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Histology Cole > Lecture 11 Circulatory System > Flashcards

Lecture 11 Circulatory System Flashcards

1
Q

Primary function of circulatory system

A
  • transport O2/CO2 and nutrients/metabolic waste
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2
Q

Invertabreates

A
  • open circulatory system
  • no vessels
  • blood sloshes around
  • dont use bloodstream as primary way to oxygenate tissue
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3
Q

Secondary functions

A
  • thermoregulation (fluid holds temp really well)

- transport of immune cells/hormones

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4
Q

Vascular system consists of heart and blood vessels

A

blood vascular system

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5
Q

2 components of blood vascular system

A
  • pulmonary circulation

- systemic circulation

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6
Q

Pulmonary circulation

A
  • right half of the heart

- RA & V –> pulmonary aa –> lungs –> pulmonary Vv –> Left atrium –>

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7
Q

Systemic circulation

A

LA and V –> aaorta –> rest of body

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8
Q

Lymph vascular system

A
  • passive drainage system for returning extravascular fluid (lymph) to blood vascular system
  • lacks intrinsic pump, relies on Mm contraction, body movement
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9
Q

Blood vessels have three layers/tunics

A
  1. Tunic intima- innermost layer
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10
Q

Tunica intima

A
  • innermost layer of blood vessels
  • 1-2 cells thick
  • forms semi-permeable barrier supported by basement membrane
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11
Q

What kind of junctions does the tunica intima have?

A
  • fascia occludens
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12
Q

What allow for diapedesis of white blood cells?

A
  • fascia occuldens
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13
Q

Internal elastic lamina

A
  • seperates tunica intima and media

- composed of elastic fibers

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14
Q

Tunica media

A
  • highly variable middle layer
  • smooth mm cells and fibroblastic connective tissue
  • may also contain reticulin (type 3 collagen) and elastic fibers
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15
Q

What is the tunica media composed of?

A
  • smooth mm cells and fibroblastic connective tissue
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16
Q

What is the thickest layers in arteries?

A
  • tunica media
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17
Q

External elastic lamina

A
  • if present located between tunica media and adventitia

- also composed of elastic fibers but less organized than internal elastic lamina

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18
Q

Tunica adventitia

A
  • outermost layer of blood vessels
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19
Q

What makes up tunica adventitia?

A
  • loose fibroblastic connective tissue

- fibroblasts, collagen, elastic fibers, smooth muscle cells

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20
Q

Is the tunica adventitia thicker in arteries or veins?

A

Veins

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21
Q

What is the thickest layer in veins?

A
  • tunica adventitia
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22
Q

What do large vessels contain in their tunica adventitia?

A
  • vasa vosorum
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23
Q

What are vasa vosorum?

A
  • small blood vessels that supply the tunica media and adventitia in both large arteries and veins
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24
Q

Walls of blood vessels are too thick, how do nutrients and oxygen reach them?

