It is composed of nine vertebrae and a terminal rod-like structure called the urostyle. It is very much short due to the absence of tail. The vertebral column or backbone of frog encloses and protects the spinal cord. The hyoid lies in the floor of the pharynx, beneath the tongue. Posteriorly is a pair of strong bony posterior cornua or thyrohyals between which lies the glottis. In front are also two long slender anterior cornua of cartilage, they curve backwards and join the auditory capsules. It is produced in front into two alar processes and behind into two posterior lateral processes. At the extreme anterior end of Meckel’s cartilage is a small cartilage bone, the Mentomeckelian. It extends anteriorly up to Mentomeckelian bone and its posterior part is attached with the outer side of angulosplenial. Anterior outer surface of Meckel’s cartilage is covered by a small, flat, dogger-like dentary. Just anterior to the condyle is present a small dorsal projection, the coronary process. Its anterior end is tapering and postenor end possesses dorsally a condyle for the articulation with the quadrate cartilage. Each half has a core of Meckel’s cartilage covered over by an angulosplenial forming the inner and posterior portion of each ramus. The lower jaw has two rami joined in front by elastic ligament. Its handle joins with the quadrate cartilage. Its anterior limb or head is free and the short posterior limb articulates with the auditory capsule and prootic. It articulates anteriorly with the maxilla and palatine and on the inner side with the parasphenoid and auditory capsule, and posteriorly with the quadratojugal and quadrate cartilage.Īt the posterior dorsolateral end of cranium is the hammer-shaped bone, the squamosal. At the posterior lateral end of cranium is present a large 3-rayed or Y-shaped pterygoid. Ventral anterior to the orbit is a slender, rod-like palatine. The mandible articulates with the quadrate cartilage. Its broad posterior end unites with quadrate cartilage, which is a small thin rod forming the suspensorium. The posterior part of the upper jaw has a small quadratojugal. The upper jaw has two halves, each half has an anterior premaxilla followed by a long maxilla, both bear teeth. Visceral skeleton includes the upper and lower jaws, the hyoid apparatus, the columella auris and cartilages of larynx. They enclose the eyes and are not fused with the skull. They are associated with and surround the Jacobson’s organ. A pair of special bones called septomaxillary (ethmoids) form the boundary of nostrils. The olfactory capsules have two nasals dorsally and two vomers ventrally, the vomers bear vomerine teeth. The stapedial plate is a part of the columella derived from the hyomandibular. Each auditory capsule has a prootic in front, the capsule has an aperture, the fenestra ovalis into which a cartilaginous stapedial plate fits. The auditory capsule is fused on the outer side of each exoccipital. Each exoccipital bears at its posterior end a convexity, the occipital condyle which articulates with the concavity of the atlas vertebra. At the posterior end of the cranium is a foramen magnum surrounded by two exoccipitals.
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