Class 11-Zoology Lectures-Discuss the structure of the frog's heart & blood circulatory system -1.12
Structure of Frog's Heart
Overview of the Frog's Heart Location and Protection
- The frog's heart is located mid-ventrally between the two lungs and is covered by a protective layer called pericardium.
- The pericardium consists of two layers: the outer parietal pericardium and the inner visceral pericardium, which closely invests the heart.
- Between these layers lies the pericardial cavity filled with fluid that prevents jerks to the heart during movement.
Structural Characteristics of the Heart
- The frog's heart has a reddish appearance, triangular shape with a broad base and conical apex, consisting of three chambers: two oracles (atria) and one ventricle.
- It is classified as an arteriovenous type due to its circulation of mixed blood with intermediate oxygenation levels.
- In dorsal view, three major veins are visible: two pre-caval veins (right and left) and one post-caval vein leading into a large chamber known as sinus venosus.
Major Vascular Structures
- The truncus arteriosus divides into two branches: left and right, which further branch into three major trunks: carotid trunk, systemic trunk, and pulmonary trunk.
- Pulmonary veins from both sides open into the left oracle carrying oxygenated blood back to the heart.
Detailed Anatomy of Oracles
- The right oracle is larger than the left oracle; it features an aperture called Sino-Oricular aperture through which deoxygenated blood enters from sinus venosus.
- Sinus venosus is described as a dark-colored thin-walled triangular chamber that collects deoxygenated blood via three cable veins before directing it to the right oracle.
Functionality of Ventricular Structures
- The ventricle serves as the largest chamber receiving both deoxygenated blood from the right oracle and oxygenated blood from the left oracle for mixing before circulation.
- Important structures within include columnar carneae (irregular ridges) on its inner surface that aid in proper functioning during contraction phases. These gaps between ridges are referred to as fissures.
Role of Chordae Tendineae
- Chordae tendineae are thread-like structures connecting AV valve flaps to ventricular walls, preventing backflow during contractions ensuring efficient blood flow through chambers.
Mixing Blood in Ventricles
- Oxygenated blood from pulmonary veins enters through a common opening in left oracle while deoxygenated blood flows from right oracle; both types mix in ventricle forming intermediate oxygenation before being pumped out via truncus arteriosus upon ventricular contraction.