1. TRACHEOBRONCHIAL TREE PULMONARY VENTILATION
ANATOMY OF
TRACHEOBRONCHIAL TREE
AND
PULMONARY VENTILATION
Presented by
Dr. Sunil Kumar Arora

2. Organs of the Respiratory System
A. The organs of the respiratory tract can be divided into two groups:
1.Upper Airways
2.Lower airways

3. Upper Airways
Nose
Paranasal sinuses
Pharynx

4. Lower Airway Begins with true vocal cords and extends to alveoli
Larynx
Trachea
Main stem bronchi
Segmental bronchi
Subsegmental bronchi
Bronchioles
Terminal bronchioles
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
alveoli

6. Organization and Functions of the Respiratory System
Conducting portion transports air.
- includes the nose, nasal cavity, pharynx, larynx, trachea, and progressively smaller airways, from the primary bronchi to the terminal bronchioles
Respiratory portion carries out gas exchange.
- composed of small airways called respiratory bronchioles and alveolar ducts as well as air sacs called alveoli

7. Tracheobronchial Tree
A highly branched system of air-conducting passages that originate from the trachea and progressively branch into narrower tubes as they diverge throughout the lungs before terminating in terminal bronchioles.
Series branching airways commonly referred to as “generations” or of “orders”
The first generation or order is zero (0), the trachea itself

8. Trachea
A flexible tube of cm length and cm width also called windpipe. Extends to second rib anteriorly and T4-T5 posteriorly.
Extends through the mediastinum and lies anterior to the esophagus and inferior to the larynx.
Anterior and lateral walls of the trachea supported by 15 to 20 C-shaped tracheal cartilages.
Cartilage rings reinforce and provide rigidity to the tracheal wall to ensure that the trachea remains open at all times
Posterior part of tube lined by trachealis muscle.

9. Tracheal lining
Pseudostratified columnar epithelium with cilia; goblet cells, serous cells, and specialized submucosal bronchial glands
200+ cilia per cell, 5-7 microns long
Beat cephalid (head) toward oropharynx

10. Primary bronchus
At the level of the sternal angle, the trachea bifurcates into two smaller tubes, called the right and left primary bronchi.
Each primary bronchus projects laterally toward each lung.
The most inferior tracheal cartilage separates the primary bronchi at their origin and forms an internal ridge called the carina.

11. Main Stem Bronchi Right bronchus Left bronchus Wider More vertical
5 cm shorter
Supported by C shaped cartilages
20-30 degree angle
First generation
Left bronchus
Narrower
More angular
Longer
Supported by C shaped cartilages
40-60 degree angle
First generation
Foreign particles are more likely to lodge in the right primary bronchus.
Foreign particles are more likely to lodge in the right primary bronchus.

12. Bronchial tree
The primary bronchi enter the hilus of each lung together with the pulmonary vessels, lymphatic vessels, and nerves.
Each primary bronchus branches into several secondary bronchi (or lobar bronchi).
The left lung has two secondary bronchi.The right lung has three secondary bronchi.
They further divide into tertiary bronchi.
Each tertiary bronchus is called a segmental bronchus because it supplies a part of the lung called a bronchopulmonary segment.

13. Lobar Bronchi R main stem divides into: L main stem divides into:
Upper lobar bronchus
Middle lobar bronchus
Lower lobar bronchus
L main stem divides into:
Upper lobar bronchus
Lower lobar bronchus

14. Segmental Bronchi 3rd generation
R lobar divides into
Segmental bronchi
10 segments on right
L lobar divides into
Segmental bronchi
8 segments on left

15. Subsegmental Bronchi 4th to 9th generations
Progressively smaller airways
1-4 mm diameter
At 1 mm diameter connective tissue sheath disappears

16. Noncartilagenous Airways
Bronchioles
10-th to 15th generation
Cartilage is absent
Lamina propria is directly connected with lung parenchyma
Surrounded by spiral muscle fibers
Epithelial cells are cuboidal
Less goblet cells and cilia
With no cartilage, airway remains open due to pressure gradients

17. Terminal Bronchioles 16th to 19th generation
Average diameter is 0.5 mm
Cilia and mucous glands begin to disappear totally
End of the conducting airway
Canals of Lambert-interconnect this generation,provide collateral ventilation

18. Respiratory Bronchioles, Alveolar Ducts, and Alveoli
Lungs contain small saccular outpocketings called alveoli.
They have a thin wall specialized to promote diffusion of gases between the alveolus and the blood in the pulmonary capillaries.
Gas exchange can take place in the respiratory bronchioles and alveolar ducts as well as in the alveoli, each lung contains approximately 300 to 400 million alveoli.
The spongy nature of the lung is due to the packing of millions of alveoli together.

