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DIGESTION AND ABSORPTION

IMPORTANT TERMS:

 v  Absorption: Passing of diffusible food through small intestine into blood or lymph.

v  Appendicitis: Inflammation and abnormal elongation of vermiform appendix.

v  Deglutition: Swallowing of food bolus into the oesophagus.

v  Enamel: The hardest material which covers the exposed part of the tooth.

v  Splenchnology: It is the study of viscera.

v  Dyspepsia: Indigestion due to defective diet.

v  Modified Teeth: Vomerine teeth of frog kill prey, fangs of a poisonous snake are maxillary teeth, elephant tusks are modified incisors and tusks of walrus are modified canines.

v  Dental Formula: Number and arrangement of teeth in one-half of each jaw.

v  Digestion: Conversion of non-diffusible food into diffusible food by the process of hydrolysis.

v  Egestion: Expelling out of undigested food as faeces.

v  Emulsification: Breaking of large fat droplets into a fine emulsion by bile juice of the liver.

v  Extracellular Digestion: Digestion occurring outside the cells.

v  Fluorosis: Disease caused by the excess of fluorine in the diet.

v  Heterodont: Presence of different types of teeth, e.g., in mammals.

v  Heterotrophic Nutrition: Intaking readymade organic food by consuming plants or animals.

v  Holozoic Nutrition: Obtaining food like animals, i.e., solid food through mouth.

v  Homodont: When all the teeth are similar, e.g., in frog.

v  Intracellular Digestion: Digestion of food inside the cells.

v  Microvilli: Electron microscopic processes on free surface of intestinal cells to increase the surface area for absorption of food.

v  Milk Teeth: Which appear earlier in the life and are replaced by the permanent teeth.

v  Night-blindness: Inability to see at night, caused due to deficiency of vitamin A.

v  Osteomalacia: A disease of bones in adults caused due to deficiency of vitamin D.

v  Peristalsis: Involuntary movements of gut wall which moves food backward.

v  Protein Energy Malnutrition (PEM): Deficiency of proteins as well as food calories.

v  Regurgitation: Back flow of food from stomach to oesophagus. It is found in ruminants.

v  Rickets: A disease of bones in children caused due to the deficiency of vitamin D.

v  Ruminants: Cud-chewing mammals, e.g., cattle.

v  Scurvy: A disease caused by deficiency of vitamin C.

v  Villi: Finger- like of intestinal mucosa to increase the surface area for absorption of food.

ADDITIONAL INFORMATION

v  Dentition: (i) Many fossil reptiles and Archeopteryx had thecodont dentition.

       (ii) Thecodont condition also occurs in crocodilians.

       (iii) Pleurodont dentition occurs in lizards and Acrodont in frog.

       A natural space between two types of teeth is called diastema.

In rabbit which lacks canine teeth, a diastema is present between the incisor and premolar on each       side.

v  Carnasial teeth in dog are (last upper premolar and first lower molar) used for tearing flesh.

 

v  Dental Formula of other Animals

 

Rabbit=2023 ⁄1023 = 28

 

Dog =3142 ⁄3143 = 42

 

Cat=3131 ⁄ 3121= 30

 

Rat =1003 ⁄1003 = 16 *

 

Horse = 3143 ⁄3143=44*

*Maximum  and  minimum number of teeth in mammals.

(i) Spiny ant-eater. Scaly ant- eater and Whales are Toothless mammals.

(ii) Bats, Guinea pig loose milk teeth before birth.

(iii) Platypus, toothed whales, sloths (bear) and sirenians (sea-crow) are Monophyodont.

v  The Ruminant Stomach

In ruminant animals (mammals that chew the cud such as cattle, the buffaloes, sheep, goat, camel,   deer, etc.), the stomach is divided into chambers—the rumen (punch), the reticulum, omasum and the aboasum. Camel and deer, however, do not have omasum.

Rumen is the largest chamber.

 

v  Gastritis: Inflammation of the stomach generally due to excessive consumption of alcohol.

v  Peptic Ulcer: Inflammation of mucosa of stomach and duodenum due to acidic gastric juice.

v  Constipation is infrequent passage of dry, hardened faeces.

v  Ulcerative Colitis: Mucosal lining of the colon becomes ulcerated.

v  Bad Breath is usually due to cavities in the teeth, infection of throat and nose.

v  Poison Glands of a snake are modified labial glands homologous to parotid salivary glands. Tongue of Whale is not movable.

v  Pigeon’s Milk is produced by its crop glands.

Mr. A. KINGSLIN M.Sc, BEd, Phd,(doing)
Post Graduate Teacher in Botany
St. Mary Goretty Hr. Sec School, Manalikarai 
Kanyakumari district





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