LBBBIO8 Toad External Anatomy PDF

TOAD Stratum Spongiosum LBBBIO8 – Zoology Laboratory Aka stratum laxum Instructor: Mr. Paolo Ramon Pacheco outer sublayer immediately below t...

TOAD Stratum Spongiosum LBBBIO8 – Zoology Laboratory Aka stratum laxum Instructor: Mr. Paolo Ramon Pacheco outer sublayer immediately below the stratum germinativum. It consists of loosely arranged connective tissue and blood OUTLINE vessels. It is the layer where the body of cutaneous glands are I. Integumentary system situated, thus giving it a spongy appearance. A. Histology of the skin 1. Stratum corneum Numerous glands are found in this layer. The glands are of 2. Stratum germinativum two types- the poison glands (larger glands) possess a 3. Stratum spongiosum thin epithelial wall, and the smaller and more numerous, 4. Stratum compactum the mucous glands, have thicker walls. II. External anatomu of the frog A. Anatomical directions 1. Regions of the body Stratum Compactum 2. Planes of the body 3. Terms consists of layers of white fibrous connective tissue 4. Axial region which are compactly arranged. 5. Appendicular region B. External sex determining characteristics EXTERNAL ANATOMY OF THE FROG INTEGUMENTARY SYSTEM ANATOMICAL DIRECTIONS Two layers - epidermis and dermis HISTOLOGY OF THE SKIN Regions of the body Anterior - head end Posterior - tail end Stratum Corneum Dorsal - back side outermost stratified layer of squamous epithelial tissue of Ventral - belly side flattened, dead cells. This is the thin hardened or cornified layer constantly removed when the toad sheds its skin (ecdysis or molting). Stratum Germinativum innermost sublayer consisting of living and growing layer of stratified epithelial tissue. The cuboidal to columnar cells continuously divide and replace the constantly shed off stratum corneum of the skin. At the junction of epidermis and dermis are Planes of the body chromatophores, specialized connective tissue which Frontal - dorsal and ventral sections contains pigments. Specifically, they contain a row of black Sagittal (longitudinal) - right and left sections pigment containing cells called melanophores which are Transverse (cross) - anterior and posterior sections in large part responsible for the color of the skin. Castilla, Selene Mari D. | 1 LBBBIO8 – TOAD EXTERNAL ANATOMY Terms Medial - near the middle Lateral - to the sides Proximal - part of a structure that is nearer the origin Distal - part farther from the origin. Axial Region Composed of the head and the trunk. ○ Note that the two are broadly joined by a very short neck thereby restricting movement of the head. The most anterior portion of the head is the pointed snout. External nares - pair of openings at the tip of the snout At the dorsolateral portion of the head, posterior to the exterior nares are the bulging eyes. It has upper and lower eyelids and a third, a transparent nictitating membrane which keeps the eyes moist when underwater. Posterolateral to the eye is an ovoid region of tightly drawn skin, the tympanic membrane (eardrum) covering the auditory canal. The frog and toad do not have external ear, only the middle and internal ears. Behind the tympanic membrane at each side of the head is a large swelling called paratoid gland/ poison gland. Cloacal aperture - at the most posterior part of the trunk, on the dorsal side. Appendicular Region Forelimbs (anterior pair) and the hindlimbs (posterior pair). The paired appendages vary in form and function. The forelimbs are short and consist of four main parts: the upper arm, forearm, wrist/carpus, and hand/manus which bear four digits and a rudimentary thumb called prepollux. The hindlimbs are long and consist of the thigh, shank, ankle/tarsus, and foot/pes. These bear five digits and a sixth rudimentary toe called prehallux. Note the webbed toes. EXTERNAL SEX DETERMINING CHARACTERISTICS Male Female The skin on the ventral side The pigments are of the head near the angles diffused; hence, there is of the jaw has a distinct no distinct pigmentation dark pigmentation due to at this area. concentration of pigments. The thumb pads of inner The thumb pads of the fingers are enlarged or inner fingers are not “swollen”. These are used “swollen”. during amplexus or false copulation. Sexually mature male frogs Sexually mature female are generally smaller than frogs are relatively female. bigger than male. Castilla, Selene Mari D. | 2 LBBBIO8 – TOAD EXTERNAL ANATOMY Castilla, Selene Mari D. | 3