Anatomy and Physiology Flashcards
What are cells?
- Smallest part of an organism that retains it characteristics
- Provide structure
- Convert nutrients into energy
- Contain DNA and can replicate
- Consist of organelles
- Made from nucleic acids, proteins, carbohydrates and lipids
What are prokaryotes?
The DNA in the cell is not separated from the cytoplasm
Unicellular
Such as bacteria and archaea
No nucleus or membrane bound organelles
What are eukaryotes?
DNA is separated from the cytoplasm by its own membrane
Most are multicellular but amoebae for example is unicellular
Such as plants and animals
Had a nucleus and membrane bound organelles
Describe the cell membrane
Fluid mosaic model
Phospholipid bilayer
Each layer has:
Polar head (phosphate) groups are hydrophilic and face outwards
Non-polar lipid tails which are hydrophobic and face inwards
Semipermeable
How can substances cross the cell membrane?
Diffusion
Facilitated diffusion
Osmosis
Active transport
Simple diffusion across a cell membrane?
Solute moved through permeable membrane from an area of high concentration to an area of lower concentration
No energy required
Non-polar gases such as O2 and CO2
Hydrophobic molecules such as steroid hormones, lipid soluble vitamins and small lipid soluble drugs
Large polar molecules are repelled by the hydrophobic interior of lipid bilayers so cannot cross by diffusion
4 principles of the modern cell theory
All living things are made up of cells
New cells are formed by the division of pre-existing cells
Cells contain genetic material, which is passed on from parent to daughter cells
All metabolic reactions take place inside the cell
Organisms made up of just one cell
Unicellular
Organisms made up of more than one cell
Multicellular
Differences between prokaryotic cells and eukaryotic cells
Prokaryotes do not have a nucleus or membrane bound organelles
Eukaryotes have genetic material in the nucleus whereas prokaryotes have a main chromosome of DNA called a nucleoid and small rings of DNA called plasmids
Examples of eukaryotes
Animals, plants, fungi
Examples of prokaryotes
Bacteria
Differences between plant and animals cells?
Plant cells also have a cellulose cell wall, plasmodesmata, chloroplasts, large permanent vacuoles but they do not have centrioles
Functions of the cell wall
Provide support for the cell by allowing it to become turgid
Provide mechanical strength to the cell
They are freely permeable to water and substances in solution
The cell walls of adjacent cells are glued together by?
Middle lamella, a jelly like substance made up of calcium pectate and magnesium pectate
What membrane is bound by the tonoplast?
The vacuole in plant cells
What does the vacuole of a plant cell contain?
Cell sap which is a solutions of sugars, amino acids, mineral salts and waste chemicals dissolved in water
Functions of the plant vacuole?
Water enters the vacuole by osmosis
Act as stores for foods like sugar and amino acids
Accumulate waste products
Some contain coloured pigment to give the plant colour
What does the nucleus contain?
DNA
What is the nucleus surrounded by?
Nuclear membrane, it is a double membrane with space in between
What is the name of the material inside the nucleus?
Nucleoplasm. It contains chromatin (made up of DNA) attached to proteins called histones
What does the nucleolus make?
rRNA and assembles ribosomes
Functions of the nucleus?
DNA contains genetic information for synthesis of proteins
Genetic material of the nucleus controls metabolism of the cell
Produces new chromosome material at cell division so each daughter cell is genetically identical
Why does haemoglobin not contain a nucleus?
To save space to enable them to carry more oxygen
What are the fluid filled spaces in the endoplasmic reticulum called?
Cisternae
Function of the cisternae?
A system of passages to allow materials to be transported throughout the cell
Rough endoplasmic reticulum contain ……. on its surface?
Ribosomes
Main function of roughy endoplasmic reticulum
To package and transport proteins made by ribosomes
Proteins are transported via the cisternae to vesicles to the Golgi body
RER can also produce pieces of new plasma membrane for the cell
Function of smooth endoplasmic reticulum
Synthesis of lipids and steroids
Transport of material through the cell in vesicles
Where are ribosomes found?
Free in the cytoplasm or on the rough endoplasmic reticulum
Ribosome function?
Protein synthesis
How are Golgi bodies formed?
Small pieces of rough endoplasmic reticulum are pinched off the ends to form small vesicles. These vesicles then join together
Functions of the Golgi body?
Modification of proteins and lipids from ER
Packaging finished proteins into vesicles for transport
Production of lysosomes
How are lysosomes formed?
When small vesicles are pinched off the Golgi body
Functions of lysosome?
Release enzymes called lysozyme that destroy worn out organelles
Digest material that has been taken into the cell this is call phagocytosis
Release their enzymes outside of the cell to destroy other cells this is called a exocytosis
Can cause the cell the self-destruct called autolysis
Functions of the mitochondria’s double membrane
Outer membrane control entry and exit of material
Inner membrane forms many folds called cristae where ATP is made
Functions of the matrix of the mitochondria
Contains enzymes needed for respiration. Also contains DNA and ribosomes so mitochondria can replicate themselves when the cell divides
Main function of the mitochondria
Aerobic respiration, converting glucose to a form of energy that can be used by the cell
Structure of the chloroplast?
Double membrane
Inner membrane forms stacks of flattened stacks called thylakoids, each stack is called a granum
Fluid cavity called stroma
Can contain starch grains (amyloplasts)
What is the cytoskeleton made up of?
Fibrous proteins such as microtubules, microfilaments and intermediate filaments
Functions of the cytoskeleton
To provide and internal framework to support the cell
Organise and move organelles within the cell
Move the whole cell
Construct the spindle during cell division
Provide the components of cilia and flagella
Microtubules are made up of?
Tubulin
Microfilaments are made up of?
Actin
Structure of the cell membrane?
Semi-permeable to control movement of substances in and out of the cell
Bilayer of phospholipids
The phospholipid bilayer has ……. heads and …….. tails
Hydrophilic heads and hydrophobic tails
How do substances enter the nucleus?
Through the nuclear pores
What is chromatin?
Long strands of DNA wrapped around purple histone proteins to organise the DNA and keep it compact in the nucleus
The nuclear envelope is attached to?
The rough endoplasmic reticulum
Ribosomes are made up of?
Two subunits
What type of ribosomes do eukaryotes have?
80s and 70s within mitochondria and chloroplasts
What type of ribosomes do prokaryotes have?
70s
Why do mitochondria and chloroplasts replicate their own DNA?
They were originally separate prokaryotes but evolution saw them become part of the eukaryote cell
What side of the Golgi does the vesicle from the ER arrive?
Cis face
What side of the Golgi does the vesicle containing the finished protein leave?
Trans face
Function of microtubules?
