Frog Anatomy (1960)

[Music] biology students find that careful and inquiring examination of a frog is a rewarding experience it teaches them much concerning the anatomy of vertebrates if a living frog is used there are many ways to prepare it for dissection one way is to their gauze soaked with an anaesthetic such as ether is added in time prob will become completely limp and ready for examination by prying open the large mouth its internal structures can be examined the minut maxillary teeth are embedded along the edges of the upper jaw the two groups of bomber and teeth project from the bones of the roof of the mouth on either side of the vomer and teeth are the internal nostrils here are the eustachian tubes they connect the mouth with the middle ear the throat contains two openings one into the large esophagus which leads to the stomach and below it the slit-like glottis which leads to the lungs the front of the fleshy sticky tongue is attached to the floor of the mouth next the organs in the body cavity will be examined before the Frog is dissected it's secured to the bottom of the tray pinning is a good way to do this after all the limbs are pinned down the body cavity is open raising the skin with the forceps helps in starting the longitudinal incision the incision is made to the sternum care should be taken to avoid injury to the underlying structures next transverse cuts are made in the skin the connective tissue which attaches the skin to the underlying muscle layer needs to be cut when the skin is laid back the pattern of its blood vessels is very evident cutting the remaining connective tissue frees the skin it is then pinned down this procedure is repeated for the other side the abdominal wall can now be seen clearly as a muscular structure when cutting the muscle wall of the bullfrog severing the abdominal vein is avoided to prevent excessive bleeding the muscle wall is lifted and a longitudinal incision is made on one side of the vein the incision is made with care to avoid damaging the underlying organs now two transverse incisions are made one near the sternum the other at the posterior end the muscle flap is pinned down in this specimen one of the lungs is still inflated and is therefore very conspicuous this procedure is repeated for the other side the abdominal vein lying in the strip of tissue must be tied off before being cut after tying the second knot the vein is cut between the two knots and placed the side this permits an unobstructed view of the internal organs some of the most obvious organs are those of the digestive system parts of the digestive tract seen here are the stomach pylorus small intestine and large intestine associated with the digestive tract are the liver the gallbladder and the pancreas the organs are held in place by fan-like membranes the mesentery by carefully cutting the mesentery x' the digestive system can be removed so that its parts can be observed more clearly when food is swallowed it passes through the very short esophagus to the stomach where digestion begins the stomach tapers at the lower end and joins the small intestine at the pylorus the food is digested and absorbed as it passes through the many loops of the small intestine the undigested food enters the shorter and broader large intestine it connects to the cloaca which leads to the exterior the three logged liver among its other functions secretes bile the bio collects in the gallbladder and passes through the bile duct into the small intestine the pancreas lies in the mesentery inside the curve of the stomach it produces the gest of juices which pass into the upper small intestine with the digestive system removed from the dissected specimen parts of the urinary system can be pointed out the two kidneys lie on either side of the spine the bladder is a transparent 2 lobe structure in order to see the urinary system more clearly it has been removed from another frog urine collects in the kidneys and flows through tiny kidney ducts to the cloaca some of the urine may be forced into the bladder where it is stored until eliminated frogs are of two sexes the specimen being dissected is a male its reproductive cells or sperms developed in the testes the sperms pass from the testes through tiny white tubes which lead to the kidney ducts the two fat bodies can also be seen the path of the sperms can be more easily traced on this male reproductive system which was dissected from another frog sperms develop in the testes and pass through the kidneys in tiny tubes when the sperms are discharged they pass through the kidney ducts and cloaca to the exterior the frog that is dissected may be a female this one was collected during the breeding season in early spring so its body cavity contains eggs the masses of eggs are in large transparent ovaries because they obstruct the view of many of the organs the eggs need to be removed note the two inflated lungs in this specimen here is one of the two long coiled oviducts the fat bodies attached above the kidneys are also found in the female frog the path of the eggs can be clearly seen in this female reproductive system the eggs burst the ovary balls enter the body cavity and pass into the openings of the oviducts the eggs move through the OVA ducts and are eventually laid bypassing out of the cloaca the two fat bodies are also shown in order to examine the heart and the blood vessels entering and leaving it the sternum is removed the pericardium the sac which surrounds the heart is carefully cut the frogs heart has three chambers the left auricle the right Oracle and the ventricle the truncus arteriosus arises from the ventricle if the heart is turned over the dorsal side can be examined the two pulmonary veins enter the left article these are the three tributaries of the vena cava they unite in the thin walled sac the sinus venosus which connects with the right oracle the spleen and organ in the circulatory system lies in the mesentery of the small intestine if an incision is made through the skin of the hind leg its muscles tendons and nerves can be examined the white tendons fasten the muscles to the bones if we cut through the muscle layers the sciatic nerve can be located by careful probing the nerve is found and pulled to the surface further examination of the nervous system is shown with a preserved specimen the nerve which was located in the leg is traced along the backbone it enters the backbone and joins the enclosed spinal cord many pairs of nerves branch from the spinal cord to all parts of the body the spinal cord can be traced to the brain to examine the parts of the brain the skull must be opened the skin is cut away then the bones which cover the delicate brain are carefully removed the parts of the brain can now be examined the or factory tracks the or factory lobes the cerebrum the optic lobes the cerebellum and the medulla part of the spinal cord can also be seen in addition to the investigations of the frog which we have just seen the alert and inquiring biology student will find opportunities for many other rewarding experiences for example investigating the frogs method of breathing examining through the microscope such things as blood flow investigating further the structure of the various organs discovering new and interesting things such as these parasitic flatworms and using other sources to help you obtain fuller understanding the careful and thoughtful examination of the frog will reward you with first-hand information concerning its anatomy and that of other vertebrates [Music] [Applause] [Music]