Anatomy and physiology

1. Respiratory System
Unit-I
Anatomy and Physiology-II

2. Objectives
 Define respiratory system.
 Define respiration.
 Describe the structure and the function of:
• upper respiratory tract (Nose, Pharynx, Larynx)
• lower respiratory tract (Trachea, Bronchial tree, lungs)
 Discuss the physiology of respiration by explaining the
mechanism of:
• Pulmonary Ventilation
• External Respiration
• Internal Respiration
 Discuss nervous control of respiration
 Briefly discuss the lung volumes & capacities

3. Respiratory System
• Definition: A system consisting of lungs and air
passages specialized for the intake of oxygen and
exchange of gases with the blood.
• Respiration: The exchange of oxygen and carbon
dioxide between the atmosphere and the cells of
the body.
Respiration includes three things:
1) Ventilation of lungs (inspiration and expiration),
2) External respiration (the exchange of gases
between lungs and blood) and Internal respiration
(between blood and tissues), and
3) The use of oxygen in cellular metabolism.

4. Functions
Respiratory and Non-Respiratory
Functions
 Respiratory Functions are:
1. Pulmonary ventilation
2. Diffusion of O2 and CO2 b/w alveoli and blood
3. Transport of O2 and CO2 to and from tissues
4. Regulation of O2 and CO2 in blood and tissues

5. Functions cont....
 Non Respiratory Functions are:
• Air filtration
• Protective/Cleansing Reflexes (SSC reflexes)
• Olfaction
• Vocalization
• Defence mechanism..... Includes leukocytes, NK cells,
macrophages, dendrite cells, mast cells, defensins and
cathelicidins.
• Maintenance of water
• Regulation of body temperature
• Regulation of PH
• Secretion of ACE

6. Angiotensin-converting enzyme (EC 3.4. 15.1),
or ACE, is a central component of the renin–
angiotensin system (RAS), which controls blood
pressure by regulating the volume of fluids in
the body. ... Therefore, ACE indirectly increases
blood pressure by causing blood vessels to
constrict.

7. Respiratory Division
Respiratory tract is divided into two:
• Upper Respiratory Tract (URT):
consists of nose, pharynx, and larynx.
• Lower Respiratory Tract (LRT):
consists of Trachea, Bronchi, bronchioles and
lungs.

8. 8

9. Upper Respiratory Tract
 Nose:
Apart from olfaction the nose has several functions:
it warms, cleanses, and humidifies the inhaled air.
It serves as a resonating chamber that amplifies the voice.
• nasal cavity
• nasal septum
• mucous membrane
– mucus
– hair
– olfactory receptors

10. Pharynx:
Is a muscular tube extending about 13 cm (5
inch). It is divided into three regions:
 Nasopharynx
-- Lies dorsal to the soft palate.
-- Receives the eustachian (auditory) tubes.
-- Houses pharyngeal tonsils.

11.  Oropharynx
-- The space between the soft palate and root of the
tongue which extends inferiorly to the hyoid bone.
Means it extends from the Uvula to the level of the
hyoid bone.
-- It contains palatine and lingual tonsils.
 Laryngopharynx
It extends from the hyoid bone to the cricoid
cartilage.
Oropharynx and Laryngopharynx serve as a common
passageway for both food and air.

13. Larynx
• The larynx or voice box is a cartilaginous chamber about 4
cm long.
• Its primary function is to keep food and drink out of the
airway, but it also produces sound.
• The superior opening of the larynx, the glottis (at the base
of the tongue) is guarded by a flap of tissue called the
epiglottis.
• During swallowing, extrinsic muscles of the larynx pull the
larynx upward toward the epiglottis, the tongue pushes
the epiglottis downward, and the epiglottis directs food
and drink into the esophagus dorsal to the airway.
• The vestibular folds of the larynx also keeps food and
drink out of the airway even if epiglottis is removed.

15. Larynx
• There are nine cartilages, three unpaired and three
paired. The unpaired cartilages of the larynx are
thyroid, cricoid and epiglottis.
• The paired cartilages of the larynx are
the arytenoids, corniculates, and the cuneiforms.
• Thyroid Cartilage: This forms the Adam's
apple. It is usually larger in males than in females.
The thyrohyoid membrane is a ligament associated
with the thyroid cartilage that connects the thyroid
cartilage with the hyoid bone.

