Regional Circulations
(pulmonary, skin, muscle, cerebral, splanchnic, renal, fetal,
coronary)
Assoc. Prof. MUDr. Markéta Bébarová, Ph.D.
Department of Physiology, Faculty of Medicine, Masaryk University
This presentation includes only the most important terms and facts. Its content by itself is not a sufficient source of information required to pass the
Physiology exam.
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 ^
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
Pulmonary Circulation
Nutrient circulation
- physiological arteriovenous shunt
Pulmonary artery
Pulmonary vein
Bronchial artery
Bronchial vein    Azygos vein
Ganong's Review of Medical Physiology, 23rd edition
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
'fir/15
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
decreased ratio -most often cause of hypoxic hypoxia in clinical practise fright-left shunt) -» I arterial blood saturation with On
X
E 50 E
CM O Ü
A
V
Ganong's Review of Medical Physiology, 23rd edition
Decreasing VA/Q Norma,
Increasing VA/Q
50 100 Po2 (mm Hg)
150
content of C02 usually not changed
(compensatory hyperventilation in other alveoles)
Mr
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
Skin Circulation
Arteriovenous anastomoses
- convoluted muscle vessels directly connecting arteriols and venules (low-resistance shunt)
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)
. ****
it.
• 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
reflex
near arteriole
Ganong's Review of Medical Physiology, 23rd edition.
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 f 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).
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 + t osmolarity -> t 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)4		Percentage of Total	
Region	Mass (kg)	mL/min	mL/100 g/min	uxygen Difference (mL/L)	mL/100 mL/min 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	20.4
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	18.4
Skin	3.6	462	12.8	25	12 0.3	11.7	42.1	8.6	4.8
Skeletal muscle	31.0	840	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
3R units are pressure (mm Hg) divided by blood flow (mL/s).
Reproduced with permission from Bard P (editor): Medical Physiology, 1 Ith ed. Mosby, 1961.
Ganong's Review of Medical Physiology, 23rd edition
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)
Cerebral Circulation
• Functional adaptation of cerebral circulation:
1) high and stable blood flow
2) high 02 extraction
3) well developed autoregulation (myogenic and metabolic)
4) high reactivity on changes of C02 concentration
5) local vs. total hypoxia
6) innervation
Cerebral Circulation
sympathetic system
70 140 Arterial pressure (mm Hg)
Ganong's Review of Medical Physiology, 23rd edition.
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)
Cerebral Circulation
Blood-brain barrier
cerebral capillaries - tight inter-endothelial connections
Nucleus v Mitochondrion
Glucose, etc
Tight junction
Ganong's Review of Medical Physiology, 23rd edition
• 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
PC02	(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
Ganong's Review of Medical Physiology, 23rd edition
Cerebral Circulation
Cerebrospinal fluid Function:
- protection of brain
(together with menanges)
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
Ganong's Review of Medical Physiology, 23rd edition
Cerebral Circulation
Cerebrospinal fluid
1.6
_ 1.2 c
'E
E, 0.8 o
0.4
0
0 68   100 112 200
Outflow pressure (mm CSF)
Ganong's Review of Medical Physiology, 23rd edition
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)
Ganong's Review of Medical Physiology, 23rd edition
Cerebral Circulation
Measurement of cerebral blood flow Kety method
- Fick principle, method of indicatory gas
nitrous oxide N20
N20 concentration in the venous blood
r
cerebral blood flow =
N20 removed from blood by brain / time average arteriovenous difference of N20
-> average blood flow through all perfused regions!
Cerebral Circulation
Measurement of cerebral blood flow - regional
PET (positron emission tomography) fMRI (functional magnetic resonance)
Splanchnic 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)
y
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
Venule
Ganong's Review of Medical Physiology, 23rd edition
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 rec. vasoconstriction
Splanchnic Circulation
Hepatic circulation (v. portae, a. hepatica)
25% of the cardiac output (-1.5 l/min) - 3A v. 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
Ganong's Review of Medical Physiology, 23rd edition
Splanchnic Circulation
Hepatic circulation (v. portae, a. hepatica)
Sinusoids
pressures:
- a. hepatica:
- v. hepatica:
- v. portae:
- sinusoids:
Bile canaliculi
90 mmHg 5 mmHg 10 mmHg 2.25 mmHg
Bile duct
Branch of the hepatic artery
Branch of the portal vein
Ganong's Review of Medical Physiology, 23rd edition
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 |, 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! -1
flow -> t 02 extraction
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)
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
Aorta
i
Renal artery
Segmental artery
Interlobar artery
I
Arcuate artery
I
Cortical radiate artery
I
Afferent arteriole
L
Inferior vena cava
í
Renal vein
í
Interlobar vein
-*■ Arcuate vein
Cortical radiate vein
4-
Peritubular capillaries i
■or vasa recta
í
Efferent arteriole
Glomerulus (capillaries)
J
(a) Frontal section illustrating major blood vessels
O2013 Rtwion Eduutan. me.
Nephron-associated blood vessels (see Figure 25.7)
(b) Path of blood flow through renal blood vessels
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r
v. aff., v. eff.
glomerular blood flow =
P   - P
1 v.a.    1 v.e.
Guyton & Hall.
