ENDOCRINE SYSTEM THYROID

PARATHYROID

3/8/2016 Prof.J.Anbalagan

LEARNING OBJECTIVES

• Microstructure with functional correlations

• Structural changes in goiter conditions

• Microstructure of parathyroid with functional correlations

THRYROID GLAND

• Follicular cells-Endoderm

• Para follicular cells-neural crest cells

• Functioning starts 10th week of fetal life

• Stores hormones 10 months, releases in a steady flow for a long period

THYROID GLAND

• Functions altered in iodine

deficiency

• Structural changes in hypo and hyper functions – Colloidal goiter – Parenchymatus goiter

• Enlargement is a symptom in thyroid disorders

• Regulates- – Metabolism – Growth and development – Activity of Nervous system

THYROID FOLLICLE • Capsule/septa

• Follicles-size and shape

variable 0.02-9mm

• Cuboidal cell lining in resting phase

• Columnar cell during active phase

• Synthesis, store, release of T3 and T4 in steady flow for a longer period

• Follicular cells are TSH dependent

THYROID FOLLICLE

• Thyroid follicle

• Size and shape variable

• Filled with colloid-

– appears pink

• Lining follicular cells are simple cuboidal to columnar on a basement membrane

THYROID FOLLICLE

• Apex of the cells show microvilli projecting into the colloid

• Para follicular cells

C cells between follicular cells and basement membrane

FOLLICLE

PARAFOLLICULAR CELL

Ultra structure of follicular cells • Short microvillus

• Tight junctions

• rER at the basal portion

• Supra nuclear position Golgi

• Vesicles

• Lysosomes

• Colloidal droplets

Parafollicular cells

• Appears in single/groups

• Between basement membrane and follicular cells

• Thyro-calcitonin

• Lowers blood calcium level

Parafollicular cells

PARATHYROID GLAND

• Paired superior and inferior glands

• Parathormone

• regulates calcium and phosphate level in blood

Parathyroid gland

• Connective tissue capsule

• Cells arranged in cords and groups

• Sinusoids between the cells

• Different type of cells identified

• Chief cells

• Oxyphil cells

Parathyroid gland • Chief cells (Principle cells)

• Principle cells appear in

group

• Cytoplasm is stained lightly

• Scattered between the chief cells are oxyphil cells

• Oxyphil cells shows acidophilic cytoplasm

• Number increases after puberty

Oxyphil cells

CHIEF CELLS

Pineal gland

Pineal gland

• EPIPHYSIS

• Capsule/trabeculae

• Lobules shows indistinct group of cells with connective tissue

• Calcareous deposits in adult

• Known as brain sand (corpora arenacea)

Pineal gland

• Cell type – Parenchymal cell

• Shows process

• Pale staining

• pinealocytes

– Glial cell • Smaller in size

• Stains intensely

• Neuroendocrine function on gonadal function – Cycles of dark and light

– Secretion of melatonin

Assessment question

• Histological features of thyroid/parathyroid.

• Location of Para follicular cells and their functions