The Lymphatic System: Components and Functions

Lymphatic System Components

• Lymph is fluid containing fats and proteins that circulates, derived from plasma that escapes capillaries and is collected in interstitial spaces.
• Lymphatic vessels collect interstitial fluid and return it to blood circulation, maintaining blood volume and blood pressure
• Proteins in lymphatic vessels create colloid osmotic pressure which regulates fluid movement in/out of blood capillaries
• Lymphatic vessels do not contain a pump; fluid moves from areas of high to low pressure, with lymphatic vessels having lower pressure than blood vessels
• Fluid accumulation and influx pushes lymph along, eventually connecting to blood vessels near the heart
• Lymph flows unidirectionally toward the heart, transporting proteins

Lymphoid Tissues, Organs, and Capillaries

• Lymphoid tissues and organs contain phagocytic cells and lymphocytes for immune functions
• Lymphoid tissues/organs filter lymph to remove foreign substances and filter blood
• Lymphatic capillaries are the smallest vessels, acting as dead-end vessels comprised of loosely overlapping endothelial cells with only one tunica interna
• Lymphatic capillaries lack tight junctions, and when external fluid pressure is greater, openings are created for fluid entry
• Minivalve systems act like valves, responding to pressure differences; high internal pressure seals cells tightly, serving as an entry for fluid into lymphatic circulation
• Endothelial cells are anchored by collagen fibers, loosely holding cells and creating a permeable system that aids in minivalve formation
• When interstitial fluid pressure exceeds lymphatic vessel fluid pressure, fluid moves into the capillaries

Lacteals and Lymphatic Collecting Vessels

• Lacteals are lymphatic capillaries in the intestines, located in small intestine villi, absorbing digested nutrients like fats and proteins for bloodstream delivery
• Proteins are not directly absorbed through the digestive system but are broken down into amino acids first
• Chyle denotes lymph within lacteals
• Lymphatic collecting vessels receive fluid from capillaries, possessing three tunics and valves
• Lymphatic collecting vessel walls are thinner than veins due to lower pressure but contain a greater number of valves which prevent backflow of lymph

Lymphatic Trunks and Ducts

• Lymphatic trunks empty into lymphatic ducts, with five major trunks including the bronchomediastinal (drains thoracic cavity), subclavian (drains arms/shoulders), jugular (drains head/neck), lumbar (drains legs), and intestinal (drains bottom of torso)
• Trunks drain specific body areas, named according to their drainage area, before emptying into lymphatic ducts
• Ducts connect to the junction of jugular and subclavian veins, where vein pressure is lower than fluid pressure in lymphatic ducts
• Fluid is collected and moved along due to pressure, directed into either the right lymphatic duct (drains head, upper arms, thorax) or the thoracic duct (drains rest of body, originating from cisterna chyli)

Lymph Movement

• Lymph flows through the lymphatic system in the following sequence: Lymphatic Capillary, Lymphatic Collecting Vessel, Lymphatic Trunk, Lymphatic Duct
• Cisterna Chyli is a major collection point receiving lymph from the lumbar region
• Valves prevent backflow, ensuring lymph moves in one direction
• The muscular pump uses muscle contraction/relaxation to squeeze vessels and cause a pressure change
• The respiratory pump utilizes pressure changes in the thoracic cavity during breathing to aid movement
• Arterial pumping uses lymphatic vessels running alongside arteries that get "pushed" as blood flows through the artery to assist movement by changing pressures to squeeze the lymphatic vessels
• Smooth muscle contraction in lymphatic trunks/thoracic ducts helps propel lymph
• Lymphedema is lymphatic swelling that can lead to reduced blood volume and immunity

