Chapter 7 (Mammalian Gas Exchange)

Question 1

Definition of a tissue?

Answer 1

Group of similar cells working together which are specialised to carry out a specific function
Eg, xylem tissue, phloem tissue, ciliated epithelium

Question 2

Definition of an organ

Answer 2

A group of different tissues working together which are specialised to carry out specific functions.
Eg, lungs, leaves

Question 3

Definition of an organ system?

Answer 3

Collection of organs working together with a specific function
Eg, circulatory system- heart, blood vessels, blood
Gas exchange system.

Question 4

What makes up the gas exchange system?

Answer 4

Lungs, trachea, bronchi, bronchioles, larynx, mouth, diaphragm.

Question 5

Function of GES?

Answer 5

1. Diffusion of respiratory gases, CO2 + O2 into blood stream
   - Rate of diffusion determines by many factors: SA:V incr., diffusion rate incr.

Question 6

Why would diffusion rate be too slow in multicellular organisms?

NOT FINISHED!!!!

Answer 6

Large diffusion distance between cells and outside environment

Question 7

Definition of tidal volume?

Answer 7

Volume of air that moves in and out of the lungs during a normal breath ~0.5dm3

Question 8

Definition of Vital capacity?

Answer 8

Maximum volume of air that can be inhaled or exhaled.

Question 9

Definition of residual volume?

Answer 9

Volume of air that remains in the lungs after a forced exhalation (important as it prevents the lungs collapsing and alveoli sticking together)

Question 10

Definition of breathing rate?

Answer 10

Number of breaths taken in a given time period (usually one minute)

Question 11

Definition of pulmonary ventilation?

Answer 11

Movement of fresh air into lungs and removal of stale air out of lungs over a minute.
PV( dm3min-1) = Tidal volume x breathing rate

Consists of inspiration and expiration
To maintain diffusion gradient.

Question 12

Definition of FEV1

Answer 12

Forced expiratory volume in one second - Volume of air forcibly exhaled in first second of forced exhalation

Question 13

Definition of PEFR

Answer 13

Peak expiratory flow rate

Maximum rate of forced exhalation through mouth

Question 14

Normal values of PEFR?

Answer 14

PEFR measurements used to diagnose pulmonary disorders,
eg, asthma, COPD
For asthmatic person - a lot lower than healthy person.
PEFR increases with age - maximum value at age 30-35.
PEFR measurements then fall from age of 35 as person ages to 85.

Question 15

Definition of respiratory arrest?

Answer 15

Occurs when person stops breathing
Causes:
Obstruction in airway blocking trachea or bronchi
Drug overdose - depresses nervous system and breathing system so they stop
Asthma attack
Severe pneumonia
severe shock
heart attack

Question 16

EAR information?

Answer 16

Expired air resuscitation

1. Call for help (wear gloves and mask)
2. Roll person onto back. remove obstruction visible in mouth, use sweeping motion of finger.
3. If unresponsive, open air ways - Hold head back by pressing on forehead and lifting chin. Move tongue from back of throat.
4. Check for breathing - chest movement and sounds.
5. Pinch nostrils closed and make seal around mouth with your mouth.
6. Blow gently into mouth and watch chest rise. Repeat when chest falls. If no, try again + recheck airways.
7. After 2 breaths check pulse. If pulse, continue
8. If no pulse, carry out CPR.

Question 17

How to carry out CPR?

Answer 17

Cardiopulmonary resuscitation.
Kneel down beside casualty on floor level with chest.
Place heel of one hand in centre of chest.
Place heel of other hand on top of first hand and interlock fingers.
With arms straight, press down by 5-6cm, then release pressure
Repeat 30 times, twice a second.
Then two rescue breaths.
If start breathing, put in recovery position.

Question 18

Smooth muscle info?

Answer 18

Found in walls of trachea, bronchi and bronchioles.
Enables diameter to be controlled
During exercise, smooth muscle relaxes -> lumen widens.
This reduces resistance to airflow -> easier to inhale and exhale.

Question 19

What does lung capacity depend on?

Answer 19

Body size
Level of activity
General health

~ 6 litres.

Question 20

How is EAR different for children?

Answer 20

Less forceful and softer breaths

Don’t tilt head back as far

Question 21

How are exchange surfaces adapted to have specialised features?

Answer 21

Increase in SA
Thin
Good blood supply
Steep diffusion gradient

Question 22

How is a large SA good for exchange surfaces?

Answer 22

SA of alveoli is huge
Alveoli can expand during inhalation
Further increases SA
Ie, more molecules of O2 and CO2 can diffuse per unit time

Question 23

Bronchioles information?

Answer 23

Subdivisions of the bronchi
Walls of larger bronchioles contain smooth muscle, elastic fibres, goblet cells and ciliated epithelium.

Walls of smaller bronchioles contain elastic fibres, epithelium, no cartilage, no cilia, no goblet cells.

Question 24

How does being thin help exchange surfaces?

