Blood Vessels Flashcards
1
Q
Name the 5 main types of blood vessels. What are their functions?
A
-
Arteries:
- Carry blood away from the heart to the tissues and organs
-
Arterioles:
- Smaller arteries that connect to capillaries
-
Capillaries
- Site of substance exchange between the blood and body tissues
-
Venules
- Connect capillaries to larger veins
-
Veins
- Convey blood from the tissue back to the heart
2
Q
What are the 3 layers of blood vessel wall? Name important components of each layer.
A
-
Tunica interna (aka tunica intima) - innermost layer, contains the
- Endothelium
- Basement Membrane
- Internal elastic lamia
-
Tunica media – middle layer, smooth muscles and elastic fibers
- Smooth muscle contraction/relaxation constricts and dilates
- Elastic allows for stretch and recoil
- Regulates the diameter of the lumen
-
Tunica externa – outermost layer, adjacent to surrounding tissue
- Elastic and collagen
- Nerves
- Vaso Vasorum
3
Q
What is endothelium? What are its functions?
A
- The innermost layer of the Tunica Interna, directly in contact with the blood and is continuous with the endocardial lining of the heart
- Secrete chemical mediators that influence the contractile state of vessel’s overlying smooth muscle
4
Q
Define vasa vasorum. Where is it located?
A
- Vaso Vasorum – small blood vessels that supply blood to the tissue of the vessel wall
- Located in the Tunica Externa – the outermost layer of the vessel wall
5
Q
What are the structural characteristics of elastic arteries? What are their functions?
A
- AKA Conducting Arteries
- Largest arteries with large diameter with relatively thin walls
- They have a lot of elastic fibers, allowing them to stretch and accommodate the surge of blood and store mechanical energy as a pressure reservoir to help continue to propel blood when the ventricles relax
- (Includes: aorta, pulmonary trunk, brachiocephalic, common carotid, subclavian, common iliac)
6
Q
What are the structural characteristics of muscular arteries? What are their functions?
A
- AKA Distributing Arteries
- Medium-sized, more muscle than elastic in the tunica media, thick walls
- Direct the blood flow through vasoconstriction and vasodilation
7
Q
Define collateral circulation. What is its function? Define end arteries.
A
- Collateral circulation – alternate route of blood flow to a body through an anastomosis
- If one vessel becomes blocked, circulation is not stopped
- Arteries that do not anastomose are known as end arteries – obstructing them can result in necrosis
8
Q
What is the function of arteriole?
Why are they called resistance vessels?
Define metarteriole.
What is the function of precapillary sphincter?
A
- Deliver blood from arteries into capillaries
- They create resistance through vasoconstriction and vasodilation, which
- The terminal end of the arterioles which form branches into the capillary bed
- Control the flow of blood through a capillary bed (or thoroughfare channel) Open and close to allow blood to flow
9
Q
What are the structure and function of a capillary?
A
- Smallest of the blood vessels with no tunica media or externa, just a single later of cells and a basement membrane
- Function is to make a surface that allows exchange of nutrients and waste between blood and tissue cells
10
Q
Define microcirculation.
A
- The flow of blood from a metarteriole through capillaries into post capillary venules
11
Q
What is a capillary bed?
A
- A network of 10-100 capillaries that arises from a single metarteriole
12
Q
What structure is used to control the flow of blood through a capillary bed?
A
- Precapillary sphincter
13
Q
What are the 3 types of capillaries?
What are the structure and locations of each type?
A
- Continuous
- Continuous tube of endothelial cell plasma membranes, found in brain, skeletal and smooth muscle, connective tissue, lungs
- Fenestrated
- Many small pores, found in kidneys, small intestine, endocrine glands
- Sinusoid
- Wider, large intracellular clefts and large fenestrations to allow proteins/blood cells to enter blood stream, found in liver, red bone marrow, spleen, anterior pituitary and parathyroid glands
14
Q
Define a portal vein.
What are the 2 portal veins present in the body?
A
- Where blood passes from one capillary network to another instead of back into a venule
- Hepatic / Liver
- Hypophyseal Portal System (Pituitary)
15
Q
What are the functions of venules?
A
- Move blood from capillaries back to veins (also still very porous and exchange nutrients/waste – confirm from book)
16
Q
What is the characteristic of vein wall?
A
- Have a much thinner tunica interna and media than arteries and thicker tuna externa – less elastic and less smooth muscles than arteries
17
Q
Define valve of a vein. What is its function?
A
- Folds on the tunica interna that form flaplike cusps and aid in venous return, preventing backflow
18
Q
Define venous sinuses. Where are they located?
