Anatomy & Physiology Doc
Respiratory System
Part 1
Anatomy + Physiology open book exam
respiratory, cardiac, Gastrointestinal, liver, muscoskeletal, endocrine, central nervous system, peripheral nervous system
Overall function of the given system
Outline the major structures of the system (most important ones)
Heart
blood vessels
blood
electrical conduction
Structure - Function - Role in the whole system
Link it all together
Heart pumps blood (flow of blood, electrical conduction)
vessels transport
capillaries exchange
Blood carries oxygen // substances to where it needs to go
link back to the function of the system
Respiratory System
Structure
Mouth / Nose
Pharynx
Nasopharynx - behind nose
Oropharynx - behind mouth
Larynx is a structure of several organs in this order. It is called often the voice box because it CONTAINS the vocal chords inside it
Trachea
Left & Right Bronchi Go into the lung’s - (Secondary bronchi) go into the different lobes of the lungs - (Tertiary Bronchi) go into different segments of the lobes - Bronchioles - terminal bronchioles - respiratory bronchioles - ducts - sacs - Alveoli individual.
Process 1. How does breathing in & out happen?
Inhale
Diaphragm contracts and flattens from its dome shape
Ribs (intercostal muscles) contract and ribs move up and out expanding the chest (CHEST GETS BIGGER)
Air is pulled into the lungs: air flows in because pressure inside is lower because there is more space - than the pressure outside.
When space gets bigger (chest expanding) air spreads out so pressure decreases - while pressure outside is higher this causes air to want to be drawn into our chest (lower pressure) forcing us to inhale.
Pressure: air particles move from an area of high pressure to low pressure naturally (to spread out)
they are forced to move to where there is more space i.e when our lungs expand there is less pressure than outside = inhalation
Exhale
Diaphragm relaxes returning to its dome shape
Intercostal muscles relax and move down and inwards - chest cavity is getting smaller again.
Air is forced out of the lungs: this is because pressure inside is higher when lung volume (space) gets smaller - so Particles are forced to where it is lower; which is the atmosphere causing exhalation.
so in summary
Inhalation - Chest cavity expands; diaphragm contracts; intercostal muscles cause ribs to move up and outwards. Pressure inside the lungs decrease. Pressure outside is higher. Inhalation happens as particles are forced to move to an area where pressure is lower such as inside the lungs.
Exhalation: chest cavity gets smaller; diaphragm relaxes; intercostal muscles cause ribs to move down and inwards. Pressure inside the lungs is now higher due to volume decrease. Atmosphere pressure is lower than inside the lungs; particles inside the lungs move to where it is lower causing exhalation.
Breathing is a mechanical process. Meaning; something happens because of movement, physical changes or forces.
Rib’s move up and out // down and in
diaphragm moves up // down
chest space for lung expansion gets bigger or smaller.
this is all movement. This movement causes change. It causes pressure changes (high to low and low to high) causing us to naturally inhale and exhale.
Process 2, of Gaseous exchange inside the alveoli sacs.
High concentration: lots of particles
low concentration: little amount of particles
Diffusion: process of gas particles moving from an area of high concentration to low concentration, particles spread out to even things out.
When we breathe in; lots of oxygen inhaled: high concentration of oxygen gas enter the alveoli sacs
capillaries encase these same alveoli sacs. They carry deoxygenated blood and mainly carbon dioxide (low concentration of oxygen gas) -
so the oxygen from the alveoli (high) moves into the blood
carbon dioxide from the blood moves into the alveoli (low amount of co2)
the co2 in the alveoli is then exhaled and removed.
Description of each part of the respiratory system and role
Nose: filters particles via cilia hairs and mucus. Mucus traps and cili removes particles that are harmful. Nasal cavity also plays a role in moistening air. Main entry point for air
Mouth: another entry point for air
Pharynx (back of throat): shared passage for air and food. Passes air to the larynx
Epiglottis: flap/trapdoor that covers the airway (larynx) when we are swallowing preventing food being aspirated into airways
Larynx; contains the vocal chords on the sides. Contains the glottis space that directs air into the trachea. Larynx is the whole structure including the epiglottis; vocal chords; glottis space. It is the AIRWAY / larynx is the open airway that flow of air passes through to get to the trachea and to where it needs to go
Trachea: main next part of the airway after larynx - that leads to the lungs. Held open by c shaped cartilage rings. C shaped cartilage rings also prevents the collapse of the airway by stabilising it. Trachea carries air into the lungs. Lined in cilia. Produces mucus from mucus glands and works with cilia to remove harmful particles. (Glands produces mucus and traps particles, cilia pushes and moves mucus out of the airways to keep clear and to keep good flow of air to and from the lungs)
Bronchi Left & Right: two main branches that descend from the trachea and go to each lung. Carries air from the trachea into the lungs. Supported by cartilage to be held open and allow air in
Alveoli sacs: tiny balloon like sacs attached at the end of the bronchioles. Where gaseous exchange happens. We have millions of tiny alveoli sacs. Millions of alveoli sacs create lots of surface area when they add up together
More surface = more oxygen is able to enter the blood all at one time as well as more co2 can leave blood all at once. Creating faster gas exchange. Alveoli and capillary walls are one cell thick so this also leads to quick diffusing of oxygen and carbon dioxide. So huge SA = efficiency, thin walls = quick crossing of gas = fast and efficient gaseous exchange
Capillaries:
One cell thick because they need to diffuse gases across their walls quickly.
