Lymphatic and immune systems

Lymphatic and Immune SystemsLymphatic and Immune SystemsDragan NikolicDragan Nikolic

The lymphatic systemThe lymphatic system has at least three three different functionsdifferent functions:

– Serves to maintain the fluid balancemaintain the fluid balance of our internal body environment

– Serves as part of our immune systempart of our immune system

– Helps regulate the absorption of lipidsabsorption of lipids from digested food in the small intestines and its transport to the large systemic veins

Components of the Lymphatic and Components of the Lymphatic and Immune SystemsImmune Systems

The immune systemThe immune system serves as an internal “security force” to deal with abnormal cells

– Repels and destroys microorganismsmicroorganisms

– Defends us from our own abnormal cells that can cause cancercancer

Components of the Lymphatic and Components of the Lymphatic and Immune Systems Immune Systems (Cont’d)(Cont’d)

Overview of the Lymphatic SystemOverview of the Lymphatic System

– The lymphatic system solves the problem of fluid retention in tissues

• Acts as a drainage systemdrainage system• Collects excess tissue fluid and return it to the venous

blood just before it reaches the heart

– Lymphatic system is a part of the circulatory system

• Consists of moving fluid derived from the bloodmoving fluid derived from the blood and tissue fluid, as well as a group of vessels that return the lymph to the blood

Lymphatic SystemLymphatic System

Lymphatic vessels do not Lymphatic vessels do not form a closed system of form a closed system of vesselsvessels

• They begin blindlyblindly in the intercellular spaces of the soft tissue of the body

Lymphatic System Lymphatic System (Cont’d)(Cont’d)

Lymph and Interstitial FluidLymph and Interstitial Fluid

– LymphLymph – clear fluid found in the lymphatic vessels

– Interstitial fluidInterstitial fluid – complex fluid that fills the spaces between the cells

– Both fluids closely resemble blood plasmaresemble blood plasma in composition

– Difference is that lymph cannot clot like bloodlymph cannot clot like blood


Lymphatic VesselsLymphatic Vessels– Lymphatic vessels – microscopic blind-ended

lymphatic capillaries; wall of each lymphatic capillary consists of a single layer of flattened endothelial single layer of flattened endothelial cellscells

• Networks of lymphatic capillaries branch and then rejoin repeatedly to form a network throughout the interstitial spaces of our bodies

• Lymphatic capillaries merge to form larger and larger vessels until main lymphatic trunks are formed – right lymphatic ductright lymphatic duct and thoracic ductthoracic duct


Structure of lymphatic vesselsStructure of lymphatic vessels• Walls of lymphatic capillaries

– Have numerous openings or clefts between the cells

– As lymph flows from the thin-walled capillaries into vessels with larger diameters, the walls become thicker

• Eventually these larger vessels have the three layers typical of arteries and veins

• One-way valves are abundant in lymphatic vessels of all sizes


Function of lymphatic Function of lymphatic vesselsvessels

• Permeability of the lymphatic capillary wall permits very large molecules and even small particles to be removed from the interstitial spaces


Circulation of LymphCirculation of Lymph

–About 50% of the total blood protein leaks out of the capillaries into the interstitial fluid; ultimately returns to the blood by way of the lymphatic vessels


The lymphatic pumpThe lymphatic pump• Lymph moves slowly and steadily along in its

vessels into the general circulation at about 3 liters per day

– Lymph flow is possible because of the large number of valves that permit fluid flow only in the general direction toward the heart

– Breathing movements and skeletal muscle contraction aid in this motion


Lymph NodesLymph Nodes– Structure of lymph nodesStructure of lymph nodes

• Oval-shaped or bean-shaped structures; widely distributed throughout the body

• Lymph nodes are linked together by the lymphatic vessels

• Fibrous partitions or trabeculae extend from the covering capsule toward the center of a lymph node, creating compartments called cortical nodules

• Center, or medulla, of a lymph node is composed of sinuses; separate medullary cords composed of plasma cells and B cells


Locations of lymph nodesLocations of lymph nodes

– Most lymph nodes occur in groups, or clusters– Approximately 500-600 lymph nodes are located in the

body

Functions of lymph nodesFunctions of lymph nodes

– Defend our bodiesDefend our bodies from invading pathogens; sites of both biological and mechanical filtration

– Provide sites for the maturationmaturation of some types of lymphocytes


Structure and Function of the TonsilsStructure and Function of the Tonsils– TonsilsTonsils – form a protective ring under the mucous

membranes in the mouth and back of the throat• Protect against bacteria that may invade tissue in the area

around the openings between the nasal and oral cavities; first line of defense from the external environment

– Tonsils:Tonsils:– PalatinePalatine – located on each side of the throat– Pharyngeal tonsils (adenoids)Pharyngeal tonsils (adenoids) – lie near the

posterior opening of the nasal cavity– Lingual Lingual – lie near the posterior opening of the nasal

cavity


Structure and Function of Structure and Function of Aggregated Lymphoid NodulesAggregated Lymphoid Nodules

– Also called Peyer patchesPeyer patches – small, oval patches or groups of lymph nodes that form protective layer in mucous membrane of the small intestine

• Provide protection in a spot that is potentially open to external environment via the mouth

