1. Chapter 21 Lecture Outline
See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes.

2. 21.1 Lymph and Lymph Vessels
Describe lymph and its contents.
Discuss the location and anatomic structure of lymphatic capillaries.
Explain how fluid enters lymphatic capillaries.
Explain the mechanisms that move lymph through lymphatic vessels, trunks, and ducts.
Name the five types of lymphatic trunks and the regions of the body from which they drain lymph.
Describe the regions that are drained by the right lymphatic duct and by the thoracic duct.
21.1 Lymph and Lymph Vessels
Learning Objectives:

3. 21.1 Lymph and Lymph Vessels
Lymphatic system functions
Transport and house lymphocytes and other immune cells
Return excess fluid in body tissues to blood to maintain blood volume
Lymphatic system components
Lymph vessels, lymphatic issues and organs
Lymph is the fluid transported within lymph vessels

4. Lymphatic System
Figure 21.1

5. 21.1a Lymph and Lymphatic Capillaries
Characteristics of lymph
Some fluid leaves blood capillaries and is not reabsorbed by them
Such fluid moves into lymphatic capillaries where it is called lymph
Components of lymph
Water, dissolved solutes, and small amount of protein
Sometimes cell debris, pathogens, or cancer cells

6. 21.1a Lymph and Lymphatic Capillaries
Small, closed-ended vessels that absorb interstitial fluid
Interspersed around most blood capillaries
Absent in avascular tissues, red marrow, spleen, and CNS
Slightly larger than blood capillaries; no basement membrane
Walls are made of overlapping endothelial cells
Have flaps between cells through which fluid enters but can’t exit
Anchoring filaments hold endothelial cells to nearby structures
Lacteals: lymphatic capillaries in GI tract
Absorb lipid-soluble substances from GI tract

7. Lymphatic Capillaries
Figure 21.2

8. 21.1a Lymph and Lymphatic Capillaries
Movement of lymph into lymphatic capillaries
Hydrostatic pressure of interstitial fluid pushes it into capillary
Anchoring filaments linking endothelial cells to surrounding structures prevent vessel collapse
Pressure of lymph inside vessel forces intercellular openings (“flaps”) of capillary wall to close with lymph inside
Lymph moves through vessels of larger and larger size
Lymphatic capillaries, lymphatic vessels, lymphatic trunks, and lymphatic ducts
Ultimately, fluid is returned to blood circulation

9. Clinical View: Metastasis
Wandering cancerous cells establishing secondary tumors
Develop in other locations in the body (metastasis)
E.g., breast cancer may metastasize to the lung
Cancerous cells break free from primary tumor
Transported in the lymph

10. 21.1b Lymphatic Vessels, Trunks, and Ducts
Lymphatic vessels are fed by lymphatic capillaries
Located adjacent to arteries and veins
Have all three vessel tunics (intima, media, externa)
Have valves to prevent pooling and backflow of lymph
Lymphatic system lacks a pump; moves lymph using
Skeletal muscles and respiratory pumps (as seen in veins)
Pulsatile movement of blood in nearby arteries
Rhythmic contraction of smooth muscle in larger lymph vessel walls
Some vessels connect to lymph nodes for lymph filtration

11. 21.1b Lymphatic Vessels, Trunks, and Ducts
Lymphatic trunks are fed by lymphatic vessels
Jugular trunks drain lymph from head and neck
Subclavian trunks drain upper limbs, breasts, and superficial thoracic wall
Bronchomediastinal trunks drain deep thoracic structures
Intestinal trunks drain most abdominal structures
Lumbar trunks drain lower limbs, abdominopelvic wall, and pelvic organs

12. 21.1b Lymphatic Vessels, Trunks, and Ducts
Lymphatic ducts are fed by lymphatic trunks
Largest lymphatic vessels
Bring lymph to venous blood circulation
There are two: right lymphatic duct and thoracic duct
Right lymphatic duct is near right clavicle
Drains upper right quadrant of body
Right side of head and neck, right upper limb, and right side of thorax
Delivers lymph to junction of right subclavian and right internal jugular veins

13. 21.1b Lymphatic Vessels, Trunks, and Ducts
Lymphatic ducts (continued)
Thoracic duct is largest lymphatic vessel
Runs from diaphragm to junction of left subclavian and left jugular veins
Saclike cisterna chyli at its base
Receives lipid-rich chyle from GI tract
Drains lymph from left side of head and neck, left upper limb, left side of thorax, abdomen, and both lower limbs
Figure 21.3b

14. Lymphatic Trunks and Ducts
Figure 21.3a

15. Clinical View: Lymphedema
Accumulation of interstitial fluid due to interference with lymphatic drainage
Causes swelling and pain in affected area
May interfere with wound healing and contribute to infection
Most caused by blockage of lymph vessels
E.g., trauma or infection of lymph vessels or tumors
E.g., radiation therapy scarring or surgical removal of lymph nodes
Controlled with compression garments, exercise, massage
Extreme cases known as elephantiasis
Caused by infection with parasitic worms

16. What did you learn?
How does fluid enter lymphatic capillaries, and what prevents its escape from them?
What is the order of flow through different lymphatic vessels?
Which lymphatic duct receives lymph from the right leg?

