Write a note on the arterial system of frog.

ARTERIAL SYSTEM OF FROG:

 Blood vessels carrying oxygenated blood from the heart to all parts of the body are called arteries, which together form a system called the arterial system.
The arterial system has two main branches:
 each of which further divides into three branches which are as follows.

1. Carotid Arch:

 It is composed of the arteries carrying oxygenated blood to various parts of the head region such as brain, tongue. head muscles, eyes, ears. lower jaw, etc.

2. Systemic Arch:

 It is composed of the arteries carrying oxygenated blood to all parts of the body except the head and lung. Right and left systemic arches join posteriorly to form dorsal aorta. The dorsal aorta is a major vessel of this system. It transports blood to various parts of the body.
 Prior to their union, each systemic arch gives out arteries supplying blood to vertebral column, oesophagus and forelimbs.

Dorsal Aorta:

 Dorsal aorta runs along the vertebral column towards the hind limbs.
Coeliacomesenteric artery originates from dorsal aorta and supplies blood to digestive system.
Renal arteries supply blood to kidneys and genital organs.
Posterior mesenteric artery carries blood to rectum Iliac arteries transport blood to hind limbs of their sides.

3. Pulmocutaneous Arch:

  It carries blood to lungs and skin. Pulmonary arteries carry deoxygenated blood to lungs for oxygenation. While cutaneous arteries supply blood to the skin.

 All the arteries after reaching their regions of supply branch and rebranch into smaller thin walled vessels called capillaries. 

Through the thin walls of capillaries exchange of materials between blood and tissue cells takes place. Capillaries join to form venules, which form veins and carry deoxygenated blood from all parts of the body to the heart.