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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 rickettsia
DENNIS Reply
state the theory of spontaneous generation of micro oranisms and germ theory of disease
UKAMAKA Reply
what are the advantages of high note numerical aperture
Genius Reply
list if non flagellated pritozoa
Mepung Reply
Can someone that's understanding of the Kreb Cycle please explain & breakdown it down to me in the simplest way without giving me the dictionary version or Google version. Basically in there own words of knowledge....!
Kisha
ok
lucas
please can someone help explain positive and negative feedback in simple term
Gum
negative feedback is the arresting of reaction or reverse of the reaction according to the response and postive feed back is the direct response without reversing or arresting a reaction.
Greet
OK
umar
pls can someone explained Kinney stone in memorising in shot time
umar
what tyoebif microorganism will be killed by antibiotic trwatmeant
Mary Reply
I don't really don't understand aerobic respiration anaerobic respiration and fermentation. Can someone explain & breakdown this in the simplest way please.
Kisha
Anaerobic Respiration in which foodstuffs are partially oxidized, with the release of chemical energy, in a process not involving atmospheric oxygen, such as alcoholic fermentation, in which one of the end products is ethanol.
Muhammad
aerobic respiration A type of respiration in which foodstuffs are completely oxidized to carbon dioxide and water, with the release of chemical energy, in a process requiring atmospheric oxygen.
Muhammad
please can someone explain what pseudomonas species and biofilm is?
uju
Fermentation is the growth of cells or microorganisms in bioreactors (fermenters) to synthesize special products. Fermentation in biochemistry refers to the biodegradation of carbon compounds by cells or organisms under anaerobic (lack of oxygen) conditions.
Muhammad
Please under which conditions does pathogens become established in the human tissues and can cause diseases
Atambilla
please the life cycle of plasmodium parasite
mavis
who is John Needham
Mary Reply
John Needham is one of the researcher in microbiology. He also experimented when scientists did not believe animals could arise spontaneously ,but did believe microbes could.
Gum
okay is he late
Mary
by the way what are the list of courses offered by a newly admitted student for microbiology
Mary
Needham's experiments with beef gravy and infusions of plants material reinforced this idea.
Gum
what drugs are given to a person with Otis nerve problem(ear problem)
Gum Reply
good morning to you all.
Muhammad Reply
Dr.A.K.S.P.G. college Akbarpur Ambedkar Nagar
Rajan
Shailesh Vishwakarma BSc 1st year
Rajan
differentiate between eukaryotes en prikaryotes
AKANKWATSA Reply
eukaryotes are organisms with complex cellular structure(presence of nucleus and mitochondrial) like plants and animals whilst prokaryotes are organisms with simple cellular structure (absence of nucleus, mitochondrial) like arthropods.
Seidu
hlo
Shagufta
hii
dr
hello sir
pankaj
I am Pankaj from bihar
pankaj
I am study in NDRI karnal in btech in dairy
pankaj
I am Pankaj from bihar
pankaj
thanks am studying biomedical sciences in zambia.chikankata
Sharon
Am a studying Disease Control in Ghana(kintampo)
Seidu
I'm studying Environmental health in Zimbabwe 🇿🇼
trust
am Joyce mwale studying nursing in Lusaka Zambia
Joyce
hi pankaj
Shailesh
hi frds iam from India
Nevil
IAM studying degree (micro biology)
Nevil
Hi I am microbiologist
Muhammad
Hi friends I'm from Nigeria studying Microbiology
uju
i am biotechnologist from pakistan
Saddam
hi feds iam from india
Shibanjan
hi
Krishna
india
Krishna
hy frnds am from Uganda
AKANKWATSA
am studying nursing/midwifery n kampala
AKANKWATSA
I'm Gum Joseph Kakuu from Ghana,I'm studying RGN in nursing Jirapa.
Gum
I'm Hellen from Kenya studying applied biology
Hellen
I live in india
Krishna
am studying biotechnology
Krishna
am maryjoy uwaoma from Nigeria,I am studying microbiology in NSUKKA NIGERIA
Mary
Nice meeting You people hear
Seidu
thanks you.
Gum
can someone in there own words in the simplest way breakdown what aerobic respiration anaerobic respiration and fermentation means please and not from the dictionary version...!
Kisha
what are the cultivation and identification of microorganisms
Algel Reply
ransport media.basic culture media.enriched media..differential media .indetification media
AKANKWATSA
algel th above are some v th basic medias for bacterial growth
AKANKWATSA
factors that can Prone the host to get disease
Linda Reply
what are the factors that prones host to get disease
Linda
HELLO
Hashim
Not sure about it, can you tell us Linda?
KINGSFORD
please I want to know the factors that prones host to get disease
Linda
please Linda we have internal and external factors. internal factors are within our body cavities.eg mother having TB giving it to her child,and the others. external factors are within our surrounding environment which include our daily activities(bathing, buying food and the others)
Gum
I don't understand aerobic respiration anaerobic respiration and fermentation. Can someone that do give me a short & simple breakdown.
Kisha
pliz kisha ..aerobic respiration is th typ v repiration whre organisms use oxgyen for survival while anaerobic respiration is whre organisms survive without oxgyen at all.these use carbondioxide
AKANKWATSA
Guys pls answer me this question fast... What are the purpose of infection prevention in 50 words..
RAPHERA Reply
The purpose of infection and prevention is a scientific approach and practical solution designed to prevent harm cause by infection to Pt and health worker
what is the sequence of kingdom concept?
isha Reply
what is immunity
Algel
what are the classification and identification of microorganisms
Algel
whats anatomy
abdiqani
and physiology
abdiqani
anatomy is the study of the human structure
physiolog is the study of the human body function
Anatomy and physiology is the study of the human body parts and their functions.
Kwame
who's the father of Microbiology
The definition you gave is not for the two
Samuel
leeuwenhoek is the real father of microbiology
abdiqani
anatomy is the study of the structure and relationship between body part while Physiolog is the study of the function of body part
thats real definition
abdiqani
I am sure about Louis pasteur been the real father of microbiology
Mary
microbiology father is marcelo
DENNIS
sorry the father is Anthony Van Leeuwenhoek
DENNIS
The father is Marcello Malpighi
DENNIS
Anatomy and physiology is the study of the body structures and how they relate to each other
Unbeatable
which drawing in figure 4.1 is a tetrad
adnaloy Reply
OK I hear
stella
syphilis a reproductive disease?
Ulamila Reply
yaa but not exactly
Medhini
STD
Medhini
what are the possible disease cause by virse?
Victor
what is improtance thing we need to know about fungi!
Victor
toxins,ancient origin ,and diseases by fungi are very hard to cure
kalyani
STD
Uko
The disease cause by virus is HIV/AIDS
thanks
Victor
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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