Study of Skeleton of Vertebrates
Dr. Vidhin Kamble.
Department of Zoology.
Sangola College, Sangola.
Punyshlok Ahilyadevi Holkar Solapur University, Solapur
Study
of bone is called as osteology. The
bones from the framework of the body act as endoskeleton of the body that protect internal
delicate organs and gives support to the different parts of the body. The skeletal muscles are attached to bones.
Bones and skeletal muscles are helpful for the movement of body and locomotion.
Skeleton
of vertebrae is studied into two parts i.e.
1.
Axial skeleton
2.
Appendicular
skeleton.
Axial
skeleton includes
1.
Skull
2.
Vertebral
column.
The appendicular skeleton includes bones of Limb and girdles bones.
The
limbs includes 1.Bones of Forelimb and
Hind limb
2. Girdle
bones include Pectoral girdle and
Pelvic girdle
Axial skeleton includes
1.
Skull
2.
Vertebral
column.
Study of Skull
Based on
presence and absence of skull or cranium chordates are grouped into two groups i. e.
1. Acraniata
2. Craniate
Acraniata: The
organisms or animals that do not have cranium or skull are termed as Acraniata.
Ex. Subphylum –Cephalochordata. Amphioxus or Lancelets.
Craniata: An organism with a distal head or cranium or skull is termed as craniate. Ex. Fishes,
frogs, lizards, birds, primates (Human)
The skull or cranium is
also called a brain box or braincase. The
skull or cranium protects the brain and also supports the other soft tissues of
the head. The skull has a large aperture
on the posterior end called foramen magnum through which the brain joins with
the spinal cord. The part of the skull
which joins to the first vertebra of the vertebral column is called occipital condyle which is in the form of flat
bones.
Generally, the skull
is dividing into three parts:
1.
Chondrocranium – It is an anterior part of the axial skeletons that
encloses the special sense organs and form the skeletal components that covering
the brain. Condrocranium also called neurocranium covering lateral, ventral
and posterior parts of the brain and also covers nose and ear. The occipital condyle of
the skull is the part of chondrocranium articulate with 1st vertebra
of the vertebral column.
2.
Splanchnocranium – Also called visceral arches that support and move
the gills and contributed to the formation of the jaws in gnathostomes (Animals with
jaws). Generally, seven visceral arches are present during early embryonic
development.in fishes, it forms epibranchial cartilage and ceratobranchial
cartilage (fins of fishes). In higher vertebrates, splanchnocranium
is modified to form Jawa, hyoid apparatus, ear pharyngeal cartilage, etc.
3.
Dermatocranium – these are dermal
bones that cover the chondrocranium and contribute to the brain box or
cranium, jaws, and skeletal system of the mouth.
The Cranium or
Skull.
The cranium also is known as the neurocranium encloses and
protects the brain, meninges. The bones of the cranium are joined together with the
help of a fibrous joint called sutures. In living tetrapods, many original bones are
either disappeared or fused with each other to form several arrangements.
The cranium can be
subdivided into a roof also known as the calvarium, and a cranial base:
Calvarium: It consists of
1.
Frontal
2.
Occipital
3.
Two parietal bones.
Cranial base: It comprised of six bones
–
1.
Frontal
2.
Sphenoid
3.
Ethmoid
4.
Occipital
5.
Parietal
6.
Temporal bones.
These bones are much significant
as they offer an articulation point for the 1st cervical vertebra i.
e. atlas, as well as the facial bones and the mandible i.e. jawbones.
Skull or cranium
covers some important organs such as
1. The brain box or braincase or cranium
encloses the brain.
2. The olfactory capsules or nasal
containing the organs of smell.
3. The orbits of the skull for casing the eyes.
4. The auditory capsules for the ears.
5. The upper jaw bone fused with the ventral
margin of the skull.
6. The lower jaw articulated to the upper
jaw.
