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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

deffination of staining
Bhavanimangali Reply
with the aid of a well labeled diagram describe the conducting system
Maridad Reply
what is cellular immunity
namugenyi Reply
Cellular Immunity. -Lymphocytes act against target cell. -Acts directly by killing infected cells.
abdinor
What are NK cells
Peter
Natural killer cells
Rahaba
what are Antigen determinant
mary
cellular immunity is the state where the lymphocytes destroy the infected or targeted cell
cynthia
any examples of oedema
cynthia
introduction of microbial diversity-1
Bhavanimangali Reply
List the type of micro organism arround us and how they can be seen and with what kind of instrument
clinton Reply
how is the arrangements of bacteria in bacilli
Vaidah Reply
Provide some examples of bacterial structures that might be used as antibiotic targets and explain why.
Vaidah
Coccobacilli, Club-Shaped bacilli, Bacilli with rounded ends, Fuilform bacilli, Bacilli with ends square.
Enoch
three main antibiotic targets in bacteria: The cell wall or membranes that surrounds the bacterial cell. The machineries that make the nucleic acids DNA and RNA. The machinery that produce proteins
Rushikesh
The bacterial cell wall. Protein production. and DNA synthesis. Why, this is because most drugs (antibiotics) affects the cell wall of the bacteria, which makes the bacteria weak or susceptible in human body.
Enoch
UV rays affecting the..
Mali Reply
what is microbiology
Baba Reply
Microbiology is the study of microorganisms, which are prokaryotic and eukaryotic cell which includes bacteria, fungi, viruses and pathogenic protozoa.
Enoch
Microbiology is the branch of Life science which deals with scientific study of many Microorganisms.
Rushikesh
what is types of microbiology
Alsheikh
Immunology, Bacteriology, Virology, Mycology, Algology etc
Enoch
Virology, Immunology, Bacteriology, Algology, Mycology, Protoozology etc
Enoch
and what is mycology
Alsheikh
Immunology, Serology, Virology, Microbial Genetics, Parasitology, Bacteriology, Mycology, Molecular, Cell Biology, Agricultural, Water,Soil, Food Industrial ,Pharmaceutical, Applied, Environmental, Clinical, Medical,Marine Microbiology, Microbial Systematics, Etc, are & many types of Microbiology.
Rushikesh
study of fungi is called mycology
Munna
Mycology is the branch of Microbiology which deals with scientific study of Fungi.
Rushikesh
Study of microorganisms,which we can't see with our naked eye is called microbiology
Munna
Mycology is the scientific study of Fungi.
Enoch
virology is the study of viruses
Oppah
what is microbiology? microbiology is the study of small microorganisms that we can not with our naked eyes.
Leticia
what is taxonomical classification of microbiology
Bami
The algae, protozoa, slime moulds, fungi, bacteria, archaea and viruses ,are taxonomic classification of Microorganisms
Rushikesh
We have Bacteria, Archaea, Protozoa, Algae, Fungi, Viruses.
Enoch
microbiology is the study of microbes too small to be seen by naked eyes
Maridad
microbiology is a branch of biology which deals with study of smallest living microrganisms such as bacteria protozoa fungi and viruses
Chaitra
microbiology is the study of microorganisms which can't be seen by our naked eyes
Nakaweesi
Micro - Minute Bio - Life Logus - Study
Roshan
what is the meaning of antimicrobial susceptibility testing
Devshree Reply
seven gram positive bacteria
Okocha Reply
seven examples of gram negative bacteria
Okocha
seven examples of gram negative bacteria
Okocha
Physical conditions that would enable selective Isolation of staphylococcus epidermis
shongile Reply
Nutritional requirements that would enable selective Isolation of staphylococcus epidermis
shongile
Nutritional requirements that would enable selective Isolation of staphylococcus epidermis
shongile
what is constant flux but
Jane Reply
Digestion of food is completed in __
Amina Reply
Small Intestine
Enoch
large inteatine
Abdiwali
small intestine
Betelhem
Small intestine
Abdirisaq
small intestine
Marah
small intestine specific in illum
Mariam
difference btwn hausteria and appears
Raviha Reply
numerical and molecular taxanomy
Dhanshri Reply
difference btwn hausteria and appesorium
Raviha
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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