The document outlines the key components and functions of the lymphatic and immune systems. It begins by defining the lymphatic system and explaining its role in absorbing excess fluid, transporting fats, producing lymphocytes, and defending the body. It then describes the structure of the lymphatic system including lymphatic vessels, lymph nodes, and other organs. Key differences between the lymphatic and immune systems are highlighted such as their circulatory nature and roles in long-term immunity. Finally, common diseases of the lymphatic system like lymphedema are discussed.

1. Lymphatic
Immune
system
Biology case (3)
G5 PBL

2. Objectives:
● Define the lymphatic system, explain it function and identify it
components. (General).
● Describe the structure of the lymphatic system.
● Describe each component of the lymphatic system ( definition,
physiology, histology).
● Describe the mechanism of circulation.
● Describe how the lymphatic system works with others systems.
● Compare between lymphatic and cardiovascular system.
● Diseases of lymphatic system (edema).
● Define the Immune system, explain it function and identify it
components.
● Explain the types of Immune system.
● Describe the difference between lymphatic and Immune system.

3. lymphatic system
Do you know what the lymphatic system is ?
it is network of tissues and organs that help rid the
body of toxins, waste and other unwanted materials.
What does the lymphatic system consist of ?
lymphatic vessels, lymph nodes, the spleen, and other
lymphatic organs.

4. The Main functions of the lymphatic system :
The lymphatic system has four main functions that contribute to homeostasis:
(1) Lymphatic capillaries absorb excess tissue fluid and return it to the bloodstream
(2) in the small intestines, lymphatic capillaries called lacteals absorb fats in the form of
lipoproteins and transport them to the bloodstream
(3) the lymphatic system is responsible for the production, mainte- nance, and distribution
of lymphocytes
(4) the lymphatic system helps defend the body against pathogens

5. STRUCTURE OF LYMPHATIC SYSTEM
The lymphatic system consists of lymphatic vessels and lymphatic organs
THE LYMPHATIC VESSELS
LYMPH excessive tissue fluid carried by lymphatic vessels
Collects lymph from lymph capillaries
Delivers lymph to lymph nodes
Returns fluid to circulatory veins near the heart

6. Fluid & plasma proteins are not all resorbed at the capillary beds and must be
returned to the blood to maintain blood volume …lymphatic vessels accomplish
this
One-way system, lymph flows toward the heart
Lymph vessels include:
Microscopic, permeable, blind-ended capillaries
Lymphatic collecting vessels
Trunks and ducts

7. The lymphatic organs
1. Primary lymphoid organs: Where lymphocytes are generated
a. Bone marrow
B lymphocytes are mature in bone marrow
Produce plasma cells, which secrete antibodies
Antibodies immobilize antigens and “tag” them for destruction by
leukocytes (WBCs)

8. b. Thymus gland
T lymphocytes are mature in thymus
Manage the immune response
Attack and destroy foreign cells
2. Secondary lymphoid organs : initiate adaptive immune responses
Lymph node
Spleen
Appendix
Peyer’s patches
Tonsils

9. Lymphoid organ: Lymph nodes.
It is a small, bean-shaped organ that serves as a filtering and processing center for your
immune system.
*Approximately 600 lymph nodes are scattered throughout the human body. They can
exist singly or in closely connected groups called chains.
*Lymph nodes are connected to their neighbors by a sort of network of tubes called
lymphatic vessels.
*lymph: it’s a clear fluid contains more white blood cells than plasma.

10. Lymph nodes

11. *Lymphocytes: *Macrophages:
1- They detect if there is any viruses or bacteria 1 - They will directly phagocytes the viruses
in the lymphatic fluid. and bacteria.
2 - They produce antibodies to combat viruses
and bacteria.

12. Types of lymphocytes:
1 - T cells: a type of white blood cell and they help protect the body from infection and
may help fight cancer.
Location : in cortex.
2 - B cells: A type of white blood cell that makes antibodies.
Location: in germinal center.

