The document summarizes the human respiratory system. It describes the main functions and components of the respiratory system, including the pathway of inhaled air through the nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles and alveoli where gas exchange occurs. It also discusses pulmonary function tests, lung volumes, respiratory disorders, gas transport in blood, and common respiratory diseases like asthma, bronchitis, pneumonia, emphysema and lung cancer. Cigarette smoke is identified as a major cause of respiratory diseases.

1. Chapter 9
Biology 25: Human Biology
Prof. Gonsalves
Los Angeles City College
Loosely Based on Mader’s Human
Biology,7th edition

2. Human Respiratory System
Functions:
 Works closely with circulatory system,
exchanging gases between air and blood:
 Takes up oxygen from air and supplies it to
blood (for cellular respiration).
 Removal and disposal of carbon dioxide
from blood (waste product from cellular
respiration).
Homeostatic Role:
 Regulates blood pH.
 Regulates blood oxygen and carbon dioxide
levels.

3. Blood Transports Gases Between Lungs and Tissues

4. Human Respiratory System
Components:
Nasal cavity, throat (pharynx), larynx (voice box),
trachea, bronchi, alveoli, and lungs.
Pathway of Inhaled Air:
 Nasal cavity
 Pharynx (Throat)
 Larynx (Voice Box)
 Trachea (Windpipe)
 Bronchi
 Bronchioles
 Alveoli (Site of gas exchange)
Exhaled air follows reverse pathway.

8. Human Respiratory System
1. Nasal cavity: Air enters nostrils, is filtered by hairs,
warmed, humidified, and sampled for odors as it flows
through a maze of spaces.
2. Pharynx (Throat): Intersection where pathway for air
and food cross. Most of the time, the pathway for air is
open, except when we swallow.
3. Larynx (Voice Box): Reinforced with cartilage. Contains
vocal cords, which allow us to make sounds by
voluntarily tensing muscles.
 High pitched sounds: Vocal cords are tense, vibrate
fast.
 Low pitched sounds: Vocal cords are relaxed,
vibrate slowly.
 More prominent in males (Adam’s apple).

11. Human Respiratory System
4. Trachea (Windpipe): Rings of cartilage maintain shape
of trachea, to prevent it from closing. Forks into two
bronchi.
5. Bronchi (Sing. Bronchus): Each bronchus leads into a
lung and branches into smaller and smaller bronchioles,
resembling an inverted tree.
6. Bronchioles: Fine tubes that allow passage of air. Muscle
layer constricts bronchioles. Epithelium of bronchioles
is covered with cilia and mucus.
 Mucus traps dust and other particles.
 Ciliary Escalator: Cilia beat upwards and remove
trapped particles from lower respiratory airways.
Rate about 1 to 3 cm per hour.

13. Pulmonary Function Tests
 Assessed by spirometry.
 Subject breathes into a closed system in
which air is trapped within a bell floating
in H20.
 The bell moves up when the subject
exhales and down when the subject inhales.

14. Spirogram
 Tidal volume:
 Amount of air expired with each breath.
 Vital capacity:
 The maximum amount of air that can be forcefully exhaled after maximum
inhalation.

15. Table 16.3 Terms Used to Describe Lung Volumes and
Capacities
Term Definition
Lung Volumes The four nonoverlapping components of the total lung
capacity
Tidal volume The volume of gas inspired or expired in an unforced
respiratory cycle
Inspiratory reserve volume The maximum volume of gas that can be inspired during
forced breathing in addition to tidal volume
Expiratory reserve volume The maximum volume of gas that can be expired during
forced breathing in addition to tidal volume
Residual volume The volume of gas remaining in the lungs after a maximum
expiration
Lung Capacities Measurements that are the sum of two or more lung volumes
Total lung capacity The total amount of gas in the lungs after a maximum
inspiration
Vital capacity The maximum amount of gas that can be expired after a
maximum inspiration
Inspiratory capacity The maximum amount of gas that can be inspired after a
normal tidal expiration
Functional residual capacity The amount of gas remaining in the lungs after a normal tidal
expiration

17. Anatomical Dead Space
 Not all of the inspired air reached the alveoli.
 As fresh air is inhaled it is mixed with anatomical
dead space.
 Conducting zone and alveoli where 02
concentration is lower than normal and C02
concentration is higher than normal.
 Alveolar ventilation: f x (TV- DS)
 F = frequency (breaths/min.).
 TV = tidal volume.
 DS = dead space.

