Blood Vessels Flashcards
1
Q
How do arteries change as they move away from the heart?
A
They branch, diverge, and get smaller.
2
Q
What is the function of arteries?
A
To carry blood away from the heart to tissues.
3
Q
What type of blood do systemic arteries carry?
A
Oxygenated blood.
4
Q
What type of blood do pulmonary arteries carry?
A
Oxygen-poor blood.
5
Q
How do veins change as they move toward the heart?
A
They join, merge, and get larger.
6
Q
What is the function of veins?
A
To return blood to the heart.
7
Q
How long is the total length of blood vessels in an adult human?
A
About 60,000 miles.
8
Q
What are the three layers of blood vessel walls?
A
Tunica intima, tunica media, and tunica externa.
9
Q
What is the function of the tunica intima?
A
It minimizes friction, promotes laminar flow, and reduces clot risk.
10
Q
What type of tissue forms the tunica intima?
A
Simple squamous epithelium overlying areolar tissue (endothelium).
11
Q
Why is the endothelium continuous with the endocardium?
A
To maintain smooth blood flow from the heart into vessels.
12
Q
What is the function of the tunica media?
A
It allows blood vessels to constrict or relax.
13
Q
What type of muscle is in the tunica media?
A
Circularly arranged smooth muscle.
14
Q
How does the tunica media differ in arteries and veins?
A
It is thicker in arteries but still present in veins, allowing them to constrict and relax.
15
Q
Which nervous system innervates the tunica media?
A
The sympathetic nervous system (no parasympathetic innervation).
16
Q
What happens when the tunica media is stimulated?
A
Vasoconstriction (muscle contracts, lumen diameter decreases).
17
Q
What happens when sympathetic stimulation is removed?
A
Vasodilation (muscle relaxes, lumen diameter increases).
18
Q
What is the function of arteries?
A
To carry blood away from the heart, usually oxygenated.
19
Q
Why do arteries have a thicker tunica media than veins?
A
They are more muscular to withstand surges of blood pressure.
20
Q
How do arteries appear in cross-section?
A
Round, unlike veins which appear misshapen.
21
Q
Where are elastic arteries located?
A
Near the heart, including the aorta and its major branches.
22
Q
What is the size range of elastic arteries?
A
2.5 cm to 1 cm in diameter.
23
Q
Why are elastic arteries called ‘conducting’ arteries?
A
They transport blood to smaller arteries, similar to how bronchi conduct air to the lungs.
24
Q
Why do elastic arteries have a large lumen?
A
To reduce resistance, making it easier for the heart to pump blood into them.
25
Are elastic arteries active in vasoconstriction?
No, smaller arteries regulate vascular resistance.
26
Which tunic contains the most elastin in elastic arteries?
The tunica media.
27
What is the function of elastin in elastic arteries?
It allows expansion and recoil to dampen pressure surges.
28
Why are elastic arteries considered pressure reservoirs?
They store kinetic energy during systole and release it during diastole to maintain blood flow.
29
How do elastic arteries propel blood forward during diastole?
By recoiling after expansion, keeping blood moving even when the heart is relaxed.
30
What is the function of muscular arteries?
To supply specific organs or groups of organs.
31
Why are muscular arteries also called 'distributing' arteries?
They distribute blood to different body regions.
32
What are examples of muscular arteries?
The celiac artery and renal arteries.
33
What is the size range of muscular arteries?
From the size of a little finger to a pencil lead.
34
Why are muscular arteries called 'muscular'?
Their tunica media is thicker relative to their lumen than in any other vessel type.
35
How do muscular arteries differ from elastic arteries in vasoconstriction?
They are more active in vasoconstriction, regulating blood flow to organs.
36
What are arterioles?
The smallest arteries.
37
What is the structure of the smallest arterioles?
A single layer of smooth muscle cells around the endothelium, retaining the tunica media.
38
What affects blood flow into capillary beds?
Arteriole diameter.
39
What happens when arterioles constrict?
Tissues served by them are largely bypassed.
40
What happens when arterioles dilate?
Blood flow to the capillary bed and tissues increases greatly.
41
How is arteriole diameter regulated? (3 mechanisms)
Hormonally, neurally, and by local chemical influences (e.g., metabolic byproducts).
