Topic 15 - Breathing and Respiratory System Flashcards
Learning Objectives
- Understand what the partial pressure of a gas is.
- Trace the flow of air into the body beginning at the nose and ending at the alveoli
- Describe why expansion of the thoracic cavity also expands the lungs
- Explain why breathing in (inspiration) is an active process compared to breathing out (expiration)
- List the mechanisms of how gases are transported in the body
Order of inspiration
Nasal Cavity
Pharynx
Larynx
Trachea
Bronchii
Bronchioles
Alveoli
Nasal Cavity
- Moistens air by adding water vapour
- Picks up pathogens (First line of defence)
Pharynx
Common area mixes with food and liquids
Larynx
- Top tupe portion of trachea
- Contains flap of tissue to block off trachea/ esophagus for swollowing/ breathing
Trachea
- Contains strong cartilage rings to keep trachea open
- Lower respiratory system
- Splits into left and right bronchii
Bronchii
- Left and Right
- Delivers air to left and right lung
- Splits into bronchioles
- Less cartilage closer to bronchioles
Bronchioles
- Terminates in alveoli sacks where gas exchange occurs
- Has NO cartilage
- Contains bands of smooth muscle allowing to contract and dilate to alter airflow (Hormones and NS control)
Alveoli
- Sacks on the end of bronchioles that perform gas exchange
- Works closely with capillaries
- Minimal diffusion distances
Diaphragm
- Skeletal muscle controlling breathing
- Relaxes to squash lungs
Right Lung
Contains 3 lobes
- Superior
- Middle
- Inferior
Left Lung
Contains 2 lobes
- Superior
- Inferior
Contains a Cardiac notch where the heart sits
Gas Exchange - Respiration
Moving O2 from the atmosphere into the body, then discharging Co2 into the atmosphere
Gas Exchange - Partial Pressure
- Gas within a container (atmosphere/ body) exerts a pressure
- Amount of gas within a misxture can be measured by pressure
- To determine movement of gas, partial psi must be known
- Always moves from high to low psi
Calculating partial psi
P(atm) = 760mmHg
P(O2) = 21%
P(CO2) = 0.03%
PO2 = 760x0.21 = 160mmHg
PCO2 = 760x0.0003 = 0.23mmHg
Negative Pressure Breathing/ Inspiration
Breathing In
- To move O2 from atmosphere into body, Psi must be lower in the lungs
- Achieved by expanding thoracic cavity and chest wall by contraction od diaphragm and intercostal muscles (back and shoulders for deep breath)
Lungs are surrounded by double membrane
- visceral Pleura
- Parietal Pleura
Visceral Pleura
- Organ/ Lung side of the double membrane
Parietal Pleura
- Sticks lungs to rigcage and diaphragm through surface tension
- Outer membrane of lungs
- Fluid full of water molecules between parietal and visceral pleura creates tension with strong hydrogen bonds
Breathing Out/ Expiration
- Does not usually involve muscle contraction
- Passive process
- Rib rage and diaphragm relax, compressing down on the lungs, reducing volume and increasing psi in the thoracic cavity
- Air forced out of lungs due to high pressure gradient
Gas exchange at the Alveoli
- Alveoli create high SA:V for gas exchange
- Allows O2 to rapidly diffuse into surrounding capillaries
- Type 2 pneumocytes (alvoli cells) contain surfactant to minimise interaction and sticking together with water bonds
- Type 1 pneumocytes perform gas exhange
Gas transport in the blood
- O2 predominantly transported around body whilst bound to haemoglobin on RBC ~2% dissolved in plasma
- CO2 transported in RBC (23% transported on Haemoglobin and 70% converted to bicarbonate) ~7% dissolved in Plasma,
CO2 + H2O <=> HCO3- + H+
O2 Transport via Haemoglobin
Each molecules carries 4 molecules of O2
4/4 bound = 100% saturation
Haemoglobin saturation curves
At normal PO2 levels, Haemoglobin is 98% saturated,
- Minor changes in PO2 levels do not impact saturation
Haemoglobin saturation curves - When things go wrong
2 General categories of Disfunction:
- Obstructive lung disease (blocked)
- Restrictive lung disease (expansions of chest wall)
Pneumothorax
- Lung collapse
- When the connection between rib cage/ diaphragm and lung not good
- Lungs would shrink down and compress in on itself filling with blood and other substances
Involuntary responses
- Sneeze
- Caugh
- Hiccup
Sneezing
- Receptors in nose signal to brain to close of mouth
- Force air out lungs through nose to expell irritanta
Caughing
- Close off glutis and vocal chordsby signals from brain
- Blood psi in lungs forced out by muscle contractions
Hiccup
- Triggers lead to involuntary contraction of diaphragm
- Closes vocal chords causing air to bounce off creating the sound
