Week 3: Thyroid gland Microanatomy

Question 1

Cell types of thyroid gland

Answer 1

1. Follicular cells (endoderm): 98-99%
2. parafollicular cells (endoderm): make calcitonin
   - called C cells
   - fxn: antagonist to parathyroid hormone, lowers blood Ca levels by suppressing bone resorption and increasing rate of osteoid calcification

Question 2

morphological changes in histology in response to functional state changes: hyper/hypothyroidism

Answer 2

1. Hyperthyroidism
   - increased rER, microvilli, mitoses, vascularity
   - tall cell height
   - reduced/absent colloid
   - many intracellular colloid droplets
2. Hypothyroidism
   - decreased rER, microvilli, vascularity, no mitoses
   - flat cell height
   - increased colloid, no intracellular colloid droplets

Question 3

parathyroid gland

Answer 3

• source of parathyroid hormone (PTH), which regulates by increasing blood calcium
• glands are surrounded by connective tissue capsule
• chief cell: dominant cell type. produce PTH. respond directly to plasma calcium levels
• oxyphil cell: no known function, cell with cytoplasm filled with mitochondria