Exchange of gases happen here because it can happen quickly due to thin walls.
(Alveoli is also one cell thick) so when capillaries encase the alveoli’s rapid exchange can happen because there is a very small barrier
Capillary carries deoxygenated blood into vessel - alveoli brings oxygen into vessel and into the bloodstream. Carbon dioxide goes into the alveoli (this is because of pressure again high to low, capillary carries lots of carbon dioxide while alveoli carries very little so it moves into the alveoli for more space. The same thing with oxygen) - blood is now oxygenated and goes back to the heart to be delivered to everywhere in the body where it is required.
Surrounding alveoli’s, one cell thick makes for a short small barrier = efficient / rapid exchange. When we have millions of this happening at the same time this is even more efficient diffusion of gas
Layers of membranes of the lungs: Pleura is plural (both layers together are called the pleura)
1) Visceral Pleura; covers lungs directly
2) Parietal Pleura; lines chest wall
In between is fluid filled space called the pleural cavity
Role is to reduce friction / rubbing when we breathe in and out (when there is movement with the chest wall and the lungs)
the fluid filled space separates the two layers from contacting. The lungs are able to expand and contract smoothly during breathing without touching the other membrane / the chest wall.
Primary BRONCHI to respiratory BRONCHIOLES - ALVEOLAR DUCTS to ALVEOLI’S
Main bronchi, right and left - goes into the lungs. Descends from the trachea. Allows flow of air to go from trachea into the lung
made of cartilage that ensures they stay open to allow air into the lungs
lined with mucus and cilia. Mucus traps while cilia moves out of the airways. So role is to filter and deliver
Secondary Bronchi’s - these distend into the separates lobes of the lungs from the main bronchi
tertiary bronchi - supplies segments of the lobes. Bronchi are made of cartilage. Bronchioles are made of smooth muscle. Bronchi stay open and don’t get narrower or wider, Bronchioles can constrict or dilate and can control the amount of air flow coming in and out.
Bronchioles - made of smooth muscle and no cartilage. They can constrict and dilate, giving more airflow or less. Smaller airways that branch off from the tertiary bronchi. Goes deeper into the lungs.
Terminal bronchioles
More branching off from first bronchioles.
respiratory bronchioles. Walls lined with alveoli. START OF GA HAPPENS IN THESE AIRWAYS NOT DUCTS.
Even smaller airways. gaseous exchange starts here
Alveolar ducts - tiny tubes branching from respiratory bronchioles. Walls are lined with alveoli.
alveolar sacs - clusters (like a bunch of grapes) of alveoli sacs grouped together. Bigger surface area when alveoli are clumped together in groups.
alveoli - individual air sac. One cell thick. Encased by capillary blood vessels. Where gaseous exchange happens via the capillaries and the alveoli walls rapidly exchanging gas.
inside alveoli walls
Covered with thin layer of fluid
fluid naturally causes (surface tension) inside walls of alveoli to pull the walls together // collapse of the alveoli walls
Surfactant substance sits on top of that fluid. Reduces the pull of the walls. Prevents collapse of alveoli. Ensures gaseous exchange can continously happen.
For part 1
Describe the normal structure and function of the organ (lungs)
outline the flow of air from inspiration to expiration // outline the process of gaseous exchange in the alveoli’s
Discuss at a cellular level
what is (example - bronchiolitis) and how does this impact the flow of air in the body (process of the system) // gaseous exchange?
Link to what is presented in our patient using evidence that tells us they have this common condition
what are the signs and symptoms of the common condition
Link to presentation, to physiology (understanding of the heart structure / function)
Outline Structure + Function 2) Outline sequence of given Process 3) Explain common condition - link to patient’s clinical presentation (use evidence)
support every question with evidence - explain - link back to question.
Part two
Follow structure of of PEEL
Point
Evidence
Explain
Link
Make a supportive argument using structure and a against statement
Patient: how is their stage of development (age) affected by being hospitalised // the care they need how does it impact on their development (physical, emotional, intellectual, social, spiritual, financial if these two are relevant in being impacted by being hospitalised)
what might impacts be on the family members
how is a nurse // wider MDT (explain their role and how they are able to support the patient ) and their family from these impacts? What can they do to make the impact smaller for the family for the patient - including after they leave, while in the hospital. How do they make sure psychosocial and clinical needs are being met
Identify the issue - what is the impact in all areas - how can they be supported? How can the impact be minimised.
