Lymphatic System

Question 1

Functions of the Lymphatic System

Answer 1

• fluid recovery (2-4 L/day, prevents edema)
• immunity (lymph and blood monitored for pathogens and cancer cells)
• lipid absorption (via lacteals in small intestine)

Question 2

6 Types of Lymphatic Cells

Answer 2

T Lymphocytes - develop in thymus

B Lymphocytes - develop in red bone marrow, produce antibodies

Macrophages - develop from monocytes, phagocytotic

Natural Killer Cells (NK cells) - large lymphocytes that attack and lyse bacteria, foreign tissue, infected host cells

Dendritic Cells - branched cells in skin, antigen presenters

Reticular Cells - branched cells in stroma of lymphatic organs

Question 3

Lymphatic Fluid

• what is it?
• how is it produced?

Answer 3

AKA Lymph

• produced by filtration of plasma through capillaries

Question 4

Pathway of Lymph Flow

Answer 4

• towards the heart
• begins in dead-ended lymphatic capillaries where blood capillaries are (except: brain, teeth, bones, marrow)

Question 5

What is this structure?

Where is it found and where does it lead?

Answer 5

lymphatic capillaries

• smallest lymph vessel (larger than blood capillaries)
• permeable to lymph fluid and proteins via its valve-like overlapping endothelial cells
• dead-end at blood capillary beds and drain into lymph collecting vessels
• absent in cornea, bone marrow, CNS

Question 6

What lymphatic structures do lymphatic capillaries drain into?

What is their structure like?

Answer 6

lymphatic collecting vessels

• contain valves to molve lymph towards heart
• have the same three tunics as blood vessels, but thinner walls and lower pressure
• have lymph nodes along length to filer lymph
• lie along with veins in superficial tissues and arteries in deeper tissues

Question 7

The convergence of several lymphatic collecting vessels

Answer 7

lymphatic trunk

Question 8

the five major lymphatic trunks

Answer 8

1. Lumbar Trunk
2. Intestinal Trunk
3. Bronchomediastinal Trunk
4. Subclavian Trunk
5. Jugular Trunk

Question 9

Paired lymphatic trunks branching off of the inferior end of the thoracic duct

Answer 9

Lumbar Trunks (left and right)

• carry lymph from lower limb, pelvic region and anterior abdominal wall

Question 10

Single lymphatic trunk branching off of inferior thoracic duct

Answer 10

Intestinal Trunk

• drains lymph from stomach, intestines and other digestive organs

Question 11

part C

Answer 11

bronchomediastinal trunks (left and right)

• carries lymph from thoracic viscera
• usually open into junction of internal jugular and subclavian veins
• sometimes join right lymphatic duct and thoracic duct

Question 12

part B

Answer 12

subclavian trunks (left and right)

• lymph from upper limbs, inferior neck and superior thoracic wall
• open either into junction of internal jugular and subclavian veins or into jugular trunk and thoracic duct

Question 13

part A

Answer 13

Jugular Trunks

• drains lymph from head and neck
• right side joins the venous angle (right internal jugular and subclavian veins)
• left side joins thoracic duct

Question 14

Where do the lymphatic trunks drain?

Answer 14

• into the lymphatic ducts
• two major ducts: thoracic duct and right lymphatic duct

Question 15

Answer 15

cisterna chyli

• dilated sac at inferior end of thoracic duct
• receives lymph from intestinal and lumbar trunks
• contains lots of chyle, fat-rich intestinal lacteal lymph

Question 16

Answer 16

Thoracic Duct

• joins junction of left subclavian and internal jugular veins (the venous angle)
• drains left side of face, most of left thorax and lower body

Question 17

top left question-marked structure:

Answer 17

right lymphatic duct

• joins right venous angle
• drains right side of head and upper body
• only present in 20% of people

Question 18

what is this collection of blue structures?

Answer 18

cervical lymph nodes

Question 19

what is this grouping of green and blue structures?

Answer 19

axillary lymph nodes

Question 20

what is this grouping of green structures?

Answer 20

inguinal lymph nodes

Question 21

Lymphoid Tissue

• what kind of tissue is it?
• what cells are found in it?
• where is it found?

Answer 21

• reticular connective tissue dominated by lymphocytes (T, B cells and macrophages)
• it is found primarily in two places:
• MALT (mucosa-associated lymphoid tissue) - mucous membranes of digestive, respiratory, urinary and reproductive tracts
• all lymphoid organs except thymus

Question 22

lymphatic capillaries that absord dietary fats within the villi of the small intestine

Answer 22

lacteal

Question 23

Lymphoid Nodules

• where are they found?
• how are they different from lymphoid organs?
• describe their structure
• name examples

Answer 23

AKA lymphoid follicles

• scattered clusters within lymphoid tissue
• they lack a fibrous capsule
• they are made of densely packed lymphocytes with a (usually lighter-staining) central zone of dividing cells (the germinal center)

Ex: tonsils and peyer’s patches

Question 24

Tonsils

• what are they?
• where are they?
• what do they do?

