Frog Anatomy and Dissection Techniques

Support and Protection Equipment and Materials

• Gloves
• Safety Pin
• Field Frog
• Dissecting Pan
• Scissors and cutting instrument

Background

• Animal bodies have definite shapes and structures composed of various parts
• These parts enable animals to perform life functions and interact with their environment
• Frogs are suitable models for studying vertebrate anatomy due to their affordability, abundance, size, observable life cycle, and structural similarities to higher vertebrates and humans.

Classification of a Field Frog

• Phylum: Chordata
• Subphylum: Vertebrata
• Class: Amphibia
• Order: Anura
• Family: Ranidae
• Genus: Rana
• Species: vittigera
• Field frog: Rana vittigera
• Bullfrog: Rana catesbeina
• Frog body is divided into two major parts: axial region (head and trunk) and appendicular region (limbs).

Frog Morphology Important Parts

• Head: Snout (triangular), mouth, eyes (upper, lower, and nictitating membrane), nostrils (external nares), tympanic membrane, brow spot, and humps
• Trunk: Anus, forelimbs (upper arm, forearm, wrist, hand/manus, four fingers), hindlimbs (thigh, shank, ankle/tarsus, foot with webbed toes, prehallux), and diffused/darkly pigmented skin areas

Frog Morphology Objectives and Activities

• Familiarization with external parts and skeleton of frogs
• Anesthetizing frogs using pithing technique
• Pinning frogs in dissecting pans
• Identifying frog structures

Frog Morphology Questions

• Frog classification
• Reasons for frog skin moisture
• Sex determination based on external features
• Toad vs. frog distinctions

Skeletal System

• Crucial for all vertebrates
• Provides support, attachment points for muscles for movement and protection of internal organs
• Supplies calcium to blood cells

Vertebral Column

• Composed of individual vertebrae
• Atlas (first vertebra) articulates with the skull
• Typical vertebra structure (centrum, neural arch, neural canal, neural spine, transverse processes, prezygapophysis, postzygapophysis)
• Sacral vertebra connects to the pelvic girdle
• Urostyle (10th vertebra) is the terminal vertebra

Sternum

• Breastbone
• Pectoral girdle divides it into anterior and posterior
• Omosternum—tapered bone connected to the epicoracoid
• Episternum—flat, circular cartilage; connects to the omosternum
• Mesosternum—bony rod positioned behind the omosternum

Pectoral Girdle

• Forms anterior support
• Consists of suprascapula, scapula, clavicle (collarbone), and coracoid
• Forms an arch around anterior trunk parts in collaboration with sternum

Pelvic Girdle

• V-shaped
• Supports and connects posterior limbs.
• Has ilium (anterior, slender), ischium (posterior, dorsal), and pubis (ventral)
• Formation of acetabulum (cup-like socket) where femur (thigh bone) fits.

Anterior Limbs (Forelimbs)

• Humerus (upper arm)
• Radio-ulna (forearm)
• Carpals (wrist bones)
• Metacarpals (palm bones)
• Phalanges (finger bones)

Posterior Limbs (Hindlimbs)

• Femur (thigh)
• Tibio-fibula (shank or lower leg)
• Tarsals (ankle bones)
• Metatarsals (foot bones)
• Phalanges (toe bones)
• Calcar (supports prehallux)

Skull

• Premaxillae (upper jaw tip)
• Maxillae (upper jaw middle)
• Quadratojugals (skull roof)
• Fronto-parietals (skull main part)
• Sphenethmoid (bone anterior to fronto-parietals)
• Nasals (bones anterior to spenethmoid)
• Prootics (enclose inner ear)
• Squamosals (lateral to prootics)
• Occipitals (posterior portion, surrounding foramen magnum)
• Occipital condyles (projections)
• Parasphenoid (skull floor)
• Vomerine (flat, teeth bearing, behind premaxillae)
• Palatines (rod-like, extending from vomer)
• Pterygoids (connected to prootics, squamosals, and maxillae)

Hyoid Apparatus

• Cartilage beneath tongue
• Has body, alary processes, anterior cornua, thyroid process, and posterior cornua

Lower Jaw

• Divided into left and right halves
• Contains:
  • Mento-meckelian (anterior)
  • Dentary (middle)
  • Angulo-splenial (posterior)

Specific Vertebral Structures

• Atlas (1st vertebra)
• Typical vertebrae (2nd -8th)
• Sacral vertebra (9th, articulates with pelvic girdle)
• Urostyle (10th, terminal)

Objectives and Activities

• Learning about bones
• Labeling illustrations of bones

Questions

• Skeleton functions
• Endoskeleton vs. exoskeleton
• Distinguishing typical and atypical vertebrae
• Pectoral girdle structure
• Pelvic girdle structure