gas exchange in humans

Question 1

features of gas exchange surfaces in humans

Answer 1

• thin (once cell thick)
• large surface area
• moist
• well ventilated
• close to blood supply

Question 2

thin gas exchange surface reason

Answer 2

Short distance to diffuse

Question 3

large surface area gas exchange surface reason

Answer 3

Many molecules can diffuse at once

Question 4

moist gas exchange surface reason

Answer 4

Cells die if not kept moist

Question 5

well ventilated gas exchange surface reason

Answer 5

Concentration gradients for oxygen and carbon dioxide are kept up by regular fresh supplies of air

Question 6

close to blood supply gas exchange surface reason

Answer 6

Gases can be carried to/from the cells that need/produce them

Question 7

cartilage function

Answer 7

Cartilage (in trachea): prevents the trachea from collapsing during absence of air and also to protect it

Question 8

ribs function

Answer 8

Ribs: to protect vital organs and blood vessels and expands and contracts (and efficient breathing)

Question 9

intercostal muscles function

Answer 9

Intercostal (internal & external) muscles: situated between the ribs that create and move the chest wall
-used when sneezing

Question 10

diaphragm function

Answer 10

Diaphragm: produces volume and pressure changes in the thorax leading to the ventilation of the lungs

Question 11

composition of inspired air

Answer 11

• 21% oxygen
• 0.04% CO2
• 78% nitrogen
• water vapour according to climate

Question 12

composition of expired air

Answer 12

• 18% oxygen
• 3% co2
• 78% nitrogen
• saturated water vapour

Question 13

test for CO2

Answer 13

Blow CO2 through limewater. +ve result = turn cloudy

Question 14

effect of physical activity on breathing

Answer 14

Physical activity increases the breathing rate – more breaths per minute, and the tidal volume – more air per breath

This is measured with a spirometer to produce a spirogram.

During exercise, tissues respire at a higher rate, the change in breathing volume and rate helps to keep CO2 concentration and pH at safe levels.

Question 15

what happens in the lungs during breathing in

Answer 15

• External intercostal muscles contract – pulls rib cage upwards and outwards
• Diaphragm muscles contract – diaphragm moves upwards
• Lung volume increases – and pressure falls
• Air rushes in to equalise pressure

Question 16

what happens in the lungs during breathing out

Answer 16

• External intercostal muscles relax – rib cage falls downwards and inwards
• Diaphragm muscles relax – returns to dome shape
• Lung volume decreases – and pressure increases
• Air is forced out

Question 17

function of muscle and cilia

Answer 17

goblet cells produce sticky mucus to trap and eliminate particulate matter and microorganisms.

Question 18

function of ciliated cells

Answer 18

Ciliated cells have cilia: little hairs which sweep back and forward in a coordinated way to brush mucus up the lungs into the mouth