Page 29 - E-Biology Sec.2 2024-2025 U1_Handy

A) Buccal digestion

1- Mouth The 1st organ in the digestive system which is a cavity, in which

teeth and tongue are existed and salivary glands are opened.

A) Teeth: the number of teeth is 32 in adults exist in 2 jaws; each one has:
4 incisors: at the front of jaw and cut food.
2 canines: follow the incisors and tear food.
10 molars (4 premolars & 6 molars): follow the canines
crush and grind food to make its swallowing easy.

B) Tongue: 1- An organ of taste.
2- Manipulate food and mix it with saliva to be chewed and swallowed easily.

C) Salivary glands (3 pairs): secrete saliva that contains:
Mucus softens the food and facilitates its swallowing.
Amylase (Ptyalin) (PH= 7.4).

Saliva (amylase/ Ptyalin)

Starch + water Weak alkaline Disaccharide (Maltose / malt sugar)

2- Pharynx A common cavity between oesophagus and trachea.

Swallowing: An organized reflex action, as during it,

the top of trachea & larynx are elevated in front of the epiglottis
to close the glottis, so the food is pushed from the mouth to the oesophagus.

First Term Reflex action is an involuntary fast
29 response for sensory stimulus without

interference / consciousness.