In most frogs salivary glands are absent bcoz the saliva they needed is formed at the tip of their tongue. but as exception poisonous frogs have modified salivary glands by which they secrete poison.

The Structure Present in Man but Absent in Frog: Salivary Glands

Salivary Glands:
- Salivary glands are a group of glands present in the oral cavity of humans and other mammals.
- These glands secrete saliva, which plays an important role in the process of digestion.
- Saliva contains enzymes, such as amylase, which help in the breakdown of carbohydrates and initiate the process of digestion.
- Salivary glands also produce mucus that lubricates the food, making it easier to swallow.
- In addition to digestion, saliva also helps in maintaining oral hygiene by washing away food particles and reducing the risk of dental caries.

Comparison between Humans and Frogs: Salivary Glands

Presence in Humans:
- Humans have three pairs of major salivary glands: parotid glands, submandibular glands, and sublingual glands.
- The parotid glands are the largest salivary glands and are located on each side of the face, in front of the ears.
- Submandibular glands are situated below the lower jaw, while sublingual glands are present beneath the tongue.

Absence in Frogs:
- On the other hand, frogs do not possess salivary glands.
- Instead, they have a relatively simple oral cavity without the presence of major salivary glands.
- The absence of salivary glands in frogs suggests that they do not secrete saliva or possess the enzymes required for the initial digestion of food in the oral cavity.

Importance of Salivary Glands in Humans:
- Salivary glands play a crucial role in the process of digestion in humans.
- The enzymes present in saliva, such as amylase, help break down complex carbohydrates into simpler sugars, facilitating their absorption in the small intestine.
- Saliva also contains antibacterial enzymes that help prevent oral infections and maintain oral hygiene.
- Additionally, saliva aids in speech and taste perception by facilitating the movement of food and providing moisture to the oral cavity.

Conclusion:
- The presence of salivary glands in humans and their absence in frogs highlights the anatomical and physiological differences between these two organisms.
- Salivary glands are an essential component of the human digestive system, facilitating the initial breakdown of food and maintaining oral health.
- The absence of salivary glands in frogs suggests that they rely on alternative mechanisms for digestion and oral hygiene.