Download Lymphatic Lecture Notes Page

LYMPHATIC SYSTEM
Lymphatic System - functions
 Returns excess interstitial fluid (lymph) to
blood (including lost plasma proteins)
 Transports dietary lipids from digestive system
to blood
 Carries out Immune responses including:
- Production & Differentiation of Lymphocytes
- Formation of Antibodies
- Other specific responses against microbes or abnormal
cells
24-2
Lymphatic System
Components
Lymph - fluid
Lymphatic Vessels – transport lymph
- capillaries, vessels, trunks & ducts
Lymphatic Organs and Tissues
- Primary: red bone marrow & thymus
- Secondary: lymph nodes, spleen, lymphatic
nodules
Lymph
Fluid, similar to plasma
Lost from blood capillaries
Enters lymphatic system at lymph
capillaries
About 3 liters of interstitial fluid drain into
lymph vessels daily
Returned to bloodstream by series of
lymph vessels
Lymph & Blood Capillaries
Intertwine
Lymph Vessels/Lymphatics
 Transport Lymph (one-way) to Blood
(Subclavian Veins)
 Under low pressure
 Lymph flow assisted by:
 Muscular compression
 One-way valves to prevent backflow
 Respiratory pump
 Rhythmically contracting smooth muscle in
walls of largest lymphatics
Lymphatic Ducts
 Two main channels drain lymph into veins:
 Thoracic Duct
 Begins as Cisterna Chyli - receives fatty
lymph (chyle) from Digestive Organs
 Drains Lower Body + Upper Lt. Half into
Lt. Subclavian Vein
 Right Lymphatic Duct
 Drains Upper Rt. Half into Rt. Subclavian
Vein
10
Lymphatic Organs/Tissues Primary
 Site of lymphocyte development (from stem cells)
 Red bone marrow
- Mature B cells
- Immature T cells
 Thymus
- T cells mature &
differentiate
- Site of T-Cell maturation (immunocompetence);
able to mount immune response
Thymus
(Primary Lymphatic Organ)
Mediastinum, between sternum & aorta
Atrophies after puberty
Populates secondary lymphatic organs &
tissues with T-cells
Lymphatic Organs/Tissues Secondary
Sites where most immune responses occur
- Lymph nodes
- Spleen
- Lymphatic Nodules
*M.A.L.T.
*Tonsils
Lymph Nodes
Secondary Lymphatic Organs
Located along lymph vessels
Often in clusters, receiving lymph from
specific regions
Filter Lymph; lymph enters through
afferent vessels, exits through efferent
vessels
Site of proliferation of B cells & T cells
Spleen
Secondary Lymphatic Organ
 Blood filtered
 Macrophages phagocytize
pathogens; lymphocytes
perform immune functions
 Recycles RBCs & Stores
Iron
 Stores blood & platelets
Lymphatic Nodules
Secondary Lymphatic Tissues
Mucosa-associated lymphatic tissue
(M.A.L.T.)
Nodules in mucosa of G.I., urinary,
reproductive tracts & respiratory airways
- Tonsils in pharynx (protect against
inhaled/ingested foreign substances)
- Peyer’s patches (Lymph nodules) in small
intestine
Immune System
Functions
Antigens are substances capable of triggering
an immune response. The Immune System:
Patrols for antigens
Recognizes, responds to, and eliminates
foreign antigens
Scavenges dead or dying cells
Three Immune Strategies
1. Physical, chemical, & mechanical barriers
to prevent entry
Then to identify, and remove or neutralize
invader:
2. General (non-specific) Immune Defense
3. Specific Immune Responses
Physical Barriers
Intact skin
Nasal hairs
Mucous membranes
Sphincters to inhibit bacterial migration
Chemical Barriers
Low pH of stomach
Urine
Vaginal secretions
Sebum on skin
Lysozyme in tears
Prostatic secretions
Mechanical Barriers
Cell turn over
Trapping action of mucus
Cilia
Flushing action of tears, saliva, urine,
defecation
General Non-Specific Defenses
Phagocytes – Neutrophils, Macrophages
Natural Killer Cells – lymphocytes that
lyse/kill abnormal cells (cancerous &
virus-infected cells)
Proteins – complement & interferon
Inflammation – vasodilation & increased
capillary permeability (redness, heat,
swelling, pain)
Fever
Specific Immune Responses
Antigen-specific (relies on recognition of
foreign antigens)
Systemic (body-wide)
Forms Memory (stronger future immune
response)
2 types of Immune Response:
- Humoral (Antibody-Mediated)
- Cellular (Cell-Mediated)
Humoral Immunity
B-Cells (B-Lymphocytes)
- Mature in Bone Marrow
- Divide to form:
*Plasma Cells (Produce Antibodies)
*Memory B Cells
- Antibodies disable Bacteria & Viruses
before they enter cells
Cellular Immunity
T-Cells (T-lymphocytes)
- Mature in thymus
- Form memory T cells
- Directly attack Bacteria & Viruses
- Attack virus-infected cells &
cancerous cells
- Influence B Cell Activity
Major Types of T-Cells
Helper T-cells
- Activate B & T-cells specific immunity
- Trigger B & T-cell proliferation
Cytotoxic/Killer T-cells
- Attack & kill other cells (e.g. virus-infected
cells, cancer cells, donor cells, cells with
bacteria or other intracellular parasites)
Regulatory T-cells
- Inhibit (dampen) the immune response