Mammalian Gaseous Exchange System Flashcards
What do mammals have in terms of cells and their organs?
Small SA:V ratio and a very large volume of cells.
What type of metabolic rate do mammals have and why is this?
High metabolic rate as they are active and maintain their body temperature independent of the environment.
What does this result in for the them?
They need lots of oxygen for cellular respiration and they produce CO2 which needs to be removed.
Where does the exchange of gases take place?
In Lungs
What are the lungs?
Pair of inflatable sacs lying in the chest cavity
How does air pass into the lungs and where does it then pass?
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.
What are lungs protected by?
Ribcage
What are the ribs held together by?
Intercostal muscles
What helps to produce breathing movements (ventilation)?
Action of intercostal muscles and the diaphragm.
What are the main key structures?
-Nasal Cavity
-Trachea
-Bronchus
-Bronchioles
-Aleveoli
What is the first important feature of the nasal cavity?
Large surface area with a good blood supply, warming the air to body temperature.
What is the second important feature of the nasal cavity?
A hairy lining, secretes mucus to trap dust and bacteria protecting delicate lung tissues from irritation and infection.
What is the third important feature of the nasal cavity?
Moist surfaces which increase the humidity of the incoming air, reducing evaporation from exchange surfaces.
What is the air like after passing through the nasal cavity and is entering the lungs?
Similar temperature and humidity to air already there.
What is the function of the trachea?
Main airway carrying clean, warm and moist air from nose down into the chest.
What is the trachea like structurally?
Wide tube supported by incomplete rings of strong flexible cartilage.
What does this cartilage do?
-Stops the trachea from collapsing.
-Incomplete allows food to move easily down the oesophagus behind the trachea.
What is the trachea lined with?
Ciliated epithelium with goblet cells between and below the epithelial cells.
What doe goblet cells do?
Secrete mucus onto the lining of the trachea to trap dust and microorganisms that have escaped the nose lining.
What do the cilia in the trachea do?
Beat and move mucus plus trapped dirt etc away from the lungs.
-most goes to throat and is swallowed and digested
Where and what is the bronchus?
In the chest cavity, trachea divides to form left bronchus leading to left lung and vice versa with the right side.
What is the structure of the bronchus like?
Similar to trachea with supporting rings of cartilage but are smaller.
What are bronchioles?
Bronchi divide to form many small bronchioles.
What do smaller bronchioles not have?
Cartilage rings
What do the walls of bronchioles contain?
Smooth muscle
What happens when this smooth muscles contracts and releaxes?
Contracts-bronchioles constrict
Relaxes-bronchioles dilate
What does this change in for the lungs?
Changes the amount of air reaching the lungs.
What are bronchioles lined with?
A thin layer of flattened epithelium, making some gaseous exchange possible.
What are alveoli?
Tiny air sacs which are the main gas exchange surfaces of the body.
What are alveoli unique to?
Mammalian lungs
What do each alveoli consist of?
A layer of thin, flattened epithelial. cells with some collagen and elastic fibres
What do the elastic tissues allow the alveoli to do?
To stretch as air is drawn in.
What happens when they return to their resting size?
They help squeeze the air out which is known as elastic recall.
What is the first adaptation of the alveoli for effective gaseous exchange?
Large surface areas of 300 to 500 million alveoli per adult lung
What is the second adaptation of the alveoli for effective gaseous exchange?
Thin layers with short diffusion distances between air in alveolus and blood in capillaries.
What is the third adaptation of the alveoli for effective gaseous exchange?
Good blood supply which brings CO2 and carries of O2 maintaining a steep concentration gradient for both (O2 and CO2) between air and blood.
What is the fourth adaptation of the alveoli for effective gaseous exchange?
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.
What is the inner surface of the alveoli covered in?
A thin layer of solution of water, salts and lung surfactant.
What does the lung surfactant allow?
Makes it possible for alveoli to remain inflated.
What happens to oxygen before diffusion to where?
Dissolves in water before diffusing into the blood but water can also evaporate into the air in the alveoli.
In humans, what is done to reduce this loss of water?
Several adaptations of the human gas exchange system.
