Note on terminology: "Amylogenesis" is not a standard term. You likely mean amelogenesis - the process of dental enamel formation. Here is a detailed account.

Secretory Stage of Amelogenesis

1. Matrix production (Secretory stage)
2. Matrix maturation (Maturation stage)

Stage 1: Matrix Production - Secretory Stage

Overview

Fig. 16.13 - Diagram and photomicrograph showing cellular relationships during enamel formation. Secretory-stage ameloblasts deposit enamel matrix onto the previously formed dentin. (Histology: A Text and Atlas)

Morphology of Secretory-Stage Ameloblasts

Fig. 16.14 - Schematic of amelogenesis showing enamel rod formation, the path of secretory-stage ameloblasts over time (5 months in utero to 9 months), and the Tomes processes surrounded by hydroxyapatite crystals.

Matrix Proteins Secreted

• Amelogenin - the dominant structural protein (~90%); initiates and guides growth of hydroxyapatite crystals; encoded on the X chromosome
• Enamelin - non-amelogenin matrix protein
• Ameloblastin (sheathlin) - associated with Tomes processes

Supporting Cells - Stratum Intermedium

Stage 2: Matrix Maturation Stage

Fig. 16.16 - Left (H&E): Secretory-stage ameloblasts (AM) with Tomes processes (TP), distal terminal web (DTW), and proximal terminal web (PTW). Right (SEM): Maturation-stage ameloblasts (MA, green) with smooth apical surfaces resting on enamel surface (E, orange).

Key Events in Maturation

• Removal of organic matrix - enzymes degrade and reabsorb the organic proteins
• Continued influx of Ca²⁺ and phosphate - enamel becomes progressively more mineralized (~96% mineral in mature enamel)
• Cyclic modulation - maturation-stage ameloblasts alternate between:
  • Striated (ruffled) border (~70% of time): Secretes HCO₃⁻ ions and pumps Ca²⁺ via plasma membrane Ca²⁺-ATPase (PMCA) into enamel
  • Smooth-ended border (~30% of time): Secretes enzymes (e.g., kallikrein-4) to degrade and remove residual matrix
• The stratum intermedium disappears - replaced by a reorganized papillary layer containing stellate papillary cells with abundant mitochondria (reflecting high energy demand for ion transport)

Summary Table

Secretory Stage of Amelogenesis

• Definition: It is the first stage of amelogenesis in which secretory-stage ameloblasts deposit a partially mineralized organic enamel matrix. Dentin is always formed first, and enamel matrix is then deposited directly onto the dentin surface.
• Cell morphology: Secretory-stage ameloblasts are tall, polarized columnar cells. Each cell has an apical cytoplasmic extension called the Tomes process, which is packed with secretory granules containing enamel matrix proteins.
• Matrix proteins secreted: The main proteins produced are amelogenin (~90%), enamelin, and ameloblastin. These are synthesized via rER → Golgi → secretory granules and guide hydroxyapatite crystal growth.
• Direction of enamel rod formation: As each ameloblast moves away from the dentinoenamel junction, the enamel rod forms in its wake. The direction of the rod is thus a permanent record of the ameloblast's path.
• Supporting cells: At the base of secretory-stage ameloblasts lies the stratum intermedium, whose plasma membrane contains alkaline phosphatase - an enzyme active in calcification.
• End point: The secretory stage continues until the full thickness of the future enamel layer is achieved, after which ameloblasts differentiate into maturation-stage ameloblasts.

Secretory Stage of Amelogenesis

1. First stage of amelogenesis; dentin is formed first, then enamel matrix is deposited onto the dentin surface.
2. Performed by secretory-stage ameloblasts - tall, polarized columnar cells derived from the inner enamel epithelium.
3. Each ameloblast has an apical Tomes process packed with secretory granules containing enamel matrix proteins.
4. Main proteins secreted: amelogenin (~90%), enamelin, and ameloblastin - synthesized via rER → Golgi → secretory granules.
5. These proteins guide hydroxyapatite crystal nucleation and growth, producing a partially mineralized matrix.
6. Enamel rods form in the wake of the moving ameloblast; rod direction reflects the path of the ameloblast.
7. Stratum intermedium lies at the base of ameloblasts and provides alkaline phosphatase for calcification support.
8. Stage ends when the full thickness of enamel is achieved; cells then differentiate into maturation-stage ameloblasts.

Secretory Stage of Amelogenesis

Definition

• It is the first and major stage of amelogenesis in which ameloblasts actively secrete organic enamel matrix proteins to form the full thickness of enamel.

Where It Occurs

• Occurs in the developing tooth germ, specifically at the dentinoenamel junction (DEJ)
• Takes place after dentin formation by odontoblasts
• Enamel matrix is laid down directly on the surface of dentin

Cells Involved

• Performed by secretory-stage ameloblasts - tall, polarized columnar cells derived from the inner enamel epithelium
• Each ameloblast has an apical extension called the Tomes process, packed with secretory granules

Function

• Synthesizes and secretes enamel matrix proteins via rER → Golgi → secretory granules
• Main proteins: Amelogenin (~90%), Enamelin, Ameloblastin
• These proteins guide hydroxyapatite crystal nucleation and growth
• Continues until the full thickness of future enamel is achieved

Location of Supporting Structures

• Stratum intermedium lies at the base of ameloblasts - provides alkaline phosphatase for calcification
• Stellate reticulum lies external to stratum intermedium
• Blood vessels supply nutrients through the enamel organ

Significance

• Establishes the complete thickness and rod pattern of enamel
• Direction of each enamel rod permanently records the path taken by each ameloblast
• Lays the organic framework that will be fully mineralized in the next (maturation) stage
• Disruption during this stage leads to Amelogenesis Imperfecta (hypoplastic type)

Secretory (Formation) Stage of Amelogenesis

Definition

• It is the stage of amelogenesis in which ameloblasts actively secrete enamel matrix proteins to lay down the full thickness of enamel, beginning after the initial layer of enamel is formed.

Cell Morphology

• Ameloblast is 30-50 µm long and 5-10 µm wide
• rER increases in the distal cytoplasm, oriented parallel to the long axis of the cell
• Changes occur after the initial layer of enamel is deposited

Tomes' Process

• Tomes' process contains secretory granules
• Proximal part - forms inter-rod enamel
• Distal part - forms enamel rod (organic matrix)
• Within the organic matrix, hydroxyapatite crystals of enamel appear

Enamel Rod Formation

• Formation of the central rod enamel is always ahead
• Later, enamel rod is formed onto the cavity wall
• When ameloblast is pulled away → leaves a honeycomb appearance

Tomes' Process Alteration

• The outermost portion of enamel is formed when the shape of the distal portion of Tomes' process is altered
• Later, ameloblasts become flat (lose Tomes' process)

End of Secretory Phase

• Secretory phase ends with the full thickness of enamel being laid down
• Matrix deposited is high in organic content at this stage, later replaced by mineral during maturation