Lymphatic System

Question 1

Describe the lymphatic system

Answer 1

Consists of a group of cells, tissues and organs that monitor body surfaces and internal fluid compartments and react to the presence of potentially harmful substances

The lymphatic system is unique, in that it is a 1-way system that returns lymph fluid via vessels to the cardiovascular system for eventual elimination of toxic byproducts by end organs, such as the kidney, liver, colon, skin, and lungs

Question 2

What are the functions of lymphatic system?

Answer 2

1. Drainage of fluid
2. Absorption of transportation of fat
3. Immune function
4. Production and maturation of immune cells
5. Filtration of lymph
6. Large compounds and hormones

Question 3

Explain how the lymphatic system drains fluid

Answer 3

One of the main functions of the lymphatic system is to collect and return tissue fluid from intracellular spaces in all the tissues of the body back to systemic circulation

-Plasma proteins contained in the lymph is also returned to circulation via this means

Question 4

Explain how the lymphatic system absorbs and transports fat

Answer 4

Lymphatic vessels located in the villi of the gastrointestinal tract (GIT) known as lacteals are responsible for absorption and transport of ingested lipids.

-Fat soluble vitamins are also absorbed with the lipids via the same means

Question 5

Explain how the lymphatic system contributes to immune functions

Answer 5

• specific. The lymphatic system is associated with cells originating from the bone marrow which mount specific responses in the presence of an antigen or foreign body
• The B and T lymphocytes recognize foreign cells, toxins, microbes and cancer cells. Their response are specific to a particular antigen or foreign cell
• Other cells like macrophages, neutrophils, eosinophils etc are also found in the lymphatic system and participate in the immune system. Their response may be however less

Question 6

How does the lymphatic system control production and maturation of immune cells

Answer 6

The bone marrow and thymus are responsible for the production and maturation of the T and B lymphocytes

Question 7

How does the lymphatic system filtrate lymph

Answer 7

The lymph nodes perform filtration function of lymph and trap particles that may be contained in the lymph before it is returned to circulation

Question 8

Large molecules/ hormones are ….

Answer 8

Transported through the lymphatic system

Question 9

What are the components of the lymphatic system ?

Answer 9

• lymphatic fluid
• lymphatic vessels
• lymphatic tissue/organ
• red bone marrow

-Specialized or immune cells e.g.
Lymphocytes, macrophages, neutrophiles, eosinophils, antigen presenting cells etc.

Question 10

Why does the lymphatic system work synergistically with the immune system and circulatory system?

Answer 10

The end result is to ensure immunity and return of lymphatic fluid back to circulation

Question 11

What is the function of lymph?

Answer 11

Contains nutrients, oxygen, hormones, and fatty acids, as well as toxins and cellular waste products, that are transported to and from cellular tissues

Question 12

What is the function of the lymphatic vessel?

Answer 12

Transport lymph from peripheral tissues to the veins of the cardiovascular system

Question 13

What 9d the functions of lymph nodes

Answer 13

Monitors the composition of lymph, the location of pathogen engulfment and eradication, immunologic response, and the regulation site

Question 14

What is the function of the spleen?

Answer 14

Monitors the composition of blood components, the location of pathogen engulfment, eradication, the immunologic response and the regulation site

Question 15

What is the function of the thymus?

Answer 15

Serves as the site of T- lymphocyte maturation, development, and control

Question 16

Differentiate lymphoid tissue and organs

Answer 16

Lymphoid tissue (connective tissue capsule: no)

Lymphoid tissue organs (connective tissue capsule:yes)

Question 17

Describe the types of lymphoid organs

Answer 17

A. Primary lymphoid organs:

• bone marrow.
• thymus

B. Secondary lymphoid organs

• lymph node
• spleen

Question 18

Describe the types of lymphoid tissue

Answer 18

A. Diffuse lymphoid tissue

• loose type: few lymphocytes present
• dense type: many lymphocytes present

B. Nodular lymphoid tissue

• solitary nodules
• aggregate nodules

Question 19

Describe the lymphatic nodule

Answer 19

Collection of B lymphocytes

• pale staining central region- germinal center
• when activated in presence of invading microorganism, B cells proliferate producing plasma cells- antibody producing cells
• macrophages are also found in the general center

