Regional Circulations
(pulmonary, skin, muscle, ■ cerebral, splanchnic, renal, fetal)
Assoc. Prof. MUDr. Markéta Bébarová, Ph.D.
Department of Physiology, Faculty of Medicine, Masaryk University
Regional Circulation
an organ may be supplied by two blood inflows:
- the nutrient circulation
- the functional circulation
various ways of anatomical and functional adaptation of an organ-specific circulation to provide the optimal function of the organ
varying impact of particular ways of regulation of the blood flow (~ vasal tone) in various organs ^
2 VCK
Pulmonary Circulation
Pulmonary Circulation
Blood flow through lungs is virtually equal to the blood flow through all other organs.
Functions:
- provide the gas exchange
- blood reservoir
- mechanical, chemical and immunological filter
Pulmonary Circulation
Arteries (differences compared to the arteries in the systemic circulation)
- bigger total cross-section of all pulmonary arteries
- smaller thickness of the vessel walls
- high compliance
Capillaries
- wide, abundant anastomoses form a net surrounding alveoles
- time of passage, area of perfused capillaries at rest and intensive exertion
Veins
- high compliance (blood reservoir, ortopnoe)
Blood pressure in pulmonary circulation !Xj
Pulmonary Circulation
Nutrient circulation
- physiological arteriovenous shunt
Pulmonary artery
Pulmonary vein
Bronchopulmonary arterial anastomosis
\
Bronchial artery
Bronchopulmonary vein
Bronchial vein xAzygosvein
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Lymphatic vessels
- fast transport of proteins and various particles from the peribronchial and perivascular tissue -» i formation of the tissue fluid ~ prevention of the pulmonary edema
No filtration in pulmonary capillaries physiologically!
1. pressures in intersticium and pulmonary capillaries
2. permeability of pulmonary capillaries
Pulmonary Circulation
• Regulation of blood flow in lungs
A. Systemic mechanisms
1) Neural regulation (sympathicus, parasympathicus)
2) Humoral regulation (circulating substances)
B. Local mechanisms
- chemical (metabolic) autoregulation
opposite reaction compared to systemic circulation (vasoconstriction)
C. Passive factors
- cardiac output ^
- gravity (blood distribution in lungs)
Pulmonary Circulation
Ratio of ventilation and perfusion
- kept constant (local metabolic autoregulation)
non-ventilated alveolus - vasoconstriction non-perfused alveolus - bronchoconstriction
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- decreased ratio -most often cause of hypoxic hypoxia in clinical practise fright-left shunt) -> I arterial blood saturation with 02
50 -
Decreasing VA/Q Normal
Increasing VA/Q
0
50 100 Po2 (mm Hg)
150
- content of C02 usually not changed
(compensatory hyperventilation in other alveoles)
Skin Circulation
Skin Circulation
• Skin blood flow considerably varies (0.02-5 l/min) Function:
• Metabolic demands of skin - small {decubitus)
Maintenance of body temperature
Poikilothermie tissue
Arteriovenous anastomoses Protection against environment
Maintenance of mean blood pressure
ASA
Skin Circulation
Arteriovenous anastomoses
- convoluted muscle vessels directly connecting arteriols and venules (low-resistance shunt)
capillaries
V.
Honzíkova N - Poznámky k přednáškám z fysiologie (1992)
- regulated by sympathetic vasoconstrictive nerve
fibers
Skin Circulation
Regulation of skin blood flow:
- Sympathetic nerve fibers
- Humoral - local factors
(histamine, Serotonine)
Skin Circulation
• Reaction on a temperature change:
1) direct impact of a temperature change on the vessel tone
2) excitation of skin thermoreceptors
3) excitation of thermoreceptors in brain
reflex modulation of
sympathetic vasoconstrictive activity
Skin Circulation
Axon reflex
Spinal cord
®
Sensory neuron
\
\
\
\
Endings in skin
■*   Orthodromic conduction
■>   Antidromic conduction
■*-   Direction taken by impulses
Endings near arteriole
Ganong's Review of Medical Physiology, 23rd edition.
