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COPY: Parathyroid Quiz 1

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40 Questions

What is the primary function of calcitriol, the active form of vitamin D?

To increase calcium absorption in the gastrointestinal tract

Which of the following best describes the relationship between parathyroid hormone (PTH) and the kidneys?

All of the above

Which of the following cell types is responsible for the destruction and reabsorption of bone tissue?

Osteoclasts

What is the primary function of calcitonin, a hormone produced by the thyroid gland?

To counter the effects of parathyroid hormone (PTH) and decrease ionized calcium levels in the blood

Which of the following is the primary source of vitamin D2 for humans?

Dietary sources only, as vitamin D2 cannot be produced within the body

What is the primary function of osteoblasts in bone metabolism?

To create bone tissue and matrix

How does parathyroid hormone (PTH) affect the kidneys' role in vitamin D metabolism?

PTH stimulates the kidney enzyme 1-alfa-hydroxilase to convert calcidiol to calcitriol

Which cell type is responsible for the biomineralization process and maintenance of bone tissue?

Osteocytes

What is the role of chief cells in the parathyroid gland?

Secrete PTH

Where is pre-prohormone synthesized in the parathyroid gland?

By rER

What triggers the release of PTH from the parathyroid gland?

Low levels of ionized calcium

Where does PTH have a direct impact on metabolism?

Bones

Which hormone is NOT involved in maintaining calcium homeostasis?

Aldosterone

What are the actions of oxphil cells in the parathyroid gland?

oxidative and hydrolytic enzymatic activity

What is the role of calcitriol in calcium metabolism?

Regulates blood calcium levels

What happens when calcium and phosphate levels are imbalanced?

Body takes calcium from bones

What is the primary effect of decreasing calcium movement from bones to the ECF?

Inhibits osteoclast reabsorption

Which hormone is released in response to excessive calcium absorption in the intestines?

Calcitonin

What is the main role of calcitriol in calcium regulation?

Promotes active transport of dietary calcium across intestinal epithelium

How do hind gut fermenters regulate blood calcium levels?

Decreasing or increasing urine loss of calcium

Which of the following is a direct effect of increasing phosphate movement into bones from the ECF, due to calcitonin?

Increased calcium storage in bones

What is the consequence of insufficient calcitriol in animals?

Inadequate support for bone structure

Which hormone indirectly affects calcium levels by acting on the GI tract?

PTH

In hind gut fermenters, what is a unique characteristic of their urine when regulating calcium?

"Chalky white" appearance

What is the primary cause of primary hyperparathyroidism?

Abnormal chief cells within the parathyroid gland

How does primary hyperparathyroidism impact the kidneys?

Leads to polydipsia and polyuria

What is a common symptom of primary hyperparathyroidism related to the urinary system?

Crystalluria

How does primary hyperparathyroidism affect the excitability of the PNS/CNS?

Decreases excitability

What is a potential cardiovascular manifestation of primary hyperparathyroidism?

Bradycardia

How is primary hyperparathyroidism typically diagnosed?

Urinalysis (crystalluria)

In horses, what is another term for secondary hyperparathyroidism?

"Big Head Disease"

"Nutritional secondary hyperparathyroidism" is a condition in horses resulting from:

"Hyper mobilization of calcium from the skeleton under the influence of PTH"

What is the main cause of Nutritional Metabolic Bone Disease (NMBD) in reptiles and amphibians?

All of the above

What is the main function of oxalates in the diet of reptiles and amphibians?

Oxalates prevent the digestion and absorption of calcium

What is the alternative name for Nutritional Metabolic Bone Disease (NMBD) in reptiles and amphibians?

Nutritional secondary hyperparathyroidism (NSHP)

What is the main cause of hypoparathyroidism in reptiles and amphibians?

Idiopathic destruction of the parathyroid gland

What is the effect of low PTH levels in reptiles and amphibians?

Decreased calcitriol production, hypocalcemia, and hyperphosphatemia

What is the main symptom of severe hypoparathyroidism?

All of the above

How is hypoparathyroidism diagnosed in reptiles and amphibians?

Serum biochemistry showing hyperphosphatemia, decreased calcium, and undetectable PTH

What is the main cause of Nutritional Secondary Hyperparathyroidism (NSHP) in reptiles and amphibians?

All of the above

Study Notes

Vitamin D and Calcium Metabolism

  • Calcitriol, the active form of vitamin D, plays a primary role in calcium metabolism.
  • Vitamin D2 is primarily sourced from mushrooms and fortified dairy products for humans.

Parathyroid Hormone and Kidneys

  • Parathyroid hormone (PTH) stimulates the kidneys to convert vitamin D into calcitriol, which in turn regulates calcium levels.

Bone Metabolism

  • Osteoclasts are responsible for destroying and reabsorbing bone tissue.
  • Osteoblasts are responsible for building new bone tissue.
  • Osteocytes are responsible for maintaining and regulating bone tissue through biomineralization.

Parathyroid Gland Functions

  • Chief cells in the parathyroid gland produce pre-prohormone, which is then converted into PTH.
  • PTH is released in response to low calcium levels in the blood.
  • PTH directly affects the kidneys, increasing vitamin D metabolism and calcium reabsorption.

Calcium Regulation

  • Calcitriol plays a crucial role in regulating calcium levels by increasing absorption in the intestines.
  • Calcitonin, produced by the thyroid gland, lowers calcium levels by promoting bone storage.

Imbalance and Disorders

  • Imbalanced calcium and phosphate levels can lead to various disorders, such as osteoporosis, osteomalacia, and rickets.
  • Insufficient calcitriol in animals can lead to rickets and osteomalacia.
  • Primary hyperparathyroidism is caused by excessive PTH production, leading to bone resorption, kidney stones, and cardiovascular issues.
  • Secondary hyperparathyroidism in horses, also known as nutritional secondary hyperparathyroidism, is caused by a diet lacking in calcium and vitamin D.

Reptiles and Amphibians

  • In reptiles and amphibians, Nutritional Metabolic Bone Disease (NMBD) is caused by a diet lacking in calcium and vitamin D.
  • Oxalates in the diet can prevent calcium absorption, exacerbating NMBD.
  • Hypoparathyroidism in reptiles and amphibians is caused by a lack of PTH, leading to muscle cramps, seizures, and death.
  • Hypoparathyroidism is diagnosed through blood work and radiographs.

Test your knowledge of parathyroid anatomy and hormone synthesis in different species. Learn about the chief cells that secrete PTH and the oxphil cells with unknown functions. Explore the chemical structure and synthesis process of parathyroid hormones.

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