<< Chapter < Page Chapter >> Page >

The watery material inside of the eyeball is called the vitreous humor . Unlike the conjunctiva, it is protected from contact with the environment and is almost always sterile, with no normal microbiota ( [link] ).

A cross section of the eye. The large spherical center is the vitreous humor. The layer surrounding this is the retina. A projection out of the back of the eye is the optic nerve. A region on the retina just above the optic nerve is the fovea. At the front of the eye is the lens. In front of this is a space labeled pupil. The colored region around the pupil is the iris. The cornea is the covering in front of the iris and pupil. The conjunctiva is a mucous membrane on the eye.
Some microbes live on the conjunctiva of the human eye, but the vitreous humor is sterile.

Infections of the eye

The conjunctiva is a frequent site of infection of the eye; like other mucous membranes, it is also a common portal of entry for pathogens. Inflammation of the conjunctiva is called conjunctivitis , although it is commonly known as pinkeye because of the pink appearance in the eye. Infections of deeper structures, beneath the cornea, are less common ( [link] ). Conjunctivitis occurs in multiple forms. It may be acute or chronic. Acute purulent conjunctivitis is associated with pus formation, while acute hemorrhagic conjunctivitis is associated with bleeding in the conjunctiva. The term blepharitis refers to an inflammation of the eyelids, while keratitis refers to an inflammation of the cornea ( [link] ); keratoconjunctivitis is an inflammation of both the cornea and the conjunctiva, and dacryocystitis is an inflammation of the lacrimal sac that can often occur when a nasolacrimal duct is blocked.

a) photo of an eyelid being pulled back to show a red are. B) A photo of inflamed eyelids. C)A photo of an eye with a cloudy cornea.
(a) Conjunctivitis is inflammation of the conjunctiva. (b) Blepharitis is inflammation of the eyelids. (c) Keratitis is inflammation of the cornea. (credit a: modification of work by Lopez-Prats MJ, Sanz Marco E, Hidalgo-Mora JJ, Garcia-Delpech S, Diaz-Llopis M; credit b, c: modification of work by Centers for Disease Control and Prevention)

Infections leading to conjunctivitis, blepharitis, keratoconjunctivitis, or dacryocystitis may be caused by bacteria or viruses, but allergens, pollutants, or chemicals can also irritate the eye and cause inflammation of various structures. Viral infection is a more likely cause of conjunctivitis in cases with symptoms such as fever and watery discharge that occurs with upper respiratory infection and itchy eyes. [link] summarizes some common forms of conjunctivitis and blepharitis.

Types of Conjunctivities and Blepharitis
Condition Description Causative Agent(s)
Acute purulent conjunctivitis Conjunctivitis with purulent discharge Bacterial ( Haemophilus , Staphylococcus )
Acute hemorrhagic conjunctivitis Involves subconjunctival hemorrhages Viral ( Picornaviradae )
Acute ulcerative blepharitis Infection involving eyelids; pustules and ulcers may develop Bacterial ( Staphylococcal ) or viral (herpes simplex, varicella-zoster, etc.)
Follicular conjunctivitis Inflammation of the conjunctiva with nodules (dome-shaped structures that are red at the base and pale on top) Viral ( adenovirus and others); environmental irritants
Dacryocystitis Inflammation of the lacrimal sac often associated with a plugged nasolacrimal duct Bacterial ( Haemophilus, Staphylococcus , Streptococcus )
Keratitis Inflammation of cornea Bacterial, viral, or protozoal; environmental irritants
Keratoconjunctivitis Inflammation of cornea and conjunctiva Bacterial, viral (adenoviruses), or other causes (including dryness of the eye)
Nonulcerative blepharitis Inflammation, irritation, redness of the eyelids without ulceration Environmental irritants; allergens
Papillary conjunctivitis Inflammation of the conjunctiva; nodules and papillae with red tops develop Environmental irritants; allergens
  • How does the lacrimal apparatus help to prevent eye infections?

Key concepts and summary

  • Human skin consists of two main layers, the epidermis and dermis , which are situated on top of the hypodermis , a layer of connective tissue.
  • The skin is an effective physical barrier against microbial invasion.
  • The skin’s relatively dry environment and normal microbiota discourage colonization by transient microbes.
  • The skin’s normal microbiota varies from one region of the body to another.
  • The conjunctiva of the eye is a frequent site for microbial infection, but deeper eye infections are less common; multiple types of conjunctivitis exist.

Fill in the blank

The ________ is the outermost layer of the epidermis.

stratum corneum

Got questions? Get instant answers now!

The mucous membrane that covers the surface of the eyeball and inner eyelid is called the ________.

conjunctiva

Got questions? Get instant answers now!

Short answer

What is the role of keratin in the skin?

Got questions? Get instant answers now!

What are two ways in which tears help to prevent microbial colonization?

Got questions? Get instant answers now!

Which label indicates a sweat gland?

A diagram of skin. i – a vase shape in the center of skin with a long projection out the top. iv – the long projection from i. iii – a small vase shape attached to i. ii – a coiled structure in the center with a tube leading out.
(credit: modification of work by National Cancer Institute)
Got questions? Get instant answers now!

Questions & Answers

how does Neisseria cause meningitis
Nyibol Reply
what is microbiologist
Muhammad Reply
what is errata
Muhammad
is the branch of biology that deals with the study of microorganisms.
Ntefuni Reply
What is microbiology
Mercy Reply
studies of microbes
Louisiaste
when we takee the specimen which lumbar,spin,
Ziyad Reply
How bacteria create energy to survive?
Muhamad Reply
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Muhamad
they make spores
Louisiaste
what is sporadic nd endemic, epidemic
Aminu Reply
the significance of food webs for disease transmission
Abreham
food webs brings about an infection as an individual depends on number of diseased foods or carriers dully.
Mark
explain assimilatory nitrate reduction
Esinniobiwa Reply
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
Elkana
Examples of thermophilic organisms
Shu Reply
Give Examples of thermophilic organisms
Shu
advantages of normal Flora to the host
Micheal Reply
Prevent foreign microbes to the host
Abubakar
they provide healthier benefits to their hosts
ayesha
They are friends to host only when Host immune system is strong and become enemies when the host immune system is weakened . very bad relationship!
Mark
what is cell
faisal Reply
cell is the smallest unit of life
Fauziya
cell is the smallest unit of life
Akanni
ok
Innocent
cell is the structural and functional unit of life
Hasan
is the fundamental units of Life
Musa
what are emergency diseases
Micheal Reply
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
define infection ,prevention and control
Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
Lubega
Heyy Lubega hussein where are u from?
_Adnan
en français
Adama
which site have a normal flora
ESTHER Reply
Many sites of the body have it Skin Nasal cavity Oral cavity Gastro intestinal tract
Safaa
skin
Asiina
skin,Oral,Nasal,GIt
Sadik
How can Commensal can Bacteria change into pathogen?
Sadik
How can Commensal Bacteria change into pathogen?
Sadik
all
Tesfaye
by fussion
Asiina
what are the advantages of normal Flora to the host
Micheal
what are the ways of control and prevention of nosocomial infection in the hospital
Micheal
what is inflammation
Shelly Reply
part of a tissue or an organ being wounded or bruised.
Wilfred
what term is used to name and classify microorganisms?
Micheal Reply
Binomial nomenclature
adeolu

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Microbiology' conversation and receive update notifications?

Ask