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Anatomy of the lymphatic system (Lymph nodes: (Anatomy: Afferent lymph…
Anatomy of the lymphatic system
Lymphatic ducts:
Largest lymph vessels
Right lymphatic duct:
Location: near right clavicle
Receives lymph from the right side of the head & neck, right arm, & right side of the thoracic cavity
Receives lymph from smaller lymphatic vessels:
Right jugular
-drains lymph from head & neck
Right subclavian
-drains lymph from arms, breasts & superficial thoracic wall
Right bronchomediastinal
-drains lymph from structures within thoracic cavity
Lymphatic vessels:
Feed into the lymphatic ducts
Superficial lymph vessels are next to superficial veins & deep lymph vessels and next to deep arteries
Valves
- lymph vessels have low pressure so valves are needed to keep lymph from going backwards
Do not have a pump to move lymph thru the system & need:
Skeletal muscle contraction
Respiratory pump
Pulsating of nearby arteries
Contraction of larger lymph vessels
Lymphatic capillaries:
Begins the lymphatic network
Microscopic
Absorb interstitial fluid
Endothelial cells
overlap each other to allow entry of interstitial fluid but won't let lymph escape
Anchoring filaments
hold endothelial cells for support
Example of lymph capillaries:
Lacteals in the small intestine
Thoracic duct:
Location: from the diaphragm to the left clavicle, anterior to vertebrae
Receives lymph from the rest of the body, left head & neck, left thoracic cavity, all of the abdominopelvic region, & legs
Cisterna chyli:
Saclike structure inferior to the thoracic duct
Receives lipid-rich lymph from lacteals in the villi of the small intestine called
chyle
Contents of cisterna chyle are delivered to
thoracic duct
Chyle is delivered to the cisterna chyli via
lymphatic trunks:
R & L lumbar trunk
- drain lymph from legs, abdominopelvic wall, & pelvic organs
R & L intestinal trunk
- lymph from most abdominal structures
Receives lymph directly from lymphatic trunks:
Left jugular
- drains lymph from head & neck
Left subclavian
- drains lymph from arms, breasts & superficial thoracic wall
Left bronchomedistinal
- drains lymph from deep thoracic structures
Lymph nodes:
Location:
mostly in the axillary, cervical, and inguinal regions, however they are throughout the body, along the path of lymph vessels
Function:
macrophages get phagocytize unwanted material and house lymphocytes that undergo mitosis in the presence of an infection.
Anatomy:
Afferent lymph vessels: numerous, bring lymph into the node
Efferent lymph vessels: usually only one, lymph flows out of the node
Hilum: origin of the efferent lymph vessel
Trabeculae: dense reg connective tissue that encapsulates the node and separates the outer cortex & allows entry of blood vessels and nerves
Lymph nodes divided into:
Outer Cortex:
Made up of
lymphatic nodules
,
Lymphatic nodules made up of:
Germinal center
- houses maturing B-cells
Mantle zone
- surrounds germinal center and contains T-cells, macrophages & dendritic cells
Cortical sinuses
- open channels containing macrophages & contains high fluid pressure to force lymph through the lymph node
Inner Medulla:
Medullary cords
- connective tissue that supports B-cells, T-cells, & macrophages
Medullary sinuses
- open channels containing macrophages & contains high fluid pressure to force lymph through the lymph node
MALT:
Location:
Digestive, respiratory, urinary, and reproductive tracts
Function:
Defense in mucosa & protects from unwanted pathogens getting into the blood
Peyer's patches:
Within the small intestine, help prevent ingested microbes from crossing the GI tract into the blood
Spleen:
Location:
Left hypochondriac region, posterior to the stomach
Function:
Lymphocyte production
Phagocytosis of foreign material in the blood (red & white pulp) & old RBC's (red pulp)
Stores RBC's and platelets (red pulp)
Anatomy:
Encapsulated by connective tissue:
Trabeculae
: extend into and divide the spleen into
red & white pulp
Hilum
: where blood vessels & nerves enter & leave the spleen
Splenic artery
: carries blood to the spleen
Splenic vein
: carries blood from the spleen
Red pulp:
Contains erythrocytes, platelets, macrophages & B-cells
Splenic cords:
Reticular connective tissue that houses red pulp
Splenic sinusoid:
contains large gaps in endothelium to allow permeability of larger of formed elements & plasma proteins. Allows removal of damaged erythrocytes
White pulp:
Spherical clumps of T-cells, B-cells, and macrophages
