7.2 The Mammalian Gaseous Exchange System Flashcards
What are the key features of the human gaseous exchange system
Nasal cavity Trachea Bronchus Bronchioles Alveoli
What are the key features of the naval cavity
Large surface area with good blood supply
Hairy lining - secretes mucus to trap dust and bacteria which protects delicate lung tissue
Moist surfaces - increase the humidity of incoming air, which reduces evaporation
What is the trachea and what does it do
The main airway carrying clean warm moist air from nose to chest
Its a wide tube supported by cartilage
What is cartilage and how does it help the trachea
They are incomplete rings that are strong and flexible and stop the trachea from collapsing
They are Nicolette so that food can move easily down the oesophagus behind trachea
What lines the trachea and it’s branches
Ciliated epithelium with goblet cells between and below the epithelial cells
The goblets cells secret mucus onto the lining of the trachea to trap dust that have escaped the nose lining
Cilia best and move the mucus and dirt away from the lungs into the throat
What does the trachea divide into in the chest cavity
Left and right bronchus that lead to the left and right kings
They have the same supporting rings of cartilage but smaller
What do the bronchi divide to in the lungs
Many small bronchioles
They have no cartilage
The walls contain smooth muscle and when the smooth muscle contracts the bronchioles constrict when they relax the bronchioles dilate
They are lined with a thin flattened layer of epithelium
What is the alveoli and it’s features
Tiny air sacs that are the main gas exchange surfaces
Diameter of 200-300um
Has a layer of thin flattened epithelial cells with collagen and elastic fibres
Elastic fibres allow the alveoli to stretch as air is drawn in
What is the elastic recoil if the lungs
Their elastic tissues allow them to stretch when air is drawn in and when they return to resting size they help squeeze the air out
Main adaptations of alveoli for effective gaseous exchange
Large surface area
Thin layers - single epithelial cells thick
Good blood supply -280 million capillaries
Good ventilation
Inner surface has lung surfactant which keeps the alveoli inflates
What parts of the body are involved in the ventilation of the lungs in the thorax
Rib cage provides semi-rigid case
Diaphragm is a broad domed sheet of muscle which forms floor of thorax
External and internal intercostal muscles found between the ribs
What is the thorax lined with
Pleural membranes which surround the lungs and the spaces between them is filled with a thin layer of lubricating fluid so membranes slide easily over each other
What takes place during inspiration
Diaphragm contracts and flattens and lowers
External intercostal muscles contract loving the ribs upward and out
Volume of thorax increases so pressure is reduced and it’s now lower pressure than the outside atmospheric air so air is drawn in
What takes place during expiration
Muscles of diaphragm relax so loves up into some shape
External intercostal muscles relax so ribs move down and inward
Elastic fibres in Alveoli return to normal length
This decreases the volume of thorax and pressure in now greater inside body than atmospheric air so air moves out
How do you exhale forcibly using energy
Internal intercostal muscles contract pulling ribs down hard and fast and the abdominal muscles contract forcing the diaphragm up to increase to increase pressure in lungs rapidly
