Test 1 Flashcards
circulatory system
- move blood around the body
- Delivers oxygen (O2)
- Removes carbon dioxide (CO2) and other waste products from cells
- Circulates/delivers nutrients (glucose and others) and hormones
what are the three types of the blood vessel?
Arteries:
Veins:
Capillaries:
Arteries:
blood flows AWAY from heart
Divides into smaller parts
Veins:
blood flows TOWARDS heart
Parts join and merge
Capillaries:
The microscopic exchange vessels (between arterioles and venules)
what are the three layers of blood vessel
Tunica intima
Tunica media=
Tunica externa
Tunica intima
is the innermost layer, always contains epithelium (reminder: one of the 4 tissue types) and sometimes contains elastic tissue.
-The tunica intima lines the lumen (hollow space/inside) of all blood vessels.
Tunica media (middle)
- mostly made of layers of smooth muscle tissue
- Tunica media contributes to blood pressure and blood flow; drugs, hormones, etc. can cause vasodilatation/vasoconstriction.
Tunica externa
is the outermost layer of blood vessels
- Tunica externa is primarily made of connective tissue (collagen fibers) that protects and anchors blood vessels.
Vasodilation
lumen diameter is increased (dilated)
Vasoconstriction
lumen diameter is reduced (constricted)
vasa vasorum
which nourish outer layers of the vessels. Tiny blood vessels found in the outer layer of large blood vessels like the aorta, needed to diffuse O2 and nutrients into outer layers of blood vessels
what are the three types of arteries
Elastic arteries
Muscular arteries
Arterioles
Elastic arteries
(aorta+ major branches)
Largest arteries; thick-walled
They are the nearest arteries to the heart
Contains high levels of elastic tissue (elastic tissue in all 3 tunics in elastic arteries)
Muscular arteries
Deliver blood to organs
Contain high levels of smooth muscle (thick tunica media)
Smaller and less stretchy than elastic arteries
Provide much of the body’s vasoconstriction/vasodilation
Arterioles
Smallest arteries
Arteriole diameter determines blood flow to the capillaries
what type of tunica are capillaries made of?
Capillaries are made only of tunica intima.
What are the three types of capillary?
There are three types of capillaries:
Continuous
Fenestrated (“window”)
Sinusoidal (“Curved”)
Continuous
the most common type of capillary Uninterrupted lining (no pores, endothelial cells closely attached) Found throughout the body
Fenestrated (“window”)
Oval pores in the endothelial cells allow fluids and small molecules to move through cells
Located in high absorption/filtration regions (i.e. kidney, small intestine)
Sinusoidal (“Curved”)
Large pores in the endothelial cells; large spaces and clefts between endothelial cells
Allows passage of large molecules (found in the liver, bone marrow, spleen)
Blood flows slowly through these vessels
capillary bed
interweaving networks of capilaries
vascular shunt
the central part of the capillary bed that provides the blood to the capillary bed
how many capillaries are in the average capillary bed?
10-100
Capillary sphincters
are cuffs of smooth muscle that surround the base of the capillary where it attaches to the vascular shunt.
The capillary sphincters control blood flow through capillary bed, by opening to allow increased blood flow, or contracting to shut off most of the blood flow.
two types of vein
Venules Veins
Venules
are the smallest veins
-No elastic tissue, very little muscle
Veins
- Veins (that are not venules) contain very little elastic tissue, and small to moderate amounts of muscle.
- Veins are a low-pressure environment (compared to arteries)
- Veins have thin walls and large lumens compared to arteries.
- Veins contain one-way valves that prevent blood from flowing backwards in veins.
how do veins push blood back to the heart?
The “muscular pump” that acts on veins occurs when skeletal muscles near veins contract, squeezing the vein, and pushing blood toward the heart. The unidirectional valves in veins will open to allow the blood to move towards the heart, and close before blood can backflow.
what is blood pressure?
defined at the force per unit area exerted on the wall of a vessel by its contained blood (measured as mm of Hg).
what are the three things that influence blood pressure?
Viscosity
Vessel length.
Vessel diameter.
What is the most important thing in blood pressure
Vessel diameter
Systolic Pressure
– Pressure from ventricular contraction; how much pressure your blood exerts against your artery walls when the heart beats
Diastolic Pressure
Pressure from ventricular relaxation; how much pressure your blood exerts against your artery walls while the heart is resting between beats.
What type of blood pressure is desired in capillaries?
Low, for the capillaries are extremely weak and a high blood pressure would damage them beyond compare.
distensible
How much the arteries can be stretched
Venous blood pressure
is lower than capillary blood pressure.
how are nutrients exchanged in the capilaries?
Capillaries exchange molecules is several ways: simple diffusion through epithelial cells, movement through the clefts between cells, or movement through fenestrations (pores).