Nose Pharynx Trachea Lungs

1. RESPIRATORY SYSTEM
Nose
Pharynx
Trachea
Lungs

2. NOSE AND PHARYNX
 Begins with the nose, where air is conditioned by warming and
moistening.
 Bone partitions separate the nasal cavity into chambers
 Hairs and hairlike cilia trap dust particles and purify the air.
 The nasal chambers open into a cavity at the rear of the mouth called the
pharynx (throat).
 Two tubes called Eustachian tubes open to the middle ear to equalize air
pressure.
 Pharynx also contains tonsils and adenoids, which are pockets of
lymphatic tissue used to trap and filter micro-organisms.

3. TRACHEA
 After passing through the pharynx, air passes into the windpipe, or
trachea.
 Framework of smooth muscle.
 Slitlike structure called the glottis.
 A thin flap of tissue called the epiglottis.
 At the upper end of the trachea, several folds of cartilage form the larynx,
or voicebox.
 In the larynx, flaplike pairs of tissues called vocal cords vibrate when a
person exhales and produce sounds.
 Two large bronchi (singular, bronchus).
 These tubes also have smooth muscle and cartilage rings.
 The bronchi branch into smaller bronchioles, forming a bronchial “tree.”
 Bronchioles terminate in the air sacs known as alveoli.
 The bronchial tree continues branching until it reaches the level of
terminal bronchioles, which lead to alveolar sacs.

4. LUNGS
 The bronchioles, their branches and air sacs are enclosed in a double
membrane called pleural membrane to form the lungs. The lungs are
main respiratory organs.
 Air passes through the nostrils into bronchi, to bronchioles and into air
sacs which are thin walled sacs with a single layer of cells and heavily
covered with a single layer of cells and heavily covered with blood
capillaries.
 O2 from alveoli passes into capillaries and CO2 from other capillaries
diffuses into alveoli for being removed. The alveoli are the organs where
the actual gaseous exchange occurs.
 The double layer pleural membrane covers the lungs for its protection. It
contains pleural fluid, which makes the movement of lungs easy.
 Each lung consists of a tree like system of branched bronchial tubes.
 The finest of them terminate into million of tiny sac like structure called
alveoli.
 Alveolar membrane is very thin, moist and richly supplied with blood
capillaries.
 The walls of both the capillaries and alveoli consist of a single layer of
flattened epithelial cells.

6. Respiratory system

9. The Respiratory pathway
Nostrils Nasopharynx Oropharynx
Bronchioles Bronchi Trachea Glottis
Alveoli

10. THE MECHANISM OF RESPIRATION
Intercostal muscles of ribs contract
lifting the ribs up and out
Muscles of diaphragm contract and it
is pulled down.
The volume of pleural cavity is
increased and air pressure
decreases leading to inhalation of
air.
Inhalation

11. THE MECHANISM OF RESPIRATION
Intercostal muscles of ribs relax
bringing ribs to their normal position
Muscles of diaphragm relax pulling it
back to normal position.
The volume of pleural cavity is
decreased and air pressure
increases leading to expiration of air.
Expiration

12. Composition of atmospheric air and expired air
in a typical subject.
Component Atmospheric Air (%) Expired Air (%)
N2 (plus inert gases) 78.62 74.9
O2 20.85 15.3
CO2 0.03 3.6
H2O 0.5 6.2
100.0% 100.0%

13. CENTRAL CONTROL OF BREATHING
• The rate of cellular respiration (and hence oxygen
consumption and carbon dioxide production) varies with
level of activity.
• It is a rising concentration of carbon dioxide — not a
declining concentration of oxygen — that plays the major
role in regulating the ventilation of the lungs. Certain cells
in the medulla oblongata are very sensitive to a drop in
pH.
• However, the carotid body in the carotid arteries does
have receptors that respond to a drop in oxygen. Their
activation is important in situations (e.g., at high altitude
in the unpressurized cabin of an aircraft) where oxygen
supply is inadequate but there has been no increase in
the production of CO2.

14. NON RESPIRATORY FUNCTIONS OF LUNGS
In addition to their function in respiration, the lungs also:
• Alter the pH of blood by facilitating alterations in the partial
pressure of carbon dioxide
• Filter out small blood clots formed in veins
• Filter out gas micro-bubbles occurring in the venous blood stream
such as those created during decompression after underwater
diving .
• Influence the concentration of some biologic substances and
drugs used in medicine in blood
• Convert angiotensin I to angiotensin II by the action of
angiotensin-converting enzyme
• May serve as a layer of soft, shock-absorbent protection for the
heart, which the lungs flank and nearly enclose.

15. • Immunoglobulin-A is secreted in the bronchial secretion and
protects against respiratory infections.
• Maintain sterility by producing mucus containing antimicrobial
compounds. Mucus contains glycoproteins, e.g. mucins,
lactoferrin, lysozyme, lactoperoxidase. We find also on the
epithelium Dual oxidase 2 proteins generating hydrogen
peroxide, useful for hypothiocyanite endogenous antimicrobial
synthesis. Function not in place in cystic fibrosis patient
lungs.
• Provide airflow for the creation of vocal sounds.
• Thermoregulation (panting)