Exploring the Frog's Anatomy: Respiratory, Circulatory, and Excretory Systems

In our previous lab session, we examined the digestive system of the frog. In this continuation, we will dissect the frog further to explore its respiratory, circulatory, and excretory systems. Understanding these systems is crucial for comprehending how frogs, as amphibians, adapt to their environments.

Frog Respiration

All animals engage in respiration, a process that involves taking in oxygen and expelling carbon dioxide. Frogs have a unique approach to respiration, utilizing three different methods:

1. Skin: Frogs can absorb oxygen directly through their skin, which is a vital adaptation for their semi-aquatic lifestyle.
2. Mouth Cavity: The lining of the frog's mouth also plays a role in gas exchange.
3. Lungs: Although frogs possess lungs, they do not rely solely on them for respiration. Consequently, their lungs are relatively small compared to those of mammals.

To observe the right lung during dissection, we must lift the lobes of the liver. The left lung is located beneath the liver, making it less visible during the procedure.

Frog Circulatory System

The heart is the primary organ of the circulatory system in frogs. It is protected by a tough, clear membrane known as the pericardium, which cushions the heart. To examine the heart's structure, we need to open the pericardium.

Upon opening the pericardium, we can identify the three chambers of the frog's heart:

• Right Atrium
• Left Atrium
• Ventricle

To further explore the circulatory system, we must remove the liver and some digestive organs carefully to avoid damaging the heart or the blood vessels beneath. The liver consists of three lobes that converge in the middle. We will begin by cutting away the right lobe, followed by the left posterior lobe, and finally the left anterior lobe.

Next, we will remove the stomach and small intestines, along with the stringy fibers known as fat bodies. These fat bodies are accumulations of fatty tissue that frogs use to store energy, particularly before hibernation in winter or estivation during hot, dry summers.

With the liver removed, we can observe a significant network of arteries and veins located just posterior to the heart, known as the hepatic portal system. This system is crucial as it allows all of the frog's blood to flow into and out of the liver, where toxins are filtered out.

The main artery responsible for carrying blood away from the heart is the aorta. The aorta splits into two systemic arches, which then rejoin in the lower abdomen to form the . Several smaller arteries branch off from the dorsal aorta, including the , which transport blood to the kidneys for filtration.