Cardiovascular System
The cardiovascular system
primary functions
transport substances - plasma (nutrients; glucose, amino acids and vitamins), red blood cells (oxygen to cells for respiration)
defend the body from foreign bodies - white blood cells
Clot the blood to heal injuries and prevent foreign bodies getting in - platelets
Deliver oxygen to the lungs and alveolar capillaries for gaseous exchange - red blood cells
Pulmonary circulation - the transport of deoxygenated blood to the lungs and alveolar capillaries for gaseous exchange
to oxygenate blood for cellular respiration to enable cell’s to generate energy that power’s their cellular activities / that enables them to function and stay alive
works closely with the cardiac system
process: systole (contracting, pushing) and diastole (relaxing, filling)
right atrium is relaxed and filling (diastole) - deoxygenated blood enters the right atrium via the superior and inferior vena cava
As blood fills the right atrium, blood also passively empties into the right ventricle.
This is because - more deoxygenated blood that enters the right atrium pressure increases. Right ventricle has little to no pressure because it is empty so naturally blood passively empties into the right ventricle.
Why does this happen? There’s a pressure gradient - the right atrium has more pressure than the right ventricle (more and more volume, ventricle is empty)
tricuspid valve is open - open door, pathway
Flow of blood into the right ventricle happens automatically - particles naturally spread from an area of high pressure to Low pressure when there is a pathway that allows it
Sinoatrial node generates an impulse - spreads over the atria (left and right)
the right atrium contracts (systole) and pushes all of the deoxygenated blood into the right ventricle (ventricle was already filling because of passive flow of blood, this is the top up that pushes all the blood into the ventricle)
The atrial ventricular node delays the given impulse that contracts the ventricles
Delay is about 0.1 seconds - helps to ensure the atria fully contract and empty into ventricles before ventricular contraction starts
Once this is done, impulse travels to the bundle of his and then the perkiness fibres. These spread over the right ventricle
right ventricle then strongly contracts (systole)
deoxygenated blood gets pushed through the pulmonary artery to the lungs and alveolar capillaries for gaseous exchange
Deoxygenated blood exits the main pulmonary artery in the heart
Flows through pulmonary arteries
Lobar (secondary) arteries - to each lung lobe
Segmental (tertiary) arteries - to each segment of the lobes
Smaller arteries
Arterioles
Alveolar capillaries - gaseous exchange happens here; co2 releases and o2 enters the blood; blood is now oxygenated
Oxygenated blood now travels through the
Venules
Veins
Pulmonary veins
Back to the left atrium
Oxygenated blood returns to the heart via the pulmonary vein, and fills the left atrium which is in diastole.
Blood passively fills the left ventricle as mitral valve gets open due to increasing pressure of the left atrium
SA node generates impulse (this is not separate and happens at the same time of the right atria right ventricle)
Impulse travels over the left atrium, left atrium contracts and pushes all oxygenated blood into the left ventricle
impulse arrives at the av node - delays impulse for 0.1 second while atrium fully contracts and empties oxygenated blood into the left ventricle
once finished - impulse travels through the bundle of his - then the purkinje fibers - spreads all over the left ventricle
left ventricle contracts (systole) strongly
left ventricle pushes oxygenated blood through the aortic valve through aorta and blood is sent all over the body to transport the oxygen and other substances
Atrial systole (contract) - ventricles fills - tricuspid is open
0.1 second delay - av node
ventricular systole (contract) - atria in diastole (relaxed)
Valves respond to pressure differences -
atrial pressure more than ventricle pressure - valves open
Atria systole, ventricle diastole - tricuspid valve open
Ventricular pressure more than atria pressure - valve closed
Ventricle systole, atria diastole - tricuspid valve closed - preventing backflow of blood
this ensures blood follows a one way pathway
Systemic Circulation - the flow of blood from the heart - to all the cells in the body - back to the heart
primary functions
Transport substances and deliver them to the cells that need them
Including oxygen to cells for respiration - allow cells to retrieve the energy that powers their activities
blood clotting
defending the body from pathogens / foreign bodies
Removal of waste - co2 and urea
Left ventricle pumps oxygenated blood that is nutrient rich (amino acids, glucose, vitamins, oxygen) into the aorta
blood travels through the aorta ➡️ arteries ➡️ smaller arteries ➡️ arterioles
structure of arteries
Narrow lumen
elastic walls
To stretch and recoil to handle pressure
thick muscular walls
high pressure blood flow
oxygenated blood travels through them
