World Library  
Flag as Inappropriate
Email this Article

Leg

Article Id: WHEBN0019166409
Reproduction Date:

Title: Leg  
Author: World Heritage Encyclopedia
Language: English
Subject: Terrestrial locomotion, Strepsiptera, Today's featured article/March 27, 2006, Worm, Human leg
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Leg

Diagram of an insect leg

A leg is a weight bearing and locomotive structure, usually having a columnar shape. During locomotion, legs function as "extensible struts".[1] The combination of movements at all joints can be modeled as a single, linear element capable of changing length and rotating about an omnidirectional "hip" joint.

As an anatomical animal structure it is used for locomotion. The distal end is often modified to distribute force (such as a foot). Most animals have an even number of legs.

As a component of furniture it is used for the economy of materials needed to provide the support for the useful surface, the table top or chair seat.

Terminology

  • Uniped: 1 leg, such as clams
  • Biped: 2 legs, such as humans and birds
  • Triped: 3 legs, which does not occur naturally in a healthy animal
  • Quadruped: 4 legs, such as dogs and horses.

Many taxa are characterized by the number of legs:

  • Tetrapods have four legs.
  • Arthropoda: 4, 6 (Insecta), 8, 12, or 14 legs. Some arthropods have more than a dozen legs; a few species possess over 100. Despite what their names might suggest, centipedes ("hundred feet") may have fewer than 20 or more than 300 legs, and millipedes ("thousand feet") have fewer than 1,000 legs, but up to 750.

Components

A leg is a structure of gross anatomy, meaning that it is large enough to be seen unaided. The components depend on the animal. In humans and other mammals, a leg includes the bones, muscles, tendons, ligaments, blood vessels, nerves, and skin. In insects, the leg includes most of these things, except that insects have an exoskeleton that replaces the function of both the bones and the skin.

Sometimes the end of the leg, or foot, is considered part of the leg; other times it is considered separate. Similarly, the hip joint or other place where the leg attaches to the main body may be considered separate or part of the leg.

Tetrapod legs

The leg of a wooly mammoth (reconstruction).

In tetrapod anatomy, leg is used to refer to the entire limb. In human medicine the precise definition refers[2][3][4] only to the segment between the knee and the ankle. This lower segment is also called the shank,[5][6] and the front (anterior) of the segment is called the shin or pretibia.

In bipedal tetrapods, the two lower limbs are referred to as the "legs" and the two upper limbs as "arms" or "wings" as the case may be.

Arthropod leg

Robotic leg

A robotic leg is moved by an actuator, which is a type of motor for moving or controlling a mechanism or system. It is operated by a source of energy, usually in the form of an electric current, hydraulic fluid pressure or pneumatic pressure, and converts that energy into some kind of motion.

Notes

  1. ^ "Studies in the Mechanics of the Tetrapod Skeleton". Biologists.org. Retrieved 21 September 2010. 
  2. ^ "Leg". Medical Subject Headings (MeSH). National Library of Medicine. Retrieved 2009-04-18. 
  3. ^ "Leg". Dorland's Medical Dictionary for Healthcare Consumers. Mercksource. Retrieved 2009-04-18. 
  4. ^ Merriam-Webster Dictionary leg
  5. ^ Kardong, Kenneth V. (2009). Vertebrates: Comparative anatomy, function, evolution (5th ed.). McGraw-Hill. p. 340.  
  6. ^ Merriam-Webster Dictionary shank
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.