The Lymphatic Sys (pgs 772-783)

 

v     Lymphatic Sys

      2 purposes

        Carry lymph (draining body tissues- excess fluid from blood capillaries that went into interstitial space)

        Immune sys (2 functions)

       Gives lymphocytes a home

       Sends lymph past WBC

 

v     Blood capillary

      Open at both ends

 

v     Lymph capillary (see diag. 20.1 pg 773)

      One end open, one dead end

        One way trap door

      Very permeable

        More fluid

      3L/day into lymphatic sys: called lymph (clear H2O)

        Stuff that can get out of blood capillary ] except blood proteins (ex albumin)

 

v     Differences between Blood & Lymph Capillaries

      Blood

        Open @ both ends

        Permeable

        Go everywhere

      Lymph

        Closed @ 1 end

        VERY, VERY PERMEABLE

        Not in bone, teeth or CNS

 

v     Lymph & Lymph Cap.

      Very permeable

        Anything can get in, but cant go into blood capillaries

      Valves

        Act as trap doors

      No tight/gap junctions

 

 

v     Lymphatic Sys

      Lots of WBCs patrolling what goes by

      Monocytes & macrophages

 

v     Infection

      Lymph nodes swell

9     permanent home of B cells

       T cells " thymus, travels

        Cancer cells & pathogens

       Handled by Immune sys & lymph nodes

 

v     Lacteals

      Specialized lymphatic cap.

      Intestines

      Chyle

        Fatty lymph

        Not clear: milky, creamy

 

v     Differences between lymphatic & blood vessels

      Lymphatic

        Thinner walls

        More anastomoses

        More valves

 

v     Lymph Vessels

      3 layers (same as b.v.)

 

v     Flow of Lymph

      Capillaries

      Vessels (collecting)

        Same tunics as veins

        Thinner walls

        More valves & anastomoses

      Trunks

        Drain large portions of body

        More, smaller

       Paired

      Lumbar

      Bronchomediastinal

      Subclavian

      Jugular

       Single

      Intestinal

      Ducts

        Thoracic duct

       Drains most of body

       Empties into internal jugular vein & subclavian vein

        R. Lymphatic duct

       Drains R. arm, R. head & thorax

 

v     Lymph Transport

      Lower pressure than b.v.

      No pump (ex. like heart)

        Musc. Pump

        Respiratory pump

        Valves prevent backflow

        Pulsation of nearby arteries

        Smooth musc peristalsis (rhythmically)

       Trunks & ducts

      Flow is still sporadic & slow

 

v     Bad infection

      Rest = immobilization

        Hinders flow of inflammatory material throughout body

 

v     Lymphoid Cells (see Immune Handout)

      Lymphocytes

        T cells (Cytotoxic and Helper)

       Manage immune response

       Attack invading cells

       Becomes immunocompetent in Thymus

        B cells

       Make plasma cells (antibodies) & memory cells

       Becomes immunocompetent in bone marrow

      Macrophages & Dendritic Cells

        Eat foreign cells

        Help activate T cells

      Reticular cell

        Produce stroma (network made of fiber that supports other cell types in lymphoid organs)

        Provide structure

 

v     Lymphoid Tissue

      2 purposes

        Where lymphocytes live and reproduce

        Surveillance mechanism for lymphocytes & macrophages

      Reticular CT

        Macrophages on fibers

        Lymphocytes spaces of network

       Travel in circuit from lymph. tissues → blood → loose CT

      Diffuse lymphatic tissue

        No capsule

        Scattered

        Found in all organs

        Most common in mucous membranes

      Lymphoid follicles (nodules)

        No capsule

        Tightly packed

        Germinal centers

       Light staining

       Dendritic & B cells

        Found forming lymph nodes, as Peyers patches in intestine & in appendix

      Lymph Nodes

        In CT

        2 functions

       Filter lymph

      Macrophages debris from CT & prevent it from entering blood & spreading to other parts of body

       Help activate immune sys

      Lymphocytes monitor lymphatic stream for antigens & mount attack against them

        Structure

       Capsule container of CT

       Trabecula strands of CT that extend inward and divide node into compartments

       Cortex

      Outside

      Superficial part

      Densely packed follicles

      Germinal centers

        B cells

      Deep part

      T cells in transit

       Medulla

      Medullary cords thin inward extensions of cortical tissue (from cortex)

      Contains lymphocytes & plasma cells

       Lymph (medullary) sinus

      Lymph capillaries spanned by crisscrossing reticular fibers

      Few cells (mostly macrophages)

      Lymph

        Circulation w/in lymph node

       Afferent

      Lymph Arrives at node

       Efferent

      Lymph Exits/Egresses node

       Subcapsular space

      Space below the capsule

       Hilus

      Indented region on concave side of node where the efferent vessels protrude off node

 

v     Other Lymphoid Organs

      All made up of reticular CT

      Spleen

        Largest lymphoid org

        L. side of abdominal cavity, curls around anterior aspect of stomach

        Lymphocyte reproduction & lots of macrophages

        Hilus

       One artery in (Splenic A.)

       One vein out (Splenic V.)

        Functions

       Extracting old & defective RBCs

       Store or release parts of old RBC

      Store iron in spleen

      Release bilirubin

       Make RBC (fetus only)

       Stores platelets

      Clotting

        White pulp

       Areas composed mostly of lymphocytes suspended on reticular fibers

       Small amounts

       Cluster around arteries

        Red pulp

       Remaining splenic tissue

       Cleans out damaged/worn-out RBCs & pathogens in blood

      Thymus

        2 lobes

        Located bottom of neck, top of thorax, & in front of heart

        Secretes hormones

       Thymosin

       Thymopietin

        Immunocompetency of T cells (stimulated by thymocytes)

        Does not directly fight antigens

        Blood thymus barrier

       Keeps antigens in blood from coming in contact w/ T cells

      Prevents premature activation of immature T cells

      T cell must recognize self b4 recognizing invaders

        No B cells

        No Reticular cells

      Tonsils (diag. 22.3 pg 832)

        Simplest lymph org

        Around entrance to throat

        Palatine tonsils (paired)

       Either side of posterior end of oral cavity

       Largest & most often infected

        Lingual tonsils (paired)

       Base of tongue

        Pharyngeal tonsil (single)

       Posterior wall of nasopharynx

        Tubal tonsils

       Opening of auditory tubes and pharynx

        Remove pathogens from food and air

        Follicles & germinal centers

       Lots of B cells & plasma cells

        Crypts

       Invaginations of surface epithelium

       Trap bacteria & particulate matter

      Invited into lymphoid tissue where destroyed

      Early warning sign against infections (memory B cells)

 

v     Aggregates of Lymphoid Follicles

      Peyers patches

        Clusters of lymphoid follicles in sm. Intestine

        Function similar to tonsil

        Crypt

      Appendix

        Blind pouch that comes off beginning of lg. intestine

        Contains lots of bacteria

        Lots of lymphoid tissue

       Lymphocytes

      Functions of Peyers patches & Appendix

        Destroy bacteria

        Make Memory B cell lymphocytes

       Provide long term immunity