Download Ch 11 Vascular System

Ch 11 - Vascular System
The Vascular System
Taking blood to the tissues and back
 Arteries, Arterioles – away from heart
 Capillaries – gas exchange
 Venules, Veins – toward the heart
Venous system
Large veins
(capacitance
vessels)
Small veins
(capacitance
vessels)
Postcapillary
venule
Thoroughfare
channel
Arterial system
Heart
Large
lymphatic
vessels
Lymph
node
Lymphatic
system
Arteriovenous
anastomosis
Elastic arteries
(conducting
vessels)
Muscular arteries
(distributing
vessels)
Lymphatic
Sinusoid
capillary
Arterioles
(resistance vessels)
Terminal arteriole
Metarteriole
Precapillary sphincter
Capillaries
(exchange vessels)
Figure 19.2
Blood Vessels: Anatomy
Three layers (tunics)
1.Tunic interna
 Endothelium
2.Tunic media
 Smooth muscle
 Controlled by sympathetic nervous
system
3.Tunic externa
 Mostly fibrous connective tissue
Tunica intima
Tunica media
Tunica adventitia
Differences Between Blood Vessels
 Walls of arteries are the thickest
 Lumens of veins are larger
 Walls of capillaries are only one cell layer thick to
allow for exchanges between blood and tissue
Table 19.1 (1 of 2)
Table 19.1 (2 of 2)
Arteries
• Carry blood away from the
heart.
• Thick layer of smooth muscle.
• Pulse, pulse points.
Arterioles
• Smallest arteries
• Lead to capillary beds
• Control flow into capillary beds via
vasodilation and vasoconstriction
Capillaries
• very thin walled microscopic
blood vessels across which
gases are exchanged.
Capillaries cont.
• So small that blood cells flow
through single file.
• Made only of thin epithelium,
so gases, nutrients, and
wastes can diffuse in and out.
Capillaries
• In all tissues except for cartilage, epithelia,
cornea and lens of eye
Venules
Veins
• Blood returns to the heart.
• Very low pressure, blood flows
against gravity.
Veins cont.
• One way valves to prevent
backflow. Squeezing of
skeletal muscle pumps blood
toward the heart.
Movement of Blood Through Vessels
 Most arterial blood is
pumped by the heart
 Veins use the milking
action of muscles to
help move blood
Figure 11.9
Varicose Veins
Capillary Beds
Capillary beds consist of
two types of vessels
1. Vascular shunt – directly
connects an arteriole to a
venule
2. True capillaries – exchange
vessels
 Oxygen and nutrients cross
to cells
 Carbon dioxide and
metabolic waste products
cross into blood
Figure 11.10
Capillary Exchange
 Substances exchanged due to
concentration gradients
 Oxygen and nutrients leave the blood
 Carbon dioxide and other wastes leave the
cells
Capillary Exchange: Mechanisms
 Direct diffusion across plasma
membranes
 Endocytosis or exocytosis
 Some capillaries have gaps (intercellular
clefts)
 Plasma membrane not joined by tight
junctions
 Fenestrations of some capillaries
 Fenestrations = pores
Diffusion at Capillary Beds
Figure 11.20
Relative crosssectional area of
different vessels
of the vascular bed
Total area
(cm2) of the
vascular
bed
Velocity of
blood flow
(cm/s)
Figure 19.14
Hepatic Portal Circulation
Hepatic Portal Circulation
• The term “PORTAL” is used to refer to
veins which carry blood to organs other
than the heart.
• Materials absorbed into the blood in the
digestive system are carried into veins
which anastomose into a single hepatic
portal vein which leads to the liver. There
those materials are processed before the
blood continues on to the heart.
Hepatic Portal Circulation Route
Inferior Vena Cava
Aorta
Celiac Artery
Digestive Organs
Hepatic Portal Vein
Liver
Hepatic Veins
Inferior Vena Cava
Right Atrium
Circulation to the Fetus
Fetal Circulation
Placenta
Umbilical Vein
Ductus Venosus
Inferior Vena Cava
Right Atrium
Foramen Ovale
Left Atrium
Right Ventricle
Pulmonary Truck
Ductus Arteriosis
Aorta
Ventricular Septal Defect
Animation
Patent Ductus Arteriosus
• Ductus Arteriosus fails to close after
birth.
• Blood flows from Aorta into Pulmonary
Arteries due to higher pressure in Aorta.
• Effects vary with size of patent opening.
– Small - no symptoms to physical
underdevelopment & increased respiratory
infection susceptibility. Heart murmurs
common.
– Large - may cause congestive heart failure.
