
ventricles
15
Q
right and left ______ receive blood from the body and the pulmonary veins, respectively.
A
atria
16
Q
The walls of all four heart chambers consist of three major layers: the ______, the ______, and the ______.
A
internal endocardium, middle myocardium, external epicardium
17
Q
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.
A
endocardium, subendocardial layer
18
Q
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.
A
myocardium
19
Q
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.
A
ventricles, left
20
Q
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.
A
epicardium, simple squamous mesothelium
21
Q
The epicardium corresponds to the ______ of the ______, the membrane surrounding the heart.
A
visceral layer, pericardium
22
Q
Where the large vessels enter and leave the heart, the epicardium is reflected back as the ______ lining the pericardium.
A
parietal layer
23
Q
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.
A
adipose, epicardium, pericardium, serous mesothelial
24
Q
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.
A
dense irregular connective, cardiac skeleton, interventricular, interatrial, valve cusps, chordae tendineae
25
Various regions of the cardiac skeleton have the following functions:
• 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.
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.
cardiac muscle, conducting system of the heart
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.
sinoatrial (SA) node, pacemaker, atrioventricular (AV) node, AV bundle, His
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.
6- to 7-mm3, atria
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.
AV node, depolarization myocytes
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 ______.
AV bundle, interventricular septum, myocytes, Purkinje fibers
31
______
- These are pale-staining fibers, larger than the adjacent contractile fibers, with sparse, peripheral myofibrils, and much glycogen.
Purkinje fibers
32
______ mingle distally with contractile muscle fibers of each ventricle and trigger waves of contraction through both ventricles simultaneously.
Purkinje fibers
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.
parasympathetic, sympathetic, Ganglionic
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.
parasympathetic, vagus, sympathetic, afferent, angina pectoris
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 ______.
heart murmur
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.
blood
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.
surgically, artificial valve, animal donor, endothelial, exogenous anticoagulant
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.
smooth muscle, connective tissue, mechanical, metabolic
39
The ______ is a specialized epithelium that acts as a semipermeable barrier between two major internal compartments: the ______ and the ______.
endothelium, blood, interstitial tissue fluid
40
______ cells are squamous, polygonal, and elongated with the long axis in the direction of blood flow.
Vascular endothelial
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.
Endothelium, basal lamina
42
Besides their key role in metabolite exchanges between blood and tissues, endothelial cells have several other functions:
nonthrombogenic surface
vascular tone and blood flow
inflammation and local immune responses
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 ______).
nonthrombogenic surface , heparin, tissue plasminogen activator, von Willebrand factor
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 ______).
vascular tone and blood flow, endothelin-1, angiotensin- converting enzyme [ACE], nitric oxide [NO], prostacyclin
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.
inflammation and local immune responses, transendothelial migration
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.
P-selectin, Weibel–Palade bodies
47
______ is the first step in the activation of white blood cells specifically where they are needed.
adhesion to selectins
48
Endothelial cells also secrete various factors called ______ that affect the activity of local white blood cells during inflammation.
interleukins
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.
growth factors
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.
vascular endothelial growth factor (VEGF), vasculogenesis, angiogenesis
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.
angiopoietins
52
The normal vascular endothelium is ______, allowing adhesion of no blood cells or platelets and preventing blood clot formation.
antithrombogenic
53
When endothelial cells of the microvasculature are damaged by tissue injury, ______ is exposed in the ______ tissues and induces the aggregation of blood ______.
collagen, subendothelial, platelets
54
These ______ release factors which initiate a cascade of events that produce fibrin from circulating plasma fibrinogen.
platelets
55
An intravascular clot, or ______, with a fibrin framework quickly forms to stop blood loss from the damaged vessels.
thrombus
56
From large thrombi, solid masses called ______ may detach and be carried by the blood to obstruct distant vessels.
emboli
57
The integrity of the endothelial layer preventing contact between platelets and the subendothelial connective tissue is an important ______ mechanism.
antithrombogenic
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.
tissue plasminogen activator, tPA, serine protease
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.
Smooth muscle, helically, gap junctions, vasoconstriction, vasodilation
60
______ components are present in vascular walls in variable amounts and proportions based on local functional requirements.
Connective tissue
61
______ are found in the subendothelial layer, between the smooth muscle layers, and in the outer covering.
Collagen fibers
62
______ provide the resiliency required for the vascular wall to expand under pressure.
Elastic fibers
63
______ is a major component in large arteries where it forms parallel lamellae, regularly distributed between the muscle layers.
