Immune System Function and Mechanisms

• There are 3 functions of the lymphatic system:

Fluid Balance

• About 30 liters of fluid leave the blood and enter the interstitial spaces, while only 27 liters return.
• The remaining 3 liters become interstitial fluid and the absence of this reuptake causes edema, tissue damage, and death.

Lipid Absorption (Lacteals)

• Lymphatic vessels in the digestive tract lining absorb lipids and other substances, then lipids enter the venous circulation.

Defense

• Microorganisms are filtered from lymph to lymph nodes and from the blood to the spleen
• The lymphatic system filters bad substances out of the blood and lymph, preventing infectious diseases

Parts of the Lymph

• Lymph is the fluid passing through lymphatic vessels back to the blood and includes water, ions, nutrients, gases, and proteins derived from plasma
• Lymph also carries hormones, enzymes, and waste products
• Chyle is fluid passing through lacteals and vessels, appearing white due to its lipid content

Lymphatic Vessels

• Lymphatic vessels are essential for fluid balance
• Lymphatic capillaries originate as small dead-end tubes
• Fluid moves from blood capillaries into tissue spaces, and extra fluid entering these tissues forms lymph within the capillaries
• Lymphatic capillaries exist in most tissues of the body
• Lymphatic vessels are absent in the central nervous system, bone marrow, and cornea

Superficial and Deep Lymphatic Vessels

• Superficial vessels are in the dermis of the skin and subcutaneous tissue
• Deep vessels are in muscles, joints, viscera, and other deep structures

Lymphatic Capillaries

• Lymphatic capillaries lack a basement membrane and consist of simple squamous endothelial cells that are overlapped and loosely attached
• The structure of the capillaries makes them more permeable than blood capillaries, allowing everything in the lymph to enter the capillaries
• The overlapping cells function as one-way valves, only allowing lymph entry but not exit

Lymphatic Vessels Structure

• Lymphatic vessels resemble small veins, formed by joined capillaries
• The inner layer consists of endothelium surrounded by an elastic membrane
• The middle layer consists of smooth muscle cells and elastic fibers
• The outer layer is a thin layer of connective tissue

Lymph Movement

• Lymph moves through lymphatic vessels via contraction of lymphatic vessels, contraction of skeletal muscles, and thoracic pressure changes

Lymph Nodes

• Lymph nodes are round, oval, or bean-shaped bodies distributed along lymphatic vessels and filter the lymph.
• Fluid moves from one to another by filtering lymph as it enters and exits the nodes through the lymphatic vessels
• Lymphatic trunks form when vessels converge to form larger vessels
• They drain lymph from major body regions

Lymphatic Trunks

• Jugular trunks drain lymph from the head to the neck
• Subclavian trunks drain lymph from the upper limbs, superficial thoracic wall, and mammary glands
• Bronchomediastinal trunks drain lymph from the thoracic organs and deep thoracic wall
• Intestinal trunks drain lymph from abdominal organs like the intestines, stomach, pancreas, spleen, and liver
• Lumbar trunks drain lymph from lower limbs, pelvic and abdominal walls, pelvic organs, ovaries or testes, kidneys, and adrenal glands

Lymphatic Ducts

• Lymphatic trunks either connect to large veins in the thorax or to larger vessels called lymphatic ducts
• The right lymphatic duct joins a right thoracic vein and jugular, subclavian, and bronchomediastinal trunks, draining the right side of the body

Thoracic Duct

• The thoracic duct is the largest lymphatic vessel, measuring 38-45 cm in length, extending from the twelfth thoracic vertebra to the base of the neck
• Drains lymph from the right side of the body inferior to the thorax and the entire left side of the body
• Jugular and subclavian trunks join into the thoracic duct
• The bronchomediastinal trunk sometimes connects, but typically joins a vein

Lymphatic System Overview

• Excess interstitial fluid enters the capillaries to form lymph
• Capillaries converge to form vessels
• Lymph passes through vessels and is filtered by lymph nodes
• Vessels converge to make trunks which drain lymph from major body regions
• Trunks empty into the thoracic vein or combine to form larger ducts that empty into thoracic veins

Lymphatic Tissue

• Lymphatic tissue consists primarily of lymphocytes but also includes macrophages, dendritic cells, reticular cells, and other types

Primary Lymphatic Organs

• Primary lymphatic organs include red bone marrow and the thymus
• In these organs, lymphocytes become immunocompetent, enabling them to launch an immune response
• Red blood cells, lymphocytes, B cells, and T cells originate from stem cells and become immunocompetent
• Pre-T cells move from red bone marrow through the blood to the thymus
• Secondary lymphatic tissue and organs include lymphatic nodules like tonsils, diffuse lymphatic tissue, lymph nodes, and the spleen
• These locations allow lymphocytes to interact with each other, other immune cells, and foreign substances to produce an immune response
• Lymphatic organs have a capsule, whereas lymphatic tissues are more diffuse and lack a capsule