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Muscle Circulation
Muscle Circulation
• Function:
1) Blood supply of muscles
the resting blood flow - 18% of the cardiac output vs. even 90% at intensive exertion (the local blood flow | even 20times)
2) Regulation of blood pressure
skeletal muscles - 40% of the body weight -> resistance of the muscle bloodstream has a high impact on the total peripheral resistance
• The blood flow during muscle activity is intermittent, during the tetanic contraction even zero (oxygen debt). fvf\h
Muscle Circulation
• Regulation of the muscle blood flow:
1) Neural regulation
dominates at rest (vasocontriction through sympathicus -big dilation reserve)
2) Local chemical regulation
dominates at physical exertion (metabolic vasodilation)
almost linear increase of the flow with increasing metabolic activity
increased blood flow + increased 02 extraction
t capillary pressure + | osmolarity -> | filtration edema in active muscles <
Cerebral Circulation
Cerebral Circulation
TABLE 34-1 Resting blood flow and 02 consumption of various organs in a 63-kg adult man with a mean arterial blood pressure of 90 mm Hg and an 02 consumption of 250 mL/min.
		Blood Flow		Arteriovenous	Oxygen Consumption		Resistance (R units}"		Percentage of Total	
Region	Mass (kg)	mL/min	mL/100 g/min	uxygen Difference (mL/L)	mL/min	mL/100 g/min	Absolute	per kg	Cardiac Output	Oxygen Consumption
Liver	2.6	1500	57.7	34	51	2,0	3.6	9.4	27.8	204
Kidneys	0.3	1260	420.0	14	18	6.0	4,3	1.3	23.3	7.2
Brain	1.4	750	54.0	62	46	3.3	7,2	10.1	13.9	184
Skin	3.6	462	12.8	25	12	03	11.7	42.1	8.6	4.8
Skeletal muscle	31.0	340	2,7	60	50	0,2	6,4	198.4	15.6	20.0
Heart muscle	0.3	250	84.0	114	29	9.7	21.4	6.4	4.7	11.6
Rest of body	23.8	336	1.4	129	44	0,2	16.1	383.2	6,2	17.6
Whole body	63.0	5400	8.6	46	250	0,4	1,0	63.0	100.0	100.0
aR units are pressure (mm Hg) divided by blood flow (rnLVs).
Re prod Lice d with permission from Bard P (editor): Medical Physiology, 1 Ith ed. Mos by, 1961,
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Cerebral Circulation
provides:
1) constant sufficient blood supply
(black-out during several seconds of the brain ischemia, irreversible damage during several minutes)
2) dynamic blood redistribution
(metabolic hyperaemia)
Cerebral Circulation
Anatomical specialities of cerebral circulation:
1) circulus arteriosus cerebri
(interconnection of main cerebral arteries by anastomoses)
2) very high density of capillaries
(3000 - 4000 capillaries / mm2 od the grey matter)
~ minimalization of diffuse distance for gases and other substances
3) very short arteriols
(almost 1/2 of the vasal resistance falls on arteries which are abundantly innervated) ^
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Cerebral Circulation
Functional adaptation of cerebral circulation: high and stable blood flow high 02 extraction
well developed autoregulation (myogenic and metabolic)
high reactivity on changes of C02 concentration local vs. total hypoxia innervation
Cerebral Circulation
• Special physical conditions of cerebral circulation:
1) solid cover of brain by skull
Monro-Kelli theory
flow may be increased only by acceleration of the blood flow, not by an increase of capacity of the bloodstream
Cushing reflex
2) gravity
orthostatic reaction (postural syncope)
• Blood-brain barrier
cerebral capillaries - tight inter-endothelial connections
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Cerebral Circulation
• Blood-brain barrier By free diffusion:
-> lipophilic substances (02, C02, xenon; unbound
forms of steroid hormones)
-> water (aquaporins; osmolality of blood and
cerebrospinal fluid is identical!)
