chapter 20 the lymphatic system g.r. pitts, j.r. schiller, and james f. thompson, ph.d. use the...
TRANSCRIPT
Chapter 20
The Lymphatic System
G.R. Pitts, J.R. Schiller, and James F. Thompson, Ph.D.
Use the video clip: CH 20 - Lymph Node Anatomy for a review of lymph node structure
The Lymphatic System• Basic organization
– Lymph fluid in lymph vessels– Structures: organs with lymphatic tissue, red
bone marrow, liver and spleen
• Functions– return interstitial fluid and proteins to the
blood– transport dietary fats to adipose tissue – protect against cancer & infection
• resistance - fight off disease– nonspecific resistance - general protection against
disease– immunity - specific protection
• susceptibility - lack of resistance
Lymph Flow• More fluid moves out of the blood
capillaries by filtration than returns by reabsorption - Starling’s Law
• ≈ 3Ll day of lymph is generated
• Proteins escaped from the blood or secreted by tissues are transferred back to the blood by the lymphatics
• Lymph flow is facilitated by muscle pumps, the respiratory pump, valves, and smooth muscle (in the walls of the trunks & thoracic duct)
• Smaller vessels drain into larger vessels
Lymphatic Capillaries• “Blind ended,” covered vessels between cells, larger
than capillaries• Not found in avascular tissues (CNS, cartilage) nor in
the splenic pulp, and bone marrow
Lymphatic Capillaries• Structure/Function regulates fluid flow
– Anchoring filaments - from lymphatic endothelium attach to surrounding tissues
– Endothelial cells overlap• high hydrostatic fluid pressure separates cells, fluid into caps• hydrostatic fluid pressure in cap prevents fluid movement out
minivalve
Lymph Flow Follows Venous
Circulation
• Lymph vessels have the same organization and routing as the vascular tree
Lymphatic Flow (cont.)
• Lymphatic vessels have no separate pump (heart)
• All lymph returns to the vena cava and to the right side of the heart
Lymphatic Flow (cont.)• Lymph ducts
– Right lymphatic duct • about ½ inch long • drains lymph from
upper right side of body (arm & head)
– Thoracic (left) duct • main collecting duct
of the lymphatic system
• 38-45 cm long• drains 75% of body• begins as a dilation
known as the cisterna chyli located anterior to lumbar disk #2
Lymphatic Flow (cont.)
• Lymph returns to the venous drainage through right and left lymphatic ducts at the junction of the internal jugular and subclavian veins
Summary of Lymphatic Vessels
• Lymph Flow from smallest to largest:
• Capillaries vessels trunks ducts
• Lymph vessels anastomose and supply and drain lymph nodes along their course
Two Main Types Of Lymphocytes
• B lymphocytes = B cells– attack microbes, especially bacteria– develop into plasma cells to produce antibodies (Ab)
• bind to antigen to form antibody-antigen (Ag-Ab) complexes• complexes prevents Ag from interacting with other body cells
or molecules• memory B cells – dormant until future exposure to Ag
• T lymphocytes = T cells– regulate many immune responses– attack viruses, fungi, transplants, cancer, some
bacteria• 4 types of T cells
– cytotoxic (killer) T cells - destroy foreign invaders – helper T cells - assist B cells and cytotoxic T cells– suppressor T cells – help bring immune response to an
end– memory T cells - dormant until future exposure to Ag
Lymphocyte Development• primary lymphatic organs - site of
lymphocyte (B cell and T cell) production– bone marrow - produces B cells,
immature T cells– T cells migrate to the thymus gland to
mature or die if determined to be improper
• secondary lymphatic organs – sites of activated immune responses– lymphatic nodules (lymph follicles) – lymph nodes, spleen, tonsils
Other Lymphoid Tissue Cells
•Macrophages & Dendritic cells–Phagocytize foreign substances and cells–Transport them to lymphatic tissues–Process foreign things into individual antigens
