Unit 4: The Lymphatic and Immune Systems

Nursing Physiology (NRS237)

Dr. Moattar Raza Rizvi

• Lymphatic System: Returns Lymphatic System: Returns interstitial fluid and leaked interstitial fluid and leaked plasma proteins back to the plasma proteins back to the bloodblood

• Consists of two semi-independent parts– A meandering network of

lymphatic vessels– Lymphoid tissues and

organs scattered throughout the body

Lymphatic System: Overview

LymphLymph – interstitial fluid once it has entered lymphatic vessels

Lymphatic System: Overview

Lymphatic System: Overview

• Is straw colored fluid, similar in composition to blood plasma

• Lymph fluid bathes the surrounding spaces between tissue cells and it is referred to as interstitial fluid or tissue fluid

• Lymph fluid is made up of water, lymphocytes, granulocytes (neutrophils), O2, digested nutrients (proteins), sodium ions, hormones, salts, CO2 and urea

Lymph fluid

• Main structures of the lymphatic system– Lymphatic vessels

• Main components of the immune system– Lymph– Lymphocytes – Lymphoid Nodules (Tonsils)– Lymphoid Organs

Components of the Lymphatic System

Components of the Lymphatic System

• A one-way system in which A one-way system in which lymph flows toward the heartlymph flows toward the heart

• FLOW OF LYMPH TOWARDS THE HEART

• Blood capillaries (blood)> interstitial spaces (interstitial fluid)>lymphatic capillaries (lymph)> lymphatic vessels (lymph)>lymphatic ducts (lymph)>subclavian veins (blood)

Lymphatic Flow

• Similar to blood capillaries, with modifications– Remarkably permeable– Loosely joined endothelial minivalves– Withstand interstitial pressure and remain open

• The minivalves function as one-way gates that:– Allow interstitial fluid to enter lymph capillaries– Do not allow lymph to escape from the capillaries

Lymphatic Capillaries

How does blood capillary differ from lymphatic capillary

Lymphatic Capillaries

• During inflammation, lymph capillaries can absorb:– Cell debrisCell debris– PathogensPathogens– Cancer cells Cancer cells

• Cells in the lymph nodes:– Cleanse and “examine” this debris Cleanse and “examine” this debris

• During inflammation, lymph capillaries can absorb:– Cell debrisCell debris– PathogensPathogens– Cancer cells Cancer cells

• Cells in the lymph nodes:– Cleanse and “examine” this debris Cleanse and “examine” this debris

Lymphatic Capillaries

• Lacteals – specialized lymph capillaries present in the villi of the small intestines– Absorb digested fat and deliver chyle to the blood

Specialized Lymphatic Capillaries- Lacteals

• The walls of lymphatic vessels are similar to those of cardiovascular veins (have the same three tunics as veins)

• Have thinner walls, with more internal valves• Anastomose more frequently• Collecting vessels in the skin travel with superficial

veins• Deep vessels travel with arteries• Nutrients are supplied from branching vasa vasorum

Lymphatic Collecting Vessels

Write short notes on lymphatic collecting vessels

The walls of lymphatic vessels are similar to those of veins but have thinner walls and more valves.

Lymph vessels in the skin follow veins. Lymph vessels in the viscera follow arteries. Lymph vessels are NOT found in avascular tissue,

CNS, parts of spleen and red bone marrow.