16. Cricoid cartilage: A ring of hyaline
cartilage that forms the inferior wall of the
larynx. It is attached to the top of trachea.
Epiglottis: A large, spoon-shaped piece of
elastic cartilage. During swallowing, the
pharynx and larynx rise. Elevation of the
pharynx widens it to receive food and drink;
elevation of the larynx causes the epiglottis
to move down and form a lid over the glottis,
closing it off.

17. Larynx cont….
• Paired Arytenoid Cartilage: They are
smaller, the arytenoid cartilages are the most
important because they influence the position and
tension of the vocal folds. These are triangular
pieces of hyaline cartilage located at the
posterosuperior border of the cricoid cartilage.
• Paired Corniculate Cartilage: Horn-
shaped pieces of elastic cartilage located at the
apex of each arytenoid cartilage.
• Paired Cuneiform Cartilage: Club-shaped
pieces of elastic cartilage located anteriorly to the
corniculate cartilages.

18. • The first three are relatively large and unpaired.
The superior one, the epiglottic cartilage, is
a spoon shaped supportive plate in the epiglottis.
The largest, the thyroid cartilage. It has an
anterior peak, the laryngeal prominence,
commonly called Adam’s apple, which is larger in
males due to testosterone. Inferior to the thyroid
cartilage is ring like cricoid cartilage which
connects larynx to the trachea.
• The remaining cartilages are smaller and occur in
three pairs. Posterior to the thyroid cartilage are
paired arytenoid, paired corniculate, and
paired cuneiform cartilages.

20. Lower Respiratory Tract
 Trachea
The trachea or windpipe is a rigid tube 12 cm long
and 2.5 cm wide lying anterior to the esophagus.
It is supported by about 20 C-shaped rings of
hyaline cartilage, some of which we can palpate
between larynx and sternum.
The open part of the C faces posteriorly which
allows room for the esophagus to expand when
the swallowed food passes by.
The cartilages are spanned by trachealis muscles.

21. Bronchi and Bronchial Tree
At the level of fifth thoracic vertebra, the trachea
divides into a right primary bronchus and
left primary bronchus.
The right primary bronchus is more vertical, shorter,
and wider than the left.
As a result, an aspirated object is more likely to enter
and lodge in the right primary bronchus than the
left.
Like the trachea, the primary bronchi contain
incomplete rings of cartilage and are lined by
ciliated pseudostratified columnar epithelium.

22. • The point where the trachea divides into right
and left primary bronchi is called carina. The
mucous membrane of the carina is one of the
most sensitive areas of the larynx and trachea for
triggering a cough reflex.
• On entering the lungs, the primary bronchi divide
to form smaller bronchi called secondary
bronchi. Each lobe in the lungs receive one
secondary (lobar) bronchus.
• The secondary bronchi continue to branch,
forming still smaller bronchi, called tertiary
(segmental) bronchi.

23. Cont…
• These bronchi further divide into bronchioles
(1 mm or less in diameter).
• The portion of the lung ventilated by one
bronchiole is called a pulmonary lobule.
• The bronchioles further divide to form
terminal bronchioles. This extensive
branching from the trachea resembles an
inverted tree and is commonly referred to as
the bronchial tree.

24. Branches of Bronchial Tree
Trachea
↓
Primary bronchi
↓
Secondary bronchi
↓
Tertiary bronchi
↓
Bronchioles
↓
Terminal bronchioles
↓
Respiratory bronchiole

26. • The larynx, trachea, and bronchial tree are lined
mostly by ciliated pseudostratified columnar
epithelium, which functions as a mucociliary
escalator. That is, the mucous traps the inhaled
particles and then the ciliary beating drives the
mucus up to the pharynx where it is either
swallowed or spit out.
Respiratory unit includes:
• 1. Respiratory bronchioles
• 2. Alveolar ducts
• 3. Alveolar sacs
• 4. Antrum
• 5. Alveoli

27. Lungs
• Each lung is a somewhat conical shaped organ
with a broad concave base resting on the
diaphragm and a blunt peak called apex faces
upward to clavicles.
The broad costal surface is pressed against the rib
cage, and the smaller concave mediastinal
surface faces medially. The lung receives the
bronchus, blood vessels, and nerves through its
hilum, a slit in a mediastinal surface.
The left lung is a little smaller than the right
because of the heart tilting to the left giving
indentation to the lung called cardiac impression
or Cardiac notch.

