BRANCHIOSTOMA-RENAL PAPILLAE

The cells are present on the floor of atrial cavity form renal papillae which are probably also excretory in function.

BRANCHIOSTOMA-EXCRETORY SYSTEM

They closely resemble the protonephridia of flatworm providing good example ofparallei evolution. Some other organs and cells are also shows excretory systems.

BRANCHIOSTOMA-LYMPHATIC SYSTEM

Lymph as such is lacking.The so-called lymphatic spaces or sinuses present inside fins and metapleural folds, are called filled with colourless blood lacking in leucocytes. It is the oxygen required by the animal is obtained by the gaseous exchange between outside water and blood inside these superficial sinuses.

BRANCHIOSTOMA-COURSE OF CIRCULATION

Blood flows anteriorly inside parietal ,subintestinal and posterior cardinal veins and ventral aorta. It flows posteriorly inside lateral and median dorsal aortae and anterior cordinal vein. The course of circulation can be graphically represented .

BRANCHIOSTOMA-PARIETAL VEINS

Bloodfrom dorsal body wall is collected by a pair of parietal veins one on either side. They run above the intestine for some distance and the turn ventrally to join the sinus venous.

BRANCHIOSTOMA-CARDINAL VEINS

The blood from ventrolateral region is collected on either side by an anterior and a posterior cardinal vein. The two unite just behind the pharynx to form a common cardinal vein or ductus cuvieri. The two ductus curieri then run down through the atrium to join the sinus venosus.

BRANCHIOSTOMA-HEPATIC PORTAL SYSTEM

The subintestinal vein continue anteriorly as the hepatic portal vein running ventrally along up in the midgut diverticulum into which it breaks up in a capillary network. Blood is collected by a hepatic vein running along its dorsal border and bending downwards to join the sinus venosus. Hepatic portal system occuring for the first time in Branchiostoma is a precursor of that of higher chordates.