-» glucose - the main source of energy for neurons
(free diffusion would be slow - accelerated by GLUT)
By transcellular transport (regulated):
-> ions (e.g. H+, HCO3" vs. C02 !)
-» transporters for thyroid hormones, some organic acids, choline, precursors of nucleic acids, aminoacids, ...
Cerebral Circulation
Blood-brain barrier Functions:
- maintenance of constant composition of the neuron environment
- protection of brain against endogenic and exogenic toxins
- prevention of loss of neurotransmitters to the bloodstream
Cerebral Circulation
Cerebrospinal fluid
- localization
- composition
- volume-150 ml,
rate of production -550 ml/d (exchange 3.7times/day)
Substance		CSF	Plasma	Ratio CSF/Plasma
Na+	(meq/kg H20)	147.0	150.0	0.98
K+	(meq/kg H20)	2.9	4.6	0.62
Mg2+	(meq/kg H20)	2.2	1.6	1.39
Ca2+	(meq/kg H20)	2.3	4.7	0.49
cr	(meq/kg H20)	113.0	99.0	1.14
HCO3-	(meq/L)	25.1	24.8	1.01
Pco2	(mm Hg)	50.2	39.5	1.28
pH		7.33	7.40	
Osmolality	(mosm/kg H20)	289.0	289.0	1.00
Protein	(mg/dL)	20.0	6000.0	0.003
Glucose	(mg/dL)	64.0	100.0	0.64
Inorganic P	(mg/dL)	3.4	4.7	0.73
Urea	(mg/dL)	12.0	15.0	0.80
Creatinine	(mg/dL)	1.5	1.2	1.25
Uric acid	(mg/dL)	1.5	5.0	0.30
Cholesterol	(mg/dL)	0.2	175.0	0.001
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Cerebral Circulation
Cerebrospinal fluid
Function:
- protection of brain
(together with menanges)
Ganong's Review of Medical Physiology, 23rd edition
Outer table of skull
Trabecular bone
Inner table of skull
Dura mater
Subdural
(potential)
space
Arachnoid
Subarachnoid space
Arachnoid trabeculae
Artery
Pia mater
Perivascular spaces
Brain
Cerebral Circulation
Cerebrospinal fluid
68   100 112 200 Outflow pressure (mm CSF)
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Cerebral Circulation
Paraventricular organs
~ brain regions where the blood-brain barrier is missing (fenestrated capillaries)
- secretion of polypeptides (oxytocin, vasopressin, ...),
- chemoreceptive zones (AP)
- osmoreceptive zones (OVLT)
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planchnic Circulation
Splanchnic Circulation
blood flow through GIT including liver and pancreas
blood flow through spleen
Main functional roles:
- metabolic function of GIT
- blood reservoir
- special (e.g. spleen - removal and degradation of old/altered erythrocytes)
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Splanchnic Circulation
• Blood reservoir
• at rest -20% of the total blood volume
• rich innervation with sympathetic vasoconstrictive fibers - a rec. (even 350 ml of the blood emptied into the systemic circulation during several minutes!)
Splanchnic Circulation
Intestinal circulation
(a. coeliaca, a. mesenterica superior and inferior)
submucous plexus, branches enter musculature and intestinal villi
countercurrent exchange of substances
Villus -
Simple columnar epithelium
Lacteal
Capillary network Goblet cells
Intestinal crypt
Lymph vessel
Arteriole Venule
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Splanchnic Circulation
Intestinal circulation
(a. coeliaca, a. mesenterica superior and inferior)
Regulation of blood flow:
- metabolic vasodilation (mediators: adenosine, j, [K+]e and | osmolarity)
- neural regulation - almost exclusively sympathicus, a > ß reo -> vasoconstriction
Splanchnic Circulation
Hepatic circulation {v. portae, a. hepatica)
25% of the cardiac output (~1.5 l/min) - Yav. portae, % a. hepatica
Regarding 02 supply, the ratio is opposite!