19. Segmental anatomy

21. Gas exchange zone Respiratory bronchioles Acinus
Alveolar Ducts, sacs, alveoli

22. Functional Units of Gas Exchange
Three generations of respiratory bronchioles
Three generations of alveolar ducts
15-20 clusters--sacs

23. Acinus or Lobule
Each acinus (unit) is approximately 3.5 mm in diameter
Each contains about 2000 aveloli
There are approximately 130,000 primary lobules in the lung

24. Anatomic Arrangement of Alveoli
85-95% of alveoli covered by small pulmonary capillaires
The cross-sectional area or surface area is approximately 70m2
Total of about 300 million alveoli in
2 lungs

25. Cells in Alveolus Type I cells : 95% of Alveoler surface,
Major site of gas exchange
 Type II cells : or Septal cells secrete surfactant,About 5% of Alveoler surface.
 Alveolar macrophages-Plays role in defence mechenism.

27. Surfactant
Is a substance produce by type II alveolar epithelial cells (~ 5% of the surface area of the alveoli) which reduce the surface tension of the fluid in the inner surface of the alveoli
it is a mixture of phospholipids, proteins, and ions, the most important component is phospholipid dipalmitoyl phosphatidylcholine which is responsible for reducing the surface tension.

28. Respiratory Zone of Lower Respiratory Tract

29. Respiratory Membrane squamous cells of alveoli .
Diffusion of gases occurs through Respiratory mambrane.
squamous cells of alveoli .
basement membrane of alveoli.
basement membrane of capillaries
simple squamous cells of capillaries
about .5 μ in thickness

30. Anatomy of the Respiratory Membrane

31. Epithelial basement membrane Capillary basement membrane
Interstitial space
Capillary endothelium
Alveolar epithelium
Red blood cell
Fluid and surfactant layer
Alveolus
Capillary
Diffusion O2
Diffusion
CO2

32. Intersitium/interstial space
Surround, supports, and shapes the alveoli and capillaries
Composed of a gel like substance and collagen fibers
Contains tight space and loose space areas

33. Factors that affect the rate of gas diffusion through the respiratory membrane
The thickness of the respiratory membrane.The thickness of the respiratory membrane is inversely proportional to the rate of diffusion through the membrane.
Surface area of the membrane.

34. The diffusion rate of the specific gas
The diffusion rate of the specific gas. Diffusion coefficient for the transfer of each gas through the respiratory membrane depends on its solubility in the membrane and inversely on the square root of its molecular weight. CO2 diffuses 20 times as rapidly as O2.
The pressure difference between the two sides of the membrane (between the alveoli and in the blood).

35. Pores of Kohn
Small holes in the walls of adjoining alveoli (alveaolar septa)
Between 3 to 13 µ in diameter
Formation of pores may be due to:
Desquamation due to disease
Normal degeneration due to aging
Movement of macrophages leaving holes

36. Blood supply of Lungs
Bronchial circulation – bronchial arteries supply oxygenated blood to lungs, bronchial veins carry away deoxygenated blood from lung tissue.
Pulmonary circulation
Response of two systems to hypoxia –
pulmonary vessels undergo vasoconstriction,
bronchial vessels like all other systemic vessels undergo vasodilation

37. Bronchial Blood Supply
Bronchial arteries
Arise from thoracic aorta(Anatomic variation is there),usually there are 1 artery for Rt lung and 2 arteries for Lt Lung.
Bronchial arteries run along with the branching bronchi and supply lung tissue except the alveoli.
Much of the blood supplied by Bronchial arteries is Returned via Pulmonary veins rather than bronchial veins.

38. Bronchial arteries Also nourish Mediastinal lymph nodes
Pulmonary nerves
Some muscular pulmonary arteries and veins
Portions of the esophagus
Visceral pleura

39. Bronchial venous system
Approx.1/3 blood returns to right heart
Azygous vien
Hemiazygous vein
Intercostal veins
This blood comes form the first two or three generations of bronchi

40. Bronchial venous return
2/3 of blood flowing to terminal bronchioles drains into pulmonary circulation via “bronchopulmonary anastomoses”
Then flows to left atrium via pulmonary veins
Contributes to “venous admixture” or “anatomic shunt” (1-2% of C.O.)

