Name : Abby Yong I.D. : 14WAR03484Group : RBS2 Group 2Date : 30 September 2015

Title : Observation of different cell types in the human body and the lymphatic structures

and organs.

Aim:

1. To differentiate the various cell types in the human blood

2. To understand the histology and organization of lymphoid organs namely the thymus,

spleen and lymph nodes.

3. To understand the histology and organization of lymphoid tissues, in particular those

that are involved with the gastrointestinal tract.

Introduction

In this experiment, fresh stains of human blood samples were made and observed to

identify the presence of various cells in the immune system. The immune system has

specific cells whose job is to recognize pathogen-associated molecular patterns.Cells of

the immune system are divided into myeloid cells and also lymphoid cells. Myeloid cells

are either granulocytic or monocytic. Granulocytic cells are white blood cells such as

neutrophils, basophils and eosinophils. Monocytic cells are macrophages, Kupffer cells

and dendritic cells. Lymphoid cells on the other hand are T-cells, B-cells and natural

killer cells. When a pathogen enters the body, cells in the blood and lymph detect the

specific pathogen-associated molecular patterns on the pathogen's surface. These

pathogen-associated molecular patterns allow the immune system to recognize "self"

from "other" so as not to destroy the host. The lymphatic system includes a system of

lymphatic capillaries, vessels, nodes, and ducts that collects and transports lymph. The

lymphatic system is important for maintaining the body’s fluid balance, and it also works

along with the rest of the immune system to fight infections. The lymphoid organs assist

the lymphatic system. They include the thymus, spleen, tonsils, and appendix. Some

lymphatic tissue similar to the tonsils is also located in the digestive tract and these are

called gut associated lymphoid tissue (GALT). An example of these tissue is the Peyer’s

patches found in the small intestine.

Method

I. Observation of different cell types in the human blood

A finger is pricked with and lancet and a drop of blood is dripped onto a glass slide.

Leishmann stain is then added to the blood drop and allowed to sit for 1-2 minutes.

Distilled water which is equal to twice the amount of stain added is then dripped onto the

slide. This is then allowed to sit for a further 10-15 minutes.

The stain is then washed off with more distilled water and is then viewed under the

microscope.

II. Observation of lymphatic structure and organs

Prepared slides of various lymphoid tissues, namely the thymus, spleen, lymph node and

Peyer’s patches are observed under the microscope.

Results

Picture 1.1: Lymph Node at

magnification

X100

Picture 2.1: Thymus gland at magnification

X100

Picture 3.1 : Small Intestine at magnification X100

Picture 4.1 : Spleen at magnification X100

Picture 5.1 : Blood smear at magnification X100

Discussion

The human blood sample consists of various cells and among them are red blood cells,

white blood cells and blood platelets. However, it is specifically the white blood cells that

are directly involved in the immune system. There are five main types of white blood

cells. They are: Neutrophils, Eosinophils, Basophils, Lymphocytes, and Monocytes.

Neutrophils, eosinophils and basophils are also called granulocytes because they have

granules in their cells that contain digestive enzymes.

Cell Structure Function

Neutrophils Lobed-nucleus and known as

a granulocyte

Engulfs bacteria via a process known

as phagocytosis. Their nucleus also

contain antimicrobial effectors which

are proteins that can kill microbes in

various different ways.

EosinophilsLobed-nucleus and known as

a granulocyte

Kills parasites and plays a role in

allergic reactions

BasophilsA granulocyte with a two-

lobed nucleus

Releases histamine and heparin

which are hormones involved in

allergy when activated.

Lymphocytes Round and agranulocytic Lymphocytes function to make T-

cells, B-cells and NK cells

MonocytesAgranulocytic and has

kidney-shaped nucleus

Matures into macrophages which are

phagocytotic

Lymphocytes function to produce B-cells, T-cells and NK cells. Each of these have

specific functions respectively.

Cell Function

B-cells It regulates construction of an antigen receptor.

It ensures the cell specificity.

It helps in exporting all required cells in the periphery.

It helps in antibody production.

It helps rearrangement of their antigen receptors.

T-cells

Divided into T-helper cells and suppressor cells

1. Helper cells assist other white blood cells in

immunologic processes, including maturation of B

cells into plasma cells and memory B cells, and

activation of cytotoxic T cells and macrophages.

2. Suppressor cells shut down T cell-mediated

immunity toward the end of an immune reaction and

to suppress autoreactive T cells that escaped the

process of negative selection in the thymus.

NK cells

Natural killer cells play a cytotoxic role in the human

immune system. Its main function is in granule mediated

cell apoptosis.

Several other organs in the human body also play large roles in the immune system.

Those that were observed in the experiment were cells from the thymus, spleen, lymph

node and also the small intestine.

Organ Structure Function

Thymus

The thymus is a two-lobed

structure which consists of

the cortex and medulla.

The cells in the medulla

form nest-like structures

known as the Hassall’s

corpuscle.

The function of the thymus is to receive

immature T cells that are produced in the

red bone marrow and train them into

functional, mature T cells that attack only

foreign cells. T cells first reside within the

cortex of the thymus where they come in

contact with epithelial cells presenting

various antigens. The immature T cells

that respond to the antigens corresponding

to foreign cells are selected to survive,

mature, and migrate to the medulla while

the rest die via apoptosis and are cleaned

up by macrophages.[1]

Spleen

A brown, flat, oval-shaped

lymphatic organ that is

divided into the red and

white pulp.

It mainly acts as a filter for purifying the

blood, removing microbes and worn out or

damaged red blood cells. It is also an

important organ in the immune system,

producing the white blood cells that fight

infection and synthesize antibodies.[2]

Small

intestine;

Peyer’s

Patches

Egg-shaped lymphatic

tissue nodules that are

similar to lymph nodes in

structure, found in the

ileum of the small

intestine.

Peyer’s patches analyze and respond to

pathogenic microbes in the ileum.

Antigens from microbes in the gut are

absorbed via endocytosis by microfold

cells lining the surface of each Peyer’s

patch. These antigens are passed on to the

lymphoid tissue, where they are absorbed

by macrophages and presented to T

lymphocytes and B lymphocytes. When

presented with dangerous pathogenic

antigens, lymphocytes trigger the immune

response by producing pathogen-specific

antibodies; turning into pathogen-killing

cytotoxic T lymphocytes; and migrating

through lymphatic vessels to lymph nodes

to alert the other cells of the immune

system. The body then prepares a full

body-wide immune response to the

pathogen before it is able to spread beyond

the intestines.[3]

Lymph node

Small bean-shaped glands

that occur along the larger

lymphatic vessels.

The function of all lymph nodes is the

production of lymphocytes, which help

defend the body against microorganisms

and against harmful foreign particles and

debris from lymph before it is returned to

the blood stream. [4]

Questions

1)

Conclusion

The various organs in the immune system work hand-in-hand to help fight against

infections and protect the body from harm.

References

[1] Taylor, T 2013, Thymus Gland, viewed 7 October 2015,

<http://www.innerbody.com/image_endoov/lymp04-new.html>.

[2] Mandal, A 2014, Functions of the spleen, viewed 7 October 2015, <http://www.news-

medical.net/health/What-Does-the-Spleen-Do.aspx>.

[3] Taylor, T 2013, Peyer’s Patches, viewed 7 October 2015,

<http://www.innerbody.com/anatomy/immune-lymphatic/peyers-patches>.

[4] Taylor, T 2014, Lymph node, viewed 7 October 2015,

<http://www.innerbody.com/image_chest1/lymp05.html>.