lecture 1: general introduction of our respiratory system

1. INTRODUCTION TO
RESPIRATORY SYSTEM
23-9-2019

2. • The primary function of the lung is gas exchange,
which consists of movement of O2 into the body and
removal of CO2 from the body.
• The lungs are contained in a space with a volume of
approximately 4 L (~ 6-8L), but they have a surface
area for gas exchange that is the size of a tennis court
(∼85 m2).
• In adults, the lung weighs approximately 1 kg.
• The first breath takes place only after birth, because
during intra-uterine life the placenta place a role for
gas exchange b/w fetal and mother.
• Permanent stoppage of respiration occurs only at
death.

3. • The respiratory system starts from the nose and
ends to the alveoli.
• The respiratory tract (System) is divided into:
1. The upper airways system: includes all structures
from nose to larynx (nose, nasal cavity, pharynx,
part of larynx above vocal cords).
2. The lower airways system: includes all structures
from below larynx (part of larynx below vocal cords,
trachea, bronchi, bronchioles and lungs).
• Ventilation (Respiration): is movement of air in and
out of the lungs in the environment.
• Respiratory unit: respiratory bronchioles, alveolar
ducts, alveolar sacs, antrum, alveoli.
• Respiratory Membrane: where the gas exchange
occurs. Formed by 1) alveolar membrane and 2)
capillary membrane.

5. • The Types Of Respiration:
1. External respiration: involves exchange of respiratory
gases, i.e. oxygen and carbon dioxide between lungs and
blood.
2. Internal respiration: which involves exchange of gases
between blood and tissues.
• The Phases Of Respiration:
1. Inspiration : during which air enters the lungs from
atmosphere.
2. Expiration : during which air leaves the lungs to
atmosphere.
• The Stages Of Respiration:
1. Ventilation Stage.
2. Transport Stage.
3. Exchange Stage.
4. Tissue Stage.

6. Stages of
Respiration:
1. Ventilation Stage.
2. Transport Stage.
3. Exchange Stage.
4. Tissue Stage.

7. • Physiologically, breathing is of two types:
A) Abdominothoracic Breathing:
• Usually seen in males.
1. During inspiration, diaphragm descends that pushes
abdominal viscera down and, therefore, abdominal wall is
raised.
2. Thus, abdominal movement becomes prominent. Contraction
of abdominal muscles facilitates breathing.
B) Thoracoabdominal Breathing:
• This is predominant in females and children, as in them the
movement of the chest wall is prominent during respiration.
1. In females, descent of diaphragm is resisted by the abdominal
viscera; the exact cause of which is not known. Therefore,
there is increased movement of the rib cage that increases
thoracic cage volume.
2. One contributing factor may be the free mobility of the ribs at
sternocostal and costovertebral joints in females compared to
males.

8. • The airways beyond the larynx can be divided into
two zones:
1- Conducting zone: extends from the top of the
trachea to the end of the terminal bronchioles.
• This zone contains no alveoli and does not exchange
gases with the blood.
2- Respiratory zone: extends from the respiratory
bronchioles down.
• This zone contains alveoli and is the region where
gases exchange with the blood

9. The conducting zone:
• The conducting zone includes the nose, nasopharynx, larynx,
trachea, bronchi, bronchioles, and terminal bronchioles.
• These structures function to:
 Bring air into and out of the respiratory zone for gas
exchange
 To warm, humidify.
 Filter the air before it reaches the critical gas exchange
region.
• The trachea, which is the main conducting airway.
• The conducting airways are lined with mucus-secreting and
ciliated cells that function to remove inhaled particles.

10. Continueeeee:
• The walls of the conducting airways contain
smooth muscle.
• This smooth muscle has both sympathetic and
parasympathetic innervations, which have
opposite effects on airway diameter:
(1) Sympathetic adrenergic neurons activate β2
receptors on bronchial smooth muscle, which
leads to relaxation and dilation of the airways.
(2) Parasympathetic cholinergic neurons activate
muscarinic receptors, which leads to contraction
and constriction of the airways.
N.B:

11. Generation
Numbers:
1. The airways become
smaller, narrower and
shorter.
2. The amount of cilia
decreases.
3. The number of mucus
secreting cells decreases.
4. The quantity of
submucosal glands becomes
less.
5. The amount of cartilage in
the airway wall decreases.
6. The quantity of smooth
muscle increases.