Elastin
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 ______.
proteoglycans, hyaluronate, permeability
65
The walls of all blood vessels larger than the ______ have many components in common and similar organization.
microvasculature
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 ______.
size, small arteries, arterioles, three, tunics
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.
intima
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.
internal elastic lamina, elastin
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.
media, elastic fibers, elastic lamellae, reticular fibers, proteoglycans
70
In arteries the media may also have an ______ separating it from the outermost tunic.
external elastic lamina
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.
adventitia, tunica externa
72
The ______ is continuous with and bound to the stroma of the organ through which the blood vessel runs.
adventitia
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.
coronary vasculature, vasa vasorum, vessels of the vessel
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.
vasa vasorum
75
______ alone does provide the needs of cells in the intima. Because they carry deoxygenated blood, large veins commonly have more ______ than arteries.
Luminal blood, vasa vasorum
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.
unmyelinated, vasomotor, norepinephrine, arteries
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.
Elastic arteries, conducting arteries
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 ______).
tunica media, 50, hypertensive
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.
tunica intima
80
ELASTIC ARTERIES
Between the intima and the media is the ______, which is more well-defined than the elastic laminae of the media
internal elastic lamina
81
ELASTIC ARTERIES
The ______ is much thinner than the media.
adventitia
82
ELASTIC ARTERIES
The numerous elastic laminae of these arteries contribute to their important function of making the blood flow more ______.
uniform
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.
ventricular contraction, systole
84
When the ventricles ______ (______) ventricular pressure drops to a low level, but the elastin rebounds passively, helping to maintain arterial pressure.
relax, diastole
85
The ______ and ______ valves prevent backflow of blood into the heart, so the rebound continues the blood flow away from the heart.
aortic, pulmonary
86
______ and ______ decrease and become less variable as the distance from the heart increases.
Arterial blood pressure, blood velocity
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 ______.
Carotid sinuses, baroreceptors, thinner, glossopharyngeal nerve
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 ______.
vasomotor centers, blood pressure, vagus nerve
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.
chemoreceptors, carotid, aortic, paraganglia
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.
glomus cells
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.
hypoxia, hypercapnia, acidosis
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.
glossopharyngeal, glomus
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 ______.
muscular arteries, distributing arteries, the subendothelial layer, internal elastic lamina
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).
40
95
An external elastic lamina is present only in the larger muscular ______.
arteries
96
The adventitial connective tissue contains ______, ______, and ______, all of which may penetrate to the outer part of the media.
lymphatic capillaries, vasa vasorum, nerves
97
Muscular arteries branch repeatedly into smaller and smaller arteries, until reaching a size with ______ or ______ layers of medial smooth muscle.
three, four
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.
arterioles, microvasculature
99
Arterioles are generally less than ______ in diameter, with lumens approximately as wide as the wall is thick.
0.1 mm
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.
subendothelial layer, adventitia
101
______ almost always branch to form anastomosing networks of capillaries that surround the ______ cells of the organ.
Arterioles, parenchymal
102
At the ends of arterioles the smooth muscle fibers act as ______ and produce periodic ______ into capillaries
sphincters, blood flow
103
______ normally keeps arterioles partially closed, resisting blood flow, which makes these vessels the major determinants of systemic blood pressure.
Muscle tone
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 ______.
deviate, thermoregulation, venules
105
The media and adventitia are thicker n these ______ (or ______) and richly innervated by sympathetic and parasympathetic nerve fibers.
arteriovenous shunts, arteriovenous anastomoses
106
The autonomic fibers control the degree of ______ at the shunts, regulating blood flow through the capillary beds.
vasoconstriction
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.
heat dissipation, conserves heat
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.
venous portal system, portal vein
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.
hepatic portal system, hypophyseal portal system
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.
Capillaries, capillary beds
111
The density of the capillary bed is related to the ______ of the tissues.
metabolic activity
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 ______.
capillaries, smooth muscle, dense connective tissue
113
Capillary beds are supplied preferentially by one or more terminal arteriole branches called ______, which are continuous with ______ connected with the ______.
metarterioles, thoroughfare channels, postcapillary venules
114
Capillaries branch from the ______, which are encircled by scattered ______ cells, and converge into the thoroughfare channels, which lack muscle.
metarterioles, smooth muscle
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.
precapillary sphincters, 5, 10
116
When the sphincters are closed, blood flows directly from the metarterioles and thoroughfare channels into ______.
postcapillary venules
117
Capillaries are composed of the simple layer of ______ rolled up as a tube surrounded by ______.
endothelial cells, basement membrane
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 ______.
4 to 10 μm, 50 μm, 90, 100,000 km, 5000 m2
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.
