The document provides a comprehensive overview of the respiratory system, detailing its anatomy, including the structures involved in gas exchange, such as the nose, pharynx, larynx, trachea, bronchi, and lungs. It classifies these components into structural and functional categories, describing the significant roles they play in air conduction and gas exchange. Additionally, it discusses the applied anatomy of the trachea and bronchi, including conditions like tracheostomy and the effects of foreign bodies on bronchial pathways.

1. RESIRTORY SYSTEM
Prof. Sumi Zacharias

2. • Our cells continually use oxygen (O2) for the metabolic
reactions that release energy from nutrient molecules and
produce ATP. At the same time, these reactions release carbon
dioxide (CO2).
• The respiratory system provides for gas exchange— intake of
O2 and elimination of CO2—and the cardiovascular system
transports blood containing the gases between the lungs and
body cells.
Introduction

3. • The respiratory system consists of the nose, pharynx (throat),
larynx (voice box), trachea (windpipe), bronchi, and lungs.
• Its parts can be classified according to either structure or
function.
• Structurally - two parts:
1. The upper respiratory system includes the nose, pharynx,
and associated structures.
2. The lower respiratory system includes the larynx, trachea,
bronchi, and lungs.
THE RESIRTORY SYSTEM

4. Functional Classification
1. The conducting zone - consists of a series of interconnecting cavities and
tubes both outside and within the lungs. These include the nose,
pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles;
their function is to filter, warm, and moisten air and conduct it into the
lungs.
2. The respiratory zone - consists of tissues within the lungs where gas
exchange occurs . These include the respiratory bronchioles, alveolar
ducts, alveolar sacs, and alveoli; they are the main sites of gas exchange
between air and blood.

6. Surface anatomy of the nose.
1. Root: Superior attachment of
the nose to the frontal bone
2. Apex: Tip of nose
3. Bridge: Bony framework of
nose formed by nasal bones
4. External naris: Nostril; external
opening into nasal cavity

7. Nose - external and internal portions
• The external nose is the portion of the nose visible on the face
and consists of a supporting framework of bone and hyaline
cartilage covered with muscle and skin and lined by a mucous
membrane.
• The frontal bone, nasal bones, and maxillae form the bony
framework of the external nose.
• On the undersurface of the external nose are two openings
called the external nares (singular is naris) or nostrils.

8. The cartilaginous framework of the
external nose
• The septal nasal cartilage,
which forms the anterior
portion of the nasal septum
• The lateral nasal cartilages
inferior to the nasal bones;
• The alar cartilages, which form
a portion of the walls of the
nostrils. The external nose is
somewhat flexible.

9. The internal nose
• A large cavity beyond the nasal vestibule in the anterior aspect of the skull
that lies inferior to the nasal bone and superior to the mouth; it is lined
with muscle and mucous membrane.
• Anteriorly, the internal nose merges with the external nose, and
posteriorly it communicates with the pharynx through two openings called
the internal nares or choanae.
• The lateral walls of the internal nose are formed by the ethmoid, maxillae,
lacrimal, palatine, and inferior nasal conchae bones; the ethmoid bone
also forms the roof.
• The palatine bones and palatine processes of the maxillae, which together
constitute the hard palate, form the floor of the internal nose.

10. • The projecting conchae increase the surface area and cause
turbulence, spreading inspired air over the whole nasal surface. The
large surface area maximises warming, humidification and filtering.

12. • Ducts from the
paranasal sinuses
(which drain mucus)
and the nasolacrimal
ducts (which drain
tears) also open into
the internal nose.

13. • The space within the internal nose is called the nasal cavity.
• The anterior portion of the nasal cavity just inside the nostrils,
called the nasal vestibule, is surrounded by cartilage; the
superior part of the nasal cavity is surrounded by bone.
• A vertical partition, the nasal septum, divides the nasal cavity
into right and left sides.

14. PHARYNX
• The pharynx or throat, is a funnel-shaped tube
about 13 cm (5 in.) long that starts at the internal
nares and extends to the level of the cricoid
cartilage, the most inferior cartilage of the larynx
(voice box).
• The pharynx lies just posterior to the nasal and oral
cavities, superior to the larynx, and just anterior to
the cervical vertebrae. Its wall is composed of
skeletal muscles and is lined with a mucous
membrane.

