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Related Concept Videos

Changes in the Appendicular Skeleton with Age01:09

Changes in the Appendicular Skeleton with Age

The upper and lower limb initially develops as a small bulge called a limb bud, which appears on the lateral side of the early embryo. The upper limb bud appears near the end of the fourth week of development, with the lower limb bud appearing shortly after.
Initially, the limb buds consist of a core of mesenchyme covered by a layer of ectoderm. The ectoderm at the end of the limb bud thickens to form a narrow crest called the apical ectodermal ridge. This ridge stimulates the underlying...
Development of the Limb Synovial Joints01:07

Development of the Limb Synovial Joints

Joints form during embryonic development in conjunction with the formation and growth of the associated bones. The embryonic tissue that gives rise to all bones, cartilage, and connective tissues of the body is called mesenchyme.
The mesenchymal stem cells differentiate into chondrocytes that form the hyaline cartilage, and later the cartilaginous model of the bone. This model further transforms into a bone. This process is known as endochondral ossification.
During development, the limbs...
Structural Classification of Joints01:20

Structural Classification of Joints

Joints, also known as articulations, are classified based on their structural characteristics, i.e., based on whether the articulating surfaces of the adjacent bones are directly connected by fibrous connective tissue or cartilage, or whether the articulating surfaces contact each other within a fluid-filled joint cavity. These differences serve to divide the joints of the body into three structural classifications.
A fibrous joint is where the adjacent bones are united by fibrous connective...
Introduction to Joints00:58

Introduction to Joints

The adult human body usually has 206 bones, and except for the hyoid bone in the neck, each bone is connected to at least one other bone. Joints are the location where bones come together. Many joints allow for movement between the bones. At these joints, the articulating surfaces of the adjacent bones can move smoothly against each other. However, the bones of other joints may be joined by connective tissue or cartilage. These joints are designed for stability and provide little or no movement.
Bones of the Lower Limb: Tibia and Fibula01:10

Bones of the Lower Limb: Tibia and Fibula

The tibia is the main weight-bearing bone of the lower leg. It is larger than the fibula with which it is paired. The tibia is also the second longest bone in the body and is located right below the skin. The proximal end of the tibia forms the medial and the lateral condyle, which articulates with the condyles of the femur to form the knee joint. Between the articulating surfaces is the irregular elevated area known as the intercondylar eminence that serves as the inferior attachment point for...
Functional Classification of Joints01:09

Functional Classification of Joints

Functional Classification of Joints
The functional classification of joints is determined by the amount of mobility between the adjacent bones. Joints are functionally classified as a synarthrosis or immobile joint, an amphiarthrosis or slightly moveable joint, or as a diarthrosis, a freely moveable joint. Fibrous and cartilaginous joints can be functionally classified as either synarthroses  or amphiarthroses, whereas all synovial joints are classified as diarthroses.
Synarthrosis
An immobile...

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Morphological integration and the evolution of knuckle-walking.

Scott A Williams1

  • 1Department of Anthropology, University of Illinois, 109 Davenport Hall, Urbana, IL 61801, USA. sawill@gmail.com

Journal of Human Evolution
|April 23, 2010
PubMed
Summary

Knuckle-walking in apes did not evolve as a coordinated functional complex. This finding challenges the idea that knuckle-walking could have easily evolved independently in chimpanzees and gorillas.

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Area of Science:

  • Primate evolution
  • Paleoanthropology
  • Comparative anatomy

Background:

  • The evolution of knuckle-walking in apes is central to understanding the origins of human bipedalism.
  • A key debate concerns whether knuckle-walking is homologous (shared ancestry) or homoplastic (independent evolution) in chimpanzees and gorillas.

Purpose of the Study:

  • To test hypotheses regarding the evolution of knuckle-walking by examining morphological integration in the hand.
  • To determine if knuckle-walking traits form a functionally integrated complex in chimpanzees and gorillas.

Main Methods:

  • Analysis of morphological integration patterns and magnitudes in the third manual ray and capitate.
  • Comparison of integration in knuckle-walking apes with non-knuckle-walking taxa.

Main Results:

  • Chimpanzees and gorillas do not exhibit high magnitudes of morphological integration for knuckle-walking.
  • No unique patterns of integration distinguish knuckle-walking apes from other primates.
  • Evidence for a distinct knuckle-walking functional complex was not found.

Conclusions:

  • The findings do not support the hypothesis of a knuckle-walking functional complex.
  • The results suggest that independent evolution of knuckle-walking in chimpanzees and gorillas is less likely than previously contended.
  • This has implications for analyzing primate traits and understanding the evolution of bipedalism.