A
  • small blood vessels like vasa vosorum
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25
Nervi vasculares
- autonomic nerves - responsible for vasoconstricion and vasodilation - control smooth muscle contraction in vessel walls
26
What stimulates vasconstriction of blood vessels?
- sympathetic post-ganglionic nerve fibers | - These fibers act on smooth muscle of tunic media causing vasoconstriction and decrease in lumen diameter
27
Vasodilation is controversial, there are 3 schools of thought
1. Passive; occurs in absence or inhibition of sympathetic stimulation 2. Accomplished via indirect parasympathetic innervation ( Ach causes endothelial cells to release nitrous oxide (NO) which 2' causes smooth Mm cells to relax) 3. In response to low O2 tension, smooth muscle in walls of arterioles relax- results in vasodilation and increase blood flow
28
Specialized sensory receptors in walls of blood vessels
- barroreceptors | - chemoreceptors
29
Baroreceptors
- located in carotid sinus and aortic arch | - detect blood pressure
30
Chemoreceptors
- located at bifurcation of carotid artery and in aortic bodies in aortic arch - detech changes in O2, CO2 tension and PH
31
Where are baroreceptors located?
- carotid sinusa and aortic arch
32
What do baroreceptors do?
- detect blood pressure
33
Where are chemoreceptors located
- bifurcation of carotid artery and in aortic bodies in aortic arch
34
What do chemoreceptors do?
- detect changes in O2, CO2 tension and PH
35
Arterial system
- conducts blood away from heart and to capillary bed
36
Venous system
- returns blood from capillaries to heart
37
What type of blood flow does the cyclical pumping of heart cause?
- pulsatile blood flow
38
Sytole
- contraction of ventricles | - pressure wave
39
Diastole
- ventricles relax | - drop in pressure
40
What maintains blood pressure?
- expansion and recoil of elastic arteries
41
Normal blood pressure
120/80
42
What regulates blood pressure?
- changes in diameter of blood vessels | - (occurs via sympathetic control of smooth muscle in vessel walls)
43
How do arteries resist pressure from pumping of heart?
- they contain large amounts of elastin and smooth muscle | (vessel wall thick relative to lumen diameter?
44
Arteries structure
- walls thick and lumen small
45
Three types of arteries
1. Elastic 2. Muscular arteries 3. Arterioles
46
Elastic arteries
- > 1 cm in diameter -- large conducting vessels, receive blood directly from heart - (aorta, common carotid, subclavian, pulmonary Aa) - Have sheets of elastic tissue in tunica media (helps maintain bp between systole and diastole) - Tunica media is thickest layer - Possess both internal and external elastic laminae
47
What are bigger muscular or elastic arteries?
- elastic
48
Muscular arteries
- 2-10 mm in diamter - medium sized distributing arteries - Have more smooth muscle and less elastin in tunica media than elastic arteries - Tunica media is thickest layer - Distinct internal elastic lamina; larger muscular artery may also contain external elastic lamina
49
What is the thickest layer of a muscular artery?
- tunica media
50
What has more smooth muscle, elastic or muscular artery?
- muscular
51
What artery has a distinct internal elastic lamina?
- muscular
52
Elastic lamina in muscular artery
- always have internal | - sometimes have external depending on size (bigger have it)
53
Do arterioles have elastic laminae?
- no it is absent
54
What is arteriole function?
- supply capillary beds - major sites of vasoconstriction and vasodilation - regulate distribution of blood capillaries via pre capillary sphincters, intermittent rings of smooth muscle within walls of arterioles
55
Arterioles
- 10-100 nm in diameter- contain relatively little smooth muscle (tunica media is only 2-3 cells thick)
56
Metarterioles
- small diamter arterioles - intermediate in size between arterioles and capillaried - characterized by discontinuous layer of smooth muscle in tunica media
57
Blood vessel trends
- amount of smooth muscle increases with increasing diameter of vessel (and relative amount of connective tissue decreases)
58
Microcirculation
- concerned with exchange of gases, fluids, nutrients, metabolites and waste products - occurs 1' within capilarries but also incluldes arterioles and venules
59
Capillaries
- thin walled vessels ~ 8-10 nm in diamter | - lined by thin single layer of endothelial cells supported by basal lamina and small #'s of pericytes
60
How do blood vessel pass through these tiny capillaries?
- fold over | - biconcave shape
61
Capillaries
- pericytes derives from same precursor cell as endothelial cells - can differentiate into endothelial cells or smooth muscle cells following injury - Capillaries lack outer connective tissue layer
62
Do capillaries have a tunic adventitia?
- no
63
do capillaries lack smooth muscle?
yes
64
Do capillaries exhibit vasomotor activity themselves?
-nope
65
Capillary vasodilation and vasoconstriction
- accomplished via smooth muscle contraction in arterioles and pre capillary sphincters --> passive change in capillary diameter
66
Types of capillaries
1. Continuous 2. Fenestrated 3. Disconstinuous
67
Continous
- endothelium forms continuous lining; most common (muscle, lung, CNS)
68
Fenestrated
- endothelial cells posses pores or fenestrae within cells (endocrine glands, GI tract) - want movement like for hormones
69
Discontinuous
- basal lamina not continuous; endothelial cells separated by large gaps between cells - discontinuous capillaries may form sinusoids (large diameter capillaries ~30-40 nm) - transport capillaries may occur via fenestrae, transcytosis, or diapedesis
70
Venous system
- fucntions as low pressure collecting system for returning blood from capillary beds to heart - thinner walled vessels with larger relative luminal diameter than corresponding arteries - fewer layers of smooth muscle in tunica media compared to similar sized aa - tunica adventitia thickest of 3 layers in vv - valves prevent backflow especially in limbs and thorax
71
Varicose veins
- valve failure in legs