MALT

• Mucosa-associated lymphatic tissue (MALT) is a type of nonencapsulated lymphatic tissue
• Mucous membranes line the digestive, respiratory, urinary, and reproductive tract that include the tonsils
• MALT keeps microorganisms from entering the body

Lymphatic Tissue and Nodules

• Diffuse lymphatic tissue disperses lymphocytes, macrophages, and other cells without a clear boundary, blending with other tissues
• This tissue is deep within mucous membranes, around lymphatic nodules, and within lymph nodes and the spleen
• Lymphatic nodules are denser arrangements of lymphatic tissue found in the loose connective tissue of the digestive, respiratory, urinary, and reproductive systems
• Nodules are found within lymph nodes and the spleen, known as lymphatic follicles

Peyer Patches and Tonsils

• Peyer Patches are large collections of lymphatic nodules in the distal half of the small intestine and tonsils
• Tonsils are a large group of nodules with diffuse lymphatic tissue that keeps harmful substances from enetering the body through the nasal and/or oral cavity
• Tonsils can disappear in adults
• Palatine tonsils are on each side of the junction between the oral cavity and pharynx
• The pharyngeal tonsil is between the junction of the nasal cavity and the pharynx and when enlarged is called the adenoids

Tonsils and Lymph Nodes

• The lingual tonsil is on the posterior surface of the tongue
• Lymph nodes are distributed along the course of lymphatic vessels and filter lymph, removing bacteria and other materials

Lymph Node Distribution

• There are 450 nodes in the body
• The head and neck contain 70
• The axillary contains 30
• The thoracic area has 100
• The abdomen and pelvic has 230
• The inguinal and popliteal has 20 lymph nodes
• The dense connective tissue surrounds these nodes called capsule

Internal Node Structure

• Trabeculae are extensions of the capsule that form a delicate internal skeleton of the node
• The cortex contains the subcapsular sinus beneath the capsule and cortical sinuses

Inner Medulla and Vessels

• The inner medulla features branching irregular strands of diffuse lymphatic tissue called medullary cords separated by medullary sinuses
• Afferent lymphatic vessels carry lymph to lymph nodes, while efferent lymphatic vessels carry lymph away from lymph nodes
• Efferent vessels enter the subscapular sinus, filter through the cortex and medulla, and exit the node through vessels

Germinal Centers

• The germinal centers are the area of rapid lymphocyte division

Spleen structure

The abdominal cavity contains the spleen, it is clenched fist size on the left, in the superior part

• An older person tends to have a smaller spleens Connective tissue and smooth muscle, with white pulp that is a lymphatic tissue surrounding the arteries within the spleen.
• There is the red pulp that is associated with the veins in the spleen, fibrous network and contains the macrophages and red blood ells
• White pulp in within the spleen is 1/2 of the volume

Spleen and Periarterial Sheath

• Branches of the splenic artery enter the spleen at the hilum
• The periarterial lymphatic sheath is diffuse lymphatic tissue surrounding arteries and arterioles that extends to lymphatic nodules

Spleen Functions

• The spleen functions by destroying defective red blood cells, detecting foreign substances in the blood, and acting as blood reservoir
• Old blood cells can rupture as they pass through the splenic cords

Immune Cells in Spleen

• T cells are within the periarterial lymphatic sheath
• B-cells are in the lymphatic nodules
• The Spleen shrinks 40-50% during exercise

Thymus

• The Thymus is a bilobed gland, located in the superior mediastinum
• Trabeculae extend from the capsule, dividing it into lobules to the substance of the gland
• Maturation of the T cells are done through the thymosin, a homrone that helps with he maturation

Development

• There are rounded epitheilial structures for the development of the regulatory T cells
• Regulatory T cells suppress the body's immune response and protect against autoimmune diseases

Immunity

• Innate immunity recognizes and destroys foreign substances with the same response each time, present at birth and genetically determined
• Adaptive immunity recognizes and destroys foreign substances with a faster and stronger response than the first time the substance was encountered and it has specificity and memory

Specificity

• Specificity is the ability to adapt immunity to recognize a particular substance

Physical and Chemicals

• The physical barrier with skin and the mucous membranes, prevent organisms that can prevent the organism and chemicals from entering the body
• remove organisms from the body by means of tears, saliva, and even in mucous membranes by coughing and sneezing

