Topic 2 - Lungs + Genetic Diseas (2.1 + Flashcards
What is a gas exchange system
A respiratory system where gas such as oxygen is transported from one membrane to another
What makes up the human respiratory system
Gas enters into the body through the mouth and into the trachea.
The trachea brings the gas into the lungs, and it splits into two bronchi which enter each side of the lungs.
The bronchi the split into bronchioles which then deliver oxygen into the alveoli where gas exchange can occur
Why do mammals need a gas exchange system
Mammals require high levels of oxygen, and produce a large amount of co2
the gas exchange system allows mammals to efficiently remove co2 from the blood, and move oxygen into it (via diffusion)
Gas exchange systems are also needed to keep up with our high metabolic rate (reactions such as respiration and protein synthesis)
Where are the lungs located (in a human)
They are located in the thorax (in the chest) and are protected by a ribcage
What is the structure of the trachea
it has smooth muscle
It is protected by c- ring cartilage
(Small amount smooth muscle )
It has ciliated epithelium
it has a lumen (where the air flows)
What is the purpose of the c-ring cartilage in the trachea + bronchi
It provides support and flexibility
this prevents the trachea / bronchi from collapsing, and also permits it to contract
What is the purpose of the smooth muscle in the trachea / bronchi
Smooth muscle contracts and relaxes to change the diameter of the lumen.
This lets it adjust airflow - ensuring more efficient respiration
it can also contract to reduce the number of pathogens entering the lungs
What is ciliated epithelium
An ‘outside’ layer made of ciliated cells and goblet cells.
the goblet cells are located between ciliated cells
What is the purpose of ciliated cells + goblet cells
Goblet cells secrete mucus which traps dirt and pathogen
The cilia then wafts mucus up and out of the airways into the mouth, where it can be swallowed (dissolved by stomach acid) or spat out.
What are bronchioles mostly made of
Mostly smooth muscle (to change the lumens size) and ciliated epithelial
some have c-ring cartilage, but most are too small
Why does the lumen in the trachea / bronchi / bronchioles need to change size
The lumen can be increased in diameter to allow for more efficient airflow
It can be decreased in diameter to reduce airflow, and reduce the number of dirt / pathogens entering the lungs
What are the alveoli
Small air sacks connected to the end of bronchioles.
Gas exchange occurs here
what are squamous cells
Flattened cells that can fit close together
What is Frick’s Law
rate of diffusion ∝ (surface area x concentration difference) / diffusion distance
How has the human respiratory system adapted to have a larger surface area
It has a large number of folded alveoli
How has the human respiratory system adapted to have a larger surface area
It has a large number of folded alveoli
How has the human respiratory system adapted to have a higher concentration difference
Large number of pulmonary capillaries ensure oxygenated blood is always being moved to the alveoli
Breathing constantly ensures oxygen is entering the lungs, and carbon dioxide is leaving
How has the human respiratory system adapted to have a higher concentration difference
Large number of pulmonary capillaries ensure oxygenated blood is always being moved to the alveoli
Breathing constantly ensures oxygen is entering the lungs, and carbon dioxide is leaving
How has the human respiratory system adapted to have a low diffusion distance
Both alveoli and capillaries have a 1 cell thick external wall (alveoli has squamous epithelial cells and the capillaries have endothelial cells)
so the diffusion distance is only 2 cells
Alveoli wall cells are ‘squamous’ which means they are thinner than normal cells
how do we inhale
Following stimulation from the phrenic nerve, the diaphragm contracts and moves in the inferior direction
The external intercostal muscle contracts, moving the ribcage up and out
This increases the volume of the thoracic cavity, decreasing the pressure
Ths creates a pressure gradient between the atmosphere and the alveolus, generating a flow of air from the the higher pressure in the atmosphere into the gas exchange system throught the nose or mouth
How do we exhale
Followig stimulation from the phrenic nerve the diaphragm relaxes and moves in the superior direction
The internal intercostal muscle contracts moving the ribcage down and in
This decreases the volume of the thoracic cavity and therefore increases the pressure
This makes a pressure gradient between the atmosphere and the alveouls generating a flow of air from the higher pressure in the gas exchange system to the atmosphere through the nose and the mouth.
