Lymphatic System Functions and Structures

Lymphatic System Functions

• Fluid Balance: Blood plasma → tissue fluid → lymph.
• Lipid Absorption: Lacteals in small intestines absorb lipids.
• Immunity: Lymphatic system plays a role in immune responses.

Lymphatic Vasculature

• Lymph Capillaries: Smallest, closed-ended vessels.
• Lymph Vessels: Larger vessels with valves to prevent backflow.
• Lymph Flow: Lymph propelled by skeletal muscle, breathing.
• Edema: Inadequate lymph movement causes swelling.
• Lymph Path: Capillaries → Vessels → Trunks → Ducts → Subclavian Veins.

Lymph Organs

• Tonsils: Lymph nodules, guard oral/nasal openings.
  • Types: Palatine, Pharyngeal (adenoids), Lingual.
• Lymph Nodes: Filter lymph, contain white blood cells (WBCs). Located along lymph vessels.
• Spleen: Filters blood for pathogens.
  • White Pulp: Lymph tissue and WBCs.
  • Red Pulp: Blood vessels.
• Thymus: Site of T lymphocyte maturation.

Immunity

• Nonspecific Immunity:
  • Species Resistance: Pathogens infect specific species.
  • Mechanical Barriers: Skin and mucous membranes.
  • Chemical Barriers: Enzymes, complement proteins, interferons.
  • Phagocytes: Neutrophils, monocytes, macrophages.
  • Natural Killer (NK) Cells: Attack tumor/infected cells with perforin.
  • Inflammatory Response: Vasodilation, chemotaxis, increased vascular permeability, fever.
• Specific Immunity:
  • Antigens: Protein markers on cell membranes.
  • Self-antigens: Body's own cells.
  • Foreign Antigens: Non-self substances.
  • Antibodies: Plasma proteins against foreign antigens.

Lymphocytes ("B" and "T")

• Origin and Maturation: Both originate in red bone marrow; T cells mature in the thymus, B cells mature in bone marrow.
• B Cells and Humoral Immunity:
  • Recognize foreign antigens, produce antibodies.
  • Helper T cells stimulate B cell division/antibody production.
  • Memory B cells form for future responses.
• Antibody Types (Immunoglobulins - Ig): IgA, IgG, IgM, IgD, IgE. IgG activates complement. IgM targets A, B, and Rh antigens.
• Antibody Functions: Agglutination, complement activation, phagocytosis enhancement, inflammation triggering, antigen blocking.

Immune Responses

• Primary response: Initial antibody production.
• Secondary response: Faster, stronger antibody response (memory cells).
• Immunity Types: Natural active, artificial active, natural passive, artificial passive.

"T" Cells and Cellular Immunity

• MHC Proteins: Antigens displayed on cell membranes.
• Helper T Cells: Activate cytotoxic T cells, produce cytokines.
• Cytotoxic T (CT) Cells: Directly destroy infected cells.
• Memory T Cells: Form for future responses.

Immune System Problems

• Allergies: Immune response to harmless substances.
• Tissue Rejection: Rejection of transplanted organs/blood.
• Autoimmunity: Immune system attacks self-tissues.

Digestive System

• Digestion: Chemical (enzymes) and mechanical breakdown of macromolecules.
• Alimentary Canal: Tube from mouth to anus.
  • Layers: Mucosa (inner), Submucosa, Muscularis, Serosa (outer).
• Mouth: Ingestion, mastication (chewing), taste receptors, tongue.