Lymphatic System review Introduction Components Lymph is

Lymphatic System (review)

Introduction Components Lymph is the fluid Vessels – lymphatics Structures & organs Functions Return tissue fluid to the bloodstream Transport fats from the digestive tract to the bloodstream Surveillance & defense

The Lymphatic System

Lymphatics Originate as lymph capillaries Capillaries unite to form larger vessels Resemble veins in structure Connect to lymph nodes at various intervals Lymphatics ultimately deliver lymph into 2 main channels Right lymphatic duct Drains right side of head & neck, right arm, right thorax Empties into the right subclavian vein Thoracic duct Drains the rest of the body Empties into the left subclavian vein

Lymph Capillaries

Lymphatic Vessels

Main Channels of Lymphatics

Major Lymphatic Vessels of the Trunk

Lymph Tissue 3 types Diffuse lymphatic tissue No capsule present Found in connective tissue of almost all organs Lymphatic nodules No capsule present Oval-shaped masses Found singly or in clusters Lymphatic organs Capsule present Lymph nodes, spleen, thymus gland

Lymph Nodules

Lymph Nodes Oval structures located along lymphatics Enclosed by a fibrous capsule Cortex = outer portion Germinal centers produce lymphocytes Medulla = inner portion Medullary cords Lymph enters nodes through afferent lymphatics, flows through sinuses, exits through efferent lymhpatic

Lymph Node

Tonsils Multiple groups of large lymphatic nodules Location – mucous membrane of the oral and pharyngeal cavities Palatine tonsils Posterior-lateral walls of the oropharynx Pharyngeal tonsil Posterior wall of nasopharynx Lingual tonsils Base of tongue

Tonsils

Spleen Largest lymphatic organ Located between the stomach & diaphragm Structure is similar to a node Capsule present But no afferent vessels or sinuses Histology Red pulp contains all the components of circulating blood White pulp is similar to lymphatic nodules Functions Filters blood Stores blood

Spleen

Thymus Gland Location – behind the sternum in the mediastinum The capsule divides it into 2 lobes Development Infant – conspicuous Puberty – maximum size Maturity – decreases in size Function Differentiation and maturation of T cells

Thymus Gland

Function of the Lymphatic System Defense against harmful organisms and chemicals 2 types of defense Nonspecific Specific defense = immunity Humoral immunity involves B cells that become plasma cells which produce antibodies that bind with specific antigens. Cell-mediated immunity involves T cells that directly destroy foreign cells

Derivation and Distribution of Lymphocytes

Chapter 20 The Lymphatic and Immune systems Structures: Lymphatic vessels and lymph Lymphocytes Lymphoid tissue Lymphoid organs

Lymphatic System Consists of 2 semiindependent parts: Network of lymphatic vessels Function primarily to return fluid to the vascular system Various lymphoid organs and tissues scattered throughout the body Functions in immune defense

The flow of lymph 1 -way flow from tissue towards heart Lymph arises from extracellular fluid Lymph capillaries flow into ( ) Lymphatic vessels Through lymph nodes Lymph trunks Lymph ducts Subclavian veins heart

Lymph capillaries Closed-ended vessels Lined by endothelium 1 -way flaps into capillary Allows passage of tissue fluid, large proteins, bacteria, viruses, cancer cells, cell debris 20. 2 ab

Lymph capillaries Blind structures that collect Interstitial Fluid How do they differ from vascular capillaries? Permeability Connections Absent from bone, teeth, and CNS Why are they not necessary in these locations?

Lymph capillaries Found in all areas of blood capillaries except: Bone, teeth, bone marrow, CNS Lacteals – lymph capillaries in villi of small intestine transports fat (chyle) [compare with blood capillaries]

Lymph capillaries Lacteals Specialized lymphatic capillaries found in the villi of the intestinal mucosa Assist in the absorption of digested fats from the small intestine Contain a milky white lymph known as chyle

Lymphatic collecting vessels Similar structure to blood vessels but thinner (have the same 3 tunics as veins, 20. 3 but are thinner, have more internal valves, and anastomose more) Receive lymph from lymphatic capillaries Many valves Flow of lymph 1 -way valves (like veins) Surrounding skeletal muscle Tunica media

Lymph nodes Scattered in trunk Located along lymphatic vessels Cleanses lymph 20. 1 20. 3

Lymph node structure Support structures Capsule Afferent and efferent lymphatics Trabeculae Reticular fibers Hilus 20. 4 a

Lymph node structure Functional tissue Cortex Lymph nodules Lymph sinuses Macrophages Lymphocytes Medulla Lymph sinuses Lymph cords Lymph filter Afferent lymphatic Lymph sinuses Removal of unwanted material Efferent lymphatic 20. 4 a

Lymph Node Function Produce new B and T cells Filter lymph

Lymph trunks Lumbar trunks Intestinal trunks Bronchomediastinal trunks Subclavian trunks Jugular trunks Formed from the union of the largest of the lymphatic collecting vessels Drain large areas of the body 20. 3

Lymph ducts Thoracic (L) lymphatic duct Drains ¾ of lymph L head, neck, thorax, upper extremity R&L abdomen, lower extremities Right lymph duct R head, neck, thorax, upper extremity Ducts drain into subclavian veins 20. 6 a

Lymph ducts

Lymph ducts

Lymphostasis

The immune system Main defense against disease Includes Lymphocytes Lymphoid tissue Lymph organs

