ANAT TEST 3

Exam 3 material (body's protective system) 

The lymphatic and immune system are a group of specialized cells, biochemicals, tissues organs and organs and vessels that work to protect the body 


Immunity: 

Specific: 

cell mediated→ CD4, T cells           cell mediated—> CD8,  T cells

Antibody→ mediated 


Non specific: 

Physical (temp, barriers, mechanical effects) 

Chemical substances

Cellular (Neutrophils, macrophages, eosinophils,basophils) 


Lymphatic system 

  • The lymphatic system consists of vessels, tissues and organs which create immune cells

  • It has 3 functions 

  1. Fluid recovery- removes excess fluid, vessels

  2. Immunity- cells that activate protection 

  3. Lipid absorption- dietary lipids, lacteal


Lymphatic pathway 

  • A system of vessels separate from the circulatory system 

  • Transport lymph fluid

  • Vessels are “blunt ended”

  • Drain excess fluid from between cells- interstitial fluid from between cells interstitial fluid 

  • L pathways begin as capillaries 

  • Located next to blood capillaries 

  • Microscopic 

  • Thin- walled 

  • A place for fluid exchange 

  • L vessels are similar to veins but thinner 

  • Three layers 

  1. Inner- endothelial lining 

  2. Middle- smooth muscle 

  3. Outer- CT 

  • Semilunar valves for one direction flow of fluid 

  • L trunks drain lymph fluid from L vessels according to region 

  • Named for regions of the body 

  • Lumbar

  • Intestinal 

  • Bronchiomediastinal 

  • Intercostals 

  • Subclavian 

  • L trunks join to become collecting ducts 

  • Thoracic duct (¾ collects fluid and brings way up) 

  • Right lymphatic duct (¼ of the fluid from the body) 

  • The ducts empty into the subclavian vein

  • So lymph returns to the blood 


How is lymph fluid formed 

  • It begins as a plasma in a blood capillary 

  • Pressure created by the beating of the heart

  • Squeezes water and small molecules out of the blood capillary into the tissue spaces 


There, the liquid is called interstitial fluid (ISF)

  • Much of the ISF goes back into the blood capillaries 

  • The remainder is called lymph and enters lymphatic capillaries 

  • These capillaries permit excess tissue fluid and dissolved molecules (proteins) to leave the tissue spaces 

Lymphatic drainage prevents the accumulation of too much tissue fluid 


  • Eventually lymph returns to the plasma again


Lymph flow in the vessels 


  • Under low pressure 

  • The vessels contract as lymph moves through them 

  • Dependant on contractions of skeletal muscles and arteries pulsing 

  • Valves prevent backflow 

  • Very much like vein blood flow 


Lymphatic cells 

  • Protective cells lymphocytes and other cells that work in protection and immunity 

  1. Neutrophils 

  2. Natural Killer cells 

  3. T- lymphocytes 

  4. B- lymphocytes 

  5. Macrophages 

  6. Dendritic cells 

  7. Reticular cells 


Neutrophil 

  • Aggressive antibacterial WBC 

  • High percent in the blood 


Killer cells 

  • Natural killer (NK) and lymphokine activated killer (LAK) cells 

  • Large cells that attack and destroy 

  • Cancer, virus, and transplanted tissue cells 


T- lymphocytes 

  • T- cells 

  • Mature in the thymus 


  • B- Cells 

  • Make antibodies 


Macrophage 

  • Many start as monocytes in the blood and then move to connective tissue 

  • Use phagocytosis to engulf invaders, dead cells, debris, and bacteria 


Dendritic 

  • branched , mobile cells 

  • Role in alerting immune system 

  • work by receptor mediated endocytosis 

Reticular cell 

  • Stationary APC 

  • Located in the stroma of lymph organs 

  • Not fibers 

Lymphatic tissue 

  • Clusters of lymphocytes in connective tissues and organs

  • Work to protect the body 

  • Two types: 

  1. Diffuse lymphatic tissue 

  2. Lymphatic nodules

Lymphatic tissue 

  1. Diffuse lymphatic tissue

  • Simplest scattered protective cells mainly at openings to the body, where there are mucous membranes 