Enables organelles to move through the cytoplasm, aided by motor proteins
Forms the spindle during cell division
Part of the centrioles, cilia and flagella
Function of microfilaments?
Enables cells to move and change shape e.g. when cells divide
Function of the intermediate filaments?
Mechanical strength
Structure of the centriole?
Part of cytoskeleton
Found as a pair at right angles to each other
Arranged in a ring of 9 sets of triplet microtubules
No membrane
Function of centrioles?
Organise the spindle during cell division
Make cilia and flagella
Structure of cilia?
Part of cytoskeleton
Made of microtubules- 9 pairs plus a pair in the middle, 9+2 formation
Function of cilia?
Waft things along, e.g. mucus in respiratory tract or egg in Fallopian tube
Sense chemical changes in environment
The only animal cell that has flagella?
Sperm cell
Structure of flagella in animal cells?
9+2 formation of microtubules
Only one or two per cell
Function of flagella in animal cells?
Allow the cell to move with a whip-like movement
What are prokaryotic flagella made of?
Protein called flagellin
Difference in function of prokaryotic and eukaryotic flagella?
Prokaryotic flagella moves the whole organism in a propeller like movement whereas eukaryotic flagella just moves that cell in a whip-like movement
Function of the chloroplasts?
Photosynthesis, thylakoids contain chlorophyll to absorb sunlight
What is a plant cell wall made of?
Cellulose, carbohydrate in a mesh
What is a fungi cell wall made of?
Chitin, containing sugars and nitrogen
What is a bacteria cell wall made of?
Peptidoglycan, containing proteins and sugars
Where does aerobic respiration in a prokaryote take place?
Not proven for certain but it is believed to be in the mesosome, a folded area of surface membrane
Where is the DNA in a prokaryote?
Circular DNA in the nucleoid region, not membrane bound. Can also be in small plasmid rings in cytoplasm
How can plasmids influence antibiotic resistance?
Antibiotic resistance genes are often found in plasmids and plasmids can be moved from one prokaryote to another
Function of the cell capsule?
Keeps the cell hydrated as it retains moisture
Can help the cell to evade recognition by the host e.g. pathogens
Function of Peroxisome?
Similar to lysosomes but contain oxidative enzymes. They digest fatty acids, ethanol and amino acids
Structure of Peroxisome?
Small membrane bound
Contains oxidative enzymes
What is mitosis used for?
Growth
Repair
Asexual reproduction
What is meiosis used for?
Gamete production
Genetic variation
What does mitosis produce?
Two genetically identical diploid daughter cells
What does meiosis produce?
Four genetically unique haploid daughter cells
What does diploid mean?
Two copies of each chromosome
What does haploid mean?
One copy of each chromosome
How many chromosomes do humans have?
46 (23 pairs)
What sex chromosomes do males have?
XY
What sex chromosomes do females have?
XX
What is a pair of chromosomes called?
Homologous pair
What is the name of the stage in mitosis when the cell is not dividing?
Interphase
What are the four stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What is the division of cytoplasm called?
Cytokinesis
What happens at interphase?
DNA replicates
Organelles replicate
Centrioles replicate
Chromatin is uncoiled
What holds the homologous chromosomes together?
The centromere
What happens in prophase of mitosis?
Chromatin condenses to form chromosomes
Nuclear envelope breaks down
Replicated centrioles move to opposite poles
Spindle fibres (tubulin) begin to form at poles
What forms around the centromere and attaches to the spindle fibres during mitosis?
A protein complex called the kinetochore
What happens during metaphase of mitosis?
Kinetochores attach to spindle microtubules
Chromosomes line up along the equator
What happens in anaphase of mitosis?
Sister chromatids are pulled apart and now called chromosomes
Chromosomes move towards opposite poles of the cell
What makes the chromosomes move the opposite poles during anaphase?
The microtubules shortening my removing tubulin subunits, called depolymerising
What happens in telophase of mitosis?
Chromosomes have reached the poles and begin to decondense so nucleolus reforms
Nuclear envelope forms around chromosomes at each pole
Spindle breaks down
Process of cytokinesis in animal cells?
The cell membrane pinches in the middle to form a cleavage furrow The cytoskeleton (microfilaments) then continues to pull the membrane inwards
Process of cytokinesis in plant cells?
Cannot form cleave furrow due to cell wall
Golgi vesicles contain components needed for a new cell wall assemble across the equator (cell plate) and fuse to make a new membrane
New cell walls form on either side of the membrane
Where does meiosis take place in humans?
Ovaries or testes
Why do gametes have half the normal chromosome number?
To fuse with another gamete to produce a zygote with the normal number of chromosomes
How many times does the cell divide in mitosis?
Once
How many times does the cell divide in meiosis?
Twice
What addition processes happen in prophase 1 of meiosis compare to mitosis?
Members of homologous pairs find each other and lie close together (process called synapsis)
Non-sister chromatids become so close that they can overlap (called chiasmata) this can lead to crossing over of genetic material
What is different about metaphase 1 of meiosis compare to mitosis?
The chromosomes line up along the equator in homologous pairs
How does genetic variation happen through meiosis? (4)
Chiasmata and crossing over of genetic information
Which random arrangement of maternal/paternal chromosomes called independent assortment in metaphase 1
Orientation of each chromosome in metaphase 2
Random fusion of the gametes produced by meiosis
How is anaphase 1 in meiosis different to mitosis?
Sister chromatids are not separated as there is no division of the centromere
Simple diffusion across a cell membrane
Solute moves through permeable membrane from high concentration to low concentration. No energy required. E.g. non polar gases:O2, CO2 Hydrophobic molecules: steroid hormones, lipid soluble vitamins and small lipid soluble drugs
Facilitated diffusion across a cell membrane
Mediated by membrane proteins, lowering the activation energy for polar compounds and ions Process is specific Used for materials that the cell needs rapidly Saturable as there are a limited number of carrier proteins
Active transport across a cell membrane
Requires energy to move a solute from a low concentration to a high concentration Mainly uses ATP from hydrolysis Responsible for creating and maintaining ion concentration gradients across the plasma membrane and the membranes of internal organelles E.g. large uncharged molecules such as glucose and ions
Other cell entry processes for particles and macromolecules
Endocytosis- particles moved into a cell by enclosing them in a vesicle made out of plasma membrane
Types of endocytosis?
Phagocytosis: used for large particles such as cells and cell debris. The vesicle is taken in and fuses with a lysosome which will break it down to its basic components Pinocytosis: the cell takes in small amounts of extracellular fluid so the cell can take any nutrients or molecules present in it Receptor-mediated endocytosis: receptors on cell surface capture specific target proteins triggering endocytosis. Usually for rarer molecules that are needed but sometimes virus’ can gain entry this way.
