The aqueous humour is a transparent, watery fluid similar to plasma, but containing low protein concentrations. It is secreted from the ciliary epithelium, a structure supporting the lens
INTRODUCTIONThe clear fluid filling the space in front of the eyeball between lens and cornea.The aqueous humour supplies nutrition and removes waste from the clear structure in the anterior eye(cornea and lens)The balance between aqueous production and outflow determines the intraocular pressure.
INTRODUCTION
The clear fluid filling the space in front of the eyeball between lens and cornea.
The aqueous humour supplies nutrition and removes waste from the clear structure in the anterior eye(cornea and lens)
The balance between aqueous production and outflow determines the intraocular pressure.
The tear film constitutes Three layers :- An outermost lipid (oily) layer An aqueous (watery) layer that makes up 90% of the tear film volume; and A mucin layer that coats the corneal surface.
3. To form smooth optical surface on cornea. To keep the surface of cornea & conjunctiva moist It serve as lubricant It transfer oxygen Provide antibacterial action Wash debris out It provides a pathway for WBC in case of injury
4. Functions of lipid layer Retards evaporation of tear film Prevents the overflow of tears
5. Function of Aqueous Layer Flushes, buffers and lubricates the corneal surface Delivers oxygen and other nutrients to the corneal surface Wash out debris Delivers antibacterial enzymes and antibodies such as lysozyme.
6. Functions of Mucin Layer Spreads tears over corneal surface. Protects the cornea against foreign substances . Makes corneal surface smooth by filling in surface irregularities
The tear film is a complex mixture of substances secreted from multiple sources on the ocular surface, including the lacrimal gland, the accessory lacrimal glands, the meibomian glands, and the goblet cells.
Anatomy and Physiology of Aqueous Humor Sumit Singh Maharjan
2. Anatomy
3. Angle of anterior chamber
4. Angle of the Anterior chamber
5. Gonioscopic grading of Angle
6. Aqueous Outflow system
7. Trabecular meshwork
8. Functions of Aqueous Humor • Maintenance of Intraocular pressure • Metabolic role cornea lens vitreous and retina • Optical function • Clearing function
9. Physicochemical properties • volume: 0.31ml (0.25ml in Ant. Chamber and 0.06 in post chamber) • Refractive index: 1.336 • Density: slightly greater than water, its viscocity is 1.025-1.040 • Osmotic pressure: slightly hyperosmotic to plasma by 3-5mosm/l • PH: 7.2 • Rate of formation: 2-2.5microliter/min
10. Biochemical composition • Water: 99.9% • Proteins: 5-16mg/100ml • Amino acids: aqueous/plasma concentration varies from 0.08-3.14 • Non colloidal constituents: conc. of ascorbate, pyruvate, lactate in higher am
INTRODUCTIONThe clear fluid filling the space in front of the eyeball between lens and cornea.The aqueous humour supplies nutrition and removes waste from the clear structure in the anterior eye(cornea and lens)The balance between aqueous production and outflow determines the intraocular pressure.
INTRODUCTION
The clear fluid filling the space in front of the eyeball between lens and cornea.
The aqueous humour supplies nutrition and removes waste from the clear structure in the anterior eye(cornea and lens)
The balance between aqueous production and outflow determines the intraocular pressure.
The tear film constitutes Three layers :- An outermost lipid (oily) layer An aqueous (watery) layer that makes up 90% of the tear film volume; and A mucin layer that coats the corneal surface.
3. To form smooth optical surface on cornea. To keep the surface of cornea & conjunctiva moist It serve as lubricant It transfer oxygen Provide antibacterial action Wash debris out It provides a pathway for WBC in case of injury
4. Functions of lipid layer Retards evaporation of tear film Prevents the overflow of tears
5. Function of Aqueous Layer Flushes, buffers and lubricates the corneal surface Delivers oxygen and other nutrients to the corneal surface Wash out debris Delivers antibacterial enzymes and antibodies such as lysozyme.
6. Functions of Mucin Layer Spreads tears over corneal surface. Protects the cornea against foreign substances . Makes corneal surface smooth by filling in surface irregularities
The tear film is a complex mixture of substances secreted from multiple sources on the ocular surface, including the lacrimal gland, the accessory lacrimal glands, the meibomian glands, and the goblet cells.