exchange of substances in the capillaries
Oxygen leaves the blood ➡️ enters cells
glucose and nutrients leave ➡️ enters cells
carbon dioxide and wastes enter the blood
cell’s use the substances for respiration - generates ATP. - ATP powers their cell activity - organ is able to function
After exchange blood is now
Low oxygen
more co2
still has some nutrients left
Not all tissues take everything at once from the blood
cells only take what they need at that moment depending on
Energy demand
hormonal signals
concentration difference between blood and cells
blood returns to the heart via
Venules
veins
Wide lumen
low pressure blood flow
walls are not elastic
deoxygenated blood
has valves
thin walls (less muscle and elastic tissue)
blood enters the right atrium via the superior and inferior vena cava, starting pulmonary circulation all over again
Blood pressure is the force of blood pushing against the walls of blood vessels as the heart pumps
heart contracts (systole) ➡️ pushes blood out of the left ventricle into the aorta
this creates high pressure in the arteries
blood then moves through arteries ➡️ arterioles ➡️capillaries
heart relaxes (diastole) ➡️pressure drops as chambers refill
The features of the artery maintains arterial pressure (high)
Elastic recoil
Blood forced in, arteries stretch
heart relaxed, arteries recoil (normal shape)
recoil pushes blood forward again, blood keeps moving
Thick muscular wall
Smooth muscle helps withstand the high pressure without bursting
able to control diameter to adjust pressure and flow
Narrow lumen
Blood less spread out in a small space = higher pressure maintained
Each heartbeat sends a new surge of blood keeping pressure up and maintained
Blood is made of plasma
Mostly water (makes it liquid)
Nutrients - amino acids, glucose, vitamins
carries cell’s
White blood cells
red blood cells
platelets
Transport and delivery of substances to cells
amino acids
we consume protein from food such as egg
this gets digested and broken down into amino acids
These amino acids become proteins again but proteins specifically designed to repair and grow cells
Repair of cells
cells get damage / wear and tear constantly because they’re constantly active
Normal metabolism (waste products, reactive molecules)
physical stress (stretching, wear)
chemicals (toxins, uv)
The more wear and tear, cell’s lose their ability to function very gradually but constantly
so they need constant repair - proteins do this
when a cell has damage - proteins made from amino acids are used to detect the damage, fix it and restore normal function by
Detecting damage
repair dna
replace damaged parts
Rebuild proteins, membranes and structures
clean up damage
Break down faulty proteins or cell parts
control process
Pause cell activity or trigger cell death if damage is too extensive
growth of cell
Cell grows in size
Makes more organelles
builds up proteins and cytoplasm
membrane expands as cell grows inside
Cell copies its DNA
division
Cell organises copied information
separates / organises into two sets
cell splits into two identical cells
so transporting amino acids is vital because they repair through protein synthesis
Cells constantly get damaged from normal activity, chemicals, uv, physical stress
repair from proteins fix this
without
Proteins stop working
dna errors accumulate
cell becomes less efficient or stops functioning completely
cell may die or get replaced
repair keeps cell working properly and prevents long term failure // prevent accumulation of damage
cell growth and division is vital
Growth of organism / allows us to develop such as from an embryo to a child to an adult. We wouldn’t exist without cell division
repairing damaged tissues (replacing lost or damaged cells after injury)
Without: cell would eventually stop working as damage accumulates
replacing cells with short lifespans
Red blood cells - 120 days
gut lining cells - replaced frequently
skin cells
If not replenished; oxygen cant be transported efficiently, skin barrier would break down
Allows for cells to become specialised later on (muscle, nerve) - these functions wont be able to work without specialised cells
hormones - transported in the plasma alongside glucose and amino acids
hormones are chemical messengers that control and coordinate body functions
Blood glucose - blood sugar
Insulin: when blood sugar rises insulin tells the liver to ➡️turn excess glucose into glycogen and tells cells to uptake glucose to use it for respiration ➡️blood sugar lowers
When blood sugar is low; glucagon hormone tells the liver to break down stored glycogen into glucose
glucose gets released into the bloodstream
blood glucose rises
Fluid balance - Adh
When is there is less water in the bloodstream ADH tells the kidney’s to absorb more water ➡️less urine produced + becomes more concentrated, more water goes to the bloodstream
When we have too much water in the blood stream ➡️less Adh released ➡️kidney’s absorb less water ➡️more urine, more diluted
adrenaline - stress/danger
