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Learning objectives

  • Describe the various physical barriers and mechanical defenses that protect the human body against infection and disease
  • Describe the role of microbiota as a first-line defense against infection and disease

Nonspecific innate immunity can be characterized as a multifaceted system of defenses that targets invading pathogens in a nonspecific manner. In this chapter, we have divided the numerous defenses that make up this system into three categories: physical defenses, chemical defenses, and cellular defenses. However, it is important to keep in mind that these defenses do not function independently, and the categories often overlap. [link] provides an overview of the nonspecific defenses discussed in this chapter.

Overview of Nonspecific Innate Immune Defenses
Physical defenses Physical barriers
Mechanical defenses
Microbiome
Chemical defenses Chemicals and enzymes in body fluids
Antimicrobial peptides
Plasma protein mediators
Cytokines
Inflammation-eliciting mediators
Cellular defenses Granulocytes
Agranulocytes

Physical defenses provide the body’s most basic form of nonspecific defense. They include physical barriers to microbes, such as the skin and mucous membranes, as well as mechanical defenses that physically remove microbes and debris from areas of the body where they might cause harm or infection. In addition, the microbiome provides a measure of physical protection against disease, as microbes of the normal microbiota compete with pathogens for nutrients and cellular binding sites necessary to cause infection.

Physical barriers

Physical barriers play an important role in preventing microbes from reaching tissues that are susceptible to infection. At the cellular level, barriers consist of cells that are tightly joined to prevent invaders from crossing through to deeper tissue. For example, the endothelial cells that line blood vessels have very tight cell-to-cell junctions, blocking microbes from gaining access to the bloodstream. Cell junctions are generally composed of cell membrane proteins that may connect with the extracellular matrix or with complementary proteins from neighboring cells. Tissues in various parts of the body have different types of cell junctions . These include tight junctions, desmosomes, and gap junctions, as illustrated in [link] . Invading microorganisms may attempt to break down these substances chemically, using enzymes such as proteases that can cause structural damage to create a point of entry for pathogens.

Tight junctions – two membranes connected with many spot welds in multiple lines. Desmosomes – two membranes with long strands weaving them together. Gap junctions – two membranes with a few spot welds each of which has a pore in the center.
There are multiple types of cell junctions in human tissue, three of which are shown here. Tight junctions rivet two adjacent cells together, preventing or limiting material exchange through the spaces between them. Desmosomes have intermediate fibers that act like shoelaces, tying two cells together, allowing small materials to pass through the resulting spaces. Gap junctions are channels between two cells that permit their communication via signals. (credit: modification of work by Mariana Ruiz Villareal)

The skin barrier

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 ( [link] ).