–Present Ags to T & B lymphocyte to help activate them
•Reticular cells–Similar to fibroblasts–Produce reticular fibers (stroma) that provide the framing structure for other cells in lymphoid organs
Lymphatic Tissue - General• Stroma of reticular
connective tissue (except thymus)
• Parenchyma of macrophages, B and T lymphocytes, occasional other leukocytes
• May or may not have a connective tissue capsule
Lymphatic Organs – Thymus Gland
• Thymus Gland – Two lobes between the
sternum and the heart– Thymocytes produce hormones– Atrophies with age (starting ~20)
• Structure/Function– Outer cortex – immature T cells
• screened for functional capacity• stimulated to proliferation • stimulated to maturation
– Inner medulla• defective T cells degenerate • mature T cells move into blood
Lymphatic Organs – Lymph Nodes
•Anatomy– oval, bean shaped small
structures scattered throughout body along lymph vessels
– may be deep or superficial
– concentrated along the respiratory tree and GI tract, in the mammary glands, axillae, and groin
– filter lymph fluid to trap foreign organisms, cell debris, and tumor cells
Circulation in the Lymph Nodes• Lymph enters via a number of
afferent lymphatic vessels• It then enters a large
subcapsular sinus and travels into a number of smaller sinuses
• It meanders through these sinuses and exits the node at the hilus via efferent vessels
• The node acts as a “settling tank,” because there are fewer efferent vessels, lymph stagnates somewhat in the node
• This allows lymphocytes and macrophages time to carry out their protective functions
Only lymph nodes filter lymph!
Cancer Metastasizes To Lymph Nodes
Cancer cells from the tumor are first trapped in a lymph node
Lymphatic Organs - Spleen• largest lymphoid organ
in the body• fibrous capsule with
arteries, veins, and efferent lymph vessels
• located between stomach and diaphragm
Spleen Functions: White Pulp
• a site of immune surveillance and response• macrophages phagocytize bacteria, worn-out RBC's,
platelets• hemoglobin is recycled and components transferred to
liver• macrophage antigen-presentation and lymphocyte
activation and proliferation• some B cells mature into plasma cells
Spleen Functions: Red Pulp• Site of fetal erythrocyte
production (normally ceases after birth)
• Stores ~ 1 L of blood which can be released during an emergency (hemorrhage)
Unencapsulated Lymphatic Tissue
• Diffuse lymphatic tissue– Small scattered patchs– In nearly every organ
• Lymphoid follicles (nodules)– More organized, more
cellular clusterssmallbronchus
Mucosa-Associated Lymphatic Tissue (MALT)
found in the lamina propria of mucous membranes of the GI tract, respiratory tract, urinary tract, and reproductive
tract
Peyer’s patchesin the intestines
Lymphatic Organs - Tonsils• lymphoid tissue
beneath the mucosae
• tonsilar crypts trap micro-organisms
• immune cells destroy the micro-organisms
• palantine tonsils – largest and most frequently infected
Lymphadenopathy
Enlarged lymph nodes due to increased drainage from inflammatory lesions or infections.
Associated with malignant and nonmalignant diseases.
Lymphocyte leukemia with severe lymphadenopathy
Hodgkin’s Disease:one of thesignificant malignant lymphomas
Cervicallymph nodes
Burkitt’s Lymphoma
Commonly found in central Africa and New Guinea.
Associated with Epstein-Barr virus which causes infectious mononucleiosis in North America and Europe.
Rarer American type has extensive marrow replacement.
Cancerous cell is a B lymphocyte.
End Chapter 20
G.R. No. 191002, G.R. No. 191032, G.R. No. 191057, A.M. No. 10-2-5-SC, G.R. No. 191149, G.R. No. 191
Chapter 4 Tissue: The Living Fabric G.R. Pitts, Ph.D, J.R. Schiller, Ph.D. & James F. Thompson, Ph.D