when we are faced with short term stress or a dangerous situation - adrenaline is released - breathing + heart rate gets faster = more oxygen in and transported to cells = more energy for cells to be ready to run or fight (fight or flight syndrome)
cortisol - prolonged stress
When we are facing long term stress cortisol -
raises blood glucose levels - more energy for cells
suppresses non essential functions like the immune response
with more glucose available in the body, body has fuel to cope with prolonged stress
TSH hormone - thyroid
Controls the metabolic rate (how fast cells respire and release energy)
More thyroxine ➡️faster metabolism ➡️more energy released in cells
less thyroxine ➡️slower metabolism ➡️less energy released
white blood cells
we need to transport white blood cells in the blood through systemic circulation because they are the body cells defense system from harm - by preventing continued harm / damage - they help to ensure a stable internal condition of the body allowing all cells to continue to function normally and efficiently
we have two types
lymphocytes
B lymphocytes
T lymphocytes
lymphocytes produce antibodies - these antibodies bind to antigens on pathogens - tagging them for destruction
Bacteria enters the body ➡️phagocyte detects it as foreign and engulfs some immediately
Antigens from pathogen activate lymphocyte - signals that they are foreign bodies
B lymphocyte produces specific antibodies - binds to antigens on bacteria
Makes bacteria easier for phagocytes to engulf
some B cells become memory cells
Virus infects a host cell ➡️infected cell displays vital antigens on its surface ➡️T helper cells recognise this and activate killer T cells
killer T cells destoy the infected cell
Stops the virus reproducing inside cells
Phagocytes clean up cell debris
Memory cells remain for faster response next time
it is important that we have white blood cells in the systemic circulation
Protection from pathogens like bacteria and viruses
prevents damage to cells and tissues and stops infection spreading
maintains a stable internal environment so cells and enzymes can function properly
Platelets
Clotting blood cells. They help or allow our blood to clot to heal injuries and to prevent blood loss. It also helps the body to prevent foreign bodies / pathogens entering the body and causing internal harm
structure - tiny cell fragments in the blood. They’re not full cells - dont have a nucleus
filled with clotting factors
surface of these cells have receptors that allow them to detect damaged blood vessels
function:
detect damage to blood vessels
stick to the damaged area
stick to each other
release chemicals to attract more platelets
Forms a clot to stop blood volume loss
primary role is - stopping bleeding from continuing - without doing this; we’d continously lose blood and face reduced circulation of blood and its components to tissues organs and cells in the body affecting cells and therefore effecting our organs and how they work
process
Blood vessel is damaged
platelets stick to the damaged area using receptors
once attatched platelets change shape ➡️spiky; helps them grab things
release chemicals
chemicals attract more platelets ➡️make them stick together
forming a platelet plug
clotting factors in the blood activate the protein mesh called fibrin
Wraps around the platelet plug
makes it strong and stable
Platelets contract ➡️tighten the clot
blood vessel repairs itself
eventually clot dissolves
Coronary Circulation
Is the blood supply to the heart itself. Allows the heart muscle cells to retrieve energy to power its activities (contracting the heart chambers / pumping of blood)
Oxygenated blood leaves the left ventricle (ventricular systole; bundle of his purkinje fibers) and gets pumped into the aorta. (Blood is oxygenated and nutrient rich)
right at the start of the aorta coronary arteries branch off
arteries carry the oxygenated blood which also is nutrient rich (glucose, amino acids and vitamins)
coronary arteries ➡️ smaller arteries ➡️ capillaries in the heart muscle
exchange happens in capillaries
Oxygen diffuses into heart muscle cells
glucose enters cells
co2 and waste diffuse into the blood
respiration = creates ATP (energy) which the cell uses to power its activities
the blood now is deoxygenated - low o2, more co2
blood collects into coronary veins
Capillaries
Small veins
Larger veins
Coronary sinus
coronary sinus empties into the right atrium with the rest of deoxygenated blood
whats the complete structure of the heart A to B
The heart starts from the inferior vena cava and superior vena cava
Collects deoxygenated blood from the lower and upper body and delivers to the heart Delivers deoxygenated blood into the right atrium
complete process - including electrical conduction // systole and diastole // flow
Diastole - means when the heart is at rest (relaxed, filling with blood) . The heart process starts with this
The superior and inferior vena cava are feeding the right atrium during diastole with deoxygenated blood that is returning from both the upper and lower parts of the body.
