Lymphatic System Overview

Lymphatic System

• Protects the body from foreign material
• Aids in the circulation of body fluids between cells and the bloodstream
• Transports dietary fats
• Consists of lymph, a network of vessels, lymph nodes and nodules, tonsils, spleen, and thymus gland

Lymph

• Derived from tissue fluid
• Contains more white blood cells than plasma
• Enters lymph nodes through afferent lymphatic vessels
• Flows through the node in one direction
• Flows through sinuses in the cortex and medulla of lymph nodes
• Exits via efferent lymphatic vessels
• Must be returned to the bloodstream to maintain blood volume and pressure

Lymph Vessels

• Resemble veins but have thinner walls and more valves
• Lymph is kept moving by constriction of vessels, the skeletal muscle pump, and the respiratory pump
• Lymph flows into lymph nodes at intervals along the vessels
• Lymphatic vessels unite to form lymph trunks

Lymph Trunks

• Formed by the uniting of lymphatic vessels
• Large tubes
• Empty their lymph into lymphatic ducts

Lymphatic Ducts

• Lymph empties into two conducting ducts: the thoracic duct (left lymphatic duct) and the right lymphatic duct
• Lymph from these ducts enters the bloodstream via the left subclavian vein and the right subclavian vein

Thoracic Duct

• Approximately 38-45 cm in length
• Begins as a dilation called the cisterna chyli
• The main collecting duct of the lymphatic system
• Receives lymph from the lower body and upper left quadrant
• Empties into the left subclavian vein

Right Lymphatic Duct

• Approximately 1.5 cm in length
• Receives lymph from the upper right quadrant
• Empties into the right subclavian vein

Lymph Nodes

• Oval or bean-shaped masses of lymphatic tissue
• Aid in defense and white blood cell formation
• Located along the length of lymphatic vessels
• Scattered throughout the body, usually in clusters

Major Lymph Nodes

• Cervical (neck)
• Axillary (armpit)
• Inguinal (groin)
• Mesenteric (abdominal peritoneum)

Cervical Lymph Nodes

• Located in the neck area
• Filter lymph from the head and neck

Axillary Lymph Nodes

• Located in the armpits
• Filter lymph from the hand, arm, and breast

Inguinal Lymph Nodes

• Located in the groin area
• Filter lymph from the lower extremities and external genital organs

Mesenteric Lymph Nodes

• Located in the abdominal peritoneum
• Aid in infection control after abdominal surgery
• Filter lymph from the abdominal cavity

Metastasis

• Bacteria or body cells spread from one body part to another via the lymphatic or circulatory systems
• Cancer cells migrate to nearby nodes (e.g., breast cancer to axillary nodes)

Tonsils

• Aggregations of large lymphatic nodules embedded in mucous membranes
• Located beneath the epithelium of the pharynx and oral cavities
• Protect nasal and oral cavities
• Three types: nasopharyngeal, palatine, and lingual

Nasopharyngeal Tonsils

• Commonly called adenoids
• Located behind the nose, on the roof of the posterior pharynx wall, and the posterior opening of the nasal cavity

Palatine Tonsils

• Commonly called tonsils
• Located in the back of the mouth and on the lateral walls of the pharynx
• Frequently removed via tonsillectomy

Lingual Tonsils

• Located at the base of the tongue
• Part of the first line of defense against pathogens

Spleen

• Largest lymphatic organ
• Located in the upper left abdominal quadrant between the fundus of the stomach and the diaphragm
• Resembles a large lymph node
• Filters blood
• Contains a capsule, hilum, trabeculae, and pulp(red and white)

White Pulp

• Consists of lymphatic tissue
• Mostly lymphocytes arranged around central arteries

Red Pulp

• Consists of venous sinuses filled with blood and cords of splenic tissue
• Contains red blood cells, macrophages, lymphocytes, plasma cells, and granulocytes

Spleen Functions

• Phagocytoses bacteria and worn-out red blood cells and platelets
• Stores and releases blood in times of demand (e.g., hemorrhage)
• Functions in immunity as a site of B cell proliferation into plasma cells
• Does not filter lymph

Thymus Gland

• Two-lobed organ in the upper chest, inferior to the thyroid gland and posterior to the sternum
• Largest and most active during prenatal and infancy periods
• Decreases in size after puberty
• Composed of lymphatic tissue
• Subdivided into lobules
• Immature T cells develop into mature T cells via blood
• Thymic hormones aid in the maturation of T cells

Thymus Removal

• Decreases T-cell production
• Increased susceptibility to infection (thymectomy)

Spleen Removal

• Other organs (liver, bone marrow) can compensate
• Increased susceptibility to disease (splenectomy)

Mucosa-Associated Lymphoid Tissue (MALT)

• Mucosa-associated lymphatic tissue
• Infiltration of mucosa by large numbers of lymphocytes
• Example: Peyer's patches of small intestine

This quiz explores the lymphatic system, including its structure and function. It covers the roles of lymph, lymph vessels, and lymph trunks in protecting the body and maintaining fluid balance. Test your knowledge on how this essential system operates within the human body.