41. Pulmonary Vascular System
The second source of blood to the lungs
Primary purpose is to deliver blood to lungs for gas exchange
Also delivers nutrients to cells distal to terminal bronchioles
Composed of arteries, arterioles, capllaries, venules, and veins

42. Pulmonary Trunk arises from the infundibulum of Rt ventricle and divide into Rt and Lt branches.Which carry deoxygenated blood.
Pulmonary arteries branch profusely along with the bronchi leading to capillary network sorrunding the alveoli.
4 Pulmonary veins(2 from each Lung) form post alveoli to carry oxygenated blood to the Lt Atrium

43. Pulmonary Capillaries
Walls are less than 0.1µ thick
Total external thickness is about 10µ
Selective permeability to water, electrolytes, sugars
Produce and destroy biologically active substances

44. Nerve Supply
Lung and Pleura are innervated by Anterior and posterior pulmonary plexuses
They are mixed plexuses containing vagal(Parasympethatic) and sympathetic fibers.
Vagus Nerve(Parasympathetic)—Bronchoconstriction,vasodilatation and Secretomotor
Sympathetic Fibres—Bronchodilator,vasocostrictor and inhibitor to the glands of bronchial tree.

45. Lymphatic System
Lymphatic vessels remove fluids and protein molecules that leak out of the pulmonary capillaries
Transfer fluids back into the circulatory system

46. Lymphatic Drainage of Lungs
There are 2 sets of Lymphatics,both of which drain into the Bronchopulmonary nodes.
Superficial vessels drain the peripheral lung tissue lying beneth the pulmonary pleura
Deep lymphatics drain the bronchial tree,the pulmonary vessels and connective tissue septa and then run towards the hilum.

47. Lymphatic vessels of upper lobe end up in superior tracheobronchial node and from lower lobe enters the inferior tracheobronchial nodes.
The tracheobronchial and bronchopulmonary nodes end in the bronchomediastinal lymph trunk
This trunk reaches the thoracic duct on the left and Rt lymphatic duct on the Rt side.

48. Respiratory events
Pulmonary ventilation = exchange of gases between lungs and atmosphere
External respiration = exchange of gases between alveoli and pulmonary capillaries
Internal respiration = exchange of gases between systemic capillaries and tissue cells

49. Breathing
Breathing (pulmonary ventilation). consists of two cyclic phases:
inhalation, also called inspiration - draws gases into the lungs.
exhalation, also called expiration - forces gases out of the lungs.

50. Muscles of Inspiration
During inspiration, the dome shaped diaphragm flattens as it contracts
This increases the height of the thoracic cavity
The external intercostal muscles contract to raise the ribs
This increases the
circumference of the thoracic cavity
Together:

51. Inspiration continued
Intercostals keep the thorax stiff so sides don’t collapse in with change of diaphragm
During deep or forced inspiration, additional muscles are recruited:
Scalenes
Sternocleidomastoid
Pectoralis minor
Quadratus lumborum on 12th rib
Erector spinae
(some of these “accessory muscles” of ventilation are visible to an observer; it usually tells you that there is respiratory distress – working hard to breathe)

52. Expiration Quiet expiration in healthy people is chiefly passive
Inspiratory muscles relax
Rib cage drops under force of gravity
Relaxing diaphragm moves superiorly (up)
Elastic fibers in lung recoil
Volumes of thorax and lungs decrease simultaneously, increasing the pressure
Air is forced out

53. Expiration continued Forced expiration is active
Contraction of abdominal wall muscles
Oblique and transversus predominantly
Increases intra-abdominal pressure forcing the diaphragm superiorly
Depressing the rib cage, decreases thoracic volume
Some help from internal intercostals and latissimus dorsi
(try this on yourself to feel the different muscles acting)

54. Expiration Inspiration Increased vertical diameter
Increased A-P diameter
Elevated rib cage
External intercostals contracted
Internal intercostals relaxed
Diaphragmatic contraction
Abdominals contracted

55. Muscles Of Breathing

56. Boyle’s Law
The pressure of a gas decreases if the volume of the container increases, and vice versa.
When the volume of the thoracic cavity increases even slightly during inhalation, the intrapulmonary pressure decreases slightly, and air flows into the lungs through the conducting airways. Air flows into the lungs from a region of higher pressure (the atmosphere)into a region of lower pressure (the intrapulmonary region).
When the volume of the thoracic cavity decreases during exhalation, the intrapulmonary pressure increases and forces air out of the lungs into the atmosphere.

