Mammalian Gaseous Exchange System

Question 1

What do mammals have in terms of cells and their organs?

Answer 1

Small SA:V ratio and a very large volume of cells.

Question 2

What type of metabolic rate do mammals have and why is this?

Answer 2

High metabolic rate as they are active and maintain their body temperature independent of the environment.

Question 3

What does this result in for the them?

Answer 3

They need lots of oxygen for cellular respiration and they produce CO2 which needs to be removed.

Question 4

Where does the exchange of gases take place?

Answer 4

In Lungs

Question 5

What are the lungs?

Answer 5

Pair of inflatable sacs lying in the chest cavity

Question 6

How does air pass into the lungs and where does it then pass?

Answer 6

Via the nose and along the trachea, bronchi and bronchioles which then reaches tiny air-filled sacs called alveoli which is where exchange of gases takes place.

Question 7

What are lungs protected by?

Answer 7

Ribcage

Question 8

What are the ribs held together by?

Answer 8

Intercostal muscles

Question 9

What helps to produce breathing movements (ventilation)?

Answer 9

Action of intercostal muscles and the diaphragm.

Question 10

What are the main key structures?

Answer 10

-Nasal Cavity
-Trachea
-Bronchus
-Bronchioles
-Aleveoli

Question 11

What is the first important feature of the nasal cavity?

Answer 11

Large surface area with a good blood supply, warming the air to body temperature.

Question 12

What is the second important feature of the nasal cavity?

Answer 12

A hairy lining, secretes mucus to trap dust and bacteria protecting delicate lung tissues from irritation and infection.

Question 13

What is the third important feature of the nasal cavity?

Answer 13

Moist surfaces which increase the humidity of the incoming air, reducing evaporation from exchange surfaces.

Question 14

What is the air like after passing through the nasal cavity and is entering the lungs?

Answer 14

Similar temperature and humidity to air already there.

Question 15

What is the function of the trachea?

Answer 15

Main airway carrying clean, warm and moist air from nose down into the chest.

Question 16

What is the trachea like structurally?

Answer 16

Wide tube supported by incomplete rings of strong flexible cartilage.

Question 17

What does this cartilage do?

Answer 17

-Stops the trachea from collapsing.
-Incomplete allows food to move easily down the oesophagus behind the trachea.

Question 18

What is the trachea lined with?

Answer 18

Ciliated epithelium with goblet cells between and below the epithelial cells.

Question 19

What doe goblet cells do?

Answer 19

Secrete mucus onto the lining of the trachea to trap dust and microorganisms that have escaped the nose lining.

Question 20

What do the cilia in the trachea do?

Answer 20

Beat and move mucus plus trapped dirt etc away from the lungs.
-most goes to throat and is swallowed and digested

Question 21

Where and what is the bronchus?

Answer 21

In the chest cavity, trachea divides to form left bronchus leading to left lung and vice versa with the right side.

Question 22

What is the structure of the bronchus like?

Answer 22

Similar to trachea with supporting rings of cartilage but are smaller.

Question 23

What are bronchioles?

Answer 23

Bronchi divide to form many small bronchioles.

Question 24

What do smaller bronchioles not have?

Answer 24

Cartilage rings

Question 25

What do the walls of bronchioles contain?

Answer 25

Smooth muscle

Question 26

What happens when this smooth muscles contracts and releaxes?

Answer 26

Contracts-bronchioles constrict Relaxes-bronchioles dilate

Question 27

What does this change in for the lungs?

Answer 27

Changes the amount of air reaching the lungs.

Question 28

What are bronchioles lined with?

Answer 28

A thin layer of flattened epithelium, making some gaseous exchange possible.

Question 29

What are alveoli?

Answer 29

Tiny air sacs which are the main gas exchange surfaces of the body.

Question 30

What are alveoli unique to?

Answer 30

Mammalian lungs

Question 31

What do each alveoli consist of?

Answer 31

A layer of thin, flattened epithelial. cells with some collagen and elastic fibres

Question 32

What do the elastic tissues allow the alveoli to do?

Answer 32

To stretch as air is drawn in.

Question 33

What happens when they return to their resting size?

Answer 33

They help squeeze the air out which is known as elastic recall.

Question 34

What is the first adaptation of the alveoli for effective gaseous exchange?

Answer 34

Large surface areas of 300 to 500 million alveoli per adult lung

Question 35

What is the second adaptation of the alveoli for effective gaseous exchange?

Answer 35

Thin layers with short diffusion distances between air in alveolus and blood in capillaries.

Question 36

What is the third adaptation of the alveoli for effective gaseous exchange?

Answer 36

Good blood supply which brings CO2 and carries of O2 maintaining a steep concentration gradient for both (O2 and CO2) between air and blood.

Question 37

What is the fourth adaptation of the alveoli for effective gaseous exchange?

Answer 37

Good ventilation; breathing moves air in and out of alveoli which helps to maintain steep diffusion gradients for O2 and CO2 between blood and air in lungs.

Question 38

What is the inner surface of the alveoli covered in?

Answer 38

A thin layer of solution of water, salts and lung surfactant.

Question 39

What does the lung surfactant allow?

Answer 39

Makes it possible for alveoli to remain inflated.

Question 40

What happens to oxygen before diffusion to where?

Answer 40

Dissolves in water before diffusing into the blood but water can also evaporate into the air in the alveoli.

Question 41

In humans, what is done to reduce this loss of water?

Answer 41

Several adaptations of the human gas exchange system.