13. Function of lymph nodes
1. Filtration.
1. Immune system activation.
1. Production of lymphocytes.

14. Other Lymphoid Organs: spleen
Spleen : is the largest lymphatic organ.
Located: in the upper left abdominal quadrant.
Contains two tissue types:
*White pulp
*Red pulp

15. Function of the spleen
1 - acts as a blood filter and controls the amount of red blood cells and blood storage in
the body.
2 - help to fight infection.

16. Other Lymphoid Organs : Tonsils
Definition : The tonsils are small masses of lymphoid tissue that
ring the pharynx (the throat)
.
The function: Their job is to trap and remove any bacteria or
other foreign pathogens entering the throat.
Disorder : sometimes they become congested with bacteria and
become red, swollen, and sore,a condition called tonsillitis
.

17. Lymphatic Vessels
Lymphatic vessels are tupe-shaped structures of the lymphatic system that transport
fluid away from tissues - the lymph.
This fluid becomes the interstitial fluid that surrounds cells.
Functions:
Lymphatic vessels collect and filter this fluid before directing it toward blood vessels
near the heart. Then, that lymph re-enters blood circulation.
Returning lymph to the blood helps to maintain normal blood volume and pressure.
It prevents edema, the excess accumulation of fluid around tissues.

18. Lymphatic Vessels
Structure:
Large lymphatic vessels are composed of three layers. - tunica intima, tunica media,
and tunica adventitia.
Tunica Intima - lymph vessel inner layer composed of smooth endothelium (type of
epithelial tissue). This layer contains valves in some lymph vessels to prevent fluid
backflow.
Tunica Media - lymph vessel middle layer composed of smooth muscle and elastic
fibers.
Tunica Adventitia - lymph vessel strong outer covering composed of connective
tissue as well as collagen and elastic fibers. The adventitia attaches lymphatic

19. THYMUS
- The thymus gland is the main organ of the lymphatic system. Located in the upper
chest region.
- The primary function of this gland is to promote the development of specific cells of
the immune system called T lymphocytes.
- T lymphocytes (T-cells) are white blood cells that protect against foreign organisms
(bacteria and viruses) that have managed to infect body cells. They also protect the
body from itself by controlling cancerous cells.
- From infancy to adolescence, the thymus is relatively large in size. After puberty, the
thymus begins to decrease in size and continues to shrink with age.

20. THYMUS ANATOMY
The thymus is a two-lobed structure that is
positioned in the upper chest cavity.
The thymus is situated above the
pericardium of the heart, in front of the
aorta, between the lungs, below the thyroid,
and behind the breastbone.
The thymus has a thin outer covering called
a capsule.

21. THYMUS HISTOLOGY
Thymus consist of three cells:
Epithelial cells - tightly packed cells that give shape and structure to the thymus.
Lymphocytes - immune cells that protect against infection and stimulate an immune
response.
Kulchitsky cells { neuroendocrine }- hormone-releasing cells.
Each lobe of the thymus contains many smaller divisions called lobules.
A lobule consists of an inner area called the medulla and an outer region called the
cortex.
The cortex region contains immature T lymphocytes. The medulla region contains the
larger, mature T-lymphocytes. While T lymphocytes mature in the thymus, they
originate from bone marrow stem cells. Immature T-cells migrate from the bone
marrow to the thymus via the blood. The "T " in T lymphocyte stands for thymus-
derived.

22. Vermiform Appendix Anatomy
In Latin, the term "vermiform" means worm-shaped. Although the appendix ranges
from a length of two centimeters to twenty centimeters, the average length is ten
centimeters. The appendix usually has a diameter between seven and eight millimeters.
The vermiform appendix is attached dorsomedially to the end of the cecum where all
three taeniae converge. It is 2 to 15 cm long and lies often intraperitoneally retrocecal
or in the lesser pelvis. The appendix is attached to the posterior abdominal wall by the
mesoappendix. Here taeniae, haustra, semilunar folds and appendices epiploicae are all
absent.

