Alimentary canal

The large intestine consists of the caecum, colon and rectum.
NCERT describes the caecum as a small blind sac which hosts some symbiotic micro-organisms.
The duodenum is the first part of the small intestine and receives bile and pancreatic juice; it is not the site of symbiotic microbes.
The vermiform appendix is a vestigial organ and the rectum only stores faeces temporarily.
Hence the symbiotic microorganisms normally occur in the caecum.

An adult human has 32 permanent teeth of four types (heterodont dentition): incisors (I), canines (C), premolars (PM) and molars (M).
The dental formula gives the number of each type in one half of the upper jaw over one half of the lower jaw, in the order I, C, PM, M.
Each half of each jaw has 2 incisors, 1 canine, 2 premolars and 3 molars.
Dental formula: $\frac{2123}{2123}$, i.e., $\frac{2}{2},\frac{1}{1},\frac{2}{2},\frac{3}{3}$
Check: (2 + 1 + 2 + 3) × 2 halves × 2 jaws = 8 × 4 = 32 teeth.

The pharynx is a common passage for food and air; the oesophagus and the trachea both open into it.
The opening of the wind pipe is the glottis. During swallowing a cartilaginous flap, the epiglottis, covers the glottis and prevents the entry of food into the wind pipe.
If the epiglottis does not close the glottis properly, for example when a person talks or laughs while eating, food particles enter the wind pipe.
This triggers the cough reflex to expel the food.
Hence the coughing is due to improper movement of the epiglottis.