20 The Lymphatic System

The Lymphatic SystemLymphatic System:

1. lymphatic vessels

2. lymph

3. lymph nodes

*returns "leaked" fluid to bloodstream

*supports CV system

Lymphoid Organs & Tissues:

1. spleen

2. thymus

3. tonsils

4. other (Peyer's patches)

*discrete organs/tissues

aiding in defense

*supports immune system

They can't all be superstars!

Keeps us healthy!

Circulation, BP, clotting, etc...

Supports immune & cardiovascular

system!

• produces, maintains and distributes lymphocytes (cells that attack invading organisms, abnormal cells, and foreign proteins) - lymphoid organs/tissues• helps maintain blood volume and the consistency of interstitial fluid (fluid forced out of arteries and reabsorbed by veins) - lymphatic system

Functions

colloid osmotic pressure due to proteins in blood (albumins) - constant IN voice

OUT

IN

hydrostatic blood pressure due to contraction of left ventricle- diminishing OUT voice

IN

OUT

HOW DO CAPILLARIES EXCHANGE NUTRIENTS/WASTES?

*most fluid forces out "upstream" is reabsorbed "downstream"

*to maintain proper blood volume, whatever is not reabsorbed needs to be returned to bloodstream

*lymphatic vessels return about 3L of "leaked" fluid, plasma proteins, and digested fats per day

"upstream"

"downstream"

Lymphatic Vessels & Lymph• lymphatic vessels

> elaborate network of one-way vessels that lead toward heart (R side)

> not in bones/teeth, bone marrow, or CNS

• lymphatic capillaries - EXTREMELY PERMEABLE

> minivalves open when pressure greater outside than in

• lymph - fluid inside vessels

> similar to blood plasma

20 The Lymphatic System

1 Lymphatic vessels originate in

A lymph fluid

B tonsils

C tissue capillaries

D lymph nodes

2 ____ is the fluid found inside lymphatic vessels.

3 Functions of the lymphatic system (defense and reabsorption of fluid) supports the actions of the

A cardiovascular system

B nervous system

C respiratory system

D immune system

4 Fluid enters lymphatic capillaries when the pressure ____ is greater than the pressure ____ the capillary.

A inside, surrounding

B inside, outside

C outside, inside

D outside, surrounding

20 The Lymphatic System

Lymphoid Cells • lymphoid cells - lymphocytes

main warriors of the immune systemT cells (thymus-dependent)

responsible for cell-mediated immunitycytotoxic T cells - attack foreign cells, abnormal body

cells, and cells infected by virusesregulatory T cells - regulate and coordinate the

immune response (helper T cells and suppressor T cells)B cells (bone marrow-dependent)

responsible for antibody-mediated immunitydifferentiate into plasma cells, which produce and

secrete antibodies that react with or bind to antigensantibodies = immunoglobulins

macrophages - phagocytize foreign substances and help activate T cells

dendritic cells - capture pathogens and bring them to lymph nodes

(attack invader)

cells

body cells

MHC I

I'm infected I die

presenting (APC)non-presenting

MHC II

macro, dendritic, B cells

under attack... here's invader

activate TH

activate B & TC

memory cells for later

(one and done) (two I'll help you)

(attack infected cells)

5 B cells are responsible for __________-mediated immunity. 6 T cells mature in the

A spleen

B lymph nodes

C tonsils

D thymus

20 The Lymphatic System

Lymphoid Tissue• collections of loose connective tissue and lymphocytes found in nodules• full of macrophages• functions

house lymphocytesideal surveillance vantage point

• found in all lymphoid organs EXCEPT thymus

lymphocytes macrophages

Normal Intestine

Damaged Intestine due to HIV Infection

Follicular lymphoid tissue - solid, tightly packed

*enlarge when B cells dividing into plasma cells

Diffuse lymphoid tissue - scattered, loosely packed

Lymphoid Organs - Lymph Nodes• principle lymphoid organ (100s embedded in

connective tissues throughout body)

• large superficial groups in inguinal, axillary, and cervical regions

• 2 functions

> "filter" lymph returning to bloodstream

> help activate immune response

afferent

efferent

Lymphoid Organs - Lymph Nodes

7 MATA: What type of cells are stored in lymph nodes?

A macrophages

B immunoglobulins

C plasma cells

D lymphocytes

THINK ABOUT IT...WHAT IS THE JOB OF A LYMPH NODE AND WHAT

WOULD HELP ACHIEVE THIS

FUNCTION?

20 The Lymphatic System

8 The main difference between diffuse and follicular lymphoid tissue is

A their location in the body

B their function

Cthe flow of blood through their structure

Dhow they are "packaged" (tightly or loosely)

Other Lymphoid Organs• tonsils - simplest lymphoid organ

gather and remove many pathogens entering pharynx in food or inhaled air

4 sets: palatine, lingual, pharyngeal (adenoids), tubal • spleen - largest lymphoid organ

lymphocyte proliferation, immune surveillance, removes defective blood cells and platelets from blood, stores platelets, stores iron obtained from recycled RBCs

• thymusatrophies as we age (most active in young children)where T cells mature and are stored

*tubal not shown

9 MATA: Choose the lymphoid organs.

A lymph nodes

B tonsils

C thymus

D spleen

10 The largest lymphatic organ is the ______.