  • Mucosa- associated lymphatic tissue (MALT) 

  • Resp, urinary, digest, repro- tracts

  1. Lymphatic nodules

  • Lymphocytes and macrophages group together in a mass- nodule 

  • Can come and go with infections- invaders

  • Lymph nodes, tonsils, lower portion of small intestine; always can find them 


Lymphatic Organs 

Organs have a well-defined shape with anatomical locations and structures, separating the from other tissues 


Lacteal

  • Lymph vessels form lacteals

  • Found in the villi of the small intestine 

  • Play a major role in the absorption of dietary fats

  • lacteal - a structure of the villi in the small intestine 


Red bone Marrow

  • Made from different tissues working together- organ 

  • Soft 

  • hematopoiesis - blood formation 

  • Lymphocyte production 

  • Body immunity 

Thymus 

  • Located anterior to the aortic arch 

  • Larger in infancy and early childhood 

  • Shrinks after puberty 

  • Is replaced by adipose tissue in older persons 

  • CT covering divided into lobules 

  • Lobules house maturing 


Thymus cell maturation 


  • Immature T cells migrate from the Red bone marrow to the thymus 

  • Develop under the influence of the hormone thymosin 

  • Mature T cells leave the thymus and work to protect the body 


Lymph nodes 

  • As lymph moves toward the lymphatic ducts, it passes through lymph nodes

  • Range in size from pinheads to lima beans

  • Most numerous lymph organ 

  • clean/filter lymph fluid before it re-enters the plasma 

  • Site for B and T cell activation 

  • In all areas except nervous tissue 

  • Structure: capsule, made from CT, surrounds the node

  • Hilum 

  • Where blood vessels and nerve enter the node 

  • Four entrances for lymph 

  • One exit for lymph 

  • Found in groups or chains 

  • Located along the larger lymph vessels 


Tonsils 

  • Lymphoid tissue located in a ring around the mouth and throat 

  • Three basic groups 

  1. Palatine tonsils: side of throat 

  2. Pharyngeal tonsils (adenoids): near the opening of the nasal cavity 

  3. Lingual tonsils: base of the tongue


Tonsils: covered by an epithelial tissue, has pits called crips  


Spleen

  • Largest lymph organ 

  • Thin and long (wraps around edge of stomach) 

  • Located in the upper left abdominal cavity 

  • Contains a hilum where it connects to the splenic artery and splenic vein also lymph vessels 

  • Structure: enclosed in CT capsule 

  • Separated in lobules by CT 

  • Two tissue types in lobes:

  • White pulp

  • Located along the outside of the splenic artery 

  • Packed with lymphocytes and macrophages 

  • Red pulp 

  • A network of channels filled with RBC 

  • Major functions: 

  1. Destruction of old red blood cells (RBC)

  2. Blood cell production before birth and in times of anemia 

  3. Major cite for mounting the immune response, has a reservoir of monocytes 

  4. Filters the blood not lymph

  5. If ruptured can be fatal

  6. You can live without a spleen 

What is a pathogen?


Pathogens are: 

  1. Disease or allergy causing agents 

  2. Bacteria, viruses, microorganisms, spores

  • The presence of pathogens can cause infection or illness of the body 

  1. The immune system must distinguish what is “self” and “non-self” 


The defense system 

  • The body has two main defense areas: 

  • 1. Non- specific/ innate immunity 

  • General body defenses- born with these 

  • Broad protection 

  • 1st and 2nd lines of defense 

  • 2. Specific responses/ adaptive immunity 

  • Adapts and has memory 

  • Responses to specific pathogen (organism)

  • 3rd line of defense 

  • Although each side of the system has unique functions- 

  • There is interplay between the systems 

  • Areas of the general system influence the specific system

 

Think of the body having “lines of defense” 

  1. First line

  • Keep stuff out! Skin, mucous membranes 

  1. Second line 

  • If skin broken; use cells, proteins, fever inflammation 

  1. Third line 

  • Adaptive immunity- vaccination 


The nonspecific/ innate system 

  • Nonspecific immunity confers a general protection to the body. 

  • Uses defenses that are present and ready. 

