Lympathic System Flashcards
(124 cards)
1
Q
- What basic tissues contribute to the composition of the lymphatic system?
A
All basic tissues of the body contribute directly or indirectly to the composition of the lymphatic system.
2
Q
What systems form the hemic-lymphatic system?
A
The lymphatic system and the vascular system form the hemic-lymphatic system.
3
Q
What is the significance of the hemic-lymphatic system?
A
It is an important vascular unit that functions as a secondary defense system.
4
Q
What is considered the primary defense system of the body?
A
The skin and mucous membranes.
5
Q
Enumerate the defensive functions of the lymphatic system.
A
Production of defensive cells
Transport of materials via lymphatic vessels
Filtration of lymph and blood through lymphatic organs
Phagocytosis and production of hemoglobin
6
Q
Which organs filter lymph and which filter blood?
A
- Tonsils and lymphatic nodules filter lymph
- Spleen and hemal nodes filter blood
7
Q
What does the hemolymph node filter?
A
Both lymph and blood.
8
Q
What are the two main kinds of lymphatic tissues?
A
- Diffuse and dense, unencapsulated lymphatic tissues
- Dense, encapsulated lymphatic tissues
9
Q
Where are diffuse and dense unencapsulated lymphatic tissues located?
Context: Tissue Location / MALT
A
Found in the lamina propria, tunica submucosa, and sometimes tunica adventitia.
10
Q
What is the collective term for these lymphatic tissues associated with mucosa?
A
Mucosa-associated lymphoid tissue (MALT)
11
Q
Enumerate the components of MALT
Context: Subdivisions of MALT
A
a. Gut-associated lymphoid tissue (GALT)
b. Bronchus-associated lymphoid tissue (BALT)
c. Nasopharynx-associated lymphoid tissue (NALT)
d. Tonsils
12
Q
What types of immune cells make up the tonsils?
A
Accumulations of lymphocytes, plasma cells, and monocytes (histiocytes or macrophages)
13
Q
What effect do tonsils have on connective tissue in their location?
A
They impart a hypercellular nature to the connective tissue in the lamina propria, tunica submucosa, and tunica adventitia.
14
Q
What is the function of tonsils as part of MALT?
A
They function as a readily available second line of defense of the body.
15
Q
What structures make up the GALT in the gastrointestinal tract?
(GALT Location and Structure)
A
Solitary lymph nodules or follicles
16
Q
What happens when solitary lymph nodules enlarge and become confluent?
A
they form aggregated lymph nodules called Peyer’s patches (intestinal tonsils).
17
Q
Where are Peyer’s patches specifically located?
A
In the ileum
18
Q
What is the cellular composition of Peyer’s patches?
Context: Histology of Peyer’s Patches
A
B cells surrounded by a region of T cells and numerous antigen-presenting cells (APCs).
19
Q
What are APCs and what is their function in Peyer’s patches?
A
specialized macrophages that participate in immune responses and communicate through signaling molecules called cytokines.
20
Q
What kind of lymphatic drainage do Peyer’s patches have?
Context: Lymphatic Flow
A
No afferent lymph vessels, but have efferent lymph drainage.
21
Q
What are M cells and what is their function in the ileum?
A
Squamous cells located in the epithelium adjacent to lymph nodules.
- Replace columnar lining cells.
- Capture antigens and transfer them to macrophages in Peyer’s patches.
22
Q
Where is BALT located in the respiratory system?
A
On the walls of bronchi, particularly in regions where bronchi and bronchioles bifurcate.
23
Q
How does the epithelium covering BALT change?
A
Changes from pseudostratified columnar epithelium with goblet cells to M cells.
24
Q
Does BALT have afferent lymph vessels?
Context: Lymphatic Flow in BALT
A
No afferent lymph vessels, but there is lymph drainage.
25
How is NALT similar to GALT and BALT?
Shares the same structure and function as GALT and BALT.
26
What is the histological composition of ***tonsils?***
Tonsils are **a combination of diffuse lymphatic tissue** and **solitary and aggregated lymphatic nodules**.
27
How can the **lymphatic tissue in tonsils be described in terms of encapsulation** and similarity to other structures?
Tonsils are **accumulations of dense unencapsulated lymphatic tissue**, similar to the nodules of lymph nodes.
28
What structural features characterize tonsils in terms of immune activity?
Tonsils possess **large germinal centers** and **dense cortices**, with **extensive infiltration of lymphocytes into the surrounding connective tissue** and associated epithelium.
