Lymphatic System Flashcards
Functions of the Lymphatic System
- fluid recovery (2-4 L/day, prevents edema)
- immunity (lymph and blood monitored for pathogens and cancer cells)
- lipid absorption (via lacteals in small intestine)
6 Types of Lymphatic Cells
T Lymphocytes - develop in thymus
B Lymphocytes - develop in red bone marrow, produce antibodies
Macrophages - develop from monocytes, phagocytotic
Natural Killer Cells (NK cells) - large lymphocytes that attack and lyse bacteria, foreign tissue, infected host cells
Dendritic Cells - branched cells in skin, antigen presenters
Reticular Cells - branched cells in stroma of lymphatic organs
Lymphatic Fluid
- what is it?
- how is it produced?
AKA Lymph
- produced by filtration of plasma through capillaries
Pathway of Lymph Flow
- towards the heart
- begins in dead-ended lymphatic capillaries where blood capillaries are (except: brain, teeth, bones, marrow)
What is this structure?
Where is it found and where does it lead?
lymphatic capillaries
- smallest lymph vessel (larger than blood capillaries)
- permeable to lymph fluid and proteins via its valve-like overlapping endothelial cells
- dead-end at blood capillary beds and drain into lymph collecting vessels
- absent in cornea, bone marrow, CNS
What lymphatic structures do lymphatic capillaries drain into?
What is their structure like?
lymphatic collecting vessels
- contain valves to molve lymph towards heart
- have the same three tunics as blood vessels, but thinner walls and lower pressure
- have lymph nodes along length to filer lymph
- lie along with veins in superficial tissues and arteries in deeper tissues
The convergence of several lymphatic collecting vessels
lymphatic trunk
the five major lymphatic trunks
- Lumbar Trunk
- Intestinal Trunk
- Bronchomediastinal Trunk
- Subclavian Trunk
- Jugular Trunk
Paired lymphatic trunks branching off of the inferior end of the thoracic duct
Lumbar Trunks (left and right)
- carry lymph from lower limb, pelvic region and anterior abdominal wall
Single lymphatic trunk branching off of inferior thoracic duct
Intestinal Trunk
- drains lymph from stomach, intestines and other digestive organs
part C
bronchomediastinal trunks (left and right)
- carries lymph from thoracic viscera
- usually open into junction of internal jugular and subclavian veins
- sometimes join right lymphatic duct and thoracic duct
part B
subclavian trunks (left and right)
- lymph from upper limbs, inferior neck and superior thoracic wall
- open either into junction of internal jugular and subclavian veins or into jugular trunk and thoracic duct
part A
Jugular Trunks
- drains lymph from head and neck
- right side joins the venous angle (right internal jugular and subclavian veins)
- left side joins thoracic duct
Where do the lymphatic trunks drain?
- into the lymphatic ducts
- two major ducts: thoracic duct and right lymphatic duct
cisterna chyli
- dilated sac at inferior end of thoracic duct
- receives lymph from intestinal and lumbar trunks
- contains lots of chyle, fat-rich intestinal lacteal lymph
Thoracic Duct
- joins junction of left subclavian and internal jugular veins (the venous angle)
- drains left side of face, most of left thorax and lower body
top left question-marked structure:
right lymphatic duct
- joins right venous angle
- drains right side of head and upper body
- only present in 20% of people
what is this collection of blue structures?
cervical lymph nodes
what is this grouping of green and blue structures?
axillary lymph nodes
what is this grouping of green structures?
inguinal lymph nodes
Lymphoid Tissue
- what kind of tissue is it?
- what cells are found in it?
- where is it found?
- reticular connective tissue dominated by lymphocytes (T, B cells and macrophages)
- it is found primarily in two places:
- MALT (mucosa-associated lymphoid tissue) - mucous membranes of digestive, respiratory, urinary and reproductive tracts
- all lymphoid organs except thymus
lymphatic capillaries that absord dietary fats within the villi of the small intestine
lacteal
Lymphoid Nodules
- where are they found?