17. 21.2 Overview of Lymphatic Tissue and Organs
Name the two categories of lymphatic tissue and organs, and identify components of the body that belong to each category.
Learning Objective:

18. 21.2 Overview of Lymphatic Tissue and Organs
Primary lymphatic structures
Involved in formation and maturation of lymphocytes
Red bone marrow and thymus
Secondary lymphatic structures
Do not form lymphocytes, but house them and other immune cells
Sites of immune response initiation
Include lymph nodes, spleen, tonsils, and lymphatic nodules
Include MALT (mucosa-associated lymphatic tissue)

19. What did you learn? What does the acronym MALT stand for?
What is an example of a primary lymphatic structure?

20. 21.3 Overview of Lymphatic Tissue and Organs
Describe the location and general function of red bone marrow.
Identify the two major types of lymphocytes.
Describe the structure and general function of the thymus.
Learning Objectives:

21. 21.3a Red Bone Marrow Red bone marrow
Located between trabeculae of spongy bone
In flat bones of skull, ribs, and sternum, vertebrae, ossa coxae, heads of humerus and femur
Site of hemopoiesis: production of blood’s formed elements
Formed elements include T-lymphocytes and B-lymphocytes
T-lymphocytes migrate to thymus to complete maturation
Figure 21.4

22. 21.3b Thymus Thymus involved in T-lymphocyte maturation
Located in mediastinum
Larger in children than adults
Grows until puberty, then regresses; gradually replaced by adipose tissue
Consists of two thymic lobes, each surrounded by connective tissue capsule
Trabeculae of capsules subdivide lobes into lobules
Each lobule has outer cortex and inner medulla regions
Both regions are lymphoepithelial (contain lymphatic cells and epithelial tissue)
Cortex contains immature T-lymphocytes
Medulla contains mature T-lymphocytes

23. Thymus
Figure 21.5a

24. Thymus
Figure 21.5b-c

25. What did you learn? Where does hemopoiesis occur?
What is the function of the thymus?

26. 21.4 Secondary Lymphatic Structures
Describe the structure of lymph nodes.
Explain the function of lymph nodes.
Describe the spleen and its location.
Distinguish between white pulp and red pulp.
List the functions of the spleen.
Identify the main groups of tonsils and their location and function.
Describe the composition of individual lymphatic nodules.
Compare the locations of MALT and Peyer patches.
Learning Objectives:

27. 21.4 Secondary Lymphatic Structures
House lymphocytes and other immune cells within a reticular connective tissue matrix
Organized into lymphatic organs and aggregates of lymphatic nodules
Organs have a complete capsule of dense irregular connective tissue
Spleen and lymph nodes
Other lymphatic structures have an incomplete capsule or lack one
Tonsils, MALT, diffuse lymphatic nodules

28. 21.4a Lymph Nodes Lymph nodes filter lymph, remove unwanted substances
Small, oval, encapsulated structures
Located along deep and superficial pathways of lymph vessels
Occur in clusters receiving lymph from body regions
Cervical lymph nodes receive lymph from head, neck
Axillary lymph nodes receive lymph from breast, axilla, and upper limb
Inguinal lymph nodes in groin receive lymph from lower limb and pelvis

29. 21.4a Lymph Nodes Lymph node components
Afferent lymphatic vessels bring lymph to node
An efferent vessel drains a lymph node
Located at hilum (involuted portion of node)
Dense connective tissue capsule encloses node
Trabeculae of capsule subdivide node into compartments
Outer cortex, inner medulla
Figure 21.6a

30. 21.4a Lymph Nodes Node’s cortex contains lymphatic nodules
Reticular fibers support a germinal center
Houses proliferating B-lymphocytes and some macrophages
Surrounding mantle zone contains T-lymphocytes, macrophages, and dendritic cells
Cortical sinuses are tiny open channels lined by macrophages
Figure 21.6b (part)

31. 21.4a Lymph Nodes Node’s medulla contains medullary cords
Connective tissue fibers that support B-lymphocytes, T-lymphocytes, and macrophages
Medullary sinuses are tiny open channels lined with macrophages
Figure 21.6b (part) 21.6c