portal circulation
- 2 capillary bloodstreams in series (intestinal villi, liver sinusoids)
- I 02 content ->■ a. hepatica represents the nutritive hepatic circulation
Splanchnic Circulation
Hepatic circulation (v. portae, a. hepatica)
Sinusoids
Branch of the portal vein
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Splanchnic Circulation
Hepatic circulation (v. portae, a. hepatica)
pressures:
- a. hepatica:
- v. hepatica:
- v. portae:
- sinusoids:
Sinusoids
90 mmHg 5 mmHg 10 mmHg 2.25 mmHg
Bite canaliculi
Bile duct
Branch of the hepatic artery
Branch of the portal vein
Central vein
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"V, .^v-
Splanchnic Circulation
Hepatic circulation (v. portae, a. hepatica)
inverse regulation of blood flow in v. portae and a. hepatica:
- between meals: many sinusoids collapsed, flow in v. portae low, adenosine formed constantly and washed less -»• dilation of terminal hepatic arterioles
- after a meal: flow in v. portae t, adenosine washed faster ->• constriction of hepatic arterioles, higher flow in v. portae opens so far collapsed sinusoids
increased hepatic pressure (cirhosis) -> ascites
Splanchnic Circulation
• Hepatic circulation (v. portae, a. hepatica)
• Regulation of blood flow:
- neural: symp. vasoconstrictive fibers - a rec.
- metabolic: adenosine -»vasodilation
- passive: | BP    passive dilation of portal vein radicles -»| liver blood amount
congestive heart failure
diffuse noradrenergic discharge due to I BP
• sufficient 02 supply is essential for liver function! - j flow    t 02 extraction /Ä*i
Splanchnic Circulation
• Hepatic circulation (v. portae, a. hepatica)
• hepatic lymphatic circulation
- formation of almost 3A of the body lymph
- lymph rich on proteins (many plasmatic proteins are formed in hepatocytes + proteins from plasma due to the high permeability of sinusoids)
Fetal Circulation
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Fetal Circulation
placenta, umbilical vein
liver, ductus venosus
crista dividens, foramen ovale
blood supply of the head and upper limbs
v cava superior and inferior the right ventricle ductus arteriosus
Left atriui
Superior vena cava
Foramen ovale
62°/c
0 Ductus arteriosus
aorta - the blood supply of the lower part of body + 60% of the cardiac output is directed to placenta
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Pulmonary artery
Left
ventricle
Portal vein
Umbilical
From í placenta^
To placenta
Fetal Circulation
fetal haemoglobin
short-period hypoxia longer hypoxia
thick muscle wall of umbilical vessels
10 20 30 40 50 60 70  80 90 100 Po2 (mm Hg)
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Fetal Circulation
Loft atrium
Superior vena cava
Ductus arteriosus
Foramen ovale
Changes after birth
Closure of umbilical vein
- sudden | of peripheral resistance and blood pressure
- contraction of musculature of ductus venosus and its closure
The first inspiration (due to
asphyxia and cooling of the body)
- i resistance of the lung bloodstream
- much more blood into lungs
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Pulmonary artery
Left
ventricle
Portal vein
Umbilical vein a
From '. placenta^
Fetal Circulation
Changes after birth
Decrease of pressure in right atrium and its increase in left atrium due to:
- t filling of left atrium by the blood from lungs
- I venous return to right atrium due to closure of umbilical vein
- left ventricle works against t pressure in aorta
Closure of formanen ovale Closure of ductus arteriosus
Left atrium
Superior vena cava
Foramen ovale
Ductus arteriosus
Pulmonary artery
Left
ventricle
Portal vein
Umbilical vein
From placenta^
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Renal Circulation
Renal Circulation
main functions of kidneys
High filtration rate requires an adequate blood supply!
