Anatomía e histologia glándulas PARATIROIDES explicado CLARAMENTE
Introduction and Overview
In this video, the speaker introduces the topic of parathyroid glands and their anatomy and histology. The primary focus is on understanding the structure and function of these glands in regulating calcium and phosphate metabolism.
Anatomy of Parathyroid Glands
- Parathyroid glands are small ovoid glands located on the posterior surface of the thyroid gland.
- Usually, there are four parathyroid glands, but they can vary in number and location.
- Their main function is to produce parathyroid hormone (PTH), which regulates calcium and phosphate metabolism.
- Different types of cells are found in the parathyroid glands, including principal cells, oxyphil cells, adipocytes, and connective tissue capsules.
Location of Parathyroid Glands
- The parathyroid glands are typically located on the posterior surface of the thyroid gland.
- They can also be found in other locations such as the mediastinum or near the carotid artery bifurcation.
- The superior parathyroid glands are situated near the junction between the thyroid cartilage and cricoid cartilage.
- The inferior parathyroid glands are located at the lower pole of the thyroid gland or sometimes in the superior mediastinum.
Relationship with Thyroid Gland
This section discusses the relationship between parathyroid glands and thyroid gland.
Relationship with Thyroid Gland
- The parathyroid glands are located on or within the thyroid gland.
- The thyroid gland consists of two lobes (left and right) connected by an isthmus.
- It is positioned between cervical vertebra C5 and thoracic vertebra T1.
- In some individuals, additional parathyroid glands may be present outside of or within the thyroid gland.
Mediastinal Location
This section explains the mediastinal location of parathyroid glands.
Mediastinal Location
- The mediastinum is divided into different spaces based on the structures it contains.
- The anterior mediastinum is located behind the sternum and in front of the heart.
- Parathyroid glands can sometimes be found in the superior mediastinum near the thymus gland or carotid artery bifurcation.
- The exact location of parathyroid glands can vary, and they may also be present in other areas within the mediastinum.
Blood Supply
This section discusses the blood supply to parathyroid glands.
Blood Supply to Parathyroid Glands
- The blood supply to parathyroid glands is similar to that of the thyroid gland.
- There are superior and inferior thyroid arteries that provide blood to these glands.
- The superior thyroid artery arises from the external carotid artery, while the inferior thyroid artery originates from a branch of the thyrocervical trunk, which itself is a branch of the subclavian artery.
- The inferior thyroid artery primarily supplies blood to the posterior pole of the thyroid gland, while the superior thyroid artery irrigates its anterior part.
- In some cases, a third middle thyroid artery may be present and has surgical significance.
Conclusion
In this video, we learned about parathyroid glands' anatomy and their relationship with the thyroid gland. We also discussed their location within or outside of the thyroid gland and their blood supply. Understanding these aspects is crucial for comprehending their role in regulating calcium and phosphate metabolism.
Arteries and Veins of the Parathyroid Glands
This section discusses the arteries and veins that supply blood to and drain blood from the parathyroid glands.
Arterial Supply
- The posterior part of the parathyroid gland is supplied by an artery called the inferior polar artery.
- The inferior polar artery is important because it supplies the posterior part of the gland, which is where the parathyroid glands are usually located.
- Additionally, some irrigation can also come from the superior thyroid artery and middle thyroid artery.
Venous Drainage
- The venous drainage of the parathyroid glands mainly occurs through parathyroid veins.
- These veins derive from the superior, middle, and inferior thyroid veins.
- The superior and middle thyroid veins drain into the internal jugular vein, while the inferior thyroid vein drains directly into the brachiocephalic trunk, which leads to the superior vena cava.
Histology of Parathyroid Glands
This section provides an overview of histological features observed in a biopsy of parathyroid glands.
Cellular Composition
- Parathyroid cells appear white in color because they do not stain easily due to their lipid content.
- Adipocytes are abundant in these glands and are responsible for hormone production.
- Oxyphil cells have a more prominent cytoplasm compared to other cell types. They have a smaller nucleus, are eosinophilic (pink-staining), and are surrounded by blood vessels.
Tissue Structure
- Parathyroid glands are embedded within a capsule of connective tissue.
- Tab-like structures called septa separate different areas within these glands.
Secretory Function
- The secretory function of parathyroid cells is not well understood.
- The main cells responsible for hormone production are the principal cells, which are abundant in the glands.
- Parafollicular cells, also known as oxyphil cells, have a less defined function but are located adjacent to the follicular cells.
Thyroid Gland Histology
This section focuses on histological features of the thyroid gland.
Follicular Cells and Colloid
- The thyroid gland consists of follicles filled with colloid.
- Tirocytes, or follicular cells, help produce thyroid hormones and form a cuboidal epithelium that surrounds the follicles.
- A special staining technique called PAS staining can be used to visualize these follicular cells and colloid.
Parafollicular Cells
- Parafollicular cells are located near the follicles and have a lower affinity for hematoxylin-eosin staining compared to other cell types.
- These cells release calcitonin, which plays a role in regulating calcium and phosphorus metabolism.
These notes provide an overview of the arterial supply, venous drainage, histology of parathyroid glands, and histology of thyroid glands.