Anatomy and Physiology of Aqueous Humor Sumit Singh Maharjan
2. Anatomy
3. Angle of anterior chamber
4. Angle of the Anterior chamber
5. Gonioscopic grading of Angle
6. Aqueous Outflow system
7. Trabecular meshwork
8. Functions of Aqueous Humor • Maintenance of Intraocular pressure • Metabolic role cornea lens vitreous and retina • Optical function • Clearing function
9. Physicochemical properties • volume: 0.31ml (0.25ml in Ant. Chamber and 0.06 in post chamber) • Refractive index: 1.336 • Density: slightly greater than water, its viscocity is 1.025-1.040 • Osmotic pressure: slightly hyperosmotic to plasma by 3-5mosm/l • PH: 7.2 • Rate of formation: 2-2.5microliter/min
10. Biochemical composition • Water: 99.9% • Proteins: 5-16mg/100ml • Amino acids: aqueous/plasma concentration varies from 0.08-3.14 • Non colloidal constituents: conc. of ascorbate, pyruvate, lactate in higher am
PHYSIOLOGY OF AQUEOUS HUMOUR & IOP REGULATION 3.pptxAkashChaurewar1
This ppt is made available for free to use and modification.
This is made for presentation for PG seminar activity during MS ophthalmology residency 1st year by Dr Akash Chaurewar under guidance of Dr. Shubha Ghonsikar with mentors - Dr. Archana Vare and other faculty.
I am a medical student. I have one friend who is persuing his MBBS degree in Taishan Medical UNiversity. I got these notes from him.
These notes are by Dr. Bikesh, He is a famous lecturer of TMU.
These notes have helped me a lot and i also watch his lecture videos , which are great; highly simple and huge content.
I am uploading with Renal physiology. If you want some other topics i would upload for you.
"Let the Knowledge be spread" Dr. Bikesh
An enzyme is a substance that acts as a catalyst in living organisms, regulating the rate at which chemical reactions proceed without itself being altered in the process. The biological processes that occur within all living organisms are chemical reactions, and most are regulated by enzymes
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. The cornea, with the anterior chamber and lens, refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power.
Lens is a transparent, biconvex, crystalline structure placed between iris and the vitreous in a saucer-shaped depression, the patellar fossa. The lens is a crystalline structure that is avascular and is devoid of nerves and connective tissue
It consists of three distinct part:
Lens capsule
Anterior lens epithelium, and
Lens substance or lens fibres
Small amounts of vitamins are required in the diet to promote growth, reproduction, and health. Vitamins A, D, E, and K are called the fat-soluble vitamins, because they are soluble in organic solvents and are absorbed and transported in a manner similar to that of fats.
Water soluble vitamins include Vitamin C and the vitamin B complex: thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), Vitamin B6, biotin (B7), folic acid (B9), Vitamin B12. Vitamin A in its Beta-Carotene form is also water-soluble.
A picornavirus is a virus belonging to the family Picornaviridae, a family of viruses in the order Picornavirales. Vertebrates, including humans, serve as natural hosts. Picornaviruses are nonenveloped viruses that represent a large family of small, cytoplasmic, plus-strand RNA viruses with a 30-nm icosahedral capsid.
Poxviruses are brick or oval-shaped viruses with large double-stranded DNA genomes. Poxviruses exist throughout the world and cause disease in humans and many other types of animals. Poxvirus infections typically result in the formation of lesions, skin nodules, or disseminated rash.
Leptospirosis is a bacterial disease that affects humans and animals. It is caused by bacteria of the genus Leptospira. In humans, it can cause a wide range of symptoms, some of which may be mistaken for other diseases. Some infected persons, however, may have no symptoms at all.
The human immunodeficiency virus (HIV) is a lentivirus (a subgroup of retrovirus) that causes HIV infection and over time acquired immunodeficiency syndrome (AIDS).
Treponema is a genus of spiral-shaped bacteria. The major treponeme species of human pathogens is Treponema pallidum, whose subspecies are responsible for diseases such as syphilis, bejel, and yaws.
Haemophilus is the name of a group of bacteria. There are several types of Haemophilus. They can cause different types of illnesses involving breathing, bones and joints, and the nervous system. One common type, Hib (Haemophilus influenzae type b), causes serious disease. It usually strikes children under 5 years old
Moraxella is a genus of Gram-negative bacteria in the Moraxellaceae family. It is named after the Swiss ophthalmologist Victor Morax. The organisms are short rods, coccobacilli, or as in the case of Moraxella catarrhalis, diplococci in morphology, with asaccharolytic, oxidase-positive, and catalase-positive properties
Pseudomonas is a type of bacteria that can cause infections. Pseudomonas is a common genus of bacteria, which can create infections in the body under certain circumstances. There are many different types of Pseudomonas bacteria
Neisseria gonorrhoeae is the obligate human pathogen that causes the sexually transmitted disease (STD) gonorrhea. This Gram-negative diplococci/gonococci does not infect other animals or experimental animals and does not survive freely in the environment. The gonococcal infection occurs in the upper or lower tract, pharynx, ophthalmic area, rectum, and bloodstream. During the 1980’s gonorrhea was also referred to as “the clap” when public awareness was quite minimal. This was one of the venereal diseases prostitutes hoped to contract since it resulted in infertility by pelvic inflammatory disease (PID). As documentation, diagnostic testing, and public awareness improved, there has been a decline in incidence reports, however, it is still considered a very common infectious disease.
