Anatomy and pattern recognition of the lymphatic system Flashcards
What is the immune system?
It is the bodies first line of defence
Immunity and themlymphatic system
Microorganisms (viruses, bacteria, fungi and
parasites) are known as pathogens.
Each pathogen interacts with the body in a
characteristic way
• viruses exist within cells which they
eventually destroy
• Bacteria multiply in the interstitial fluids
• Parasites burrow through internal organs
The lymphatic system includes cells, tissues and
organs.
• The primary cells are lymphocytes.
types of immunity
immunity:
inate (at birth) = specific (against specific pathogen) and non specific
acquired = passive split into natural (from mother placental tcirculation to fetus) and artificial (administration of antitoxins)
active split into natural (infection recovery an actual disease) and artificial (immunisation and vaccination)
Blood cells
The 3 main types of blood cell are:
o red cells (erythrocytes)
o Platelets (thrombocytes)
o White cells (Leukocytes)
Leukocytes (White blood cells)
Our white blood cells are associated with defence and immunity
• They detect and destroy foreign / abnormal material through a range of processes
• They are the largest type of blood cells but only make up 1% of blood volume
There are 2 main types
o Granulocytes
o Agranulocytes
Granulocytes
• Neutrophils
o Respond to bacteria, dead cells and tissue
o Responds to the release of chemicals by damaged cells (Chemotaxins)
o Use phagocytosis
• Basophils
o Respond to allergens (e.g. pollen)
o Contain histamine (inflammatory) and heparin 9anticoagulant)
• Eosinophils
o Responds to parasites that are too big to be phagocytosed
o They release toxic chemicals that can also cause a local inflammation (e.g. skin reaction)
o They also have an effect to reduce an allergic response by releasing enzymes to break
down histamines
The monocyte – macrophage system
• Monocyte
o Largest white blood cell
o They can be in the blood or in lymphoid tissues where they develop into
macrophages
o Both produce interleukin 1 which
§ Increases body temperature through the hypothalamus
• Macrophages
o They are large
o They phagocytose more than neutrophils
o They produce chemical for inflammation and tissue repair
Phagocytosis
• Translates as cell eating
• This is the first line of defence for the
immune system
• The white blood cells are attracted to sites of
inflammation and infection by chemotaxis
• They engulf and destroy
• Microbes (e.g. bacteria)
• Foreign cells (e.g. tumour cells)
• Antigenic material (cause the production
of antibodies)
• Damaged cells and debris
• They can also release chemicals into the
lymph which are toxic to microbes
Lymphocytes
• Smaller than monocytes, and make up
approximately 30% of white blood cells
• They are found in the blood, but most
are in the lymphoid tissue
• They all originate from the same type of
stem cell in red bone marrow / lymphoid
tissue but they can develop into either
o Non specific
o Specific
B-lymphocytes
T-lymphocytes
B-Lymphocytes
o Produced and matured in red bone marrow, stored in lymphoid tissue
o They produce antigens (immunoglobins) - proteins that atta h to and destroy antigens
o They only respond to one type of antigen
o Provide antibody mediated immunity
T-Lymphocytes
o Mature in the thymus which programmes them to only respond to one antigen
o Found more in circulation
o They rely on other cells to present the antigen to be destroyed
o Cell mediated immunity
Interstitial fluid and lymph - overview
Interstitial fluid between the cells diffuses from the bloodstream
through the permeable capillary walls
• Most of this fluid diffuses back into the bloodstream through the
venous capillaries
• The remaining fluid diffuses through the lymph capillaries – and is called
lymph
• It passes through the lymphatic system and the lymph nodes before
diffusing back into the blood
Functions of the lymphatic system
Immunity
• Production and maturation of white blood cells
• 90% of the body’s immune cells are within the lymphatic tissue
• All organs / tissue is supported by a network of lymph vessels and nodes
Tissue drainage (homeostasis)
• 21 litres of interstitial fluid diffuses from your bloodstream each day
• Most returns directly to the blood
• Excess fluid (3-4 litres) drains through the lymphatic system
Absorption of fat / fat soluble nutrients / fatty acids
• Absorbs into the central lymphatic vessels in the villi of the small bowel
lymph transportation
o Carries larger particles (bacteria and cell debris) to be filtered and destroyed in the lymph nodes
o It circulates lymphocytes throughout the lymphatic system
Lymph capillaries
They are designed to let fluid flow only one way
• Have a one way valve and are closed at the
proximal end
Lymphatic vessels
• Formed by a network of lymphatic capillaries
• Movement of lymph is similar to venous flow
and return via
• Rhythmic contraction of muscle layers
causes lymph movement
• Contraction of adjacent muscles
Lymphatic ducts
The lymphatic vessels drain into 2 large ducts
• Both drain back into the venous system through the respective subclavian veins
thoracic duct
• Begins in a vessel anterior to L1/2
• 40cm long and drains into left subclavian vein
• Drains the legs, pelvis, abdomen, left arm, left
side of thorax, head and neck
right lymphatic duct
Very short tin comparison – only 1cm
• Lies in the right side of the neck and drains into
the right subclavian
• Drains the right arm and right side of head, neck and thorax
Lymph nodes
• Small oval shaped organs that are found along the lymph vessels, usually in groups
• Lymph normally passes through a number (8-10) nodes before re- entering the circulation
• They vary in size from 1mm to 20mm
• Their functions are
• Filtration and phagocytosis
• Multiplication of lymphocytes which, when activated release antibodies
Lymph node locations
• Found along the length of the lymphatic
system but are also grouped in specific
locations- the junctions between regions
• There are deep and superficial groups
• Includes
• Cervical – head and neck
• Axillary – arms and breast
• Mediastinal – thoracic
• Knee and inguinal – lower limbs
• Pelvis and abdomen - mainly close to major vessels
Filtration and phagocytosis
• Lymph is filtered by reticular and lymphatic tissue to remove
• Bacteria
• Dead / live phagocytes with ingested microbes
• Damaged cellular tissue
• Tumour cells
• Inhaled particles
• Macrophages and antibodies destroy organic matter
• Non-organic matter is trapped by macrophages (too large to leave by the vessels)
• Successive lymph noes act to provide a filtering mechanism
• Incomplete phagocytosis causes inflammation and hypertrophy – lymphadenopathy
Spleen
• Largest lymphatic organ
• Has a hilum containing
• Splenic artery
• Splenic vein
• Nerves and lymph vessels
Structure of the spleen
• Cellular structure of the spleen contains
lymphocytes and macrophages
• Blood in the spleen follows the same pattern
as lymph nodes – through the sinuses /
trabeculae
• Pores in the endothelium allow close contact
between blood and the splenic pulp
• It has no afferent lymph vessels so is not
affected by diseases spread in the lymphatic
system
Functions of the spleen
phagocytosis
blood storage
immune response
Erythropoiesis
Thymus
Lies in the superior mediastinum posterior to the sternum and between the lungs
• Consists of a left and right lobe connected by connective tissue
• Surrounded by a fibrous capsule, which like lymph nodes and spleen extends into the body to form lobules
• Made up of epithelial cells and lymphocytes
Functions of the thymus
• Contains activated –lymphocytes
• The hormone thymosin is secretes in the thymus it matures the T-lymphocytes and sensitises them to a specific antigen
• They travel through the body and will only respond that their specific antigen – cell mediated immunity
• Production is most prolific up to adulthood but continues to a smaller extend throughout life
• It provides a less effective response as we get older
