The main difference between follicular and parafollicular cells is that follicular cells secrete thyroxine (T4) and triiodothyronine (T3) , which are responsible for regulating the body's metabolism. Meanwhile, parafollicular cells secrete the hormone calcitonin , which is responsible for regulating the body's calcium levels. In addition, follicular cells are the major cell type while parafollicular cells are the secondary cell type.
In short, follicular and parafollicular cells are the two types of cells found in thyroid tissue. The thyroid tissue is part of the thyroid , an endocrine gland that is located in front of the neck.
Key areas covered
1. What are follicular cells - definition, anatomy, function 2. What are parafollicular cells - definition, anatomy, function 3. What are the similarities between follicular and parafollicular cells - overview of the common characteristics 4. What is the difference between follicular and parafollicular? Cells - Comparison of Key Differences
key terms
Calcitonin, follicle cells, parafollicular cells, thyroid, thyroxine, triiodothyronine
What are follicular cells?
Follicular cells ( thyrocytes or thyroid epithelial cells) are the most important cell types of the thyroid gland. They form a simple cuboid epithelium that is arranged in spherical follicles that surround an interior space known as the follicular lumen. Here the follicle lumen is a fluid-filled space called a colloid. In addition, the basolateral membrane of the follicle cells contains thyrotropin receptors , which bind to the thyroid-stimulating hormone (TSH) circulating in the blood .
Figure 1: Synthesis of thyroid hormones
In addition, follicle cells take up iodide and amino acids to synthesize thyroglobulin and thyroperoxidase, which are then secreted into the thyroid follicles along with iodide. After oxidation, iodination and conjugation, thyroglobulin penetrates the follicle cells, which extract thyroid hormones and release them into the blood. Of these, the two types of thyroid hormones that release are thyroxine (T4) and triiodothyronine (T3). In addition, a normal thyroid produces about 80% T4 and about 20% T3, but T3 is about four times as strong as T4. The main function of thyroid hormones is also to regulate the body's metabolism; the conversion of oxygen and carbohydrates into energy.
What are Parafollicular Cells?
Parafollicular cells, or C cells, are the neuroendocrine cells in the thyroid. They are also the subset of cells that are interspersed between follicular cells. Strictly speaking, they appear next to the thyroid follicles and are located in the connective tissue. In addition, parafollicular cells are larger than the follicular cells and their cytoplasm is pale in color compared to the cytoplasm of the follicular cells. Therefore, they have no direct contact with the follicle lumen.
Figure 2: Follicular and parafollicular cells
In addition, the main function of parafollicular cells is to secrete calcitonin, which regulates the body's calcium metabolism. Calcitonin lowers especially the calcium levels in the blood by inhibiting bone resorption by osteoclasts, proportional to the blood calcium concentration. In addition, parafollicular cells secrete several neuroendocrine peptides such as serotonin , somatostatin or CGRP in small quantities.
Similarities Between Follicular and Parafollicular Cells
- Follicular and parafollicular cells are the two types of cells found in the thyroid gland. Here the thyroid is an endocrine gland that is located in the front of the neck. It also consists of two connected clubs.
- In addition, the thyroid gland consists of spherical thyroid follicles that are lined with follicular cells (Thyrocytes) and occasionally parafollicular cells surrounding a lumen Contain colloid .
- In addition, both cell types produce and secrete hormones that are responsible for regulating the body's metabolism.
Difference Between Follicular and Parafollicular Cells
definition
Follicular cells refer to the major cell types in the thyroid that produce and secrete the thyroid hormones thyroxine (T4) and triiodothyronine (T3) . Parafollicular cells refer to the neuroendocrine cells in the thyroid that are primarily responsible for secreting calcitonin.
Abundance
Follicular cells are the major type of cells in the thyroid, while parafollicular cells are the subordinate cell type.
Appear
Follicular cells are also arranged in spherical follicles that surround the follicle lumen, while parafollicular cells are found next to the thyroid follicles and reside in connective tissue.
Contact to the follicle lumen
In addition, follicular cells have direct contact with the follicle lumen, while parafollicular cells have no direct contact with the follicular lumen.
ID
In addition, the cytoplasm of the follicular cells is strongly stained with H&E, while the cytoplasm of the parafollicular cells is stained lighter with H&E.
Releasing hormones
Follicular cells also secrete thyroxine (T4) and triiodothyronine (T3), while parafollicular cells secrete calcitonin.
function
Functionally , thyroxine and triiodothyronine regulate the body's metabolism, while calcitonin regulates calcium metabolism.
diploma
In summary, follicular cells are the most important cell types in the thyroid. They also occur around the thyroid follicle. In addition, follicle cells secrete two thyroid hormones. Essentially, it is thyroxine (T4) and triiodothyronine (T3) that are mainly responsible for regulating the body's metabolism. In contrast, parafollicular cells are the smaller cell types in the thyroid that are occasionally found in follicular cells. However, parafollicular cells secrete calcitonin, which regulates calcium metabolism. Hence, the main difference between follicular and parafollicular cells is the type of hormones secreted.
References:
1. "The thyroid." Johns Hopkins Medicine , The Johns Hopkins University, Available here.
Image courtesy:
1. "Synthesis of Thyroid Hormones" By Mikael Häggström. (Häggström, Mikael (2014). "Medical Gallery by Mikael Häggström 2014". WikiJournal of Medicine 1 (2). DOI: 10.15347 / wjm / 2014.008. ISSN 2002-4436. (CC0) via Commons Wikimedia 2. "Tiroides 03 100X ”By Andrea Mazza - Own work ( CC BY-SA 3.0 ) via Commons Wikimedia