42
What is the function of capillaries? (delivered products)
Gas, nutrient, hormone, and metabolic waste exchange.
43
What are the size characteristics of capillaries?
About 1 mm in length and 8–10 μm in diameter.
44
How do red blood cells pass through capillaries?
Single file due to their small diameter.
45
What layers do capillaries have?
Only the tunica intima (a single layer of endothelium with a basement membrane).
46
What are pericytes, and what is their function?
Smooth muscle-like cells that stabilize capillary walls and control permeability.
47
Where are capillaries scarce?
Tendons and ligaments (low vascular areas).
48
Where are capillaries absent?
Cartilage and epithelia (they receive nutrients from nearby connective tissue).
49
How do the cornea and lens receive nutrients without capillaries?
From the aqueous humor.
50
Why are capillaries ideal for material exchange?
Their thin walls allow efficient exchange of gases, nutrients, and waste between blood and extracellular fluid.
51
Where are continuous capillaries most abundant?
In the skin and muscles.
52
How do continuous capillaries compare to other capillaries in permeability?
They are the least permeable but still allow some exchange.
53
How are endothelial cells in continuous capillaries connected?
By tight junctions.
54
What are intercellular clefts?
Small gaps between endothelial cells that allow small molecules to pass.
55
How do brain capillaries differ from other continuous capillaries?
Their tight junctions are complete, forming the blood-brain barrier (BBB) with no intercellular clefts.
56
What makes fenestrated capillaries more permeable?
They have pores called fenestrations in the endothelial cells.
57
Where are fenestrated capillaries found?
In areas of absorption and filtrate formation: small intestine, endocrine organs, glomerulus (kidneys).
58
What are sinusoid capillaries?
Highly modified, leaky capillaries with large pores.
59
Where are sinusoid capillaries found?
In the liver, bone marrow, and spleen.
60
What structural features make sinusoids highly permeable?
Large irregular lumens, fenestrations, fewer tight junctions, and large intercellular clefts.
61
What can pass through sinusoid capillaries?
Large molecules and blood cells.
62
Why does blood flow sluggishly in sinusoids?
To allow time for modification and exchange.
63
What are capillary beds?
Networks of branching capillaries.
64
What vessel feeds a capillary bed?
A metarteriole.
65
What is a metarteriole?
A vessel structurally intermediate between an arteriole and a capillary.
66
What does a metarteriole continue as?
A thoroughfare channel that connects to a venule.
67
What structure regulates blood flow into capillary beds?
Precapillary sphincters.
68
Where are precapillary sphincters located?
At the root of each true capillary.
69
What happens when precapillary sphincters are open?
Blood floods the entire capillary bed.
70
What happens when precapillary sphincters are closed?
Blood bypasses true capillaries and flows directly into venules.
71
What is the purpose of capillary permeability?
To allow the delivery of substances and removal of waste.
72
How do O₂, CO₂, nutrients, and metabolic wastes cross capillary walls?
By diffusion.
73
What are the three basic routes of capillary permeability?
Lipid-soluble diffusion, small water-soluble transport, and active transport.
74
How do lipid-soluble molecules cross capillary walls?
By direct diffusion through endothelial cell membranes.
75
How do small water-soluble solutes (e.g., amino acids, sugars) pass through capillaries?
Via intercellular clefts or fenestrations.
76
How do large molecules (e.g., proteins) cross capillary walls?
By active transport in pinocytotic vesicles.
77
What are the four main transport mechanisms in capillaries? (each individual route to enter)
Diffusion, movement through clefts, movement through fenestrations, and vesicular transport.
78
How do lipid-soluble substances cross capillary walls?
By diffusion directly through the lipid bilayer (e.g., thyroid hormone).
79
How do water-soluble substances pass through capillaries?
By moving through intercellular clefts.
80
How do larger water-soluble substances pass through capillaries?
By moving through fenestrations (endothelial pores).
81
How do large proteins cross capillary walls?
Via pinocytotic vesicles through receptor-mediated transport.
82
What is the function of the blood-brain barrier?
It prevents most molecules from leaving the blood and entering the brain.
83
What type of capillaries form the BBB?
Continuous capillaries with complete tight junctions.
84
Why do BBB capillaries lack intercellular clefts?
To prevent unwanted substances from passing through.
85
How do vital molecules like glucose cross the BBB?
Through active transport mechanisms.
