Frog Dissection Notes

External Anatomy

• Dorsal surface darker than ventral for camouflage.

• Smooth, moist skin aids in cutaneous respiration.

• Size varies by species.

Countershading

• Lighter ventral, darker dorsal side for camouflage.

• Disrupts body outline, seen in other animals.

Limbs and Webbing

• Webbing on back feet for efficient swimming.

Swimming

• Coordinated limb movement and webbed feet for propulsion.

External Structures

• Nictitating membrane: Protects eye while swimming.

• Tympanic membrane: Circular, behind eye, for hearing.

• External nares: Nostrils for breathing while floating; can be closed when submerged.

Mouth Structures

• Tongue: Attached at front, sticky, for catching prey.

• Internal nostrils: Connect to external nares, used for breathing.

• Vomerine teeth: Two pointed teeth to hold prey.

• Maxillary teeth: Ridge of teeth to hold prey.

• Frogs swallow prey whole.

Throat Structures

• Eustachian tubes: Equalize pressure during dives.

• Esophagus: Leads to stomach.

• Glottis: Leads to lungs, controls airflow.

Internal Anatomy

• Cut from lower stomach to jaw to view organs.

Liver

• Largest organ with three lobes.

  • Filters toxins, produces bile.

  • Left Anterior Lobe: Most forward.

  • Left Posterior Lobe: Extends back.

  • Right Lobe: Often largest.

Heart

• Above liver, pink, triangular, circulates blood.

  • Ventricle: Single chamber, pumps blood.

  • Atria: Left receives oxygenated blood, right receives deoxygenated blood.

Lungs

• Spongy, near heart, for gas exchange.

• Blood to heart, lungs, then body.

Gallbladder

• Under liver's right lobe, stores bile for fat digestion.

Stomach and Pancreas

• Stomach under liver, leads to duodenum for initial digestion.

• Pancreas within stomach curve, produces digestive enzymes and regulates blood sugar.

Stomach Structure

• Rugae: Folds for expansion.

• Mucosa: Releases digestive enzymes.

• Pyloric Sphincter: Valve to small intestine.

Intestines

• Stomach to duodenum for chemical digestion.

• Small intestine absorbs nutrients.

• Large intestine (colon) absorbs water, compacts waste.

Mesentery and Spleen

• Mesentery: Holds small intestine together, contains blood vessels.

• Spleen: Reddish sphere, filters blood.

Kidneys and Bladder

• Kidneys filter waste, bladder stores urine.

• Urine exits via cloaca.

Testis

• Cream-colored, on kidneys, only in males