2. INTRODUCTION:
Respiration is the process by which oxygen
from lungs is carried by blood to the tissue ,
and carbon dioxide formed in the tissues by
metabolic activity is carried by blood to the
lungs and is expired out.
PROCESS OF
RESPIRATION:
1.Ventilation
2.Intrapulmonary gas-mixing
3.Diffusion
4.Perfusion
4. CYCLES OF RESPIRATION:
This occurs 12 to 15 times per minute and consist of
three phases.
1. INSPIRATION: Inhalation of air or breathe in.
2. EXPIRATION : Exhalation of air or breathe out.
3. PAUSE.
5. COMPOSITION OF AIR:
Air is a mixture of gases , nitrogen ,oxygen , carbon dioxide, water vapour
and small quantities of inert gases.
The percentage of each is listed in the table.
composition of inspired and Expired air
Inspired air % Expired air %
Oxygen 21 16
Carbon dioxide 0.04 4
Nitrogen & rare
gases
78 78
Water vapour Variable Saturated
6. ORGAN OF RESPIRATORY
SYSTEM:
NOSE AND NASAL CAVITY.
PHARYNX.
LARYNX.
TRACHEA.
PAIR OF BRONCHI.
BRONCHIOLES
LUNGS AND PLUERA(covering).
7. 1.NOSE AND NASAL CAVITY:
Position: The nose is the organ of smell located in the middle of the face while the
nasal cavity lies above the roof of the mouth.
Structure: Nasal cavity is an irregular cavity divided into two equal passages by a
SEPTUM.
Posterior bony part: It is a perpendicular plate of Ethmoid bone and Vomer.
Anterior bony part: It consist of Hyaline cartilage.
Roof: It is formed by cribriform plate of the ethmoid bone and sphenoid bone,
frontal and nasal bone.
Floor :It is formed by the roof of the mouth and consist of hard palate(maxilla and
palatine bones) in front and the soft palate(involuntary muscle) behind.
Walls: medial wall-septum
Lateral wall- maxilla and ethymoid bone
Posterior wall- pharynx
9. OPENINGS INTO THE NASAL CAVITY:
Anterior nares or nostrils: Opening from the exterior into the nasal cavity.
Posterior nares : Opening from the nasal cavity into the pharynx.
Paranasal sinus: Cavities in the bones of face and the cranium which contain air .
The main sinuses are ,maxillary sinus (lateral walls),frontal and sphenoidal
sinuses(roof) , ethmoid sinus (upper part of the lateral walls).
FUNCTIONS:
1. Respiratory function:
The nose is the first of the respiratory passages through which the inspires air
passes. The function of the nose is to begin the process by which the air is warmed ,
moistened , and filtered.
2. Olfactory function:
The nose is the organ of the sense of smell.There are nerve endings in the roof of
the nose which are stimulated by the chemical substances given off by odorous
material.The resultant impulses are conveyed by olfactory nerves to the brain where
the sensation of smell is perceived.
10. PHARYNX
POSITION:
It is muscular tube
12 cm in length
Extends from the base of the skull to the level of the 6th
cervical vertebra.
It lies behind the nose, mouth and larynx
It is wider at its upper end.
12. NASOPHARYNX: The nasal part of the pharynx lies behind the nose bove the level of soft
palate. On its lateral walls are two openings of the auditory tubes one leading to each middle ear. On
the posterior wall are the pharyngeal tonsils (adenoids), consist of lymphoid tissue. They are more
prominent in children upto approx. 7 years of age there after they gradually atrophy.
OROPHARYNX:The oral part of the pharynx lies behind the mouth extending from below the level
of soft palate to the level of the upper part of the body to the 3rd cervical vertebra. Th e lateral wall of
the pharynx blend with the soft palate to form two fold on each side. Between each pair of fold os the
collection of lymphoid tissue called the
palatine tonsil. During swallowing the
nasal and oral part are separated by
the soft palate and uvula.
THE LARYNGOPHARYNX: The laryngeal
part of the pharynx extends from the
oropharynx above and continues as the
oesophagus below i.e, from the level of the
3rd to the 6th cervical vertebra.
13. STRUCTURE
The walls of the pharynx contain several types of tissue.
Mucous membrane lining
Submucosa
Smooth muscle
14. BLOOD AND NERVE SUPPLY
Blood is supply to the pharynx by several branches of facial artery. The venus return is into
the facial and internal jugular veins.
The nerve supply is from the pharyngeal plexus, formed by parasympathetic and sympathetic
nerves. Parasympathetic supply is by the vagus and glossopharyngeal nerves. Sympathetic
supply is by nerves from the superior cervical ganglia.