What does the external intercostal muscle do
It is responsible for the elevation of the ribs and bending them open
what does the internal intercostal muscle do
It is responsible for the depression of the ribs and bending them inwards
What pathway does air travel through to reach the lungs
Nose + Mouth
Pharynx
Larynx
Trachea
Bronchi
Bronchioles
Alveoli
What is a genotype
The genetic makeup of an organism
What is a phenotype
The physical expression of a characteristic
What is monohybrid inheritance
The inheritance of a single allele
What is a hetrozygous genotype
Having 1 dominant and 1 recessive allele
What is a homozygous genotype
Either two recessive alleles
Or two dominant alleles
Which alleles most commonly cause genetic diseases
Recessive alleles
What is needed for a dominant characteristic to be expressed
Only 1 dominant allele is needed
What is needed for a recessive characteristic to be expressed
Two recessive alleles
How is sickle cell disease inherited
It is an autosomal recessive allele - two recessice alleles are needed
What are autosomal chromosomes
Chromosomes 1 -22
What is a sex - linked disorder
A disorder caused by the x or y chromosomes
(Chromosome 23)
What is codominance / incomplete dominance
When neither alleles are recesseive (Both are dominant)
Heterozygotes (ppl with both alleles) will express both phenotypes
How do you draw a punnett square
- Phenotype
- Genotype
- specific alleles
ENCLOSED box with each allele
What is cystic fibrosis
An autosomal recessive disease that results in the production of thicker, sticky mucus
How is cystic fibrosis caused
A mutation in the CFTR gene causes the CFTR protein channel to be dysfunctional
(Causing defective chloride transport)
This causes the mucus to be stickier and thicker - as it contains less water (less cl- ions in the mucus means its water potential is higher)
This sticky mucus clogs up organs and airways
How is mucus changed to be less sticky
Cl- moves into epithelial cells from the tissue fluid
Cl- then diffuses into the mucus via CFTR channel proteins
Na+ diffuses from the tissue fluid to the mucus
CFTR prevents Na+ from being actively transported back into the tissue fluid
The Water potential of the mucus has been lowered
Water moves into the mucus (from the tissue fluid) via osmosis
What is an electrical gradient (e.g.between the inside and outside of a cell)
The difference of charge (of ions)
Ions will.move to achieve nutrality
How is the mucus changed if it is too runny
There are Na+ and Cl- ions in the mucus
Cl- ions can diffuse straight into the tissue fluid
Na+ ions enter the epithelial cell through active transport
The Na+ then diffuses into the tissue fluid through channel proteins
The water potential in the mucus is higher, so water moves via osmosis into the tissue fluid
Why is mucus too sticky in cystic fibrosis (regulation of mucus)
Cl- is pumped into the epithelial cells
Due to the faulty CFTR gene Cl- cant diffuse into the mucus (faulty protein channels) (reamins in epithelial cells)
There is no electrical gradient, so sodium will not diffuse out of the tissue fluid into the mucus
Due to the CFTR mutation, ENaCs remain open causing Na+ to leave the mucus and diffuse into epithelial cells
The movemnt of Na+ also causes Cl- to be pulled into the epithelial cells
This increases the water potential of the mucus - so water moves via osmosis into the tissue fluid (making the mucus stickier)
How does CF impact the respiratory system
-Mucus blocks airways so less oxygen is brought to the alveoli (concentration gradient decreases)
- Mucus reduces the SA of alveoli + increases diffusion distance
Why can someone with CF develop lung infections / emphysema
The mucus is too sticky to be wanted up and out by the cillia
Bacteria grows in the mucus which can cause infections
Why are people with CF prescribed bronchodilators
Bronchodilators relax muscles in your lungs, widening the airways
Oxygen enters the lungs more (increasing concentration gradient)
Information is decreased
Why are people with CF prescribed DNAase enzymes
It breaks down the DNA that causes faulty CFTR and ENaC protein channels
This allows the water potential of the mucus to be controlled better
Why are people with CF prescribed antibiotics
To kill bacteria growing in the mucus - reducing infections
What is the CFTR and what does it do
Cystic fibrosis Transmembrane regulator (protein)
Controls the salt / water content in cells by moving cl- in and out of cells
(Regulates osmotic pressure)
What is ENaC and what does it do
Epithelial sodium channels
They regulate the amount of sodium that enters and leaves cells
What is the endocrine function of the pancreas
Secreting hormones into the blood stream
What is the exocrine function of the pancreas
Secreting enzymes into ducts
How does CF affect the exocrine function of the pancreas
Mucus build up can block pancreatic ducts
This prevents the pancreas from secreting digestive enzymes
This doesnt effect the endocrine system as ducts are not used in that system
Why is someone with CF prescribed high energy foods (+ calorific foods)
With CF nutrients are absorbed less (as mucus coats the lining of the small intestine + there are less digestive enzymes)
High calorie foods are needed to ensure enough energy is absorbed
This happens as there are not enough digestive proteins
Why are people with CF prescribed enzyme supplements
Digestive enzymes can be taken as a supplement to replace those not produced
They will break down food
Where does CF affect the female reproductive system
Mucus builds up in the cervix
Where does CF affect the male reproductive system
Mucus builds up in the sperm duct
What are the effects of CF of the female reproductive system
Infertility
Inflammation of the cervix
Irregular mensural profiles
What are the effects of CF of the male reproductive system
Infertility
How can CF induced fertility be treated
By extracting the sperm and eggs (since they are blocked by the mucus)
A child would be conceived through IVF
What is amniocentesis
A test where amniotic fluid from the amniotic sac is removed and then tested for genetic conditions
What is CVS (the test)
Chronic Villi sampling is a process where cells are removed from the placenta and tested for genetic sampling
What is PiGD
Pre implantation genetic diagnosis
An embryo is created by IVF and (when its 8 cells) is tested for genetic diseases
What is NiPD
Non-invasive prenatal diagnosis
A diagnosis test where a maternal blood draw is taken, and the DNA is tested for genetic diseases
What are the risks of CVS and amniocentesis
CVS has a 1-2% risk of miscarriage
Amniocentesis has a 0.1 - 0.5% risk of miscarriage
What are the risks of NiPD and PiGD
There are none since they are non - invasive (do not require intensive surgery)
Why are genetic tests used
They give reliable information that allows parents to plan for the future
It can allow planning for medical care
The parents could decide to abort the child
When are amniocentesis and CVS done + their accuracy
Amniocentesis - 14-16 weeks (99% accuracy)
CVS - 9-14 weeks (98% accurate)
What is an allele
A different version of a gene on the same locus
(point of a chromosome)
The genes have different base sequences
What is a recessive allele
A type of allele that requires both allels to be expressed in the phenotype
They are a different version of a gene at the same locus