Question 20

Explain the formation of lymph

Answer 20

Lymph is ultrafiltrate go blood

• interstitial fluid is formed at the arterial end of capillaries and reabsorbed at the veinous end
• About 10-20% of this fluid is not reabsorbed in the venous end-lymph fluid
• This 10-20% of fluid enters the lymphatic system via the lymph vessels
• there is a difference between the composition of plasma and lymph fluid

Question 21

Explain the fundamentals of lymph flow

Answer 21

Flow rate of lymph is generally low. An increase in pressure of interstitial causes increase flow into the lymph vessels

• Valves in lymph vessels prevent retrograde flow
• Skeletal muscle pump and Respiratory pump also effect (enhance) the flow rate of lymph
• There are lymphatic vessels in most areas of the body except the Brain, bone marrow and avascular areas such as epithelia and cartilages

Skeletal muscle contraction and pulses generated by arteries help to propel lymph through lymphatic channels

Question 22

Outline lymph circulation

Answer 22

1. Lymphatic capillaries
2. Lymphatic vessels
3. Lymph nodes
4. Lymph trunks
5. Cisterna chyli
6. Lymph ducts
7. Blood

Question 23

What is thymus embryologically developed from?

Answer 23

From the third pharyngeal pouch

Question 24

Where is the thyroid located?

Answer 24

The superior mediastinum

Question 25

Describe the development of the thyroid

Answer 25

It is well developed in early childhood - thymus begins involution at puberty - by adulthood, most of the thymus has atrophied and replaced by adipose tissue

Question 26

What is the purpose of the thymus?

Answer 26

Location for proliferation and maturation of T cells (originate from the bone marrow)

Question 27

Explain the structure of the thymus

Answer 27

Covered by a thin connective tissue capsule - Trabeculae from the connective tissue divide it into lobes. - Each lobule contains a cortex and a medulla - Cortex contains mainly immature T lymphocytes, is darker staining (due to tightly packed lymphocytes) and also contains special type of cells called Epithelial Retivular Cells (ERCs) - ERCs establish a protective blood-thymus barrier that prevents the developing thymocytes from coming in contact with antigens - The medulla is lighter staining - due to less lymphocyte concentration. Also contains more ERCs - Epithelial reticular cells degenerate or keratinized in the medulla into Hassan (thymic) corpuscles The Thymus contains no afferent lymph vessels (unlike the lymph node)

Question 28

Describe red bone marrow

Answer 28

Is a primary lymphoid organ - Site of production of T and B lymphocyte - Immature and naïve T lymphocytes exit the bone marrow to the thymus for maturation and differentiation - B lymphocytes develop, mature and differentiate in the bone marrow

Question 29

Describe the lymph node

Answer 29

- Kidney or bean shaped - Contains a lot of reticular fibers - Encapsulated -dense connective tissue - Trabeculae divides nodes into compartments. - Efferent and afferent lymphatic vessels - Subdivisions are the cortex and medulla - Filters lymph and mounts immune response via recirculation of lymphocyte - Has a Hilum where arteries and veins + efferent lymphatic exit - Afferent lymphatic vessels drain lymph through the convex margin

Question 30

Describe cortex of the lymph node

Answer 30

Outer cortex: lymph nodules, B cells Inner cortex (paracortex): T cells, dendritic cells

Question 31

Describe the medulla of the lymph node

Answer 31

B cells, retivular cells, reticular fibers, sinuses and cords: reticular fibers, lymphocytes, macrophages

Question 32

Describe the flow of lymph through the lymph node

Answer 32

Lymph from afferent lymphatic vessels Drain into subscapular sinuses - From the subscapular sinuses, lymph flow into the trabecular sinuses - then to the medullary sinuses - and finally exit via the efferent lymphatics in the hilum of the lymph node

Question 33

Describe the spleen

Answer 33

Is a secondary lymphatic organ - major function of the spleen is to filter blood - located at the left-posterior abdominal wall under cover of ribs 9-11 - largest lymphoid organ - It is covered by a dense connective tissue capsule which continues as Trabeculae in the paranchyme of the organ - Unlike lymph nodes, contains no cortex or medulla

Question 34

What does the spleen consist of?

