Lymphatic System

Question 1

What are the main lymphocyte cells?

Answer 1

• T cells: cellular adaptive immunity
  ~75% circulating lymphocytes
• B cells: humoral adaptive immunity
• Natural Killer cells: innate (nonspecific) immunity
  Induce apoptosis of virus- or cancer-infected cells

Question 2

Name the auxiliary immune cells

Answer 2

MACROPHAGES

DENDRITIC CELLS =
antigen presenting cells

Question 3

What are the functions of macrophages?

Answer 3

Widely distributed throughout lymphoid organs

Functions include:
Phagocytosis
Enhancement of inflammatory response
Presentation of antigens to T cells

Question 4

What are the functions of dendritic cells?

Answer 4

Mobile, antigen-presenting cells

Possess wispy cellular extensions for antigen capture & phagocytosis

Migrate to lymph nodes and present antigens to naïve lymphocytes

Question 5

What are the subtypes of T cells

Answer 5

• Subtypes:
  
  • cytotoxic,
  • helper,
  • regulatory T cells

Question 6

What are the subtypes of B cells

Answer 6

• plasma: Antibodies

- memory cells:

Question 7

What are supporting cells?

Answer 7

• Reticular cells: fibroblast-like cells that produce a connective tissue stroma (L. ‘bed covering’) for lymphoid tissues and organs

Question 8

What is the normal ratio of cells?

Answer 8

500 RBCs:
30 platelets:
1 WBC

Question 9

Whats the function of Lymphoid tissue?

Answer 9

Proliferation site for lymphocytes

Surveillance point for lymphocytes & macrophages

Question 10

What are the types of Lymphoid tissue?

Answer 10

Diffuse lymphoid tissue: Loose arrangement of lymphoid cells & reticular fibres

Lymphoid follicles:Solid, spherical bodies consisting of tightly packed lymphoid cells & reticular fibres.

Question 11

What are the primary Lymphoid organs?

Answer 11

Sites of B & T cell maturation
Red bone marrow, thymus

“preschool”

Question 12

What happens at the secondary Lymphoid organs?

Answer 12

Where mature lymphocytes first encounter their antigens and become activated

Question 13

What are the secondary Lymphoid organs?

Answer 13

Lymph nodes*> filtering, 
spleen, 
tonsils, 
appendix, 
intestinal follicles

Question 14

What is the gross structure of lymph nodes?

Answer 14

Dense fibrous capsule
Compartmentalised by trabeculae
Stroma of reticular (internal network - like skeleton)
connective tissue

Question 15

Whats the functions lymph nodes?

Answer 15

House lymphocytes AND macrophages

Site of immune system activation

Filtering of lymph (microorganisms, debris)

Question 16

What is the histology of the lymph node?

Answer 16

Cortex: germ cells (B cells) & T cells transit

Medulla: medullary cords

Lymph sinuses: lymphatic channels

Question 17

What is the Nodal circulation process?

Answer 17

Lymph flows into the node through numerous afferent lymph vessels (convex side)

Lymph moves through the subcapsular sinus towards the medulla

Flow occurs through medullary sinuses

Exits via efferent lymph vessels

Question 18

What is the structure of the spleen

Answer 18

Largest lymphoid organ, size of a clenched fist
Dark red,
highly vascular,
ovoid organ
encapsulated by fibroelastic connective tissue + smooth m. cells

Question 19

What are the surfaces of the spleen?

Answer 19

Diaphragmatic surface:

• outer,
• convex

Visceral surface:

• inner, concave
• Impressions from stomach, kidney, colon, pancreas

Question 20

What are the peritoneal ligaments of the spleen ?

Answer 20

gastrosplenic

splenorenal ligaments

Question 21

What is the location and function of the spleen?

Answer 21

LOCATION:
Lt Hypochrondriac region, LUQ behind stomach
Roughly deep to Ribs 9 - 11 ribs (separated by diaphragm)
Rests on the Lt colic flexure

Function:

• immunity
• blood filter
• reservoir
• recycle iron from RBC
• erythropoiesis in foetus

Question 22

What is the histology of the spleen?

Answer 22

White pulp: site of immune functions
Mostly lymphocytes suspended on reticular fibres

Red pulp: where senescent RBC and bloodborne pathogens are destroyed

Question 23

What is the vascular supply to the spleen ?

Answer 23

Arterial:
Splenic a.: largest branch of the celiac trunk

Splenic a. runs a tortuous course along the superior border of the pancreas

Venous:
Splenic V.

Question 24

What is the lymph and neural supply to the spleen?

Answer 24

Lymph nodes in the splenic hilum

Sympathetic: abdominopelvic splanchnic nerves via the celiac ganglion (T6-T10)

Parasympathetic – CNX Vagus

visceral afferent supply to spleen

Question 25

What are microbiome?

Answer 25

Make 90% of microbes in human body and are external.

Microbiome: a collection of microbial genomes
Microbiota: a collection of microbes

Question 26

What is Dysbiosis?

Answer 26

A shift on healthy microbiome to a disease-associated state