Micro of Endocrine Glands - Parathyroid Glands

Question 1

Gross anatomy of parathyroid glands

Answer 1

1. Next to thyroid
2. External parathyroid glands - sitting on capsule
3. Internal parathyroid glands - deep within prenchyma of thyroid gland

Question 2

Embryology of parathyroid gland

Answer 2

1. Endoderm
2. External parathyroids and internal parathyroids arise from pharyngeal pouches

Question 3

Parenchyma of parathyroid glands

Answer 3

• Oxyphil cells
  
  • Acidophilic
  • Filled with mitochondria
  • Cell # varies with species - increase in size and number as animal ages
  • Function unknown
• Principal cells = chief cells (NOT chief cells in stomach)
  
  • Main cell
  • Light or dark depending on functional state of activity
  • Produce parathyroid hormone (parathormone = PTH)

Question 4

Function of parathyroid gland

Answer 4

• Essential for life
• Produce parathormone (principal cells)
  
  • Polypeptide
  • Maintains normal blood calcium and phosphorus levels

Question 5

Control of PTH secretion; what does PTH stimulate?

Answer 5

• Decreased blood calcium stimulates PTH release to increase blood calcium levels and decrease blood phosphorous levels
• PTH stimulates:
  
  • Calcium resoprtion from bone (activates osteoclasts)
  • Increased calcium absorption from intestine
  • Decreased calcium loss in urine via kidney
  • Decreased reabsorption of phosphate in kidney to decrease blood phosphorous levels

Question 6

Net effect of PTH

Answer 6

• Raise blood calcium
• Lower blood phosphorous