Circulatory System of Frog | Zoology : Biology

UNIT SEVEN | DETAILED STUDY OF FROG
Class 11

Circulatory system of Frog

Circulatory system is the system of blood, heart, and blood vessels. 

1. Heart 

· Heart is triangular muscular pumping organs. 

· Heart of frog is situated ventrally to the liver in the pericardial cavity. 

· Heart is three –chambered. 

· Upper two chambers are called auricle sand lower one chamber is called ventricle. 

· Its anterior end is broader then posterior end. 

· The broader part anterior is known as auricle. 

· The posterior part is known as ventricle. 

· The ventricle is thick walled than auricles .right auricle is larger than left auricle.

External structure of heart 

From the ventral view 

· The tubular structure is present on right side of anterior part of ventricle, which is called truncus arterious gives two branches called aortic trunks. 

From the dorsal view 

· There is somewhat triangular structure called sinus venosus. It opens into right auricle. The right precaval, left precaval and post caval veins open into sinus venosus. 

Internal structure of heart: 

· Two auricles are separated by a septum called internal auricular septum. 

· The right auricle bears opening of sinus venosus called sinu-auricular aperture which is guarded by valves called sinu- auricular valves. 

· It allows flow of blood from sinus venous to right auricle and prevents back flow of blood. 

· Left auricle bears opening of pulmonary vein without valve. 

· Auricles open into ventricles by auriculo-ventricular aperature, which is guarded by four auriculo –ventricular valves. 

· The flaps of these valves are connected to the wall of ventricles by chordae tendinae. 

· A ventricle is thick walled and internally give in folding called trabecule. 

· Ventricle opens into truncus arterious. 

· The opening is guarded by four semilunar valves, which prevent backward flow of blood from truncus arterious to ventricle. 

· A truncus arterious is divided into two parts at the base. 

o conus arteriosus ( plangium)- which consists spiral valves. 

o Bulbous arteriosus ( synangium)- which is again divided into two parts. 

Cavum aorticum and cavum pulmocutanum. 

Each aortic trunk again divides into three vessels: Carotid arch, Systemic arch, Pulmo -cutanous arch 

Arterial system of frog 

Blood vessels, which carry oxygenated blood away from heart to different part of the body, are called arteries. They constitute a system called arterial system. Truncus arterious gives two branches right aortic trunk and left aortic trunk. Each aortic trunk again divides into three branches- 

a) Carotid arch: it divides into – 

Lingual artery – it supplies blood to tongue and hyoid. 

Common carotid – it supplies blood to buccal cavity and brain. it consists swelling at the base called carotid labyrinth. 

b) Systemic arch – two systemic arches move upward and then curve backward to join each other behind the heart to form dorsal aorta before meeting each other each systemic arch gives- 

Oesophageal artery – it supplies blood to osephagus. 

Occipito vertebral artery – it supplies blood to head and vertebral column. 

Subclavian – it supplied blood to shoulder and forelimb. From the junction of two systemic arches coeliaco – mesenteric artery arise which gives following branches. 

Coeliac artery arises and gives two branches – 

Hepatic artery artery – it supplies blood to liver. 

Duodenal artery –it supplies blood to duodenum. 

Intestinal artery – it supplies blood to small intestine (ileum). 

Spleenic artery – it supplies blood to spleen (meeting place of ileum and rectum). 

Posterior mesenteric artery- It is Long Branch and supplies blood to the rectum. 

The dorsal aorta runs backward and gives following branches- 

Gonadial artery – it supplies blood to testes and ovary. 

Renal artery- it supplies blood to kidney. At the end, the dorsal aorta runs posterior and bifurcates into  right and left common iliac arteries. Each of iliac arteries gives 

Femoral artery – it supplies blood to hip and thigh. 

Sciatic artery – it supplies blood to lower region of hind legs. 

Epigastric artery- it supplies blood to urinary bladder. 

c) Pulmo-cutanous arch- it divides into 

Pulmonary artery – it receives deoxygenated blood from different parts of the body and open into lungs. 

Cutanous artery- it supplies oxygenated blood to skin. 

Venous System of frog 

Blood vessels, which carry the deoxygenated blood from different parts of the body to the heart, are called veins. They constitute a system called venous system. Venous system of frog can be studied under too heading 

A) Systemic Venous System 

This system includes the three large veins, which receives the deoxygenated blood from all the parts of the body and collect to the sinus venous. The three veins are- 

Right Precaval, Left precaval and Post cavals 

1. Right and Left Precaval Vein: Each precaval is formed by the union of 3 veins 

External jugular vein - it is formed by the two veins. 

a. lingual vein – it receives deoxygenated blood from mouth and tounge. 

b. mandibular vein – it receives deoxygenated blood from lower jaw. 

innominate vein – it is formed by two veins. 

a. internal jugular vein- it receives deoxygenated blood from eye brain and skull. 

b. subscapular vein- it receives deoxygenated blood from shoulder and arm.

subclavian vein- it is formed by two veins- 

a. brachial veins- it receives deoxygenated blood from fore limb. 

b. muscub cutanous vein – it receives deoxygenated blood from muscles and skin. 

2. Post Caval Vein: It receives deoxygenated blood from following 3 veins. 

Hepatic vein- it receives deoxygenated blood from liver. 

Gonodial vein- it receives deoxygenated blood from gonads. 

Renal vein – it receives deoxygenated blood from kidney. 

B) Pulmonary Venous System 

The pulmonary vein receives pure blood from lungs into left auricle of heart.