The document discusses the formation of pearls, detailing both old and new views on how they develop, primarily through irritation from foreign bodies. It provides a biological classification of the pearl oyster and explains the structure of its shell and mantle, which play crucial roles in pearl formation. Finally, it outlines the natural process through which pearls grow, emphasizing the significant role of nacre secretion by the mantle tissue.

1. Pearl|‫موتی‬
ANWAR ULLAH
29
7TH SEMESTER

2. CONTENTS:
Views about Pearl Formation
Pearl Oyster
C.S of Pearl Oyster
Stages of Pearl Formation

3. VIEWS ABOUT PEARL FORMATION:
• Old view: The rain drop when fall inside the mouth
of pearl oyster become converted into PEARL.
• New views: Three views,
i. Pearl formation due to the irritation caused to the
mantle by the entry of foreign bodies.( most
accepted view)
ii. Internal parasites act a provoking agent-PEARL
iii. Internal pathological condition of the host - PEARL

4. • Pearl form in Mussels, mullusc .

5. PEARL OYSTER:
• Kingdom: Animalia
• Class: bivalvia
• Order: Pterioida
• Family: Pterioidea
• Genus: Pteriidae
• Phylum: mollusca

6. IMPORTANT SPECIES:

8. C.S OF SHELL AND MANTLE OF OYSTER:
• Essential to know the Structure of Shell and Mantle ( Soft Connective
Tissues).
Shell: Three distinct layers
1. Periostracum: Outermost layer, greenish-brown, thin, transparent, made
up of an organic substance “Conchiolin”. Secreted by Mantle. Help to
protect the underlying layers.
2. Prismatic Layer: Middle layer, secreted by Mantle, made up of minute
crystal of calcium carbonate( Separated by layers of conchiolin). Give
strength and rigidity to shell
3. Nacreous Layers: inner most layer, mother of the Pearl – Layer is
responsible for the Pearl formation. Secreted by mantle. Protect the
delicate surface from harmful effects of foreign particles.

9. MANTLE:
• Also 3 Layers:
1. Columnar epithelium: conation numerous nacre secreting
unicellular glands.
2. Connective tissue layer: middle, fibrous layer, composed of
connective tissue
3. Ciliated epithelium: inner most layer, mucous secreting cells

10. C.S OF SHELL AND MANTLE OF OYSTER:

11. STAGES OF NATURAL PEARL FORMATION:
• Sometimes a foreign body accidently enters into the body of the oyster,
when the shells remain open, and gets trapped between the shell and
the mantle. The outer epithelium of the mantle Invaginats and form
the pearl sac.
• Inside the pearl sac, as a result of secretion of nacre, a natural pearl
grows.
• The secretion of nacre continues till the end of life of the pearl oyster,
thereby forming/producing a beautiful, natural pearl.

12. Conti…………..
• Pearl is formed due to secretion of the mantle tissue.
• The nacreous layer of the pearl is secreted by the outer epithelial layer
of the mantle.
• This layer has the capability to rearrange and regenerate itself .

14. Two types :

15. JAZAKALLAH!!
ANY QUESTION??