CHAPTER 15 BLOOD VESSELS Part B
Body contains closed circuit of tubes to transport blood between heart & body cells.
I. Vessels: arteries, arterioles, capillaries, venules, & veins
Fig. 15.24, 25 & 28
A. Arteries & arterioles
1. Arteries: carry blood ___________________________ heart
2. Adapted to withstand _____________
3.Arterioles: small branches of arteries
B. Walls of arteries
1. Endothelium, smooth muscle, connective tissue.
a. Inner layer - 1 layer of simple squamous epithelium = ___________________________
b.Rests on ______________________________ tissue membrane with elastic & collagen fibers
c .Prevents blood clots. How? Secretes biochemicals that inhibit _______________________
d. May secrete chemicals that dilate or constrict blood vessels
e. Provides ___________________________________________
2. Middle layer (tunica media)
a.________________________________________ fibers encircling tube + thick layer of elastic connective tissue.
b. Connective tissue enables vessels to withstand force of blood
pressure & to stretch suddenly.
3. Outer layer (tunica adventitia)
a. Thin; made of connective tissue with irregularly arranged elastic
& collagenous fibers.
b.__________________________________________________ to
surrounding tissues.
c. Contains small vessels (vas vasorum) that provide blood to
external cells of artery wall.
C. Nervous tissue: autonomic nerve fibers stimulate vasoconstriction/dilation.
1. Impulses on vasomotor fibers contract smooth muscles == __________
2. Inhibition of impulses == __________________________________
D. Walls of arterioles
1._________________________- layers like arteries
2. Become thin close to capillaries
3. Small arterioles: only endothelial lining + some smooth muscle
4. Arterioles give off branches: _________________________________
that join capillaries
5. What is an arteriovenous shunt? Fig. 15.27
II. Capillaries note diagram of capillary in Fig. 15.28 a
A. Connect arterioles & venules
B. Smallest blood vessels
C. Wall is single layer of cells that extend from arterioles & venules
D. Form semipermeable membrane.
E. Capillary permeability
1. Thin slits occur where endothelial cells of capillary _______________
2. ____________________________ of slits differ from tissue to tissue
3. In brain, endothelial cells of capillaries are tightly fused: forms
_________________________________________;
4. Some substances move through by _____________________________ diffusion.
F. Capillary arrangement:
1. Number of capillaries in a given area varies _________________with tissue metabolic rates.
a. Can you relate this to exercise? Does this explain the lack of vessels in cartilage?
2. Note the precapillary sphincters that open when cells are low in O2 &
nutrients; close when cells have adequate O2 & food.
D. Capillary exchange: Fig. 15.30
1. What is exchanged? Gases, nutrients, & metabolic by-products.
2. How? ________________________________
3. In order to diffuse easily the substance must be ____________________________ SOLUABLE.
4. Plasma proteins remain in blood.
5. ARTERIAL END OF CAPILLARY: Filtration (due to hydrostatic pressure of blood) causes net outward movement of fluid
6. VENULE END OF CAPILLARY: Osmosis causes net inward movement of fluid (note that proteins
remain in blood)
III. Venules and veins
A. Venules
1. Microscopic vessels�unite capillaries to veins
B. Veins
1. Walls have the 3 layers that are found in arteries, but tunica media is less developed in veins.
2. Veins have thinner walls compared to arteries�less smooth muscle &
less elastic tissue.
3. Veins have larger diameter compared to arteries.
4. Most have flap-like valves Fig. 15.32
5. Serve as a blood reservoir � When is this important in the human?
IV. Blood Vessel Disorders
A. Check clinical application 15.3
B. What is arteriosclerosis? atherosclerosis? an aneurysm?
V. Blood Pressure
A. What is blood pressure? ---- force blood exerts against the
inner walls of vessels; refers to _______________________________________________________..
1. Arterial blood pressure
a. Produced by __________________________________________
b. Rises & falls with phases of cardiac cycle
c. Systolic pressure: pressure in arteries when _________________________________
cntracts; this represents the maximum pressure achieved during contraction of the ventricles == 1st tapping sound
d. Diastolic pressure: pressure in arteries when _________________________________________ relaxes; ==after ventricles relax, pressure in the arteries drops; the diastolic
pressure is the lowest pressure before the next contraction. Sounds become __________________.
e. _____________________________ == expanding and recoil of an artery
wall
1.) Where to take pulse ---temporal, carotid, facial,brachial, radial, femoral, popliteal, & dorsalis pedis artery == tells us the ________ at which the left ventricle contracts.
f. HIGH BLOOD PRESSURE == PULSE FEELS _______________________
g. LOW BLOOD PRESSURE == PULSE IS EASILY _____________________
h. _______ --arterial systolic pressure; ________ -- arterial diastolic pressure
i. If cardiac output increases & arteries have to accept more blood
than can flow into peripheral vessels, then arteries are under
pressure even when ventricles are relaxed; this results in HIGH DIASTOLIC PRESSURE
2. What factors influence arterial blood pressure? Heart action, blood
volume, resistance to flow, blood viscosityFig. 15.35
a. Heart action: C O == stroke volume X heart rate
1.) Stroke volume: amount discharged from ventricle with
each contraction (70 milliliters at rest)
2.) Cardiac output = volume discharged from ventricle/minute
3.) If SV ___ , then C O ____ ; if H R ____ , then C O ___.
b. Blood volume: approximately 5 liters in adult
1.) B P is directly proportional to blood volume
2.) What happens to B P in dehydration? hemorrhage?
c. Resistance to flow: peripheral resistance hinders blood flow
1.) What is the effect of nicotine one peripheral resistance?
of caffeine? of alcohol?