- kidneys form only -0.4 % of the body weight
- blood flow 1.2 l/min, -25% of cardiac output
distribution of blood flow is irregular, the most flows through cortex (glomeruli - filtration)
Renal
Circulation
Cortical radiate vein
Cortical radiate artery
Arcuate vein
Arcuate artery Interlobar vein Interlobar artery Segmental arteries Renal vein
Renal artery Renal pelvis
Ureter
Renal medulla
Renal cortex
(a) Frontal section illustrating major blood vessels
O 2013 Pearson Education, Ire
Aorta
I
Renal artery
Segmental artery
Interlobar artery
I
Arcuate artery
Cortical radiate artery
i"
Afferent arteriole
Inferior vena cava
Renal vein
Interlobar vein
í
->- Arcuate vein
í
Cortical radiate vein
4-
Peritubular capillaries -or vasa recta
Efferent arteriole
Glomerulus (capillaries}
J
riesl-1
Nephron-associated blood vessels (see Figure 25,7)
(b) Path of blood flow through renal blood vessels
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http://classes.midlandstech.edu/carterp/Courses/bio211/chap25/chap25.htm
pressure pressure (60 mm Hg)    (32 mm Hg)
v. aff., v. eff.
Bowman's capsule pressure (18 mm Hg)
glomerular blood flow =
P   - P
1 v.a.    1 v.e.
Guy ton & Hall.
Textbook of Medical Physiology
t resistance in vas aff. or vas eff. -> I the renal blood flow (if the arterial pressure is stable)
regulate the glomerular filtration pressure:_
constriction of vas aff. -» i glomerular pressure -» i filtration constriction of vas eff. -» t glomerular pressure -» t filtration
Renal Circulation
• Regulation of renal blood flow:
1) Myogenic autoregulation
2) Neural regulation
3) Humoral regulation
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Renal Circulation
Regulation of renal blood flow:
1) Myogenic autoregulation
- dominates
- provides stable renal filtration activity by maintaining stable blood flow at varying systemic blood pressure
Renal Circulation
• Regulation of renal blood flow:
2) Neural regulation
- conformed to demands of systemic circulation
- sympathetic system - norepinephrine
light exertion/upright body posture -> t sympathetic tone -> t tone of v. aff. and eff. -> I renal blood flow but without^ GFR (t FF)
higher t of sympathetic tone - during anesthesia and pain - GFR may already I
Renal Circulation
• Regulation of renal blood flow:
3) Humoral Regulation
- contribute to regulation of systemic BP and regulation of body fluids
- NE, E (from the adrenal medulla)
constriction of aff. and eff. arterioles -»• -l renal blood flow and GFR
(small impact with the exception of serious conditions, for example serious bleeding)
Renal Circulation
• Regulation of renal blood flow:
3) Humoral Regulation
- contribute to regulation of systemic BP and regulation of body fluids
- endothelin
constriction of aff. and eff. arterioles ->• I renal blood flow and GFR
released locally from the impaired endothel (physiological impact - hemostasis; pathologically increased levels at the toxemia of pregnancy, acute renal failure, chronic uremia)
Renal Circulation
• Regulation of renal blood flow:
3) Humoral Regulation
- contribute to regulation of systemic BP and regulation of body fluids
- NO
continual basal production vasodilation ->• stable renal blood flow and GFR
- prostanglandins (PGE2, PGI2), bradykinin
->• vasodilation
minor impact under physiological conditions non-steroidal anti-inflammatory agents during stress!
Renal Circulation
Regulation of renal blood flow:
3) Humoral regulation
- contribute to regulation of systemic BP and regulation of body fluids
- Renin-angiotensine Glomerulus system
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Afferent arteriole