29
Enumerate the two main types of tonsils based on structural features.
1. Tonsils with crypts
1. Tonsils without crypts
30
What is a **crypt** in the context of tonsils?
A crypt is **a blind and sometimes branched invagination of the surface epithelium**.
31
What is a tonsillar follicle?
A tonsillar follicle is the **crypt and the associated lymphatic tissue.**
32
Enumerate the examples of tonsils with crypts and their species.
a. **Palatine tonsils** – man, horse, ruminants, and swine
b. **Lingual tonsils** – man, horse, ruminants, and swine
c. **Paraepiglottic tonsils** – sheep, goat, and swine
d. **Tubal tonsils** – swine
33
They consist of **a single lamina of lymphatic tissue**, which **may be secondarily bulged outward or slightly folded** to increase surface area.
Tonsils without Crypts
34
Enumerate the examples of tonsils without crypts and their species.
a. **Palatine tonsils** – carnivores
b. **Pharyngeal tonsils** – all domestic animals except carnivores
c. **Tubal tonsils**– ruminants
35
Do tonsils have afferent lymphatic vessels?
No, tonsils **do not** possess afferent lymphatic vessels.
36
How are materials delivered to tonsils if they lack afferent lymphatic vessels?
Materials are either **filtered into the organ** or **carried to it by cells** from the surrounding connective tissue space.
37
Do tonsils have efferent lymphatic vessels?
Yes, **efferent lymphatic vessels are present.**
38
Enumerate the dense encapsulated lymphatic tissues.
Lymph nodes
Spleen
Hemal nodes
Hemolymph nodes
Thymus
Bursa of Fabricius
39
What is the general structure of a lymph node?
Lymph nodes are **dense, encapsulated, usually bean-shaped**, and range in size from **1 mm to several centimeters**.
40
Enumerate and describe the **main structural parts** of a lymph node.
a. **Capsule** – Made of dense white fibrous connective tissue (DWFCT), continuous with trabeculae
b. **Stroma** – Composed of fine reticular fibers
c. **Parenchyma** – Has two regions:
- **Cortex** (outer): mainly lymphatic nodules
- **Medulla** (inner): cellular aggregates in cords (medullary cords) separated by connective tissue and lymph sinuses
41
How do lymphatic vessels interact with the capsule of the lymph node?
Lymphatic vessels **penetrate the capsule** on **the convex surface** and **exit from the concave surface** called ***the hilus.***
42
What is the hilus of a lymph node?
The hilus is a connective tissue space **containing efferent lymph vessels**.
43
What is the function of valves in lymphatic vessels?
They prevent backflow of lymph.
44
What constitutes an immunologically competent and active lymph nodule *(secondary nodule)*?
It consists of **a germinal center** and **an outer corona.**
45
Why is the germinal center paler than the corona? (LYMPH NODES)
Due to the **presence of fewer cells** and the pale-staining characteristics of these cells (**e.g., plasma cells)**.
46
What are the **dominant cell types** in the germinal center?
B-lymphocytes and lymphoblasts.
47
What happens to the germinal center after a period of immune activity?
**It regresses**, and **the nodule returns to its original configuration** as a *primary nodule devoid of a germinal center.*
48
What is **absent** in **immunologically** incompetent animals?
Germinal centers.
49
What is the paracortical (or subcortical) region, and what cells occupy it?
**It is the region subjacent to the lymph nodules** of the **cortex,** primarily **occupied by T-lymphocytes.**
50
hat cell types are found in the medullary cords?
B-lymphocytes, among others.
51
Enumerate the **types of lymph node sinuses.**
Subcapsular sinuses
Trabecular sinuses
Medullary sinuses
52
What lines the lymph sinuses?
Endothelial cells
53
What **cells traverse the sinuses** and attach to their walls?
**Reticular cells**, attached via cellular processes.
54
What immune cells are found among reticular cells in lymph node sinuses?
Macrophages
55
How is lymph node structure reversed in pigs?
In **porcine species**, the **lymph nodules are in the medullary region**, and the **medullary cords are located in the cortical region**, *reversing the flow of lymph from the hilus to the convex capsule surface.*
56
What is commonly observed in **horse** lymph nodes?
Fusion of cortical nodules is common.
57
What notable histological feature is seen in ox lymph nodes?
The presence of **very large germinal centers.**
58
What are the four main functions of lymph nodes?
* To produce lymphocytes
* To filter lymph
* To phagocytose foreign materials
* To produce antibodies
59
What is the defining characteristic of a hermal node?