Meningococci are a type of bacteria that cause serious infections. The most common infection is meningitis, which is an inflammation of the thin tissue that surrounds the brain and spinal cord. Meningococci can also cause other problems, including a serious bloodstream infection called sepsis. In its early stages, you may have flu-like symptoms and a stiff neck. But the disease can progress quickly and can be fatal. Early diagnosis and treatment are extremely important. Lab tests on your blood and cerebrospinal fluid can tell if you have it. Treatment is with antibiotics. Since the infection spreads from person to person, family members may also need to be treated.
A vaccine can prevent meningococcal infections.
Diphtheria is an infection caused by the bacterium Corynebacterium diphtheriae. Diphtheria causes a thick covering in the back of the throat. It can lead to difficulty breathing, heart failure, paralysis, and even death. CDC recommends vaccines for infants, children, teens and adults to prevent diphtheria. The presentation consists of basic concepts regarding the bacteria and its infection. It has explanation in detail about signs and symptoms of Diptheria
Contraindications, Adverse reactions and ocular nutritional supplementsArun Geetha Viswanathan
utritional supplements comprise a great deal of the products available over the counter in most pharmacies. Although most vitamin supplements are relatively harmless—except for the fat soluble ones A, D, E, and K—they are not the only supplements available to patients. Some of these other, non-vitamin supplements can actually be harmful to patients and often they have been proven to be ineffective. This doesn’t mean that patients will stop taking them though, which in turn leaves the potential for contraindications of nutritional supplements with prescription-based drugs wide open.
Ageing is a gradual process that takes place over many decades. Most theories of ageing relate to impaired DNA replication and loss of cell viability and hence the viability of the body’s organs. Ageing is often accompanied by socioeconomic changes that can have a great impact on the nutritional needs and status of elderly individuals. The incidence of disability increases with ageing, with over a third of the elderly population limited by chronic conditions and unable to carry on normal daily living activity
Every component of the eye is vulnerable to damage from ROI, particularly retina. There are several reasons for the vulnerability of the retina, including high concentrations of polyunsaturated fatty acid (PUFA), constant exposure to visible light, high consumption of oxygen, an abundance of photosensitisers in the neurosensory retina and the RPE, the process of phagocytosis by the RPE which is known to generate hydrogen peroxide.
Carotenoids are class of fat soluble coloured pigments, found primarily in plants, where they play a critical role in the photosynthetic process. Two xanthophylls, lutein (L) and zeaxanthin (Z) accumulate at the macula where they make up macular pigment (MP). In the human eye, the MP optical density (MPOD) is not uniformly distributed across the retina
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
2. Aqueous Humour
entire volume of fluid in the anterior chamber is
replaced 12 times a day, i.e. once every 2 hours
3. Formation of Aqueous Humor
• The ciliary processes are the site of aqueous production
• The aqueous humour is primarily derived from the plasma within the capillary network
of the ciliary processes
• The Leber’s theory (which was generally accepted for many
years) that aqueous is a simple filtrate from the blood does not hold true any more
• Presently, by and large, it is agreed that three mechanisms namely, diffusion,
ultrafiltration and secretion play a part in aqueous production at different levels
4. Formation of Aqueous Humor
1. Diffusion
• Diffusion is a biophysical process by which molecules of a gas or solution distribute
themselves uniformly throughout the space in which they are contained, by motion of
its particles
• In this process, there occurs net flux of the particles from areas of high concentration
to areas of low concentration
• Diffusion also occurs across a semipermeable membrane
5. Formation of Aqueous Humor
• Quantitatively the net movement of a substance across a semipermeable membrane
where only diffusion is occurring is expressed by Fick's law of diffusion as follows:
Rate of movement = K(C1-C2), where:
C1 = Concentration of substance on side with higher concentration.
C2 = Concentration of substance on side with lower concentration.