23. Vermiform Appendix Histology
Histologically the appendix looks quite similar to the colon and cecum. A distinctive
feature is however the numerous lymph follicles and the parafollicular tissue in the
connective tissue layer of the mucosa (lamina propria mucosae) and the submucosa.
The crypts are particularly deep so that the follicles are in close contact to the
intestinal lumen. M-cells (microfold cells) are found in the epithelium which access
antigens from the intestinal lumen. As the appendix lacks taeniae it has a regular outer
longitudinal musculature.

24. Circulatory
System
Similarities Lymphatic
System
● Both are circulatory systems.
● The medium is contained in vessels.
Comparison of the Circulatory and
Lymphatic Systems

25. Circulatory System Differences Lymphatic System
● Closed continuous
circuit throughout
the body.
● Comprises of the
heart, arteries, veins
and capillaries.
Structure ● Open circuit from the
tissues into lymphatic
vessels.
● Comprises of right
lymphatic duct and
thoracic duct, lymph
nodes, lymphatic
vessels and
capillaries, thymus
and spleen.
Blood Medium Lymph
Erythrocytes, leucocytes,
platelets, dissolved
substances, waste products
and protein plasma.
Composition of medium Leucocytes, dissolved
substances, waste products
and protein plasma.

26. Circulatory System Differences Lymphatic System
Collects and distributes oxygen,
nutrients, waste products and
hormones to the tissues of the
entire body.
Role of medium Collects and removes waste
products left behind in the
tissues.
By the kidneys. Filtration By lymph nodes.
Blood is visible and damaged
blood vessels cause obvious signs.
Vessel damage Lymph is invisible and damaged
lymphatic system is difficult to
detect.
Blood is propelled throughout
the body by the pumping of the
heart and the muscular
movement.
Propulsion Lymph is not pumped. It
passively flows from the tissues
into the lymph capillaries aided
by muscular movement,
breathing mechanism and blood
circulation.

27. circulation lymphatic system
•Mingled among the blood capillaries throughout your body is another
network of tiny, thin-walled vessels called lymphatic capillaries.
Lymphatic capillaries are designed to pick up the fluid that leaks into
your tissues from your bloodstream and return it to your circulatory
system.

28. circulation lymphatic system
•Just like their neighboring blood capillaries, your
lymphatic capillaries join into progressively larger tubes
called lymphatic vessels, which transport the fluid from
your tissues (this fluid is now called lymph) toward the
center of your body. Eventually, the lymph is returned to
your bloodstream through two large ducts in the upper
central portion of your chest.
•The largest of these lymphatic ducts, the thoracic duct,
originates in your abdomen, where it collects lymph from
your legs, intestine, and other internal organs. As it
proceeds upward into your chest, the thoracic duct
collects lymph from your thoracic organs, your left arm,
and the left side of your head and neck.

29. Circulation Of the Lymphatic System
The right lymphatic duct, which is much
shorter than the thoracic duct, begins high in
the right side of your chest. It collects lymph
from the right side of your chest wall, your
right arm, and the right side of your head
and neck. The thoracic duct and the right
lymphatic duct reintroduce lymph to your
bloodstream through the large veins
returning to your heart from your arms: the
left and right subclavian veins.

30. How the lymphatic system works with other
systems?Cardiovascular system
Lymphatic vessels pick up leaked plasma and proteins; spleen destroys aged RBCs, stores
iron, and removes debris from blood; immune cells protect cardiovascular organs from
specific pathogens
Blood is the source of lymph; lymphatics develop from veins; blood provides the route for
circulation of immune elements
Nervous system
The lymphatic vessels pick up leaked plasma fluid and proteins in the peripheral nervous
system structures; immune cells protect peripheral nervous system structures
from specific pathogens
The nervous system innervates larger lymphatic vessels;the brain helps regulate immune
response

31. How the lymphatic system works with other
systems?Urinary system
Lymphatic vessels pick up leaked fluid and proteins from urinary organs; immune cells
protect urinary organs from specific pathogens
Urinary system eliminates wastes and maintains homeostatic water/ acid-base/electrolyte
balance of the blood for immune cell functioning; urine flushes some pathogens out of
the body
Endocrine System
Lymphatic vessels pick up leaked fluids and proteins; lymph distributes hormones;
immune cells protect endocrine organs from pathogens
The thymus produces hormones that promote development of lymphoid organs and