Physical Barrier 

  1. The skin and mucous membranes are a physical barrier.

  2. Skin sloughing removes invaders from the skin surface. 

  3. Cilia movement. 

  4. Mucus traps invaders- GI, respiratory, body openings 

  5. Tears, sweat, saliva, urine flush organisms away

  6. Normal flora crowd out pathogens 


The nonspecific immune system 

  • Chemical substances

  • Chemical substances and enzymes in body fluids make a chemical barrier. 

  • A. Fatty Acids inhibit bacterial growth 

  • B. Enzymes in tears, saliva, and nasal secretions degrade bacteria

  • C. Low pH prevents bacterial growth (sweat, gastric juice) 

  • The skin is covered by antimicrobial chemicals 

  • Acid mantle- made by sweat and sebum

  • Lactic and fatty acids 

  • Inhibit bacteria 

  • There are antimicrobial peptides

  • A small part of a protein 

  • Can inhibit bacteria, fungi, parasites, and viruses 

  • Protection 

Two examples: 

cathelicidins - proteins that protect against bacteria, yeast, viruses. Recognize pathogen-grab- environment 


Defensins: 

Secreted by WBC
Low molecular weight proteins that have anti- microbial activity- lung, GI

Attack bacterial cell walls, pathogen


Cathelicidins 

  • Function in the innate immune system 

  • These molecules recognize apoptotic cells and perhaps necrotic cells and cell debris 

  • Collagenous tails signal for engulfment 

  • Can act as a link between innate and adaptive immunity.

Definsins 

  • Most defensives are antimicrobial proteins 

  • Amphipathic molecules 

  • Have a hydrophilic side (pink) and hydrophobic side (green) 

  • This allows them to interact with microbial membranes and create holes 


Nonspecific Immune system 

  • Anatomical barriers are very effective in preventing invasion by microorganisms

  • However, when there is damage to tissues and the anatomical barriers are breached infection may occur

  • Once infectious agents are present, innate defense mechanisms- called humoural factors come into play 

  • These factors are found in blood serum or formed at the site of infection 

Nonspecific/ Innate system 

  • WBC and macrophages 

  • The same WBC you have seen before, found in the plasma of the blood 

  • 1. Neutrophils- bacteria killer

  • 2. Eosinophils- parasites, allergens 

  • 3.  Basophil- heparin 

  • 4. Lymphocytes- B and T cells

  • 5. Monocytes- in blood, phagocytes 

  • Cellular responses 

  • Complement 

  • A group of over 30 globulins (proteins) made mostly in the liver 

  • Circulate in plasma in an inactive form 

  • And are activated by a pathogen 

  • Work to defend the body 

Complement Activation 

Complement can be divided into four pathways:

  • Classical pathways 

  • Lectin pathway 

  • Alternative pathway 

  • Membrane attack (or lytic) pathway 

  • Complement can opsonize bacteria for enhanced phagocytosis 

  • Recruit and activate cells- WBCs 

  • Participate in regulation of antibody responses

  • Stimulate inflammation 

  • But, can also have detrimental effects for the host; contributes to inflammation → anaphylaxis 

  • Classical pathway 

  • There is an antigen on the pathogen 

  • It binds to the antibody from the body 

  • Complement binding site 

  • Starts a cascade

  • Ends in the bursting of the pathogen 

  • Adaptive immunity- because of the antibody 

  • Alternative pathway 

  • No antibody 

  • Slower 

  • Still a cascade 

  • targets - cancer, viruses, bacteria, yeasts

  • Drills a hole through the path membrane 

  • No antibody- innate system  

The inflammatory response: 

  1. Body invaded: Bacteria or tissue damage 

  2. Response: Heat, Pain, redness swelling 

  3. Increased blood flow to bring chemicals/cells to area of damage/ invasion 

  4. WBC to the rescue 

  5. Possible production of pus 

Specific Immune system

  • 1. Specific immunity includes protective mechanisms that confer very specific protection 

  • Works against certain types of invading agents; bacteria, toxic material, viruses 

  • Reacts only in response to that organism, one to one 

  • 2. Is a second line of defense

  • Protects against re- exposure to the same pathogen

  • Involves memory cells

  • The body can recognize and respond to certain substances or bacteria 

How it works! 