Lymphatic Collecting Vessels

Lymphatic Trunks Large vessels lead to lymph

nodes and then to larger lymphatic trunks

Lymphatic trunks are named for the body region they drain

Lumbar trunk –drains lymph from lower limbs and pelvic organs

Intestinal trunk- drains abdominal viscera

Bronchomediastinal trunk- drains portions of the thorax

Subclavian trunk – drains upper limbs

Jugular trunk – drains portions of the neck and head

• Lymphatic trunks are formed by the union of Lymphatic trunks are formed by the union of the largest collecting ductsthe largest collecting ducts

• Major trunks include:– Paired lumbar, bronchomediastinal, subclavian, and

jugular trunks– A single intestinal trunk

• Lymph is delivered into one of two large trunksLymph is delivered into one of two large trunks– Right lymphatic duct Right lymphatic duct – drains the right upper arm

and the right side of the head and thorax– Thoracic duct Thoracic duct – arises from the cisterna chyli and

drains the rest of the body

Lymphatic Trunks

Lymph capillaries converge to become collecting vessels and end up as eitherThoracic duct or right lymphatic duct

Thoracic (left lymphatic) duct

Left subclavian vein

Right lymphatic

duct

Right subclavian

vein

Cysterna Chyli

Lymphatic Trunks

The right and left (thoracic duct) lymphatic duct empties directly into the left subclavian vein

Lymphatic Ducts

• The lymphatic system lacks an organ that acts as a pump

• Vessels are low-pressure conduits• Method to propel lymph: • Uses the same methods as veins

1. Pulsations of nearby arteries2. The main activity that causes fluid to flow through

lymphatic vessels is smooth muscle contraction in the walls of the lymphatics

Lymph Transport

• Lymphocytes are the main cells involved in the immune response

• The two main varieties are T cells T cells and B cellsB cells• T cells and B cells protect the body against

antigens• Antigen – anything the body perceives as foreign

– Bacteria and their toxins; viruses– Mismatched RBCs or cancer cells

Lymphoid Cells

• T cells (T lymphocytes): – Manage the immune

response– Attack and destroy

foreign cells

• B cells (B-Lymphocytes)– basic functional unit of the immune system– Produce plasma cells, which secrete antibodies– Antibodies immobilize antigens

Lymphoid Cells

Describe lymphoid cells

Lymphoid Cells

• MacrophagesMacrophages – phagocytize foreign substances and help activate T cells

• Dendritic cells Dendritic cells – spiny-looking cells with functions similar to macrophages

• Reticular cells Reticular cells – fibroblastlike cells that produce a stroma, or network, that supports other cell types in lymphoid organs

Other Lymphoid Cells

• Primary lymphatic organs - site of B and T cell production– bone marrow - produces B cells, pre-T cells– thymus gland – pre-T cells migrate to thymus gland

and mature in thymus gland

• Secondary lymphatic organs - site of most immune responses – lymph nodes, – spleen – surrounded by connective tissue capsule– lymphatic nodules – not surrounded by capsule

Lymphoid Organs

Differentiate between primary and secondary lymphatic organs

Lymphoid Organs

Lymphoid Organs1.Tonsils2.Appendix3.Bone marrow 4.Thymus gland5.Spleen 6.Lymph nodes, 7.Lymphatic nodules

• Nodes are bean shaped and surrounded by a fibrous capsule

• Lymph nodes are the principal lymphoid organs of the body

• Nodes are imbedded in connective tissue and clustered along lymphatic vessels

• Aggregations of these nodes occur near the body surface in inguinal, inguinal, axillary, and cervical regions of the axillary, and cervical regions of the bodybody

Only lymph nodes filter lymph

Lymphoid Nodes

Lymphoid Nodes

The breast tissue fluid will drain into the axillary nodes

The following cavity contain lymph node

• Abdominopelvic cavity• Thoracic cavity• Mediastinum

Cranial cavity is an area where lymph nodes is not present

Lymphoid Nodes

Lymphoid Nodes

• Their two basic functions are:– Filtration – macrophages destroy

microorganisms and debris– Immune system activation – monitor for

antigens and mount an attack against them

• Lymph vessels– Afferent lymphatic vessels– carrying fluid towards lymph node

– Efferent lymphatic vessels: – carrying fluid away from the lymph node

Lymphoid Nodes

Give the basic functions of lymph nodes

• Nodes have two histologically distinct regions: a cortex and a medulla

• The cortex contains follicles with germinal centers, heavy with dividing B cells