Lymphoid Cells and its Types

• Lymphoid cells include lymphocytes, the two main types of lymphoid cells:
  • B lymphocytes recognize and attack foreign substances.
  • Once activated they produce plasma and some become memory cells. Antibodies mark targets for destruction
  • T lymphocytes directly attack body cells
  • Become immunocompetent in the thymus
  • Activated by infected body cells
  • Kills and destroys cell and when T cells bind to something, they lyse the cell to kill it
  • Exists in spaces between fibers and they can move and travel with lymph to get into the bloodstream
• Macrophages start as monocytes, circulate with diapedesis out of circulation, once out of circulation become phagocytic cells
  • Activates T cells
  • Antibodies activate macrophages
  • Attached directly to fiber
• Dendritic cells are phagocytic cells that activate T lymphocytes, destroying foreign cells, activating T-lymphocytes to destroy engulfed antigens, and essentially killing themselves
• Reticular cells produce stroma, a network of reticular fibers supporting other cells, with T, B, and phagocytic cells existing within this mesh
  • Found in all lymphoid organs except thymus

Lymphoid and Lymphatic Tissues and Organs

• Lymphoid tissues are sites for lymphocyte proliferation, with lymphoid cells accumulating and macrophages attaching to stromal fibers
• Allows for the detection of infection or damage and lymphoid tissue consists predominantly of reticular connective tissue, except in the thymus
• Lymph nodes are clusters along lymphatic vessels through which Lymph passes through and is processed by housing lymphocytes
• Antigens are markers on the surface of a foreign cell or harmful pathogen, and activated immunity when something foreign is detected
• Lymph node action:
  • Lymph enters via multiple afferent lymphatic vessels
  • Then it filters through sinuses and nodules in the medulla
  • Exits at the hilus via efferent vessels with less efferent vessels to increase efficiency of filtration and pressure
• Spleen: The largest lymphatic organ, located behind the stomach the size of your fist
  • Splenic artery delivers blood, splenic vein drains blood from the spleen; blood undergoes processing as lymphocytes proliferate and processes red blood cells in embryo
  • Removes aged and infected elements
  • Blood enters the spleen via the splenic artery, filtering through white/red pulp where lymphocytes/macrophages act
  • Cleaned lymph returns via splenic vein
• Thymus: Produces hormones to create white blood cells
  • Helps create lymphocytes, deteriorates with age, and very active in youth
  • The thymus secretes thymosin and thymopoietin stimulating the production of white blood cells and causing lymphocytes to become immunocompetent
  • No reticular fibers or stroma is in the thymus and Instead, it has thymocytes and epithelial/secretory cells to release hormones

Tonsils and Patches

• Tonsils are located at the entrance for food and air and traps anything foreign
  • Sets of tonsils include paired palatine tonsils (often infected, roof of mouth), paired lingual tonsils (at base of tongue), single pharyngeal tonsil (adenoids), and paired tubal tonsils, surrounds tempano pharyngeal tube (connects middle ear)
  • Tonsil histology contain germinal centers and crypts trap bacteria and particulates. Then the lymphoid tissue destroys pathogens to avoid infection
• Peyer's Patches are lymphatic organs in the distal small intestine and appendix
  • Destroys bacteria, generate memory lymphocytes, and creates memory cells for long-term immunity

Lymphatic System Development and Immune System

• Lymphatic vessels start as buds from developing veins, eventually forming a branching system, connecting with jugular veins to form the right lymphatic/thoracic ducts
• Lymphoid organs develop from mesodermal mesenchyme that becomes a reticular tissue, migrates, and starts to populate after birth except the thymus, in the endoderm
• The immune system prevents pathogens from entering or spreading and is technically a functional system using various organ systems
• Immune Systems:
  • Nonspecific: Innate immune system attacks anything foreign - example: inflammation
  • Specific: Adaptive immunity use B and T lymphocytes to attack foreign pathogens with lag time

Superficial Nonspecific Defenses

• Skin is the intact external membrane with the barrier that contains a layer of stratum corneum; dead cells that are avascular
  • Acid Mantle: Surface of the skin is slightly acidic creating cutaneous membrane's dry barrier
• Mucous Membrane lines all free body cavities secreting mucus
  • Traps substances and can destruct antigens, it contains protein-digesting enzymes: ex Gastric Juice

