Download The Mammalian Respiratory System

Biology-lecture 11-----------------------------------------------------------------Dr. Ahmed MA. Nazar
The Mammalian Respiratory System
Respiration is the process of obtaining sufficient oxygen from the environment to support
cellular metabolic requirements.
Function: transport of oxygen from the outside air to the cells within tissues, and the
transport of carbon dioxide to the outside. It is also the metabolic process by which an
organism obtains energy by reacting oxygen with glucose to give water, carbon dioxide
and ATP.
Breathing: the actual mechanism of gas exchange.
Types of Breathing :
1. Inspiration (Inhalation): air moves in.
2. Expiration (Exhalation): air moves out.
Types of Respiration:
1. External respiration: exchange of O2 and CO2 between air and blood.
2. Internal Respiration: exchange of O2 and CO2 between blood and cells of the
surrounding tissues.
3. Cellular respiration – chemical reactions in the mitochondria that yield ATP
O2 + C6H12O6 → CO2 + ATP + H2O
The upper respiratory tract:
•Nasal Cavity/ Nasal Passages
1. Vestibule – the area surrounding the anterior external opening to the nasal cavity.
2. Respiratory region – lined by a ciliated psudeostratified epithelium, interspersed
with mucus-secreting goblet cells.
3. Olfactory region – located at the apex of the nasal cavity. It is lined by olfactory
cells with olfactory receptors.
Biology-lecture 11-----------------------------------------------------------------Dr. Ahmed MA. Nazar
4. Turbinate bones (conchae): The function of the conchae is to increase
the surface area of the nasal cavity
a) Inferior meatus: Lies between the inferior concha and floor of the nasal
cavity.
b) Middle meatus: Lies between the inferior and middle concha.
c) Superior meatus: Lies between the middle and superior concha.
d) Spheno-ethmoidal recess: Lies superiorly and posteriorly to the superior
concha.
5. Openings
a) Paranasal sinuses (The frontal, maxillary and anterior ethmoidal sinuses).
b) The middle ethmoidal sinuses.
c) sphenoid sinus.
d) nasolacrimal duct.
•Pharynx
1. tube at the back of the mouth and nasal cavities.
2. intersection of the oesophagus (digestive system) and the trachea (respiratory
system)- the pharynx contains passageways for both food and air.
3. connects the mouth and nasal cavity to the larynx and the trachea/esophagus.
Biology-lecture 11-----------------------------------------------------------------Dr. Ahmed MA. Nazar
•Epiglottis
1. protects the glottis (and ultimately the opening to the trachea).
2. flap-like piece of cartilage .
3. 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
1. the opening of the trachea.
2. conducts air to the lungs.
•Larynx
1. located at the upper end of the trachea.
2. also known as the voice box.
3. contains two folded ligaments that stretch across the larynx, held in place by the
cartilage on the larynx walls.
4. two ligaments are known as the vocal cords.
5. 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.
•Trachea
1. a long tube made up of cartilage that connects the nasal
cavity/mouth/pharynx/larynx to the lungs.
2. usually about 10-12cm long.
3. often called the windpipe in mammals.
4. lined with epithelial cells that contain cilia, that produce mucus to traps foreign
particles.
5. beating/waving of cilia help to propel material back into the nose and throat where it
is expelled by a cough or a sneeze
Biology-lecture 11-----------------------------------------------------------------Dr. Ahmed MA. Nazar
Lower respiratory tract
•Bronchi (plural is bronchi, if you talk about only one it is called a bronchus)
1. the bottom of the trachea branches into the left bronchus (for left lung) and the right
bronchus (for right lung)
2. surrounded by a layer of smooth muscle- smooth muscle contraction and relaxation
causes changes in air flow
3. lined with cilia/mucus to keep passageway clear and acts a filter
4. branching increases surface area
•Bronchioles
1. passageways that branch from the bronchi into the separate lobes of the lungs
2. increase surface area
3. smallest tubes lined with cilia and mucus membranes.
4. 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),
1. grape like clusters of air sacs at the end of each bronchiole
2. always kept moist, site of gas exchange, diffusion of gases occurs here
3. wall of each cell is only one cell thick
4. each alveolus is surrounded by a capillary bed, gas exchange occurs via diffusion
across the alveolus cell wall into the surrounding capillaries
5. oxygen from outside air → pulmonary venules →heart → pumped to body
6. carbon dioxide from pulmonary arterioles→ breathe out.