72
Girafes
- have valves in carotid arteries to prevent backflow | - also have valves to prevent blood from rushing to head when bending over
73
Most common place where vein valves fail?
- legs
74
Lasers
- damage vessel by light and closes vessel by fibrosis
75
Venules
- smallest of veins - lack elastic laminae and smaller venules may lack tunica media - enlarge intercellular spaces which leads to increased permeability of vessel
76
Post capillary venules
- 10-50 nm in diameter - both tunica media and adventitia reduced or absent - post capillary venules preferential site for diapedesis
77
Where is the preferential site for diapedesis?
- post capillary venules
78
Where do post capillary venules drain?
- into larger collecting venules; then muscular venules
79
Muscular venules
- 50-100 nm in diameter with thin smooth muscle layer in tunica media - thicker tunica adventitia
80
Where do vasoactive substances like histamine and seratonin act?
- venules
81
Venules Enlarging intercellular spaces can lead to?
- edema (fluid accumilation)
82
Muscular veins
- small muscular vv may or mat not contain internal elastic lamina - medium muscular vv contain internal elastic lamina only - large muscular vv contain internal and external eslastic laminae - smooth muscle in tunica media controls luminal diameter of muscular vv and venules
83
AV shunts
- direct connections between arterial and venous system - bypass capillary bed - type of anastomosis; common in skin function in thermoregulation
84
Portal vessels
- Venous or arterial directly connecting two capillary beds | hepatic portal vein, a venous portal system
85
Atherosclerosis
- when endothelium of vessel damaged, cholesterol adheres to exposed proteins - once endothelium heals, cholesterol patch reabosrbed (cholestrol can induce a inflammatory response) - phagocytosis by machrophages later by enothelial and subintimal cells -> (foam cells)
86
foam cells
- mostly macrophages | - contain cholesterol
87
If inflammatory response of cholesterol becomes chronic what happens?
- atherosclerosis and plaque formation
88
What happens if endothelium is damaged and exposes underlying collagen?
- clotting cascade happens
89
Thrombous breaks off
- embolus aka thromboembolic disease
90
What is atherosclerosis accompanied by later in process?
- proliferation of smooth muscle cells and formation of fibrous connective tissue capsule -
91
What happens when cells within plaque die?
- necrosis and secondary calcification (aka hardening of arteries)
92
Why is atherosclerosis often associated with hypertension?
- decrease in diameter of vessel lumen and increase in systolic blood pressure
93
Most common cause of ischemic heart disease?
- athersclerosis | - lumen of corony aa may decrease by 90%
94
Gradual narrowing by plaque
stenosis | leads to thrombosis or occlusion of cessel
95
Sudden occlusion by embolus
acute ischemic event
96
decrease in O2 anoxia to heart muscle
leads to chest pain (angina)
97
Myocardial infarction
- if untreated and portion of muscle dies --> MI (death by ischemia) -
98
Can you regenerate cardiac muscle?
- no cardiac muscle cells are in Go phase or terminally differentiated
99
What do the fibroblast replace damaged cardiac muscle with?
- connective tissue (which is less contractile than muscle and leads to a decrease function or partial loss of function)
100
Enocarditis
- inflammation and thickening of AV valves often associated with valvular incompetence --> increase turbulence, regurgitation
101
Regurgitation leads to
- vegetative endocarditis and thromboembolic disease
102
Stroke
similar to MI but affects brain - neurons also terminally differentiated - results in cerebral infarct with similar cell death and loss of function - location of clot determines symptoms and severity
103
What happens when blood vessels dilate to form thin walled balloon like regions??
- aneurism
104
Where are aneurisms common?
aorta
105
Can aneurisms burst?
yes
106
Lymph vascular system
- structurally similar to veins but endothelial cells thinner with greater permeability - lymph endothelial cells highly active in phagocytosis - very thin tunica media - valves present; basement membrane and pericytes may be present or absent
107
Lymph vessel function
- drain excess fluid or lymph and return to blood stream
108
Lymph
- formed as result of high hydrostatic pressure in arterioles; exceeds colloid oncotic pressure exerted by plasma proteins -> leakage of water, electrolytes, and plasma proteins from capillaries into ECS
109
Where does lymph return to blood stream?
- junction of left internal jugular vein and left subclavian vein
110
Large lymphatic vessels
- have contractile system but no central pumping mechanism
111
Why is lymph formed?
- recycles high protein fluid that you don't want lost to Extracellular space
112
What generally moves the lymph?
- general body movement and skeletal muscle contraction
113
sitting still
- leads to edema (cant pump fluid)
114
ECS is drained by a series of interconnected blind-ending tubules called?
lymphatics
115
Where do lymph vessels converege?
- on thoracic duct (R lymphatic duct) largest lymph vessels in body
116
Lymph nodes
- interspersed along lymph vessels - contain lymphoid tissue for antigenic sampling and recognition activation of immune cells and production of Ab - when they find invaders they are ready to respond
117
Asymmetrical drainage
- importance with cancer patients
118
Easiest way to identify lymph vessels in section
- thin walled - lack blood - contain smooth eosinophilic proteinaceous fluid (lymph) occasional WBC's - basement membrane rudimentary or absent +/- pericytes
119
Where is asymmetrical drainage common?
- thorax | - breast tumor significance
120
Aggressive tumors
- develop wonderlust | - use blood system and lymphatics to travel
121
Elephantiasis
- tropical disease - due to small warm than hangs in lymphatics and migrates to lymph nodes - get absence of lymphatic return - common in legs or groin

Histology Cole (7 decks)

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