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The Lymphatic System. Biology 2122 Chapter 20. Functions of the Lymphatic System. 1. Drain Excess ‘interstitial’ fluid 2-3 L of fluid lost from the blood stream/day 2. Transport dietary lipids From GI tract to the blood (lipids and lipid-soluble vitamins) 3. Immune Response

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The lymphatic system

The Lymphatic System

Biology 2122

Chapter 20


Functions of the lymphatic system
Functions of the Lymphatic System

1. Drain Excess ‘interstitial’ fluid

  • 2-3 L of fluid lost from the blood stream/day

    2. Transport dietary lipids

  • From GI tract to the blood (lipids and lipid-soluble vitamins)

    3. Immune Response

  • A. Cell-mediated response

    • T-cell response (cytotoxic cells destroy antigens)

  • B. Humoral – response

    • Antibody-mediated (B-Cells)


Basic structure
Basic Structure

1. Lymph Fluid

  • Interstitial fluid ------ lymph capillaries

    2. Lymph Vessels

  • Capillaries, ducts, etc.

    3. Lymph Tissue and Organs

  • Specialized reticular tissue

  • Large numbers of lymphocytes

  • Organs: Thymus gland; Tonsils; Spleen


Tissues to the heart
Tissues to the Heart

Lost lymph fluid - returned to the heart.

1. Capillaries

  • Endothelial Cells and mini-valves

    • Supported by collagen

    • One way pressure from the capillaries move lymph towards the capillaries

  • Very permeable

    2. Capillaries form vessels

  • Skin follow veins; viscera follow path of arteries

  • Lymph flows into the nodes

  • No lymph vessels (cartilage, epidermis, cornea- all avacular); CNS

    and red bone marrow


Chyle and lacteals
Chyle and Lacteals

Lipids absorption take place in the small intestine

Lacteals

  • Small capillaries in the absorptive cells

  • Lipids transported from lacteals into the blood

    • Specialized lipid absorption

      Chyle

  • In small intestine lymph is white or creamy due to lipid presence (lymph is normally clear)


Flow and structure
Flow and Structure

Capillaries ----- Collecting vessels ---- Nodes --- Trunks ------ Lymph ducts (thoracic and right lymphatic) ----- Internal jugular and Subclavian vein ---- Heart


On the way to the heart
On the way to the heart

1. Trunks – lumbar, intestinal, bronchomediastinal, subclavian, jugular

  • A. lumbar

  • B. intestinal

  • C. bronchomediastinal

  • D. subclavian

  • E. Jugular

    2. Thoracic (left lymphatic) duct

  • Cisterna chyli

  • Main duct for return of lymph to blood from left side of body

  • Drains into the L.internal jugular and L.subclavian vein


On the way to the heart1
On the way to the heart

3. Right lymphatic duct

  • Receives lymph from right side of the body

  • Drains blood into venous blood at junction of R. internal jugular and R. subclavian veins


Flow of lymph against gravity
Flow of Lymph against Gravity

Same problems as encountered by venous return

Pumps

  • 1. Skeletal system pump

  • 2. Respiratory pump

Organs and Tissues


Organs and tissues
Organs and Tissues

1. Primary Organs – stem cell division produces mature cells – immunocompetent

  • Red bone marrow

    • B – cells; pre-T cells

  • Thymus

    • Pre-T cells migrate to thymus to become immunocompetent

      2. Secondary Organs

  • Site of immune system response

  • Nodes, spleen, nodules


Thymus
Thymus

  • Bi-lobed- surrounded by CT and separated by capsule

  • Trabeculae -separates tissue into lobes

  • Lobe

    • Cortex -(T-cells and Dendritic cells, Epithelial cells and Macrophages)

    • Medulla – mature T-cells, dendritic cells and macrophoges

    • Thymic(Hassal’s corpusles)


Lymph nodes
Lymph Nodes

Lymphatic Nodules

  • B-cells (primary lymphatic nodule)

  • Plasma and memory B cells in outer cortex (secondary lymphatic nodule)

    B-cell in primary nodule recognizes antigen and transforms into a secondary nodule

  • Germinal center

  • B-cells, follicular dendritic cells, macrophages

    Antigen presented by APC (B-cell; dendritic , etc.) B- cells develop into plasma and memory cells

    Inner cortex and medulla

  • Covered by Dense CT capsule


Spleen
Spleen

Covered by Dense CT capsule

Visceral peritoneum – serous membrane

Stroma

  • Trabeculae, reticular fibers and fibroblasts

    Parenchyma

  • 1. White pulp – lymphocytes and macrophages around central arteries (splenic artery branches)

  • 2. Red pulp – venous sinuses, cords of splenic tissue or splenic cords (RBCs, macrophages, lymphocytes, plasma cells, granulocytes


Nodules
Nodules

  • No capsule

  • Found in mucous membranes (near lamina propria) in GI tract, urinary, reproductive, respiratory airways

    • “Mucosa-associated lymphatic tissue (MALT)

  • Can be small or larger tissue

    • Tonsils (5)-Pharyngeal area

      • Pharyngeal (adenoid- posterior nasopharynx)

      • Palatine (2)-posterior region of oral cavity (tonsillectomy)

      • Lingual (2)-base of tongue


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