Lymphoid Tissue

Question 1

Neutrophils

What is their function?

Physical description?

What does polymorphonuclear mean?

Answer 1

Recognize & bind to Bacteria, foreign organisms, and infectious agents; Acute inflammation & tissue injury

Multi-lobed nucleus with lack of cytoplasmic staining

Varying shapes of nucleus

Question 2

Eosinophils

Description of nucleus and cytoplasm?

What would cause increased counts?

Answer 2

• ​Bi-Lobed nuclei, Cytoplasm stains pink/red
• Increased counts with allergies and/or parasitic infection

Question 3

Basophils

Nucleus?

Answer 3

• Lobed nucleus usually obscured by granules

Question 4

Lymphocytes: Functional Cells of Immune System

Description of nucleus & cytoplasm

Answer 4

• Spherical nucleus w/ thin, pale blue rim of cytoplasm

Question 5

Monocytes: Largest WBC

Description of nucleus?

Answer 5

• Heart/Kidney shaped nucleus

Question 6

Primary and Secondary Structures

Functions

Answer 6

• Primary: Thymus & Red Bone Marrow
  
  • Produces lymphocytes to recognize Ags
• Secondary: Diffuse lymphoid tissue
  
  • Lymphocytes activated in response to antigens

Question 7

Diffuse Lymphoid Tissue

Capsule status

Location

Function

Answer 7

Non encapsulated

Lamina Propria (GI, Genitourinary, Respiratory) - Subepithelial tissue

Intercept Ags and initiate immune response

Question 8

Nodular Lymphoid Tissue

Lymphatic nodules

Primary nodule

Answer 8

Discrete concentration of lymphocytes (non-encapsulated)

Consist of small lymphocytes without germinal center

Question 9

Secondary Nodule/Follicle

Germinal Center

Mantle Zone (Corona)

Answer 9

Activated primary nodules exposed to Ag

Central region of nodule (lightly stained)

Outer ring of small lymphocytes encircling germinal center

Question 10

Aggregated Lymphoid Tissue

Locations?

Answer 10

Tonsils

Peyer’s Patches

Veriform Appendix

Mucosa-Associated Lymphatic Tissue (MALT)

Question 11

Tonsils

Location

Answer 11

Mucosa of posterior oral cavity, oropharynx, nasopharynx

Question 12

Palatine Tonsil

Lined with what type of epithelium?

What are the deep invaginations called?

What acts as partial capsule?

Answer 12

Nonkeratinized stratified squamous epithelium

Tonsillar crypts

Dense CT

Question 13

Pharyngeal Tonsil

Location?

Covered with what type of epithelium?

Capsule and crypt status?

Answer 13

Posterior wall of nasopharynx

Pseudostratified columnar ciliated epithelium

Thin underlying capsule, no crypts

Question 14

Lingual Tonsil

Location?

Covered with what type of epithelium?

Possess what structures not present in pharyngeal tonsils?

Capsule status?

Answer 14

Base of tongue

Stratified squamous epithelium

Germinal centers and varying number of crypts

No capsule

Question 15

Peyer’s Patches

Location

Associated with what?

Covered with what epithelium?

Answer 15

SI (Ileum)

Intestinal villi

Simple columnar epithelium with goblet cells

Question 16

Veriform Appendix

Lamina propria infiltrated with what?

Type of epithelium?

Characterized by what?

Answer 16

Lymphocytes

Simple columnar epithelium with goblet cells

Crypts but no villi

Question 17

Mucosa-Associated Lymphoid Tissue (MALT)

Structure?

Lumen open to what?

Answer 17

Single/clusters of lymphoid nodules

External environment

Question 18

Lymph Nodes

Structure?

Comprised of what tissue?

Locations

Answer 18

Encapsulated structures positioned along lymphatic vessels

Reticular tissue

Axilla, Neck Vasculature, Thorax, Inguinal

Question 19

Lymph Nodes

Parenchyma

Stroma

Superficial Cortex

Deep (Para) Cortex

Medulla

Lymph Flow

Hilum

Answer 19

Cortex + Medulla

Supportive CT

Receives lymp from afferent lymphatic vessels

Region between cortex and medulla

Sinuses converge at efferent lymphatic vessel

Exit for efferent lymphatic and exit/entry for neurovasculature

Afferent –> Cortex –> Paracortex –> Medulla –> Efferent

Exit for efferent lymphatic and exit/entry for neurovasculature

Question 20

Lymph Node Cortex

Superficial Cortex: what is located here?