The right atrium has lower pressure than the vena cava’s - blood moves from high pressure to low pressure naturally - vena cava blood flows into the right atrium
why is it lower pressure? = thin walls, lower pressure than inside the vena cavae, diastole makes right atrium low pressure
The more blood that enters the right atrium = pressure increases
right ventricle has lower pressure than right atrium because its in diastole // relaxed
blood passively flows through because of pressure gradient and due to tricuspid valve being open
sinoatrial node starts the electrical conduction process of the heart. It starts the impulse at the right atrium and causes the right atrium (and left at the same time) to contract
the impulse arrives at the atrialventricular node. Node sits between the atria and ventricles. Allows the atria to finish contracting before ventricle contraction // allows atria to deliver all of its blood to the ventricle before the ventricle contracts - 0.1 second delay
During contraction - blood is under higher pressure + tricuspid valve is open = all blood flows into the right ventricle which is relaxed and at lower pressure. Pressure gradient always causes blood flow to keep moving
this contraction happens with the passive flow - ensures all deoxygenated blood is delivered to the right ventricle
delay of the atrialventricular node now ends. Impulse causes ventricles to contract. Both left and right. This is why the heart is a dual pump because the electrical impulse makes both atria’s together act together and ventricles after to both contract together
When the right ventricle contraction begins = high pressure
Ventricular pressure is higher than the atria’s causes the tricuspid valve to shut to prevent blood flowing backwards to where it is lower pressure. Pressure gradient will naturally causes blood to flow back into the atrium. Tricuspid closing prevents this
right ventricle transports deoxygenated blood through the open pulmonary valve to the main pulmonary artery trunk - right and left pulmonary arteries - lobar / secondary arteries - tertiary or segmental arteries - smaller arteries - arterioles - capillaries where gaseous exchange happens and blood becomes oxygenated - venules - pulmonary veins - oxygenated blood is brung back to the primary pulmonary vein into the left atrium which is in diastole // low pressure which causes blood to flow in
When the atria are in diastole / relaxed and filling - ventricles are also in diastole. Ventricular diastole means they are relaxed and expanding
expanding of the ventricles causes ventricle pressure to be lower than the atria - so blood flowing in from the pulmonary vein flows into the left ventricle due to lower pressure than the atria. The mitral valve being open allows this.
pressure difference causes the closing and opening of the hearts valves
if the atrial pressure is more than the ventricular pressure the valve between remains open
if ventricular pressure is more than atrial pressure the valve will close to prevent blood flowing backwards into the atria because of the lower pressure - which is why the mitral valve is open at this point
so passive flow is happening - the sinoatrial node starts the electrical impulse for systole
(note - impulse at sinoatrial node - causes systole of BOTH atria’s at the same time - then impulse goes to the atrialventricular node - delayed for 0.1 seconds - delay finishes and both ventricles contract transporting the blood)
the left atrium contracts - higher pressure - all oxygenated blood flows into the left ventricle as it is lower pressure than the atrium
ventricular diastole ends and systole starts as impulse delay ends
ventricle starts to contract because of impulse - higher pressure - mitral valve is shut to prevent backflow of blood
when ventricular pressure is higher than the atrium and the blood is trying to go back - it closes to stop it flowing backwards -
the left ventricular - thick and muscular - contracts strongly because its exerts a greater force on the blood
aortic valve opens
blood is pushed into the aorta -
Blood enters the coronary arteries to perfuse the heart first
then blood continues into systemic circulation of the entire body delivering all of its components; glucose, amino acids, vitamins, oxygen, WBC’s, platelets, red blood cells
Location & Position
thoracic cavity
between the lungs
Heart covering
pericardium - fibrous outer covering
pericardial fluid reduces friction during beating
Heart wall layers
epicardium - outer layer
myocardium - thick muscular layer - responsible for contraction
endocardium - smooth inner lining
septum separates left and right sides preventing mixing
left ventricle has the thickest myocardium as it pumps blood to the entire body - thicker muscle = stronger contraction
Thicker wall = more muscle fibers contracting at once = generates greater force
Digestive system
The Digestive System
What is digestion?
Is the breakdown of food into molecules and parts of which are able to pass through the intestinal wall and be absorbed by the bloodstream to be transported to cells to be towards their growth, repair and generating the energy they need to power their cellular activities.
Digestion uses up what we need from food and the rest is removed from the body as waste ensuring the cells and the body get exactly the amount they need and not too much or too little
Why do we need it?
because our cells need to use the nutrients to work and to keep working
glucose = needed for respiration to take place with oxygen, without = no respiration = no energy = cellular activities cant take place
amino acids specifically repair cells = without cells would stop working eventually and amino acids also play a part in growing cells so they wouldn’t get replaced therefore cells would die and therefore organs would eventually stop working because the cells wouldn’t get replaced
Fatty acids
vitamins
First what is the upper digestive tract?
Mouth
oropharynx
oesophagus
how does it work?