K = Constant which depends on nature and permeability of membrane, nature
of solute and solvent, and the temperature
• In the process of aqueous production, the lipid soluble substances are transported by
diffusion through the lipid portions of the cell membrane of the ciliary processes,
proportional to a concentration gradient across the membrane
6. Formation of Aqueous Humor
2. Ultrafiltration
A. Dialysis
• When a solution of protein and salt is separated from plain water or a less concentrated
salt solution by a membrane permeable to salt and water and not to proteins, there will
be a net movement of water on the protein side by diffusion and a movement of the salt
away from the protein side
• This process is called dialysis
7. Formation of Aqueous Humor
2. Ultrafiltration
• Ultrafiltration refers to occurrence of dialysis under hydrostatic pressure
• In the process of aqueous formation, water and water-soluble substances (limited by
size and charge) flow through the theoretical micropores in the protein part of the cell
membrane in response to osmotic gradient or hydrostatic pressure.
8. Formation of Aqueous Humor
3. Secretion (active transfer)
• Secretion implies an active process that selectively transports some substances across
the cell membrane
• Since energy is consumed, substances can be moved across a concentration gradient in
a direction opposite to what would be expected by passive mechanism alone
• In the process of aqueous formation, water soluble substances of larger size or greater
charge are actively transported across the cell membrane
• This mechanism is believed to be mediated by globular proteins in the membrane and
requires the expenditure of energy
9. Steps/scheme of aqueous formation
• The major factor in aqueous production (approximately 70%) is active secretion
• Ultrafiltration accounts for 20% and osmosis 10%
• The various constituents of the aqueous humour reach the posterior chamber from the
plasma within the capillary network of ciliary processes as follows:
10. Steps/scheme of aqueous formation
1. Formation of stromal pool
• It is the first step in the formation of aqueous
• By ultrafiltration, most substances pass easily from the capillaries of the ciliary
processes, across the stroma and between the pigmented epithelium cells before
accumulating behind the tight junctions of the non-pigmented epithelium
• Protein is to be expected in the filtrate because of the fenestrated nature of the ciliary
capillaries.
11. Steps/scheme of aqueous formation
2. Active transport of stromal infiltrate
• The tight junctions between the non-pigmented epithelial cells create part of blood-
aqueous barrier
• Evidence of active transport occurring across these non-pigmented epithelial cells,
especially in the cell membrane of the lateral interdigitation, comes from observations
of the following in these areas:
• Abundant Na -K-active ATPase, Presence of more mitochondria, Higher adenyl cyclase
activity, Higher specific activity for glycolytic enzymes and, Preferential incorporation of
labelled sulphate into macromolecules (primarily glycolipids and glycoproteins).
12. Steps/scheme of aqueous formation
• Until recently, active aqueous secretion was thought to be carried out solely by the
mitochondria rich non-pigmented epithelium
• However, recent studies have shown that the pigmented epithelium also plays an active
role in the aqueous production
• The basolateral membranes of the pigmented epithelial cells contain numerous Na ion
dependent cotransporters and exchangers and carbonic anhydrase activity is also
present in these cells
• The net effect of these ion transport systems is a low level of Na+ in both epithelial
layers (facilitated by numerous gap junctions between the pigmented and non-
pigmentedcells), a high level of ascorbate and K, and control of intracellular pH.
13. Steps/scheme of aqueous formation
• Following substances from the stromal filtrate are actively transported across epithelial
cells:
• Sodium: Approximately 70% of the sodium found in the posterior chamber is actively
transported by a specific secretory pump. Remaining 30% enters the posterior chamber
by diffusion or ultrafiltration. The active transport of sodium is ATPase-dependent but
does not appear to be related to the concentration of sodium in plasma.
• carbonic anhydrase acts to maintain the proper pH for the Nat-K+-ATPase system.
14. Steps/scheme of aqueous formation
• Following substances from the stromal filtrate are actively transported across epithelial
cells:
• Chloride: A smaller percentage of the chloride ion is actively transported and this
appears to be dependent upon the presence of sodium as well as pH. The remaining
amount of cl- enters into lateral intercellular space by diffusion
• Potassium is transported by secretion and diffusion.
• Ascorbic acid is secreted against a large concentration gradient.
15. Steps/scheme of aqueous formation
• Following substances from the stromal filtrate are actively transported across epithelial
cells:
• Amino acids are secreted by at least three carrier, one each for acidic, basic and neutral
molecules
• Bicarbonate: Its formation is catalysed by carbonic anhydrase. It influence fluid transport
through its effect on sodium, possibly by regulating the pH for optimum active transport
of sodium.