28. The left lung has two lobes as superior and inferior
lobe with a deep fissure between them called
oblique fissure.
The right lung has three lobes as superior, middle,
and inferior lobe. Superior lobe is separated from
the middle lobe by horizontal fissure and the
inferior lobe from the middle one by oblique
fissure.

29. Alveoli
• An alveolus (plural alveoli) is pouch about 0.2 to 0.5 mm in
diameter.
• It is lined by simple squamous epithelium.
• An alveolar sac consists of two or more alveoli that share a
common opening.
• The surface area of the alveoli is about 70 m2.The walls of
alveoli consist of two types of alveolar epithelial cells.
• Type I alveolar cells which are numerous and form a
continuous layer. They are simple squamous epithelial cells.
Gaseous exchange occurs here.
• Type II alveolar cells also called septal cells, rounded or
cuboidal, which are fewer in number and found between
type I cells.

30. Alveoli cont….
• They secrete alveolar fluid to keep the surface
moist.
• Included the alveolar fluid is surfactant, a
mixture of phospholipids and lipoproteins.
• Surfactant lowers the surface tension of the
alveolar fluid, which reduces the tendency of the
alveoli to collapse.
• Associated with the alveolar wall are alveolar
macrophages (dust cells). They are phagocytes
which remove fine dust particles and other debris
and pathogens from the alveolar surface.
• Alveoli are surrounded by a network of blood
capillaries for gaseous exchange.

31. 31

32. Capillary
Red Blood Cell
Oxygen is picked up
Carbon Dioxide
is dropped off
Wall of
the air
sac

33. Plural Membrane
• The lungs are enclosed and protected by two layers
of serous membrane which are collectively called
plural membrane or pleura. The outer layer, called
parietal membrane, lines the wall of the thoracic
cavity. The inner layer, called the visceral
membrane, covers the lungs themselves.
Between the visceral and parietal membranes
(pleurae) is a small space called pleural cavity. The
plural cavity contains a small amount of lubricating
fluid secreted by the serous membrane. This
pleural fluid reduces the friction between the
membranes when sliding over one another during
breathing.

34. Respiratory Muscles

35. Respiratory Muscles
Muscles of Inhalation:
• Diaphragm
• External intercostals
• Sternocleidomastoid
• Scalenes
Muscles of Exhalation:
• Internal intercostals
• External oblique
• Internal oblique
• Transverse abdominis
• Rectus abdominis

36. The scalene muscles are three paired
muscles (anterior, middle and posterior),
located in the lateral aspect of the neck.
Collectively, they form part of the floor of
the posterior triangle of the neck. The
scalenes act as accessory muscles of
respiration, and perform flexion at the
neck.

37. Diaphragm
• Is a skeletal muscle separating chest and
abdomen
• Inspiration: diaphragm contracts and
increases thoracic space
– air flows in
• Expiration: diaphragm relaxes and
decreases thoracic space
– air flows out
• Innervated by phrenic nerve fibers (C3, C4,
C5)

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Mechanisms of Breathing:
How do we change the volume of the rib cage ?
Inhalation is ACTIVE process
• Diaphragm
Rib Cage
Contract
Diaphragm
Volume
•External Intercostal Muscles
Intercostals
Contract
to Lift
Rib
Spine
Ribs Volume
Both actions occur simultaneously – otherwise not effective

39. Functions of Diaphragm
• Diaphragm is the muscle of:
• Inspiration
• Abdominal straining
• Weight-lifting
• Thoracoabdominal pump

40. Nervous Control of
Respiration
Respiration is controlled by the respiratory center in
the central nervous system. The respiratory
muscles contract as a result of nerve impulses
transmitted to them from centers in the brain and
relax in the absence of nerve impulses. These
nerve impulses are sent from clusters of neurons
located bilaterally in the medulla oblongata and
pones of the brain stem. This group of neurons,
collectively called respiratory center, which
is divided into three areas as:

41. 1.Medullary Rhythmicity Area:
2. It is located in the medulla oblongata. It
controls the basic rhythm of respiration.
There are inspiratory and expiratory areas.
During quiet breathing, inhalation lasts
for about 2 seconds and exhalation lasts
for about 3 seconds.
Inspiratory area establishes the basic
rhythm of breathing by generating nerve
impulses.