Chemical Mediators

• Molecules are responsible for innate immmunity
• some produce chemical mediators on the surface of the cells to kill a microorganism to keep them from entering
• complements and eicosanoids promote in causing inflammation from vasodilation

Cytokines

• Proteins or peptides secreted by calls that bind on the receptors
• Bind to neighboring cells
• Regulate the intensity and duration of immune responses
• Interfeons interlukines and the lymphokinines with the function with the immune system
• Chemicals within the surface prevents the microbial growth

Functions

• Surface prevent microbial growth and kills the microorganism, and the the mucus on the surface on membranes traps the microbial growth unitl destroyed
• Histamine produced by the Amine released from the mast cells , basophils platelets
• increases the vasodilation
• increases the vascular permeability
• it stimulates gland secretions
• allows the contraction of smooth muscle of airway passage

Kinins and Interons

• Polypeptides are derived by teh plasma proteins produced by vasodilation and vascular permeability
• interferes with pain receptors
• and attracts the neutrophils
• Interferes with the virus production produced by many cells

Complement

• plasma proteins increase the vascular permeability
• Histamine for activation
• Activated kinins to promote
• Activates neutriphols and the macrophages
• There are groups of lipids that cause vascular permeability and vasodilation to stimulate receptor pain

Leukotrienes and Pyrogens

• A group of Lipids with the basophilis, it produces prologned muscle contraction and vascular permeability, it attracts neuriphils as well
• Released by neutrophils and other cells and stimulate fever production

Group of Proteins

• There re a group of proteins that protect the body by destroying the abnormal cells
• and increase other components of the immune systems
• circulating the blood
• The series are a reaction that makes hte compliment
• produces a channel and destroyis cells within the plasma mambrane
• Activated c3s the break down the cell Opsonization

Opsonization and Interferons

• Complement proteins that attach bacteria as and stimulate that cell to break down

Interferons

• Body is protected against the viral infection and from the cancer
• White blood cells produced by the bone marrow and the lymphatic tissue
• Attracted by the chemotatic signals, and chemicals release body cells

Chemotaxis

• parts of the microbes that by the cells within the chemicals as well
• diffuse from area, moving towards the substance

Phagocytosis

• Destroys cells with small inflammation and increases inflammation
• neutrophil is a cell that leaves blood stream and goes towards a infection area

Lysosomal Enzymes

• Releases Lysosomal enzymes that kill the microorganism and inflmmation
• An accumlation of dead neutrophils

Monocytes and Macrophages

• leaves the blood and enter the tissues to become a macrophage
• Most effective phagocyte
• intercepts subsnatces
• activates B and t cells
• Nonmotile cells will promote inflammation

Eosinophil

• Dfens against parasitic infections and it is a asthma and allergies

Tumors

• Lyes tumor and virus cell
• Type of lymphocyte produced in red bone marrow Is 15%
• Subsatnces that stimulate immune responce

Cytotoxic T

• Cytoxic t cells produce the immune cell, it kills infection and also promotes

Immunities and Cells

• Helper T cells are able to both promote and inhibit the activities that come with both anti bodies
• Cell adaptions for adaptive immune function B cells are also either memory B cells, or Plasma cells
• Cytotoxin are responsibvle for destroying by lyrsis
• activate cells and T cells

More Immunities

• Are quick to have a response and adaptive innmune funtions
• Dendritic cell are process ang and it ivloved cell that is acitvates B and T cells and it helps activate it by the recepotors

T Cell and B Cells

• Two chains consitent of variable region for T cell and for B cells has identacla variables on surface where the antigen bond
• There are major histocompatibility complex molecules

MHC and Antigens

Glycoprotein fond in the membranes of most of the body cells

• Exogenous
• produced in antigen
• in displays found in nuclearted cells Displays exogenous agents that are phagyic

Antigens and Cells

• Antigen process the externaly It binds with macrophages and dendric
• dendritic large cells that use for extension and process antigen and call for T cells

Selection

• cells are specialized to clones and go to the surface of the clones
• it elimnates cells acting against the person It has 2 cells and the it generates the antigen in 2 types of repsonse

Interferons Pt. 2

• Precent it and it is secreted by cells Helps prevent viral replication

• It decreasses

• Activates killer cells and prevents it

• Secretes helper cells In conjuction with the the B and T cells it activates the the B and T cells

Interleuklin

• Promotes by activting the glands fever produced by it
• B cell that is sercreted For the Alageric and helper B cells Interfeons Also fights with SSOS cells And fights Helbert T cells

Explore the intricacies of the immune system, focusing on adaptive and innate immunity. Understand the role of physical barriers, chemical mediators, and cytokines in defense mechanisms. Learn about lymph node and spleen functions, including their structural support via trabeculae.