The lymphatic system immune system
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The Lymphatic System Immune System. Consists of two semi-independent parts Lymphatic vessels Lymphoid tissues and organs Lymphatic system functions Transports escaped fluids back to the blood Plays essential roles in body defense and resistance to disease. Lymphatic Characteristics.

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The lymphatic system immune system
The Lymphatic SystemImmune System

  • Consists of two semi-independent parts

    • Lymphatic vessels

    • Lymphoid tissues and organs

  • Lymphatic system functions

    • Transports escaped fluids back to the blood

    • Plays essential roles in body defense and resistance to disease


Lymphatic characteristics
Lymphatic Characteristics

  • Lymph—excess tissue fluid carried by lymphatic vessels

  • Properties of lymphatic vessels

    • One way system toward the heart

    • No pump

    • Lymph moves toward the heart

      • Milking action of skeletal muscle

      • Rhythmic contraction of smooth muscle in vessel walls


Venous

system

Arterial

system

Heart

Lymph duct

Lymph trunk

Lymph node

Lymphatic

system

Lymphatic

collecting

vessels,

with valves

Lymph

capillary

Tissue fluid

(becomes

lymph)

Blood

capillaries

Loose connective

tissue around

capillaries

Figure 12.1


Tissue fluid

Tissue cell

Lymphatic

capillary

Blood

capillaries

Arteriole

Venule

(a)

Figure 12.2a


Lymph
Lymph

  • Harmful materials that enter lymph vessels

    • Bacteria

    • Viruses

    • Cancer cells

    • Cell debris


Lymph nodes
Lymph Nodes

  • Filter lymph before it is returned to the blood

  • Defense cells within lymph nodes

    • Macrophages—engulf and destroy foreign substances

    • Lymphocytes—provide immune response to antigens


Entrance of right

lymphatic duct into right

subclavian vein

Regional

lymph nodes:

Cervical

nodes

Internal jugular vein

Thoracic duct

entry into left

subclavian vein

Axillary

nodes

Thoracic duct

Aorta

Spleen

Cisterna chyli (receives

lymph drainage from

digestive organs)

Inguinal

nodes

Lymphatics

KEY:

Drained by the right lymphatic duct

Drained by the thoracic duct

Figure 12.3


Tonsils (in

pharyngeal region)

Thymus (in thorax;

most active during

youth)

Spleen (curves

around left side of

stomach)

Peyer’s patches

(in intestine)

Appendix

Figure 12.5


Spleen
Spleen

  • Located on the left side of the abdomen

  • Filters blood

  • Destroys worn out blood cells

  • Forms blood cells in the fetus

  • Acts as a blood reservoir


Thymus gland
Thymus Gland

  • Located low in the throat, overlying the heart

  • Functions at peak levels only during childhood

  • Produces hormones (like thymosin) to program lymphocytes


Tonsils
Tonsils

  • Small masses of lymphoid tissue around the pharynx

  • Trap and remove bacteria and other foreign materials

  • Tonsillitis is caused by congestion with bacteria


Peyer s patches
Peyer’s Patches

  • Found in the wall of the small intestine

  • Resemble tonsils in structure

  • Capture and destroy bacteria in the intestine


Surface membrane barriers first line of defense
Surface Membrane Barriers:First Line of Defense

  • Skin and mucous membranes

    • Physical barrier to foreign materials

    • Also provide protective secretions

      • pH of the skin is acidic to inhibit bacterial growth

      • Sebum is toxic to bacteria

      • Vaginal secretions are very acidic

      • Antimicrobial proteins – lysozyme – in saliva, tears

      • Cilia in trachea

      • Gastric juice

      • Symbiotic bacteria in gastric tract


Non specific barriers
Non-specific barriers

  • Phagocytes – engulf antigens, neutrophils, monocytes, NK cells (attack tumors)

  • Complement proteins – lyse the cell wall of the antigen

  • Interferons – produced by already invaded cells, inhibit viral replication

  • Inflammatory response – swelling, histamine release, vasodilation


Types of immune cells
Types of Immune Cells

  • Immune cells target specific antigens

  • Lymphocytes – B cells and T cells

  • B-cells – originate and mature in bone marrow. Produce antibodies

  • T-cells – produced in bone marrow, reside in thymus

  • MHC (major histocompatibility complex) markers are on plasma membranes and distinguish self vs. non self cells


Cell mediated response
Cell-Mediated Response

  • T cells recognize the antigen MHC markers

  • They activate other T-cells – memory and helper

  • The T-helpers activate B-cells – AIDS wipes out T-helpers

  • T-memory cells “remember” if they have “seen” the virus before

  • Cytotoxic T-cells kill infected cells


Humoral response
Humoral Response

  • Antibody mediated response

  • Immunoglobulins – 5 classes

  • When B-cells encounted macrophages that are displaying antigen MHC markers

  • Some B-cells become memory cells for those markers

  • They produce antibodies that bind to antigens

  • They will work for future infections




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