15. Pharynx
• The pharynx can be
divided into three
anatomical regions:
1. Nasopharynx
2. Oropharynx
3. Laryngopharynx or
hypopharynx

16. Nasopharynx
• The superior portion of the pharynx, called the nasopharynx, lies
posterior to the nasal cavity and extends to the soft palate.
• The soft palate, which forms the posterior portion of the roof of the
mouth, is an arch-shaped muscular partition between the
nasopharynx and oropharynx that is lined by mucous membrane.
• There are five openings in its wall: 2 internal nares, 2 openings of
eustachian tubes, and the opening into the oropharynx.
• The posterior wall also contains the pharyngeal tonsil (adenoid).

17. Oropharynx
• The intermediate portion of the pharynx, the oropharynx, lies
posterior to the oral cavity and extends from the soft palate
inferiorly to the level of the hyoid bone.
• It has only one opening into it, the fauces, the opening from
the mouth.
• This portion of the pharynx has both respiratory and digestive
functions, serving as a common passageway for air, food, and
drink.
• Two pairs of tonsils, the palatine and lingual tonsils, are found
in the oropharynx.

18. Laryngopharynx
• The inferior portion of the pharynx, the laryngopharynx or
hypopharynx, begins at the level of the hyoid bone.
• Like the oropharynx, the laryngopharynx is both a respiratory
and a digestive pathway
• At its inferior end it opens into the esophagus posteriorly and
the larynx anteriorly.

19. Larynx
• The larynx, or voice box, is a short
passageway that connects the
laryngopharynx with the trachea.
• It lies in the midline of the neck
anterior to the esophagus and the
fourth through sixth cervical
vertebrae (C4–C6).
The wall of the larynx is composed of nine pieces of cartilage. 3 occur
singly (thyroid cartilage, epiglottis, and cricoid cartilage), and 3 occur in
pairs (arytenoid, cuneiform, and corniculate cartilages).

20. • The thyroid cartilage (Adam’s apple) consists of two
fused plates of hyaline cartilage that form the anterior
wall of the larynx and give it a triangular shape. It is
present in both males and females but is usually
larger in males due to the influence of male sex
hormones on its growth during puberty.
• The ligament that connects the thyroid cartilage to
the hyoid bone is called the thyrohyoid membrane.
• The extrinsic muscles of the larynx connect the
cartilages to other structures in the throat; the
intrinsic muscles connect the cartilages to one
another.

21. Epiglottis
The epiglottis (epi-over; glottis-tongue) is a large,
‘leaf’ shaped piece of elastic cartilage that is covered
with epithelium. The “stem” of the epiglottis is the
tapered inferior portion that is attached to the
anterior rim of the thyroid cartilage and hyoid bone.
The broad superior “leaf” portion of the epiglottis is
unattached and is free to move up and down like a
trap door.
During swallowing, the pharynx and larynx rise. Elevation of the larynx causes the
epiglottis to move down and form a lid over the glottis, closing it off.

22. Glottis
• The glottis consists of a pair of folds of mucous membrane,
the vocal folds (true vocal cords) in the larynx, and the space
between them called the rima glottidis.
• The closing of the larynx in this way during swallowing routes
liquids and foods into the esophagus and keeps them out of
the larynx and airways.

23. Cricoid Cartilage
• The cricoid cartilage (ringlike) is a ring of
hyaline cartilage that forms the inferior wall of
the larynx.
• It is attached to the first ring of cartilage of the
trachea by the cricotracheal ligament.
• The thyroid cartilage is connected to the
cricoid cartilage by the cricothyroid ligament.
• The cricoid cartilage is the landmark for
making an emergency airway called a
tracheotomy

24. Arytenoid cartilages
The paired arytenoid cartilages
are triangular pieces of mostly
hyaline cartilage located at the
posterior, superior border of the
cricoid cartilage.
They form synovial joints with
the cricoid cartilage and have a
wide range of mobility.

25. corniculate cartilages &
cuneiform cartilages
• The paired corniculate cartilages (shaped
like a small horn), horn-shaped pieces of
elastic cartilage, are located at the apex of
each arytenoid cartilage.
• The paired cuneiform cartilages, wedge-
shaped elastic cartilages anterior to the
corniculate cartilages, support the vocal
folds and lateral aspects of the epiglottis.