13. The Respiratory Rate:
• Is a Rhythmical of cyclical alteration b/w
inspiration and expiration.
• Respiratory rate are different at any age.

14. Pleura (Pleural sac):
• Is bilayered serous membrane that encloses (covers) each lung..
• Pleura layers:
1. Inner Visceral Layer: that attached firmly to the surface of the
lungs.
2. Outer Parietal Layers: that attaches to the wall of thoracic
cavity.
• Intrapleural Space or Pleural Cavity: the narrow space in
between the two layers of pleura.
• Intrapleural Fluid: thin film of serous fluid, which is secreted by
the visceral layer.
• N.B:
 Intrapleural fluid serve as lubricant to prevent friction between
two layers of pleura (during respiration).
 Intrapleural fluid serve creating the negative pressure called
intrapleural pressure within intrapleural space

15. Alveolar Cells or Pneumocytes:
• Alveolar epithelium divided into 2 types of cells:
1- Type I alveolar cells:
• 95% of alveolar cells.
• Squamous epithelial cells.
• Site of gaseous exchange between the alveolus and
blood.
2- Type II alveolar cells (granular pneumocytes):
• 5% of alveolar cells.
• Cuboidal epithelial cells.
• Secrete alveolar fluid and surfactant.

16. Muscular Wall of the Bronchi and
Bronchioles and Its Control.
• In all areas of the trachea and bronchi not occupied
by cartilage plates, the walls are composed mainly of
smooth muscle.
• Also, the walls of the bronchioles are almost entirely
smooth muscle, with the exception of the most
terminal bronchiole, called the respiratory
bronchiole, which is mainly pulmonary epithelium
and underlying fibrous tissue plus a few smooth
muscle fibers.
• Many obstructive diseases of the lung result from
narrowing of the smaller bronchi and larger
bronchioles, often because of excessive contraction
of the smooth muscle.

17. RESPIRATORY PROTECTIVE
REFLEXES:
• Are the reflexes that protect lungs and air
passage from entry and expel the foreign
particles.
• Following are the respiratory protective
reflexes:
1. Cough Reflexes.
2. Sneezing Reflexes.
3. Swallowing Reflexes.

18. 1- Cough Reflexes:
1. First, up to 2.5 liters of air are rapidly inspired.
2. Second, the epiglottis closes, and the vocal cords shut tightly
to entrap the air within the lungs.
3. Third, the abdominal muscles contract forcefully, pushing
against the diaphragm while other expiratory muscles, such
as the internal intercostals, also contract forcefully.
4. Fourth, the vocal cords and the epiglottis suddenly open
widely, so that air under this high pressure in the lungs
explodes outward.

19. 2- SNEEZING REFLEX:
• Irritation of the nasal mucous membrane occurs
because of dust particles, debris, mechanical
obstruction of the airway and excess fluid
accumulation in the nasal passages.
• Same as mechanism in cough production.
• Sneezing center is in medulla oblongata and
some in spinal nucleus.

20. 3- SWALLOWING (DEGLUTITION)
REFLEX:
• Swallowing reflex is a respiratory protective
reflex that prevents entrance of food particles
into the air passage during swallowing.
• While swallowing of the food, the respiration
is arrested for a while.
• Arrest of breathing during swallowing is called
swallowing apnea or deglutition apnea.

21. 2. OLFACTION:
“Olfactory sensation”
3. VOCALIZATION:
“Speech apparatus”
4. PREVENTION OF DUST PARTICLES:
“filtration action of the hairs in nasal”
“Phagocytic action of macrophages”
“Cough reflex and sneezing reflex”
5. MAINTENANCE OF
WATER BALANCE:
“H2O evaporation”
6. REGULATION OF
BODY TEMPERATURE:
“Heat loss mechanism”
7. ANTICOAGULANT FUNCTION:
“Mast cells secrete Heparin”
8. REGULATION OF ACID-BASE BALANCE:
9. SECRETION OF ANGIOTENSIN
CONVERTING ENZYME
10. SYNTHESIS
OF HORMONAL
SUBSTANCES:
“prostaglandins,
acetylcholine
and serotonin”
11. DEFENSE MECHANISM:
“leukocytes, macrophages,
mast cells, natural killer
cells and dendritic cells”.
1. Gas exchange:
O2 CO2