Chapter 42.3 Flashcards
A vessel’s cavity
the central lumen
central lumen
a vessel’s cavity
The epithelial layer that lines blood vessels
endothelium
endothelium
the epithelial later that lines blood vessels
The endothelium is…
smooth and minimizes resistance
Capillaries
- are only slightly wider than a red blood cell
2. have thin walls, the endothelium plus its basal lamina
why do capillaries have the endothelium and its basal lamina
to facilitate the exchange of materials
What do arteries and veins have?
endothelium, smooth muscle, and connective tissue
How do arteries differ from veins?
they have thicker walls to accommodate the high pressure of blood pumped from the heart
how do veins differ from arteries?
they have thinner-walls, blood flows back to the heart mainly as a result of muscle action
What affects blood flow and blood pressure?
physical laws governing movement of fluids through pipes
Where is the velocity of blood flow the slowest
capillary beds
why is the velocity of blood flow the slowest in capillary beds
the high resistance and large total cross-sectional area
Why is blood flow in the capillaries necessarily slow?
for exchange of materials
Where does blood flow?
from areas of high pressure to areas of lower pressure
What is blood pressure
the pressure that blood exerts in all directions, including against the walls of blood vessels
What does the recoil of elastic arterial walls play a role in
maintaining blood pressure
What dissipates much of the pressure
the resistance to blood flow in the narrow diameters of tiny capillaries and arterioles
Systolic pressure
the pressure in the arteries during ventricular systole
the pressure in the arteries during ventricular systole
systolic pressure
what is the highest pressure in the arteries called
systolic pressure
diastolic pressure
the pressure in the arteries during diastole
the pressure in the arteries during diastole
diastolic pressure
is lower than systolic pressure
diastolic pressure
a pulse
is the rhythmic bulging of artery walls with each heartbeat
the rhythmic bulging of artery walls with each heartbeat
a pulse
How do homeostatic mechanisms regulate arterial blood pressure
by altering the diameter of arterioles
vasoconstriction
the contraction of smooth muscle in arteriole walls
the contraction of smooth muscle in arteriole walls
vasoconstriction
increases blood pressure
vasoconstriction
vasodilation
the relaxation of smooth muscles in the arterioles
the relaxation of smooth muscles in the arterioles
vasodilation
causes blood pressure to fall
vasodilation
a major inducer of vasodilation
nitric oxide
a strong inducer of vasoconstriction
the peptide endothelin
What are vasoconstriction and vasodilation often coupled to
changes in cardiac output that affect blood pressure
What is blood pressure generally measured for
an artery in the arm at the same height as the heart
What has a significant effect on blood pressure
gravity
What is fainting caused by
inadequate blood flow to the head
what do animals with long necks require
a very high systolic pressure to pump blood a great distance against gravity
What is blood moved through the veins by
smooth muscle contraction, skeletal muscle contraction, and expansion of the vena cava with inhalation
what do one-way valves in veins prevent
backflow of blood
What percent of the body’s capillaries does blood flow through at any given time
5-10%
how filled are capillaries in major organs usually
to capacity
What two mechanisms regulate distribution of blood in capillary beds
- constriction/dilation of arterioles that supply capillary beds
- precapillary sphincters
precapillary sphincters
control the flow of blood between arterioles and venules
what is blood flow regulated by
nerve impulses, hormones, and other chemicals
Where does the exchange of substances between the blood and interstitial fluid take place
across the thin endothelial walls of the capillaries
What does the difference between blood pressure and osmotic pressure drive
fluids out of capillaries at the arteriole end and into capillaries at the venule end
Why can most blood cells and blood proteines not pass through the endothelium
they are too large
Lymphatic system
returns fluids that leaks out from the capillary beds
returns fluids that leaks out from the capillary beds
lymphatic system
fluid lost by capillaries
lymph
lymph
fluid lost by capillaries
What does the lymphatic system drain into
veins in the neck
What do valves in lymph vessels do
prevent the backflow of fluid
edema
swelling caused by disruptions in the flow of lymph
swelling caused by disruptions in the flow of lymph
edema
lymph nodes
organs that filter lymph and play an important role in the body’s defense
organs that filter lymph and play an important role in the body’s defense
lymph nodes
What occurs when the body is fighting an infection
lymph nodes become swollen and tender
