unit 4 lymphatic system nrs 237
TRANSCRIPT
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