N. V. Tatsenko introduction to theoretical phonetics of english

The Pharynx. It lies between the mouth and the food passage, that is, just above the larynx. It is just about 7cm long in the case of women and 8cm long in the case of men.
The Roof of the Mouth. It is considered as a major speech organ. It is divided into three parts:
a) the alveolar ridge/teeth ridge. The alveolar ridge is the slightly rough area just behind the top teeth (after the upper front teeth). It can also be called the tooth ridge or the gum ridge. The tongue touches or almost touches the alveolar ridge when we say the sounds [t], [d], [s], [z], [l], and [n]. The
sounds which are produced touching this convex part are called alveolar sounds.

2. 
   the hard palate. It is the concave part of the roof of the mouth and is situated on the middle part of the roof, beginning just behind the alveolar ridge. It can also be called the roof of the mouth. When you close your mouth, your tongue is probably flat against your hard palate. The tongue touches or almost touches the hard palate when we say the sounds [f], [3],
   

И1 №L ^{and [}y^].

2. 
   t
   he velum or soft palate. The soft palate is the softer part of the roof of the mouth, farther back than the hard palate. It is also called the velum. If you touch the roof of your mouth with your tongue and then keep moving your tongue farther back, you’ll find that softer area. It could be lowered or raised. When it is lowered, the air stream from the lungs has access to the nasal cavity. When it is raised the passage to the nasal cavity is blocked. The sounds which are produced touching this area with the back of the tongue are called velar sounds. The back of the tongue touches the soft palate when we say the sounds [k], [g], and [g] (see fig. 2.6):