1. Lymphatic System
Composition
Lymph Lymphocytes Lymph vessels Lymph nodes Tonsils Spleen Thymus gland
Function
1) Maintains fluid balance - 30 liters of plasma pass out of capillaries each day -
27 liters get resorbed at capillary - 3 liter left in tissue spaces get resorbed
into lymph vessels 2) Fat absorption from gastrointestinal tract - lacteals in
small intestine - lymph + fat = chyle (a milky white fluid) 3) Body defense system
- lymph nodes filter lymph contains lymphocytes - spleen filters blood
Lymph Vessels
Carry lymph away from tissues begins at lymph capillaries (simple squamous
epithelium) lymph capillaries join together to form vein-like lymph vessels lymph
vessel contain valves to prevent retrograde flow o contraction of skeletal muscle o
smooth muscle in lymph vessel wall o pressure changes in thorax during breathing
1) Right Lymphatic Duct (RLD) drains lymph from - right upper limb - vessels from
right halve of head, neck, & chest form the RLD which empties into the right
subclavian vein. 2) Thoracic Duct The rest of the body drains into the Thoracic
Duct which empties into the left subclavian vein.
Lymphatic Lecture Page 1

2. Lymph Organs
- Contain lymphatic tissue composed of lymphocytes, macrophages, & other cells. -
Lymphocytes originate from red bone marrow, and are carried by the blood to lymph
organs. - Microorganisms stimulate lymphocyte cell division in germinal centers of
lymph nodes. This is called Immune System Activation 1) Tonsils Protects body
against pathogens entering at the nose and mouth. a. palatine â “ posterior oral
cavity b. pharyngeal âr“ nasal cavity, adenoids c. lingual âe “ posterior tongue 2)
Lymph Nodes - Small, round structures along lymph vessels. - Lymph passes through
at least one node before emptying into vein. - Superficial aggregation Inguinal in
groin Axillary Cervical The function of a node is to filter lymph and produce
lymphocytes. 1) activation of the immune system (lymphocyte cell division) 2)
phagocytosis of pathogens by macrophages
3) Spleen Located in the left upper abdominal cavity Function: Filters blood of
pathogens and old RBCs Activation of immune system Blood reservoir Easily
traumatized 4) Thymus Located in the superior mediastinum Function: Maturation of
lymphcytes
Lymphatic Lecture Page 2

3. Defense or Resistance
Ability to resist damage from foreign substances.
Two kinds of defense.
1) Nonspecific Resistance
constant response time
versus
2) Specific Resistance
faster & faster response time
1) Nonspecific Resistance: Identical response time for repeat infections. Example;
each time a bacterium enters the body, it is phagocytized with the same speed &
efficiency. 2) Specific Resistance: The response for repeat infections is faster
and more efficient due to the ability to recognize (specificity) and remember a
particular antigen. Specific resistance also imparts long lasting immunity from a
pathogen, so it is also called Specific Immunity.
1) Nonspecific Resistance
A. Mechanical Mechanisms for preventing entry
- skin & mucous membranes - tears, saliva, urine wash out microorganisms - ciliated
mucous membranes in lungs - coughing and sneezing remove from respiratory tract
B. Chemical Mediators (4), bring about or focus immune system response
1. Lysozyme in tears and saliva 2. Histamine promotes inflammatory response by
vasodilating and increasing capillary permeability (producing edema & swelling) 3.
Compliment Eleven proteins in plasma are inactive, but are activated by bacteria or
antibodies. Active compliment promotes - Inflammation - Phagcytosis - Attracts WBCs
- Lysis of bacterial cells
Lymphatic Lecture Page 3

4. Nonspecific Resistance Chemical Mediators (cont.)
4. Interferons are proteins from infected cells that protect uninfected cells from
viral infection.
Virus Infected Cell
Interferons
Uninfected Cell
More viruses
Cell death
Antiviral Proteins
C. Cells, all WBCs except lymphocytes
White blood cells are the most important cellular component of the immune system.
Histamine and compliment attract WBCs.
- neutrophils (phagocytes) first to arrive - macrophages are monocytes that have
left blood vessels (5x bigger) - basophils release histamine - mast cell (not a
WBC) in connective tissue release inflammatory chemicals - eosinophils release
chemicals that break down inflammatory chemicals
Lymphatic Lecture Page 4

5. 2) Specific Resistance (a.k.a Immunity)
Due to an antibody/antigen reaction.
Specific resistance is the ability to recognize, respond, and remember a particular
antigen. Molecules which stimulate specific resistance are called antigens. 1)
Foreign Antigens - parasites - bacteria - viruses - toxins (chemicals) 2) Self
Antigens - tumors - autoimmune disease
multiple sclerosis rheumatoid arthritis
**Specific resistance results from lymphocyte activity!!**
Two types of Lymphocytes 1. B cells produce proteins called antibodies. Thus,
antibody mediated immunity is the result of B cells or B lymphocytes activity. 2. T
cells are contact killers. They lyse invading cells on contact. Thus, cell mediated
immunity is the result of T cells or T lymphocytes.
Lymphatic Lecture Page 5

6. I. Antibody Mediated Immunity (B-cell)
Works well for extracellular antigens.
A. Primary Response
Antigen binds to receptor on B lymphocyte.
B lymphocyte + Antigen
Plasma Cells
+
Memory B Cells (Provides long lasting immunity)
Antibodies
Primary response takes 3-14 days.
B. Secondary Response
Memory B cells are responsible for the secondary response for a repeat infection.
1. faster response time, will produce antibodies within a few hours 2. more
effective response, many more antibodies are produced
Lymphatic Lecture Page 6

7. II. Cell Mediated Immunity (T-cell)
Can work for intracellular antigens.
A. Primary Response
Antigen binds to receptor on T lymphocyte.
Cytotoxic T Cells
1) promotes inflammation 2) promotes phagocytosis 3) contact killing
Memory T Cells
(long lasting immunity)
Primary response takes 3-14 days.
B. Secondary Response
Memory T cells are responsible for the secondary response for a repeat infection.
1. faster response time, will produce cytotoxic T cells within quickly 2. more
effective response, many more cytotoxic T cells are produced
Lymphatic Lecture Page 7