• Dendritic cells nearly encapsulate the follicles• The deep cortex houses T cells in transit• T cells circulate continuously among the blood,

lymph nodes, and lymphatic stream

Microscopic Anatomy of a Lymph Node

Largest lymphoid organ, located on the left side of the abdominal cavity beneath the diaphragm Function:

Immune function removal of worn out or damaged RBC’s storage of platelets production of RBC’s during fetal life

Lymphatic Tissue - Spleen

• Two distinct areas of the spleen are:

– White pulp – area responsible for producing lymphocytes suspended on reticular fibers and involved in immune functions

– Red pulp – remaining splenic tissue concerned with phagocytizing old or senescent RBCs and bloodborne pathogens

Lymphatic Tissue - Spleen

• A bilobed organ that secrets hormones (thymosin and thymopoietin) that cause T lymphocytes to become immunocompetent

– Located in pleural cavity between sternum, heart

– Composed of cortex and medulla

Thymus Gland

– The size of the thymus varies with age– It stops growing during adolescence and then

gradually atrophies– Largest lymphatic organ in a child is thymus

gland– It functions strictly in T lymphocyte maturation– It does not directly fight antigens

Thymus Gland

• Location of the tonsils– Palatine tonsils – either side

of the posterior end of the oral cavity

– Lingual tonsils – lie at the base of the tongue

– Pharyngeal tonsil – posterior wall of the nasopharynx

– Tubal tonsils – surround the openings of the auditory tubes into the pharynx

• Simplest lymphoid organs; form a ring of lymphatic tissue around the pharynx

Tonsils

• Peyer’s patches – isolated clusters of lymphoid tissue, similar to tonsils– Found in the wall of the distal portion of the small

intestine– Similar structures are found in the appendix

• Peyer’s patches and the appendix:– Destroy bacteria, preventing them from breaching

the intestinal wall– Generate “memory” lymphocytes for long-term

immunity

Aggregates of Lymphoid Follicles

• MALT – mucosa-associated lymphatic tissue is composed of:– Peyer’s patches, tonsils, and the appendix

(digestive tract)– Lymphoid nodules in the walls of the bronchi

(respiratory tract)• MALT protects the digestive and respiratory

systems from foreign matter

MALT

Lymphocytes are later also produced in thymus, spleen and tonsils

Bone Marrow: Lymphopoiesis

Immune System

Innate/Natural/ Nonspecific– Present from birth– Operates against any substance– Not enhanced by prior

exposure

Acquired/Adaptive/Specific– Defense mechanisms

tailored to individual pathogens

– enhanced by prior exposure

2 Type of Immunity: Innate & Acquired

• Innate (nonspecific) system responds quickly and consists of:– First line of defense – intact skin and mucosae

prevent entry of microorganisms– Second line of defense – antimicrobial proteins,

phagocytes, and other cells • Inhibit spread of invaders throughout the body• Inflammation is its hallmark and most important

mechanism

Immunity: Two Intrinsic Defense Systems

• Refers to various PHYSICAL, CHEMICAL, and CELLULAR attributes that collectively represent the first line of defense against infectious disease.

• Skin – acts as a physical barrier to invasion• Sweat – has chemicals which can kill different

pathogens. • Tears – have lysozyme protective chemical that lyses

cells• Saliva – also has lysozyme.• Mucus - can trap pathogens, which are then sneezed,

coughed, washed away, or destroyed by chemicals. • Stomach Acid – destroys pathogens• Lactic acid further decreases skin pH

