Practical 2 PDF

MODULE 5: EXTERNAL ANATOMY OF THE TOAD lower eyelids and a third, a transparent nictitating membrane. It keeps the eyes moist Frogs and toads belong to the order Anura, the underwater largest and the most dive...

MODULE 5: EXTERNAL ANATOMY OF THE TOAD lower eyelids and a third, a transparent nictitating membrane. It keeps the eyes moist Frogs and toads belong to the order Anura, the underwater largest and the most diverse group of living amphibians. Tympanic Membrane: Posterolateral to the eye is an ovoid region of tightly drawn skin. It is the THE SKIN OF TOAD eardrum and it covers the auditory canal. Toads have no external ears (only middle & internal). Epidermis: Made up of stratified epithelium w/ a thin, hardened surface layer of dead squamous Parotoid Gland: Found behind the tympanic cells that is constantly removed when a toad sheds. membrane it is a large swelling of a large aggregate of poison glands. Inner layer consists of living cuboidal to columnar cells that continuously divide to replace the shed Cloacal aperture: Found at the most posterior end off layer of the skin. of the trunk, on the dorsal side. The color of the skin is due to the row of black APPENDICULAR REGION OF THE TOAD pigment-containing cells called melanophores Made up of forelimbs (anterior pair) & hindlimbs found at the junction of the epidermis and dermis. (posterior pair). AXIAL REGION OF TOAD Forelimbs: Short and consists of 4 main parts Upper arm Snout: Most anterior portion of the of the head. Forearm Wrist/carpus External Nares / Nostrils: pair of openings at the Hand/manus tip of the snout. 4 digits & prepollex (thumb) Nictitating Membrane: At the dorsolateral portion of the head, posterior to the external nares are the bulging eyes. It has upper and 1  MODULE 6: MUSCULOSKELETAL SYSTEM OF THE TOAD THE SKELETON The skeleton has several functions: Serves as support or framework for the softer parts of the body; Provides a firm surface for the attachment of muscles used in movement and locomotion; Supplies calcium to the blood, and; Important site for the formation of blood Hindlimbs: Long and consists of cells. Thigh Shank Exoskeleton: consists of the hardened bony or Ankle/tarsus horny structures that develop in the skin and Foot/pes provides external protection to the animal 5 digits & Prehallux (6th toe) Endoskeleton: The skeleton of the frog/toad is SEX DETERMINING CHARACTERISTICS almost entirely endoskeletal in nature and consists almost entirely of bone and cartilage. Pigmentation (Ventral side of head): Males have a distinct dark pigmentation near the angles of the Skeletal muscles and skeleton are often considered jaw due to concentration of pigments. Females’ together as a functional unit that permits body pigments are diffused, hence, no dark movements and locomotion. pigmentation. Tendon: A connective tissue that attaches muscles Thumb Pads Of Inner Fingers: Males have enlarged to the bones. or “swollen” thumbs (used during amplexus or false copulation). Females’ thumb pads are not swollen. Aponeurosis: A broad, flat and sheet-like tendon. Sexual Dimorphism: Sexually mature males are SMALLER than sexually mature females. This is Belly: Skeletal muscles often have two points of because females are the one holding the eggs. attachment. This is the part in between. ENDOSKELETON DIVISIONS BASED ON POSITION Axial endoskeleton: Composed of all endoskeletal structures located at the center or axis of the body. Skull Visceral skeleton Vertebral column and ribs (it lacks true ribs) Sternum 2 Appendicular endoskeleton: Consists of all endoskeletal structures located laterally or in the Exoccipital: Surrounds the posterior part of the region of the extremities or appendages. brain. A pair of prominent bones project from it, Girdles: Pectoral & Pelvic called the occipital condyles. Bones of the limbs: Anterior/forelimbs & Posterior/Hindlimbs. Quadratojugals: Short bones make up the posterior part of the upper jaw, but unlike the premaxillae THE SKULL and maxillae, these do not bear teeth. Dorsal View Squamosals: Each shaped in the form of a hammer and serves as a brace between the cranium and the posterior portion of the jaws to support the cartilaginous auditory region. Ventral View Upper jaw consists of: Premaxillae, Maxillae, & Quadtrojugals. Premaxillae: Paired, short, teeth-bearing bones that form the anterior most 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. These are wide in front where the premaxillae articulate. Nasal bones: A pair of flat, triangular-shaped bones on the dorsal surface of the skull just behind the nares. Frontoparietals: Two long, slender, flat bones, just Vomers: two flat, wing-shaped bones in the roof of posterior to the nasal bones. These may be fused so the mouth just posterior to the premaxillae. The that they appear as a single bone. The ventral surface of each bears the vomerine teeth. frontoparietals cover most of the brain. Palatines: slender, rod-like bones on the lower side Foramen magnum: Posterior end of the skull and it of the cranium just posterior to the vomers. They has a large opening through which the spinal cord extend laterally from near the median line to the passes. maxillae. 