Answer 34

Red pulp and white pulp

Question 35

Describe red pulp in the spleen

Answer 35

- contains capillary sinusoids | - splenic cords (of Billroth): laced with lymphocytes, macrophages, plasma cells, granulocytes etc

Question 36

Describe the white pulp of the spleen

Answer 36

- consists of focal accumulation of lymphocytes with macrophages - central artery located in the white pulp is ensheathed by T lymphocytes ( peri arteriolar lymphatic sheath ), PALS - Marginal zone is the area around the white pulp and is rich in macrophages and antigen presenting cells

Question 37

What is contained in the white pulp of the spleen?

Answer 37

Veinous sinuses Splenic cords Lymphocytes Macrophages, plasma cells Granulocytes, RBC

Question 38

What are the general parts of the splenic parenchyma?

Answer 38

White and red pulp

Question 39

What is the function of red pulp of spleen?

Answer 39

- Removal by macrophages of ruptured, worn out, or defective blood cells and platelets - Storage of platelets, up to one-third of the body’s supply - Production of blood cells during fetal life

Question 40

What is the function of white pulp of the spleen ?

Answer 40

- B cells and T cells carry out immune functions | - Macrophages destroy blood-prone pathogens by phagocytosis

Question 41

Describe the tonsils

Answer 41

Tonsils are lymphoid tissues - Part of gut associated lymphoid tissue (GALT) - process antigens that may attack the body via the oral or nasal cavity - Are partially encapsulated - Include the pharyngeal tonsil, palatine tonsil, and lingual tonsil - Together they form a lymphoid ring at the back of the oral cavity called Waldeyer’s ring - Tonsillitis= inflammation of the tonsils

Question 42

Describe the pharyngeal tonsils

Answer 42

- Located at the posterior wall of the pharynx - Called adenoids when enlarged by inflammation - Contains many lymph nodules

Question 43

Describe the palatine tonsils

Answer 43

- Paired tonsil found on either side of the mouth posteriorly - Contains deep crypts formed by epithelial invagination - Mainly secondary nodules are found in this region

Question 44

Describe lingual tonsils

Answer 44

- Found at the posterior aspect of the tongue - Also contains crypts(shallow) - Associated with mucus glands

Question 45

What is tonsillitis ? Common causes and symptoms

Answer 45

Inflammation of the tonsils Common causes- Virus, bacteria Symptoms- headache, fever, malaise enlarged lymph nodes in the neck, dysphagia

Question 46

What are mucosa associated lymphatic tissue?

Answer 46

Located in the lamina propria of the mucosa lining -May be arranged in aggregate of lymph nodules

Question 47

Give the examples of MALT

Answer 47

RALT- respiratory system, genitourinary system NALT- nasal cavity GALT- gut associated lymphoid tissue.g. Stomach, esophagus, peyers patches, colon, tonsils

Question 48

What are peyers patches?

Answer 48

A lymphoid nodule - Are located in the ileum (distal portion of the small intestine ) - Consists of numerous aggregates of lymphatic nodules containing T and B lymphocytes

Question 49

Describe the right lymphatic duct

Answer 49

Drains lymph from the following parts of the body: - Upper right side of the trunk above the diaphragm (via the right Bronchomediastinal trunk) - Right upper limb (via right subclavian trunk) - Right side of the head and neck(via right jugular trunk) - The right lymphatic duct usually drains into the right Subclavian, at its junction with the right internal jugular vein

Question 50

Describe the thoracic duct

Answer 50

- Is the largest lumphatic vessel in the human body - Starts at the level of the 2nd lumbar vertebra and extends to the neck - Collects and drains lymph from the lower part of the body below the diaphragm , left side of the trunk above the diaphragm, the left upper limb and the left side of the head and neck - Empties into the left brachiocephalic vein