32. How the lymphatic system works with other
systems?Reproductive system
Lymphatic vessels pick up leaked fluid and proteins from reproductive organs; immune
cells protect the organs from specific pathogens
Acidity of vaginal secretions prevents bacterial multiplication
Respiratory system
Lymphatic vessels pick up leaked fluid and proteins from respiratory organs; immune cells
protect respiratory organs from specific pathogens; plasma cells in the respiratory
mucosa ecrete IgA to prevent pathogen invasion of deeper tissues
The lungs provide oxygen needed by lymphoid/immune cells and eliminate carbon
dioxide; the pharynx houses tonsils; the respiratory “pump” aids lymph flow

33. How the lymphatic system works with other
systems?Integumentary System
Lymphatic vessels pick up leaked plasma fluid and proteins from the dermis; lymphocytes
in lymph enhance the skin’s protective role by defending against specific pathogens
The skin’s keratinized epithelium provides a mechanical barrier to pathogens; acid pH of
skin secretions inhibits growth of bacteria on skin
Digestive system
Lymphatic vessels pick up leaked fluids and proteins from digestive organs; lymph
transports some products of fat digestion to the blood; lymphoid nodules in the wall of
the intestine prevent invasion of pathogens
The digestive system digests and absorbs nutrients needed by cells of lymphoid organs;
gastric acidity inhibits pathogens’ entry into blood

34. How the lymphatic system works with other
systems?Skeletal system
Lymphatic vessels pick up leaked plasma fluid and proteins from the periostea; immune
cells protect bones from specific pathogens
The bones house hematopoietic tissue (red marrow) which produces the cells that
populate the lymphoid organs and provide body immunity
Muscular system
Lymphatic vessels pick up leaked fluid and proteins from skeletal muscle; immune cells
protect muscles from specific pathogens
The skeletal muscle “pump” aids the flow of lymph; muscles protect superficial lymph
nodes

35. Difference between Immune System and
Lymphatic SystemLymphatic System Immune System
The main function The main function is fluid
recovery, immunity, and lipid
absorption
Provide long term immunity and
defend against foreign substances
by activating immune responses
The anatomy Has specific anatomy No specific anatomy
Made of composed of lymph nodes, lymph
vessels, and other related organs
while
made up of basically B and T
lymphocytes

36. Difference between Immune System and
Lymphatic System
Lymphatic System Immune System
Associated with associated with the
cardiovascular system
mainly associated with
nervous and endocrine
systems
The relationship The products of the immune system are
transported in the lymphatic system

37. Disease of the lymphatic system
Lymphedema
Lymphedema is a build-up of lymph fluid in the fatty tissues just under your skin. This
build-up causes swelling (or edema), most often in the arms or legs. Lymphedema can
result from surgery or radiation therapy to treat certain cancers.

38. Types of lymphedema
Primary Lymphedema
It’s largely hereditary, meaning you’re born with it. This is less common than
secondary lymphedema. You’re more likely to have primary lymphedema if a family
member is also affected..
Secondary lymphedema
Secondary lymphedema results from an identifiable damage to or obstruction of
normally-functioning lymph vessels and nodes.

39. Causes of lymphedema
Surgery
Radiation treatment for cancer
Cancer
Infection

40. Symptoms of lymphedema
Fever
Decreased flexibility of hands
Aching and pain
Skin rash
Swelling of the arm
Weight loss

41. Prevention of lymphedema
Avoid insect bites and sunburns
Do not carry a heavy purse on an affected arm
Practice skin hygiene
Keep the body adequately hydrated

43. DEFINITION OF IMMUNE SYSTEM
The bodily system that protects the body from foreign substances,
cells, and tissues by producing the immune response and that includes
especially the thymus, spleen, lymph nodes, special deposits of
lymphoid tissue (as in the gastrointestinal tract and bone marrow),
macrophages, lymphocytes including the B cells and T cells, and
antibodies.

