Chapter 23 Lymphoid system A parasite called filarial worm can lodge itself inside lymph vessel, blocking flow of fluid. Excessive edema may ensue, called elephantiasis.

Figure 23.1 Lymphoid System Tonsil Lymphatics of upper limb Cervical lymph nodes Right lymphatic duct Thymus Axillary lymph nodes Thoracic duct Thoracic (left lymphatic) duct Lymphatics of mammary gland Cisterna chyli Spleen Lumbar lymph nodes Mucosa-associated lymphoid tissue (MALT) Pelvic lymph nodes Inguinal lymph nodes Lymphatics of lower limb 2

Figure 23.2a Lymphatic Capillaries Smooth muscle Lymphatic capillary Arteriole Blood capillaries Endothelial cells Venule Loose connective tissue Interstitial fluid Lymph flow A three-dimensional view of the association of blood capillaries and lymphatic capillaries. Arrows show the direction of blood, interstitial fluid, and lymph movement. 3

Figure 23.2b Lymphatic Capillaries Lymphocyte Lymph flow Incomplete basal lamina To larger lymphatics Loose connective tissue Interstitial fluid Interstitial fluid Lymphatic capillary Blood capillary Sectional view through a cluster of lymphatic capillaries 4

Figure 23.3a Lymphatic Vessels and Valves Vein Artery Lymphatic vessel Lymphatic valve From lymphatic capillaries A diagrammatic view of loose connective tissue showing small blood vessels and a lymphatic vessel. Arrows indicate the direction of lymph flow. 5

blood capillaries  tissue fluid  lymphatic capillaries (lymph)  lymphatic vessels lymph nodes  lymphatic trunks  lymphatic duct venous blood stream.

Figure 23.4 Lymphatic Ducts and Lymphatic Drainage Left internal jugular vein Right internal jugular vein Left jugular trunk Right jugular trunk Brachiocephalic veins Thoracic duct Right lymphatic duct Left subclavian trunk Right subclavian trunk Left bronchomediastinal trunk Right subclavian vein Left subclavian vein Right bronchomediastinal trunk Superior vena cava (cut) First rib (cut) Highest intercostal vein Rib (cut) Thoracic duct Azygos vein Drainage of right lymphatic duct Thoracic lymph nodes Drainage of thoracic duct Hemiazygos vein Parietal pleura (cut) Diaphragm Inferior vena cava (cut) Intestinal trunk Right lumbar trunk Left lumbar trunk The thoracic duct collects lymph from tissues inferior to the diaphragm and from the left side of the upper body. The right lymphatic duct drains the right half of the body superior to the diaphragm. The collecting system of lymph vessels, lymph nodes, and major lymphatic collecting ducts and their relationship to the brachiocephalic veins 7

Figure 23.10 Lymphatic Drainage of the Head and Neck Orbicularis oculi muscle Periauricular lymph node Infraorbital lymph node Retroauricular lymph node Parotid salivary gland Buccal lymph node Occipital lymph node Mandibular lymph node Parotid lymph node Submental lymph node Superficial cervical lymph node Submandicular lymph node Deep cervical lymph node Sternocleidomastoid muscle 8

Figure 23.11 Lymphatic Drainage of the Upper Limb Deltoid muscle Deltopectoral lymph node Pectoralis major muscle Axillary lymph nodes Pectoralis major muscle (cut) Axillary vein Cephalic vein Subclavian lymph node Axillary lymph nodes Basilic vein Supratrochlear lymph node Central lymph node Subscapular lymph node Parasternal lymph node Pectoral lymph node Mammary gland Superficial lymphatic vessels and nodes that drain the upper limb and chest of a male Superficial and deeper lymphatic vessels and nodes of the upper limb and chest of a female 9

Figure 23.12 Lymphatic Drainage of the Lower Limb Superficial inguinal lymph nodes Deep inguinal lymph nodes Great saphenous vein Popliteal lymph nodes 10

Figure 23.14a Lymphatic Drainage of the Inguinal Region Inguinal ligament Femoral artery Deep inguinal lymph nodes Great saphenous vein An anterior view of a dissection of the inguinal lymph nodes and vessels 11

Figure 23.9 Structure of a Lymph Node (Part 1 of 2) Lymph vessel Lymph nodes Efferent vessel Lymph node artery and vein Hilum Lymph nodes Medullary sinus Trabeculae Medulla Outer cortex (B cells) Cortex Deep cortex (T cells) Capsule Medullary cord (B cells and plasmocytes) Afferent vessel 12

Figure 23.9 Structure of a Lymph Node (Part 2 of 2) Subcapsular space Germinal center Outer cortex Capsule Dividing B cell Capillary Dendritic cells Nuclei of B cells 13

Lymphocytes are produced and stored in which of the following? a. spleen and thymus b. lymph nodes c. tonsils d. the lacteals of the small intestine Answer: a

Figure 23.16a Anatomy and Histological Organization of the Thymus Thyroid gland Trachea THYMUS Right lobe Left lobe Left lung Right lung Heart Diaphragm The location of the thymus on gross dissection; note the relationship to other organs in the chest 15

Figure 23.16b Anatomy and Histological Organization of the Thymus Right lobe Left lobe Septa Lobule Anatomical landmarks on the thymus 16

Figure 23.17a Anatomy and Histological Organization of the Spleen Parietal peritoneum Visceral peritoneum Stomach Diaphragm Rib Gastrosplenic ligament Liver Pancreas Gastric area Aorta Diaphragmatic surface Spleen SPLEEN Hilum Renal area Kidneys The shape of the spleen roughly conforms to the shapes of adjacent organs. This transverse section through the trunk shows the typical position of the spleen within the abdominopelvic cavity (inferior view). 17

Figure 23.17b Anatomy and Histological Organization of the Spleen SUPERIOR Gastric area Hilum Splenic vein Renal area Splenic artery Splenic lymphatic vessel INFERIOR External appearance of the visceral surface of the intact spleen showing major anatomical landmarks. This view should be compared with that of part (a). 18

Spleen

Lymphoid Tissues Lymph nodules (no capsule) Tonsils MALT (mucosa associated lymphoid tissue)

Figure 23.8c Histology of Lymphoid Tissues How many tonsils are in the pharynx? Pharyngeal epithelium Pharyngeal tonsil Germinal centers within nodules Palate Palatine tonsil Lingual tonsil Pharyngeal tonsil LM  50 The location of the tonsils and the histological organization of a single tonsil 22

Ileum & Peyer’s Patch

a. capsule; megakaryocytes b. germinal center; erythrocytes Typical lymphoid nodules often have a pale central zone, called a ____, which contains activated, dividing ____. a. capsule; megakaryocytes b. germinal center; erythrocytes c. medulla; lymphocytes d. germinal center; lymphocytes Answer: d

a. declines; natural killer b. increases; T cells c. declines; tumor The increased incidence of cancer in the elderly reflects the fact that lymphoid surveillance ______, and ______ cells are not eliminated as effectively. a. declines; natural killer b. increases; T cells c. declines; tumor d. increases; antigens Answer: c