Answer 24

• large lymphatic nodules
• located in the pharynx and on the palate and tongue
• they trap bacteria and foreign pathogens entering the mouth and nose

Question 25

B

Answer 25

**palatine tonsil** - paired tonsils at the posterior inferior margin of oral cavity

Question 26

A

Answer 26

**pharyngeal tonsils** (AKA **adenoids**) - located in posterior wall of nasopharynx

Question 27

C

Answer 27

**lingual tonsils** - located along posterior third of tongue - unpaired

Question 28

boxed structure: - what is it? - where is it? - what does it do?

Answer 28

**Peyer's patch** - large isolated clusters of lymphatic nodules - the ileal wall of the small intestine - functions to destroy bacteria and generate memory lymphocytes for long term immunity

Question 29

Lymphoid Organs - what are they? - how are they different from lymphoid nodules? - how are they classified? - give examples

Answer 29

- similar to lymphoid nodules in structure but are separated from tissues around them by a **fibrous capsule** **Primary Lymphoid Organs** - produce lymphocytes **Secondary Lymphoid Organs** - collect and destroy infectious organisms using lymphocytes ex: **Lymph Nodes, Spleen, Thymus**

Question 30

**Lymph Nodes** - what are they? - where are they? - what do they do? - what are large ones called?

Answer 30

- about 500 1-25 mm bean-shaped structures - found along lymphatic collecting vessels - macrophages within the node filter lymph of pathogens before it reaches the venous system - large ones are called **lymph glands**

Question 31

Lymph Node Structure Overview

Answer 31

- surrounded by **fibrous capsule** - fibrous **trabeculae** extend inward and split the node into compartments - divided into two regions: **cortex** and **medulla**

Question 32

How does lymph flow through lymph nodes?

Answer 32

1. it flows in through **afferent lymphatic vessels,** then... 2. through **lymph sinuses** (subscapular, cortical and medullary), where macrophages cleanse it of pathogens, then... 3. it exits through **efferent lymphatic vessels** at the **hilum** of the node back into **collecting vessels**

Question 33

round structure marked 4

Answer 33

**lymphatic nodule of lymph node** - clusters of lymphocytes in cortex of lymph node

Question 34

#3

Answer 34

**cortex** of lymph node - outer region of lymph node - consists of _cortical sinuses_ and _lymphatic nodules_

Question 35

#4

Answer 35

**medulla** of cortex - inner region of lymph node - consists of _medullary sinuses_ and _medullary cords_

Question 36

#3

Answer 36

**germinal center** - areas in lymphatic nodules where b lymphocytes undergo mitotic division

Question 37

#1

Answer 37

**medullary cords** - CT fibers that support strands of lymphatic cells

Question 38

#2

Answer 38

**medullary sinus** - lymph percolates through these sinuses

Question 39

the tiny dots that make up this image

Answer 39

**lymphocytes** - white blood cells that attack specific types of antigens

Question 40

what is the visible organ? - describe its location - what is its function? - what are the two main types of tissue within it?

Answer 40

**Spleen** (largest lymphatic organ) - located in upper left quadrant (left hypochondriac region) - it stores blood and filters it to remove antigens and old blood cells - also is site of hematopoiesis in fetus - **red pulp -** engorged with RBCs - **white pulp -** lymphocytes and macrophages collected like sleeves long central arteries

Question 41

What is the organ at the superior end of the lungs, lying medial to them? - what is its function? - and why is it shown here on a child?

Answer 41

**Thymus** - site of maturation of lymphocytes into "T" cells - secretes **thymosin** and **thymopoietin** which stimulate immunocompetency of T cells - it is most prominent in childhood when the immune system is developing, and is only 5% active by age 40

Question 42

What is this structure? What is it composed of and what is its function?

Answer 42

**Thymic** or **Hassall's Corpuscle** - found in medulla of thymus lobules - clusters of epithelial cells - functions to develop **regulatory T cells** which prevent auto-immune responses

Question 43

What is this structure and what kind of tissue does it contain?

Answer 43

**vermiform appendix** - blind-ended puch extending from cecum - contains **mucosa-associated lymphoid tissue (MALT)** which protect against pathogens entering through cecal mucosa