44. FUNCTION OF THE IMMUNE SYSTEM
The major function of the immune system is to protect the host from
environmental agents such as microbes or chemicals, thereby
preserving the integrity of the body. This is done by the recognition
of self and response to nonself. The immune response has been
artificially divided into innate immunity (resistance) and specific
immunity. Specific immunity is further divided into humoral
immunity, the one involved with antibody, and cellular immunity,
which is orchestrated by T cells.

45. COMPONENTS OF THE IMMUNE
SYSTEM● Lymph nodes: Small, bean-shaped structures that produce and store cells
that fight infection and disease and are part of the lymphatic system.
● Spleen: The largest lymphatic organ in the body, which is on your left side,
under your ribs and above your stomach, contains white blood cells that fight
infection or disease.
● Bone marrow: The yellow tissue in the center of the bones produces white
blood cells.
● Lymphocytes: These small white blood cells play a large role in defending
the body against disease.The two types of lymphocytes are B-cells, which
make antibodies that attack bacteria and toxins, and T-cells, which help
destroy infected or cancerous cells. Killer T-cells are a subgroup of T-cells
that kill cells that are infected with viruses and other pathogens or are
otherwise damaged. Helper T-cells help determine which immune responses
the body makes to a particular pathogen.

46. ● Thymus: This small organ is where
T-cells mature. This often-
overlooked part of the immune
system, which is situated beneath
the breastbone (and is shaped like
a thyme leaf, hence the name),
can trigger or maintain the
production of antibodies that can
result in muscle weakness.
● Leukocytes: These disease-
fighting white blood cells identify
and eliminate pathogens and are
the second arm of the innate
immune system. A high white
blood cell count is referred to as
leukocytosis.

47. Immune system
The Immune system is composed of two major subdivisions. They are :
Non specific immunity.
Specific immunity.

48. Non specific immunity
Nonspecific immunity includes the external physical and chemical barriers provided
by the skin and mucous membranes.
It also includes various internal defenses, such as antimicrobial substances, natural
killer cells, phagocytes, inflammation, and fever.
The nonspecific line of defences are :
First line of defence
Second line of defence

49. First line of defence (skin and mucous)
The skin provides a barriers that discourage pathogens and foreign substances from
penetrating the body and causing disease.
With its many layers of closely packed, keratinized cells,the epidermis—provides a
formidable physical barrier to the entrance of microbes
The epithelial layer of mucous membranes,secretes a fluid called mucus that
lubricates and moistens the cavity surface. It traps many microbes and foreign
substances.

50. Second Line of Defense (Internal Defenses)
When pathogens penetrate the physical and chemical barriers of the skin and mucous
membranes, they encounter a second line of defense: internal antimicrobial
substances, phagocytes, natural killer cells, inflammation, and fever.

51. Antimicrobial
An antimicrobial is an agent that kills or inhibits the growth of microorganisms.
These agents interfere with the growth and reproduction of causative organisms
like bacteria, fungi, parasites, virus etc.
Phagocytes
Phagocytes are specialized cells that ingest microbes or other particles.The two
major types of phagocytes are neutrophils and macrophages
Natural killer cells
They have the ability to kill a wide variety of infected body cells and certain tumor
cells. They attack any body cells that display abnormal or unusual plasma
membrane proteins.

52. Fever
Fever is an abnormally high body temperature that occurs because the hypothalamic
thermostat is reset.
Elevated body temperature intensifies the effects of interferons, inhibits the growth
of some microbes, and speeds up body reactions that aid repair.
Inflammation
Inflammation is a nonspecific, defensive response of the body to tissue damage.
It is caused due to pathogens, abrasions, chemical irritations, distortion or
disturbances of cells, and extreme temperatures.
Inflammation is an attempt to dispose of microbes, toxins, or foreign material and
tissue repair.

