CH 23: The Lymphatic System

1
CH 23 The Lymphatic System
Hastaneciyiz.blogspot.com
Accessory to cardiovascular system ? there are
two drainage systems

• Goals
• Discuss the organization of the lymphatic system,
  including the vessels, principal lymph nodes,
  thymus, and spleen
• Explain the relationship between the lymphatic
  and circulatory systems, and the role of
  lymphoid tissue structures and lymphocytes in the
  bodys defense

2
Overview of the Lymphatic System

• Includes, vessels, fluid, and nodes or
  nonsecreting "glands".
• Lymphatic vessels convey fluid from the periphery
  to the veins.
• The fluid, lymph (clear spring water), is what
  seeps out of the blood at the peripheral
  capillaries. Composition is similar to plasma
  without the proteins
• Lymphatic organs or tissues ("glands") are
  filtering areas and arenas of lymphocyte
  maturation and competency.

3
Major Functions of Lymphatic System

• Filtration of lymph
• Return of seeped fluid to c.v. system
• Education and production of immune system
  lymphocytes
• Transport of digested lipids from small
  intestinal lacteals

4
Lymph Capillaries
Compare to Fig. 23.2

• Thin walled endothelium (no BM) with periodic one
  way valves. In general they parallel veins.
• Closed ends allow fluid flow inward only
• Pick up and recycle extra tissue fluid

Lymph circulation due to ?
5
Location of Lymph Capillaries

• Everywhere, except for CNS and bone marrow, as
  well as cornea and cartilage.
• Special set of lymph capillaries in villi of
  small intestine Lacteals

6
Lymphatic vessels

• comparable in structure to veins

Damaged valves or blocked lymph vessels
???
7
Right lymphatic duct
Right subclavian vein
Left subclavian vein
Thoracic (left lymphatic) duct
Lymph capillaries converge to become collecting
vessels and end up as either Thoracic duct or
right lymphatic duct
Cysterna Chyli
Fig 23.4
8
largest
9
Lymphocytes

• Agranulocytes - large nuclei and small amount of
  cytoplasm
• Function in identification and inactivation/destru
  ction of pathogens
• Types of Lymphocytes
• T Cells - cellular immunity - specific for
  previously identified pathogens
• T Helper, T Killer, T Suppressor, and memory
  cells
• B Cells - humoral immunity - plasma cells produce
  antibodies specific to the antigen or pathogen
  memory cells
• NK cells - non-specific, provide immunological
  surveillance

10
Bone Marrow Lymphopoiesis
Fig 23.7
Lymphocytes are later also produced in thymus,
spleen and tonsils
11
Lymphoid Tissue
1
adenoids

• C.t. loaded with Lymphocytes
• Lymphoid nodules are unencapsulated clusters of
  lymphocytes (? 1mm). Found beneath epithelial
  lining of respiratory, digestive urinary tracts
• Mucosa associated lymphatic tissue (MALT) in GI
  tract
• 5 tonsils
• aggregate lymphoid nodules in small intestine (
  Peyers patches)
• appendix - walls contain lymphoid tissue

2
2
12
Lymph Nodes

• 500 (? 1mm to 25 mm)
• Bean-shaped with hilus
• several afferent vessels, one efferent vessel
• Function?
• Popular term lymph gland is misnomer. Why?
• Contain lots of lymphocytes Macrophages
• Clinical application Swollen lymph nodes

Fig 23.9
13
Distribution of LNs

• Cervical lymph nodes - drain head and neck
• Axillary lymph nodes - drain arms and breasts
• Popliteal lymph nodes - drain legs, drain into
• Inguinal lymph nodes - drain lower limb
• Thoracic lymph nodes - drain thoracic viscera
• Abdominal lymph nodes - drain pelvic region
• Intestinal and mesenteric lymph nodes - drain
  abdominal viscera

14
Thymus

• Location above heart, posterior to sternum
• Divided into lobules
• Only lymphoid organ that does NOT fight antigens,
  it functions as T-cell academy
• Blood thymus barrier prevents premature
  stimulation of developing T-cells
• Involution after puberty
• Epithelial cells produce thymic hormones

15
Spleen
Surfaces named for contacts diaphragmatic,
visceral, gastric, renal

• Largest lymphoid organ
• Soft and very blood rich
• Red pulp sinusoids containing RBCs
• white pulp lymphoid tissue
• Major Functions
• Initiation of Immune response to antigens in
  blood
• Removal of aged and defective RBCs
• Repository for new RBCs
• Fe salvaging, storage and recycling

Fig 23-17
the end