Surround a central artery
Primary lymph structure 1: Thymus
Location:
Anterior superior mediastinum
Function:
T-cell maturation, grows until puberty & gradually gets smaller until it is replaced by adipose tissue around mid 20's
Anatomy:
Bilobed & fused together
Encapsulated by connective tissue
Trabeculae
separate lobes into lobules
-
Lobules contain: outer cortex & inner medulla
(contain T-cells at different levels of maturation)
Primary lymph structure 2: Red Bone Marrow
Location:
Trabeculae of spongy bone:
Mainly flat bones as adult, and epiphysis of humerus and femur
Function:
Hemopoiesis:
Production of formed elements, erythrocytes, leukocytes, and platelets
Immunity:
Innate immunity:
Nonspecific, react to a big range of unknown substances from pathogens to allergens
First line of defense:
Skin & mucosal membranes
Skin:
- Stratified squamous epithelium
protects from abrasion
Keratin:
makes a physical barrier on skin & is resistant to weak acids/bases, bacterial enzymes
Normal flora:
help prevent pathogenic overgrowth by competition for space
Skin pH:
3-5 inhibits growth
Sebum:
sebaceous gland secretion
Lysozyme & defensins:
sweat gland secretions
Mucosal membranes:
Mucus:
lysozyme, defensins, & IgA
Second line of defense: Internal
Neutrophils, macrophages, dendritic cells, basophils, eosinophils, mast cells, and NK cells
Phagocytes:
Neutrophils:
Most numerous
Macrophages:
Big eaters, last longer, participates in antigen presentation to T-cells
Dendritic cells
destroy pathogens and display the antigen on cell membrane to T-cells.
Eosinophils:
Immune response to allergens, eats antigen-antibody complex
Inflammation:
Basophils:
circulate the blood. Release
histamine & eicosanoids
to cause inflammation &
heparin
for anticoagulant
Mast cells:
similar but are fixed in the skin connective tissue, mucosa, & other organs
Natural Killer Cells:
Circulate the blood
Accumulate in the lymph nodes, tonsils, & spleen
Destroy array of pathogens: viral & bacterial infected cells, tumor cells, & transplant problems
Secrete perforin & granzyme to cause apoptosis
Interferons: released from infected cells to tell neighboring cells to cause antiviral changes to protect them from infection. Also stimulate NK cells to target infected cells
NK cells also release INF to stimulated macrophages to also destroy infected cells
Adaptive Immunity:
Acquired after exposure to antigen, specific, longer response time
Third line of defense:
T-cells & B-Cells
T-cells: cell response
Helper T-cells:
Coordinates humoral & cell-mediated immunity, also some innate immunity
Naive helper T-cells must activated by antigen presenting cells, then produces interleukin to stimulate more activated helper T-cells & memory T-cells
Activates B - cells
Cytotoxic T-cells:
activated by APC or infected cell, interleukin from helper T-cell fully activates cytotoxic T-Cell & cytotoxic memory cell
After days of proliferation:
Helper T-cells effector response:
go to the site of infection, activate B-cells & enhance response of cells innate immunity
Cytotoxic T-cells efectobre response:
goes to the site of infection, destroys infected cells by releasing perforin and granzymes to aid in apoptosis
B-cells: humoral response
Humoral immunity:
occurs in the blood & lymph
B-cells
react to antigens without a presenting cell
B-cell will engulf antigen and present it to helper T-cell
Helper T-cell releases interleukins & activates B-cells
Activated B-cells differentiate to:
Plasma
cells that produce
antibodies,
or:
Memory B-cells
that can be reactivated if exposed to that antigen
Antigens
Foreign antigens:
non self, causes immune response
i.e. pollen, bacteria, viruses, toxins
Self antigens:
won't bind with immune cells
Antibodies:
Antibodies
are an immunoglobulin protein that is made in response to an specific antigen.
Antibodies stick to specific antigens & stimulates destruction by other WBC's
Structure:
Y-Shaped protein
(2) Variable regions: antigen binding sites, specific
Constant region: stem, determines function of the antibody
Types of Immunoglobulins
:
IgG
The most common and most versatile
Used for passive immunity
IgM
Pentamer
Most effective at causing agglutination
Only antibody produced in a fetus
IgA
Dimer
Found in breast milk, saliva, tears, and mucus
Associated with mucus membranes
IgD
B-cell receptor
Identifies when immature B-cells are ready to be activated
IgE
Formed in response to allergic reactions
Causes release of histamine
Attracts eosinophils