A
- Vein with a thin endothelial wall that has no smooth muscle to alter its diameter
- Found in dura sinus (brain to heart), Coronary sinus (in the heart)
19
Q
. What is the percentage of blood distribution in the circulatory system at rest?
A
- 64% is in the systemic veins and venules as blood reservoir
- 36% is in circulation
- 13% in Systemic Arteries and Arterioles
- 7% in Heart
- 7% in Systemic Capillaries
- 9% in Pulmonary vessels
20
Q
Which blood vessels are blood reservoirs?
A
- Systemic veins and venules
21
Q
What are the three mechanisms of capillary exchange? What are the substances exchanged by each process?
A
- Diffusion
- Oxygen, Co2, Glucose, Amino Acids, Some hormones diffuse across lipid bilayer
- Transcytosis
- Large lipid-insoluble molecules (like insulin) cross walls in vesicles
- Bulk Flow
- Large numbers of ions, molecules particles (area of higher pressure to lower pressure
22
Q
Define bulk flow. What are the different outward and inward pressures controlling the bulk flow?
A
- Process of:
-
Filtration is pressure-driven moment of fluid and solutes from blood capillaries into interstitial fluid
- Blood hydrostatic pressure (BHP) – pressure generated by the pumping of the heart
- Interstitial fluid osmotic pressure (IFOP)
-
Reabsorption is pressure-driven movement of fluid and solutes from interstitial fluid into blood capillaries
- Interstitial fluid hydrostatic pressure (IFHP)
- Blood colloid osmotic pressure (BCOP)
-
Filtration is pressure-driven moment of fluid and solutes from blood capillaries into interstitial fluid
- Balance of these pressures is net filtration pressure – determines whether the volumes of blood and interstitial fluid remain steady or change
23
Q
What percentage of blood is filtered by the cap after Filteration/Reabsorption?
A
- About 85% of the filtered fluid is returned to the capillary
- Escaping (left-over) fluid and plasma proteins are collected by lymphatic capillaries
24
Q
Define vascular resistance? What are the factors on which vascular resistance depends?
A
Opposition of blood flow due to the friction between blood and the walls of the blood vessels
- Size of the blood vessel lumen
- Blood Viscosity / thickness
- Total blood vessel length
25
Define Blood Pressure
Blood pressure (BP) is the pressure exerted by blood on the walls of a blood vessel; in clinical use, BP refers to pressure in arteries.
26
Define systolic, diastolic, and pulse pressures?
* **Systolic BP** is the higher pressure measured during left ventricular systole when the aortic valve is open. (Normally around 120)
* **Diastolic BP** is the lower pressure measured during left ventricular diastole when the valve is closed (Normally around 80)
* **Pulse pressure** is the difference between systolic and diastolic pressures. It normally is about 40 mm Hg
27
How is mean arterial pressure is calculated?
MAP is roughly 1/3 of the way between the diastolic and systolic BP.
MAP = 1/3 (systolic BP – diastolic BP) + diastolic BP
(In our 'normal' example this is 93.3mm)
28
What are the relations to Vascular Resistance (R) for size of Blood vessel lumen, Blood viscosity, and Blood Vessel length?
**Size of the blood vessel lumen**
* The smaller the lumen, the greater is the resistance, and vice versa
**Blood viscosity**
* The higher is the blood’s viscosity, the higher is the resistance, and vice versa
**Total blood vessel length**
* Resistance is directly proportional to the length of the blood vessel
29
What is total peripheral resistance?
**Systemic vascular resistance** (also known as total peripheral resistance) refers to all of the vascular resistances offered by systemic blood vessels; most resistance is in arterioles, capillaries, and venules due to their small diameters.
30
# Define venous return.
**What are the mechanisms which assist venous return?**
The volume of blood flowing back to the heart through the systemic veins – due to pressure generated by contractions of the hearts left ventricle
* **Valves -** prevent backflow, especially in limbs/against gravity
* **Skeletal Muscle Pump -** Contraction of leg muscles compresses the vein and pushes blood through the proximal valve. At the same time, the distal valve in the uncompressed segment closes as some blood is pushed against it, Relaxation of the leg muscles causes proximal valve to close and distal valve to open
* **Respiratory Pump -** Decreased thoracic pressure and increased abdominal pressure during inhalation, moves blood into thoracic veins and the right atrium
31
# Define blood flow and the relation of blood flow to the cross-sectional area of blood vessels?
The volume of blood that flows through a tissue in a given period of time
Inversely related to the cross-sectional area of blood vessels. The larger the cross section, the lower the blood flow.
32
**What is the force which generates blood pressure? What are the factors which determine the blood pressure?**
The contraction of the ventricles
cardiac output, blood volume, viscosity, resistance, and elasticity of arteries.