Lymphoid Cells Lymphocytes What are the 2 types? What are plasma cells? What do they secrete? Lymphoid macrophages What is their function? Reticular cells Fibroblastlike cells that produce the reticular fiber stroma – the network that supports other cell types in lymphoid organs

Lymphocytes Attack antigens B lymphocytes produce Ab T lymphocytes destroy antigenbearing cells

Lymphocyte Activation

Lymphoid tissue MALT – mucosa-associated lymphoid tissue In mucous membrane Digestive system Respiratory system Urinary system Reproductive tract B and T lymphocytes B lymphocytes form lymph nodules with germinal centers 20. 8 ab

Lymphoid tissue 2 main functions: Houses and provides a proliferation site for lymphocytes Provides an ideal site for surveillance. Composed largely of reticular connective tissue and lymphoid cells Can be found as: Diffuse lymphatic tissue Scattered reticular tissue and lymphoid cells found in most organs and especially prominent beneath mucous membranes Lymphoid Follicles Spherical, tightly packed bodies of reticular and lymphoid cells Lymphoid Organs

Lymphoid organs Lymph nodes Spleen Thymus Tonsils 20. 3, 20. 9

Lymph nodes Filter lymph B lymphocytes Produced in germinal center T lymphocytes Mature at corticomedullary junction 20. 4 a

Lymph nodes Primary lymphoid organ – 100 s of them Cluster along lymph vessels Large clusters are found in the axillary, inguinal, and cervical regions 2 functions: Filter lymph – remove microorganisms and debris Activate the immune system

Lymph Node Structure Bean shaped and about 1” in length Each is surrounded by a dense fibrous CT capsule Trabeculae (strands of CT from the capsule) extend inward to compartmentalize the node What type of fibers are these trabeculae? Functional tissue consists of 2 main regions: Cortex Medulla

Cortex Superficial portion is packed with follicles – containing multiple B lymphocytes Deeper portion contains T lymphocytes Medulla Contains medullary cords which are inward extensions of cortical lymphoid tissue What cells do they contain? Large lymph capillaries known as medullary sinuses are also present Lymph Node Structure

Lymph Node Function Multiple afferent lymphatic vessels enter a lymph at its hilus - the indented region on the concave side Lymph percolates thru the node and it is scrutinized by macrophages and lymphocytes ready to mount an immune response Lymph leaves via a few efferent lymphatic vessels Lymph usually has to pass thru several nodes before it is “clean” Why is it significant that there are more afferent than efferent lymphatic vessels?

Other Lymphoid Organs Includes: Spleen Thymus Tonsils Peyer’s Patches All contain reticular CT and lymphocytes, but none of them actively filter lymph Where does lymph filtration occur? These other lymphoid organs contain efferent but no afferent lymphatic vessels. Why?

Largest lymphoid organ. About the size of a fist. Location: Spleen Left side of the abdominal cavity, just beneath the diaphragm and curling around the anterior stomach • Served by the splenic artery and vein which enter at its hilus • Surrounded by a fibrous CT capsule with inward extending trabeculae

Spleen Supporting tissue Capsule Hilus Splenic artery Trabeculae Trabecular arteries Functions include: Extracting old & defective RBCs and removal of debris and foreign matter from blood Storage of blood platelets and iron

Internal structure consists of: White Pulp Smaller portion Islands of lymphocytes and reticular fibers Red Pulp Venous sinuses and splenic cords (regions of reticular fibers and macrophages)

Spleen Functional tissue: Smaller portion White pulp Islands of lymphocytes and reticular fibers Lymphocytes around central arteries Branches of trabecular arteries Immune response to antigens Produces both B & T lymphocytes

Spleen Red pulp Venous sinuses and splenic cords (regions of reticular fibers and macrophages) Venous sinuses (splenic sinusoids) Splenic cords Lymphocytes Reticular fibers Macrophages Cleanse blood Remove old rbcs

Thymus Located in thorax Found in inferior neck and anterior thorax Posterior to sternum Supporting structures Capsule Trabeculae

Thymus Secretes hormones that allow T lymphocyte maturation Prominent in newborns, it increases in size throughout childhood. In adolescence, it begins to atrophy and is fatty/ fibrotic in adults. Only lymphoid organ that does not fight antigens

Thymus Functional tissue - lobules Site of T lymphocyte development Most active during childhood Decreases from adolescence to adult 20. 10

Tonsils Aggregations of lymphocytes and lymph nodules MALT – mucosa associated lympoid tissue

Tonsils Form a ring of lymphoid tissue around the entrance to the pharynx 3 main sets: Palatine Located on either side of the posterior oral cavity Largest and infected most often Lingual Lie at the base of the tongue Pharyngeal Found in the posterior wall of the nasopharynx Called adenoids when infected

Tonsils Palatine tonsils – in pharynx, near palate Lingual tonsils – in tongue Pharyngeal tonsils – in pharyngeal roof 21. 3 a

Contain multiple lymphoid follicles overlain by epithelial crypts Crypts trap bacteria which work their way into the lymphoid tissue where they are destroyed Why is this a risky method of fighting pathogens? What advantage does this method confer? Tonsils

Метастаз Вирхова Метастаз Шницлера Метастаз Крукенберга

Лу первого этапа Лу второго этапа Лу третьего этапа