53. Third line of Defences
Also known as Acquired Immune system
It is specific
Long time period between exposure and maximal response
Has immunological memory
Is flexible
Components are T lymphocytes and B lymphocytes

54. Activation of lymphocytes
Lymphocytes are formed in the bone marrow
Those that are matured in the thymus gland are called T-cells
Those that mature in the bone marrow are called B-cells
Before B-cells leave bone marrow (antibodies) and T-cells leave thymus, they must
become immunocompetent. This is achieved by developing surface receptors
capable of recognizing various antigens.
Specific immunity is two kinds:
● Cell-mediated immunity
● Antibody-mediated immunity

55. Cell-mediated Immunity
Involves T-cells: They are four kinds:
● Cytotoxic T-cells
● Helper T-cells
● Memory T-cells
● Suppressor T-cells
Once a T-cell (helper or cytotoxic T-cell) binds to an antigen, it is activated.
It undergoes clonal selection (making clones)
It starts secreting many cytokines, one of which activates cytotoxic T-cells, B-cells

56. Cytotoxic T-cells are the soldiers. They recognise and attach to target cells which
are:
Infected body cells
Tumour cells
Cells of a tissue transplant
Cytotoxic T cells have two principal mechanisms for killing infected target cells:
By producing protein digesting enzymes that causes apoptosis of infected cells. Microbes are
released and killed by phagocytes
By producing perforin that insert into the plasma membrane of the target cell and creates

57. Antibody-mediated Immunity
B-cells, unlike T-cells, are rarely found in circulation.
Upon interaction with foreign antigen and usually with the assistance of T helper
cells, B lymphocytes become mature antibody secreting cells called plasma cells.
A few days after exposure to antigens, plasma cells secrete hundreds of millions of
antibodies each day for 4-5 days, after that they die.
Antibodies produced by a clone of plasma cells enter the circulation and form
antigen–antibody complexes with the antigen.
Memory B cells do not secrete antibodies. Instead, they can quickly differentiate into
more plasma cells and more memory B cells should the same antigen reappear at
a future time.

58. Structure of Antibodies
An antibody (also called
immunoglobulins) can combine
specifically with the epitope on the
antigen, the antibody’s structure
matches its antigen
Almost all antibodies are made of 4
polypeptide chain.
2 of them are identical, called heavy
chains
2 of them are light chains.

59. Function of Antibodies
Antibodies inactivate antigens in a number of ways:
Complement fixation
Neuralization
Agglutination or precipitation
The most Important is the complement system. It is activated when antibodies bind
to antigens and are recognized by complement protein. One result of complement
fixation is formation of substances that that make holes in the foreign cell’s
surface.
Agglutinating and precipitating antigen: Because antibodies have two or more sites
for binding to antigen, the antigen– antibody reaction may cross-link pathogens

60. References :- (Books)
● Human Biology Book. Sylvia S. Mader & Michael Windelspecht. 12th edition. chapter 7.pages 137 and 140
● Essential of human anatomy and physiology 11th edition pg. no. 399 402 , 403
● Human biology 14th edition MC GRAW-HILL EDUCATION, chp 7, pg no.132
● Essential of human anatomy and physiology 11th edition pg. no. 430
● Principles of Anatomy and Physiology 13th ed - G. Tortora, B. Derrickson

61. References:- (Websites)
● http://www.livestrong.com/article/73427-human-body-systems-work-immune
● http://www.livescience.com/26983-lymphatic-system.html
● https://www.google.com.sa/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&uact=8&ve
d=0ahUKEwiynLO9zprTAhUICBoKHaVbDXcQFghKMAY&url=http%3A%2F%2Fstudy.com%2F
academy%2Flesson%2Flymphatic-vessels-definition-function-
quiz.html&usg=AFQjCNFjHS_1yefHS0JyddYSbKbq_lKnFQ&sig2=8E-uVv2FEaQ7JRKLU2Eq4g
● http://www.kean.edu/~jfasick/docs/Fall%2009%20&%20SP10%20%20A&PII/Chapter%2020.pdf

62. Thank you