Diversity in vertebrate tongue, salivary glands esophagus, girzzard and stomach


Tongue:
A tongue develops in the floor of oral cavity in many vertebrates e.g. lamprey has a prototractible tongue with horny teeth that rasp its prey flesh. Fishes may have a non-muscular tongue that bears teeth that help hold prey. Tetrapods have evolved mobile tongues for gathering food. Frogs and salamanders and some lizards can rapidly project part of their tongue from the mouth to capture an insect. A wood pecker has a long spiny tongue for gathering insects and grubs. Ant and termite eating mammals also gather food with long, sticky tongues, spiny papillae on the tongues of cats and other carnivores help these animals rasp flesh from a bone.
Salivary glands:

Most fishes lack salivary glands in the head region. Lampreys are an exception because they have a pair of glands that secrete an anticoagulant needed to keep their preys blood flowing as they feed. Modified salivary glands of some snakes produce venom that is injected through fangs to immobilize prey.
In amphibians or reptiles and must birds lack salivary glands while all mammals have them.

Esophagus:
Esophagus is short in fishes and amphibians but much longer in amniotes due to their longer necks. Grain and seed eating birds have a crop that develops from the caudal portion of the esophagus. Storing food in the crop ensures continuous supply of food to the stomach and intestine for digestion. This structure allows these birds to reduce the frequency of feeding and still maintain high metabolic rate.

Stomach:
Stomach is an ancestral vertebrate structure that evolved as vertebrates began to feed on longer organisms that were caught at less frequent intervals and required storage. The gastric glands and their production of Hydrochloric acid (HCl) evolved to kill bacteria and helping preserve food. The enzyme pepsinogen has evolved later because the stomach is not essential for digestion.

Gizzards:
Some fishes, crocodilians and all birds have a gizzard for grinding up food. The bird’s gizzard develops from the posterior part of stomach called the ventriculus. Pebbles that have eating birds and facilitate the grinding process.

Comments

Post a Comment

Popular posts from this blog

What is the Dynamic Theory of Profit

Image
Clark's Dynamic Theory of Profit And Its Criticism The Dynamic Theory of Profit is associated with the name of an American Economist, J. B. Clark. In the world of reality, according to J. B. Clark, profit arises only in a dynamic economy. An economy is said to be dynamic when there is a change in population growth or change in the method of production or a change in the consumer’s wants, etc. A society which is without these changes is called a static society. In a static society, only monopoly profits continue to exist. All other economic profits are gradually eliminated by competition. In a dynamic society, an entrepreneur is always confronted with continuous unpredictable changes in demand for his product. The variation in demand may take place due to changes in fashions, tastes, the standard of living, distribution of income, population, new inventions, international repercussions, technological advances, etc. A prudent entrepreneur will always keep an eye on future demand
Read more

Compare the anatomy of Bifacial and Isobilateral leaves

BIFACIAL LEAF: It is also called dorsiventral leaf. This leaf is more strongly illuminated on upper surface than on lower surface. This unequal illumination induces a difference in the internal structure between upper and lower sides. Its internal structure shows: (1)        Upper Epidermis This is single layer of cells with thick cuticle which checks excessive evaporation of water from the surface. It does not contains chloroplasts, stomata are also absent. (2)        Lower Epidermis This is also single layer but with a thin cuticle. It bears many stomata, two guard cells of which contain some chloroplast, none are present in the epidermal cells. Internal to each stomata is large cavity called respiratory cavity. Lower epidermis of leaf is meant for exchange of gases (oxygen and carbon dioxide) between the atmosphere and the plant body. Excess water also evaporates from lower epidermis. (3)        Mesophyll The ground tissue lying between upper epidermis and th
Read more

osmoregulation in terrestrial and aquatic animals

Mechanism of osmoregulation is very important for all groups of animals whether inhibting land or water. Unlike plant cells, animal cells when placed in hypotonic solution burst due to the continuous absorption of water. On the contrary they would shrink and die if constantly placed in hypertonic solution. Normally uptake and loss of water are in balance for proper survival of cell. (1)        Osmoregulation in terrestrial animals: Terrestrial animals are more likely to loose water by evaporation through their permeable surfaces exposed to amsophere. Among various animal groups only Arthropods and vertebrates became the most successful land dwellers. They have developed number of strategies to maintain osmoregulation of their body fluid. (a) Water proof external coverings: To prevent water loss through external surfaces, vertebrates like reptiles, birds and mammals have water proof keratinized epidermis. Similarly the insects have developed external water proof layer called
Read more