BIO 342
Comparative Vertebrate Anatomy
Lecture Notes 2 - Vertebrate Skeletal Systems



Bone:

Bone formation begins with a blastema (any aggregation of embryonic mesenchymal cells which will differentiate into tissue such as muscle, cartilage, or bone). These cells then develop into either FIBROBLASTS or OSTEOBLASTS. Fibroblasts form collagen; osteoblasts form bone cells. Together, these form MEMBRANE BONE (bone deposited directed in a blastema).
 

Intramembranous ossification is the process of membrane bone formation. This process give rise to:


Endochondral ossification is the process in which bone is deposited in pre-existing cartilage, & such bone is called REPLACEMENT BONE.


Source: http://training.seer.cancer.gov/module_anatomy/unit3_3_bone_growth.html



Skeletal elements:

Source: http://www.auburn.edu/academic/classes/zy/0301/Topic3b/Topic3b.html

Source: http://www.auburn.edu/academic/classes/zy/0301/Topic11/Topic11.html

Dermal bone of fishes:


Also check: http://courses.washington.edu/vertebra/453/photos/skin_photos/special_integument1.htm


1 = lamellar bone, 2 = spongy bone, 3 = dentin, 4 = enameloid, & 5 = fibrous plate (collagen)
Source: http://www.uta.edu/biology/restricted/3452int.htm




Tetrapods - retain dermal elements in the skull, jaws, & pectoral girdle


Somatic skeleton = axial skeleton (vertebral column, ribs, sternum, & skull) + appendicular skeleton

 Vertebral column:

  Vertebrae - consist of a centrum (or body), 1 or 2 arches, plus various processes






Vertebral arches:

Vertebral processes:

Transverse processes - most common type of process; extend laterally from the base of a neural arch or centrum & separate the epaxial & hypaxial muscles

Diapophyses & parapophyses - articulate with ribs

Prezygapophyses (cranial zygapophyses) & postzygapophyses (caudal zygapophyses) - articulate with one another & limit flexion & torsion of the vertebral column
 

Vertebral columns:

Diplospondyly = 2 centra and 2 sets of arches per body segment; occurs in some fish (including sharks)

Agnathans - only skeletal elements associated with the notochord are paired, lateral neural cartilages



Vertebral columns of tetrapods


EVOLUTION OF VERTEBRAE


Cross-hatched areas = hypocentrum; black areas = pleurocentrum.


Ribs - may be long or short, cartilaginous or bony; articulate medially with vertebrae & extend into the body wall


Sternum - strictly a tetrapod structure &, primarily, an amniote structure.


Useful link:

Skeletal system - the axial skeleton


Lecture Notes - Skeletal System II

Back to BIO 342 Syllabus