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Comparative Anatomy - ZOO 420 2(1+1)

Comparative Anatomy - ZOO 420 2(1+1). Zoology Department Dr. Elsayed Younis. The skeleton of Amphibians - Amphibians have a skeletal system that is structurally homologous to other tetrapods, though with a number of variations.

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Comparative Anatomy - ZOO 420 2(1+1)

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  1. Comparative Anatomy - ZOO 420 2(1+1) Zoology Department Dr. ElsayedYounis

  2. The skeleton of Amphibians - Amphibians have a skeletal system that is structurally homologous to other tetrapods, though with a number of variations. - The bones are hollow and lightweight. - The skeleton arefully ossified (except salamanders and caecilians) where, the skeleton isrelatively unossified. - The vertebrae interlock with each other by means of overlapping processes. - The ilium slopes forward and the body is held closer to the ground.

  3. The axial skeleton The skull :- is the skeleton of the head. It passes through three developmental stages ( membranocranium, chondro- cranium and osteocranium ) however, osteocranium is built up of bones and cartilages together. The skull is divided of two regions:- 1- neurocranium(cranium , sense capsules: olfactory or nasal capsules , optic capsules and audito or otic capsules) 2-splancocranium(mandibular arch, hyoid arch, and branchial arches)

  4. The vertebral column: It is short and formed of few vertebrae and a slender rod of bone called the urostyle. In case of salamanders it is formed of two distinct regions, the trunk and the tail. The vertebrae are all built up on the same plan, and resemble each other very closely. ( vertebra usually consists of centrum, neural arch, neural foramen, neural spine and transverse processes). Except the first vertebra or atlas and the ninth or sacral vertebra.

  5. The vertebrae are concave in front and convex behind, so that the vertebrae articulate with each other by staying the convexity of one vertebra in the concavity of the vertebra next behind. The sternum: consists of two portions( xiphisternum and xiphoid cartilage) and attached to the pectoral girdles. The appendicular skeleton pectoral girdle :- consists of two symmetrical halves, each half consists of ( coracoid, epicoracoid, clavicle, scapula and supra-scapula )

  6. pelvic girdle :- consists of two symmetrical halves, each half consists of three parts ( ilium, ischium and pubis ) Fore-limbs :- consists of two bones ( humerus, radius and ulna which called radio-ulna ) and ended by the hand (fore foot) which have 4 digits Hind-limbs: consists of three bones ( femur, tibia and fibula which called tibio-fibula and astragalus and calcaneum) and ended by the hind foot which have 5 digits

  7. The feet have adaptations for the way of life, with webbing between the toes for swimming, broad adhesive toe pads for climbing and keratinised tubercles on the hind feet for digging (frogs usually dig backwards into the soil). In most salamanders Some frogs use a wet or sticky substance on their feet to help them climb trees and cling to surfaces.

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