Anatomy of an Frog Structural Organization of Animals CBSE Class 11 Biology by Elearnin

frog anatomy the study of frogs is known as batracology they live on land and in fresh water it is the first land-based four-legged creature they originated in the devonian period and developed during the carboniferous period morphology frog's body contains head and body without neck or tail above the mouth pair of nostrils is present eyes are bulged and covered by nictitating membrane that protects them while in water on either sides of the eyes membranous tympanum receives sound signals the forelimbs and hind limbs help in swimming walking leaping and burrowing the hind limbs end in five digits and they are larger and muscular than four limbs that end in the four digits feet have webbed digits that help in swimming frogs exhibit sexual demorphism male frogs can be distinguished by the presence of sound amplifying vocal sacks and also copulatory pad on the first digit of the four limbs which are absent in the female frogs anatomy the body cavity of frogs accommodate different organs which constitute the viscera these are enveloped by an internal covering called the visceral peritoneum digestive system the digestive system consists of elementary canal and digestive glands the elementary canal is short because frogs are carnivores and hence the length of intestine is reduced the mouth opens into the buccal cavity that is short and shallow teeth are present at the rim of the upper jaw the muscular tongue is split into at the tip the tongue is attached at the front of the mouth and free at the back the pharynx opens into the short esophagus which in turn opens into the stomach the stomach has the cardiac sphincter at the start and the distal pyloric sphincter the stomach helps to store and digest food the first part of the small intestine is the duodenum and the distal part is long and coiled this is the ilium the ilium opens into the rectum the rectum is short and broad it opens to the outside through the cloaca digestive glands the stomach wall has small gastric glands they secrete gastric juices the largest gland is the liver it opens into the diodinum through the common heptic duck the bile secreted from the liver is stored in the gall bladder bile doesn't contain any digestive enzymes the pancreas is non-capsulated long-mixed gland located between the stomach and the duodenum it secretes pancreatic juices duodenal glands secrete duodenal juices feeding and digestion the tongue acts by obtaining the food in the stomach digestion begins by the action of gastric enzymes in the presence of hydrochloric acid partially digested food is called chyme it reaches the small intestine through the gastric outlet there it mixes in the duodenum with bile and pancreatic juices bile emulsifies fat pancreatic enzymes complete the digestion of carbohydrates fats and proteins this digested food is absorbed by villi in the lumen of the intestine the undigested solid waste reaches the rectum and are excreted through the anus respiratory system frog respires through three separate roots one skin two buca pharyngeal cavity three lungs the skin of frog is thin and moist with abundant blood circulation the skin is permissible to both oxygen and carbon dioxide oxygen diffuses through the moist skin into the blood capillaries in the same way carbon dioxide diffuses through the skin out into the atmosphere for respiration through the skin the skin must be moist apart from skin and lungs the moist bucopharyngeal cavity is also rich in blood vessels to facilitate the exchange of gases this mode is used when the frog is on land when on land it also respires through the lungs the lungs are pink coloured sacs with abundant blood supply for pulmonary circulation the bucopharyngeal pouch functions as forced pump when the bucopharyngeal pouch is compressed the lens opens and air is forced into the lungs here exchange of gas occurs following which the pouch relaxes and expands when this happens air is sucked and expelled via the bucco pharyngeal pouch and the nostrils blood circulation system it consists of the heart blood vessels and blood the superior part of the torso contains the muscular heart it contains two atria and ventricle it is covered by two layers of pericardium arteries supply blood from the heart to the body parts three major veins collect blood from the body and send it to the atria frogs have incomplete double circulation systems portal systems special venice connection between liver and intestine as well as the kidney and lower parts of the body are present in frogs the former is called heptic portal system and the latter is called renal portal system blood it contains plasma and cells the blood cells include erythrocytes lyoko sites and thrombocytes erythrocytes here are nucleated and help in the transport of oxygen white blood cells are non-nucleated they are amoeboid and help in defense thrombocytes help in blood coagulation integrating system frogs have well-developed system for control and coordination it includes both neural system and endocrine glands the chemical coordination of various organs of the body is achieved by hormones which are separated by the endocrine glands the prominent endocrine glands found in frog are pituitary thyroid parathyroid themis pineal body pancreatic islets of langerhans adrenals and garnets special senses frogs have different types of sense organs namely organs of touch taste smell vision and hearing out of these eyes and internal years are well organized structures and the rest are cellular aggregations around nerve endings the skin has receptors the small taste buds present on the tongue help in taste perception they help by jointly acting as smell and taste sense organs excretory system in order to excrete waste and maintain the water salt balance frogs have well-developed excretory system the excretory system consists of pair of kidneys uterus and urinary bladder cloaca these are compact dark red and bean-like structures situated in little posteriorly in the body cavity on both sides of the vertebral column only its lower part is covered by the peritoneum male reproductive organs consist of pair of yellowish ovoid testes which are found adhered to the upper part of kidneys by double fold of peritoneum called misortium each testes has millions of seminiferous tubules they jointly form 10 to 12 vasa efferentia which join the bitter canal finally it communicates with the uranogenital duct and opens into the cloaca the female reproductive system consists of pair of ovaries oviducts and cloaca the ovaries are adhered to the upper part of kidneys by double fold of peritoneum the peritoneum is called ovarian spore the ends of the oviducts form broad opening which opens separately into the cloaca during coagulation the females release large amounts of eggs called spawn male frogs release semen which is called milt external fertilization and development take place in the water during development the larval tadpole stage is formed which is vegetarian and breeds through the gills like fish the tadpole breeds through its gills you