thymus

Introduction

[Greek, thymos = excrescence, sweetbread]

Function

• role in immunological function throughout life.
• produces hormones, including thymosine that can continue to influence T-cells after they have left the gland

Structure

• a bilobed mass of pinkish gray lymphoid tissue located deep to the sternum, in the anterior region of the mediastinum.
• the thymus is covered by a connective tissue capsule that separates it into smaller lobules.
• each lobule has an outer cortex & an inner medulla.
  • cortex composed of densely packed lymphocytes
  • medulla composed of lymphocytes; also has thymic corpuscles

Innervation

• derived from the vagus & sympathetic nerves

Arterial supply

• inferior thyroid artery & internal thoracic artery

Pathology

• in some newborn infants, the thymus may also extend superiorly through the superior thoracic aperature into the neck & compress the trachea

Biochemistry

Transcription factors implicated in thymic development & function:

• FoxN1
• HoxA3
• Pax-1
• Pax-9
• Eya-1
• Six-1

⧼aaushi-heading-development⧽

• it increases in size during fetal life & early childhood.
• after puberty, it undergoes gradual involution & is largely replaced by adipose tissue.

More general terms

• organ

Additional terms

• thymic neoplasm

Component of

• lymphatic system
• thorax

Components

• thymic corpuscles (Hassall bodies, Hassall concentric corpuscles, Virchow-Hassall bodies, Hassall's corpuscles)