Exercise 7.1
Draw a neat diagram of digestive system of frog.
The book prints no answer for this
NCERT publishes no answers for this textbook, so there is nothing in the book to check this working against. It has also not yet been read through by hand.
The diagram is the alimentary canal of the frog drawn as one continuous tube from mouth to cloacal aperture, with the two digestive glands — liver and pancreas — attached near its front end. The book's own drawing is Figure 7.2.
What to draw, in order down the page
Mouth, opening into the buccal cavity; show the bilobed tongue inside it, as food is captured by the tongue.
Pharynx, leading into a short, narrow oesophagus.
Stomach — a wide, curved sac lying to one side of the mid-line; digestion here is by HCl and gastric juices from its walls.
Intestine — begins as the duodenum, which runs forward beside the stomach, then continues as the coiled intestine. Keep the whole canal short: the frog is a carnivore, so the intestine is reduced.
Rectum — a short, wider tube after the intestine.
Cloaca, a small median chamber, opening to the outside at the cloacal aperture.
Glands to add
Liver — a large, lobed gland drawn over the front part of the stomach; it secretes bile.
Gall bladder — a small oval sac tucked under the liver; it stores the bile.
Pancreas — a thin gland in the fold between the stomach and the duodenum; it makes pancreatic juice.
Common bile duct — one duct carrying bile from the gall bladder and pancreatic juice from the pancreas into the duodenum. Draw it as a single line entering the duodenum.
Labels the diagram must carry
Buccal cavity, tongue, oesophagus, stomach, liver, gall bladder, pancreas, bile duct, duodenum, intestine, rectum, cloaca, cloacal aperture.
Figure $\displaystyle 7.2$ of the book also shows the lung, heart, kidney, ureter, urinary bladder and fat bodies, because it is a drawing of all the internal organs. For a digestive-system answer these need not be labelled.
