The Lymphatic Sys
(pgs 772-783)
v
Lymphatic Sys
Ø
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
Ø
Open
at both ends
v
Lymph capillary (see diag. 20.1 pg
773)
Ø
One
end open, one dead end
§
One
way trap door
Ø
Very
permeable
§
More
fluid
Ø
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
Ø
Blood
§
Open @
both ends
§
Permeable
§
Go
everywhere
Ø
Lymph
§
Closed
@ 1 end
§
VERY,
VERY PERMEABLE
§
Not in
bone, teeth or CNS
v
Lymph & Lymph Cap.
Ø
Very
permeable
§
Anything
can get in, but can’t go into blood capillaries
Ø
Valves
§
Act as
trap doors
Ø
No
tight/gap junctions
v
Lymphatic Sys
Ø
Lots
of WBCs patrolling what goes by
Ø
Monocytes
& macrophages
v
Infection
Ø
Lymph
nodes swell
9
permanent
home of B cells
·
T
cells " thymus, travels
§
Cancer
cells & pathogens
·
Handled
by Immune sys & lymph nodes
v
Lacteals
Ø
Specialized
lymphatic cap.
Ø
Intestines
Ø
Chyle
§
Fatty
lymph
§
Not
clear: milky, creamy
v
Differences between lymphatic &
blood vessels
Ø
Lymphatic
§
Thinner
walls
§
More
anastomoses
§
More
valves
v
Lymph Vessels
Ø
3
layers (same as b.v.)
v
Flow of Lymph
Ø
Capillaries
Ø
Vessels
(collecting)
§
Same
tunics as veins
§
Thinner
walls
§
More
valves & anastomoses
Ø
Trunks
§
Drain
large portions of body
§
More,
smaller
·
Paired
¨
Lumbar
¨
Bronchomediastinal
¨
Subclavian
¨
Jugular
·
Single
¨
Intestinal
Ø
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
Ø
Lower
pressure than b.v.
Ø
No
pump (ex. like heart)
§
Musc.
Pump
§
Respiratory
pump
§
Valves
– prevent backflow
§
Pulsation
of nearby arteries
§
Smooth
musc peristalsis (rhythmically)
·
Trunks
& ducts
Ø
Flow
is still sporadic & slow
v
Bad infection
Ø
Rest =
immobilization
§
Hinders
flow of inflammatory material throughout body
v
Lymphoid Cells (see Immune Handout)
Ø
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
Ø
Macrophages
& Dendritic Cells
§
Eat
foreign cells
§
Help
activate T cells
Ø
Reticular
cell
§
Produce
stroma (network made of fiber that supports other cell types in lymphoid
organs)
§
Provide
structure
v
Lymphoid Tissue
Ø
2
purposes
§
Where
lymphocytes live and reproduce
§
Surveillance
mechanism for lymphocytes & macrophages
Ø
Reticular
CT
§
Macrophages
– on fibers
§
Lymphocytes
– spaces of network
·
Travel
in circuit from lymph. tissues → blood → loose CT
Ø
Diffuse
lymphatic tissue
§
No
capsule
§
Scattered
§
Found in
all organs
§
Most
common in mucous membranes
Ø
Lymphoid
follicles (nodules)
§
No
capsule
§
Tightly
packed
§
Germinal
centers
·
Light
staining
·
Dendritic
& B cells
§
Found
forming lymph nodes, as Peyer’s patches in intestine & in appendix
Ø
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
Ø
Densely
packed follicles
Ø
Germinal
centers
§
B
cells
¨
Deep
part
Ø
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
Ø
All
made up of reticular CT
Ø
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
Ø
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
Ø
T cell
must recognize self b4 recognizing invaders
§
No B
cells
§
No
Reticular cells
Ø
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
Ø
Early
warning sign against infections (memory B cells)
v
Aggregates of Lymphoid Follicles
Ø
Peyer’s
patches
§
Clusters
of lymphoid follicles in sm. Intestine
§
Function
similar to tonsil
§
Crypt
Ø
Appendix
§
Blind
pouch that comes off beginning of lg. intestine
§
Contains
lots of bacteria
§
Lots
of lymphoid tissue
·
Lymphocytes
Ø
Functions
of Peyer’s patches & Appendix
§
Destroy
bacteria
§
Make
Memory B cell lymphocytes
·
Provide
long term immunity