• Macrophages and other cells prevent most bacteria from penetrating the gut wall


Structure and Function of the ThymusStructure and Function of the Thymus– ThymusThymus – a primary organ of the lymphatic

system• Consists of two pyramid-shaped lobes• Located in the mediastinum, extending up into

the neck, close to the thyroid gland• Thymus plays a critical part in the body’s

defenses against infection• Soon after birth, thymus begins secreting a

group of hormones that enable lymphocytes to develop into mature T cells


Structure and Function of the SpleenStructure and Function of the Spleen– SpleenSpleen – located directly below the diaphragm, just

above most of the left kidney and behind the fundus of the stomach

• Roughly oval in shape

• Spleen has variety of functions:

– Defense– Hematopoiesis– Erythrocyte and platelet destruction– Reservoir for blood


Organization of the Immune SystemOrganization of the Immune System– Identification of cells and other particles:

• AntigensAntigens – cells, viruses, and other particles with unique molecules on their surfaces

– SelfSelf – Non-selfNon-self – molecules on the surface of foreign or

abnormal cells or particles that serve as recognition markers by our immune system

– Self-toleranceSelf-tolerance – ability of our immune system to attack abnormal or foreign cells while sparing our own cells

• Two categories of defense mechanisms:Two categories of defense mechanisms:– Innate immunity (Nonspecific) – Adaptive immunity (Specific)

Immune SystemImmune System

Innate (Non-specific) ImmunityInnate (Non-specific) Immunity

Phagocytosis and phagocytic cellsPhagocytosis and phagocytic cells

• PhagocytosisPhagocytosis – ingestion and destruction of microorganisms and other small particles by cells called phagocytesphagocytes

• Phagocytosis is classified as an innate defense• The most numerous type of phagocyte is the neutrophilneutrophil; other

types include macrophagesmacrophages and dendritic cells (DC)dendritic cells (DC)

Chemo-tactic factorsChemo-tactic factors cause neutrophils and other phagocytes to adhere to the endothelial lining of capillaries servicing the affected area

– After this, phagocytic cells squeeze through the wall of a blood vessel to get to the site of the injury or infection; diapedesisdiapedesis

Immune System Immune System (Cont’d)(Cont’d)

Innate (Non-specific) ImmunityInnate (Non-specific) Immunity

– Natural killer cellsNatural killer cells – provide important innate defensive functions for our bodies

• Kill many types of tumor cells and cells infected by different kinds of viruses

• Produced in the red bone marrow and make up about 15% of the total lymphocyte number

• Recognize markers on surface membrane of invading or defective cells


Adaptive immunityAdaptive immunity – involves mechanisms that program the body to recognize specific threatening agentsspecific threatening agents; specific immunity

• Primary types of cells involved in innate immunity:Primary types of cells involved in innate immunity:– Epithelial barrier cells– Phagocytic cells– Natural killer (NK) cells

• Primary types of cells involved in adaptive immunity:Primary types of cells involved in adaptive immunity:– T cells– B cells


Adaptive immunityAdaptive immunity – body’s third line of defense; provided by two different types of lymphocytes

• Two major classes of lymphocytes: –B lymphocytes (B cells)–T lymphocytes (T cells)

• B cells produce molecules called antibodiesantibodies that attack the pathogens or direct other cells, such as phagocytes, to attack them; antibody-

mediated immunity


B Cells and Antibody-Mediated ImmunityB Cells and Antibody-Mediated Immunity– Diversity of antibodiesDiversity of antibodies – every normal baby is born with an

enormous number of different clones of B cells

– Classes of antibodiesClasses of antibodies – five classes of immuno-globulinimmuno-globulin antibodies; identified by letter names as immunoglobulins M, E, G, A, M, E, G, A, and D D (USE MNEMONIC: MEGA-DMEGA-D)

• IgMIgM – antibody that immature B cells synthesize and insert into their plasma membranes

• IgGIgG – most abundant circulating antibody; cross-placental barrier during pregnancy to give passive immunity to baby

• IgAIgA – major class of antibody in the mucous membranes of the body; also in saliva and tears

• IgEIgE – produce the major symptoms of allergies and kill parasites• IgDIgD – small amount in blood; function unknown


Types of Adaptive ImmunityTypes of Adaptive Immunity

– Acquired immunityAcquired immunity – classified as either natural immunity or artificial immunity

• Natural immunityNatural immunity – results from non-deliberate exposure to antigens

• Artificial immunityArtificial immunity – results from deliberate exposure to antigens; immunizations


Types of Adaptive ImmunityTypes of Adaptive Immunity

– Natural and artificial immunity may be “active” or “passive

• Active immunityActive immunity – results when an individual’s own immune system responds to a harmful agent—regardless of how it was encountered

• Passive immunityPassive immunity – results when immunity to a disease that has developed in another individual is transferred to an individual who was not previously immune


• Hill, David J., (2012) Essentials of Anatomy and Physiology, Mosby, St. Louis. ISBN 9780323085113

• Metchnikoff, Elie; Translated by F.G. Binnie. (1905). Immunity in Infective Diseases (Full Text Version: Google Books). Cambridge University Press. ISBN 68025143

ReferencesReferences

Lymphatic and immune systems

Education

Transcript of Lymphatic and immune systems