● The body `color{violet}("cavity of frogs")` accommodate different `color{brown}("organ systems")` such as `color{violet}("digestive, circulatory, respiratory, nervous, excretory")` and `color{violet}("reproductive systems")` with well developed structures and functions.

● The digestive system consists of `color{brown}("alimentary canal")` and `color{brown}("digestive glands")`.

● The `color{violet}("alimentary canal")` is short because `color{violet}("frogs are carnivores")` and hence the length of intestine is reduced.

● The mouth opens into the `color{brown}("buccal cavity")` that leads to the `color{brown}("oesophagus")` through pharynx.

● `color{brown}("Oesophagus")` is a short tube that opens into the `color{violet}("stomach")` which in turn continues as the intestine, rectum and finally opens outside by the `color{violet}("cloaca.")`

● `color{brown}("Liver")` secretes `color{brown}("bile")` that is stored in the `color{brown}("gall bladder.")`

● `color{brown}("Pancreas")`, a digestive gland produces `color{violet}("pancreatic juice")` containing digestive enzymes.

● Food is captured by the `color{brown}("bilobed tongue.")`

● `color{violet}("Digestion of food")` takes place by the action of `color{brown}("HCl")` and `color{brown}("gastric juices")` secreted from the walls of the `color{violet}("stomach.")`

● Partially digested food called `color{brown}("chyme")` is passed from stomach to the first part of the intestine, the `color{brown}("duodenum.")`

● The `color{violet}("duodenum")` receives bile from `color{violet}("gall bladder")` and `color{violet}("pancreatic juices")` from the pancreas through a `color{brown}("common bile duct")`.

● Bile `color{brown}("emulsifies fat")` and pancreatic juices `color{brown}("digest carbohydrates")` and `color{brown}("proteins.")`

● `color{violet}("Final digestion")` takes place in the intestine.

● `color{violet}("Digested food")` is absorbed by the numerous finger-like folds in the inner wall of intestine called `color{brown}("villi and microvilli.")`

● The undigested `color{violet}("solid waste moves")` into the `color{brown}("rectum")` and passes out through `color{brown}("cloaca.")`

● `color{violet}("Frogs respire")` on land and in the water by two different methods.

`star` `color{green}("Cutaneous Respiration")`

● In water, `color{brown}("skin")` acts as `color{violet}("aquatic respiratory organ")` (`color{brown}("cutaneous respiration")`).

● `color{violet}("Dissolved oxygen")` in the water is exchanged through the `color{violet}("skin")` by `color{brown}("diffusion.")`

`star` `color{green}("Pulmonary Respiration")`

● On `color{violet}("land")`, the `color{brown}("buccal cavity, skin")` and `color{brown}("lungs")` act as the `color{violet}("respiratory organs.")`

● The respiration by `color{violet}("lungs")` is called `color{brown}("pulmonary respiration.")`

● The `color{violet}("lungs")` are a pair of elongated, `color{violet}("pink coloured sac-like structures")` present in the upper part of the trunk region `color{violet}("(thorax).")`

● Air enters through the nostrils into the `color{violet}("buccal cavity")` and then to `color{violet}("lungs.")`

● During `color{violet}("aestivation and hibernation")` gaseous exchange takes place through skin.

● The `color{violet}("vascular system of frog")` is well-developed `color{brown}("closed type.")`

● Frogs have a `color{brown}("lymphatic system")` also.

● The `color{violet}("blood vascular system")` involves `color{brown}("heart, blood vessels")` and `color{brown}("blood.")`

● The `color{violet}("lymphatic system")` consists of `color{brown}("lymph, lymph channels")` and `color{brown}("lymph nodes.")`

`star` `color{green}("Heart:")`

● `color{brown}("Heart")` is a `color{violet}("muscular structure situated")` in the upper part of the `color{violet}("body cavity.")`

● It has three chambers, `color{brown}("two atria")` and `color{brown}("one ventricle")` and is covered by a membrane called `color{brown}("pericardium.")`

● A `color{violet}("triangular structure")` called `color{brown}("sinus venosus")` joins the right atrium.

● It receives `color{violet}("blood")` through the major veins called `color{brown}("vena cava.")`

● The ventricle opens into a saclike `color{brown}("conus arteriosus")` on the ventral side of the `color{violet}("heart")`.

● The blood from the `color{violet}("heart")` is carried to all parts of the body by the arteries (arterial system).

● The `color{violet}("veins")` collect `color{violet}("blood")` from different parts of body to the heart and form `color{brown}("the venous system.")`

● Special venous connection between `color{violet}("liver and intestine")` as well as the kidney and lower parts of the body are present in `color{violet}("frogs.")`

● The former is called `color{brown}("hepatic portal system")` and the latter is called `color{brown}("renal portal system.")`