What are nucleic acids?
DNA and RNA
Polynucleotides made of nucleotide monomers
Each nucleotide has a nitrogenous base bonded to carbon-1 of a pentose sugar and phosphate group (which has a negative charge causing acidity) bonds to carbon-5 of pentose sugar
Difference between pentose sugar of DNA and RNA?
DNA: deoxyribose sugar, carbon-2 has a hydrogen bonded to it
RNA: ribose sugar, carbon-2 has a OH group bonded to it
Types of nitrogenous bases?
Purines: adenine and guanine
Pyrimidines:
DNA: thymine and cytosine
RNA: uracil and cytosine
Which bases can hydrogen bond?
Cytosine and guanine
DNA: adenine and thymine
RNA: adenine and uracil
How are polynucleotides formed?
Condensation reaction creating phosphodiester bond (strong covalent) between OH group of phosphate group and OH group of carbon-3
Each chain has a 5-prime end (where carbon 5 is attached to phosphate group) and a 3-prime end (where carbon-3 of the pentose sugar is nearest the end)
In DNA a second chain will run anti parallel (3-5 rather than 5-3) so nitrogenous bases are close to each other and hydrogen bonds will form between them (two bonds between a and t) (three bonds between g and c)
DNA curls up into a double helix to save space
Difference between RNA and DNA?
Different pentose sugar
DNA double strand, RNA single strand
DNA A and T, RNA A and U
Differences between purines and pyrimidines?
Purines are bigger
How does DNA replicate?
Called semi-conservative replication
1) helicase enzymes separate the DNA strands. The point at which two strands are separated is called replication fork
2) each strand is kept apart from single-strand bonding proteins
3) enzyme called DNA polymerase uses each patent strand as a template and adds the complementary base pairs in a 3 to 5 direction this creates the leading strand which grows continuously
4) the lagging strand is built away from the replication form in a 5 to 3 direction. It grows discontinuously in small sections called Okazaki fragments which are joined together by DNA ligase
5) helicase unwinds DNA little bit more and the previous steps happen again
6) there can be multiple replication bubbles
What is the origin of replication?
Begins at a specific nucleotide sequence
Enzymes involved in DNA replication?
Topoisomerase: untwists the DNA ahead of the replication forks to relieve the strain
Helicase: unwinds the double helix at replication forks, breaking hydrogen bonds between base pairs
Single-stranded binding proteins: keep the two parental strands separate
Primase: synthesises one short strand (10 nucleotides) called a RNA primer, in the 5 to 3 direction using the parental DNA strand as a template to ‘start of’ for DNA polymerase
DNA polymerase III: can only add to an existing chain in the 5 to 3 direction. Adds DNA nucleotides to the 3 end of RNA primer
DNA polymerase I: replaces RNA primer with DNA in both leading and lagging
DNA ligase: joins Okazaki fragments
What is transcription?
Making a RNA copy strand of gene required as a template
Transcription process?
At the promoter, a DNA sequence that determine which strand will be transcribed and in what direction. Transcription factors bind to promoter and enable RNA polymerase II to bind. This unwinds the double helix, separates the DNA strands and synthesises the pre-mRNA. The addition of nucleotides is called elongation.
DNA double helix reforms and pre-mRNA peels away
There is a polyadenylation signal (AAUAAA) which cause the transcript to be cut releasing the RNA polymerase and pre-mRNA
What is RNA processing?
Modification of the pre-mRNA to produce mRNA for translation
Step 1) end processing
Step 2) splicing
What is end processing?
At 5 prime end there’s a modified guanine added (5 prime cap)
At the 3 prime end there are 50-250 adenine added (poly-A tail)
These protect the transcript from enzymes which would degrade the transcript
They act as signals and to move the transcript through the nuclear pore for translation
The 5 prime cap binds the transcript in the cytoplasm to the ribosome
What is splicing?
Introns (non-protein coding) removed and exons (protein coding) joined together
Average mRNA is 95% shorter that pre-mRNA
Takes place in spliceosome (in the nucleus)
Small nuclear RNAs bind to the ends of introns by complementary base pairing
Small RNAs are ribozymes (RNA molecules that function as enzymes)
Alternative splicing (only joining some exons) can produce a variety of proteins
Introns contain regulatory sequences
What is translation?
Decoding the sequences of bases in the mRNA and transforming them into a sequence of amino acids
It is read 3 bases at a time (called a codon)
Start codon is AUG at 5 prime end
Stop codon is at the three prime end
What is the genetic code?
Triplet code (codons)
Universal
Non-overlapping
Start codon sets the reading frame
61 codons for 20 amino acids so there can be more than one codon for a particular amino acid (degenerate)
Not ambiguous
What is tRNA?
Transfer RNA
A single strand of RNA
Hydrogen bonds can form between complementary base pairs forming a unique (cloverleaf) shape
At the bottom the three bases are called an anti-codon and they bind by complementary base pairing to the codons on mRNA
Anti-codon is specific to an amino acid
Translation process?
mRNA lays between the two subunits of the ribosome and moves across it
tRNA binds to the codons on the mRNA by complementary base paring with their anti-codons
The tRNA brings along the amino acids they carry and these are close enough to each other so peptide bonds can form between adjacent amino acids
The now empty tRNA goes to the cytoplasm to collect another amino acid
Translation stops when a stop codon is present, a release factor recognises the stop codon and a water molecule is added to the chain
What is health?
A state of complete physical, mental and social well-being and not merely the absence of disease or drug infirmity
What are the classifications of diseases?
Topographic - subcategories such as gastrointestinal, vascular Anatomic- specific organ it affects e.g. heart disease Physiological- caused by a specific disorder such as metabolic, respiratory Etiological- based on cause, such as viral, fungal or bacterial Juristic- legal circumstances of death Epidemiological- disease incidence, control and distribution Pathological- the nature of disease process. Such as inflammatory
What is process of apoptosis?
Programmed cell death: 1) cell shrinks and develops blebs on surface 2) DNA in nucleus is cut into small pieces 3) some organelles break down 4) cell splits up into small parts that are packed into membranes 5) vesicles show phosphatidylserine on surface which lets phagocytes bind and destroy it
Why do cells undergo apoptosis?
Some cells need to be deleted during development Some cells are abnormal and could hurt the rest of the organism To maintain balance Can destroy cancer cells
What is necrosis?
Accidental cell death: The cell membrane can no longer control the passage of water and ions so it will swell and the contents leak out. This causes inflammation in the surrounding tissue. Caused by infection, hypoxia, heat, cancer and injury
What is hypertrophy?
Increased tissue size due to enlargement of cells (due to an increase in organelles and structural proteins) Physiological reasons: increased muscles mass through sport, uterus enlargement due to hormonal changes Pathological reasons: hypertrophic cardiomyopathy due to arterial hypertension
What is hyperplasia?