Textbook of Medical Physiology
Rv.a. + Rv.e. +
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
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 4 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 -» i 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 <*»»«*■
system
Ganong's Review of Medical Physiology, 23rd edition
Juxtaglomerular cells
Afferent arteriole
Renal Circulation
Renin-angiotensine system
l   Na+ in plasma Juxtaglomerular
apparatus
I BP ^ t sympathetic activity ((3 rec.)'
Angiotensinogen <-
I-
Renin
Angiotensin I
I-
Angiotensin II
Angiotensin-
Increased renal arterial mean pressure, decreased discharge of renal nerves
Increased extracellular fluid volume
converting enzyme
Aldosterone
vasoconstriction thirst, ADH
Adrenal cortex
Decreased Na+ (and water) excretion
Ganong's Review of Medical Physiology, 23rd edition
Renal Circulation
Determination of renal plasma flow velocity (RPF)
Clearance of a substance which      pPAH=oo1mg/m, * is fully cleared from plasma in glomerulotubular apparatus.
PAH (paraaminohippuric acid) cleared by 90%
Renal plasma flow
RPF =
5.85 x 1 mg/min 0.01 mg/ml
= 585 ml/min
^ Renal venous PAH = 0.001 mg/ml
UPAH = 5.85 mg/ml V = 1 ml/min
Guyton & Hall. Textbook of Medical Physiology
Correction to the extraction ratio of PAH (EPAH):
585 ml/min
■PAH
PpAH " VpAH _ Q g PpAH
+ RPF =
= 650 ml/min
0.9
Fetal Circulation
Fetal Circulation
Left atriu
Superior vena cava
62% Ductus
arteriosus
Foramen ovale
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
aorta - the blood supply of the lower part of body + 60% of the cardiac output is directed to placenta
Ganong's Review of Medical Physiology, 23rd edition
Pulmonary artery
Left
ventricle
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 P02 (mm Hg)
Ganong's Review of Medical Physiology, 23rd edition
Fetal Circulation
Left atrium
Superior vena cava
Ductus arteriosus
Foramen ovale
Changes after birth
Closure of umbilical vein
- sudden f 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
Ganong's Review of Medical Physiology, 23rd edition
Portal vein
Umbilical vein
From
placenta\
Pulmonary artery
Left
ventricle
Fetal Circulation
Changes after birth
Decrease of pressure in right atrium and its increase in left atrium due to:
- | 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 | pressure in aorta
Closure of formanen ovale Closure of ductus arteriosus
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Coronary Circulation
Coronary Circulation
a. cor sinistra a. cor dextra
02 diffusion directly from the blood situated in the cardiac cavities
placing of coronary arteries and capillaries in the cardiac walls; consequences!
Epicardial coronary arteries
Right coronary artery
Left coronary artery
Subendocardial arterial plexus
Circumflex branch
Anterior
descending
branch
Septal branches
Marginal branch
Marginal branch
Posterior descending branch
Ganong's Review od Medical Physiology, 23rd edition
Guyton and Hall. Textbook of Medical Physiology, 11th edition
Coronary Circulation
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Coronary Circulation
TABLE 34-4 Pressure in aorta and left and right ventricles (vent) in systole and diastole.
	Pressure (mm Hg) in			Pressure Differential (mm Hg) between Aorta and	
	Aorta	Left Vent	Right Vent	Left Vent	Right Vent
Systole	120	121	25	-1	95
Diastole	80	0	0	80	80
intramural vessels
left vs. right ventricle high heart rate
120
if) _2>
8? x 100 a- E I E
o <
0.4 0.6 Time (s)
1.0
Ganong's Review od Medical Physiology, 23rd edition
Coronary Circulation
02 extraction is almost maximal already at rest, capillaries are open
The only possibility how to increase 02 supply (for example during exercise) is the coronary vasodilation!
Coronary Circulation
Control of coronary blood flow
1) reduction/interruption of the blood flow or increased demands
hyperaemia (reactive or active) based on the metabolic vasodilation
Coronary Circulation
Control of coronary blood flow
2) the neural regulation of the vessel diameter-secondary impact
a) indirect effects w
Y (mostly opposite)
b) direct effects
Coronary Circulation
Control of coronary blood flow
2) the neural regulation of the vessel diameter-secondary impact
a) indirect effects
sympathetic system (NE, E)
f HR + contractility ->■ rate of cardiac metabolism -> increased 02 consumption ->• activation of local vasodilating mechanisms
parasympathetic system (ACH)
opposite changes —> vasoconstriction „^
Coronary Circulation
Control of coronary blood flow
2) the neural regulation of the vessel diameter-secondary impact
a) indirect effects
b) direct effects vasospastic
sympathetic system (NE, E)   myocardial ischemia
epicardial vessels - mostly a-rec. -> vasoconstriction intramural vessels - mostly |3-rec. -> vasodilation
parasympathetic system (ACH)
vasodilation, but not significant (only few fibers)
Coronary Circulation
Control of coronary blood flow
2) the neural regulation of the vessel diameter secondary impact
a) indirect effects
b) direct effects
Whenever the direct effects alter the coronary blood flow in the wrong direction the metabolic control overrides them
within seconds!
Coronary Reserve
• ability of coronary vessels to adapt blood flow to the actual cardiac work (ergometry)
• the maximal blood flow / the resting blood flow
• reduction of the coronary reserve:
- relative coronary insufficiency
- absolute coronary insufficiency (~ coronary heart disease)
Reduced coronary reserve is a limiting factor of the cardiac output, thus, also of the effort of organism!