7. Elastic Connective Tissues- fill spaces between individual structures to keep the
entire arrangement in position (like anchors)
Biology-lecture 11-----------------------------------------------------------------Dr. Ahmed MA. Nazar
•Lungs
1. located deep within the body, protected from water loss and damage by bone and
muscles of the thorax/rib cage.
2. many folds and fine membranes, delicate, fragile
3. air moves from the external environment to the respiratory surface deep inside the
mammal.
4. each lung is divided into lobes: Right Lung: 3 lobes, Left Lung: 2 lobes
5. each lobe is subdivided into lobules, each lobule has its own bronchiole.
•Pleura (singular pleuron)
1. thin double membrane that surrounds the lungs, still allows them to expand and
contract during breathing
2. each pleuron consists of two layers separated by a thin lubricating fluid
In the vertebrate world, the types of respiration:
1. In unidirectional ventilation, the medium (air or water) moves across tissues in
one direction. This method is efficient because the medium is always fresh. Fish
and birds have unidirectional respiration.
2. The second type is bidirectional respiration, which implies that the medium
enters and exits through the same channel. In this case, the medium (air) contains
more waste and is not as efficient.
3. Cutaneous respiration is also possible and occurs via the skin. Cutaneous
respiration is unique in that it can occur in air or water. Amphibians utilize this
form. Each type of respiration requires modified organs and methods of
obtaining oxygen.
Definitions
1. Tidal volume is the amount of air breathed in and out of the body during
normal breathing.
2. Forced breathing, is the volume that is forced to change during exercise.
3. Vital capacity is the largest amount or volume of air that can be exhaled after
the largest possible inhalation.
4. Residual volume is the amount of air that, even after as much air as possible
has been exhaled, is left in the lungs.
Control of breathing
1. Control for rate and depth, by breathing control center which is two regions
in the brain, medulla oblongata and pone.
2. Control of Co2 concentration, by aortic and carotid arteries sensors.
Comparative respiratory mechanisms
Mammalian respiration : Compared to other species, mammalian respiration is
highly efficient; there is a very large surface area within the lungs which is
maximized by the bubble like structure of the alveoli. The lungs also benefit from
Biology-lecture 11-----------------------------------------------------------------Dr. Ahmed MA. Nazar
very thin membranes between the moist layer within the alveoli and the blood. The
blood supply to the lungs is very great .Mammals have a sealed thoracic cavity,
which is sealed by the diaphragm. In conjunction with the ribs, the two sets of
muscles are able to control breathing. Normally, the diaphragm’s relaxed position
recoils (decreasing the thoracic volume) whereas in the contracted position it is
pulled downwards (increasing the thoracic volume). This process works in
conjunction with the intercostal muscles connected to the rib cage. Contraction of
these muscles lifts the rib cage, thus aiding in increasing the thoracic volume.
Relaxation of the diaphragm compresses the lungs, effectively decreasing their
volume while increasing the pressure inside them. The intercostal muscles
simultaneously relax, further decreasing the volume of the lungs. This increased
pressure forces air out of the lungs. Conversely, contraction of the diaphragm
increases the volume of the (partially empty) lungs, decreasing the pressure inside,
which creates a partial vacuum. Environmental air then follows its pressure gradient
down to fill the lungs. The ventilation system of mammals is basically a suction
pump.
Insects are able to obtain all the oxygen they need for cellular metabolism without
lungs. Instead insects have a hard exoskeleton which contains valve like openings
called spiracles. Typically there is one pair of spiracles per body segment. Air flow
is regulated by small muscles that operate flap-like valves within each spiracle
which contract to close the spiracle, or relax to open it.
Amphibians have lungs which they use to respire, but they are also able to obtain
oxygen through their skin. As expected with a gaseous exchange surface, the skin is
thin, moist and well vascularized. Oxygen is therefore able to dissolve in the moist
layer of the skin and diffuse directly into the blood. When submerged beneath the
water surface, amphibians obtain all their oxygen through their skin.
Fish live in predominantly aquatic environments however there are exceptions, such
as the lung fish which are able to utilize lungs to obtain oxygen. Aquatic fish
however use a set of respiratory organs known as gills. Gills are highly vascularized
with a large surface area, short diffusion distance and an always moist surface.
Avian just like mammals, birds have ribs, although they lack a diaphragm to seal the
thoracic cavity. The thoracic and abdominal cavities are thus not separated and this
single large body cavity is known as the coelom.The lungs of the bird are connected
to the wall of the coelom by connective tissue and are unable to enlarge themselves
like mammalian lungs. Instead air is moved in and out of the bird by expanding the
coelom; this enlarges air sacs connected to the coelom causing air to pass through
the lungs and into the air sacs.