FUNCTIONS:
Passageway for air and food
Warming and humidifying
Hearing
Protection
speech
15. LARYNX
The larynx or ‘voice box’ links the laryngopharynx
and the trachea. It lies at the level of the
3rd ,4th ,5th and 6th cervical vertebrae.
Until puberty there is a little difference in size
of the larynx between the sexes, thereafter,
it grows larger in the male, which explain the
prominence of the ‘Adams apple’ and
the generally deeper voice.
16. STRUCTURE
CARTILAGES:
larynx is composed of several irregularly shaped cartilages attached to each other by
ligaments and membranes.
The main cartilages are:
Thyroid cartilage (1) The
Cricoid cartilage (1)
Arytenoid cartilages (2)
Epiglottis (1)
18. THE THYROID CARTILAGE: This is the most prominent of the laryngeal cartilages. Made
of hyaline cartilage, it lies to the front of the neck. Its interior wall projects into the soft tissue of the
front of the throat, forming the laryngeal prominence or Adam’s apple, which is easily felt and
often visible in adult males. The anterior wa’ll is partially divided by the thyroid notch, the cartilage
is incomplete posteriorly, and is bound with ligaments to the hyoid bone above and cricoid
cartilage below.
The upper part of the thyroid cartilage is lined with stratified squamous epithelium like the larynx,
and the lower part with ciliated columnar epithelium like the trachea. There are many muscles
attached to its outer surface.
THE CRICOID CARTILAGE: This lies below the thyroid cartilage and is also composed of
hyaline cartilage. It is shaped like a signet ring, complete encircling the larynx with the narrow part
anteriorly and the broad part posteriorly. The broad posterior part articulates with the arytenoid
cartilages and with the thyroid cartilage. It is lined with ciliated columnar epithelium and there are
muscles and ligaments attached to its outer surface. The lower border of the cricoid cartilage
marks the end of the upper respiratory tract.
19. THE ARYTENOID CARTILAGES: These are two roughly pyramid shaped hyaline cartilages
situated on the top of the broad part of the cricoid cartilage forming part of the posterior wall of
larynx. They give attachment to the vocal cords and to muscles And are lined with ciliated columnar
epithelium.
THE EPIGLOTTIS: This is a leaf shaped fibroelastic
cartilage attached on a flexible stalk of cartilage to
the inner surface of the anterior wallof the thyroid
cartilage immediately below the thyroid notch.
It riseobliquely upwards behind thetongue and the
body of the hyoid bone. It is covered with stratified
squamous epithelium.If the larynx is likened to a box
then the epiglottis acts as the lid; it closes off the
larynx during swallowing, protecting the lungs from
the accidental inhalation of foreign o bjects.
20. BLOOD AND NERVE SUPPLY:
Blood is supply to the larynx by the superior and inferior laryngeal arteries and drained by the
thyroid veins, which join the internal jugular vein.
The parasympathetic nerve supply is from the superior cervical ganglia, one on each side. These
provide the motor nerve supply to the muscles of the larynx and sensory fibres to the lining
membrane.
INTERIOR OF THE LARYNX:
The vocal cords are two Pale folds of
mucous Membrane with cord like free
edges, which extends from the inner wall
of the thyroid prominence anteriorly to
the arytenoid cartilages posteriorly.
21. When the muscles controlling the vocal cords are
relaxed, the vocal cords open and the passage
way for air coming up through the larynx is clear;
the vocal cords are said to be abducted (open).
The pitch of the sound produced by vibrating the
vocal cords in this position is low. When the
muscles controlling the vocal cords contract, the
vocal cords are stretched out tightly across the
larynx, and are said to be adducted (closed).
When the vocal cords are stretched to this extent,
and are vibrated by the air passing through from
the lungs, the sound produced is high pitched.
The pitch of the voice is therefore determined by
the tension applied to the vocal cords by the appropriate sets of muscles. When not in use, the
vocal cords are adducted. The space between the vocal cords is called the glottis.
22. Production of sound:
Speech:
Protection of the lower respiratory tract:
Passageway for air:
Humidifying, filtering and warming:
FUNCTIONS:
24. Begins-in the neck below the cricoid cartilage of the
larynx.
Extends to carina
lined by ciliated columnar epithelium.
10 to 11 cm long and lies mainly in the median plane in
front of the oesophagus.
It then divides into two smaller tubes known as bronchi;
each lung having a bronchus.
Each time you inhale, the trachea slightly lengthens and
widens, and it goes back to its normal size whenever you
exhale
25. STRUCTURES ASSOCIATED WITH
TRACHEA
Superiorly- the larynx
Inferiorly- the right and left bronchi
Anteriorly-upper part: the isthmus of the thyroid gland-
lower part: the arch of the aorta and the sternum
Posteriorly- the esophagus separates the trachea from
the vertebral column.
