Histology of Chief and Oxyphil Cells

Study Notes

Most numerous cells in the parenchyma of parathyroid glands.
Small, polygonal shape with central rounded nuclei and pale, slightly acidophilic cytoplasm due to glycogen content.
Ultrastructural features include:
- Juxtanuclear Golgi complex.
- Elongated mitochondria with numerous cristae.
- Abundant rough endoplasmic reticulum (rER).
- Presence of lipofuscin pigment, glycogen granules, and lipid droplets.
- Smaller dense granules that contain parathyroid hormone (PTH).
Function of PTH:
- Increases blood calcium levels, antagonistic to calcitonin hormone.
- Promotes phosphate excretion, lowering blood phosphate levels.
- Secretion regulated by serum calcium levels.

Fewer in number and larger than chief cells, with small, deeply stained nuclei.
Cytoplasm more acidophilic, present singly or in clusters, increasing in number with age.
Ultrastructural characteristics:
- Abundant mitochondria and small Golgi complex with minimal rER.
- Contains glycogen and lipid droplets among mitochondria.
- Presence of secretory granules.
Function: Unclear, potentially considered as immature chief cells.

Endocrine portion of the pancreas comprised of pale rounded clusters of epithelial cells within dense exocrine pancreatic acini.
More than one million islets in the human pancreas, predominantly found in the tail region.
Structure:
- Surrounded by a fine capsule of reticular fibers, separating from exocrine tissue.
- Parenchyma features lightly stained, polygonal or rounded cells organized in cords, interspersed with fenestrated blood capillaries.
Four cell types identified using immunocytochemistry: A, B, D, and F cells.
Ultrastructural features:
- Cells exhibit characteristics of polypeptide synthesizing (APUD) cells.
- Contain rER, well-developed Golgi apparatus, and specific secretory granules, with large vesicular nuclei.
Cell types in Islets of Langerhans:
- A Cells (α cells):
  - Comprise around 20% of islet cells, located mostly at the periphery.
  - Produce glucagon, which increases blood glucose levels by converting glycogen to glucose.
- B Cells (β cells):
  - Make up about 70% of islet cells, found centrally.
  - Produce insulin, lowering blood glucose levels by converting glucose to glycogen.
- D Cells: Additional unspecified functional characteristics.