Controlled proliferation in the form of elevated reproduction rate. A higher number of cells so a higher tissue mass. Physiological reasons: reactive bone marrow hyperplasia in haemolytic anaemia Pathological: BPH caused by androgen and oestrogen stimulation
What can cause cell injury?
Ischaemia and toxins can cause an increase in cytosolic calcium concentration which can active a number of enzymes with harmful effect Mitochondria can also become damaged by the calcium increase
Examples of reversible cell injury?
Cell swelling Fatty change Detachment of ribosomes Plasma membrane blebbing Loss of microvilli Mitochondrial swelling
What is the largest organ of the body?
Skin (15%) total adult body weight
Functions of the skin?
Protects against external physical, chemical and biological influences as impermeable Prevents again dehydration (thermoregulation) Lines the body’s surface Can secrete antibodies and lysosomes- immunity Can sense environment- pain, temperature
Layers of the skin?
Epidermis Dermis Subcutaneous tissue
Layers of epidermis?
Stratum germinativum (horny cells including basal cell layer) Stratum spinosum (squamous cell layer) Stratum granulosum (granular cell layer) Stratum corneum (cornified cell layer)
Stratum germinativum structure?
Column shaped keratinocytes attached to basement membrane from dermis Cells in each single layer adhere to each other Have dark stained oval nuclei Have melanocytes which produce melanin
Stratum germinativum function?
Site for active cell division Stem cells in this layer have long life span Conditions like wounds stimulate division of stem cells and increase cell number in the epidermis Where we get skin colour from- darker skin has more melanin not necessarily melanocytes
Function of keratinocytes?
Produces cytokeratin (keratin) Gives skin tough outer layer as it gets to the top
Stratum spinosum structure?
5-10 cells thick Spinous cells linked by desmosome Cells become flatter as they progress through this layer Some cells may be spiney/ star shaped due to loss of moisture but desmosomes keep them connected Contains langerhans cells
Stratum spinosum function?
Desmosome links provide resistance to physical stress Langerhans cells look for pathogens to phagocytose them- they can travel to other layers if needed
Stratum granulosum structure?
Keratinocytes contain granules called keratohyaline granules 1-3 cell layer- more on palms and soles
Stratum granulosum function?
Keratinhyaline granules contain proteins that help to handle the keratin Also release lamellar bodies that form the skins lipid impermeable layer
Stratum corneum structure?
Cells are now dead- no nuclei or other organelle Stacked layers of keratinocytes as they progress through the layer
Stratum corneum function?
Random/ continuous shedding of top dead cells Provide protection, prevent water loss, prevent invasion of pathogens Cells in the middle have higher capacity for water binding due to the high concentration of free amino acids in cytoplasm compared to deeper layers
Dermis layer structure?
Connective tissue - lots of other proteins such as actin and collagen Connective tissue is thinner at top of dermis Top of dermis contains capillaries Contain nerve endings Bottom of dermis contains glands Contain hair follicles with arrector pili muscles attached to them
Dermis layer function?
Connective tissue holds things together Capillaries deliver oxygen and nutrients to both dermis and epidermis Sense pain and touch Glands secrete contents to upper layers of skin via duct
Arrector pili muscle function?
Attached to hair follicles When contracts it allows hairs to stand up straight when cold or scared
Subcutaneous tissue layer structure?
Lots of fat layers Varies in thickness depending on location Lipocytes produce leptin
Subcutaneous tissue layer function?
Fat absorbs shock and insulates the tissue Leptin regulates body weight
Melanocytes structure and function
Dendritic cell Organelle called malacosoma produces melanin which is transferred to keratinocytes UV light stimulates increase in melanogenesis which is where there is an increased transfer of melanosome to keratinocytes and they aggregate towards the nucleus surface Allowing the cells ability to protect the DNA in nuclei from radiation
Merkel cell structure and function?
Oval shaped type-1 mechanoreceptors located in high sensitivity sites Attached to basal keratinocytes by desmosomal junctions High number= increased tactile resolution and sensitivity
Structure and function of langerhans cells?
Derived from bone marrow and involved in T-cell response Migrate to suprabasal position during embryonic development and circulate and repopulate epidermis throughout life 2-8% of epidermis cell population
Dermal-epidermal junction structure and function?
Porous basement membrane junction between dermis and epidermis Allows exchange of fluid Holds two layers together Basal keratinocytes and basal lamina are part of junction
Nail structure?
Nail root attached to epidermis Essential part of epidermis Made of keratin packed into dead cells Fingernails grow faster than toe nails
Nail function
Provide protection to finger tips Enhance sensation Grasp small objects Slow growth rate of toe nails can provide historical medical issue such as arsenic poisoning can cause meese line on toenails
Hair structure
Grows from dermis Hair follicle in lower dermis Made from dead cells with keratin Arrector pili in upper dermis No more hair follicles are added after birth
Hair function?
Protection from environmental elements Distribution of sweat gland secretion Psychosocial role in society
Hair growth cycle?
Anagen: active stage, lasts about 3-5 years in scalp, grows at 0.33mm/day Catagen: two week period of involution resulting in club hair formation after apoptosis of many cells in the outer root sheath Telogen: lasts 3-5 months on scalp, hair then pushed out by growing anagen hair shaft
What are vater-Pacini corpuscles?
Large nerve-end organs that generate sense of pressure. Mainly located in deeper parts of dermis of genitalia and nipples
Eccrine sweat gland structure?
Band of epithelial cells growing down from epidermal ridge Three parts: Intra-epidermal spiral duct Straight dermal portion Coiled secretory duct
Eccrine sweat gland function?
Thermoregulation
Apocrine sweat gland structure?
Ductless so do not secrete directly onto skin surface Mainly in regions of axillae and perineum Develop just before puberty
Apocrine sweat gland function?
Scent release for sexual attraction, territorial marker or warning signals
What is the main function of the endocrine system?
Maintains homeostasis through the use of hormones
What are hormones?
Signalling molecules
How do hormones work?
1) secreted by an endocrine cell/organ into the extracellular fluid 2) hormone diffuses into the vasculature where it can circulate throughout the body 3) hormone diffuses out of the vasculature 4) hormone binds to a specific receptor within or on a cell of the target organ 5) this triggers a response
What effects can hormones exert?
Rate of enzymatic reactions Transport of ions and molecules across cell membranes Gene expression and the synthesis of proteins Electrical signalling pathways
Where is the thyroid gland found?
Neck
What does the thyroid gland secrete?
Thyroxine Calcitonin
It hat does thyroxine do?
Regulates metabolism
What does calcitonin do?
