1. Respiratory System
Topic
Content
Structure and Function of the
respiratory system
The exchange of gases between
the internal and external
environments of the body is
facilitated by the structure and
function of the respiratory
system at the
cell, tissue and
organ levels
Respiratory System Structure and Function
·
Nasal
cavity
– warms, filters and moistens air
·
Pharynx-
shared area of respiratory and digestive system
·
Epiglottis
- flap of cartilage tissue covering trachea when swallowing
·
Larynx
– cartilage and mucous membranes produce sound & speech
·
Trachea
– air way containing cartilage rings to keep the trachea
open when inhaling and cilia and mucus producing epithelial cells
that trap and waft material out of the trachea
·
Ribs
– made of bone connective tissue for protection of lungs
·
Intercostal muscles
– skeletal muscles contract to raise the ribs up
and out; lungs are “attached” to ribs via the pleural fluid/pleural
membranes and therefore also increase in volume resulting in
inhalation
·
Pleural membrane
–line the lungs and ribs and secretes pleural fluid
·
Pleural fluid
– lubricant, holds lungs to pleural membranes and in
turn the ribs
·
Diaphragm
- skeletal muscle that contracts downwards into
abdominal cavity increasing the volume of the thoracic cavity and
thus the lungs resulting in inhalation
·
Bronchioles
–fine tubes extending from the bronchi with walls with
smooth muscle that contract or relax to constrict or dilate the
airways therefore regulating airflow to the lungs
·
Bronchus
- 2 large airways branching from the trachea
·
Alveoli
- small grape like structures at terminal of bronchioles which
are the site of gas exchange
Breathing
·
Inspiration
o
Diaphragm contracts: flattens and pushes down into the
abdominal cavity
o
Intercostal muscles contract pulling the rib cage up and out
o
Lung volume increases and pressure inside the lungs decreases
o
Air flows from the area of high pressure outside the lungs into
the area of low pressure inside the lungs
·
Expiration
o
Diaphragm relaxes doming up into the thoracic cavity reducing
lung volume
o
At the same time the intercostal muscles relax lowering the rib
cage causing ribs to move down and in
o
Lung volume decreases and pressure inside the lungs increases
o
Air flows from the area of high pressure inside the lungs into
the area of low pressure outside the lungs
Blood Flow in Pulmonary Circulation
·
Pulmonary arteries
–deoxygenated blood from heart to lungs
·
Pulmonary veins-
oxygenated blood from the lungs to the heart
Exchange of gases
The efficient exchange of gases
in the lungs is maintained by
the actions of breathing, blood
flow and the structure of the
alveoli
Passive diffusion of gases
·
movement of gases from high concentration to low
concentration, with/down the concentration gradient
(diffusion), requires no expenditure of energy by the cell
·
Simple diffusion of gases occurs directly through the cell
membrane between alveoli and capillary as molecules are small.
Alveoli features for gas exchange include
·
Many small alveoli
– creates a large surface area which increases
rate of diffusion
·
T
hin alveoli walls
– simple epithelium allows less distance for gases
to diffuse across and therefore increased rate of diffusion
·
Extensive blood capillary network
–wrapped around the alveoli
creating a large surface area for
gas exchange
between the blood
and alveoli.
·
Moist surface
– gases dissolve allowing for faster rate of diffusion.
Maintenance of gas concentration gradient
b
etween air in alveoli and
blood in capillaries
·
Heart is always pumping - allows for a constant flow of blood to and
from lungs. Blood passing the lungs will always have a low O
2
concentration and a high CO
2
concentration
·
Constant
breathing
replaces O
2
and expels CO
2
. Air in the lungs will
always have a high O
2
concentration and a low CO
2
concentration
·
Cellular
respiration
uses O
2
and produces CO
2
as a waste, which
returns to lungs in deoxygenated blood
