Basic Concepts

During our first week in Veterinary Anatomy we covered a few basic concepts which we need to know as well as started learning about the musculoskeletal system. This post will cover the basic concepts which we need to know. 

Nomenclature
Firstly we need to know some anatomical nomenclature. Below is a diagram showing the terms that we'll use to describe the position of certain body parts.

The anatomical planes of a kangaroo.
source: :http://commons.wikimedia.org/wiki/File%3AAnatomical-directions-kangaroo.jpg
please see:http://creativecommons.org/licenses/by-sa/3.0/

Types of Joints

Classification: 

Joints can be grouped according to the amount of movement they allow:

• synarthrosis: no movement
• amphiarthrosis: limited movement
• diarthrosis: freely mobile

Joints can also be classified according to the type of tissue found between the bones:
Fibrous:

• suture: short fibrous seams: found in the skull
• syndemosis: thicker fibrous union - eg, like in between the distal tibia/fibula
• gomphosis: a peg-in-socket fibrous union. eg tooth

Cartilaginous:

• symphysis: fibrocartilage
• synchondrosis: fixed hyaline cartilage

Synovial: two hyaline cartilage surfaces seperated by a fluid filled space named the synovial cavity.


In addition, joints can be classified according to the shape of their surfaces and the range of movement possible:

• Spheroidal (ball and socket): eg the hip. a hemispherical head fits into a cup shaped cavity.
• Hinge: eg. elbow. the main movement is in only one plane. Ligaments and bony processes prevent movement in other planes. 
• Condylar: eg the knee. Two rounded processes of one bone fit into two depressions of another bone. The main movement is hinge but some rotation or sliding may occur. 
• Saddle: eg. the joint between the tip of the finger and the rest of the finger. ie the distal interphalangeal joint. This joint allows flexion and extension as well as abduction and adduction.
• Plane: eg between the bones in the wrist. ie the intercarpal joints. Little movement is possible because the surfaces are flat and the bones are held in place by tight ligaments. 
• Pivot: eg between the C1 and C2 (the first and second below the skull) vertebrae. Allows rotation of one bone about the other.

Joint Movements

Below is a very useful video which explains the various forms of joint movement. This video discusses human anatomy but many of these terms are also used in veterinary anatomy so it would be helpful to know them. 

Other Terms
  
Origin: The point of attachment of a muscle that remains relatively fixed during contration
Insertion: The point of attachment of a muscle to a bone or other body part that it moves.
Tendon:a band of tough fibrous tissue that connects a muscle to its bony attachment.
Aponeurosis: a flattened ribbon-shaped or sheet-like tendinous connective tissue that replaces tendon in muscles. It is flat and has a wide attachment area. Its job is to bind muscle together or to connect muscle to bone. 

An example of aponeurosis.
source: http://commons.wikimedia.org/wiki/File%3ALumbar_aponeurosis.jpg
please see: http://creativecommons.org/licenses/by-sa/3.0/ if you'd like to use this image

Tetrapod: an animal that has four feet, legs or leg-like appendages.
Cursorial: this refers to an animal that is adapted to or specialised for running
Girdle: an arch-like arrangement of bones that encircles a structure. eg the pelvic girdle. 
Plantigrade: a method of locomotion in which the animal walks on the phalanges, metacarpal and carpal bones. Humans use this method.
Digitigrade: a form of locomotion in which the animal walks only on its digits. Dogs use this form.
Unguligrade:the stance of an ungulate, which stands on its hooves.