Inhibits release of calcium from bones
Where are the parathyroid glands found?
Dorsal aspect of the thyroid gland, in the neck
What do the parathyroid glands secrete?
Stimulate the release of calcium from bones
Where are the islet cells?
In the pancreas
What do islet cells secrete?
Insulin and glucagon
What does insulin do?
Decreases blood sugar by promoting the uptake of glucose by cells
What does glucagon do?
Increase blood sugar by stimulating the breakdown of glycogen in the liver
What do the testes secrete?
Testosterone
What does testosterone do? (males)
Regulates sperm cell production and secondary sex characteristics
What do the ovaries secrete?
Estrogen and progesterone
What does estrogen do?
Stimulates egg maturation and controls secondary sex characteristic
What does progesterone do?
Prepare the uterus to receive a fertilised egg
What does the adrenal medulla secrete?
Epinephrine
What does epinephrine do?
Stimulates fight or flight response
What does the adrenal cortex secrete?
Glucocorticoids Aldosterone Testosterone
The function of glucocorticoids?
Part of stress response, increases blood glucose levels and decreases the immune response
The function of aldosterone?
Regulates sodium content in the blood
The function of testosterone? (both sexes)
Adult body form (greater muscle mass), libido
Where is the pineal gland found?
In a part of the brain called the epithalamus
What does the pineal gland secrete?
Melatonin
The function of melatonin?
Sleep cycles, reproductive cyles in many mammals
Classification of endocrine disorders?
Hyperfunction Hypofunction
Hyperfunction meaning?
Increased secretion of the hormone and, therefore, an increased concentration in the circulating blood
Hypofunction meaning?
Decrease secretion of hormone and therefore a decreased concentration of hormone in the circulation blood
Example of hypofunction?
Hypothyroidism Hypopituitarism Diabetes mellitus
Examples of hyperfunction?
Gigantism (acromegaly) Hyperthyroidism
What can hormones be?
Proteins/peptides/glycoproteins Steroids Amino acid derivatives
Examples of peptide hormones?
Insulin Glucagon Prolactin ACTH Gastrin parathyroid hormone
Examples of steroid hormones?
Cortisol Aldosterone Estrogen Progesterone Testosterone
Examples of amino acid derivative hormones?
Adrenaline Thyroxine Triiodothyronine
How are peptide hormones synthesised?
As prohormones that require further processing to activate
How are steroid hormones synthesised?
In a series of reactions from cholesterol
How are amino acid derivative hormones synthesised?
From the amino acid tyrosine
How are peptide hormones stored?
In vesicles (regulatory secretion)
How are steroid hormones stored?
Released immediately (constitutive secretion)
How are amino acid derivative hormones stored?
Stores before release but the storage mechanism varies
Solubility of peptide hormones?
Most are polar and water soluble Can travel freely in the blood
Solubility of steroid hormones?
Generally nonpolar Require carrier proteins to travel in the blood
Solubility of amino acid derivative hormones?
Some are polar, e.g. Adrenaline Others must be protein bound
How do peptide hormones bind to receptors?
Bind to receptors on the cell membrane and transduce signal via the use of second messenger systems
How do steroid hormones bind to receptors?
Bind to intracellular receptors to change gene expression directly
How do amino acid derivative hormones bind to receptors?
Adrenaline acts on membrane receptors whilst thyroid hormones act directly on nuclear receptors
Effects of peptide hormones?
Often fast onset of transient changes in protein activity, though gene expression changes can occur
Effects of steroid hormones?
Alterations in gene expression, slower onset but longer duration than peptide hormones
Effects of amino acid derivative hormones?
Adrenaline functions like peptides, thyroid hormones function like steroids
What is the lymphatic system?
A network of vessels that convey lymph Returns plasma-derived interstitial fluids to the bloodstream An important role within the immune system
What is lymph?
A clear-to-white fluid of white blood cells
Functions of the lymphatic system?
Defends against pathogens Develops the bodies immunity by making lymphocytes Remove excess fluid of the body Absorption and transport of fats to the bloodstream
What is the lymphatic system divided into?
Primary lymphoid organs Secondary lymphoid organs Tertiary lymphoid organs
What are the primary lymphoid organs?
Bone marrow Thymus
What happens in the bone marrow?
Hematopoiesis
What happens in primary lymphoid organs?
Immune cells develop
What happens in the thymus?
T-lymphocytes complete maturation Generate unique antigen receptors They are selected on their reactivity to self MHC-peptide complexes Most T-lymphocytes die in the thymus
What do the secondary lymphoid organs do?
Where the immune system is initiated and distributed throughout the body All have distinct regions of T-cell and B-cell activity and develop lymphoid follicles
What are lymphoid follicles involved in?
Development and selection of B-cells
What are the secondary lymphoid organs?
Lymph nodes Spleen Mucosa-associated lymphoma tissue
Where is mucosa-associated lymphoid tissue found?
Tonsils Peyer’s patches (small intestine) Appendix Lymphoid follicles in mucous membranes
Spleen function?
Organises the immune response against the bloodborne pathogens
What supplies the spleen with antigens?
The splenic artery
What is the red pulp in the spleen?
Destroyed red blood cells
What is the white pulp in the spleen?
Peri-arteriolar lymphoid sheaths with T-cells and B-cells
Marginal zone of the spleen?
A trap for antigens
Lymph node function?
Regulates the immune system and is the first organised structure to face antigens
Lymph node anatomy?
Connect with blood and lymph vessels Packed with lymphocytes, macrophages and dendritic cells
Regions of the lymph nodes?
Cortex Follicle Para-cortex Medulla
What does the cortex region of the lymph node contain?
It contains B-lymphocytes, macrophages and follicular dendritic cells
What does the follicle region of the lymph node do?
It is a microenvironment to support the development of B-cells
What does the para-cortex region of lymph nodes contain?
T-lymphocytes and dendritic cells that have migrated from the tissue
What does the medulla region of the lymph node do?
An exit for lymphocytes
What does mucosa-associated lymphoid tissue do?
Organises the response to antigens entering mucosal tissue
What does mucosal-associated lymphoid tissue contain?
T and B cell zones Lymphoid follicles
Where are examples of organised mucosal-associated lymphoid tissues?
Tonsils Peyer’s patches Adenoids
What is gut-associated lyohoid tissue?
A barely organised cluster of lymphoid cells
What are M-cells?
Specialised epithelial cells of the mucosa-associated lymphoid tissues that transport antigens across the epithelium
What is tertiary lymphoid tissue?
Found at chronic sites of inflammation Organised accumulation of T and B cells
What causes swollen lymph nodes?
The result of activated B and T cells
Genetics definition?
Biological science that deals with hereditary and related variation between living organisms
Chromosomes definition?
