functions of skin, mucous membrane, types of immunity, phagocytosis

Date:6/22/2021 www. qadricohs.edu.pk FB Page: Qadri College of Health Sciences, Karachi, Sindh, Pakistan. 1
QADRI COLLEGE OF HEALTH SCIENCES, KARACHI
U-3, 3 OF
“DEFENSE MECHANISMS OF THE BODY”
By: Aftab H. Abbasi
RN, DCHN, BSN, MA, LL.B
Lecturer Nursing
Qadri College of Health Sciences Karachi

“DEFENSE MECHANISM OF THE BODY”
- This unit focuses on the resistance of the
body which microorganism’s encounter
where they enter in the human body.
- This unit highlights the importance of the
resistance or defense of the body which
will help learners in understanding that
why infection occurs sometimes and not
always.

At the completion of this unit learners will
be able to:
1- Explain the role of good health in protection against the microbial
infection.
2- Define Resistance and Susceptibility.
3- Define Nonspecific Resistance.
4- Describe the role of the skin and mucous membrane in nonspecific
Resistance.
5- Explain the process of Phagocytosis.
6- Define the Specific Resistance, Innate Resistance and Immunity.
7- Explain four types of acquired Immunity.

At the completion of this unit learners will be
able to:
8- Differentiate between humoral and cell mediated immunity.
9- Define Antigens, happen and antibodies.
10- List the five classes of antibodies and their functions.
11- Explain the role of memory, tolerance and specificity in immunity.
12- Distinguish between primary and secondary immune response.
13- Define Hypersensitivity.
14- Differentiate between i.e. delayed and immediate Hypersensitivity.

2- Resistance and Susceptibility.

DEFINITION OF RESISTANCE:
However, the host can also
defend itself by limiting the
damage that is caused by
the infection.
Resistance is defined as the
ability to limit pathogen
burden, whereas tolerance
is defined as the ability to
limit the health impact of a
given pathogen burden.

DEFINITON OF SUSCEPTIBILITY:
Disease Susceptibility is a condition in
which the individual is at a risk of getting
infected by a disease.
Some diseases that are thought to have
an inherited or genetic component are
seen to cluster in families and affect
more than one generation, but without a
clear pattern of inheritance as for
monogenic diseases.

Susceptibility- the quality or state of
being susceptible especially :
lack of ability to resist some extraneous agent
(such as a pathogen or drug).
A Susceptible Host:
Is a person who can become infected by the
infectious agent.
Susceptible host include:
- Patients
- Health care professional
- Visitor from the community.

4- Role of the skin and mucous membrane in nonspecific Resistance.
Skin- main barrier which prevents entry
of the micro-organisms.
One of the body’s most important physical
barriers is the skin barrier, which is
composed of three layers of closely packed
cells. The thin upper layer is called the
epidermis. A second, thicker layer, called
the dermis, contains hair follicles, sweat
glands, nerves, and blood vessels. A layer
of fatty tissue called the hypodermis lies
beneath the dermis and contains blood and
lymph vessels.

The topmost layer of skin, the epidermis, consists of
cells that are packed with keratin. These dead cells
remain as a tightly connected, dense layer of protein-
filled cell husks on the surface of the skin. The keratin
makes the skin’s surface mechanically tough and
resistant to degradation by bacterial enzymes.
Fatty acids on the skin’s surface create a dry, salty, and
acidic environment that inhibits the growth of some
microbes and is highly resistant to breakdown by
bacterial enzymes. In addition, the dead cells of the
epidermis are frequently shed, along with any microbes
that may be clinging to them. Shed skin cells are
continually replaced with new cells from below,
providing a new barrier that will soon be shed in the
same way.

Infections can occur when the skin barrier is
compromised or broken. A wound can serve
as a point of entry for opportunistic
pathogens, which can infect the skin tissue
surrounding the wound and possibly spread
to deeper tissues.
Barrier which prevents entry of microbes
into the body which comes in contact with
body.