Answer 24

Each alveolus made from single layer of flat, thin cells - alveolar epithelium
reduces diffusion distance,to incr. diffusion rate.
Capillary walls made from one cell, so total diffusion distance between RBC in plasma to air in alveoli is very small.

Question 25

How does having a good blood supply help exchange surfaces?

Answer 25

Large capillary network surrounds each alveolus Maintains conc gradient and enables O2 and CO2 to be exchanged in opposite directions.

Question 26

Alveoli information?

Answer 26

Ending sacs at end of each bronchiole. Site of gas exchange. Walls consist of single layer of squamous epithelial cells and elastic fibres containing elastin (for stretch during inhalation and recoil during exhalation) Walls also contain collagen and stretch receptors - sensory input to enable control of ventilation mechanism. Liquid layer lining alveoli contains surfactant (specialised phospholipid produced by septal cells in alveolar wall)

Question 27

How does having a steep diffusion gradient help exchange surfaces?

Answer 27

Pulmonary circulation rapidly delivers oxygenated blood and removes deoxygenated blood Pulmonary ventilation replaces CO2 rich air with O2 rich air to maintain diffusion gradient.

Question 28

What happens during inhalation?

Answer 28

External intercostal muscles contract (internal relax) Diaphragm contracts and flattens Volume of thorax increases as ribcage moves up and out Pressure of thorax decreases Atmospheric air forced into lungs Active process

Question 29

What happens during exhalation?

Answer 29

External intercostal muscles relax (internal contract) Diaphragm relaxes Volume of thorax decreases as ribcage moves downwards and inwards. Pressure of thorax increases Atmospheric air forced out of lungs Passive process

Question 30

What is the diaphragm?

Answer 30

Sheet of muscle at base of ribcage, separating thorax from abdomen

Question 31

Function of goblet cells?

Answer 31

``` Secrete mucus (mucus is a specialised glycoprotein) Mucus traps microorganisms (pathogens) and dust and pollen. ```

Question 32

What is the diaphragm?

Answer 32

Sheet of muscle at base of rib cage, separating thorax from abdomen

Question 33

What is the thorax?

Answer 33

An air-tight dome-shaped chamber formed by the ribcage and its intercostal muscles, with a domed floor - the diaphragm. Internal surfaces of thorax lined by pleural membrane - secretes pleural fluid. Proves surface tension that holds lungs to ribcage and protects lungs from friction during breathing movements.

Question 34

Elastic fibres information?

Answer 34

Found in walls of trachea, bronchi and bronchioles. During inhalation elastic fibres stretch to enable alveoli to inflate During exhalation, elastic fibres recoil to help deflate alveoli

Question 35

Bronchi information?

Answer 35

Carries air into/out of lungs. Lined with ciliated epithelium with many goblet cells Contains complete cartilage. Walls contain smooth muscle that contracts and narrows lumen of airway. Allow recoil back to normal size when muscle relaxes. At each division of bronchial tree - amount of cartilage decreases + smooth muscle increases - prevent collapse of tubes.

Question 36

What is the thorax?

Answer 36

An air-tight dome-shaped chamber formed by the ribcage and its intercostal muscles, with a domed floor (the diaphragm) Internal surfaces of thorax are lined by pleural membrane - secretes pleural fluid that provides surface tension that holds lungs to rib cage and protects lungs from friction during breathing movements.

Question 37

Trachea information?

Answer 37

Carries air from oral cavity to bronchi Held open by incomplete C shaped rings of cartilage around walls. -> prevent collapse under pressure from large bolus passing down oesophagus Under cartilage layer, smooth muscle, elastic fibres, glandular tissue, connective tissue and blood vessels. Lined with layer of ciliated epithelial cells and goblet cells that produce mucus that moisten incoming air and traps finer dust particles.

Question 38

Rings of cartilage information?

Answer 38

Found in walls of trachea and bronchi Provide support Strong but flexible to prevent trachea and bronchi collapsing during inhalation and pressure drops.

Question 39

Function of cilia information?

Answer 39

Hair-like extensions to individual cells. Beat adn waft mucus in rhythmic motion Moves mucus upwards towards throat and away from lungs Move mucus and trapped pathogens - up to mouth to be swallowed - HCL kills pathogens in stomach - Or coughed up and removed from body as sputum.

Question 40

Function of surfactant?

Answer 40

Reduces surface tension of water - Easier to inflate lungs - Prevents alveoli sticking together during exhalation - Contains antibacterial chemicals - Enables O2 to dissolve into surfactant - diffuse across alveolar wall. DOES NOT INCREASE RATE OF DIFFUSION.

Question 41

How does gas exchange occur in the alveoli?

Answer 41

As blood flows past alveoli, gas exchange occurs by diffusion. Oxygen dissolved in surface film of water, diffuses across blood plasma and into RBC. It combines with haemoglobin - oxyhaemoglobin. At the same time, CO2 diffuses from blood into alveolus.