- how are they different from lymphoid organs?
- describe their structure
- name examples
AKA lymphoid follicles
- scattered clusters within lymphoid tissue
- they lack a fibrous capsule
- they are made of densely packed lymphocytes with a (usually lighter-staining) central zone of dividing cells (the germinal center)
Ex: tonsils and peyer’s patches
Tonsils
- what are they?
- where are they?
- what do they do?
- large lymphatic nodules
- located in the pharynx and on the palate and tongue
- they trap bacteria and foreign pathogens entering the mouth and nose
B
palatine tonsil
- paired tonsils at the posterior inferior margin of oral cavity
A
pharyngeal tonsils (AKA adenoids)
- located in posterior wall of nasopharynx
C
lingual tonsils
- located along posterior third of tongue
- unpaired
boxed structure:
- what is it?
- where is it?
- what does it do?
Peyer’s patch
- large isolated clusters of lymphatic nodules
- the ileal wall of the small intestine
- functions to destroy bacteria and generate memory lymphocytes for long term immunity
Lymphoid Organs
- what are they?
- how are they different from lymphoid nodules?
- how are they classified?
- give examples
- similar to lymphoid nodules in structure but are separated from tissues around them by a fibrous capsule
Primary Lymphoid Organs - produce lymphocytes
Secondary Lymphoid Organs - collect and destroy infectious organisms using lymphocytes
ex: Lymph Nodes, Spleen, Thymus
Lymph Nodes
- what are they?
- where are they?
- what do they do?
- what are large ones called?
- about 500 1-25 mm bean-shaped structures
- found along lymphatic collecting vessels
- macrophages within the node filter lymph of pathogens before it reaches the venous system
- large ones are called lymph glands
Lymph Node Structure Overview
- surrounded by fibrous capsule
- fibrous trabeculae extend inward and split the node into compartments
- divided into two regions: cortex and medulla
How does lymph flow through lymph nodes?
- it flows in through afferent lymphatic vessels, then…
- through lymph sinuses (subscapular, cortical and medullary), where macrophages cleanse it of pathogens, then…
- it exits through efferent lymphatic vessels at the hilum of the node back into collecting vessels
round structure marked 4
lymphatic nodule of lymph node
- clusters of lymphocytes in cortex of lymph node
3
cortex of lymph node
- outer region of lymph node
- consists of cortical sinuses and lymphatic nodules
4
medulla of cortex
- inner region of lymph node
- consists of medullary sinuses and medullary cords
3
germinal center
- areas in lymphatic nodules where b lymphocytes undergo mitotic division
1
medullary cords
- CT fibers that support strands of lymphatic cells
2
medullary sinus
- lymph percolates through these sinuses
the tiny dots that make up this image
lymphocytes
- white blood cells that attack specific types of antigens
what is the visible organ?
- describe its location
- what is its function?
- what are the two main types of tissue within it?
Spleen (largest lymphatic organ)
- located in upper left quadrant (left hypochondriac region)
- it stores blood and filters it to remove antigens and old blood cells
- also is site of hematopoiesis in fetus
- red pulp - engorged with RBCs
- white pulp - lymphocytes and macrophages collected like sleeves long central arteries
What is the organ at the superior end of the lungs, lying medial to them?
- what is its function?
- and why is it shown here on a child?
Thymus
- site of maturation of lymphocytes into “T” cells
- secretes thymosin and thymopoietin which stimulate immunocompetency of T cells
- it is most prominent in childhood when the immune system is developing, and is only 5% active by age 40
What is this structure?
What is it composed of and what is its function?
Thymic or Hassall’s Corpuscle
- found in medulla of thymus lobules
- clusters of epithelial cells
- functions to develop regulatory T cells which prevent auto-immune responses
What is this structure and what kind of tissue does it contain?
vermiform appendix
- blind-ended puch extending from cecum
- contains mucosa-associated lymphoid tissue (MALT) which protect against pathogens entering through cecal mucosa