2.) What happens to artery walls when the ventricle discharges
a surge of blood? Why?
d. Blood viscosity � refers to the ease with which molecules flow
past one another.
1.) What is one factor that can decrease blood viscosity?
2.)What is a factor that might increase blood viscosity?
e.Summary:arterial pressure _____ as cardiac output, blood
volume, peripheral resistance or viscosity ___.
B. CONTROL OF BLOOD PRESSURE Fig. 15.37, 38, 39
1. BP = C O X P R
a. Mechanisms that regulate cardiac output & peripheral resistance control blood pressure.
b. When C O ____ or _____, then blood pressure _____ or ____.
c. When P R ____ or _____, then blood pressure _____ or ____.
d. Thus, B P varies with cardiac output and peripheral resistance.
2. Factors that control CARDIAC OUTPUT: Fig. 15.37
mechanical factors, neural control, chemicals, temperature
a. Mechanical factors:
1.) Volume entering ventricle affects stroke volume.
2.) Why? = Starling's Law of the Heart-
a.) Stretched fibers contract with greater force
b.) Law ensures that vol. out = vol. in
c.) The more that enters, the stronger the contractions
d.) The result: à
SV __; CO __
3.) Can you think of a time when the amount entering the ventricle would increase? How would hemorrhage affect C O?
b. Neural control: Fig. 15.38, 15.39
1.) Baroreceptors in carotid and aortic arch sense high pressure
2.) Sensory impulses to cardiac center
3.) Parasympathetic impulses to heart
4.) S-A node inhibited
5.) Heart rate decreases; returns to normal
6.) Baroreceptors in carotid and aortic arch sense low pressure
7.) Results:
c. Chemical control
1.) ___________________________ from medulla of adrenal glands
2.) Heart rate ____, C O ___, B P _____ (fight/flight)
d. Body temperature
1.) ____ in body temperature will ___ B P
3. Factors that regulate peripheral resistance Fig.15.39
Peripheral resistance: is caused by friction between blood & vessel walls
When arterioles contract à
P R increases, blood backs up into arterioles &
arteries, thus blood pressure rises. Also, arteries become less distensible
over time, increasing P R. Thus, P R is determined mainly by the state of
the arterioles. Small changes in diameter of arterioles = big changes in
peripheral resistance
Figure 15.39
a. Vasomotor center
1.) Increase in B P stimulates baroreceptors in aortic arch/carotid bodies
2.) Sensory impulses travel to vasomotor center (located where?)
3.) Vasomotor center inhibited
4.) Less frequent sympathetic impulses to arteriole walls
5.) Result: vasodilation of arterioles, decr. P R, B P returns to normal
6.) This mechanism is important in controlling arterioles of abdominal viscera; arterioles stay in state of constant contraction from sympathetic stimulation. What would happen if these vessels were fully dilated?
b. Chemicals:CO2, O2, NO, H+ epinephrine, norepinephrine
1.) Incr in ___________, decr ____________, & decr in _____ results in relaxation of precapillary sphincters and smooth muscles in arterioles, allowing more blood into tissues with high metabolic rates (exercising muscles).
2.) Nitric oxide (NO, viagra)produced by endothelium & bradykinin (pain) acts as a vasodilator
3.) Angiotensin II act as vasoconsrictors (see additional class notes for important diagram on angiotensin)
4.) Epinephrine & norepinephrine cause vasoconstriction à incr. BP. Is this a beneficial effect or a harmful effect?
5.) Chemoreceptors (chemically sensitive cells in carotid & aortic bodies) send messages via sensory nerves to vasomotor center in medulla. Vasomotor center will cause constriction or allow dilation.
c. Viscosity affects peripheral resistance.
1.) As blood viscosity ___, BP ___; as blood viscosity __, BP ___.
C. CONTROL OF VENOUS BLOOD FLOW: --not direct result of heart action; B P decreases as blood moves through the arterial system and finally reaches
the capillaries. Very little pressure is left at venular ends of capillaries. Venous pressure depends on:
1. skeletalmuscle contraction (valves)
2 breathing movements--during inspiration thoracic pressure is less than abdominal; diaphragm is flat & down, ribs up & out & abdomen compressed; thus, blood squeezed out of abdomen & into thoracic cavity
3. vasoconstriction of veins
4 ._________________________________________-- from sympathetic reflexes; causes veins to constrict from stimulation of pressorectors in vena cava near entrance to right atrium. These send message to autonomic nervous system & heart will beat faster & more forcefully.
D. Central venous pressure = pressure in the rt atrium
1 . When central venous pressure increases because the heart isn't pumping hard enough, blood backs up in the venous network so the pressure increases there
2. When the heart beat is strong, central venous pressure & pressure in veins decrease
3. When injured -- fluid can accumulate in ________________________, compresses heart, heart can't beat. Sign: ________ in central venous pressure resulting in _________________________ of veins in neck.
a. Pressure in ________________________________ atrium
b. Affects pressure in peripheral veins
E. Rennin - Angiotensin System - draw diagram
F. Terms:
1. Valsalva maneuver -- strain with glottis closed -- intrathoracic
pressure _______ -- result: == less venous return to heart ;
2. hypertension, varicose veins; hemorrhoids; venous sinuses; anastomoses (alternative channels); systolic; diastolic; sphygmomanometer; stethoscope; sounds of Karotkoff.
3. Why do we take blood pressure?
4. What organs empty into the HEPATIC PORTAL SYSTEM fig 15.57?
What purpose does this system serve?
6. Which vessels make up the CIRCLE OF WILLIS at the base of the brain? fig 15.48
What is the purpose of this arrangement?
7. ANP
Helpful Activities to do after you finish reading this chapter