Chapter 20 - The Lymphatic System and Lymphoid Organs and Tissues Flashcards
1
Q
What is the function of the lymphatic system?
A
Returns fluids that leaked from blood vessels back to the blood.
2
Q
The three parts of the lymphatic system are:
A
- network of lymphatic vessels (lymphatics)
- Lymph
- Lymph nodes
3
Q
What is lymph?
A
fluid in vessels
4
Q
What is the function of lymph nodes?
A
cleanse lymph
5
Q
What are the characteristics of lymphoid organs and tissues?
A
- they provide the structural basis of the immune system
2. they house phagocytic cells and lymphocytes
6
Q
Lymphoid organs and tissue structures include:
A
- spleen
- thymus
- tonsils
- other lymphoid tissues
7
Q
What is the overall function of the lymphatic vessels?
A
- they return interstitial fluid and leaked plasma proteins back to the blood
- ~3L/day
8
Q
Once interstitial fluid enters lymphatics, what is it called?
A
lymph
9
Q
Lymphatic vessels - Distribution and structure:
A
- one-way system
- lymph flows toward heart
- contains lymph vessels (lymphatics)
10
Q
What are the three main lymph vessels?
A
- lymphatic capillaries
- collecting lymphatic vessels
- lymphatic trunks and ducts
11
Q
Lymphatic capillaries are similar to blood capillaries, except for a couple of differences. What are they?
A
- very permeable
2. pathogens travel throughout the body via lymphatics
12
Q
Lymphatic capillaries take up what?
A
- proteins
- cell debris
- pathogens
- cancer cells
13
Q
What are the characteristics of lymphatic capillary permeability?
A
- endothelial cells overlap loosely to form one-way minivalves
- anchored by collagen filaments, preventing collapse of capillaries
- increased ECF volume opens minivalves
14
Q
Lymphatic capillaries are absent from:
A
- bones
- teeth
- bone marrow
- CNS
15
Q
What are lacteals?
A
specialised lymph capillaries present in intestinal mucosa
16
Q
What is the function of lacteals?
A
they absorb digested fat and deliver fatty lymph to the blood
17
Q
fatty lymph is also known as
A
chyle
18
Q
Lymphatic collecting vessels are similar to veins, except for a couple of differences. What are they?
A
- they have thinner walls, with more internal valves
2. they anastomose more frequently
19
Q
Lymphatic collecting vessels in the skin travel with ____.
A
superficial veins
20
Q
Deep lymphatic collecting vessels travel with ___.
A
arteries
21
Q
Nutrients are supplied to lymphatic collecting vessels via branching ____.
A
vasa vasorum
22
Q
The lymphatic trunks are formed by the union of the largest collecting ducts, which are:
A
- paired lumbar
- paired bronchomediastinal
- paired subclavian
- paired jugular trunks
- single intestinal trunk
23
Q
Lymph is delivered into one of two large ducts, which are:
A
- right lymphatic duct
2. thoracic duct
24
Q
What is the function of the right lymphatic duct?
A
it drains the right upper arm and right side of head and thorax
25
What is the function of the thoracic duct?
it drains the rest of the body
26
The thoracic duct arises from ____.
cisterna chyli
27
Each lymphatic duct empties lymph into ___ circulation.
venous
28
Where is lymph emptied within venous circulation?
at the junction of internal jugular and subclavian veins on its own side of the body
29
Lymph is propelled by:
1. milking action of skeletal muscle
2. pressure changes in thorax during breathing
3. valves to prevent backflow
4. pulsations of nearby arteries
5. contractions of smooth muscle in walls of lymphatics
30
The main warriors of the immune system are ____.
lymphocytes
31
Lymphocytes arise in:
red bone marrow
32
Lymphocytes mature into one of two main varieties, which are:
1. T cells (T lymphocytes)
| 2. B cells (B lymphocytes)
33
T cells and B cells protect against ____.
antigens
34
Antigens are:
anything the body perceives as foreign
35
What are examples of antigens?
1. bacteria and bacterial toxins
2. viruses
3. mismatched RBCs
4. cancer cells
36
What is the function of T cells?
1. manage immune response
| 2. attack and destroy infected cells
37
What is the function of B cells?
they produce plasma cells, which secrete antibodies
38
What do antibodies do?
they mark antigens for destruction by phagocytosis or other means
39
Other lymphoid cells are:
1. macrophages
2. dendritic cells
3. reticular cells
40
What do macrophages do?
1. phagocytise foreign substances
| 2. help activate T cells
41
What do dendritic cells do?
capture antigens and deliver them to lymph nodes
42
What do reticular cells do?
they produce the reticular fibre stroma that supports other cells in lymphoid organs
43
What is the overall function of lymphoid tissue?