26. The Structures of Voice Production
• The mucous membrane of the larynx forms 2 pairs of folds:
1. A superior pair called the ventricular folds (false vocal cords)
2. An inferior pair called the vocal folds (true vocal cords).
• The space between the ventricular folds is known as the rima vestibuli.
• The laryngeal sinus (ventricle)
is a lateral expansion of the
middle portion of the laryngeal
cavity inferior to the ventricular
folds and superior to the vocal
folds.

27. When the ventricular folds
are brought together, they
function in holding the
breath against pressure in
the thoracic cavity

28. Trachea
• The trachea or windpipe, is a tubular passageway for air that is about 12
cm (5 in.) long and 2.5 cm (1 in.) in diameter. It is located anterior to the
esophagus and extends from the larynx to the superior border of the fifth
thoracic vertebra (T5), where it divides into right and left primary bronchi.
• The layers of the tracheal wall, from deep to superficial,are the
1. mucosa
2. submucosa
3. hyaline cartilage
4. adventitia (composed of areolar connective tissue).

29. • The 16–20 incomplete, horizontal rings of hyaline cartilage resemble the
letter C, are stacked one above another, and are connected together by
dense connective tissue.
• The open part of each C-shaped cartilage ring faces posteriorly toward the
esophagus and is spanned by a fibromuscular membrane. Within this
membrane are transverse smooth muscle fibers, called the trachealis
muscle, and elastic connective tissue that allow the diameter of the
trachea to change.
• The solid C-shaped cartilage rings provide a semirigid support so that the
tracheal wall does not collapse inward.

30. • Carina-The last tracheal ring is thick and broad. From
its lower border, a hook-like process curves downwards
and backwards between the bronchi.
• This projection is called carina(meaning -keel)
• It is in between the orifices of the main bronchi in the
sagittal plane. The mucous membrane at the carina is
one of the most sensitive areas of the tracheobronchial
tree. It is associated with cough reflex.

31. Cross section

32. Relations of Trachea
The Cervical Part
✓ Anteriorly
• Isthmus of the thyroid lies on
the 2nd, 3rd and 4th tracheal
rings
• Pretracheal layer of fascia
• Vessels of thyroid gland
• The strap muscles-sternohyoid
and sternothyroid.
✓ Posteriorly
• The esophagus
• The recurrent laryngeal nerves
lie in a groove between the
trachea and the esophagus
✓ Laterally
• The lobes of the thyroid
• The common carotid arteries
in the carotid sheath.

33. Relations of Thoracic Part
✓Posteriorly -esophagus.
✓ Anteriorly
• Manubrium sterni
• The arch of aorta
• The brachiocephalic and left
common carotid arteries
• The thymus
• The left brachiocephalic vein
crosses to the right side.
✓Left side
• Arch of aorta
• Left subclavian and left
common carotid arteries
• Left recurrent laryngeal nerve
✓ Right side
• Arch of azygos vein
• Right vagus nerve.

34. APPLIED ANATOMY
• Foreign bodies entering the trachea have a tendency to go to the
right bronchus, since it is wider and more in line with the trachea.
• Tracheostomy-is an emergency surgery, usually done to relieve
complete obstruction of the respiratory tract at laryngeal level. An
opening is made in the trachea, just below the isthmus of the
thyroid and a tracheostomy tube is inserted, so that air enters into
the distal part of respiratory tract through it.

35. The Bronchi
• At the superior border of the fifth thoracic vertebra, the trachea
divides into a right primary bronchus which goes into the right lung,
and a left primary bronchus, which goes into the left lung
• Like the trachea, the primary bronchi contain incomplete rings of
cartilage and are lined by pseudostratified ciliated columnar
epithelium.
• The left principal bronchus is longer (5 cm), narrower and more
oblique than the right.This bronchus, enters the hilum of the left
lung and divides into 2 lobar bronchi-upper and lower.

36. The right primary bronchus
• The right primary bronchus is more vertical, shorter,
and wider than the left.
• The right bronchus enters the hilum of the lung and
divides into 3 lobar bronchi-superior, middle and
inferior.
• The bronchus to the upper lobe lies above the
pulmonary artery-eparterial bronchus. The other 2,
below the pulmonary artery-hyparterial bronchus.