  • 3. Specific immunity response pattern: 

  • When first attacked, the body fights the invading organism and symptoms occur (flu, cold, fever) response takes 7-10 days 

  • The second attack (by the same organism) produces no symptoms 

  • The organism is destroyed quickly- response time is 1-3 days 

  • The person is now immune 

The body remembers and it instantly makes responder 


How do we get specific immunity? 

  1. Natural immunity 

Exposure to the agent is not deliberate, happens in the course of living 

  1. Active exposure Immunity due to the body's response to a disease or infection 

  2. Passive exposure Temporary protection through the mother before birth or breast milk 

2. Artificial Immunity 

Exposure to the agent is deliberate 

  1. Active exposure An immunization against a disease- causing agent 

  2. Passive exposure Immunity developed by injection of antibodies developed in another individuals immune system 

Immunity 

What is an antigen?

- a molecule that can trigger an immune response 

- proteins, allergens, glycolipids 


  • Antigens can come from outside of the body 

  • Non-self

  • Act as an invader

  • Or, can be self- antigens 

  • Blood 

  • In general the body responds to non- self antigens 

  • In order to protect the body 


What is an antibody?

  • Antibodies are proteins, normally in the body with unique concave regions called combining sites 

  • The antibody can combine with a specific antigen by fitting in the combining sites 

  • “Lock and key” fit 

  • This forms an antigen- antibody complex 

  • This mechanism is called humoral or antibody mediated immunity 

  • Antibodies change the antigen so they cannot harm the body 

  • Antibodies act in several ways 


1. If the antigen is a toxin- poison 

  • The toxin is naturalized or made nonpoisonous 

  • Neutralization being made active!!


2. If antigens are in the surface membranes of invading or diseased cells (microbes or cancer cells) 

  • Antibodies will attach to several antigens, clumping the cells together (agglutination) 

  • Then phagocytes can destroy large numbers of them at one time 


3. When antigens combine with certain antibodies 

  • The antibody changes shape to expose two complement binding sites and will activate the complement proteins 

  • Complement fixation 


Types of immunoglobulin 

  • An immunoglobulin is a globular plasma protein that functions as an antibody 

  • There are five types of Ig

  1. IgG 80% of antibodies

  2. IgA  13% of antibodies

  3. IgM 6% of antibodies 

  4. IgD

  5. IgE 


Lymphocytes 

  1. The most numerous cells of the immune system are lymphocytes 

  2. Lymphocytes continually patrol the body on “search and destroy” missions 

  3. Dense populations of lymphocytes are found in the lymph nodes and other lymphatic tissues 

  4. The two major types of lymphocytes: 

  1. B- lymphocytes (B cells)  bone

  2. T- lymphocytes (T cells) thymus


  • Stem cells in red bone marrow give rise to lymphocyte precursor  


  • Some move to the thymus and become T- cells


  • Some are processed in the bone marrow to become B cells 


  • Both cells can be transported by the blood to lymph organs and tissues 


T cell activation

Stage 1: T cells are released from the thymus 

  • T cells have an antigen receptor on the plasma membranes 

  • Stage 2: If it contacts its specific antigen, it is activated 

  • Activated T cells produce cell mediated immunity 


  • T cells secrete peptides called cytokines that can attack viruses, infected cells and cancer cells 

  • Helper T 

  • Cytotoxic T 

  • Memory T 


B  Cell activation 

  • B cells- two stage development in the bone marrow 

  • 1. Stem cells into immature B cells: 

  • Immature B cells have an antibody or antigen receptor inserted in to the plasma membrane 


  • transport in blood to lymph organ (nodes mainly) 

  • They then act as seed cells to produce identical cells called clones 


  • 2. When the antigen receptors receive an antigen, the immature B cells become activated 

  • Rapidly reproduce two types of cells: 

Plasma cells 

Memory cells


  • Plasma cells secrete 2000 antibodies per second into the blood. 

  • Live for 4-5 days 

  • “Antibody factories”  


  • Memory cells remain in reserve until contracted by the same antigen that led to their initial formation 

  • Then, develop into plasma cells 

  • Secrete the same antibody “made them”