Role of Mucous Membrane in Nonspecific Resistance:
Mucus coating- present at epithelium lining of the
respiratory, gastrointestinal and urogenital tracts
-trap microbes.
Mucous membranes provide a mechanical barrier
at body openings. They also line the respiratory,
GI, urinary, and reproductive tracts. Mucous
membranes secrete mucus, a slimy substance
that traps pathogens. The membranes also have
hair-like cilia. The cilia sweep mucus and
pathogens toward body openings where they can
be removed from the body. When you sneeze or
cough, pathogens are removed from the nose
and throat.

5- The process of Phagocytosis.
Phagocytosis:
Phagein = "to devour", kytos = "cell“,
osis = “process” (from Ancient Greek)
Phagocytosis:
Is the process of engulfment and
destruction of solid particles such as
bacteria, dead tissue and foreign particles
by the cells.

Phagocytes:
The cells performing phagocytosis are
called phagocytes.
The cell types are:
• Neutrophils
• Monocytes and
• Macrophages

Steps:
1. Margination:
Rolling and Adhesion — In margination,
leukocytes assume marginal positions in the
blood vessels.
2. Diapedesis:
Resting phagocytes are activated by
inflammatory mediators and produce surface
receptors that increase their ability to adhere
to the inner surface of capillary walls enabling
them to squeeze out of the capillary and enter
the tissue.

3. Chemotaxis:
Is the movement of phagocytes toward an
increasing concentration of some attractant
such as bacterial factors (bacterial proteins,
capsules, LPS, peptidoglycan, teichoic acids,
etc.)
4. Opsonization: (attachment stage)
Refers to the process of coating of bacteria by
the opsonins.
The opsonin coated bacteria gets attached to
the surface of phagocyte through the opsonin
receptors.

5. Engulfment stage
6. Secretion (degranulation) stage
7. Degradation stage

7- Four types of acquired Immunity.
What is acquired immunity?
Acquired immunity is immunity you develop
over your lifetime. It can come from:
- a vaccine
- exposure to an infection or disease
- another person’s antibodies (infection-
fighting immune cells)

1- Active immunity:
Active immunity is the most common type. It
develops in response to an infection or vaccination.
These methods expose your immune system to a
type of germ or pathogen (in vaccinations, just a
small amount).
Immune cells called T and B cells recognize there’s
an “invader” pathogen and activate the immune
system to fight it.
The next time the T and B immune cells encounter
that specific germ, they’ll recognize it and
immediately activate the rest of your immune
system to prevent you from getting sick.

2- Passive immunity:
Passive immunity develops after you receive antibodies from
someone or somewhere else. This type of immunity is short-
lived, because it doesn’t cause your immune system to
recognize the pathogen in the future.
There are two main types of passive immunity:
- Maternal antibodies: are antibodies that transfer from a
mother to child. This usually happens across the placenta or
through breast milk, especially in the first few days after birth.
- Immunoglobulin treatments: are antibodies that are usually
used to treat people at risk for infections, like after a
snakebite or a baby born to a mother with hepatitis B. These
antibodies are made in a lab, or come from other people or
animals.

Both natural and artificial sources of immunity can be active or passive.
3- Natural sources: aren’t specifically
given to you to boost your immunity.
Instead, they’re something you acquire by
natural means, like an infection or from your
mother during birth.
4- Artificial sources: of immunity are given
to you for a specific purpose. They include
vaccinations or immunoglobulin treatments.

https://www.healthline.com/health/acquired-immunity

By: Aftab H. Abbasi
RN, DCHN, BSN, MA, LL.B
Lecturer Nursing
Qadri College of Health Sciences Karachi

functions of skin, mucous membrane, types of immunity, phagocytosis

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to functions of skin, mucous membrane, types of immunity, phagocytosis

Similar to functions of skin, mucous membrane, types of immunity, phagocytosis (20)

Recently uploaded

Recently uploaded (20)

functions of skin, mucous membrane, types of immunity, phagocytosis