6.4 Gas Exchange

Question 1

What is ventilation?

Answer 1

Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries

Question 2

What is gas exchange?

Answer 2

all organisms absorb one gas from the environment and release a different one

Question 3

How do terrestrial organisms perform cell respiration?

Answer 3

They exchange gas with the air

Question 4

How do humans exchange gas?

Answer 4

occurs in small sacs called alveoli inside the lungs

Question 5

Why does diffusion occur between air in alveoli and blood flowing in capillaries?

Answer 5

Concentration gradient: Alveolus as more OXYGEN and lower concentration of CARBON DIOXIDE than blood capillary. So fresh air must be pumped into alveoli (provide for blood) and stale air must be remove

Question 6

When O2 diffuses from Alveoli to capillaries, and CO2 diffuses to alveoli, what is this process called?

Answer 6

Ventilation

Question 7

What are type I pneumocytes?

Answer 7

Type I pneumocytes are extremely thin alveolar cells that are adapted to carry out gas exchange in the epithelium

Question 8

what are the wall of each alveolus made of?

Answer 8

a single layer of cells, called epithelium made mostly of pneumocytes type I

Question 9

What is an adaptation to increase rate of gas exchange in humans?

Answer 9

As the blood’s wall’s are also made of a very thin cell layer, which makes the distance between alveoli and blood ( distance of diffusion) VERY SMALL with 0.5 micrometers Alveoli also has a large surface area

Question 10

What is the function of Type II penumocytes?

Answer 10

They secret solutions containing surfactant that creates a moist surface INSIDE the alveoli to prevent the sides of the alveolus ADHERING to each other by reducing SURFACE TENSION (prevents the lung from collapsing)

Question 11

What are Type II pneumocytes?

Answer 11

Rounded cells in the alveolar epithelium that can secret fluids to coat the inner of alveoli which contain PULMONARY SURFACTANTS

Question 12

Why do Type II pneumocytes coat the inner of alveoli?

Answer 12

1. the moisture allows oxygen in the alveolus to dissolve and then diffuse to the blood in the alveolar capillaries 2. provides area for carbon dioxide to be evaporated and be exhaled

Question 13

Why does the pulmonary surfactant prevent the alveoli from collapsing?

Answer 13

Structure similar to phospholipids, with the HYDROPHILIC head facing the water, and the HYDROPHOBIC tails facing the air, which as a result REDUCES SURFACE TENSION as the water is prevented from making the side of alveoli adhere (when exhaling)

Question 14

Who often suffers from infant respiratory distress syndrome?

Answer 14

Premature babies with insufficient pulmonary surfactant that can be treated with giving oxygen, and doses of surfactant (from animal lungs)

Question 15

What is the airway for ventilation?

Answer 15

1. Enters through nose/mouth 2. carried to the lungs in the trachea and bronchi and then to the alveoli in bronchioles

Question 16

What is this? and where does air flow afterwards?

Answer 16

1. Trachea 2. divides to form two bronchi

Question 17

What is this?

Answer 17

Left Bronchus (One bronchus leads to each lung)

Question 18

What do both trachea and bronchi have?

Answer 18

Walls with cartilage to strengthen them

Question 19

How are bronchi divided?

Answer 19

Divided repeatedly to form tree like structure of narrow airways called bronchioles which end with groups of alveoli

Question 20

What do bronchioles have in their walls?

Answer 20

smooth muscle fibres

Question 21

What causes changes inside the thorax?

Answer 21

Muscle contractions cause the pressure changes inside the thorax that force air in and out of the lungs to ventilate them

Question 22

What happens inside lungs when gas particles spread and occupy more volume?

Answer 22

The pressure becomes lower

Question 23

What happens when gas is free to move?

Answer 23

Flow from HIGH pressure to LOW pressure

Question 24

What is a diaphragm?

Answer 24

set of muscles that separate your thorax from your abdomen

Question 25

What happens to the thorax when air is forced into lungs? (Inspiration)

Answer 25

Muscle contractions cause the pressure inside thorax to drop so lungs DRAW AIR in - Diaphragm flattens (moves down) - ribcage expands (moves upwards)

Question 26

What happens to the thorax when air is forced out of lungs?

Answer 26

Muscle contraction cause pressure inside thorax to rise, so air is FORCED OUT of the lungs (expiration) - ribs move downward and inward - diaphragm moved up and becomes domed

Question 27

What is the only way for muscles to work?

Answer 27

Different muscles are required for inspiration and expiration because muscles only work when they contract

Question 28

What two stages can muscles be?

Answer 28

Relaxing or contracting

Question 29

Explain the need for ventilation system?

Answer 29

• most cellular respiration is aerobic and thus requires oxygen and produces CO2 - ventilation system exchange gas between inhaled air and lungs/blood stream - ventilation maintains high concentration gradient of gases in alveoli/lungs (to diffuse to cells)

Question 30

What happens when muscles do work?

Answer 30

they CONTRACT by exerting a pulling force (tension) that causes a particular movement. They become SHORTER

Question 31

What happens when muscles relax?

Answer 31

muscles LENGTHEN while they are relaxing, PASSIVE. Most are pulled into elongated state by contraction of another muscle

Question 32

What happens if movement in opposite direction is needed?

Answer 32

• Muscle can ONLY cause movement in one direction - so at least two muscles are required - one muscle will contract, while other one relaxes - They work ANTAGONISTICALLY

Question 33

Does inspiration/expiration require antagonistic pairs of muscles?

Answer 33

It involves opposite movements, so different muscles are required working as antagonistic pairs

Question 34

What happens to the movement of the diaphragm during inhalation?

Answer 34

Diaphragm CONTRACTS, moved DOWN and pushes the abdomen wall OUT the abdomen wall RELAX so pressure can be applied

Question 35

What happens to the movement of the diaphragm during exhalation?

Answer 35

Diaphragm RELAXES, moved UP into domed shape the abdomen wall CONTRACT so organs and diaphragm are pushed up

Question 36

What happens to the movement of the ribcage during inspiration?

Answer 36

Ext. intercostal muscles CONTRACT, pulling ribcage up and out . Int. intercostal relax and are pulled back in elongated state

Question 37

What happens to the movement of the ribcage during expiration?

Answer 37

Ext. intercostal muscles RELAX. Int. intercostal muscles CONTRACT and pull ribs inward and down

Question 38

What has contributed to understanding lung cancer?

Answer 38

Epidemiological studies. This studies the incidence and causes of disease. Most are observational because it rarely possible to investigate causes on humans

Question 39

What are causes of lung cancer?

Answer 39

• smoking - passive smoking - air pollution - radon gas - asbestos/silica/solids (usually in mines)

Question 40

Consequences of lung cancer

Answer 40

• difficult breathing, persistent coughing (cough up blood), chest pain, loss of appetite, weight loss, fatigue,m tumours

Question 41

What is emphysema?

Answer 41

chronic disease where normal (small and thin-walled) alveoli are replaced by a smaller number of larger alveoli with thicker wall –> gas exchange decreases/more difficult ventialtion

Question 42

Symptoms of emphysema?

Answer 42

lower oxygen and higher carbon dioxide concentrations in the blood –> lacks of energy (Ex. Patient can’t climb stairs), shortness of breath, and hard to breath

Question 43

Causes of emphysema?

Answer 43

• Smoking leads to increase in number of phagocytes that produces protease. These protease digest lung tissue - Smoking reduces the enzyme inhibitor called A1AT that prevent the proteases - Some genetic factors affecting A1AT in the lungs.