Lymphatic System Functions and Structures

Study Notes

Lymphatic System Functions

Fluid Balance: Plasma (blood) → tissue fluid (between cells) → lymph (lymphatic system).
Lipid Absorption: Lacteals in small intestines absorb lipids.
Immunity: The lymphatic system plays a crucial role in the body's immune response.

Lymphatic Vasculature

Lymph capillaries are the smallest and are closed-ended.
Lymph vessels are larger with valves to prevent backflow.
Lymph flows: Capillaries → Vessels → Trunks → Ducts → Subclavian Veins.
Lymph movement is aided by skeletal muscle contractions and breathing.
Inadequate movement can cause swelling (edema).

Lymph Organs

Tonsils (lymph nodules): Guard oral and nasal openings.
- Palatine, pharyngeal (adenoids), and lingual are types.
Lymph Nodes: Found along lymph vessels, filter lymph for pathogens, contain white blood cells (WBCs).
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: Some pathogens infect only certain species.
- Mechanical Barriers: Skin and mucous membranes.
- Chemical Barriers: Enzymes destroy bacteria; complement proteins enhance inflammation; interferons protect cells from viruses.
- Phagocytes: Neutrophils, monocytes, and macrophages.
- Natural Killer (NK) Cells: Attack tumor and virus-infected cells using perforin.
- Inflammatory Response: Vasodilation (increased blood flow and WBCs); chemotaxis (damaged tissues attract WBCs); increased vascular permeability (additional fluid, complement, and fibrinogen leave blood vessels).
- Fever: Decreases pathogen activity and increases phagocyte rate.
Specific Immunity:
- All cells have antigens (protein markers) on their membranes. -Self-antigens: Body's own cells -Foreign antigens: Non-self proteins -Specific antibodies exist in plasma against foreign antigens.
B lymphocytes (B cells) and Humoral Immunity:
- Originate in bone marrow, mature in bone marrow.
- Specific B cells bind foreign antigens.
- Helper T cells stimulate specific B cells through cytokines.
- B cells divide and produce antibodies against the specific antigen.
- Some B cells become memory B cells.
Types of Antibodies (Immunoglobulins, Igs):
- IgA: Exocrine secretions.
- IgG: Activates complement.
- IgM: Anti-A, anti-B, anti-Rh.
- IgD: On B cell surfaces.
- IgE: Allergies.
Antibody functions: Agglutination, complement activation, phagocytosis enhancement, inflammatory chemical triggers, foreign antigen blockage.
- Immune Responses: Primary (initial antibody response) and secondary (faster and stronger antibody response).
- Immune Classes:
  - Natural active: Natural exposure to antigens.
  - Artificial active: Induced exposure to antigens.
  - Natural passive: Antibodies transferred to infant.
  - Artificial passive: Antibodies transferred from a recovered individual.
T lymphocytes (T cells) and Cellular Immunity:
- Macrophages display foreign antigens on MHC proteins.
- Helper T cells trigger cytotoxic (CTL) T cells to divide.
- CTL cells directly destroy pathogens.
- Some CTL cells become memory T cells.

Immune System Problems

Allergies: Non-harmful allergen triggers an immune response.
Tissue Rejection: Organ and blood transplants.
Autoimmunity: Immune system misidentifies self as foreign.

Digestive System (Chapter 15)

Chemical Digestion: Uses enzymes to break down macromolecules.
Mechanical Digestion: Uses physical methods to break down macromolecules.

Alimentary Canal

The alimentary canal encompasses the mouth to anus with layers of the wall comprising:
- Mucosa: Inner layer (mucous membrane).
- Submucosa: Contains glands, nerves, blood, and lymph vessels.
- Muscularis: Contains smooth muscle.
- Serosa: Outer layer (serous membrane).

Mouth

Food entry point.
Cheeks with mastication muscles.
Lips with temperature and texture receptors.
Tongue for taste and food movement during chewing.
Teeth for tearing and grinding.

Description

Explore the essential functions and structural components of the lymphatic system, including fluid balance, lipid absorption, and immune response. Understand the organization of lymphatic vasculature and the roles of lymph organs such as tonsils, lymph nodes, and the spleen.