Study Guide for Histology of Thyroid Gland

 Stroma:

a) Thin fibrous connective tissue (CT) capsule

b) Trabeculae/ septa:

- contains Blood + Lymph + Nerve (BLN)  -> (highly vascularize to release hormones to blood)

- divides gland into well-defined lobules:

c) Lobules:

- surrounded by interlobular CT

- each lobule consists of thyroid follicles

- each thyroid follicle surrounded by interfollicular CT (sparse reticular CT)

 

Thyroid Gland Drawing

 

 

Parenchyma:

1. Consists of thyroid follicles

2. Thyroid follicle is the functional unit of the thyroid gland

3. Each thyroid follicle is lined by:

a. Follicular cells (thyrocytes)

b. Parafollicular cells (C-cells)

4. Each thyroid follicle is filled with colloid

5. Colloid is:

- Gelatinous acidophilic glycoprotein

- Contain thyroglobulin (precursor of the thyroid hormone)

- Secrete thyroxine (T3 + T4)

 

Thyroid Lobule

 

 

a. Follicular Cells

 

I. General histological features of follicular cell

a. Shape - squamous/ cuboidal/ tall cuboidal (columnar)

b. Cytoplasm - basal basophilic (due to containing high amount of rER + Golgi complex)

c. Nucleus - spherical with 1 or > prominent nucleoli

Single Follicular Cell Drawing

 

II. Comparison between active and inactive thyroid follicles

 Features Active Gland Inactive Gland 
 Shape

- Cuboidal cells (moderately active)

- Tall cuboidal/ Columnar cells (highly active)		  Squamous cells
Size - Small follicles - Large follicles
 Colloid

 

- Little amount/ absent

- Present of resorption lacunae

 

*Resorption lacunae:

Areas where colloid is being actively reabsorbed into follicular cells

 

- Abundant

- Appear solid
 Diagram Active Thyroid Follicile Inactive Thyroid Follicle 

 

b. Parafollicular cell (C-cell)

i) Histological features:

- Size: Larger than follicular cells

- Cytoplasm: pale basophilic (due to little amount of rER + Golgi complex)

ii) Location:

- Can be found either solitary or in a cluster

- Always situated within basal lamina/ basement membrane

iii) Function:

- Secrete calcitonin responsible for calcium metabolism

 Parafollicular Cell

 

*Disclaimers: The color used in the drawings are for illustration purposes only and may not be an exact

representation of the actual color in the photomicrograph