Deep Cortex

Answer 20

• Superficial
  
  • Location of lymphatic nodules (1 & 2)
  • Immune cells suspended on reticular fibers
• Deep
  
  • Free of nodules and high in T-cell counts

Question 21

Reticular Meshwork

Cells of reticular meshwork?

Answer 21

Reticular cells

Dendritic cells (APCs) and Follicular DCs

Macrophages

Question 22

What are High Endothelial Venules?

What do they facilitate?

What leave circulation through these?

Answer 22

Postcapillary venules lined by cuboidal or columnar endothelial cells

Movement of lymphocytes from circulation and into lymph node via diapedesis

B cells and T cells

Question 23

Lymph Node Medulla

Inner part of the LN, consisting of cords of lymphatic tissue called _ that are separated by _

What serves as the framework of the parenchyma?

Converge where?

Answer 23

Medullary cords; Medullary sinuses

Network of reticular cells and fibers traversing the medullary cords and sinuses

Near the hilum and drain into efferent lymphatic vessels

Question 24

Thymus

What invade the tissue to proliferate?

What is involution?

Answer 24

Lymphoblasts

Decreased activity of thymus and becomes filled with adipose tissue over time

Question 25

**Thymus** What surrounds the thymus? What is the purpose of trabeculae? What does it lack?

Answer 25

Thin CT capsule with trabeculae extending into the parenchyma Establish domains (thymic lobules) Lymphoid nodules and germinal centers

Question 26

**Thymic Cortex** Site for what process? Appearance? What cells provide framework for T-Cell development?

Answer 26

T-Lymphocyte maturation Markedly basophilic and packed with thymocytes Epithelioreticular cells

Question 27

**Cortical Epithelial Reticular Cells** Type 1 Type 2 Type 3

Answer 27

Boundary of cortex and capsule (between cortical parenchyma and trabeculae) Located within cortex and compartmentalize into isolated areas for developing T cells (express MHC I and MHC II) Located at boundary of cortex and medulla (express MHC I and MHC II)

Question 28

**Thymic Medulla** Distinguishing feature of medulla? Houses what cells?

Answer 28

Thymic corpuscles Mature T cells migrating from cortex (enter postcapillary venules to exit Thymus)

Question 29

**Medullary Epithelioreticular Cells** Type IV Type V Type VI

Answer 29

Located near Type III cells and creates barrier at corticomedullary junction with type III cells Located throughout medulla and provides cellular framework Forms Thymic Corpuscles and produces IL-4 and IL-7 (thymic differentiation and T-cell education)

Question 30

**Blood Thymus Barrier** Function? What constitutes the barrier between T cells and lumen of cortical blood vessels?

Answer 30

Protect developing lymphocytes from exposure to Ags Endothelium lining capillary wall --\> Macrophages within perivascular CT --\> Type I Epithelioreticular cells surround capillary wall

Question 31

**Spleen** Capsule status? White pulp Red pulp

Answer 31

Dense CT capsule with trabeculae containing myofibroblasts T-cells, B-cells and macrophages Venous supply, RBCs, platelets, macrophages, plasma cells

Question 32

**White Pulp** Components

Answer 32

Periarteriolar lymphoid sheaths (PALS): T cells surrounding central arteriole Corona/Mantle Zone: small lymphocytes surrounding germinal center Marginal Zone: surround mantle zone, blend of lymphocytes that span white --\> red pulp

Question 33

**Red Pulp** Function? Composition

Answer 33

Blood filtration and RBC turnover Splenic sinusoids and splenic cords (reticular tissue rich in macrophages and lymphocytes)

Question 34

**Red Pulp** What lines sinusoids?

Answer 34

**Stave cells**: specialized endothelial cells separating healthy and unhealthy RBCs

Question 35

Splenic Blood Flow

Answer 35

Celiac trunk --\> Splenic a. --\> Trabecular aa. --\> Central arteriole/PALS --\> White Pulp --\> Penicillar aa. --\> Splenic sinuses --\> Splenic cords