17. Steps/scheme of aqueous formation
3. Passive transport across
• To maintain the balance of osmotic and electrical forces, water, chloride and other small
plasma constituents move into the posterior chamber by ultrafiltration and diffusion
• Sodium is primarily responsible for movement of water into the posterior chamber and
its secretion is a major factor in the formation of aqueous
• secretion of sodium into the posterior chamber is the key event in aqueous formation
18. Steps/scheme of aqueous formation
3. Passive transport across
The following evidences supports importance of sodium in aqueous formation:
• Presence of large concentration of Na+ –K+- activated ATPase especially at the lateral
interdigitations of the non-pigmented epithelium
• Oubain which is an inhibitor of Na+-K activated ATPase effectively reduces aqueous
formation
• Shrinkage of ciliary processes is inhibited by oubain
• Sodium accumulates in the posterior chamber after parenteral administration of radioactive
sodium.
19. Biochemical Composition
• Water. It constitutes about 99.9% of the normal aqueous humour.
• Protein (colloid content):
• In the plasma - 6-7 gm/100 ml, in the aqueous humour - 5-16 mg/100 ml in human
• This is because of the blood-aqueous barrier; and any disruption of this barrier will increase
protein influx
• The albumin/globulin ratio is the same as in plasma, although there are less gamma
globulins.
• Human aqueous has been found to contain IgG and IgM but no IgA and IgA
20. Biochemical Composition
• Plasminogen and its proactivator are present, but none of their inhibitors or other clotting
factors are detectable in the aqueous
• Numerous growth factors including FGF, TGF-B and insulin-like growth factor-I have also
been demonstrated in the aqueous.
• Amino acids. The relative concentration of free amino acids is from 0.08 to 3.14 supporting
the concept of active transport of amino acids
21. Biochemical Composition
Non-colloidal constituents
• non colloidal composition of the aqueous humour is similar to that of plasma
• But have differences, For example, the concentration of ascorbate (vitamin C), pyruvate and
lactate are much higher than in plasma, while those of urea and glucose are much less
• Insulin and steroid. These hormones are also present and enter the aqueous humour by
simple diffusion.
• Prostaglandins. They appear to be actively released into the aqueous by the iris.
• Cyclic-AMP. It has been detected in the aqueous at a level about the same as found in serum
22. Biochemical Composition
Composition of aqueous humour: Anterior chamber versus posterior chamber
• The composition of aqueous humour in anterior chamber differs from that of the aqueous
humour in posterior chamber because it depends not only on the nature of production but
also on the constant metabolic interchange that occurs throughout its intraocular course
• Diffusional exchange across the iris is a significant factor in changing the composition, since
iris vessels are permeable to anions and non-electrolyte
23. Biochemical Composition
Composition of aqueous humour: Anterior chamber versus posterior chamber
• Differences are as follows:
• Bicarbonate concentration in posterior chamber aqueous is higher than in the anterior
• This is because the freshly secreted fluid has a much higher concentration than in the
plasma, but due to diffusion into the vitreous and into the blood from iris and decomposition
by the acids formed by the lens and cornea metabolism, its level decreases in the anterior
aqueous.
24. Biochemical Composition
Composition of aqueous humour: Anterior chamber versus posterior chamber
• Differences are as follows:
• Chloride concentration in the newly formed aqueous of posterior chamber is lower than the
plasma
• Diffusion of chloride from the blood raises the chloride levels of anterior chamber aqueous.
• Ascorbate concentration in posterior aqueous is much higher than the plasma
• The gradient of diffusion for ascorbic acid from the anterior chamber to the blood reduces
the concentration of ascorbic acid in the anterior aqueous
25. Functions of Aqueous Humor
1. Maintenance of intraocular pressure.
• It is the primary function of the aqueous
• By virtue of this, the aqueous humour helps in maintaining the shape and internal structural
arrangement of the eye
2. Metabolic role
• In addition to its role in maintaining a proper intraocular pressure, it also plays an important
metabolic role by providing substrates and removing metabolites from the avascular ocular
structures
26. Functions of Aqueous Humor
In addition to its role in main taining a proper intraocular pressure, it also plays an important metabolic role by
providing substrates and removing metabolites from the avascular ocular structures as follows:
a) Cornea takes glucose and oxygen from the aqueous and releases lactic acid and carbon
dioxide into the aqueous.
b) Lens uses oxygen, glucose, amino acids and potassium from the aqueous and releases
lactate, pyruvate and sodium into the aqueous.
c) Vitreous and retinal metabolism also appears to be associated with the aqueous humour in
that substances such as amino acids and glucose pass into the vitreous from the aqueous.
27. Functions of Aqueous Humor
3. Optical function
• Under normal conditions, aqueous is optically clear
• The cornea-aqueous interface acts as a diverging lens of low power
4. Clearing function
• The aqueous humor serves as a mechanism to clear blood, macrophages, remnants of lens
matter and products of inflammation from the anterior chamber of the eye