Laterally-lungs
26. STRUCTURE
Trachea is composed of 3 layers of tissue (C-shape)
rings of hyaline cartilage lying one above another.
The rings are incomplete posteriorly.
Connective tissue and involuntary muscle join the
cartilages and form the posterior wall where the rings
are incomplete.
27. Three layers of
tissue “CLOTHE” the
cartilages of the trachea.
The outer layer
consists of fibrous
and elastic tissue
and encloses the
cartilages.
The middle layer
consists of cartilages
and bands of
smooth muscle that
wind round the
trachea in a helical
arrangement.
The inner lining
consists of ciliated
columnar epithelium,
containing mucus-
secreting goblet
cells.
28. Blood and nerve supply, lymph drainage
BLOOD SUPPLY-
Arterial supply-The inferior thyroid and bronchial arteries.
Venous drainage: Inferior thyroid veins into the brachiocephalic veins.
NERVE SUPPLY-
Para sympathetic nerve supply :
The recurrent laryngeal nerves and other branches of the vagi.
Para sympathetic stimulation constricts the trachea.
Sympathetic nerve supply:
Nerve supply from the sympathetic ganglia.
Sympathetic stimulation dilates the trachea.
LYMPHATIC SUPPLY:
Lymph from the respiratory passages drains through lymph nodes situated round the
trachea and in the carina.
The area where it divides into two bronchi.
29. FUNCTIONS
SUPPORT AND PATENCY :
The arrangement of cartilage and elastic tissue prevents kinking and obstruction of the
airways as the head and neck move.
COUGH REFLEX.
Nerve endings in the larynx, trachea and bronchi are sensitive to irritation, which generates
nerve impulses conducted by the vagus nerves to the respiratory centre in the brain stem.
WARMING, HUMIDIFYING AND FILTERING.
When the air is cold, the trachea helps to humidify and warm the air entering the lungs. When
the air is hot, heat is carried away in exhaled air through evaporation of water.
30. LUNGS
Lungs are pair of respiratory organs situated in
thoracic cavity. right and left lung are separated
by the mediastinum.
Texture- spongy
Color- young- brown
adults- melted black due to the position
carbon particles.
MEASURMENTS
SHAPE: CONE
REGIONS : apex, base, coastal surface, medial
surface.
31. APEX: It is rounded and rises into the root of the neck.
It lies close to the first rib and blood vessels and nerves in the root of the neck.
THE BASE: This is concave and semilunar in shape.
Lies on the thoracic surface of the diaphragm.
THE COSTAL SURFACE: This surface is convex in shape.
Lies against the costal cartilages, the ribs and the intercostals muscles.
THE MEDIAL SURFACE: This surface is concave and roughly triangular-shaped area called “HILUM”.
It lies at the level of the 5th,6th and 7th thoracic vertebrae.
It is occupied by the heart,, trachea, right and left bronchi, oesophagus, lymph nodes, lymph vessels and nerves.
32. The right lung is divided into three distinct lobes
Superior lobe
Middle lobe
Inferior lobe
The left lung is smaller because the heart occupies space
left of the midline.
v It is divided into two lobes
SUPERIOR And INFERIOR LOBE.
34. PLEURA AND PLEURAL CAVITY
The pleura consists of a closed sac of serous membrane(one for each lung) which
contains a small amount of serous fluid. The lung is invaginated (pushed into)
this sac so that it forms two layers:
THE VISCERAL PLEURA: This is adherent to the lung, covering each lobe and
passing into the fissures that separate them.
THE PARIETAL PLEURA: This is adherent to the inside of the chest wall and the
thoracic surface of the diaphragm. It remains detached from the adjacent
structures in the mediastinum and continous with the visceral pleura round the
edges of the hilum.
35. THE PLEURAL CAVITY: The pleural cavity is a potential space
between the visceral and parietal pleura that contains thin
layer of fluid.
Two pleural cavities are situated on either side of the
mediastum.
During development the lungs grow out of the mediastum,
becoming surrounded by the pleural cavities.
36. BLOOD SUPPLY:
Arterial supply-The pulmonary trunk divides into the right and left
pulmonary arteries, it carries pure blood.
VENOUS DRIANAGE :two pulmonary bronchial veins carry the de-
oxygenated blood.
NERVE SUPPLY:
PARASYMPATHETIC NERVE SUPPLY: The vagus nerves stimulate
contraction of smooth muscle in the bronchial tree
causing BRONCHOCONSTRUCTION.
SYMPATHETIC NERVE SUPPLY: Stimulation causes
BRONCHODILATATION.
LYMPHATIC SUPPLY : Lymph is drained from the walls of the air
passages in a network of lymph vessels.
