CH. 21 - PERIPHERAL CIRCULATION
I. GENERAL FEATURES
A. INTRODUCTION
1. 2 Circuits a. PULMONARY
b. SYSTEMIC
2. ARTERIES - AWAY from heart, SUPPLY
3. VEINS - TO heart, DRAIN
4. CAPILLARIES - Exchange, thermoregulation
B. CAPILLARIES (Fig. 21.1, p. 719)
1. WALL a. ENDOTHELIUM
b. BASEMENT MEMBRANE
c. ADVENTITIA - loose C.T.
d. PERICAP. cells - Fibroblasts, macrophages, undifferentiated smooth muscle cells
2. TYPES a. CONTINUOUS - no gaps in wall, lo flow, most
(Fig. 21.2, b. FENESTRATED - many “holes” in wall, hi flow, kidneys
p. 720) c. SINUSOIDAL - large holes in wall, endocrine
C. VESSEL STRUCTURE - 3 TUNICS (* KNOW Fig. 21.4, p. 721)
1. TUNICA INTIMA
a. ENDOTHELIUM
b. BASEMENT MEMBRANE
c. LAMINA PROPRIA - smooth muscle & C.T.
d. INTERNAL ELASTIC MEMBRANE - fenestrated
2. TUNICA MEDIA
a. SMOOTH MUSCLE
b. EXTERNAL ELASTIC MEMBRANE - fenestrated
c. NERVES & VASA VASORUM - “vessels of the vessel”
3. TUNICA ADVENTITIA - C.T., anchors
D. ARTERY TYPES - Tunica media thickest (Fig. 21.6, p. 723)
1. LARGE ELASTIC/CONDUCTING - Elastic C.T. > smooth muscle
2. MUSCULAR - Smooth muscle > C.T.
a. MEDIUM/DISTRIBUTING - regulate blood supply
b. SMALL - Vasoconstriction & vasodilation
3. ARTERIOLES a. To capillaries, still w/ 3 tunics
b. Vasodilate & vasoconstrict
E. VEIN TYPES - Tunica adventitia thickest
1. VENULES a. From capillaries
b. 2 tunics
2. SMALL - have 2 tunics, scattered muscle cells
3. MEDIUM/LARGE a. 3 tunics
b. ADVENTITIA thickest
4. VALVES a. MEDIUM & larger (2mm & up) to vena cava
b. Prevent BACKFLOW
c. Folds of Tunica Intima
d. More below heart than above
e. VARICOSE - incompetent valves èbackflow
- genetics & pregnancy
- PHLEBITIS - clots, inflamm. of veins
F. VASA VASORUM - “Vessels of the vessels” (Fig 21.4, p. 721)
G. NERVES
1. SYMPè Stim. vasoconstriction in skin, dilation is skel. muscles
2. TUNICA MEDIA
3. SENSORY - Baroreceptors - stretch
H. AGING 1. ARTERIOSCLEROSIS - hardening of arteries, Ca2+
2. ATHEROSCLEROSIS - deposits of fatty plaque (Fig. 21.7, p. 725)
p. 725-748 - Vessel names in lab, know clinical impacts (blue boxes)
