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Section 4, Chapter 15.pptx

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Presentation Slides & Transcript

Presentation Slides & Transcript

Section 4, Chapter 15

A layer of smooth simple squamous epithelium

Secretes biochemicals with a wide variety of functions.

Basement membrane
Bed of connective tissue with elastic & collagenous fibers
Tunica Interna (inner)
Walls of the blood vessels – 3 Layers

Walls of the blood vessels – 3 Layers
Tunica Media (middle)
Smooth Muscles
Vasoconstriction – muscles contract, decreasing diameter of vessel

Vasodilation – muscles relax, allowing vessel diameter to increase

Elastic Connective tissue
Recoil of elastic fibers helps propel
blood through vessels

Tunica Externa (outer)
Fibrous Connective Tissue
Elastic and collagenous fibers

Attaches blood vessel to organs

Vasa Vasorum “vessels of the vessels”
Provide blood supply to walls of thicker arteries
Walls of the blood vessels – 3 Layers

Figure 15.27
An arteriovenous shunt provided by a metarteriole.
Arterioles are smaller divisions of arteries.

metarterioles – small arterioles that join capillaries

Arteriovenous shunt – connects an arteriole directly to a venule Shunt allows blood to bypass a capillary bed.

Figure 15.28 Substances are exchanged through openings (slits) separating endothelial cells.
Capillaries - smallest diameter blood vessels
Consists of a single layer of endothelial cells

Site of gas, nutrient, and waste exchange

Spaces between endothelia that facilitate diffusion across vessel wall

Figure 15.26 A precapillary sphincter at the base of a capillary.
Precapillary sphincters
Smooth muscles that regulate the flow of blood through a capillary

Closes a capillary bed when oxygen demand to an organ is low

Artificially colored electron micrograph depicts sinusoids throughout the liver.
large cavities within discontinuous capillaries

Allows a rapid exchange of nutrients, debris, proteins, and even cells.

located throughout the liver and spleen.

Continue from capillaries and merge to form veins

Convey blood from body back to the atria of heart

Veins follow a pathway roughly parallel to arteries

Vessel wall of veins has 3 layers (tunics) similar to arteries

Figure 15.31. Venous valves (a) open as blood moves towards the heart, but (b) close to prevent blood from moving backward away from the heart.
Veins have poorly developed tunica media
Thinner walls, and a larger luman than arteries

Tunica Interna of veins contain valves
Valves prevent blood from flowing backwards towards capillaries.

Veins act as blood reservoirs
Most blood (60-70%) is in the veins and venules.
Differences between veins and arteries

Figure 15.25 Blood vessels (a) the wall of an artery. (b) The wall of a vein. (c) cross section of an arteriole (bottom) and a venule (top).
Differences between veins and arteries

End of Section 4, Chapter 15