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Many red blood cells with a single larger cell. The larger cell is pink with a purple region that fills nearly the entire cell. The purple region is labeled perforin-containing granules.
Natural killer cell with perforin-containing granules. (credit: modification of work by Rolstad B)

Monocytes

The largest of the white blood cells, monocytes have a nucleus that lacks lobes, and they also lack granules in the cytoplasm ( [link] ). Nevertheless, they are effective phagocytes, engulfing pathogens and apoptotic cells to help fight infection.

When monocytes leave the bloodstream and enter a specific body tissue, they differentiate into tissue-specific phagocytes called macrophages and dendritic cells . They are particularly important residents of lymphoid tissue, as well as nonlymphoid sites and organs. Macrophages and dendritic cells can reside in body tissues for significant lengths of time. Macrophages in specific body tissues develop characteristics suited to the particular tissue. Not only do they provide immune protection for the tissue in which they reside but they also support normal function of their neighboring tissue cells through the production of cytokines. Macrophages are given tissue-specific names, and a few examples of tissue-specific macrophages are listed in [link] . Dendritic cells are important sentinels residing in the skin and mucous membranes, which are portals of entry for many pathogens. Monocytes, macrophages, and dendritic cells are all highly phagocytic and important promoters of the immune response through their production and release of cytokines. These cells provide an essential bridge between innate and adaptive immune responses, as discussed in the next section as well as the next chapter.

Monocytes are large cells with a large purple nucleus. There is a cluster of them in a field of smaller red blood cells. A PMN is also visible with a dark, multi-lobed nucleus. Macrophages are large cells with a defined nucleus.
Monocytes are large, agranular white blood cells with a nucleus that lacks lobes. When monocytes leave the bloodstream, they differentiate and become macrophages with tissue-specific properties. (credit left: modification of work by Armed Forces Institute of Pathology; credit right: modification of work by Centers for Disease Control and Prevention)
Macrophages Found in Various Body Tissues
Tissue Macrophage
Brain and central nervous system Microglial cells
Liver Kupffer cells
Lungs Alveolar macrophages (dust cells)
Peritoneal cavity Peritoneal macrophages
  • Describe the signals that activate natural killer cells.
  • What is the difference between monocytes and macrophages?

Key concepts and summary

  • The formed elements of the blood include red blood cells ( erythrocytes ), white blood cells ( leukocytes ), and platelets (thrombocytes ). Of these, leukocytes are primarily involved in the immune response.
  • All formed elements originate in the bone marrow as stem cells (HSCs) that differentiate through hematopoiesis .
  • Granulocytes are leukocytes characterized by a lobed nucleus and granules in the cytoplasm. These include neutrophils (PMNs) , eosinophils , and basophils .
  • Neutrophils are the leukocytes found in the largest numbers in the bloodstream and they primarily fight bacterial infections.
  • Eosinophils target parasitic infections. Eosinophils and basophils are involved in allergic reactions. Both release histamine and other proinflammatory compounds from their granules upon stimulation.
  • Mast cells function similarly to basophils but can be found in tissues outside the bloodstream.
  • Natural killer ( NK ) cells are lymphocytes that recognize and kill abnormal or infected cells by releasing proteins that trigger apoptosis.
  • Monocytes are large, mononuclear leukocytes that circulate in the bloodstream. They may leave the bloodstream and take up residence in body tissues, where they differentiate and become tissue-specific macrophages and dendritic cells .

Matching

Match each cell type with its description.

___natural killer cell A. stains with basic dye methylene blue, has large amounts of histamine in granules, and facilitates allergic responses and inflammation
___basophil B. stains with acidic dye eosin, has histamine and major basic protein in granules, and facilitates responses to protozoa and helminths
___macrophage C. recognizes abnormal cells, binds to them, and releases perforin and granzyme molecules, which induce apoptosis
___eosinophil D. large agranular phagocyte that resides in tissues such as the brain and lungs

C, A, D, B

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Match each cellular defense with the infection it would most likely target.

___natural killer cell A. virus-infected cell
___neutrophil B. tapeworm in the intestines
___eosinophil C. bacteria in a skin lesion

A, C, B

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Fill in the blank

Platelets are also called ________.

thrombocytes

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The cell in the bone marrow that gives rise to all other blood cell types is the ________.

pluripotent hematopoietic stem cell (HSC)

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PMNs are another name for ________.

neutrophils

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Kupffer cells residing in the liver are a type of ________.

macrophage

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_____________ are similar to basophils, but reside in tissues rather than circulating in the blood.

mast cells

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Short answer

Explain the difference between plasma and the formed elements of the blood.

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List three ways that a neutrophil can destroy an infectious bacterium.

