GENBIOLAB2 - 5 and 6 sads

• The frog is divided into two major layers: the outer epidermis and the inner dermis
• The epidermis is made up of a stratified epitheliumwith a thin, hardened surface layer of dead squamouscells that is constantly removed when the toad sheds itsskin. The inner layer consists of living cuboidal tocolumnar cells that continuously divide to replace theshed off layer of the skin. The color of the skin is due inlarge part to the row of black pigment-containing cellscalled melanophores found at the junction of theepidermis and dermis.
• The toad exhibits bilateral symmetry – that is, it can be differentiated into two mirrored portions, namely, right and left halves. The regions of the body include: (a) anterior– head end; (b) posterior– tail end; (c) dorsal– back side; and (d) ventral– belly side.
• The body of the toad is divided into three planes according to how thebody is divided: (a) frontal– into dorsal and ventral sections; (b) sagittal(longitudinal)- into right and left sections; (c) transverse (cross)– into anterior and posterior sections
• With reference to location relative to the center of the body, the following terms are used: (a) medial– near the middle; (b) lateral– to the sides; (c) proximal– part of a structure that is nearer the origin; and (d) distal– part farther from the origin
• Axial region


  Composed of the head and the trunk
• Head and trunk


  • Broadly joined by a very short neck
  • Restricting movement of the head
• Snout


  The most anterior portion of the head
• External nares


  • A pair of openings at the tip of the snout
• Eyes

  • Bulging, at the dorsolateral portion of the head, posterior to the external nares
• Eyes

  • Have upper and lower eyelids
  • Have a third, transparent nictitating membrane, which keeps the eyes moist when underwater
• Tympanic membrane (eardrum)


  An ovoid region of tightly drawn skin, covering the auditory canal, posterolateral to the eye
• The frog and toad have no external ear, only the middle and internal ears
• Parotoid gland


  • A large swelling behind the tympanic membrane at each side of the head
  • A large aggregate of poison glands
• Cloacal aperture


  At the most posterior end of the trunk, on the dorsal side
• The appendicular region is made up of the forelimbs (anterior pair) and the hindlimbs (posterior pair). The paired appendages vary in form and function. The forelimbs are short and each consists of four (4) main parts: upper arm, forearm, wrist/carpus, and hand/manus which bear four digits and a rudimentary thumb called prepollex. The hindlimbs are long and each consists of the thigh, shank, ankle/tarsus, and foot/pes. Each foot bears five digits and a sixth rudimentary toe called prehallux. Note the webbed toes.
• Male Frog -The skin on the ventral side of the head near the angles of the jaw has a distinct dark pigmentation due to concentration of pigments. The thumb pads of the inner fingers are enlarged or “swollen”. These are used during amplexus or false copulation. Sexually mature male toads/frogs are generally smaller than the females
• Female Frog - The pigments are diffused; hence,there is no distinct dark pigmentation at this area. The thumb pads of the inner fingers are not “swollen”. Sexually mature female toads/frogsare relatively bigger than the males.
• The skeleton is an essential part of the body ofevery vertebrate animal. It has several functions: (1)serves as support or framework for the softer parts of thebody, (2) provides a firm surface for the attachment ofmuscles used in movement and locomotion, (3) suppliescalcium to the blood, and (4) important site in theformation of blood cells.
• There are two types of skeleton: the exoskeletonand the endoskeleton. The exoskeleton of vertebratesconsists of the hardened bony or horny structures thatdevelop in the skin and provides external protection tothe animal. These structures are poorly developed infrogs/toads. The skeleton of the frog/toad is almostentirely endoskeletal in nature and consists almostentirely of bone and cartilage.
• Skeletal muscles and skeleton are often

  considered together as a functional unit that permit body

  movements and locomotion. Muscles are attached to the

  bones by a connective tissue called tendon. A broad,

  flat and sheet-like tendon is called aponeurosis.
• Skeletal muscles often have two points ofattachment. The part in between is sometimes referredto as the belly of the muscle. Locating the attachmentscan facilitate identification of a muscle. Other clues toidentify muscle include the shape and relative size ofthe muscles, direction of the muscle fibers, as well asthe action of the muscles. It is worthwhile to note thatthese factors mentioned are also the bases for namingmuscles.
• Axial endoskeleton– composed of all endoskeletal structures located at the centeror axis of the body.

  1. Skull
  2. Visceral skeleton
  3. Vertebral column and ribs (it lacks true ribs)
  4. Sternum
• Appendicular endoskeleton– consists of all endoskeletal structures located laterally or in the region of the extremities or appendages.

  1. Girdles
  2. Pectoral girdle
  3. Pelvic girdle
  4. Bones of the limbs
  5. Anterior limbs or forelimbs
  6. Posterior limbs or hindlimbs
• The skull of the frog is flattened dorsoventrally. It is wider posteriorly andnarrower anteriorly. It encloses the brain and the sense organs. It includes the cranium or braincase and the visceral skeleton (jaws, hyoid apparatus, and bones of the ears).
• Nasal Bones


  Triangular-shaped bones on the dorsal surface of the skull behind the nares
• Fontoparietals


  Two long, slender, flat bones, just posterior to the nasal bones, covers most part of the brain
• Foramen Magnum


  Posterior end of the skull, this is where the spinal chord passes
• Exoccipital


  Surrounds the posterior part of the brain
• Occipital Condyles


  Prominent bones from the exoccipital
• Premaxillae


  Paired, short, teeth-bearing bones that form in the anterior most edge of the upper jaw
• Maxillae


  Paired, curved teeth-bearing bones, forming the margin of the jaw. These are the longest bones of the upper jaw
• Quadratojugals


  Posterior part of the upper jaw, does not bear teeth
• Squamosis


  Hammer-shaped, serves as a brace between the cranium and posterior portion of the jaw
• Eye socket


  Two large openings, lateral to the frontoparietals
• Ventral View of the Skull

  • Vomers - two flat, wing-shaped bones in the roof of the mouth just posterior to the premaxillae, bears vomerine teeth
  • Palatines - extends laterally, from near the median line to the maxillae
  • Parasphenoid - dagger-shaped singular bone that forms the floor of the cranium
• Visceral SkeletonThe visceral skeleton is the endoskeletal structure derived from the gill arches and in the frog, it consists of (a) the upper and lower jaws, (b) hyoid apparatus that provide support for the muscles used in respiratory movements of the mouth, and (c) the cartilages that support the ventral wall of the larynx or voice box.
• The Vertebral Column

  • Atlas - specialized for articulation with the skull, receives the occipital condyles of the skull, lacks transverse processes (represents fused ribs)
  • Urostyle - vertebral column beyond the sacral region, represents the tail or caudal vertebrae
• The Pectoral Girdle

  The pectoral girdle (shoulder girdle) consists of a series of bones and cartilages which encircle the body and provide support for the forelimbs. In the toad, the pectoral girdle is firmly attached to the sternum or the breastbone
• The Pelvic Girdle - supports the hindlimbs. It consists of two identical halves, one half of which is called an innominate bone.