Describe briefly the body wall of sponges

The body wall of a common sponge consists of three layers which are
(i) Pinacoderm (dermal layer) It is an outer cellular layer which consists of
{a) flattened pinacocytes (b) oval porocytes
(ii) Choanoderm (gastral layer) It is inner cellular layer consisting of highly specialised flagellated cells called choanocytes or collar cells.
(Hi) Mesohyl layer (mesenchyme) It is a non-cellular layer found in between pinacoderm and choanoderm. It has fine dispersed spongin fibres and numerous spicules. It also contains amoebocytes of both pinacoderm and choanoderm.
Amoebocytes are modified into following cells
(a) Archaeocytes (totipotent cells) (b) Trophocytes (nurse cells)
© Thesocytes (d) Gland cells
(e) Collencytes (f) Myocytes
(g) Germ cells (k) Chromocytes
(i) Phagocytes.