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Questions & Answers

what is prokaryotes
PRALHAD Reply
are micro-organisms that have no nucleus e.g bacteria
Foster
and they do not possess membrane bound organelles e.g mitochondria
Bharat
yes
Foster
they are single cellular organisms,
Rajasekhar
all the organelles are embedded in cytoplasm of the cell
Rajasekhar
They don't possess true nucleus
PREMI
they're unicellular organisms
Kamaluddeen
they are classified as bacteria and. archaea. bacteria have a cell membrane conposed of peptidoglycan and archaea is composed of psuedomu
Tara
pseudomurein
Tara
organelles are non membraneous as the nucleus
Tara
What is the biosynthesis of a bacteria cell
Adesina Reply
biosynthesis is multiple step enzymes catalyze process which occur in bacterial cell
Jayeeta
biological way of manufacturing food and utilizes it for growth, multiplication and development
Kamaluddeen
prokaryot
PRALHAD
what is microbiology
Kiirya Reply
which organism can not be seen necked eyes is knowm as microbiology
meet
microorganisms
Jayeeta
micro can be define as d smallest living organisms dat can not be see wit naked eyes only with the aid of a microscope 🔬
muhammed
bio means life logy means study
muhammed
biology can b define as the systematic study of living things
muhammed
microbiology can be define as the study of tiny organisms, that's according to my understanding
muhammed
Microbiology is the study of living organisms which cannot be seen by the naked eye but only with the aid of a microscope. These microorganisms can be classified as bacteria, fungi, micro-algae, protozoa and virus.
Tatz
microbes that can't seen in naked eyes. upto 100micrometer we can see in naked eyes but 1 microns or nanometers are invisible in naked eye.
Jayeeta
what is a cell
Oteri Reply
cell can be define as smallest indivisible organism in the body
muhammed
cell is the smallest unit which makes up the whole body
Yue
cell is smallest unit and there are two types prokaryotic cell and eukaryote cell. bacteria a prokaryotic cell which works independently.
Jayeeta
nice forum
muhammed
Which parasite competes with the host for vitamin B12 to cause pernicious anaemia
Abubakar
Diphyllobothrium latum for vit B12
Jayeeta
it is also fish tapeworm
Jayeeta
Diphyllobothrium sp feed vitB 12
Jayeeta
recent trends in microbiology of biofertilizer
Ykomalipriya Reply
using nano technology
Jayeeta
what is transposors
EMMANUEL Reply
Junk DNA, jumping gene.
Pradeep
transposon elements are jumping gene as DNA sequence move from one location to anothet
Jayeeta
Yes
Pradeep
what is microbiology
Usama Reply
Microbiology is the study of organisms, most of which are too small to be seen with the naked eye, including bacteria, algae, protozoa, and fungi, as well as acellular agents, such as viruses and prions.
digvijaya
what is gram +ve and gram - ve bacteria?
Sharma
gm- contain lipid layer so it take counter stain during gram staining and pink or red in color but gm + does have thick LPS layer.
Jayeeta
what year microbiology started
Kartik
Robert Koch was the first to detect microorganisms
Jayeeta
what appears microorganisms
Kartik
clear the questions please
Jayeeta
was it robert koch or robert hooke?
digvijaya
microbiology word came from microns. study microbes that not recognize in naked eyes.
Jayeeta
what are the branch of microbiology
Oyemade Reply
We can basically classify into pure and applied microbiology
Ozzie
what is arabinose operon and it's stucture
Pooja Reply
The L-arabinose operon, also called the ara or araBAD operon, is an operon required for the breakdown of the five-carbon sugar, L-arabinose, in Escherichia coli
Tharra
kya hum operon ko divide kar skate hain
Kartik
reactions if viruses to physical and chemical agents?
VICTOR Reply
All viruses contain the following two components: 1) a nucleic acid genome and 2) a protein capsid that covers the genome. Together this is called the nucleocapsid. In addition, many animal viruses contain a 3) lipid envelope. The entire intact virus is called the virion.
Asali
assume you have performed a gram stain on a sample of pus from a patients urethra. you see red, nucleated cells and purple rods. what can you conclude
Petty Reply
bacteria
ABUBAKAR
gram negative bacteria hence gonococcal infection
Kiirya
Study of micro organisation which we cannot see with naked eye...
shyam Reply
Despite their bad reputation, microbes are mostly beneficial or have a neutral effect on our lives. Microbiology 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.
Asali
yes
Dhirender
not 'things'...'organisms' like bacterias, viruses and fungi
Sinmi
simi, it's not bacterias but bacteria which is the plural form of the word while bacterium is the singular of it
Richard
bacterium is obvio in a singular form but plural of bacterium is bacterias
Sinmi
Richard is right it's bacterium which is the singular form and plural is bacteria. *Bacterias* doesn't exist.
Aakriti
that is microbiology which is deals with microbes only their structure
Kiirya
what is microbiology?
Sandeep Reply
what is microbiology
Glory
is the study of small microorganisms that can't be viewed by our naked eyes under a microscope
Nabukwasi
it's the study of microbes their classification, diversity, their cellular structure and processes, their applications and interaction with other organisms.
Chaitanya
what is EMP pathway
rajesh
which organism is implicated in meningoencephalitis
Peter Reply
Herpes virus
Carlos
Yeah
Laxmi
which mold is called dairy mold?
Gopinath
mushroomm
Top
Geotrichum candidum
Gopinath
hi
bio
Hlw
Laxmi
which infectious agent is the smallest
Sinmi
spore or virus
Anushree
prion ....it is a single protein in a misfolded form..there is also a theory based on it
Sinmi
yup...m sry
Anushree
yes it can be turned as a virus
Sinmi
which gram positive bacteria is responsible for food poisoning?
Sinmi
prion is not a living organism yet it is infectoois why
Jeevan
prions are virus like organism. and it is a misfolded protein that may cause disease to us.
Tharra
Clostridium perfringens, B.cereus
Sneha
Who is the father of the biology
Dhirender
I have one more question. . that who is the father of botany and medicine? ? can any one tell
Dhirender
define polar bond in simple way
Rashmi Reply
when there is formation of positive and negative poles i.e. one atom is +ve and other is -ve which further results in the dipole moment. Such bond is know as polar bond. It is a convalent bond only.
Aakriti

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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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