A hermal node is a **lymph node with blood in its sinuses.**
60
What is the lymphatic vessel status of hermal nodes?
Hermal nodes are **devoid of lymphatic vessels.**
61
Where are hermal nodes situated anatomically?
Hermal nodes are **situated along the course of blood vessels**, rather than lymphatic vessels.
62
In which species and anatomical regions are hermal nodes found?
Occurs in **ruminants**
- Located in **retroperitoneal positions along the vertebral column, jugular furrow**, and associated with **some visceral organs**
63
What structural characteristic is seen in the **medulla of hermal nodes?**
The medulla **has wide medullary sinuses that may contain blood**, and it is not typical in structure.
64
What is another term for the hemolymph node?
the hemorrhagic lymph node.
65
What fluids are received and intermixed in the sinuses of a hemolymph node?
**Blood and lymph** intermix in the sinuses of hemolymph nodes.
66
In which species and anatomical locations do hemolymph nodes occur?
Found in the **perirenal region of the sheep and goat**
Found in the **lumbar area of the ox**
67
What is the spleen in terms of lymphatic tissue mass and essentiality to life?
The **spleen is the largest mass of lymphatic tissue** in the body, but it is **not essential for life.**
68
What is the composition of the splenic capsule?
The **splenic capsule** consists of:
- dense white fibrous connective tissue (DWFCT) with collagen,
- elastic fibers, and
- some smooth muscle covered by a thin layer of mesothelium.
69
In which species is the spleen's capsule thickest?
The **horse** has the thickest capsule.
70
What is the relationship between splenic trabeculae and the capsule?
The trabeculae are connected to the capsule.
71
Does the spleen possess afferent lymphatic vessels?
No, the spleen has **no afferent lymphatic vessels.**
72
What are the two components of the splenic parenchyma?
* White pulp
* Red pulp
73
What structures compose the white pulp of the spleen?
* **Dense lymphatic tissue called splenic corpuscles** (lymph nodules)
* **Periarterial sheaths of lymphocytes**
74
What structure is found in the center or paracenter of the white pulp, and what is its common misnomer?
An **arteriole** **occupies the central or paracentral position**, and is **mistakenly called the central artery.**
75
What influences the presence of nodules in the white pulp?
The degree of activity of the gland, similar to lymph nodes.
76
What is the structural form of the red pulp in the spleen?
The **red pulp** is in the form of splenic cords (**Billroth’s cords**) separated by sinuses.
77
What are splenic cords made of?
| Red Pulp IN Spleen
Reticular fibers
Reticular cells
Erythrocytes
Macrophages
Lymphocytes
Plasma cells
Other leukocytes
78
What are splenic sinuses, and how are they structured?
Wide vascular channels
Lined with endothelial cells
Supported by reticular fibers
79
What is the functional role of **contractile microfilaments in splenic endothelial cells?**
| Red Pulp (Context: Circulatory and Phagocytic Zone of the Spleen)
They help **stabilize the endothelial cells** and **form slits or gaps** upon contraction.
80
What do the gaps between endothelial cells allow?
| Red Pulp
They allow erythrocytes to pass from the splenic cords into the sinus lumen.
81
Enumerate the **two types of red pulp found in mammalian spleens** and their representative species.
a. **Sinusal type** – with sinuses *(e.g., dog, man, rat)*
b. **Non-sinusal type** – without sinuses but with venules *(e.g., cat, ruminant)*
82
Enumerate the seven functions of the spleen.
Blood cell formation
Hemoglobin and iron metabolism
Red blood cell destruction in red pulp
Blood filtration
Blood storage
Phagocytosis
Immune response through production of B-lymphocytes
83
What type of spleen is found in humans, and what are its characteristics?
Defensive type
Few trabeculae and muscle fibers
Abundant lymphatic tissue
84
What type of spleen is *found in horses, dogs, and cats*, and what are its characteristics?
* Storage type
* Many trabeculae and smooth muscle fibers
* Relatively large and less white pulp
85
What type of spleen is **found in ruminants and swine**, and what are its characteristics?
**Intermediate type**
**Between defensive and storage types**
86
What type of connective tissue forms the capsule of the thymus?
The capsule is made of loose connective tissue.
87
What structures arise from the thymic capsule, and what is their function?
Septa arise from the capsule and subdivide the organ into lobules.
88
What type of tissue comprises the thymic stroma?
