LYMPHATIC SYSTEM

MUDr. Hisham El Falougy, PhD.hisham.elfalougy@fmed.uniba.sk

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

• Marginal zone

– 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