Protein structures inside the nucleus, made of a molecule of parents DNA that contains the hereditary information.
Gene definition?
A segment of DNA sequence that codes for a specific trait
Genome definition?
The set of genes
Hereditary definition?
Passing parents traits to the next generation through reproduction
Mitosis definition?
The process by which a cell separates it’s duplicated genome into two identical halves
Meiosis definition?
The process that transforms one diploid into four haploids
Dominant allele definition?
An allele whose trait is always present
Recessive allele definition?
A train that is masked by a dominant allele
What is codominance?
Ah inheritance relationship in which neither of the two alleles of the same gene totally mask the other
Allele definition?
One pair of genes that appears at a specific location on certain a chromosome and control the same phenotype
Homozygous allele?
Two of the same allele for the same characteristic
Heterozygous allele?
Two different alleles for the same characteristic
Phenotype definition?
Physical appearance of the genetic makeup
Genotype definition?
The genetic make up
Who discovered Mendelian genetics?
Gregor Mendel
Three laws of Mendelian inheritance?
Segregation Independent assortment Dominance
Explain the segregation law of Mendel inheritance?
alleles that make up a gene separate from each other during the formation of gametes. So either gamete has an equal probability of obtaining either member of the gene pair
Explain the independent assortment law of Mendel inheritance?
Usually only true in simpler organisms The way in which alleles from different genes separate and then recombine is unconnected to other genes
Explain the dominance law of Mendel inheritance?
One allele is dominant and one is recessive.
What is autosomal dominance?
The phenotype will be observed whether the individual has one or two copies of the allele
What is autosomal recessive?
The phenotype will only be observed if both alleles are recessive.
What is sex-linked inheritance?
Traits other than gender found on the X chromosome. Males only receive one copy whereas females receive two. This is why some diseases may be more common in males. Such as muscular dystrophy, colour blindness and haemophilia
Name four monogenetic Mendelian autosomal recessive disease?
Phenylketonuria Cystic fibrosis Sickle cell anaemia Albinism
Name five monogenetic Mendelian autosomal dominant diseases?
Huntington’s Myotonic dystrophy Hypercholesterolemia Neurofibromatosis Polycystic kidney diseae
Name two monogenetic Mendelian X-linked recessive disease?
Haemophilia A Muscular Dystrophy (Duchenne type)
Name two monogenetic Mendelian X-linked dominant disease?
Rett’s syndrome Hypophosphatemic rickets
Name one monogenetic Mendelian Y-linked disease?
spermatogenic failure
What is a non-mendelian inheritance pattern?
does not follow the laws of autosomal inheritance Traits can be produced by gene interactions and gene-environment The interactions are known as complex or multifactorial Can include: mitochondrial inheritance, instability of repetitive sequences and genomic imprinting
Name two non-mendelian genetic diseases?
Fragile X syndrome Friedreich ataxia
Phenotype of fragile-X syndrome?
mental deficit Autism High voice Behavioural problems Macrocephaly Long face Big ears Second most common cause of inborn mental retardation and down syndrome
Causes of fragile-X syndrome?
a
Cause of Freidreich ataxia?
homozygous in the first intron of frataxin that causes lower mRNA and protein levels More trinucleotide repeats are produced
What is a genetic mutation?
An alteration in the DNA sequence
Types of genetic mutations?
Silent mutations Nonsense mutations Missense mutations
What is a silent mutation?
A change in the DNA sequence but it still code for the same amino acid
What is a nonsense mutation?
A change in DNA sequence that leads to an early stop codon
What is a missense mutation?
A change DNA sequence that then codes for a different amino acid
How is dihydrotestosterone produced?
From testosterone by the enzyme 5a-reductase
What does dihydrotestosterone do?
Sexual differentiation in embryo and subsequent sexual development and maintenance of masculine characteristics
Where does dihydrotestosterone work?
Locally
Where is testosterone made?
In the testes
What does testosterone do?
Generation of sperm and development and maintenance of masculine characteristics
Where does testosterone work?
Systemically and locally
What does oestradiol do?
Controls the development and maintenance of feminine characteristics and stimulate the growth of the egg follicle
What does progesterone do?
Stimulates the growth of the endometrial lining of the uterus in order to prepare it for pregnancy
What does the hypothalamus secrete (reproductive endocrinology)?
Gonadotropin-releasing hormone (GnRH)
What does the anterior pituitary secrete (reproductive endocrinology)?
Follicle stimulating hormone (FSH) and Luteinising hormone (LH)
What is GnRH?
Gonadotropin-releasing hormone
What is FSH?
Follicle stimulating hormone
What is LH?
Luteinising hormone
Male gonads?
Testes
Female gonads?
Ovaries
Principle functions of gonads?
Produce steroidal sex hormones Gametogenesis
Average age for onset of puberty?
Males 12 years Females 11 years
What causes puberty?
High pulses of gonadotropin-releasing hormone
What does the release of GnRH do?
Stimulates the release of FSH and LH from the pituitary gland
Hormonal regulation of the male reproductive system?
Hypothalamus secretes GnRH -> GnRH causes pituitary gland to secrete FSH and LH -> FSH acts on testes to begin spermatogenesis and LH to produce testosterone -> testosterone and inhibin control release of GnRH and FSH/LH through a negative feedback mechanism
What is inhibin?
A peptide hormone that controls the release of GnRH and FSH/LH
Main parts of the testes?
Seminiferous tubules Rete testis Epididymis Vas deferents
What do the seminiferous tubules do?
Site of spermatogenesis Make up 80% mass of the testes
What do the rete testis do?
Sperm are concentrated here
What does the epididymis do?
Store sperm
What does the vas deferens do?
It is duct that transports sperm from the epididymis to the ejaculatory ducts
Two main types of cell in the seminiferous tubules?
Leydig cells Sertoli cells
What do leydig cells do?
Respond to LH to produce testosterone
What does testosterone do to the Sertoli cells?
Stimulates the production of factors that promote spermatogenesis
Where are the leydig cells located?
Surround the seminiferous tubules
Where are the Sertoli cells located?
Beneath the basement membrane of the seminiferous tubules and form the blood/testes barrier
What do Sertoli cells do?
Provide nutrients and factors to developing germ cells Respond the FSH to produce chemical signals for proliferation and differentiation of germ cells Secrete inhibin Secrete seminal fluid which contains androgen-binding protein (ABP) that binds testosterone to maintain a high concentration in tubules
What is ABP?
Androgen-binding protein It binds testosterone to maintain a high concentration in the seminiferous tubules
Process of spermatogenesis?
Germ cells called spermatogonia divide mitotically and meiotically and differentiate into spermatozoa Germ cells move away from the basement membrane, towards the lumen of seminiferous tubules
How long does spermatogenesis take?