The stroma is composed of **reticular connective tissue.**
89
How is the **parenchyma of the thymus** organized?
The parenchyma is composed of two distinct regions: **the cortex and the medulla.**
90
What cell types and fibers are found in the cortex of the thymus?
1. **Small lymphocytes** (thymocytes)
1. **Epithelial-reticular cells**
1. **Reticular fiber stroma**
91
How does the **thymic medulla differ from the cortex** in cell composition?
| Difference nila
The **medulla has more reticular cells** and fibers, but **fewer thymocytes.**
92
What is a distinctive histological feature found in the thymic medulla?
The presence of thymic (Hassal’s) corpuscles.
| **Hassal's Corpuscles**
93
They are acidophilic bodies made up of concentric whorls of cells, probably reticular cells in various stages of degenerative change.
Thymic (Hassal’s) corpuscles
94
Does the thymus possess afferent lymph vessels?
No, it has **no afferent lymph vessels.**
95
What type of lymphatic vessel is present in the thymus?
The thymus contains **only efferent lymph vessels.**
96
What is the origin of epithelial-reticular cells in the thymus?
They are **endodermally derived.**
97
How are epithelial-reticular cells structurally connected to each other?
They are attached to each other through processes.
98
What is the role of epithelial-reticular cells **surrounding blood vessels in the thymus?**
form the blood-thymus barrier.
99
What are the **two functions of the blood-thymus barrier?**
* Prevents entry of antigens into the thymus
* Prevents sensitization of thymocytes
100
Enumerate **three major functions** of the thymus.
Answer:
1. Produces lymphocytes (thymocytes) which populate secondary lymphatic organs such as lymph nodes, spleen, tonsils, and bone marrow.
1. Produces hormones such as thymosin and thymopoietin I and II that influence the development of progenitor cells into T-lymphocytes.
1. Involved in immune response.
101
What happens to the thymus **after puberty?**
It **involutes** and is eventually **replaced by adipose cells.**
102
Which **bird groups possess lymph nodes?**
Only swamp, sea, and shore birds possess lymph nodes.
103
What is the characteristic lymphatic feature **in galliform and columbiform birds?**
The **presence of solitary nodules in the digestive tract**, serous membranes, and skin.
104
What are the **two major divisions of the avian lymphatic system?**
Primary lymphoid system
Secondary lymphoid system
105
What are the components of the avian primary lymphoid system?
Bursa of Fabricius
Thymus
106
What are the components of the ***avian secondary lymphoid system?***
Spleen
Harderian gland
Caecal tonsil
Diffuse unencapsulated lymphatic nodules in the digestive tube (especially small and large intestines)
107
In what animals is the Bursa of Fabricius found?
It is present only in birds.
108
What is the **anatomical structure** of the bursa of Fabricius?
It is a **blind sac that opens into the cloaca**.
109
What are** two other names** for the bursa of Fabricius?
1. Cloacal tonsil
1. Cloacal thymus
110
What kind of **epithelium lines the bursal folds?**
* Simple columnar or
* Pseudostratified columnar epithelium
111
Where are **lymphatic nodules** **found in the bursa of Fabricius?**
They are found **between the folds of the bursal wall.**
112
What structures do the lymphatic nodules in the bursa **resemble**?
they resemble **follicle-like structures.**
113
What are the germinal centers of the bursa called?
They are referred to as **medullary structures.**
114
What are the **darker coronal regions** in the bursa called?
cortical areas
115
Despite structural resemblance to tonsils and thymus, what is the specific function of the bursa of Fabricius?
It functions in the **production of B-lymphocytes.**
116
At what age does the bursa of Fabricius reach its **maximum size?**
At **4 to 5** months of age.
117
What happens to the **bursa at 10 months of age?**
It is **reduced to a tiny saccule** and eventually disappears entirely.
118
How does the structure of the avian thymus compare to mammals?
It is **similar in structure** to the thymus in mammals.
119
What happens to the **thymus in birds** **between 13–17 months of age?**
Only traces of it are recognizable due to **involution.**
120
What **type of lymphocytes** are produced by the avian thymus?
It produces **T-lymphocytes.**
121
describe the **physical appearance** of the avian spleen.
round, small, and brownish-red in color.
122
How does the histology of the avian spleen compare to mammals?
same as in mammals.
123
In **which animal**s is the **Harderian gland considered a lymphatic organ?**
lymphatic organ present **only in birds.**
124
Where is the **Harderian gland** located in birds?
It is found **under the eyes.**
