The Process of Digestion in Frogs
The Dietary Habits of Frogs
Frogs are carnivorous creatures that primarily feed on spiders, earthworms, fishes, snails, small frogs, and small insects. They capture their prey and swallow it whole, aided by their protractible tongue.
Ingestion of Food in Frogs
Frogs have a unique way of capturing their prey. They strategically position themselves in areas frequently visited by insects. When an insect comes within reach, they open their mouths and quickly flick their sticky tongue out to strike the prey. As soon as the prey comes into contact with the tongue, it sticks to it. The tongue is then retracted into the buccal cavity.
Once the prey is trapped in the buccal cavity, it cannot escape due to the presence of the hook-like inwardly directed maxillary and vomerine teeth. The prey is then pushed from the buccal cavity into the oesophagus by the contraction of the pharyngeal wall. From there, it is propelled into the stomach through peristalsis, a process involving the contraction and dilation of the muscular walls of the oesophagus.
Digestion of Food in Frogs
The ingested food consists of complex organic particles which cannot be immediately used by the body due to their insoluble nature. Thus, they must undergo physical and chemical changes through the process of digestion to be transformed into soluble forms that the body can readily use.
The physical changes are caused by the peristaltic movements of the alimentary canal, while the chemical changes are brought about by enzymes acting as organic catalysts. These enzymes, which are complex proteins, accelerate the chemical reactions without changing themselves. They are produced by the exocrine glands and function at the body's optimum temperature. These enzymes can also reverse reactions, meaning that substances can be reformed. They come in various types, depending on the type of food they act upon. Hence, proteins are digested by proteolytic enzymes, fats by lipolytic enzymes, and carbohydrates by diastatic enzymes.
Absorption of Food in Frogs
The final products of digestion are absorbed through the walls of the small intestine. The internal absorptive surface is increased by the presence of villi-like processes. Each villus is richly supplied with blood capillaries and lacteal or lymph vessels. Mineral salts, water, and other nutrients are absorbed directly through the mucosa.
Glucose, amino acids, and fructose pass by diffusion from the mucosa into the blood capillaries of the intestine, reaching the liver through the hepatic portal vein. The liver maintains a steady supply of the required amount of amino acids and sugars in the blood. Excess sugar is stored as glycogen, but excess amino acids cannot be stored, so they are converted into urea by the liver cells and discarded as urine from the kidneys.
If there is a drop in the level of sugar concentration from the normal in blood, the reserve glycogen is converted into glucose by the liver cells and released into the blood. From the blood, cells take up the required amino acids for the synthesis of proteins, forming protoplasm.
The fatty acids and glycerol pass into the lymph vessels, known as lacteals. Glycerol can be easily absorbed as they are water-soluble, but fatty acids cannot be absorbed as they are water-insoluble. Thus, before fatty acids are absorbed, they are mixed with bile salts to make them soluble. Once absorption occurs in the lacteals, the fatty acids and glycerol are reconverted into small molecules of fat. As a result, the fats enter the blood through the lymph vessels as glycerol and fatty acids.
Assimilation of Food in Frogs
Assimilation refers to the process where different cells take up the required amount of different digested food either to provide energy or to build new protoplasm. The conversion of the digested food into new protoplasm is facilitated by vitamins. The mineral salts also form parts of the protoplasm.
Egestion of Undigested Food in Frogs
The absorption and digestion are completed in the small intestine. The ingested food enters the rectum through peristalsis for the formation and storage of faeces. The faeces, which consist of leukocytes, old epithelial cells, bile pigments, and a large number of bacteria, are expelled periodically through the cloacal opening.
This comprehensive overview provides an in-depth understanding of the digestive system of a frog. For more related topics and concepts, stay tuned.
More to explore:
| Digestive system of Earthworms |
| Digestive system of Balanoglossus |