5, 300
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 ______.
simple diffusion, transcytosis
121
The average thickness of the cells is only ______ and their nuclei are often distinctively curved to accommodate the very small tubular structure.
0.25 μm
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.
cytoplasm, junctional complexes, tight junctions
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 ______.
metabolic exchange, three, endothelial, basement membrane
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.
Continuous capillaries
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.
Continuous capillaries
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.
transcytosis
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.
Fenestrated capillaries
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.
80 nm
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.
proteoglycans, transcytosis
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.
continuous, fenestrations
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.
Discontinuous capillaries, sinusoids
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.
perforations, diaphragms, intercellular clefts
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.
basement membranes, 30-40 μm
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 ______
liver, spleen, endocrine organs, bone marrow
135
At various locations along continuous capillaries and postcapillary venules are mesenchymal cells called ______, with long cytoplasmic processes partly surrounding the endothelial layer.
pericytes
136
Pericytes secrete many ______ components and form their own ______, which fuses with the basement membrane of the endothelial cells.
ECM, basal lamina
137
Well-developed cytoskeletal networks of ______, ______, and ______ indicate that pericytes also dilate or constrict capillaries, helping to regulate blood flow in some organs.
myosin, actin, tropomyosin
138
Within the CNS pericytes are important for maintaining the endothelial ______.
blood-brain barrier
139
After injuries, ______ proliferate and differentiate to form smooth muscle and other cells in new vessels as the ______ is reestablished.
pericytes, microvasculature
140
In many organs the pericyte population also includes ______ cells important for regeneration of other tissues.
mesenchymal stem
141
The transition from capillaries to venules occurs ______.
gradually
142
______ are similar to capillaries with pericytes but larger, ranging in diameter from ______.
Postcapillary venules, 15 to 20 μm
143
______ are the primary site at which white blood cells adhere to endothelium and leave the circulation at sites of infection or tissue damage.
postcapillary venules
144
Postcapillary venules converge into larger ______ that have more distinct contractile cells.
collecting venules
145
With increasing size venules become surrounded by a recognizable tunica media with two or three smooth muscle layers and are called ______.
muscular venules
146
A characteristic feature of all venules is the large diameter of the ______ compared to the overall thinness of the wall.
lumen
147
______ carry blood back to the heart from microvasculature all over the body.
Veins
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.
low pressure, contraction, compressions
149
Most veins are classified as ______ or ______ veins, with diameters of ______ or less.
These veins are usually located close and parallel to corresponding muscular ______.
small, medium, 10 mm, arteries
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.
tunica intima, media, adventitial
151
The big venous trunks, paired with elastic arteries close to the heart, are the ______.
large veins
152
large veins
- These have well-developed ______ layers, but relatively thin ______ with alternating smooth muscle and connective tissue.
intimal, media
153
The tunica ______ is thicker than the media in large veins and frequently contains longitudinal bundles of smooth muscle.
adventitia
154
large veins
- Both the media and adventitia contain ______, and an ______ like those of arteries may be present.
elastic fibers, internal elastic lamina
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.
valves
156
The ______, which are especially numerous in veins of the legs, help keep the flow of venous blood directed toward the heart.
valves
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.
lymphatic capillaries
158
Like the interstitial fluid, ______ is usually rich in lightly staining proteins but does not normally contain ______, although ______ and other ______ may normally be present.
lymph, red blood cells, lymphocytes, white blood cells
159
With exceptions such as the bone marrow and most of the CNS, most tissues with blood microvasculature also contain ______ (or ______).
lymphatic capillaries, lymphatics
160
______ originate locally as tubes of very thin endothelial cells which lack tight junctions and rest on a discontinuous basal lamina.
Lymphatic capillaries
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 ______.
collagen, Interstitial fluid, transcytosis
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.
hemidesmosome, lumen
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.
lymphatic vessels
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 .
intimal, lymph nodes
165
In histological sections lymphatic vessels are often dilated with ______.
lymph
166
As in veins, ______ is aided by external forces (eg, contraction of surrounding skeletal muscle) with the valves keeping lymph flow ______.
lymphatic circulation, unidirectional
167
Lymphatic vessels ultimately converge as two large trunks: the ______ and the ______, which empty lymph back into the blood.
thoracic duct, right lymphatic duct
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.
thoracic duct, right lymphatic duct
169
The structure of these largest lymphatic vessels is similar to that of ______.
The ______ is relatively underdeveloped, but contains ______ and a ______.
small veins, adventitia, vasa vasorum, neural network
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.
lymphatic vascular system
