The Mammalian Respiratory System
Function: To transport gases to and from the circulatory system
Respiration: all parts of the process that supplies O2 to the body cells and rids the body of CO2
-involves the diffusion of gases across a semi-permeable membrane
Breathing: the actual mechanism of gas exchange
Respiration
Breathing
Inspiration
External
Respiration
Internal
Respiration
Cellular
Respiration
Expiration
In humans, breathing involves 2 movements:
 1) Inspiration (Inhalation): air moves in
 2) Expiration (Exhalation): air moves out
External respiration – exchange of O2 and CO2 between air and blood
Internal Respiration – exchange of O2 and CO2 between blood and cells of the surrounding tissues
Cellular respiration – chemical reactions in the mitochondria that yield ATP
O2 + C6H12O6 → CO2 + ATP + H2O
The Path of an Air Molecule:
THE UPPER RESPIRATORY TRACT
•Nasal Cavity/ Nasal Passages
-located above the roof of the mouth
-air enters the nostrils, mouth/oral cavity and enters
the nasal passages
Turbinates
-thin bones, hang suspended from nasal chambers
-increase surface area of chambers
-covered with a thin membrane that secretes mucus
which moistens the air
Capillaries
-line the nasal passages
-warm incoming air, increase relative humidity
-this protects delicate lung tissues
Cilia
-nasal passages also lined with small hairs called cilia
-cilia trap dust and foreign particles, are swept into
throat by the cilia where they are swallowed
•Pharynx
-tube at the back of the mouth and nasal cavities
-intersection of the esophagus (digestive system) and the
trachea (respiratory system)- the pharynx contains
passageways for both food and air
-connects the mouth and nasal cavity to the larynx and
the trachea/esophagus
•Epiglottis
-protects the glottis (and ultimately the opening to the
trachea)
--flap-like piece of cartilage
-when food is swallowed, the epiglottis presses down
and covers the opening to the trachea- this prevents
food from going down your trachea (choking)
•Glottis
-the opening of the trachea
-conducts air to the lungs
•Larynx
--located at the upper end of the trachea
-also known as the voice box
-contains two folded ligaments that stretch across the larynx, held in place by the cartilage on the
larynx walls
-two ligaments are known as the vocal cords
-sound are produced when air is forced past the ligaments, they vibrate, and the pitch and volume of
sound varies with the amount of tension on the vocal cords and the amount of air being forced by
them
-when breathing: large gap b/w cords
-when speaking: small gap b/w cords- muscles around larynx contract
Long vocal cord→low sound, Short Vocal Cord→ high sound
Refer also to figure 8.13 page 257
•Trachea
- a long tube made up of cartilage that connects the nasal cavity/mouth/pharynx/larynx to the lungs
-usually about 10-12cm long
-often called the windpipe in mammals
-lined with epithelial cells that contain cilia, and that produce mucus
Mucus
-secreted by epithelial ciliated cells
-traps foreign particles
-beating/waving of cilia help to propel material back into the nose and throat where it is expelled by
a cough or a sneeze
-cold= increased mucus=blowing of your
nose
THE LOWER RESPIRATORY TRACT
•Bronchi (plural is bronchi, if you talk about
only one it is called a bronchus)
-the bottom of the trachea branches into the
left bronchus (for left lung) and the right
bronchus (for right lung)
-surrounded by a layer of smooth musclesmooth muscle contraction and relaxation
causes changes in air flow
-lined with cilia/mucus to keep passageway
clear and acts a filter
-branching increases surface area
•Bronchioles
-passageways that branch from the bronchi into the separate
lobes of the lungs
-increase surface area
-smallest tubes
-lined with cilia and mucus membranes
-divide into smaller and smaller and smaller passageways
that carry air into all portions of the lungs
•Alveoli (plural is alveoli, if you talk about only one it is
called an alveolus), 300 million in one lung!
-grape like clusters of air sacs at the end of each bronchiole
-always kept moist, site of gas exchange, diffusion of gases
occurs here
-wall of each cell is only one cell thick
-each alveolus is surrounded by a capillary bed, gas exchange
occurs via diffusion across the alveolus cell wall into the
surrounding capillaries
-oxygen from outside air → pulmonary venules →heart →
pumped to body
-carbon dioxide from pulmonary arterioles→ breathe out
•Elastic Connective Tissues- fill spaces between individual structures to keep the entire arrangement
in position (like anchors)
-alveoli are filled with a lubricating film that helps to keep them from collapsing
•Lungs
-located deep within the body, protected from water
loss and damage by bone and muscles of the
thorax/rib cage
-many folds and fine membranes, delicate, fragile
-air moves from the external environment to the
respiratory surface deep inside the mammal
--each lung is divided into lobes
Right Lung: 3 lobes, Left Lung: 2 lobes
-each lobe is subdivided into lobules, each lobule
has its own bronchiole
•Pleura (singular pleuron)
-thin double membrane that surrounds the
lungs, still allows them to expand and contract
during breathing
-each pleuron consists of two layers separated
by a thin lubricating fluid
Pleurisy- condition in which the pleura may
become inflamed
Cystic Fibrosis- a disease in which too much
mucus is produced- the gas exchange surface is
reduce and eventually all the alveoli become
blocked
Lung Cancer- prevents normal cleaning process,
cells are not repaired, leads to cancer