86
Which substances can pass through the BBB without transporters?
Lipid-soluble substances, including some anesthetics.
87
Why is the BBB highly selective?
Tight junctions create a barrier, allowing only specific molecules to be actively transported.
88
What is the function of veins?
To return blood from capillaries to the heart.
89
Why do veins have valves?
To prevent backflow, unlike arteries.
90
How do veins change as they move toward the heart?
Their diameter increases, and walls thicken.
91
What do capillaries unite to form?
Venules.
92
What are post-capillary venules made of?
Only endothelium.
93
Why are venules extremely porous?
To allow easy movement of fluid and white blood cells.
94
What structural differences exist in larger venules?
They have 1–2 layers of smooth muscle and a thin tunica externa.
95
What do venules unite to form?
Veins.
96
How do vein walls compare to arteries?
They are thinner, with larger lumens.
97
How does the tunica media in veins compare to arteries?
It contains little smooth muscle or elastin.
98
Which tunic is the thickest in veins?
The tunica externa, rich in collagen and elastin fibers.
99
Why can vein walls be thinner than arteries?
Because blood pressure in veins is lower.
100
Why are veins called capacitance vessels?
They store a large volume of blood, like a capacitor stores electricity.
101
How does vein structure allow them to hold more blood?
Their large lumen and thin walls accommodate high blood volume.
102
What percentage of the blood supply can veins hold?
Up to 65%.
103
What is the function of venous valves?
To prevent blood from flowing backward.
104
How do venous valves work?
They are passive and driven by pressure changes.
105
What are venous valves formed from?
Folds of the tunica intima.
106
Where are venous valves most abundant?
In veins of the limbs, where gravity affects blood flow.
107
Are venous valves present in thoracic and abdominal veins?
They are usually absent but can sometimes be found.
108
How do skeletal muscles assist venous return?
Their contraction squeezes veins, forcing blood upward past valves.
109
What are varicose veins?
Dilated veins caused by incompetent valves.
110
What are contributing factors to varicose veins?
Heredity and conditions that hinder venous return (e.g., prolonged standing, obesity, pregnancy).
111
Why does blood pool in varicose veins?
Increased pressure weakens valves, causing veins to stretch and become floppy.
112
Which veins are most susceptible to varicose veins?
Superficial veins, as they receive little support from surrounding tissues.
113
Why does blood pooling cause vein dilation?
The lack of structural support allows the vessel walls to stretch under pressure.
114
What are venous sinuses?
Highly specialized, flattened veins with thin walls composed only of endothelium.
115
What supports venous sinuses structurally?
Surrounding tissues.
116
What are examples of venous sinuses?
The coronary sinus and dural venous sinuses of the brain.
117
What is deep vein thrombosis (DVT)?
A clot that forms in the veins of the lower extremities (sometimes upper).
118
What is a major complication of DVT?
The clot can detach, travel to the lungs, and cause a pulmonary embolism.
119
What are common causes of DVT?
Sluggish blood flow, abnormal clotting chemistry (e.g., Leiden factor V), or vascular damage.
120
What are treatments for DVT?
Anticlotting drugs and placement of a Greenfield filter in the inferior vena cava.
121
What is an aneurysm?
An out-pocketing of an artery or vein, increasing the risk of rupture.
122
Where do aneurysms most commonly occur?
In the aorta, but they can also occur in veins.
123
What are potential causes of aneurysms?
Congenital defects, hypertension, and arteriosclerosis.
124
How does smoking affect aneurysm risk?
Even six months of smoking increases lifelong aneurysm risk.
125
What imaging views are used to detect aortic aneurysms?
Transverse and sagittal (longitudinal) views.
126
How does diabetes affect blood vessels?
Elevated blood sugar deposits glycoproteins in capillary basement membranes.
127
What happens to capillary walls in diabetic microangiopathy?
They become thickened but leaky.
128
How does diabetic microangiopathy impair circulation of nutrients and wastes?
It reduces nutrient delivery and waste removal.
129
Why does diabetes cause neuropathy?
Poor circulation leads to reduced oxygen, nutrients, and clearance of metabolic waste.
130
How is diabetes now viewed in terms of disease progression?
As a spectrum disease, where metabolic syndrome can cause early, subclinical vascular damage before diabetes is officially diagnosed.