Mechanical breakdown
take a bite of food - ingestion
teeth
Tears, cut, grinds the food - mechanical process of breaking down food into smaller and smaller pieces
tongue
Moves the food around
Rolls food into bolus (soft ball of food)
coats food in saliva
Released from salivary glands
contains water - moistens food - making swallowing easier
amylase - starts breaking carbohydrates into simple sugars
Once the bolus is formed - tongue pushes it to the oropharynx, the back of the throat
the glottis space gets covered with the epiglottis trapdoor flap
this prevents food going into the wrong pipe - the windpipe of the trachea and causing aspiration of food into the lungs
so bolus of food goes down the oesophagus
breakdown of food now becomes automatic and no longer is mechanical or requires physical action
Oesophagus is a muscular tube
inner lining - lined with mucosa, produces mucus to help food slide along
the muscle layer of the oesophagus is responsible for producing the contractions that moves the food along
these contractions are called peristalsis
Upper oesophageal sphincter (muscular ring) opens to let bolus in
closes after bolus comes in to prevent food going back up
Just behind the bolus
Muscles tighten
this pushes the bolus forward
in front of bolus the muscles are relaxed and dilated allowing bolus to come forward
Pressure causes the bolus to move forward
Muscle tightening = high pressure
Muscle relaxing = low pressure
bolus moves from high pressure low pressure = moves forward
this process keeps going until the lower oesophageal sphincter which relaxes and dilates to allow the bolus to reach the stomach
it will close again after to prevent stomach acid coming back up and corroding the oesophagus
Stomach
bolus now is in the stomach
Stomach stores the food
mechanical digestion is back
stomach mixes and grinds, churns and squeezes the bolus of food
as it does so, it releases gastric juice into the bolus which contains the hydrochloric acid
Very acidic
kills any bacteria in the food
creates right ph for enzymes
contains protease
Breaks proteins into smaller peptides
the mixing grinding and adding the gastric juice = turns bolus into chyme, a paste like substance
Next: pyloric sphincter opens slightly
each time the stomach mixes, new tiny amount of chyme is pushed through the pyloric sphincter
small amounts of chyme enters the small intestine, continously in small amounts = controlled flow
not all enters because
Small intestine needs time to work
Neutralise acid
add enzymes
digest properly
stomach content is highly acidic = little gradually prevents damage to intestines
nutrients need time to absorb into the small intestine
the small intestine
Much longer than the large intestine
narrower than the large intestine
composed of 3 parts; duodenum 1st; jejunum; and the ilium
we are able to live without certain amounts of the small intestines
most nutrients get absorbed here (large intestine takes the waste to be expelled from the body)
Duodenum.
The 1st part of the small intestine
where the chyme arrives after coming through the pyloric sphincter
Chyme is very acidic from the stomach; gets neutralised here
bile is secreted from the gallbladder into the chyme
Breaks big fat down into tiny drops of fat to make it easier for enzymes to work (pancreatic enzyme lipase)
pancreatic enzymes get added by the pancreas
Breaks down
Carbs into sugars
proteins into amino acids
fats into fatty acids and glycerol
Structure
protection; glands that produce alkaline mucus - neutralises the acid from the chyme coming from the stomach
enzymes work better at slightly alkaline conditions
lining has villi - finger like projections; their function is to absorb
some are micro villi
increases surface area for absorption - jejunum does this a lot more
Role of the duodenum:
neutralise the stomach acid (alkaline mucus),
controls stomach emptying via hormones -
controls how fast chyme enters
when bile and pancreatic juice is released
After the duodenum, and the enzymes and the bile has done their job to break the food further we move to the jejunum part of the small intestine
the carbs are now glucose
proteins are now amino acids
fats are now fatty acids and glycerol
Jejunum
Villi
Microvilli
Role = take nutrients and pass them to the blood stream
without Villi or microvilli - there would be no actual way for the nutrients of the food to get into the bloodstream because the intestinal wall would be the barrier that prevents it getting to where it needs to go
no way to absorb = no transportation = cells dont get the nutrients they need
with them ✅the intestinal wall is covered in villi’s - finger like bumps
each individual villi has its own microvilli on its surface - like hair on its surface
makes for every efficient absorption of nutrients
each microvilli and villi’s
has blood vessels inside it
Glucose goes into the blood
amino acids goes into the blood
lymph vessels
fat goes into the lymph
concentration gradients causes the actual movement of the nutrients into the blood and lymph vessels
in the intestine there’s a high concentration of the nutrients - particles move from areas of high concentration to low concentration naturally - the blood has a low concentration of the nutrients - causing the actual diffusion of the nutrients into the blood because the blood has a lower concentration than the small intestine
lots of villi with even lots of microvilli creates a large surface area for absorption because every single villi has blood vessels and lymph vessels which will draw the nutrients in compared to no surface for absorption
Lots of villi and microvilli attatched to the surface of the villi also further increases surface area in that the food or nutrients actually are touching a lot more wall all at once
circular folds = triples the surface area of the intestines
more contact = more absorption happening at the same time
