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Mucous membranes

The mucous membrane s lining the nose, mouth, lungs, and urinary and digestive tracts provide another nonspecific barrier against potential pathogens. Mucous membranes consist of a layer of epithelial cells bound by tight junctions. The epithelial cells secrete a moist, sticky substance called mucus , which covers and protects the more fragile cell layers beneath it and traps debris and particulate matter, including microbes. Mucus secretions also contain antimicrobial peptides.

In many regions of the body, mechanical actions serve to flush mucus (along with trapped or dead microbes) out of the body or away from potential sites of infection. For example, in the respiratory system, inhalation can bring microbes, dust, mold spores, and other small airborne debris into the body. This debris becomes trapped in the mucus lining the respiratory tract, a layer known as the mucociliary blanket. The epithelial cells lining the upper parts of the respiratory tract are called ciliated epithelial cells because they have hair-like appendages known as cilia. Movement of the cilia propels debris-laden mucus out and away from the lungs. The expelled mucus is then swallowed and destroyed in the stomach, or coughed up, or sneezed out ( [link] ). This system of removal is often called the mucociliary escalator .

A spongy-looking surface with tufts of long hairs. Each hair is about 5 µm long; each tuft is about 10 µm in diameter.
This scanning electron micrograph shows ciliated and nonciliated epithelial cells from the human trachea. The mucociliary escalator pushes mucus away from the lungs, along with any debris or microorganisms that may be trapped in the sticky mucus, and the mucus moves up to the esophagus where it can be removed by swallowing.

The mucociliary escalator is such an effective barrier to microbes that the lungs, the lowermost (and most sensitive) portion of the respiratory tract, were long considered to be a sterile environment in healthy individuals. Only recently has research suggested that healthy lungs may have a small normal microbiota. Disruption of the mucociliary escalator by the damaging effects of smoking or diseases such as cystic fibrosis can lead to increased colonization of bacteria in the lower respiratory tract and frequent infections, which highlights the importance of this physical barrier to host defenses.

Like the respiratory tract, the digestive tract is a portal of entry through which microbes enter the body, and the mucous membranes lining the digestive tract provide a nonspecific physical barrier against ingested microbes. The intestinal tract is lined with epithelial cells, interspersed with mucus-secreting goblet cells ( [link] ). This mucus mixes with material received from the stomach, trapping foodborne microbes and debris. The mechanical action of peristalsis , a series of muscular contractions in the digestive tract, moves the sloughed mucus and other material through the intestines, rectum, and anus, excreting the material in feces.

Figure a is a diagram of a single goblet cell. Cell is tall and slightly hour-glass shaped. The bottom of the cell is filled with a nucleus. The top shows the Golgi apparatus (folds of membranes), rough endoplasmic reticulum (folds of membranes with dots), secretory vesicles containing mucin (large bubbles), and microvilli (finger-like projections at the top). Figure b is a micrograph of two goblet cells within a row of epithelial cells. The epithelial cells are rectangular with a large nucleus visible. The goblet cells are thinner and have a clear (uncolored) top.
Goblet cells produce and secrete mucus. The arrows in this micrograph point to the mucus-secreting goblet cells (magnification 1600⨯) in the intestinal epithelium. (credit micrograph: Micrograph provided by the Regents of University of Michigan Medical School © 2012)