57. Alveolar pressure
Alveolar pressure: – is the pressure inside the lung alveoli
During inspiration:  –1cm of H2O (this slight negative pressure is enough to move about 0.5 liter of air into the lungs in the first 2 second of inspiration)
During expiration: it rises to about +1cm of H2O (this forces 0.5 liter of inspired air out of the lungs during the 2 to 3 seconds of expiration

58. Compliance of the lungs
Definition:
the extent to which the lungs expand for each unit increase in transpulmonary pressure (difference between intra-alveolar pressure and intra-pleural pressure) ~ 200ml/cm of H2O (each time, the transpulmonary pressure increase by 1cm of H2O, the lungs expand 200ml)

59. Mechanism

60. Respiratory Values
A normal adult averages 12 breathes per minute = respiratory rate(RR)
Respiratory volumes – determined by using a spirometer

61. LUNG VOLUMES
TIDAL VOLUME (TV): Volume inspired or expired with each normalﾊbreath. = 500 ml
INSPIRATORY RESERVE VOLUME (IRV): Maximum volume that can be inspired over the inspiration of a tidal volume/normal breath. Used during exercise/exertion.=3100 ml
EXPIRATRY RESERVE VOLUME (ERV): Maximal volume that can be expired after the expiration of a tidal volume/normal breath. = 1200 ml
RESIDUAL VOLUME (RV): Volume that remains in the lungs after a maximal expiration.ﾊ CANNOT be measured by spirometry.= 1200 ml
RESPIRATORY MINUTE VOLUME : Amount of air inspired per minute. e.g. 500ml x 12 = 6 Ltr.
Dead Space : Portion of each Tidal volume that does not take part in gas exchange (150ml).

62. LUNG CAPACITIES
INSPIRATORY CAPACITY ( IC): Volume of maximal inspiration:IRV + TV = 3600 ml
FUNCTIONAL RESIDUAL CAPACITY (FRC): Volume of gas remaining in lung after normal expiration, cannot be measured by spirometry because it includes residual volume:ERV + RV = 2400 ml
VITAL CAPACITY (VC): Volume of maximal inspiration and expiration:IRV + TV + ERV = IC + ERV = 4800 ml
TOTAL LUNG CAPACITY (TLC): The volume of the lung after maximal inspiration.ﾊ The sum of all four lung volumes, cannot be measured by spirometry because it includes residual volume:IRV+ TV + ERV + RV = IC + FRC = 6000 ml

64. Partial pressures of respiratory gases as they enter and leave the lungs (at sea level)
CO2
H2O
Atmospheric Air*
(mmHg)
Humidified Air
Alveolar Air
Expired Air
(78.62%)
(74.09%)
(74.9%)
(74.5%)
(20.84%)
(19.67%)
(13.6%)
(15.7%)
0.3 (0.04%)
40.0 (5.3%)
27.0 (3.6%)
3.7 (0.50%)
47.0 (6.20%)
47.0 (6.2%)

65. The rate at which alveolar air is renewed by atmospheric air:
The amount of air remaining in the lungs at the end of normal expiration ~ 2300ml (FRC). Only 350ml of air is brought into the alveoli with each breath. Therefore, the amount of alveolar air is replaced by new atmospheric air with each breath is only 1/7th of the total. This slow replacement of alveolar air is important in preventing sudden changes in gaseous concentrations in the blood.

66. Ventilation-perfusion ratio (V/Q)
It is the ratio of alveolar ventilation to pulmonary blood flow per minute. The alveolar ventilation at rest (4.2L/min) and is calculated as:
Alveolar ventilation = respiratory rate x (tidal volume – dead space air).
The pulmonary blood flow is equal to right ventricular output per minute (5L/min).
This value is an average value across the lung.
At the apex, V/Q ratio = 3.
At the base, V/Q ratio = 0.6.
So the apex is more ventilated than perfused, and the base is more perfused than ventilated.
During exercise, the V/Q ratio becomes more homogenous among different parts of the lung.

67. THANK YOU