Thymus Gland
One of the essential parts of the lymphatic system, which is located in the mediastinum beneath the sternum, is the thymus gland.
- The thymus stretches from the fourth intercostal gap of the vertebrae to the lower margin of the thyroid gland.
- Unlike other endocrine glands, the thymus gland is exclusively active prior to puberty. At puberty, the gland expands to its maximum size before being gradually replaced by adipose tissue.
- A vital component of the immune system, the thymus gland acts as a barrier against various diseases, cancers, and antigens.
- The thymus is particularly crucial for the adaptive or thymus-dependent arm of the immune system since it is necessary for the growth and activation of immune cells.
- The thymus contains immune cells such as macrophages, neutrophils, and dendritic cells in addition to secretory cells.
- Cytokines like tumour necrosis factor (TNF) and interferon sustain the growth of the secretory cells and the control of their secretions.
- Autoimmune conditions like myasthenia gravis can affect the anatomy and operation of the gland.
Structure of Thymus Gland
- The thymus gland is a bilobed gland with two pyramid-shaped lobes, each of which has a surface that is lobulated and has two distinct regions: the outer cortex and the inner medulla.
- An interior connective tissue septum and a thick connective tissue capsule surround and separate each of the gland’s lobes.
- An intricate three-dimensional network of star-shaped reticular cells makes up the majority of the gland’s mass.
- Based on many characteristics, including antigenic expression, ultrastructure, and the ability to create thymic hormones, the epithelial cells of the thymus gland are categorised into four main subtypes.
- Subcapsular cortical, inner cortical, medullary, and Hassall’s corpuscles are the subtypes.
- Loosely packed lymphocytes can be found in the gland’s outer cortex, while reticulocytes with abundant cytoplasm can be found in the medulla.
- Small bodies made up of concentric arrays of squamous cells are also present in the structure and are known as Hassall’s concentric corpuscles, Hassall’s bodies, or thymic corpuscles.
- Infants and early children have big thymuses, which reach their maximum size during puberty. After puberty, the gland gradually starts to consolidate so that adipose tissue can take its place.
- The inferior thyroid, internal thyroid, and intercostal arteries all give blood to the thymus gland.
- Sternohyoid and sternothyroid muscles, both of which are bilateral, link the gland to the sternum.
What is Thymus Gland?
A gland in an animal is a collection of cells that produce compounds, such as hormones, for release into the bloodstream (endocrine gland), into cavities inside the body, or onto the animal’s surface (exocrine gland). Each gland is created by the ingrowth of epithelial tissue. This ingrowth may initially have a tubular form, but glands can also begin as a solid column of cells that later develops into a tubular structure.
The column of cells may divide or release offshoots as growth progress, in which case a compound gland is created. Many glands have a finite number of branches, whereas others (such as the pancreas and salivary glands) repeatedly expand and divide to eventually form a very massive structure. Normally, the branches don’t join together, but the liver is one exception since a reticulated compound gland develops there. The terminal portion of each branch in compound glands is made up of the more common or secretory epithelium, and the connecting segments, which ducts, are lined with a less altered type of epithelial cell.