Ch 4. Vasculature Flashcards
Define Vasculature
All of the blood vessels in the body
What are the several types of blood vessels?
ARTERIES, ARTERIOLES, CAPILLARIES
VENULES, VEINS
What do Arteries/Veins do?
Arteries: Carry blood AWAY from the heart
Veins: Carry blood TO the heart
What are the smallest blood vessels in the body?
Capillaries! Its walls only consist of Endothelium and a Basement Membrane.
Fun fact: They are also more capillaries in the body than any other blood vessel and their walls are porous! About 10 billion of them exist in the body.
How many miles does blood travel throughout the body?
Altogether, blood travels through about 60,000 miles of blood vessels!
What do all blood vessels have?
What do all blood vessels have except for capillaries?
- At least an inner layer of Endothelium surrounded by a basement membrane
- Layers of Connective Tissue and Smooth Muscle that surround the basement membrane
Endothelium
Endothelium: A layer of epithelial cells that is closest to the lumen (or interior space) in a blood vessel
Because of its location, the endothelium is in direct contact with the blood that passes through the blood vessel!
The Endothelium of a typical capillary contains 2 types of pores:
- Intercellular Clefts: located between the endothelial cells of a capillary
- Fenestrations: run through individual endothelial cells of a capillary
Basement Membrane
Basement Membrane: A thin layer of extracellular material that surrounds and provides support to the endothelium and has pores
Smooth Muscle
Smooth Muscle: May be present toward the middle of the blood vessel wall.
The Smooth Muscle can contract or relax, thereby altering the diameter of the blood vessel.
Connective Tissue
(2 types of connective tissues may be present in the wall of a blood vessel
The 2 types of Connective Tissue that can be found:
- Elastic Connective Tissue
- Fibrous connective tissue.
Elastic: contains elastic fibers that allow the blood vessel to stretch and is typically found deeper within the wall of a blood vessel
Fibrous: contains collagen fibers that resist stretch, which prevents the blood vessel from over-stretching. This tissue usually forms the outer layer of a blood vessel.
How do blood vessels vary?
- They vary with the respect to the amount of Elastic and Fibrous connective tissues that they contain
What allows CAPILLARIES to serve as THE blood vessels that undergo gas, nutrient, and waste exchange with cells in the surrounding tissues?
FUNCTIONS OF BLOOD VESSELS ARE BELOW
It’s thin wall and pores.
Arteries, arterioles, venules, and veins are too thick AND lack pores so the gases, nutrients, and waste can’t move across the walls of these blood vessels.
Arteries
Arteries carry blood away from the heart, to arterioles
Arterioles
Arterioles deliver blood, to capillaries
Capillaries
Capillaries function as the “exchange vessels”.
They permit the exchange of gases, nutrients, and wastes between blood and the cells of the body. Transforming oxygenated blood into deoxygenated blood.
Fun fact: They are also more capillaries in the body than any other blood vessel and their walls are porous! About 10 billion of them exist in the body.
Venules
Venules drain capillary blood, and then deliver the blood to veins
Veins
Veins carry blood back to the heart
CAPILLARY EXCHANGE
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What can pass through a capillary’s walls?
Only relatively small molecules such as:
- Gases, Water, Ions, Glucose, Amino acids, & Hormones
Which substances typically diffuses across capillary walls directly through the LIPID BILAYER of endothelial cell plasma membranes?
Lipid-soluble substances (aka hydrophobic substances)
- Oxygen, Carbon Dioxide, and Steroid hormones
Which substances typically diffuses across capillary walls directly through the PORES?
Most small water-soluble (aka hydrophilic substances) -Ions, and Polar Molecules such as Glucose and Amino Acids
(in other words, the intercellular clefts and fenestrations of the capillary endothelium and pores of the basement membrane).
Fun fact
Recall that although water is a hydrophilic molecule, it is small and has NO charge.
What can move across the capillary wall via
transcytosis?
(which refers to endocytosis followed by exocytosis)
PROTEINS.
Fun Fact Notes from Prof
Any water that diffuses out of the blood goes into the interstitium
What is Lymph?
Extracellular fluid that is located within a lymphatic vessel
VENOUS VALVES, SKELETAL MUSCLE PUMP, AND VENOUS RETURN
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What’s venous return?
Venous return refers to the process by which veins return blood back to the heart.
How are veins able to return blood back to the heart despite having to go against gravity and lower blood pressure?
Venous Valves & the Skeletal Muscle Pump
Venous valves: consists of folds of the endothelium of the vein that function to prevent back-flow of blood.
The Skeletal Muscle Pump: refers to contractions of skeletal muscles surrounding veins that help push blood up the veins.
Fun Fact: If you stand for a long period of time, you should periodically contract the muscles in your legs, in order to make sure that blood goes back to the heart.
OTHERWISE, blood can pool in the veins & you might pass out since the heart isn’t pumping enough blood to the brain.
ALTERATION OF BLOOD VESSEL DIAMETER
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Which blood vessels can change their diameters (Vasoconstrict or Vasodilate) by contracting or relaxing the smooth muscle in their walls?
Arteries, Arterioles, Venules, and Veins
note capillaries do NOT constrict or dilate because they do NOT have smooth muscle!
Vasoconstriction DETAILS
The Smooth Muscle within its wall CONTRACTS.
- Consequently, the blood vessel lumen becomes SMALLER which causes a decrease in blood flow and an increase in blood pressure.
NOTE: blood pressure is pressure that occurs when blood interacts with the wall of a blood vessel. So, if there is more interaction between blood and the blood vessel wall, blood pressure increases.
Vasodilation DETAILS
The Smooth Muscle within its walls RELAXES.
- Consequently, the blood vessel lumen becomes WIDER and larger. Vasodilation causes an increase in blood flow and a decrease in blood pressure (because there’s more room between the blood and blood wall)
BLOOD DISTRIBUTION
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What is the average blood volume when the body is normally hydrated?
About 5 liters
Blood Distribution (blood volume) DETAILS
Heart: 7% Systemic Arteries and Arterioles: 13% Systemic Capillaries: 7% Systemic Veins and Venules: 64% Pulmonary Blood Vessels: 9%
What is deemed the “Blood Reservoirs” of the body?
Systemic Veins and Venules