37. The Bronchial Tree
• On entering the lungs, the primary bronchi divide to form smaller
bronchi—the secondary (lobar) bronchi, one for each lobe of the
lung.
• The secondary bronchi continue to branch, forming still smaller
bronchi, called tertiary (segmental) bronchi, that divide into
bronchioles. Bronchioles in turn branch repeatedly, and the smallest
ones branch into even smaller tubes called terminal bronchioles.
• This extensive branching from the trachea resembles an inverted
tree and is commonly referred to as the bronchial tree.

38. Tracheo-bronchial Tree

39. Structural changes
• Plates of cartilage gradually replace the incomplete
rings of cartilage in primary bronchi and finally
disappear in the distal bronchioles.
• As the amount of cartilage decreases, the amount of
smooth muscle increases. Smooth muscle encircles the
lumen in spiral bands. Because there is no supporting
cartilage, however, muscle spasms can close off the
airways. This is what happens during an asthma attack.

40. The Lungs
• The lungs are paired cone-shaped
organs in the thoracic cavity. They
are separated from each other by
the heart and other structures in
the mediastinum.
• Separate pleural cavities
surround the left and right lungs.

41. The Pleura
• Each lung is enclosed and protected by a double-layered
serous membrane called the pleural membrane.
1. The superficial layer, called the parietal pleura, lines the
wall of the thoracic cavity;
2. the deep layer, the visceral or pulmonary pleura, covers
the lungs themselves.
✓ Between the visceral and parietal pleurae is a small space,
the pleural cavity, which contains a small amount of
lubricating fluid secreted by the membranes.

42. The Parietal Pleura
4 subdivisions

43. Applied Anatomy
• Inflammation of the pleural membrane, called pleurisy
or pleuritis
• excess fluid accumulates in the pleural space, a
condition known as pleural effusion.
• Collapse of a part of a lung, or rarely an entire lung, is
called atelectasis.
• In certain conditions, the pleural cavities may fill with
air (pneumothorax), blood (hemothorax), or
pus(pyothorax).

44. The Lungs
• The lungs extend from the diaphragm to just slightly
superior to the clavicles and lie against the ribs anteriorly
and posteriorly .
• The broad inferior portion of the lung, the base, is concave
and fits over the convex area of the diaphragm.
• The narrow and rounded superior portion of the lung is the
apex. It extend into the root of the neck, about 3 cm
superior to the anterior end of the first rib and medial end
of the clavicle.

46. The Surface Of The Lung
• The surface of the lung lying against the ribs, the costal
surface, matches the rounded curvature of the ribs.
• The mediastinal (medial) surface of each lung contains a
region, the hilum, through which bronchi, pulmonary blood
vessels, lymphatic vessels, and nerves enter and exit.

47. Left Vs Right Lungs
• Medially, the left lung also contains a concavity, the
cardiac notch, in which the heart lies. Due to the space
occupied by the heart, the left lung is about 10%
smaller than the right lung.
• Although the right lung is thicker and broader, it is also
somewhat shorter than the left lung because the
diaphragm is higher on the right side, accommodating
the liver that lies inferior to it.

49. Lingula

51. The Bronchopulmonary Segment
• Each segmental bronchus and the accompanying division of
the pulmonary artery supply a definite part of the lung and
the entire unit is referred to as the bronchopulmonary
segment.
• The radicals of pulmonary veins are not segmental; they are
intersegmental in position.
• The bronchopulmonary segments are independent units.
• Each unit is surrounded by connective tissue, which is
continuous with the visceral pleura.

53. • Each bronchopulmonary
segment of the lungs has
many small compartments
called lobules; each lobule is
wrapped in elastic connective
tissue and contains a
lymphatic vessel, an arteriole,
a venule, and a branch from a
terminal bronchiole.

54. • Terminal bronchioles subdivide
into microscopic branches
called respiratory bronchioles.
• Respiratory bronchioles in turn
subdivide into several (2–11)
alveolar ducts.
• Around the circumference of
the alveolar ducts are
numerous alveoli and alveolar
sacs.

55. Alveoli
• An alveolus is a cup shaped out
pouching lined by simple squamous
epithelium and supported by a thin
elastic basement membrane.
• An alveolar sac consists of two or
more alveoli that share a common
opening.
• The walls of alveoli consist of type I
& type II alveolar epithelial cells.

