7.2 Mammalian Gas Exchange System Flashcards
Is the surface area : volume ratio of mammals large or small
Small
Is the metabolic rate of mammals high or low? Why?
High, because they are active, and maintain their body temperature independent of the environment
State the passage of air when inhaled by a human
Nasal cavity -> Trachea -> Bronchus -> Bronchioles -> Alveoli
State the features of the nasal cavity.
-Has a large surface area with a good blood supply
-Has a hairy lining, which secretes mucus to trap dust and bacteria to protect lung tissue
-Has moist surfaces which increase the humidity of incoming air to reduce evaporation
What is the air entering the lungs like after it passes through the nasal cavity?
Similar temperature and humidity to the air already there
Describe the structure of the trachea
-Wide tube, supported by C-shaped rings of strong, flexible cartilage, which stops the trachea from collapsing
-Lined with a ciliated epithelium, with goblet cells between and below the epithelial cells
Why are the rings of cartilage in the trachea C-shaped?
So that food can move down the oesophagus behind the trachea
What do goblet cells and ciliated epithelium cells do in the trachea?
-Goblet cells secrete mucus onto the lining of the trachea, to trap dust and microorganisms that have escaped the nose lining
-The cilia move the mucus, along with any trapped dirt and microorganisms away from the lungs
-Most of this goes into the throat, and is swallowed and digested
What does the hairy lining of the nasal cavity do?
Secretes mucus to trap dust and bacteria, protecting delicate lung tissue from irritation and infection
Describe the structure of the bronchi
-Similar in structure to the trachea
-Contains smaller rings of cartilage in the walls to provide support. Strong, but flexible and stop the bronchi from collapsing when pressure drops
Describe the structure of the bronchioles
-Small tubes with no cartilage rings
-The walls of the bronchioles contain smooth muscle
-When the smooth muscle contracts, the bronchioles construct, when the smooth muscles relax, the bronchioles dilate
-Lined with a thin layer of flattened epithelium cells, making gaseous exchange possible
What does the smooth muscle in the walls of the bronchioles do?
Controls the amount of air reaching the lungs.
Why are bronchioles lined with a thin layer of flattened epithelium cells?
To make sure that gaseous exchange is possible.
Describe the structure of the alveoli.
-Alveoli are tiny air sacs which are the main gas exchange surfaces of the body. Millions in each lung.
-Each alveolus contains a layer of thin, flattened epithelial cells, along with some collagen and elastin fibres.
What is the function of the elastic tissues in the alveoli?
They allow the alveoli to stretch as air is drawn in. When they return to their resting size, they help squeeze the air out.
What is the ELASTIC RECOIL of the lungs?
The elastic tissue of the alveoli stretching and returning to their resting size
What are the main key adaptations of the alveoli?
-Large surface area
-Thin layers
-Good blood supply
-Good ventilation
Describe the feature of alveoli having a large surface area.
Allows for oxygen to diffuse into the body, and for carbon dioxide to diffuse out of the body at a rapid rate
Describe the feature of alveoli having thin layers.
Alveoli walls are only a single epithelial cell thick. So, diffusion distances between the air in the alveolus and the blood in the capillaries are very short.
Describe the feature of alveoli having a good blood supply.
The constant flow of blood through these capillaries surrounding the alveoli brings carbon dioxide and carries off oxygen, maintaining a steep concentration gradient.
Describe the feature of alveoli having good ventilation.
Breathing moves air in and out of the alveoli, helping maintain steep diffusion gradients
What is the inner surface of the alveoli covered in?
A thin layer of a solution of water, salts, and lung surfactant
What is the purpose of lung surfactant?
Makes it possible for the alveoli to remain inflated.
What is the purpose of having water in the alveoli?
Allows the oxygen to dissolve in the water before diffusing into the blood
What is ventilation?
The movement of air.
How is air moved in and out of the lungs?
As a result of pressure changes in the chest cavity (thorax)
What is the thorax?
The chest cavity.
What is the function of the ribcage?
To provide a semi-rigid case within which pressure can be lowered, with respect to the air around it.
What is the diaphragm?
A broad, domed sheet of muscle, which forms the floor of the thorax
Where are the external and internal intercostal muscles found?
Between the ribs
What is the thorax lined by?
Plural membranes, which surround the lungs.
What is the plural cavity usually filled with, and why?
A thin layer of lubricating fluid, so that the membranes slide over eachother easily as you breathe.
What happen to the cilia in the trachea of someone who has recently inhaled cigarette smoke?
They stop beating.
What is INSPIRATION?
Taking in air/inhalation
Describe what happens to the diaphragm, the intercostal muscles, and the thorax during inspiration.
-Diaphragm contracts
-External intercostal muscles contract, internal intercostal muscles relax, moving the ribs upwards and outwards
-Volume of the thorax increases, so the pressure in the thorax is reduced.
How is air drawn in during respiration?
The pressure in the chest cavity is lower than the pressure of the atmospheric air, so air is drawn in.
What is EXPIRATION?
Breathing out/exhalation
Describe what happens to the diaphragm, the intercostal muscles, alveoli, and the thorax during expiration.
-Diaphragm relaxes, so it moves up
-External intercostal muscles relax, internal intercostal muscles contract, the ribs move down and inwards
-Volume of the thorax decreases
-Elastic fibres in the alveoli return to their normal length