no villi and microvilli = no contact or very little so diffusion isnt easy or quick (not efficient)
this makes it extremely efficient during absorption because it can take a lot all at once compared to if we only had a few = only some at a time
after glucose ✅fats ✅amino acids ✅ are taken by the jejunum - we are left with: water, bile salts, vitamin b12, leftover nutrients
which go to the ileum
longest part of the small intestine
Nutrients spend the most time here
absorbed again via the villi and microvilli
bile salts are recycled back to the liver
role of the ileum is to mainly finish absorption and recycle bile salts and vitamin b12
at the end of the ileum - ileocecal valve
controls the movement from small intestine to the large intestine
like the cardiac valve - prevents the backflow of waste / leftover after nutrients are removed
LARGE INTESTINE (colon)
final process of digestion
initially what enters the colon is liquid - water and electrolytes - because we’ve removed the vitamins ✅ and the bile salts ✅
the large intestine is much wider and 1.5 m long - this is because it needs to fit our waste / stool comfortably
the process of digestion in the colon is to remove the water and electrolytes
and to be left with all the waste - which becomes stool - which will be then expelled by the rectum and the anus
gut bacteria breaks down leftover material and produces vitamin K
rectum
faeces stored temporarily
rectum stretches as it fills
stretch receptors in rectum detect fullness
sends signal to the brain that we need to go to the toilet
defecation
rectum contracts
internal anal sphincter relaxes automatically
external anal sphincter relaxes - voluntary
faeces are expelled through the anus
we can choose to hold the external sphincter but if pressure gets too much - reflex takes over
COMPLETE PROCESS OF THE COLON DIGESTION
Contents entering is mostly water undigested material salts and bacteria
body needs the water to maintain the blood volume because it makes up most of the blood plasma and keeps it liquid - without water wed have reduced or no blood volume which is life threatening because the blood would not be able to reach the whole body and its cells and deliver what it needs to
water moves from the gut to the blood using osmosis; once water is removed - what remains in the gut isnt liquid anymore but thick now starting to form the faeces
salt is absorbed to maintain electrolyte balance - how? - through diffusion
gut bacteria helps process leftovers
breaks down undigested food
produces vitamin k; b vitamins; wind
formation of faeces
why? We need to remove waste efficiently
how? Water removed - material becomes solild
mixed with bacteria, dead cells, fibre
ends at the rectum
faeces now solid or semi solid
stored temporarily before removal
ileocecal valve ➡️colon ➡️rectum
whole colon process takes around 24 hours to complete
peristalisis contractions - muscle commencing wave like contractions
small intestine: happens constantly; slow, gentle to allow time for absorption and digestion (mixing)
large intestine; slow peristalsis
When the contraction happens its a big contraction - strong wave
pushes faeces towards the rectum
So summary
key processes
mechanical digestion / breakdown
mouth; tearing, chewing food into small pieces (called mastication), tongue mixes
stomach; grinds using contractions; into small pieces - and churns food (swirls and stirs so mixes gastric juice (pancreas and hcl) into food)
chemical digestion
mouth: amylase from saliva breaks down starch into simple sugars - maltose
Stomach; acid denatures protein (stops it working), pepsin enzyme from pancreatic juice breaks proteins into smaller peptide chains (smaller proteins)
duodenum: PRIMARY chemical breakdown of food using bile and pancreatic enzymes
Maltase into glucose - amylase enzyme
peptides into amino acids - protease enzyme
fats into fatty acids and glycerol - lipase enzyme and bile
Bile is what breaks fat down. Using emulsifying which means; large fat droplets get broken into tiny droplets
lipase turns the small fat droplets into fatty acids and glycerol
bile gets recycled back to the liver once used to break down fat
absorption
jejunum mainly
glucose, amino acids, fatty acids and glycerol, absorbed into the blood via diffusion and the villi and microvilli
ileum; finishes absorption of remaining nutrients; vitamin b12 and bile salts
What’s left by the time we reach the colon; is mostly water, fibre we cant digest/ indigestible material, dead cells and bacteria
as contents move through the colon (via peristalsis) colon absorbs water (through osmosis) and salts back into the body
what is osmosis?
movement of water across a partially permeable membrane
from a dilute solution to a more concentrated solution
dilute = lots of water
concentrated = less water more solutes (salts, glucose)
Water moves to balance concentrations
whats in the colon at first?
leftover material contains; lots of water, some salts. Undigested fibre and bacteria = highly diluted / watery
colon lining actively absorbs salts into the blood
makes the blood side more concentrated (less water, more solutes)
osmosis = water moves from the gut / material that is highly diluted
into the blood which is concentrated from the salts to balance the concentration
= water reabsorbed into the blood
contents in colon becomes; thicker, solid, forms faeces
changes from liquid ➡️thick paste
Colon is full of gut bacteria
produces gases
break down some remaining material
ferments carbs
What’s left after is faeces which is composed of; water (very little), undigested fibre, dead bacteria (mostly)
peristalsis pushes it along to be stored in the rectum
receptions signal to us when the rectum is full and needs to be expelled / emptied
external sphincter - voluntary - we can choose to hold to a certain degree - too much pressure - reflex takes over
internal sphincter is automatic and stores rectum automatically