Anatomy of the Circulatory System: Structure and Components of Blood Vessels, Exams of Biology

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CIRCULATORY SYSTEM I.

How do vampires like to travel?

By blood vessel!

I. There are two major components of the circulatory system.

1. heart
   2. arteries
   3. arterioles
2. capillaries
   5. venules
   6. veins A. The cardiovascular system:

II. General cardiovascular

circulation

A. Two major components

1. arterial system
   2. venous system http://www.accessexcellence.org/AE/AEC/CC/art_vein.gif

B. Together these two systems form two major circulatory loops http://gened.emc.maricopa.edu/bio/bio181/BIOBK/ BioBookcircSYS.html#Vertebrate Cardiovascular Syste

1. systemic loop
2. pulmonary loop

III. Structure of vessels I - General structure of larger blood

vessels.

A. Blood vessels larger than capillaries are encircled by 2 or more of the following tissue layers. In most instances, all 3 layers are present.

• tunica intima
• tunica media
• tunica adventitia

http://www.medsch.wisc.edu/anatomy/histo/res/l/cv/cv21.jpg

c. In arteries, the intima often appears scalloped (wrinkled) in sections due to contraction of the smooth muscle cells present in the subendothelial layer.

1. tunica intima http://meded.ucsd.edu/hist-img-bank/chapter_3/Slide_58_artery/pages/a.2.58.2.1.htm

2. tunica media ("media")

III. Structure of vessels I - General structure of larger blood

vessels.

a. this layer encircles the intima b. consists of circumferential smooth muscle with extracellular matrix secreted by the muscle cells

• collagen,
• elastin,
• various proteoglycans c. in muscular arteries a layer of elastin called the internal elastic lamina separates the intima and media http://medic.med.uth.tmc.edu/edprog/images/Cv1.jpg

3. tunica adventitia (or "adventitia")

III. Structure of vessels I -

General structure of larger

blood vessels.

a. connective tissue layer with high content of collagen and elastic fibers in extracellular matrix between fibroblasts b. this layer gradually becomes continuous with the connective tissue of the organ/tissue the vessel is in http://medic.med.uth.tmc.edu/edprog/images/Cv1.jpg http://128.218.123.161/IDS_100/vessels/fig2.html

http://www.finchcms.edu/anatomy/histology/ organology/circulatory/o_c_10.html http://medic.med.uth.tmc.edu/edprog/images/Cv1.jpg c. in larger vessels a network of small blood vessels called the vasa vasorum is present in the adventitia. Branches of these vessels (arterioles, capillaries) venules) will extend into the tunica adventitia and the outer half of the media.

• these provide nutrients to cells in the adventitia and media.

V. Structure of vessels III - Arteries

A. Large elastic arteries (e.g. descending aorta and large branches thereof)

3. lots of elastin in tunica media that gives these vessels yellow color in life
4. very thick tunica intima consisting of the endothelium with a relatively thick sub-endothelial layer of loose connective tissue. An internal elastic lamina may or may not be present. http://www.lab.anhb.uwa.edu.au/mb140/
5. sub-endothelial basal lamina of intima may not be present

4. media consists of concentrically arranged
   • sheets of elastin fibers
   • smooth muscle cells
   • collagen fibers. The number and thickness of the elastic layers increases with age
   5. tunica adventitia is usually relatively thin with a vasa vasorum (network of blood vessels) http://www.lab.anhb.uwa.edu.au/mb140/ A. Large elastic arteries (e.g. decending aorta and large branches thereof)

5. larger muscular arteries may have an external elastic lamina.
6. adventitia is well developed and may be thinner than media.
7. spasmodic contraction of the media smooth muscle helps prevent hemorrhaging during injury.
8. the tunica media is the major identifying characteristic. It consists of a thick smooth muscular layer with as many as 40 layers of smooth muscle encircling the artery. B. Muscular arteries http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Vascular/ Vascular.htm

C. Arterioles

1. arterioles are small arteries, 0.04 - 0.4 mm in diameter
2. tunica intima consists of the endothelium - no sub- endothelial layer of loose connective tissue
3. media is muscular and composed of 1-3 layers of smooth muscle
4. adventitia is fairly prominent http://www.finchcms.edu/anatomy/histology/ organology/circulatory/images/ff518.jpg