Questions & Answers

what is gram staining
Nankya Reply
microbiology?
Bekka
Tell u only
Balu
It's technique to differentiate bacterial species.The method is discovered by Hans Christian Gram. The bacteria is differentiated as gram positive and gram negative on the basis of peptidoglycan layer which is present in cell wall. The gram positive have peptidoglycan layer.
shamali
What is study of morphology ? and it's classification
Maryam
taxonomy
Kamaluddeen
what makes a student to forget what he or she has been taught with easily and how can he or she cope up with it
Samson Reply
to be in touch with subject will help to cope up with the learning life long and also interest matters for subject
shriya
Constant review. And don't worry if you do forget something you always have the option to study it again. Each time you study a certain topic the more it make sense and the more it becomes something natural rather than brute memorization.
Abdi
the cause are many 1.lack of interest . 2. poor attitude to the subject. how can he cope up 1. falling in love with the subject . 2. making it part of you at all times and having determination
Ikilai
understanding the concept and relating whatever course of study with something in his/her day to day activities (i.e in which you are more conversant with in your life).
Kamaluddeen
how many types of cross matching method
umesh
which disease is caused by vicera zoster virus
Timaka Reply
chicken pox
Osuoha
Patients with disseminated herpes zostermay present with severe abdominal pain that results from visceral involvement of varicella-zoster-virus infection. In immunocompetent individuals herpes zoster usually is a localised illness, affecting the skin of one or two adjacent dermatomes.
Kamaluddeen
Actually, it is severe abdominal pain thanks
Osuoha
what causes inflammation of the lung?
Samson
what causes the fungi infection of the vigina
Estar Reply
what causes the fungi infection of the vagina?
Estar
poor hygiene of the area and unprotected sex with infected partner
Kamaluddeen
poor hygiene,some times having sex with infected person or when normal flora enters in the vagina
Ikilai
unprotected sex and poor hygiene are the major but keep in mind that there are some other minor causes also
Samson
what brings about dirt in blood
Sumaiyah Reply
So many factors might be the cause viz. Defects of blood capillaries and certain organs like the liver, the kidneys e.t.c
MOHAMMED
with the above any infection of the body easily enters the bloodstream.
MOHAMMED
there may be fevers which cause septicemia
Ikilai
even taking drug, and eating junk foods .
Ikilai
drinking contaminated water and taking drugs which contains chemical and afterwards they gets absorbed in yo the blood stream
Samson
write a essay about gene library's
anaparthi Reply
Structure of bacteria
Maggy Reply
Outline the classification of viruses according to morphology, nucleic acid, type of diseases, antigenic reaction
chilufya Reply
who is da father of microbiology
Mukomya Reply
Lucie pasture
Felicity
Father of microbiology is Anton von Leuuwenhoek
Anshika
mean Luice pasture the father of microbiology
Felicity
Luice pasture is the father of industrial microbiology
Anshika
who is the father of surgery
Talemwa
father of surgery is Sushruta
Agyekum
sushruta is the father of surgery
Ven.phumie
he Anthony van Lee wen hock
Ikilai
who is the father of medical microbiology
Naveen
he is Anthony van Lee wen hock
Ikilai
Anthony van Lee wen hook
Kamaluddeen
where would we be without microbes
Jessa Reply
nowhere because our body alone also contain billions of microbes.
Edward
in the dreams
Abid
Bangladeshi people's body contain thrice the amount of microbes than regular people.
IamTheMegaExploder
sure?
Kamaluddeen
yah
Kamran
why it was like that
Mمهazn
no where
Mukomya
cocci which are arranged in pairs are called?
umesh
diplococci
vijaya
Cocci are bacterias
Anshika
fimbriae is an organ of ?
umesh
what is the choma like vrius?
PRALHAD
Vibrio cholarea
Kamaluddeen
outline the classification of viruses
chilufya
Fimbriae z an organ of bacteria
Maggy
Antoni van Leeuwenhoek, the father of micro biology
Yang
concept of primary& secondary metabolism
yamini Reply
who is the father of microbiology
imran Reply
Louis pasture is a father of modern microbiology
Bharat
anton van leuwen kook
Kavi
anton van is father of ancient microbiolgy
Bharat
Antonie van Leeuwenhoek
Bharat
g
Red
Louis pasture
Atar
what can cause serious stomachache after treating ulcer and typhoid and symptoms persist to leave.
Ven.phumie
Anthony van
Nankya
what is lumbar puncture
amulya Reply
To get the cerespinalfluid
Alphonsia
what is the role of glutamic acid in consideration to ulcer healin
Hyrin Reply
what is role of glutamic acid in peptidoglycan
Pooja Reply
what's the name of Greek word were nursing came from?
Joyce
Take care.
Alphonsia
thanks
Joyce
glutamic acid helps in synthesis of protein
Ganesh
i want some explantion on gram staining
Nankya
gram (+ve) or gram(-ve)
Atar
gram stain is defined as identification methods for bacteria
vijaya
Gram stain or Gram staining, also called Gram's method, is a method of staining used to distinguish and classify bacterial species into two large groups (gram-positive and gram-negative). The name comes from the Danish bacteriologist Hans Christian Gram, who developed the technique.
Atar
Practice MCQ 3

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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