CARDIOVASCULAR
SYSTEM
The Blood Vessels
Chapter 19
Types of Blood Vessels
• Arteries=transport blood away from the heart
and typically carry oxygenated blood.
• Veins=transport blood toward the heart and
typically carry deoxygenated blood.
• Capillaries=microscopic blood vessels that
allow exchange between blood and tissues.
Blood Flow
Arteries
Capillaries
Veins
Layers of a Blood Vessel
• Tunica interna
(intima)= inner most
– Endothelium
• Tunica media=middle
– Vasoconstriction and
Vasodilation
• Tunica externa
(adventitia)= outermost
– Vasa vasorum
Arteries versus Veins
Blood Flow
Arteries
Capillaries
Veins
Arterial System
• Elastic arteries
• Muscular arteries
• Arterioles
• Arterial anastomoses
Major Arteries
Capillaries
• Characteristics
– Squamous epithelium
– Basal lamina
– Pericytes
• Types
– Continuous
– Fenestrated
– Sinusoidal
Capillary Beds
• Precapillary sphincter
• Metarteriolethoroughfare channels
• True capillaries
Venous System
• Venules
• Venous sinuses
• Veins
• Varicose Veins
• Venous Anastomoses
Major Veins
Blood Reservoirs
Vessel Comparison
PHYSIOLOGY OF
BLOOD VESSELS
Definition of Terms
• Resistance =the opposition to flow and is a
measure of the amount of friction blood
encounters as it passes through vessels.
• Blood Pressure =the force per unit area exerted
on a vessel wall by the blood contained within it
(expressed in mm Hg).
• Blood flow =the volume of blood flowing through
a vessel, an organ, or the entire circulation in a
given period.
RESISTANCE
Peripheral Resistance
• Blood viscosity
• Total blood vessel length
• Blood vessel diameter
BLOOD PRESSURE
Blood Pressure
• Arterial blood pressure
–
–
–
–
Systolic pressure
Diastolic pressure
Pulse pressure
Mean arteriole pressure
• Capillary blood pressure
• Venous blood pressure
Venous Blood Pressure
• Muscular pump
• Respiratory pump
Factors affecting Blood
Pressure
• Cardiac Output
– Increased CO = increased BP
– Decreased CO = decreased BP
• Peripheral Resistance
– Increased vasoconstriction = increased BP
– Increased vasodilation = decreased BP
• Blood Volume
– Increased blood volume = increased BP
– Decreased blood volume = decreased BP
Maintaining BP
(Short-term: neural)
• Vasomotor centers of
the medulla
• Vasomotor tone
• Baroreceptor-initiated
reflexes
• Chemoreceptorinitiated reflexes
• Hypothalamus and
cerebral cortex
Maintaining BP
(Short-term: hormones)
Maintaining BP
(Short-term: hormones & chemicals)
• Nitric Oxide
• Endothelin
• Inflammatory chemicals
• Alcohol and Nicotine???
Maintaining BP
(Long-term: renal regulation)
• Direct Renal
Regulation
– Blood volume
– Filtrate production
• Indirect Renal
Regulation
– Renin
– Angiotensin II
Factors That Increase MAP
MONITORING
CIRCULATORY HEALTH
Vital Signs
• Taking Pulse
• Measuring Blood pressure
• Respiratory rate
• Body temperature
Pulse Points
Blood Pressure:
Auscultatory Method
Blood Pressure Disorders
• Hypertension=140/90 mm Hg or higher
• Hypotension=100/80 mm Hg or lower
BLOOD FLOW
Blood Flow
• Through Tissues
–
–
–
–
Brain (13%)
Heart (4%)
Kidneys (20%)
Abdominal organs
(24%)
– Skeletal muscles (20%)
– All others (19%)
Velocity of Blood Flow
• Inversely related to
cross-sectional area of
the blood vessel
– Capillaries have low
velocity!
– Arteries have high
velocity!
– Veins have medium
velocity!
Regulation of Blood Flow
• Short-term autoregulation:
– Metabolic controls
– Myogenic controls
• Long-term autoregulation
– Angiogenesis
Regulation of Blood Flow
Relationship Between Blood
Flow, Pressure, and Resistance
Blood flow (F) is directly proportional to the
difference in blood pressure (P) between two
points in the circulation and inversely
proportional to the peripheral resistance (R) in
the systemic flow. Therefore:
F = DP
R
Blood Flow through Capillaries
and Capillary Dynamics
Capillary Transport Mechanisms
• Hydrostatic pressure (HP) causes filtration or reabsorption of
fluids
• Colloid osmotic pressure (OP) results from the presence of
large non-diffusible solutes or colloids
• Net filtration pressure (NFP) = (HPc – HPif) – (OPc-OPif)
Net Filtration Pressure
Circulatory Shock
• Hypovolemic shock
=extreme blood loss
• Vascular shock =blood
volume normal but poor
circulation due to extreme
vasodilation
• Cardiac shock =pump
failure
Blood Vessel Disorders
• Atherosclerosis=plaque
build up within vessel
• Aneurysm=ballooning of
blood vessel
• Phlebitis=inflammation
of a vein
Blood Vessels of the Body
Pages 722-744
END OF MATERIAL FOR
TEST I !!!