60-64 days
How many sperm on average are made per day?
30 million
Hormonal control of spermatogenesis?
Hypothalamus releases GnRH -> GnRH causes release of FSH and LH from pituitary gland -> LH acts on leydig cells to produce testosterone -> testosterone and FSH act on Sertoli cells to facilitate spermatogenesis and release inhibin -> testosterone acts on hypothalamus and pituitary as a negative feedback mechanism whereas inhibin only acts on the pituitary
Hormonal control of female reproductive system?
Hypothalamus secretes GnRH -> GnRH causes pituitary gland to secrete FSH and LH -> FSH and LH stimulate ovaries to produce oestrogen for follicular development and ovulation -> oestrogen controls release of GnRH and FSH/LH through a negative feedback mechanism
Menstrual cycle definition?
The monthly cycle of release of the oocyte and the preparation of the endometrial lining of the uterus for pregnancy which is then shed if fertilisation does not take place
What are the three phases of the menstrual cycle?
Follicular phase Ovulatory phase Luteal phase
What happens in the follicular phase of the menstrual cycle?
Where the follicle develops into a mature follicle Lasts 9-23 days
What happens in the ovulatory phase of the menstrual cycle?
Release of the oocyte Lasts 1-3 days
What happens in the luteal phase of the menstrual cycle?
Begins after ovulation with the development of the corpus luteum Lasts 13-14 days
Main cells of the follicle?
Granulosa cells Theca cells
What do theca cells do?
Respond to LH and synthesise testosterone
What do granulosa cells do?
Respond to FSH to synthesise oestradiol from testosterone They acts as nurse cells to the oocyte
How many follicles develop each month?
10-25
What causes all but one of the follicles to die?
A drop in FSH
What causes follicle growth?
FSH increase
What hormone causes ovulation?
LH increase
Why happens during ovulation?
The oocyte is released into the Fallopian tube
What is the corpus luteum?
The follicle after the oocyte has been released The granulosa cells greatly enlarge
What does the corpus luteum do?
Produces progesterone which stimulates the growth of the endometrial lining to prepare for pregnancy It also releases oestrogen and inhibin
Hormonal control of menstrual cycle?
Hypothalamus releases GnRH -> GnRH stimulates pituitary to releases FSH and LH -> FSH and LH stimulate follicles to produce low levels of oestradiol and also produce inhibin -> low levels of oestradiol inhibit GnRH to keep FSH and LH levels low causing menstruation -> LH and FSH levels increase which increase oestradiol which thickens the uterine lining -> GnRH is secreted causing LH and FSH levels to rise -> resulting in ovulation around a day later -> LH stimulates growth of corpus luteum -> corpus luteum releases oestradiol and progesterone that blocks GnRH and LH and FSH causing endometrium to further develop
What does the combined pill contain?
Oestrogen and a progestogen (synthetic progesterone)
How does the contraceptive pill work?
Suppresses the release of FSH and LH
What does human chorionic gonadotropin (HCG) do?
Generated by the developing embryo to ensure survival of corpus luteum
Where does fertilisation occur?
In the Fallopian tube
When can fertilisation occur?
Within a couple of days of ovulation
What is the zona pallucida?
the thick transparent membrane surrounding a mammalian ovum before implantation
How does fertilisation occur?
Sperm binds to zona pallucida -> triggers acrosomal reaction causing acrosomal enzymes to be released -> enzymes digest a path through zona pallucida -> when a sperm penetrates zona pallucida a reaction occurs to harden the zona pallucida to prevent entry of more sperm -> sperm DNA (the head) enters the oocyte which is now called a zygote
What is a zygote?
The cell formed by the union of two gametes
Fertilisation to implantation?
Zygote undergoes mitotic division resulting in 16-32 totipotent cell conceptus -> after 3/4 days conceptus reaches uterus -> totipotency is lost and conceptus differentiates and develops into blastocyst -> blastocyst embeds in wall of uterus
What are trophoblasts?
A layer of tissue surrounding the blastocyst Provides nutrients to the developing embryo for the first three months
What do trophoblasts release and why?
Human chorionic gonadotropin (HCG) to ensure survival of corpus luteum so it can continue to produce progesterone and oestradiol for the first three months to maintain the pregnancy
What do pregnancy tests detect?
HCG
How soon can a pregnancy test work?
After implantation (6-12 days after fertilisation)
What happens to trophoblasts at 3 months?
They differentiate into the placenta and stop making HCG and instead produce progesterone and oestradiol Placenta takes over the job of corpus luteum which degenerates due to fall in HCG
Name a common cause of miscarriage around 3 months?
When the switch between the corpus luteum and the placenta goes wrong
Where is oxytocin produced?
Hypothalamus and then stored in posterior pituitary
Process of oxytocin release?
Baby pushes against cervix causing activation of stretch receptors -> stretch receptor send message to hypothalamus to release more oxytocin This is positive feedback
What does oxytocin do?
Causes contractions of smooth muscle of the uterus pushing baby further down birth canal
Why may oxytocin be given to a patient?
To induce labour To accelerate labour To stop bleeding after deliver (routine after caesarean-delivery)
What is the difference between plasma, serum and whole blood?
Plasma is the liquid portion of blood before it has clotted Serum is liquid portion of blood after it has clotted Whole blood includes blood cells and other components
What is the auricle?
External ear
Parts of the outer ear?
Auricle External auditory canal
Auricle anatomy?
Elastic cartilage, adipose tissue covered in skin
What does the auricle do?
Help direct sounds to auditory canal
Parts of the middle ear?
Tympanic membrane Auditory ossicle (malleus, incus, stapes) Eustachian tube
What is the tympanic membrane?
Eardrum Thin, circular membrane covering interior auditory canal Vibrates in response to sound waves
What is the auditory ossicle?
Three small bones called malleus, incus and stapes Vibrate with the eardrum to conduct sounds to the inner ear
What is the Eustachian tube?
Small tube attaching middle ear to throat Equalises air pressure inside the middle ear with atmospheric pressure
Parts of the inner ear?
Cochlea, vestibule, semi-circular canals
What is the cochlea?
Spiral structure in inner ear Many hair fibres to detect vibrations Attached to nerve fibres from vestibulocochlear to transmit auditory signals to brain Filled with endolymph fluid
What is the vestibule?
Small, hollow region in inner ear Contains otolithic membranes that detect static equilibrium
What are the semi-circular canals?
Three canals filled with fluid in inner ear Detect dynamic equilibrium Each canal lined aligned to different area of the body Filled with endolymph fluid
Process of hearing?