1. houses and provides proliferation for lymphocytes
| 2. surveillance vantage point for lymphocytes and macrophages
44
Lymphoid tissue is largely composed of ____.
reticular connective tissue
45
What is reticular connective tissue?
a type of loose connective tissue
46
The two main types of lymphoid tissue are:
1. diffuse lymphoid tissue
| 2. lymphoid follicles
47
Diffuse lymphoid tissue of lymphoid cells and reticular fibres is found in:
~ every body organ
48
There are larger collections of diffuse lymphoid tissue in:
the lamina propria of mucous membranes
49
Structural characteristics of lymphoid follicles (nodules):
1. solid, spherical bodies of tightly packed lymphoid cells and reticular fibres
2. there are isolated aggregations of Peyer's patches and in appendix
50
Lymphoid follicles are the germinal centres of:
proliferating B cells
51
Lymphoid follicles may form part of:
larger lymphoid organs
52
The principal lymphoid organs of the body are:
lymph nodes
53
Where are lymph nodes found?
1. embedded in connective tissue, in clusters along lymphatic vessels
2. near body surface in inguinal, axillary, and cervical regions of the body
54
The functions of lymph nodes include:
1. filter lymph
| 2. immune system activation
55
When lymph nodes filter lymph, what happens?
macrophages destroy microorganisms and debris
56
When lymph nodes activate the immune system, what happens?
lymphocytes are activated and mount attack against antigens
57
Lymph node shape:
vary in size and shape, but most are bean shaped
58
Lymph nodes contain an external:
fibrous capsule
59
What extends into the lymph node and divides it into compartments?
trabeculae
60
The two internal compartments of lymph nodes are:
1. cortex
| 2. medulla
61
Characteristics of the internal cortex of lymph nodes:
1. cortex contains follicles with germinal centres, heavy with dividing B cells
2. dendritic cells nearly encapsulate follicles
3. deep cortex houses T cells in transit
62
T cells circulate continuously among:
1. blood
2. lymph nodes
3. lymph
63
Characteristics of the internal medullary cords of lymph nodes:
1. extend inward from cortex
| 2. contain B cells, T cells, and plasma cells
64
Lymph sinuses contain ____.
macrophages
65
Lymph enters lymph nodes on the convex side via _____.
afferent lymphatic vessels
66
Once lymph enters lymph nodes, it travels through _____ then to _____.
subcapsular sinus and smaller sinuses; medullary sinuses
67
There are fewer ____ vessels in lymph nodes.
efferent
68
Why are there fewer efferent vessels in lymph nodes?
allows lymphocytes and macrophages time to function; flow is somewhat stagnate
69
The largest lymphoid organ is the ____.
spleen
70
The spleen is served by:
the splenic artery and vein
71
The splenic artery and vein enter and exit the spleen at the ____.
hilum
72
What is the function of the spleen?
1. site of lymphocyte proliferation and immune surveillance and response
2. cleanses blood of aged cells and platelets, macrophages remove debris
73
Spleen stores what?
1. breakdown products of RBCs (e.g. iron) for later reuse
| 2. blood platelets and monocytes
74
The spleen may be the site of ____ production.
fetal erythrocyte (normally ceases after birth)
75
The spleen is encased by ____, and has ___.
fibrous capsule; trabeculae
76
The spleen contains what?
1. lymphocytes
2. macrophages
3. huge numbers of erythrocytes
77
The two distinct areas of the spleen are:
1. white pulp
| 2. red pulp
78
The white pulp of the spleen is located:
around central arteries
79
White pulp contains:
mostly lymphocytes on reticular fibres
80
White pulp of the spleen is involved in:
immune functions
81
The red pulp of the spleen is located:
in venous sinuses and splenic cords
82
The red pulp of the spleen contains:
1. abundant RBCs
| 2. abundant macrophages
83
Red pulp of the spleen's composed elements function for:
disposal of worn-out RBCs and bloodborne pathogens
84
The red pulp of the spleen is composed of ____ and ____.
splenic cords; sinusoids
85
The thymus is found in:
inferior neck
86
The thymus extends into:
mediastinum
87
The thymus partially overlies:
the heart
88
What are the characteristics of the thymus?
1. important functions in early life
| 2. increases in size and most active during childhood
89
The thymus stops growing when?
during adolescence
90
After the thymus stops growing, what happens?
it gradually atrophies
91
After the thymus stops growing, it still produces:
immunocompetent cells, though slowly
92
Thymic lobules contain:
outer cortex and inner medulla
93
Most thymic cells are ____.
lymphocytes
94
The cortex of the thymus contains:
rapidly dividing lymphocytes and scattered macrophages
95
The medulla of the thymus contains:
fewer lymphocytes and thymic corpuscles
96
What do thymic corpuscles do?
they are involved in regulatory T cell development (prevent autoimmunity)
97
The thymus differs from other lymphoid organs in important ways. What are they?
1. has no follicles because it lacks B cells
| 2. does not directly fight antigens (functions strictly in T lymphocyte maturation)
98
The thymus keeps T lymphocyte maturation isolated via the _____.
blood thymus barrier
99
The stroma of epithelial cells in the thymus provide what?
environment in which T lymphocytes become immunocompetent
