How To Study Living Animals


The Organs of Circulation and Respiration of the Frog
Materials.

The materials used in this exercise are the same as those used in the preceding exercise herunterladen.

Observations.

The pupil should identify the following structures:—

Pericardium,

a membrane that surrounds the heart and, in the case of the frog, separates the body cavity into two portions, the abdomen and the pericardial chamber herunterladen.

Heart,

lying between the shoulders and in front of the false diaphragm. It is conical in form and composed of three chambers microsoft office kostenlos downloaden vollversion deutsch chip.

Ventricle,

the pink, conical, and muscular portion of the heart, pointing backward and outward.

Auricles,

right and left. These are anterior and dorsal to the ventricle, thin, membranous, and dark-colored.

Arterial trunk,

the single large blood vessel, usually empty of blood, and white. Note its origin and trace it as far as possible, at least until you see it divide to encircle the throat.

Sinus venosus,

a large membranous sac dorsal to the heart and connected with the right auricle.

Lungs,

two small oblong, pink, spongy sacs, lying between and behind the shoulders.

The pupil may also identify the following structures if a specimen is available which has the blood vessels injected.

Conus arteriosus,

or “arterial trunk,” a large artery passing obliquely forward from the ventricle, and dividing into three branches on each side.

Carotid arteries,

the first branches of the conus, to the head and neck.

Aortas,

the second branches of the conus, to the dorsal region.

Pulmocutaneous arteries,

the third branches of the conus, to the lungs and skin.

Dorsal aorta,

the large artery along the back, formed by the union of the two aortas.

Iliac, or femoral arteries,

the two posterior divisions of the dorsal aorta, supplying the legs.

Posterior (ascending) vena cava,

a large vein close to the dorsal aorta, passing forward from the kidneys.

Hepatic veins,

large veins connecting the liver with the posterior vena cava.

Anterior (descending) venæ cavæ,

large veins formed by the junction of the veins from the arm, neck, and head on the right and left sides.

Subclavian veins,

from the arms.

Jugular veins,

from the neck.