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== Venule ==
== Venule ==


[[File:Capillaries.jpg|thumb|right|Diagram showing venules and capillaries]]
[[File:Capillaries.jpg|thumb|right|Diagram of capillaries connecting to venules]]


A '''venule''' is a small blood vessel in the [[microcirculation]] that allows blood to return from the [[capillaries]] to the larger [[veins]]. Venules are an essential component of the [[circulatory system]], playing a critical role in the return of deoxygenated blood to the heart.
A '''venule''' is a small blood vessel in the [[microcirculation]] that allows deoxygenated blood to return from the [[capillary]] beds to the larger blood vessels called [[veins]]. Venules are an essential component of the [[circulatory system]], playing a crucial role in the return of blood to the heart.


== Structure ==
== Structure ==
Venules are formed when capillaries come together. They are typically 7 to 50 micrometers in diameter. The walls of venules are composed of three layers: the inner [[endothelium]], a middle layer of [[smooth muscle]], and an outer layer of connective tissue. The structure of venules is similar to that of veins, but they are smaller and have thinner walls.
 
Venules are formed when capillaries come together. They are typically 7 to 50 micrometers in diameter. The walls of venules are composed of three layers, similar to larger veins, but they are much thinner. These layers include:
 
* The [[tunica intima]], which is the innermost layer and consists of a thin layer of endothelial cells.
* The [[tunica media]], which is the middle layer and contains a small amount of smooth muscle.
* The [[tunica externa]] (or adventitia), which is the outermost layer and is made up of connective tissue.


== Function ==
== Function ==
Venules serve as conduits for blood returning to the heart. They collect blood from the capillary beds and transport it to the veins. Venules also play a role in the [[immune system]], as they are sites where [[white blood cells]] can exit the bloodstream to reach tissues.
 
[[File:Venule.jpg|thumb|left|Illustration of a venule]]
 
Venules serve as the site where blood from the capillaries is collected and transported back to the veins. They play a key role in the exchange of nutrients and waste products between the blood and tissues. The permeability of venules allows for the movement of white blood cells into tissues during inflammatory responses.


== Clinical significance ==
== Clinical significance ==
Venules can be involved in various medical conditions. For example, inflammation can cause venules to become more permeable, leading to [[edema]]. In some diseases, such as [[vasculitis]], venules can become inflamed and damaged.
 
Venules can be involved in various medical conditions. For example, inflammation can cause venules to become more permeable, leading to [[edema]]. In certain diseases, such as [[vasculitis]], the walls of venules can become inflamed, which can lead to tissue damage.


== Related pages ==
== Related pages ==
* [[Vein]]
* [[Vein]]
* [[Capillary]]
* [[Capillary]]
* [[Artery]]
* [[Arteriole]]
* [[Microcirculation]]
* [[Microcirculation]]
== References ==
* Guyton, Arthur C.; Hall, John E. (2006). ''Textbook of Medical Physiology''. Elsevier Saunders. ISBN 978-0-7216-0240-0.
* "Venule." Encyclopædia Britannica. Encyclopædia Britannica Online.
{{Circulatory system}}


[[Category:Cardiovascular system]]
[[Category:Cardiovascular system]]

Revision as of 04:01, 13 February 2025

Venule

Diagram of capillaries connecting to venules

A venule is a small blood vessel in the microcirculation that allows deoxygenated blood to return from the capillary beds to the larger blood vessels called veins. Venules are an essential component of the circulatory system, playing a crucial role in the return of blood to the heart.

Structure

Venules are formed when capillaries come together. They are typically 7 to 50 micrometers in diameter. The walls of venules are composed of three layers, similar to larger veins, but they are much thinner. These layers include:

  • The tunica intima, which is the innermost layer and consists of a thin layer of endothelial cells.
  • The tunica media, which is the middle layer and contains a small amount of smooth muscle.
  • The tunica externa (or adventitia), which is the outermost layer and is made up of connective tissue.

Function

File:Venule.jpg
Illustration of a venule

Venules serve as the site where blood from the capillaries is collected and transported back to the veins. They play a key role in the exchange of nutrients and waste products between the blood and tissues. The permeability of venules allows for the movement of white blood cells into tissues during inflammatory responses.

Clinical significance

Venules can be involved in various medical conditions. For example, inflammation can cause venules to become more permeable, leading to edema. In certain diseases, such as vasculitis, the walls of venules can become inflamed, which can lead to tissue damage.

Related pages