42. Inspiratory area sends impulses to the external
intercostal muscles through intercostal nerves (T1
to T11) and to the diaphragm via the phrenic
nerves (C3 to C5).
When the nerve impulses reach the diaphragm and
external intercostal muscles, the muscles contract
and inhalation occurs.
At the end of 2 seconds, the inspiratory area becomes
inactive and nerve impulses cease.
With no impulses arriving, the diaphragm and
intercostal muscles relax for about 3 seconds,
allowing lungs and thoracic wall to recoil. Then, the
cycle repeats.

43. Nervous Control of Respiration
cont…
• The neurons of the expiratory area remain
inactive during quiet breathing.
• However, during forceful breathing nerve
impulses from the inspiratory area activate
the expiratory area Impulses causing
contraction of the internal intercostal and
abdominal muscles and thus forceful
expiration occurs.

44. 2. Pneumotaxic Area: (pneumo= air; taxic=
arrangement)
In the upper pons, it transmits inhibitory impulses to the
inspiratory area to turn off the inspiratory phase before
the lungs become too full of air. Breathing rate is more
rapid when the pneumotaxic area is more active. It
means that it shortens the duration of inhalation.
3. Apneustic Area:
In the lower pons of the brain stem, the apneustic area
sends stimulatory impulses to the inspiratory area that
activate it and prolong inhalation. It causes a long and
deep inhalation. Thus pneumotaxic and apneustic area
coordinate the transition between inhalation and
exhalation.

45. Respiratory Volumes
• Tidal Volume (TV): The amount of air
normally inhaled or exhaled with one breath.
(500 ml)
• Inspiratory Reserve Volume (IRV): The
amount of (additional) air forcefully inhaled after
a normal tidal volume inhalation. (3000 ml)
• Expiratory Reserve Volume (ERV): The
amount of air forcefully exhaled after a normal
tidal volume exhalation. (1200 ml)
• Residual Volume (RV): The amount of air
remaining in the lungs after maximum expiration.
(1300 ml)

46. Respiratory Capacities
• Vital Capacity (VC): Maximum amount of air expired
after a maximum inspiratory effort. (4700 ml)
VC= TV+IRV+ERV
• Inspiratory Capacity (IC): Maximum amount of air
inspired after a normal tidal expiration. (3500 ml)
IC= TV+IRV
• Functional Residual Capacity (FRC): Volume of air
remaining in the lungs after a normal tidal volume expiration.
(2500 ml)
FRC= ERV+RV
• Total Lung Capacity (TLC): The amount of air in lungs
after a maximum inspiratory effort. (6000 ml)
TLC= TV+IRV+ERV+ RV

47. Clinical Conditions
• Inflammation of the pleural membrane is called
pleurisy or pleuritis and as a result the
accumulation of excess fluid in the pleural cavity
is called pleural effusion.
• The introduction of air into the plural cavity
(either by surgical opening or stab or gunshot) is
called pneumothorax while blood or pus in
it is called hemothorax. The collapse of
lungs is known as atelectasis (ateles =
incomplete; ectasis = expansion).

48. Clinical terminology of
ventilation
• Apnea: Temporary cessation of breathing.
• Dyspnea: Difficulty in breathing. Eg. SOB
• Eupnea: Normal breathing. 12 to 15 b/m
• Hyperpnea: Increased rate and depth of
breathing.
• Hyperventilation: Increased pulmonary
ventilation leading to low blood level of CO2

49. Hypoventilation: Decreased pulmonary
ventilation leading to increased blood level of CO2
Orthopnea: Dyspnea that occurs when a person is
lying down.
Tachypnea: Abnormal quick shallow breathing
Bradypnea: Abnormal slow breathing.
Hypoxia: Low oxygen level

50. Thank you