Innate Immune System: First Line of Defense

• The body uses nonspecific cellular and chemical devices to protect itself– Phagocytes and natural killer (NK) cells– Antimicrobial proteins in blood and tissue fluid– Inflammatory response enlists macrophages,

mast cells, WBCs, and chemicals• Harmful substances are identified by surface

carbohydrates unique to infectious organisms

Internal Defenses: Cells and Chemicals

• Macrophages are the chief phagocytic cells• Free macrophages wander throughout a region in

search of cellular debris• Kupffer cells (liver) and microglia (brain) are fixed

macrophages• Neutrophils become phagocytic when encountering

infectious material• Eosinophils are weakly phagocytic against parasitic

worms• Mast cells bind and ingest a wide range of bacteria

Phagocytes

• Next line of defense (with phagocytes)• Lymphocytes – but do not respond to specific antigens• Can kill a variety of microbes plus tumor cells.• May release perforins, or attack directly• Cell may not display correct MHC antigens

Natural Killer Cells

CYTOKINE

A cytokine is a protein hormone which regulates normal cell functions, like growth and differentiation.

Interferon• Naturally occurring proteins produced by virus-infected cells that

helps other cells resist viral infection.• There are 3 types of interferon, alpha, beta and gamma• Standard interferon is broken down relatively fast by the body• Has to be injected 3 times a week• Effectiveness decreases, allowing HCV to multiply in between

injections

Types of Acquired Immunity

• The adaptive immune system is a functional system that:– Recognizes specific foreign substances– Acts to immobilize, neutralize, or destroy foreign

substances– Amplifies inflammatory response and activates

complement

Adaptive (Specific) Defenses

• 10- 20 normally inactive proteins • When activated, they “complement” or enhance

certain immune, allergic and inflammatory reactions.– Activation of inflammation– Opsonization – enhances phagocytosis– Cytolysis – membrane attack complex

The Complement System

• The adaptive immune system is antigen-specific, systemic, and has memory

• It has two separate but overlapping arms– Humoral, or antibody-mediated immunity

• B cells (mature in bone) make antibodies: specific proteins that bind to specific antigens

– Cellular, or cell-mediated immunity • T-cytoxic lymphocytes attack virus infected or tumor

cells directly

Adaptive Immune Defenses

Differentiate between cellular and humoral immunity

Adaptive Immune Defenses

• B cells encounter antigens and produce antibodies against them– Naturally acquired – response to a bacterial or viral infection– Artificially acquired – response to a vaccine of dead or attenuated pathogens– Regarding acquired immunity, the introduction into a recipient of dead or attenuated

pathogens, via a vaccine, is an example of Active, artificially acquired immunity

A vaccination artificially acquired active immunity

Active Humoral Immunity

• Differs from active immunity in the antibody source and the degree of protection– B cells are not challenged by antigens– Immunological memory does not occur– Protection ends when antigens naturally degrade in the

body• Naturally acquired – from the mother to her fetus

via the placenta• Artificially acquired – from the injection of serum,

such as gamma globulin

Passive Humoral Immunity

Gamma Globulin: A Gamma Globulin shot is purely an injection of antibodies to provide temporary immunity. You might receive an Gamma Globulin shot if you travel outside of the country.

Artificially acquired passive immunity could be the result of gamma globulin injection.

Gamma Globulin

AntibodiesAn antibody is a protein produced in response to an antigen.“Y” shaped proteins – gamma globulins

have a variable region that matches a specific antigen (Fab region)

Have a constant region – activates complement (Fc region)

There are 5 classes of antibodies:– IgG—most abundant; about 80% of all antibodies in

the blood; can cross the placenta from mother to fetus, giving newborns immune protection

– IgA—makes up 10-15% of antibodies in the blood; levels decreased during stress

– IgM—makes up 5-10% of antibodies in the blood; first secreted by plasma cells

– IgD—makes up only about 0.2% of antibodies in the blood

– IgE—makes up less than 0.1% of all antibodies in the blood; involved in allergic reactions

Antibodies - Immunoglobulin

• Substances that can mobilize the immune system and provoke an immune response

• The ultimate targets of all immune responses are mostly large, complex molecules not normally found in the body (nonself)

Antigens