Lymphatic System Overview

Lymphatic System

• Part of the immune system, regulates body fluid levels and defends against infections
• Composed of lymph vessels, lymph nodes, lymphoid organs, and lymphoid tonsils

Lymph

• Colorless fluid circulating within lymphatic vessels, accompanying veins but not visible to the naked eye
• In the small intestine, fats are absorbed by intestinal epithelium and packaged into milky opaque lymph called chylomicrons, which is also known as chyle
• Begins as lymphatic capillaries

Lymphatic Capillaries

• Present in most areas of the body except the brain, bone marrow, epidermis, eyeball, and cartilage

Lymphatic Vessels

• Movement of lymph is controlled by adjacent muscle action, particularly skeletal muscles and arterial pulses
• Unidirectional flow is maintained by valves within the lymphatic vessels

Lymph Nodes

• Small masses of lymphoid tissue located along the path of lymphatic vessels
• Encapsulated, ranging in size from 0.1 to 2.5 cm long
• Function as filters for foreign substances and contain elements of the body's defense system, such as lymphocytes and macrophages
• Found in groups, both superficial to the skin and deep in other areas

Lymph Node Groups

• Cervical - Drain head and neck
• Axillary - Drain upper limb and breast
• Mediastinal - Drain thoracic organs
• Aortic - Drain abdominal organs
• Inguinal - Drain groin and lower limbs

Lymphatic Trunks and Ducts

• Right Lymphatic Duct - Drains lymph from the right side of the head and neck, right upper limb, right side of the thorax, and right upper abdominal wall
• Thoracic Duct - Drains lymph from the left side of the body

Thoracic Duct

• Largest lymphatic duct in the body
• Drains lymph from the lower limbs, pelvis, perineum, abdomen, left side of the neck, and left upper limb
• Length: 45 cm
• Course:
  • Originates from the upper end of the abdominal lymph trunks or cisterna chyli in front of the lower border of the last thoracic vertebra
  • Ascends through the aortic opening of the diaphragm into the thorax
  • Ascends in front of the vertebral column
  • Crosses gradually from right to left side of the median plane of the body in front of T5
  • Terminates at the angle of junction between the left internal jugular and left subclavian vein at the level of C7

Lymphoid Organs

• Parts of the body that produce lymphocytes:
  • Thymus gland
  • Tonsils
  • Spleen
  • Red bone marrow
  • Lymphoid follicles at the wall of the alimentary tract

Tonsils

• Lymphoid tissue located in the pharynx and oral cavity:
  • Pharyngeal tonsil (adenoid)
  • Palatine tonsils
  • Lingual tonsils

Thymus gland

• Central lymphoid organ involved in the early development of the immune system
• Well-developed at birth and grows until puberty
• Diminishes in size and is replaced by fibrous and adipose tissue later in life
• Composed of two unequal pyramidal lobes bound together by loose connective tissue

Spleen

• Largest lymphoid organ in the body
• Reddish-brown in color
• Pyramidal in shape
• Two ends, three borders, and two surfaces
  • Anterior end: Expanded, directed downwards and forwards, reaching the mid-axillary line
  • Posterior end: Rounded, directed upwards, backwards, and medially, resting on the upper pole of the left kidney
  • Superior border: Characteristically notched near the anterior end
  • Inferior border: Rounded
  • Intermediate border: Rounded, directed to the right
  • Diaphragmatic (lateral) surface: Convex and smooth, containing impressions from the 9th to 11th ribs
  • Visceral (medial surface: Contains three impressions for the stomach, splenic flexure of the colon, and renal area for the left kidney
• Hilum: Located on the visceral surface, transmits splenic vessels and nerves, and provides attachment for ligaments

This quiz covers the key components and functions of the lymphatic system, including lymphatic capillaries, vessels, and nodes. Discover how this part of the immune system regulates body fluid levels and defends against infections. Test your knowledge of lymph and its role in fat absorption.