7. The hyoid apparatus, supporting the floor
of the mouth cavity.
Study of Axial
Skeleton: B). Vertebral Column
The presence of the vertebral column is the characteristic
of vertebrates. It is also called as the backbone
of the body. It consists of a series of separate bones
called vertebrae. It is situated on the dorsal side and extended from the base of skull to the base of the trunk. Each typical vertebra shows rod-like of
cylindrical centrum with many processes arise from centrum on the dorsal, ventral
side for articulation with each other and for attachment of muscles. Each
vertebra shows foramen or canal called vertebral canal through which the spinal
cord passes along its length.
1. Centrum
2. Neural arch
3. Neural spine
4. Neural canal
5. Haemal arch
6. Haemal spine
7. Haemal canal
8. Transverse process
9. Di-apophysis and paraphysis
10.
Prezygapophysis
11.
Postzygapophysis.
Centrum :
Each typical vertebra have a cylindrical axial piece
called as body or centra (Singular-Centrum). Many processes, ribs and muscles are attached to it. The centrum of
one vertebra connected with other forming columns which gives rigidity to the
vertebral column and support skull and trunk.
On the basis of the structure of centrum, there are
several types of vertebrae are as follows.
1. Pro- coelous
2. Amphi-coelous
3. Ophistho-coelous
4. Acoelous
5. Pro-platen
6. Ophisto-platen
7. Amphi-platen
8. Hetero-coelous
1. Pro-coelous vertebra: In this type of vertebra, centrum shows the presence of concavity on the anterior side and convex on the posterior side.
Ex. Typical
vertebrae of Frog, Reptiles
2. Ophistho-coelous vertebra: In
this type, the centrum shows concavity on the posterior side of vertebra and convex
on the anterior side. Ex. Salamanders, Parrots, and ungulates
3. Acoelous: in this type centrum is without concavity or convexity on both the side.
4. Amphi-coelous
vertebra: In this type, the vertebrae show the presence of concavity on both
the side of the vertebra. Ex. Fishes,
8th vertebra of the frog.
5. Platy-coelous:
In this type, the centrum is flat on the anterior side
and concave on the posterior side.
Ex. Some mammals.
6. Amphi-platyn: Such types o vertebrae are flat on both the side.
7. Ophishto-platene: Centrum is flat on the posterior side.
8. Amphi-platyn: In this type, the centrum is flat on both the side. Ex. Some mammals.
9. Hetero-coelous: In
this type, the centrum saddle-shaped or dissimilar on both the side. Such types of vertebrae are present in the cervical vertebrae of birds, helpful for movement.
10. Bi-convex: In this type, the convexity is present on both the
side.
Ex. 9th vertebra of the frog.
Neural arch: It is in the form of pair, arises on the dorsal side of the vertebra. The neural arches unite to form the neural canal. Neural arches enclose
the neural canal through which the spinal cord passes all along the length of the vertebral column. Ex. Higher animal.
Haemal arch: It is in the form of pair that arises on the ventral side of the vertebra. The haemal arches unit to from the haemal canal. Through which haemal spine passes. Ex. Caudal vertebrae of fishes.
In reptiles, it forms chevoron bone (Caudal vertebra)
Transverse processes – These are
elongated processes extended laterally from the neural arch of centrum.
Prezygapophysis and
postzygapophysis: Prezygapophysis present on the anterior side and postzygapophysis
present of the posterior side of the vertebra. The prezygapophysis and postzygapophysis
articulate with one another.
Kinds of vertebrae
In higher vertebrates, the vertebral column
constitutes of following vertebrae.
1. Atlas vertebra 1st
cervical vertebra connected to the skull.
2. Axis vertebra 2nd
cervical vertebra
3. Typical
vertebra
4. Thoracic vertebra
5. Sacral vertebra
6. Lumbar vertebra
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Dr. Vidhin Kamble
Department of Zoology.
Sangola College, Sangola
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