32. 21.4a Lymph Nodes Lymph flow through nodes
Lymph enters through several afferent vessels
Creates pressure to push it through node to the single exit vessel
Lymph is monitored for presence of foreign material
Macrophages remove foreign debris from lymph
Lymphocytes may initiate immune response
Lymphocytes proliferate especially in germinal centers
Can cause enlarged nodes that can be palpated in neck and axilla
Lymph exits node through efferent vessel
May enter nearby lymph node within the cluster of nodes

33. Clinical View: Lymphoma
Malignant neoplasm from lymphatic structures
Nontender, enlarged lymph node
Possible night sweats, fever, and weight loss
Hodgkin lymphoma
Affects young adults and people over 60
If caught early, cured by excision, radiation, and chemotherapy
Non-Hodgkin lymphoma
More common
Some kinds aggressive, others slow growing

34. 21.4b Spleen The spleen is the largest lymphatic organ
Located in left upper abdominal quadrant
Lateral to left kidney and posterolateral to stomach
Posterolateral aspect is convex and rounded
Anteromedial border is concave
Hilum: indentation where blood vessels and nerves enter
Splenic artery supplies blood; splenic vein drains it
Surrounded by connective tissue capsule
Trabeculae from capsule extend into spleen dividing red and white pulp

35. 21.4b Spleen Tissues of the spleen White pulp Red pulp
Clusters of T- and B-lymphocytes and macrophages around central artery
Red pulp
Contains erythrocytes, platelets, macrophages, and B-lymphocytes
Splenic cords: cells and reticular connective tissue in red pulp
Splenic sinusoids: very permeable capillaries
Storage site for erythrocytes and platelets

36. Spleen
Figure 21.7
Figure 21.7

37. 21.4b Spleen Monitoring blood as it flows through the spleen
The spleen filters and monitors blood (not lymph)
White pulp monitors it for foreign materials and bacteria
Macrophages in sinusoids of red pulp remove particles
Phagocytize bacteria, debris, defective erythrocytes and platelets
Path of flow: splenic artery, central artery, sinusoids, venules, splenic vein
Summary of functions: eat foreign particles, clear defective erythrocytes and platelets, store erythrocytes and platelets
In first 5 months of fetal life, spleen makes blood cells
This function can be reactivated under certain conditions
E.g., some hematologic disorders

38. Clinical View: Splenectomy
Surgical removal of the spleen
May be performed due to
Ruptured spleen from abdominal injury (most common)
Infection, cyst, or tumor
Lymphoma or other cancer
Blood disorders (e.g., sickle cell anemia)
May be more prone to life-threatening infection

39. 21.4c Tonsils Tonsils Secondary lymphatic structures
Immune surveillance of inhaled and ingested substances
Tonsillar crypts
Invaginations that trap material
Contain lymphatic nodules
Some with germinal centers
Figure 21.8b, c

40. 21.4c Tonsils Tonsils (continued) Pharyngeal tonsil Palatine tonsils
In nasopharynx
Called adenoids when enlarged
Palatine tonsils
In posterolateral oral cavity
Lingual tonsils
Along posterior one-third of tongue
Figure 21.8a

41. Clinical View: Tonsillitis and Tonsillectomy
Acute tonsillitis: inflammation and infection of tonsils
Palatine tonsils most commonly affected
Redden and enlarge
May partially obstruct pharynx
Fever, chills, sore throat, and difficulty swallowing
May be infected by viruses or bacteria
Persistent recurrent infections, chronic tonsillitis
May require tonsillectomy, surgical removal of tonsils

42. 21.4d Lymphatic Nodules and MALT
Clusters of lymphatic cells with some extracellular matrix
Not completely surrounded by connective tissue capsule
Scattered nodules termed diffuse lymphatic tissue
Found in every body organ
Help defend against infection
In some areas, group together to form larger structures
E.g., MALT

43. 21.4d Lymphatic Nodules and MALT
Mucosa-associated lymphatic tissue
Located in gastrointestinal, respiratory, genital, and urinary tracts
Found in lamina propria of the mucosa
Help defend against foreign substances
Prominent in small intestines, especially ileum
Peyer patches: large collections of lymphatic nodules that form bulges in ileum wall

44. Relationship of the Lymphatic System to the Cardiovascular System
Figure 21.9a

45. Relationship of the Lymphatic System to the Immune System
Figure 21.9b

46. What did you learn?
What is the typical ratio of afferent and efferent vessels at a lymph node?
Which side of the body is the spleen on? Which direction does its hilum face?
What functions does the red pulp of the spleen serve?
What are Peyer patches?