Aorta
Patent Ductus Arteriosus
Pulmonary Artery
Pulse
 Pulse –
pressure wave
of blood
 Monitored at
“pressure
points” where
pulse is easily
palpated
Figure 11.16
Blood Pressure
 Measurements by health professionals
are made on the pressure in large
arteries
 Systolic – pressure at the peak of
ventricular contraction
 Diastolic – pressure when ventricles relax
 Pressure in blood vessels decreases as
the distance away from the heart
increases
Comparison of Blood Pressures in
Different Vessels
Figure 11.17
Measuring Arterial Blood Pressure
Figure 11.18
Variations in Blood Pressure
Human normal range is variable
Normal
 140–110 mm Hg systolic; varies with age
 80–65 mm Hg diastolic
Hypotension
 Low systolic (below 100 mm HG)
 Often no cause for concern
 Orthostatic hypotension
 Acute hypotension during shock
Hypertension
 High systolic (above 140 mm HG)
 High diasolic (above 90 mm Hg)
 Can be dangerous, increases peripheral
resistance. Strains heart and damages
vessels.
• Atherosclerosis – narrowing of a blood
vessel by a thickening of the wall of the
vessel.
• Arteriosclerosis – the end stage of the
disease. The damaged area of the blood
vessel hardens, frays, and ulcerates,
encouraging thrombus formation.
Blood Pressure: Effects of Factors
Neural factors
 Autonomic nervous system adjustments (sympathetic
division causes vasoconstriction)
Renal factors
 Regulation by altering blood volume
 Renin – Hormonal released from kidney. Results in
vasoconstriction and water retention.
Temperature
 Heat has a vasodilation effect
 Cold has a vasoconstricting effect
Chemicals
 Various substances can cause increases or decreases
Diet
3 Impulses from baroreceptors
stimulate cardioinhibitory center
(and inhibit cardioacceleratory
center) and inhibit vasomotor
center.
4a Sympathetic
impulses to heart
cause HR,
contractility, and
CO.
2 Baroreceptors
in carotid sinuses
and aortic arch
are stimulated.
4b Rate of
vasomotor impulses
allows vasodilation,
causing R
1 Stimulus:
Blood pressure
(arterial blood
pressure rises above
normal range).
Homeostasis: Blood pressure in normal range
5
CO and R
return blood
pressure to
homeostatic range.
1 Stimulus:
5
CO and R
return blood pressure
to homeostatic range.
Blood pressure
(arterial blood
pressure falls below
normal range).
4b Vasomotor
fibers stimulate
vasoconstriction,
causing R
2 Baroreceptors
in carotid sinuses
and aortic arch
are inhibited.
4a Sympathetic
impulses to heart
cause HR,
contractility, and
CO.
3 Impulses from baroreceptors stimulate
cardioacceleratory center (and inhibit cardioinhibitory
center) and stimulate vasomotor center.
Figure 19.9
Homeostasis: Blood pressure in normal range
1 Stimulus:
Blood pressure
(arterial blood
pressure falls
below normal
range).
Figure 19.9 step 1
Homeostasis: Blood pressure in normal range
1 Stimulus:
Blood pressure
(arterial blood
pressure falls
below normal
range).
2 Baroreceptors
in carotid sinuses
and aortic arch
are inhibited.
Figure 19.9 step 2
Homeostasis: Blood pressure in normal range
1 Stimulus:
Blood pressure
(arterial blood
pressure falls
below normal
range).
2 Baroreceptors
in carotid sinuses
and aortic arch
are inhibited.
3 Impulses from baroreceptors
stimulate cardioacceleratory center
(and inhibit cardioinhibitory center)
and stimulate vasomotor center.
Figure 19.9 step 3
Homeostasis: Blood pressure in normal range
1 Stimulus:
Blood pressure
(arterial blood
pressure falls
below normal
range).
2 Baroreceptors
4a Sympathetic
impulses to heart
cause HR,
contractility, and
CO.
in carotid sinuses
and aortic arch
are inhibited.
3 Impulses from baroreceptors
stimulate cardioacceleratory center
(and inhibit cardioinhibitory center)
and stimulate vasomotor center.
Figure 19.9 step 4a
Homeostasis: Blood pressure in normal range
1 Stimulus:
4b Vasomotor
Blood pressure
(arterial blood
pressure falls
below normal
range).
fibers stimulate
vasoconstriction,
causing R
2 Baroreceptors
4a Sympathetic
impulses to heart
cause HR,
contractility, and
CO.
in carotid sinuses
and aortic arch
are inhibited.
3 Impulses from baroreceptors
stimulate cardioacceleratory center
(and inhibit cardioinhibitory center)
and stimulate vasomotor center.
Figure 19.9 step 4b
Homeostasis: Blood pressure in normal range
1 Stimulus:
5
CO and R
return blood
pressure to
homeostatic
range.
4b Vasomotor
Blood pressure
(arterial blood
pressure falls
below normal
range).
fibers stimulate
vasoconstriction,
causing R
2 Baroreceptors
4a Sympathetic
impulses to heart
cause HR,
contractility, and
CO.
in carotid sinuses
and aortic arch
are inhibited.
3 Impulses from baroreceptors
stimulate cardioacceleratory center
(and inhibit cardioinhibitory center)
and stimulate vasomotor center.
Figure 19.9 step 5
Factors Determining Blood Pressure
Developmental Aspects of the
Cardiovascular System
 A simple “tube heart” develops in the
embryo and pumps by the fourth week
 The heart becomes a four-chambered
organ by the end of seven weeks
 Few structural changes occur after the
seventh week