Internal Nonspecific Defenses - Phagocytes

• Macrophages were previous monocytes, accumulating enzymes
  • Free Macrophages float and get into other lymphatic organs
  • Fixed Macrophages: anchored to stroma
• Neutrophils diapedesis, circulate, and sometimes act as attracted to inflammation
• Eosinophils attack parasitic worms and also activate inflammation
• Phagocytic mechanism (phagocytosis) uses a recognition of carbohydrate surfaces for foreign antigens to be marked and destroyed by cells
  • 1. Phagocyte recognizes and binds to the pathogen
  • 2. Cytoplasmic extensions of phagocytic cell adhere to pathogen -- adherence
  • 3. Pathogen is pulled inside the cell into a vacuole
  • 4. Lysosome binds with phagosome -- phagolysosome
  • 5. Lysosomal enzymes digest (break down) the pathogen
  • 6. Residual body formed and then expelled

Internal Nonspecific Defenses - Other Cells

• Mast cells are somewhat phagocytic, killing bacteria by ingesting and using enzymes
• Natural killer cells are lymphocytes that attack anything, destroying virally infected cells and doesn't follow other phagocytes' mechanism
  • Natural killer mechanism detects infected/cancer cells by altered surface markers. When detected they release perforins (Perforin: a chemical)
• Inflammation occurs if the barrier to entry has breached and accumulates cells to attack antigen with a purpose set up for repair and is noted with 4 signs of inflammation: redness, heat, swelling, pain
  • Vessels dilate due to chemical interaction
  • Increased blood flow/ fluid can occur when selectins or adhesion occur
  • There will inflammation causing escape of selectins and neutrophils
  • Monocytes will follow after

Antimicrobial Proteins and Fever

• Interferon is a chemical secreted by the cells protecting it's neighboring cells by releasing, stimulate and interacting with another cell
  • A virally infected cell releases interferons that diffuses nearby stimulating the cells and when neighbors interact PKR protein (Interrupt of viruses) synthesis is stimulated
  • It also activates macrophages and natural killer cells
• Complement system is a group of 20+ proteins in the blood stream by being more inactive and when activated this kills microorganism or prevents replication otherwise stimulating inflammation
  • Mechanisms:
    • Abs bind to Pathogens with this non specific pathway the complex or inflammation may occur
    • Complement binds to poly saccharide molecules that result in Pathogens, lysis, phagocytosis
• Fever is an Elevated body temperature as an defense and systemic response
  • Uses of leukocites, pyrogens to raise body temp where hypothalamus is, generating heat and causing bacteria to destroy because of the iron and liquids lost

Antigens and Specific Immunity

• Antigens activate it's immune functions and is defined through the any foreign substance
  • Is identified with immunogenicity and to have reactivity
  • Recognizable of antigen determinants on a surface within Markers
• Major Histocompatibility Complex: Self Antigens are markers and not immunogenic to ourselves
• Characteristics of immunity contains systemic responses , and is activated through pathogen pathways

Humoral and Cell Mediated Pathways and Lymphocytes

• Humoral: Antibody and foreign mediated and virus that get marked by antibodies
• Cell is mediated by a bind of those infected and act through to destroy
• All Lymphocyte are produced in a bone marrow
• Once matured get put in Immune systems in Lymph Nodes
• Then, every cell has a cell marker on its surface

Antigen and Humoral Responses

• Antigen presenting cell (APCs) engulfs the pathogen, and presents the pathogens.
• First encounter between lymphocyte and antigen
  • The humoral response consists of free antigens that binds where a clone occurs that is then copied to be cells and most become plasma cells with antibodies
  • These plasma cells will create new cells for memory the response is secondary

Immune Response and Humoral Immunity

• The immune response is more effector through time and is measured because bodies is able to respond
• Types of Humoral Immunity: active( body produces antibodies), passive (harvesting) or artificial passive( infection or vaccine

Antibodies

• The structure has 4 subunits with heavy/light chains that connect to a a specific area where it determined through attachments
• Subunits
  • IgD can mark things faster and has receptors
  • IgG is most abundant by binding and crossing placentas
  • IgE binds mast cells and basophils
  • IgA are activated and have binding sites that help in the secretion
  • IgM finds a recent exposure by activating, fixating, and agglutinating the attachment