56. Alveolar Cells…
• The more numerous type I alveolar cells are simple squamous
epithelial cells that form a nearly continuous lining of the alveolar
wall. The thin type I alveolar cells are the main sites of gas exchange.
• Type II alveolar cells, also called septal cells, are fewer in number and
are found between type I alveolar cells. Type II alveolar cells, rounded
or cuboidal epithelial cells with free surfaces containing microvilli,
secrete alveolar fluid, surfactant.
• Associated with the alveolar wall are alveolar macrophages (dust cells)
that remove fine dust particles and other debris from the alveolar
spaces.

57. The Respiratory Membrane
• The exchange of O2 and CO2 between the air spaces in the lungs and the
blood takes place by diffusion across the alveolar and capillary walls,
which together form the respiratory membrane.
• It has 4 layers:
1. A layer of type I and type II alveolar cells and associated alveolar
macrophages that constitutes the alveolar wall
2. An epithelial basement membrane underlying the alveolar wall
3. A capillary basement membrane that is often fused to the epithelial
basement membrane
4. The capillary endothelium

60. Blood Supply of Lungs
• The Pulmonary Artery - One pulmonary artery enters the hilum of
the lung carrying deoxygenated blood from the right ventricle of
the heart; it ends in the capillary plexus on the alveolar walls of the
lung.
• The Pulmonary Veins - Two veins emerge from the hilum of each
lung. They carry oxygenated blood from the lung and empty into
the left atrium.
• The Bronchial Artery - This artery may arise from the thoracic aorta
or one of the posterior intercostal arteries. It supplies the bronchial
tree (as far as the respiratory bronchioles).

61. Nerve Supply of Lungs
• The lungs and the visceral pleura are innervated by
thepulmonary plexuses, which are formed by the
branches of vagus nerves (parasympathetic) and
sympathetic trunks.
Lymphatic Drainage of Lungs
• There are 2 sets of lymphatics-superficial and deep plexuses-
both of which ultimately drain into thebronchopulmonary
nodes.

62. Muscles of respiration
• The expansion of the chest during inspiration occurs
as a result of muscular activity, partly voluntary and
partly involuntary.
• The main muscles of respiration in normal quiet
breathing are the intercostal muscles and the
diaphragm.
• During difficult or deep breathing they are assisted
by the muscles of the neck, shoulders and abdomen.

63. Intercostal muscles
• There are 11 pairs of intercostal muscles that occupy the spaces
between the 12 pairs of ribs.
• They are arranged in two layers, the external and internal
intercostal muscles
• The external intercostal muscle fibres. These extend in a downwards
and forwards direction from the lower border of the rib above to the
upper border of the rib below.
• The internal intercostal muscle fibres. These extend in a downwards
and backwards direction from the lower border of the rib above to
the upper border of the rib below, crossing the external intercostal
muscle fibres at right angles.

64. • The innermost intercostal muscle is a layer of intercostal
muscles. It may also be called the intima of the internal
intercostal muscles. It is the deepest muscular layer of
the thorax, with muscle fibres running parallel with
the internal intercostal muscles.
• It is present only in the middle of each intercostal space, and
often not present higher up the rib cage.
• It lies deep to the plane that contains the intercostal
nerves and intercostal vessels, and the internal intercostal
muscles.
• The diaphragm is continuous with the innermost intercostal
muscle.

66. • The first rib is fixed. Therefore, when
the intercostal muscles contract they
pull all the other ribs towards the first
rib.
• Because of the shape of the ribs they
move outwards when pulled upwards.
In this way the thoracic cavity is
enlarged antero-posteriorly and
laterally. (bucket handle movement)

67. Diaphragm
• The diaphragm is a dome-shaped
structure separating the thoracic and
abdominal cavities.
• It forms the floor of the thoracic cavity
and the roof of the abdominal cavity and
consists of a central tendon from which
muscle fibres radiate to be attached to the
lower ribs and sternum and to the
vertebral column by two crura.
• The diaphragm is supplied by the phrenic
nerves.

68. • When the muscle of the diaphragm is relaxed, the central tendon is
at the level of the 8th thoracic vertebra.
• When it contracts, its muscle fibres shorten and the central tendon
is pulled downwards to the level of the 9th thoracic vertebra,
enlarging the thoracic cavity in length.
• This decreases pressure in the thoracic cavity and increases it in the
abdominal and pelvic cavities.
• The intercostal muscles and the diaphragm contract simultaneously
ensuring the enlargement of the thoracic cavity in all directions,
that is from back to front, side to side and top to bottom.