3 Parasphenoid: It is dagger-shaped. It is a single Urostyle: It is found beyond the sacral region. This bone that forms the floor of the cranium. Cartilages represents several fused tail or caudal vertebrae. form the sides of the cranium. The urostyle has a conspicuous dorsal keel, and a hollow canal, best seen from the anterior end, into VISCERAL SKELETON which the spinal cord continues. The visceral skeleton is the endoskeletal structure THE PECTORAL GIRDLE derived from the gill arches and in the frog, it The pectoral girdle (shoulder girdle) consists of a consists of (a) the upper and lower jaws, (b) hyoid series of bones and cartilages which encircle the apparatus that provide support for the muscles body and provide support for the forelimbs. In the used in respiratory movements of the mouth, and toad, the pectoral girdle is firmly attached to the (c) the cartilages that support the ventral wall of sternum or the breastbone. the larynx or voice box. THE VERTEBRAL COLUMN The vertebral column of a frog is very specialized, due to the shortening of the trunk of the body. There are ten vertebrae that make up the vertebral column. THE PELVIC GIRDLE The pelvic girdle supports the hindlimbs. It consists of two identical halves, one half of which is called an innominate bone Atlas: It is the first vertebra. It is specialized for articulation with the skull by means of two large facets or depressions, which receive the occipital condyles of the skull. The atlas lacks traverse processes. Traverse Processes: It is present in all other vertebrae. These represent fused ribs and support the attachments of the muscles. 4  phalanges or smaller bones of the digits or fingers are attached. BONES OF THE HINDLIMBS (POSTERIOR LIMBS) Femur: Bone of the thigh BONES OF THE FORELIMBS (ANTERIOR LIMBS) Tibiofibula: Represents the fusion of two bones, the tibia and fibula of most land vertebrates. Tarsals: Ankle Bones; corresponding to the carpals of the wrist. The two proximal tarsals are greatly elongated thus giving the hindlimb an extra segment and an extra lever arm. There 4 additional distal tarsal bones. Astragalus / Tibiale: A b Calcaneus / Fibulare: The stouter of the two. Metatarsals: Consist of five long bones of the sole to which the smaller bones (phalanges) of the digits Humerus: Bone of the upper arm are attached. Radioulna: It is represents the fusion of two bones, the radius and ulna of other land vertebrates. The THE SKELETAL MUSCLES OF THE TOAD proximal end of the radio-ulna is extended into a process, known as the olecranon, which reaches The large spaces between the skin and muscles around the distal end of the humerus and serves for where the skin is not attached is the subcutaneous the attachment of muscles. lymph sacs. Carpals: Bones of the wrist. Metacarpals: Bones of the hand proper consist of four slender bones of the palm to which the 5 Ventral View of Head & Trunk Ventral View of Thigh & Shank Mylohyoid: Locate the median longitudinal connective tissue on the ventral side of the lower jaw. This connective tissue is called the median raphe. Lateral to the median raphe is the thin broad, transversely oriented fibers of the mylohyoid. Sternoradialis: Find this thick median pair of muscles which is partly covered by the posterior rim of the mylohyoid. Adductor longus: This is a slender muscle that can be seen by cutting the belly of the sartorius. Cutaneous pectoralis: Locate this most ventral, thin, pocket like superficial muscle Sartorius: Locate this flat strap-like muscle running obliquely along the ventral side of the thigh. Rectus abdominis: Identify the thin connective tissue running at the mid ventral portion of the Adductor magnus: Find the thick muscle near the abdomen. This is the linea alba. Lateral to the linea groin area, seen as a triangle when the sartorius is in alba is a longitudinal muscle called the rectus place. This is also the muscle immediately posterior abdominis. to the adductor longus. External oblique: find the sheet like muscle lateral to Gracilis major: locate this large muscle with oblique the rectus abdominis. Notice that the direction of fibers situated posterior to the adductor magnus. muscle fibers ran obliquely. Gastrocnemius: Locate this large muscle situated at the back of the shank. Note the white tissues (fascia) surrounding the belly of this muscle. Tibialis posticus: Find this long, narrow but thick muscle anterior to the gastrocnemius and partly covered by it. This is seen attached to the surface of the tibiofibula. Tibialis anticus: locate the most anterior muscle of the shank which can also be seen dorsally. This muscle splits into two distally. 6 Dorsal View of Head & Trunk Triceps Femoris: this is the largest, three-headed muscle that covers the lateral surface of the thigh. Semimembranosus: this large muscle is found next to the biceps femoris Biceps femoris: locate this slender muscle posterior to the triceps femoris Longissimus dorsi: find the mass of muscle lying alongside the mid-dorsal line and tapering posteriorly Iliolumbaris: locate the muscle lateral to the longissimus dorsi. The lateral or horizontal skeletogenous septum, a strong connective tissue, separates the iliolumbaris from the lateral external Peroneus: locate this muscle of the shank oblique. immediately anterior to the gastrocnemius and partly covered by it. Coccygeo-iliacus: locate a pair of large V-shaped muscles situated between the ilia of the pelvic girdle. Dorsal View of Thigh & Shank Gluteus: Find this small but thick muscle found between the two heads of the triceps femoris 7