Questions & Answers

Types of micro organisms
Jennifer Reply
Who discovered plant and animal cell
Jennifer
Robert Hooke
Martha
Father of microbiology
Jennifer Reply
Antonie van Leeuwenhoek
Satarupa
Why are mitochondria and chloroplasts unable to multiply outside of a host cell?
Iqra Reply
iqra mitochondria arises from the division of existing mitochondria and they are fused together. they move around inside the cell with the interactions of the cytoskeleton that's why mitochondria unable to multiply outside the host cells chloroplasts has its own separate DNA from the plant cell.
Rana
short not on medical microbiology
Massah Reply
Hy
Iqra
hope you fine
Arif
love you
Arif
Assalamualaikum
Suhaib
arai yeh micro kai sth kis ko love hua
Umer
icrobiology is the scientific study of these microorganisms. Microorganisms are those organisms that are too small to see with the naked eye and include things like bacteria, fungi, and viruses
Suhaib
iqra iqbal
Arif
What is gram syaining?
Arif
to differentiate between gram positive and gram negative bacty
Umer
True
Arif
where you are from
Arif
i m frm sopore..kashmir
Umer
i m frm baramulla .. Kashmir
Umer
and u
Umer
umer
Arif
and i m from afghanistan lovely country
Arif
yes
Umer
thanks
Arif
medical microbiology means study of microorganisms which are beneficial or harmful for the body. mostly which are studied under microscope by structure and shape appearance. e.g bacteria, viruses, bacteriophage, fungus hyphae and some blood and other body fluids parasites e.g plasmodium etc.
Rana
arif bhai gram staining in which we are given different dyes to the bacterial cell wall and cytoplasm and nucleus.e.g giemsa stain
Rana
Gram staining uses crystal violet to stain cell walls iodine as a mordant and a fuchsin or safranin counterstain to mark all bacteria
Umer
Gram staining uses crystal violet to stain cell walls iodine as a mordant and a fuchsin or safranin counterstain to mark all bacteria
Umer
Gram staining uses crystal violet to stain cell walls iodine as a mordant and a fuchsin or safranin counterstain to mark all bacteria
Umer
Omar baba crystal violet iodine 70% alcohol fuchicine or safranine after every step washing must be done
Rana
hello
Cristy
*Fuchsin stain
Cristy
*Safranin
Cristy
thanks
Ganesh
difference between epidermophyton trichophyton and microsporum
Ankita Reply
plz answer the question
Iqra
epidermophyton type of fungi causes superficial and cutaneous mycoses trichophyton is also fungi type including parasitic varieties causes dermatophytosis microsporum is also type of fungi causes dermatophytosis.
Rana
ok
Iqra
Is this app perfect for preparation of exam?
Ankita
Ankita I totally disagree with your respected opinion. it's just minor helpful
Rana
disagree by me ?
Ankita
what is infectious
Fred Reply
Many poeple are die due to covid-19 virus
AMINU Reply
they become sick due to millions bacteria, fungi and some insects that make plants as their host.
charles Reply
what are microbes and what are their effects to humans
charles Reply
they are organism that cannot be seen with the naked eye
Angel
classify microorganisms.
Satarupa Reply
protozoa' bacteria' virus' algai' archea'
Cabdifitaax
protozoa
Ayesha
Thank you
Satarupa
bacteria,fungi, protozoa and virus
Angel
mutant having a requirement for a certain growth factor is called a(n)
Purushoth Reply
what is atome
Marie Reply
is the smallest part of any material that cannot be broken up by chemical means
Feisal
How does forest tree become sick
Emmanuel
Aseptate hyphae are seen in
lab Reply
yes
Ahmed
w
Ahmed
hello
Apdikrim
what is ADT
Feisal
hii
Salman
how does this work bro
Feisal
CHEMISTRY
Apdikrim
biology
Ahmed
I.m student
Ahmed
I.m question what is difference between arthropod and insect?
Ahmed
Arthropod is a large division of jointed-foot Invertebrates such as Insects, centipedes and others so Insect is a part of the division or the phylum
hilina
thanks
Ahmed
ur welcome
hilina
describe binary fission
Queen Reply
in which parent cell devides into two daughter cells
Iqra
single parent cell
Tean
who is the father of microbiology
Mary Reply
Antonie van Leeuwenhoek , he is father of microbiology and Louis Pasteur is father of modern microbioloy.
Arshad
Anton van leeuwenhoek ( He descovered bacteria in 1679)
Satarupa
what is the contriyo sachilden and sachwan in cell thoery
Iqra
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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