1) auricle conducts sound waves towards external auditory canal 2) eardrum vibrates on to malleus 3) malleus vibrates on to incus 4) incus vibrates on to stapes 5) stapes pushes on small hole in cochlea creating ripple in endolymph 6) ripples detected by hair cells inside cochlea 7) hair cells connected to neurons which transmit information to brain
Process of static equilibrium? (Ear)
Sense of gravity direction Detected by otolithic membranes in vestibule of inner ear, the membranes have small calcium carbonate molecules embedded in gel matrix that are pulled down by gravity and bend the hair cells The bending of hair cells indicates direction and the nerve sends this to the brain
Process of dynamic equilibrium? (Ear)
Sense of rotational motion Detected by semi-circular canals Base of canal has a structure called a cupula which has hair cells to detect its movement (when pushed on by fluid) Bending of hairs indicates directions of movement and nerves transmit this to the brain
What is conductive hearing loss?
movement of sound through the external ear or middle ear is blocked, and the full sound does not reach the inner ear Can be problems with Eustachian tubes, middle ear itself or the auditory ossicle
What is otosclerosis?
Most common cause of hearing loss in young people Affects stapes bone causing gradual hearing loss Treat with hearing aids or surgery
What is sensorineural hearing loss?
Affects cochlea Mainly over 60s Age-related (called presbyacusis) Hearing aids may be needed
What is Eustachian tube dysfunction?
Usually temporary during or after a cold Middle ear can fill with fluid, known as middle ear effusion
What is glue ear?
Middle ear fills with glue-like liquid rather than air Usually self-limiting
Neurological hearing problems?
TBI Stroke Multiple sclerosis
Congenital hearing loss conditions?
Inherited Problems in womb including infections Low oxygen Birth complications Underdeveloped ear known as microtia
Sections of the nasal cavity?
Vestibule Respiratory Olfactory
What are turbinate bones?
Four bumps in the respiratory section of the nasal cavity covered by nasal mucosa Under these are passages to the meatuses which connect to the paranasal sinuses
Where are bowmans glands found in the nasal cavity?
Olfactory zone
What are the functions of the paranasal sinuses?
Adjust speech Produce mucus for nasal passage
Function of the nasolacrimal ducts?
Drain tears from lacrimal (tear) ducts to the nasal mucosa
Features of the nasal cavity lining?
Initial region lines by several layers of stratified squamous epithelial cells Outermost layer of cells covers the layer of proliferative cells attached to a basement membrane Posterior is lined with pseudostratified columnar ciliated epithelium which contain goblet cells
What is underneath the basement membrane of the nasal cavity?
Glands that secrete mucus, nerves, blood vessels
Function of bowmans glands?
Secrete mucus lining the nerves of the olfactory system Also secrete a pigment that gives the mucus a yellow colour Mucus dissolves odours and enables the interaction with olfactory receptors
What is the anterior chamber of the eye?
Space in the front of the eye between cornea and iris Full of aqueous humour (fluid)
What is aqueous humour?
Clear, water liquid produced by ciliary body and flows through pupil into anterior chamber 99.9% water 0.1% nutrients Helps maintain pressure and provides nutrients Drains through trabecular mesh work to keep pressure normal
What is the choroid of the eye?
Layer of tissue with blood vessels Located between sclera and retina Keeps retina and back of eye nourished
What is the ciliary body of the eye?
Between iris and choroid Helps lens change position for focusing (contracts to see close, relaxes to see far) Produces aqueous humour
What is the conjunctiva of the eye?
Clear, thin membrane lining the insides of the eyelids and white part of the eye Contains tiny blood vessels to supply eye and lid with oxygen and nutrients Keeps eye moist and prevents infection
What is the cornea of the eye?
Curved, clear layer at the front of the eye Light enters and rays are refracted before they pass further through the eye
What is the iris of the eye?
Coloured part of eye behind cornea Controls amount of light entering by adjusting pupil size
What is the lens of the eye?
Transparent, flexible disc Behind iris and pupil Helps focus light and image on retina
What is the drainage angle of the eye?
Junction of the iris and cornea
What is the macula of the eye?
Small, highly sensitive area in centre of retina Detects fine detail and colours
What is the fovea of the eye?
In centre of macula (retina) Contains only cones for the sharpest vision
What is the optic disc?
Circular area on retina where optic nerve enters the eye (blind spot)
What is the optic nerve of the eye?
Bundle of nerve fibres that carry electrical signals from the retina to the brain for processing
What is the posterior chamber of the eye?
Behind lens and in front of retina Filled with vitreous humour
What is the pupil of the eye?
Round, dark opening in centre of iris Opens and closes to adjust amount of light
What is the retina of the eye?
Light sensitive layer of photoreceptors cells Contains rods and cones Rods for low level light Cones for good light conditions and colour Retina sends picture to the brain
What is the sclera of the eye?
White structure tissue of the eye Thick connective tissue Supporting wall that protects inner eye components Controls the eyes movement
Purpose of tears?
Moist/lubricate the eye Provide oxygen and nutrients to eye surface Protect from damage Prevent eye infections
What is the uvea?
Iris, choroid and ciliary body together
What is vitreous humour of the eye?
Clear gel-like liquid filling the posterior chamber 99% water 1% sugar, salts, collagen and proteins Does not move/is not drained
Process of vision?
1) light ray reflects of object and enters eye through cornea 2) cornea refracts light onto lens 3) light ray passes through pupil 4) light refracted again whilst passing through lens 5) light focuses on retina 6) impulse travels down optic nerve to brain 7) brain corrects image
What is near-sightedness?
Myopia Distant objects looked blurred due to image being in front of the retina not on it Can adjust with diverging lenses to spread out light rays before they enter
What is far-sightedness?
Hyperopia Near objects look blurry due to image forming behind retina Correct with converging lenses to converge light rays together before they enter
Causes of blurred vision?
Refractive errors, corneal abrasion, age-related macular degeneration, scarring, infectious retinitis, migraine, retinopathy etc
What is age-related macular degeneration?
Most common cause of irreversible central vision loss in older people Affects central part of retina Dilated funduscopic findings are diagnostic Treat with dietary supplements, intravitreal injections of anti vascular endothelial growth factor drugs
What is glaucoma?
Causes vision loss through optic nerve damage due to increased intraocular pressure Leading cause of blindness in over 60s
What is a cataract?
Clouding over eye lens, protein build up Usually over 65s Usually in both eyes but one may be worse than the other Surgery
What is diabetic retinopathy?
Chronic, progressive condition associated with prolonged high blood sugar and high blood pressure Can be a symptomatic for long periods Can lead to blindness Vision loss can be associated with lesions and macular oedema or development of new blood vessels that bleed into the eye Laser treatment to stop vessel growth Eye injections to treat maculopathy
