Topic 15 - Breathing and Respiratory System

Question 1

Learning Objectives

Answer 1

1. Understand what the partial pressure of a gas is.
2. Trace the flow of air into the body beginning at the nose and ending at the alveoli
3. Describe why expansion of the thoracic cavity also expands the lungs
4. Explain why breathing in (inspiration) is an active process compared to breathing out (expiration)
5. List the mechanisms of how gases are transported in the body

Question 2

Order of inspiration

Answer 2

Nasal Cavity
Pharynx
Larynx
Trachea
Bronchii
Bronchioles
Alveoli

Question 3

Nasal Cavity

Answer 3

• Moistens air by adding water vapour
• Picks up pathogens (First line of defence)

Question 4

Pharynx

Answer 4

Common area mixes with food and liquids

Question 5

Larynx

Answer 5

• Top tupe portion of trachea
• Contains flap of tissue to block off trachea/ esophagus for swollowing/ breathing

Question 6

Trachea

Answer 6

• Contains strong cartilage rings to keep trachea open
• Lower respiratory system
• Splits into left and right bronchii

Question 7

Bronchii

Answer 7

• Left and Right
• Delivers air to left and right lung
• Splits into bronchioles
• Less cartilage closer to bronchioles

Question 8

Bronchioles

Answer 8

• 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)

Question 9

Alveoli

Answer 9

• Sacks on the end of bronchioles that perform gas exchange
• Works closely with capillaries
• Minimal diffusion distances

Question 10

Diaphragm

Answer 10

• Skeletal muscle controlling breathing
• Relaxes to squash lungs

Question 11

Right Lung

Answer 11

Contains 3 lobes
- Superior
- Middle
- Inferior

Question 12

Left Lung

Answer 12

Contains 2 lobes
- Superior
- Inferior

Contains a Cardiac notch where the heart sits

Question 13

Gas Exchange - Respiration

Answer 13

Moving O2 from the atmosphere into the body, then discharging Co2 into the atmosphere

Question 14

Gas Exchange - Partial Pressure

Answer 14

• 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

Question 15

Calculating partial psi

Answer 15

P(atm) = 760mmHg

P(O2) = 21%
P(CO2) = 0.03%

PO2 = 760x0.21 = 160mmHg
PCO2 = 760x0.0003 = 0.23mmHg

Question 16

Negative Pressure Breathing/ Inspiration

Breathing In

Answer 16

• 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

Question 17

Visceral Pleura

Answer 17

• Organ/ Lung side of the double membrane

Question 18

Parietal Pleura

Answer 18

• 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

Question 19

Breathing Out/ Expiration

Answer 19

• 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

Question 20

Gas exchange at the Alveoli

Answer 20

• 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

Question 21

Gas transport in the blood

Answer 21

• 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+

Question 22

O2 Transport via Haemoglobin

Answer 22

Each molecules carries 4 molecules of O2
4/4 bound = 100% saturation

Question 23

Haemoglobin saturation curves

Answer 23

At normal PO2 levels, Haemoglobin is 98% saturated,
- Minor changes in PO2 levels do not impact saturation

Question 24

Haemoglobin saturation curves - When things go wrong

Answer 24

2 General categories of Disfunction:
- Obstructive lung disease (blocked)
- Restrictive lung disease (expansions of chest wall)

Question 25

Pneumothorax

Answer 25

• 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

Question 26

Involuntary responses
- Sneeze
- Caugh
- Hiccup

Answer 26

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