II. DYNAMICS OF CIRCULATION - flow of blood
A. FLOW (Fig. 21.30, p. 749)
1. LAMINAR - concentric circles, streamlined
a. close to wall has é friction, ê rate
b. center has ê friction, é rate
2. TURBULENT - eddy currents, disruption of laminar flow
B. B. P.
1. Responsible for flow
2. Force of blood against walls
3. KOROTKOFF’S SOUNDS: a. 1st = systolic 120
(Fig. 21.31, p. 750) b. no sound = diastolic 80
C. VISCOSITY - resistance to flow, H20 =1, blood 3-4.5X
D. RATE - influenced by:
1. PRESSURE: é B.P. è é Flow, Proportional
2. RESISTANCE: êFlow, due to:
a. Viscosity
b. Vessel length & radius, friction against walls
c. é Resistanceè êFlow, Inversely proportional
E. CRITICAL CLOSING PRESSURE: ê Pressure in vesselècollapse, shock
F. LAPLACE'S LAW
1. Force = Diameter X Pressure
2. ANEURYSM = bulge, weak wall, pressure is greatest here
G. COMPLIANCE = é in volume due to é in pressure
1. Veins have large compliance, 24X greater than arteries
2. Major blood reservoir
III. PHYSIOLOGY OF CIRCULATION
A. VOLUME - ***KNOW Tab. 21.13, p. 752
B. VESSEL X-SECTIONAL AREA (Fig. 21.32, p. 752)
1. é Capillaries (2500cm2) è ê Velocity
2. ê Aorta (5cm2) è é Velocity
C. PRESSURE & RESISTANCE (Fig. 21.33, p. 753)
1. Highest B.P. in Aorta - 100 mmHg
2. Lowest B.P. in R. Atrium - 0 mmHg
3. Greatest D in B.P. & Resistance in Arterioles 85-30 = D 55!
D. PULSE PRESSURE = Diff. between Systol & Diastol.: 120-80 = 40
E. CAPILLARY EXCHANGE (Fig. 21.35, p. 755)
1. OUTWARD pressure in arterial; capillary ètissues
2. INWARD pressure in venous; tissues ècapillary/lymph
a. 9/10 returns to capillary è vein
b. 1/10 to lymphatic system
F. GRAVITY - affects B.P., ORTHOSTATIC differences: stand, sit, lie
IV. CONTROL OF BLOOD IN TISSUES (Tab. 21.15, p. 758)
A. INTRINSIC/LOCAL - to tissues as needed - Metabolism determines
1. SHORT-TERM by VASODILATORS, Cyclic
a. PRECAPILLARY SPHINCTERS @ Capillaries (Fig.21.36, p 759)
2. LONG-TERM by é Vascularization
a. é # of capillaries as muscles é in size
b. é # of capillaries as O2 less available, Colorado
B. EXTRINSIC REGULATION - by SYMP N.S. & HORMONES
(Fig. 21.37, p. 761)
V. BLOOD PRESSURE REGULATION
= MEAN ARTERIAL PRESSURE (M.A.P.) = C.O. x Peripheral Resistance
A. SHORT TERM - Act RAPIDLY (seconds/minutes)
1. BARORECEPTORS (Fig. 21.38, p. 762 & 21.39, p. 764)
a. Maintain B.P. under normal conditions
b. Aortic arch & Carotid sinus
2. HORMONAL - Adrenal medulla (Fig. 21.40, p. 765)
A é a. ADRENALINE/EPINEPHRINE è é B.P.
3. CHEMORECEPTORS - O2, CO2 & pH levels in blood (Fig 21.41, p 765)
a. é B.P. under EMERGENCIES
b. Lo O2, lo pH or Hi CO2
4. CNS ISCHEMIC RESPONSE – ê blood supply to tissues
a. Kicks in if ê blood supply to brain or if B.P. drops below 50 mm Hg
b. é B.P. under EMERGENCIES
5. SUMMARY OF SHORT-TERM (Fig. 21.42, p. 766)
B. LONG TERM - Act SLOWER (minutes/hours)
1. HORMONAL
A é a. RENIN-ANGIOTENSIN-ALDOSTERONE (Fig 21.43, p 768)
- Normal regulation AND response to SHOCK
- If B.P. ê è RENIN from Kidney
ê
ANGIOTENSINOGEN èANGIOTENSIN I èANGIOTENSIN II
i. é Vasoconstriction (é B.P.)
ii. é ALDOSTERONE è ê Urine vol., é H2O retention
iii. é Thirst
- RESULT IS é B.P., takes 20 minutes, active for 1 hour
A é b. ADH (VASOPRESSIN) (Fig. 21.44, p. 769)
- é Vasoconstriction, ê Urine volume è é B.P.
A ê *c. ATRIAL NATRIURETIC FACTOR
- Prod in R atria of heart in response to hi B.P.; walls stretch
- Causes ê in B.P., inhibits ADH, é Urine volume
2. FLUID SHIFT - between blood & interstitial spaces
3. STRESS-RELAXATION - smooth muscle tension
a. if B.P. é then muscles relax è ê B.P.
b. If B.P. ê then muscles contract è é B.P.
4. KIDNEY key organ in B.P. regulation due to urine production
5. SUMMARY OF LONG-TERM (Fig. 21.45, p. 770)