LYMPHATIC SYSTEM
MUDr. Hisham El Falougy, PhD. [email protected] Unencapsulated lymphoid tissue • Lymphoid follicles (nodules) • Urinary tract • Digestive tract (Peyer’s patches) • Upper respiratory tract
Tonsils
• Palatine • Pharyngeal • Lingual • Pharyngeal circle of Waldeyer • Tonsilla tubaria SPLEEN
• Vascular and lymphoid tissue • Left hypochondrium (regio hypochondriaca sinistra) • 12 cm long, 7 cm broad (adult) • 80 – 300 g (adult)
SPLEEN
• Function – Phagocytosis (removal of particulate material including aging erythrocytes) – Pitting of red blood cells – Immune responses (humoral, cellular) – cytopoiesis
SPLEEN
• Diaphragmatic surface
– Convex and smooth
• Visceral surface
– Gastric, renal, colic and pancreatic impressions
– Hilum SPLEEN
• Superior border – Convex – Separating diapgragmatic surface from gastric impression • Inferior border – Separating diapgragmatic surface from renal impression – Lower margin of 11th rib
SPLEEN
• Posterior extremity
– Faces the vertebral column
• Anterior extremity
– Forms margin connecting the superior and inferior borders
– Related to the left colic flexure SPLEEN
• Peritoneum – Firmly adheres to the splenic capsule – Peritoneal folds (splenorenal ligament, gastrosplenic ligament) • Connective tissue trabeculae – Fibrous skeleton of spleen – Supporting delicate tissues of spleen (red pulp, white pulp) SPLEEN
• Surface anatomy
– Position assessed by percussion
– Dull area extends over the 9th to 11th ribs
– Should not go forward beyond the midaxillary line
– Normal spleen is not palpable SPLEEN
• Vessels and nerves – Splenic artery (branch of the coeliac artery) – In the splenorenal ligament divids into segmental branches – Enter hilum to supply splenic segments – Each artery ramifies in the trabeculae to supply parenchyma and capsule SPLEEN
• Vessels and nerves
– Minor veins pass from red pulp into the trabeculae
– Form segmental veins leaving the hilum to the splenorenal ligament
– The splenic vein drains directly into the hepatic portal vein SPLEEN
• Vessels and nerves – Lymphatics drain along the trabeculae – Pass out of the hilum into lymphatic vessels accompanying the splenic artery and vein – Splenic lymph goes to pancreatosplenic and coeliac lymph nodes – Sympathetic fibers from coeliac plexus (vasomotor) – Regulates blood flow through the spleen SPLEEN
• White pulp
– Lymphoid tissue
– B and T lymphocyte maturation an proliferation
– Adventitia of arterioles within trabeculae repalced by sheath of T lymphocytes (periarteriolar lymphatic sheath)
– Enlarged lymphoid follicles (Malpighian bodies) SPLEEN
• White pulp
– Enlarged lymphoid follicles (Malpighian bodies)
– Aggregations of B lymphocytes
– At terminal branches of arterioles
– Germinal centers after antigen stimulation
– Penicilli (terminal branches of arterioles)
SPLEEN
• Red pulp
– Filtration device
– Complex system of interconnected spaces
– Phagocytic macrophages
– 75% of spleen
SPLEEN
• Red pulp
– Venous sinuses (50µm in diameter) draining into the
tributaries of the splenic veins
– Reticulum (fibrocellular network)
– Splenic cords (of Billroth)
SPLEEN
– Loosly arranged lymphocytes
– Small aggregation of macrophages (periartetiolar macrophage sheath)
• Fibrous framework
– Capsule (1.5mm thick)
– trabeculae
SPLEEN
• Splenic hypertrophy
• Splenomegaly
• Hymolytic diseases
• splenectomy
Thymus
• Primary lymphoid organ
• Thymus-processed lymphocytes (T lymphocytes)
• Immune tolerance to the body’s own components
• Neuroendocrine axis of the body Thymus
• Largest up to age of 15 years
• Active into old age
• Pyramidal shape, red and firm in children
• Thin, gray, yellow in adult
• Two lobes
• 20g (at birth 10-15g)
Thymus
• Superior and anterior inferior mediastinum
• Level of 4th costal cartilage (lower border)
• Extends to neck
• Anterior: sternum, 4 upper ribs, sternohyoid, sternothyroid
• Posterior: pericardium, aortic arch, left brachiocephalic vein, trachea Thymus
• Vessels
– Arteries: from internal thoracic and inferior thyroid arteries
– Veins: drain to the left brachiocephalic, internal thoracic and inferior thyroid veins Thymus
• Innervation
– Sympathetic from stellate (cervicothoracic) ganglion
– Parasymphathetic from vagus nerve
– Autonomic nerves are vasomotor
– Capsule of thymus recieves fibers from the phrenic nerve Thymus
• Outer cortex
– Densely packed cells (T lymphocytes)
– Outer cortical region(subcapsular)
• Inner medulla
– Rich in connective tissue
– Fewer lymphoid cells Thymus
• Capsule
– Losse connective tissue
– Septa penetrate to the junction of the cortex and medulla Thymus
• Cells of the mononuclear phagocyte system
• Fibroblasts
• Myoid cells
• Lymphocyte population (thymocytes)
• Thymic heamopoiesis