Exam 4: Lymphatic System Flashcards
Tonsils
–Secondary lymphatic structures found in pharynx
–Not completely surrounded by capsule
–Help protect against foreign substances inhaled or ingested
–Have invaginated outer edges, tonsillar crypts
–Contain lymphatic nodules
What are tonsillar crypts?
Increase surface area to trap material
What do some lymphatic nodules contain?
Germinal Centers
What are the three types of tonsils?
Pharyngeal Tonsil
Palatine Tonsil
Lingual Tonsil
Pharyngeal Tonsil
- in posterior wall of nasopharynx
- when enlarged, termed adenoids
Palatine Tonsil
•in posterolateral oral cavity
Lingual Tonsil
•along posterior one-third of tongue
Phayngeal Tonsils
Palatine Tonsils
Lingual Tonsils
MALT
–Mucosa-associated lymphatic tissue
Where is MALT located?
–in gastrointestinal, respiratory, genital, and urinary tracts
•found in lamina propria of the mucosa
What does MALT do?
–Help defend against foreign substances
Where is MALT prominent?
–small intestines, especially ileum
•Peyer patches, found here
What is the general structure of the lymphatic system?
•Consists of red bone marrow, thymus, lymph, lymphatic vessels, lymph nodes, spleen, tonsils, MALT
What are the functions of the lymphatic system?
- Drain excess interstitial fluid
- Transport dietary lipids
- Carries out our immune responses
Flow of lymph: More fluid out of the blood capillaries than returns to them by
–More fluid filters out of blood capillaries than returns to them by reabsorption
How much excess fluid drains into lymphatic vessels and become lymph?
About 3L a day
What is an important function of the lymphatic vessesls?
to return lost plasma proteins to blood stream
What are the 2 pumps that aid in flow of lymph (also in venous return)
- Skeletal muscle pump – milking action
- Respiratory pump – pressure changes during breathing
Lymphatic vessels contain
valves
Lymph organs and tissues: 2 Groups based on function
Primary Lymphatic Organs
Secondary Lymphatic Organs
Primary Lymphatic Organs
- Sites where stem cells divide and become immunocompetent
- Red bone marrow and thymus
Scondary Lymphatic Organs
- Sites where most immune response occurs
- Lymph nodes, spleen, tonsils, MALT
Where is red bone marrow located
–Located within spaces between trabeculae in sections of spongy bone
- in flat bones of skull, vertebrae, ribs, and sternum
- proximal epiphyses of humerus and femur
What is red bone marrow responsible for?
–Responsible for hemopoiesis
•produces erythrocytes, platelets, granulocytes, and agranulocytes
T-lymphocytes and B-lymphocytes
- two major types of lymphocytes
- T-lymphocytes migrating to thymus to complete maturation
Thymus Anatomy: Outer Cortex
–composed of large number of T cells
- Immature T cells migrate here from red bone marrow where they proliferate and begin to mature
- Dendritic cells derived from monocytes assist in T cell maturation
- Specialized epithelial cells help educate T cells through positive selection – only about 25% survive
- Macrophages clear out dead and dying cells
Thymus Anatomy: Medulla
•More mature T cells migrate here from cortex
More epithelial cells, dendritic cells and macrophages
Thymus shrinks with age from g in infants to g in old age
70g to 3g
Secondary Lymphatic Organs: Lymph Nodes
–Located along lymphatic vessels
–Scattered throughout body
Lymph Node Anatomy
Stroma
Parenchyma
Lymph node anatomy: stroma
•supporting connective tissue
–Capsule (dense irregular connective tissue), trabeculae, reticular fibers and fibroblasts
Lymph node anatomy: parenchyma
•functional part
–Outer cortex – aggregates of B cells called lymphatic nodules (follicles) – site of plasma cell and memory B cell formation
–Inner cortex – mainly T cells and dendritic cells
–Medulla – B cells, antibody producing plasma cells from cortex, and macrophages
Lymph Flow through the lymph nodes
–Enters node through afferent lymphatic vessels
–Makes its way through lymph node sinuses
–Lymph continuously monitored for presence of foreign material
–Macrophages
•remove foreign debris from the lymph
–Lymph exiting lymph node through efferent vessel
–May enter nearby lymph node in cluster
Lymph Flow through lymph nodes: If lymphocyte contacts foreign substance
- immune response generated
- lymphocytes undergoing cell division
–especially in germinal centers
- some remaining in lymph node
- others transported in lymph and blood
–reach areas of infection
Lymph Flow Through Lymph Nodes: Swollen lymph nodes
- become tender with infection
- sign that lymphocytes proliferating and fighting infection
- can palpate swollen superficial lymph nodes
Secondary Lymphatic Organs: Spleen
–Largest single mass of lymphatic tissue in the body
–Stroma
–Parenchyma
Spleen Stroma
–capsule, trabeculae, reticular fibers, and fibroblasts
spleen: parenchyma
made of white pulp and red pulp
White Pulp
•– lymphatic tissue
–(lymphocytes and macrophages)
–B cells and T cells carry out immune function
–Contains a central artery
Red Pulp
contains erythrocytes, platelets, macrophages, and B-cells
Red Pulp: Macrophages
remove ruptured, worn out or defective blood cells
Red Pulp: Cells housed in reticular connective tissue…
Form Splenic Cords
Red Pulp: Splenic Sinusoids
–permeable capillaries, so blood cells easily exit
–drain to small venules leading to splenic vein
Red Pulp: In charge of production of blood cells during
fetal life