Antibody and Cell-Mediated Functions

• Formation of antibodies that attract proteins when blocking other pathogens.
• Takes out if action by destroying with Agglutination or Precipitation.
• In cell is T cell uses stimulatory and receptors and binding to activate

Types of T Cells

• Types of T Cells:
  • Natural Killers have glycol to protect it
  • Cytotoxic Specific: CD8 lyse
  • Helper B: cd4
  • Suppressor for actions
  • Involves Congenital deficiencies

Immune and Autoimmune Disorders

• With genetic decreases within bodies or caused through immunodeficiencies a system can attack itself - Will occur skin and joins with Rhemoid arthritis
• Hysensitivites happens with responses allergens or quick reactions - Can cause Anaphylaxis or reactions over time period through transplantation

Respiratory System Basics

• The respiratory system is tasked with supplying oxygen and removing carbon dioxide
• The process is named due to cellular respiration and Includes:
  • Pulmonary respiration (air in and out),
  • External respiration (between lungs and blood),
  • Gaseous transport (circulation of gases), and
  • Internal respiration.

Respiratory Apparatus

• Normal air entry path is through the nose
  • Involves Nasul cavity
  • Also involves Pharanyx and Larynx
  • Lastly the Trachea.
• Outside lungs:
  • The apparatus includes the primary, secondary, and tertiary bronchi, terminal bronchioles, alveoli, which are sacs.

Respiratory Zone

• Site of gas exchange, involving microscopic respiratory bronchioles and alveoli with large surface area. Conducting Zone:
• Terminal bronchioles and up, anything larger, just a pathway with rigid structure that does not collapse to improve efficiency. Functions:
• No gas exchange occurs here. Functions:
• No gas exchange occurs here.
• Cleans air, humidifies air if lungs are to dry, and warms the air.

Respiratory System: Nose and Pharynx

• Nose: External entry has and functions of passageway to warm and filter due to echoing, vibrissae, or olfactory. Nasal Cavity:
• The nostrils in vestibule contains stiff, thick hair. Internal nares are constricted with paranasal sinuses that contains air in the tissue
• Hard and soft palate separates the nasal and oral that allow to breath while eating Nasal muscose with olfactory:
• With receptors and respiratory of ciliated colunar with goblet cells and glands

Respiratory System: Pharynx

• Pharynx connects with nasal and oral cavity
  • The Nasopharynx with nasal which has Uvula to prevent backs up. It includes the P and PCEE that mostens air
  • The Oropharynx directs with cells, the Laryngopharynx separates

Larynx

• Larynx Very is very rigid but can direct food - Adam's apple: Open and buzzing voice - Vocal structures by ballon and tension
• Glotis: Pathway

Lower Respiratory Structures

• The lungs run from the neck through passageways to the mediastinum
  • It constricts air though structures that constricts as air vibrates, the pitch can be tuned with a volume to push
• Trachea runs from neck to mediastinum and branches towards bronchi - Layers contains: PCCE and Submucosal: , Tracheal - Bronchi: First, and secondary
• The bronchioles: gets small towards terminal and Respiratory - The further the diameter the epithelium will switch

Lungs - Key features

• Gas is able to be taken out and in
• The structures are enclosed by a plural activity for ventilation
• Alveolar Structure includes:
  • The alveolar: Make of simple one layer
  • Has Capillaries on the outside with respiratory: The cells are lined
  • Connected to pores to increase efficiency
  • Macrophages: The lungs must remain clean for their proper.
• Functions or Structure: and pleural cavities for fluids, ventilation and its regulated as pressure for high and low
• The ability to volume has compliance and pressure

Respiratory Processes & Regulation

• Atmoshpheric and Boyle's Law regulates pressure and breathing. Also depends with Musclar d, or intercontal Muscles
• Measured in: Tidal to indicate is air that get inhaled and exhaled has: The air that gets left through collapse with no changes that has affects with respiration and lung capacity
• The atmospheric measures Nitrogen, oxygen, dioxide, and water