Regional Circulations
(pulmonary, skin, muscle, cerebral, splanchnic, renal, fetal)
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 oraans ^
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 fjfj
Pulmonary Circulation
Nutrient circulation
- physiological arteriovenous shunt
Pulmonary artery
Pulmonary vein
Bronchopulmonary arterial anastomosis
\
Bronchial artery
Bronchopulmonary vein
Bronchial vein xAzygosvein
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
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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
Ganong's Review of Medical Physiology, 23rd edition
decreased ratio -most often cause of hypoxic hypoxia in clinical practise (right-left shunt) -> 1 arterial blood saturation with 02
50
CM
8
CL
Decreasing VA/Q Norma|
Increasing VA/Q
0
50
100
150
Po2 (mm Hg)
content of C02 usually not changed
(compensatory hyperventilation in other alveoles)
Skin Circulation
z
Skin Circulation
• Skin blood flow considerably varies (0.02-5 i/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)
capillaries
a/r  AVA /
v
Honzíkova N - Poznámky k přednáškám z fysiologie (1992)
- regulated by sympathetic vasoconstrictive nerve fibers
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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 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). #Vtv*i
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}0		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	20.4
Kidneys	0.3	1260	420.0	14	18	6.0	4.3	13	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
aR units are pressure (mm Hg) divided by blood flow [mUs).
Reproduced with permission from Bard P (editor!: Medical Physiology, 11th eel. Mos by, 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
2
3
4
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
erebral Circulation
100
LL
m
o
50
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
Ganong's Review of Medical Physiology, 23rd edition
Nucleus ^ Mitochondrion
Glucose, etc
Tight junction
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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
HC03-	(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
Ganong's Review of Medical Physiology, 23rd edition
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
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Cerebral Circulation
Cerebrospinal fluid
1.6
_ 1.2 £
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)
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Cerebral Circulation
Measurement of cerebral blood flow
Kety method
- Fick principle, method of indicatory gas
- nitrous oxide N20
NoO concentration in the venous blood
cerebral blood flow =
-i-s
N20 removed from blood by brain / time
average arteriovenous difference of N20
average blood flow through all perfused regions!
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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)
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, I [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) - ZA v. portae, % a. hepatica
• portal circulation
- 2 capillary bloodstreams in series (intestinal villi, liver sinusoids)
- i 02 content -> a. hepatica represents the nutritive hepatic circulation
Regarding 02 supply, the ratio is opposite!
Splanchnic Circulation
Hepatic circulation (v. portae, a. hepatica)
Sinusoids
functional unit - acinus
Bile canaliculi
Bile duct
Branch of the hepatic artery
Branch of the portal vein
Central vein
Ganong's Review of Medical Physiology, 23rd edition
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Splanchnic Circulation
• Hepatic circulation (v. portae, a. hepatica)
Sinusoids
• pressures:
- a. hepatica: 90 mmHg
- v. hepatica: 5 mmHg
- v. portae: 10 mmHg
- sinusoids: 2.25 mmHg
Branch of the portal vein
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Medical Physiology,
23rd edition iAfXi
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: t BP    passive dilation of portal vein radicles -» t 'iver blood amount
congestive heart failure
diffuse noradrenergic discharge due to l 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
(a) Frontal section illustrating major blood vessels
O 2013 Bearson Education Inc
Aorta
I
Renal artery
I
Segmental artery
Interlobar artery
I
Arcuate artery
I
Cortical radiate artery
I-
1 Afferent arteriole
i , I
Inferior vena cava
í
Renal vein
í
Interlobar vein
í
Arcuate vein
í
Cortical radiate vein
4
Peritubular capillaries -or vasa recta
Efferent arteriole
■*■ Glomerulus (capillaries)
J
Nephron-associated blood vessels (see Figure 25.7)
(b) Path of blood flow through renal blood vessels
http://classes.midlandstech.edu/carterp/Courses/bio211/chap25/chap25.htm
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Cortical nephron Juxtamedullary nephron
• Short nephron loop • Long nephron loop
• Glomerulus further from the cortex-medulla junction • Glomerulus closer to the cortex-medulla junction
• Efferent arteriole supplies peritubular capillaries * Efferent arteriole supplies vasa recta
- Cortical radiate vein
- Cortical radiate artery
- Afferent arteriole
- Collecting duct
- Distal convoluted tubule
- Afferent arteriole
Efferent arteriole
© 2013 Pearson Education. Inc.
F renal cortical tissue (180X)
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http://classes.midlandstech.edu/carterp/Courses/bio211/chap25/chap25.htm
v. aff., v. eff.
t
Bowman's capsule pressure (18 mm Hg)
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 I 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 ->• 4- 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) Uy?^
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 Gomerulus
system
Ganong's Review of Medical Physiology, 23rd edition
Renal Circulation
Renin-angiotensine system
l   Na+in plasma Juxtaglomerular/^^
apparatus
i BP
sympathetic activity (P rec.)'
Angiotensinogen
i"
Angiotensin I
I
Angiotensin-
Increased renal arterial mean pressure, decreased discharge of renal nerves
Increased extracellular fluid volume
converting enzyme
Angiotensin II
Aldosterone
vasoconstriction thirst, ADH
Adrenal cortex
Decreased Na+ (and water) excretion
u_r     mw \. ma
Ganong's Review of Medical Physiology, 23rd edition \Af/
■2-
Renal Circulation
Determination of renal plasma flow velocity (RPF)
Clearance of a substance which is fully cleared from plasma in glomerulotubular apparatus.
PAH (paraaminohippuric acid) cleared by 90%
PPAH = 0.01 mg/ml -
RPF =
5.85 x 1 mg/min 0.01 mg/ml
= 585 ml/min
Renal plasma flow
>- 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):
■PAH
PpAH " VpAH
PAH
= 0.9
^           585 ml/min l# .
■> RPF =-= 650 ml/min
0.9
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 atriu
Superior vena cava
Foramen ovale
62°/c
o Ductus arteriosus
to
From
placental.
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
Aorta
58%
Portal vein
Umbilical vein
To placenta
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Fetal Circulation
fetal haemoglobin
short-period hypoxia longer hypoxia
thick muscle wall of umbilical vessels
Fetus
10 20 30 40 50 60 70  80 90 100 Po2 (mm Hg)
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Fetal Circulation
Left 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
Ganong's Review of Medical Physiology, 23rd edition
Portal vein
Umbilical vein a
i
From
placental.
Pulmonary artery
Left
ventricle
■2-
"V, .^v-
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
Right ventricle Ductus venosus
Portal vein
Umbilical vein
From placental.
Ductus arteriosus
Pulmonary artery
Left
ventricle
Ganong's Review of Medical Physiology, 23rd edition