It passes through lymph nodes situated around the trachea and bronchial
tree then into the thoracic duct on the left side and right lymphtic duct on
the other.
40. Conducting zone structure
Trachea, primary, lobar,
segmental bronchi, and
terminal bronchiole
together represent as
conducting zone passage
where air conduction is
done.
41. The tissue composition of walls of primary bronchi similar to the
trachea.
However , as conducting tube becomes smaller, the following structural
changes occur-
Support structure changes
Epithelium type change
Amount of smooth muscle increases
42. Respiratory zone structure
Defined by presence of thin walled air sacs called alveoli, the
respiratory zone begins as terminal bronchioles divides into
respiratory bronchioles within lung.
Respiratory bronchioles lead into winding alveolar ducts, whose
walls consist of diffusely arranged rings of smooth muscle cells,
connecting tissue fibers, and outpocketing alveoli.
The alveolar duct lead into terminal cluster of alveoli called
alveolar sacs.
44. Alveoli and Respiratory Membrane
Walls of the alveoli are composed of a single layer of squamous
epithelial cells called type I alveolar cells.
External surfaces of alveoli are densely covered with pulmonary
capillaries.
Capillary and alveolar wall and their fused basement membranes form
that respiratory membrane.
It is thick blood air barrier.
45. Gas exchanges occur readily by simple diffusion across the
respiratory membrane.
Type II alveolar cells secrete surfactant that coat the gas exposed
alveolar surfaces.
It also secrete number of antimicrobial proteins that are important
elements of innate immunity.
47. Alveoli have three significant features :
They are surrounded by fine elastic fibers of the same type that
surround the entire bronchial tree.
Open alveolar pores connecting adjacent alveoli allow air pressure
throughout the lung to be equalized and provide alternate air route
to any alveoli whose bronchi collapsed due to disease.
Remarkably efficient alveolar macrophages present freely along the
internal alveolar surfaces.
48. Functions
• Control Of Air Entry
• Warming And Humidifying
• Support And Patency
• Removal Of Particulate Matter
• Cough Reflex
49. EXTERNAL AND INTERNAL
RESPIRATION:
The physiological role of respiration is to
supply the tissues with oxygen and remove
carbon dioxide wastes from them.
To do so, the lungs must periodically take in
fresh air and expel used air . Thus
respiration may be said to have two phases
or to function at two levels in the body i.e.
A. EXTERNAL RESPIRATION
B. INTERNAL RESPIRATION
50. A. EXTERNAL RESPIRATION
(BREATHING)
External respiratory system
concerned with getting air into and
out of the lungs
It follows the path of inspired air
i.e. through the nose and mouth,
into the pharynx (throat), on
through the larynx (voice box),
down the trachea (windpipe)and
into the bronchial tubes leading
into the lungs.
51. MECHANISM OF BREATHING.
It is based on Boyle’s law , which says that “if the volume of the container is
increased, the pressure within it decreases.”
Inspiration: volume of the thorax increases as the pressure within it decreases so
the air flows into the lungs.
Expiration: volume of the thorax decreases as the pressure within it increases so
the air is forced out.
Action of diaphragm.
Inspiration - contraction of diaphragm.
Expiration - relaxation of diaphragm.
Action of ribs.
Inspiration – outward and upward excursion of ribs(ribs 2 through 10)
Expiration – downward slope of the relaxed ribs.
52. THE AIR WE BREATHE.
When the speaking of the amount of air in the lungs, it is often advisable to be
more specific, since this amount depends on whether the person was breathing
naturally or forcefully.
The following are semi-official terms used by physiologists,
Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Vital capacity
Residual volume
53. B . INTERNAL RESPIRATION
Internal respiration involves the following
1. The passage of oxygen from the lungs into the bloods.
2. Transporting oxygen to the tissues.
3. Passage of oxygen into the tissues from the blood.
54. TRANSPORT OF GASES IN THE
BLOODSTREAM.
To enter the bloodstream, oxygen must pass
through the alveolar membrane and then through
the capillary wall.
The blood then transport it to the tissues where
again it must diffuse through wall of the capillary,
into the tissue fluid, and into the cell.
The same is true of carbon dioxide in the reversed
direction.
This passage of oxygen in one direction and of
carbon dioxide in other is referred to as the
interchange of gases.
55. Bibliography
Chatterjee C.C, Human Physiology : Medical Allied Agency.
Guyton and Hall : Testbook of Medical Physiology,9th Edition
Tortora: Principles of Anatomy and Physiology.
Ross and Wilson: Anatomy and Physiology in Health and Illness.
Fred E.D’Amour, Frank R.Blood: Manual for Laboratory Work in
Mammalian Physiolology.