18. Restrictive and Obstructive
Disorders
 Restrictive
disorder:
 Vital capacity
is reduced.
 FVC is normal.
 Obstructive
disorder:
 VC is normal.
 FEV1 is
reduced.

20. Breathing Ventilates the Lungs
Breathing: Alternation of inhalation and exhalation. Supplies
our lungs with oxygen rich air, and expels excess carbon
dioxide.
 Inhalation: Diaphragm contracts, moving downward and
causing rib cage, chest cavity, and lungs to expand. Air
rushes in, due to decrease in internal lung pressure as
lungs expand.
 Exhalation: Diaphragm relaxes, moving upwards and
causing rib cage, chest cavity, and lungs to contract. Air
rushes out, due to the increase in internal lung pressure as
lungs contract.
Breathing is controlled by centers in the nervous system to
keep up with body’s demands.

28. Hemoglobin helps transport CO2 and buffer blood
Hemoglobin is found in red blood cells
Functions:
 Transports oxygen
 Transport carbon dioxide
 Helps buffer blood
As carbon dioxide is picked up from tissues it is converted
into carbonic acid:
CO2 + H2O <-----> H2CO3 <----> H+ + HCO3
-
Carbon Carbonic acid Carbonate
ion
dioxide
Hemoglobin picks up most H + ions, so they don’t acidify the
blood.

29. Hemoglobin Loading and Unloading of Oxygen

30. Respiratory Acid-Base Balance
 Ventilation normally adjusted to keep
pace with metabolic rate.
 H2CO3 produced converted to CO2,
and excreted by the lungs.
 H20 + C02 H2C03 H+ + HC03
-

31. Respiratory Acidosis
 Hypoventilation.
 Accumulation of CO2 in the tissues.
 pH decreases.
 Plasma HCO3
- increases.
 Pc02 increases.

32. Respiratory Alkalosis
 Hyperventilation.
 Excessive loss of CO2.
 pH increases.
 Plasma HCO3
- decreases.
 Pc02 decreases.

36. Diseases of the Respiratory System
 Respiratory rate: 10 to 14 inhalations/minute.
 In one day, an average human:
 Breathes 20,000 times
 Inhales 35 pounds of air
 Most of us breathe in air that is heavily contaminated with
solid particles, ozone, sulfur oxide, carbon monoxide,
nitrogen oxides, and many other damaging chemicals.
 Breathing contaminated air can cause a number of diseases
including asthma, bronchitis, emphysema, and lung cancer.

39. Diseases of the Respiratory System
 Respiratory rate: 10 to 14 inhalations/minute.
 In one day, an average human:
 Breathes 20,000 times
 Inhales 35 pounds of air
 Most of us breathe in air that is heavily contaminated with
solid particles, ozone, sulfur oxide, carbon monoxide,
nitrogen oxides, and many other damaging chemicals.
 Breathing contaminated air can cause a number of diseases
including asthma, bronchitis, emphysema, and lung cancer.

40. Diseases of the Respiratory System
 Cigarette smoke is one of the worse air pollutants.
 Over 1 million people start smoking every year.
 Kills about 350,000 people every year in U.S.
 Contains 4000 different chemicals.
 Each cigarette smoked subtracts about 5
minutes from life expectancy.
 Cigarette smoke paralyzes cilia in airways,
preventing them from removing debris and
from protecting delicate alveoli.
 Frequent coughing is the only way airways can
clean themselves.
 Cigarette smoke also causes fetal damage,
which can result in miscarriage, premature
birth, low birth weight, and poor development.

41. Diseases of the Respiratory System
 Asthma: Condition in which breathing is
impaired by constriction of bronchi and
bronchioles, cough, and thick mucus
secretions. The severity and incidence of
asthma has risen dramatically in recent years,
especially in children. May be fatal if not
treated.
Causes: Attacks may be precipitated by
inhalation of allergens (e.g.: pollen, cats, and
cockroach proteins), pollutants, infection, or
emotional stress.
Treatment: Alleviates symptoms (e.g.:
immuno-suppressors, bronchodilators), but is
not a cure.

42. Diseases of the Respiratory System
 Bronchitis: Inflammation of the mucous
membranes of the bronchi. May present with
cough, fever, chest or back pain, and fatigue.
Causes: Associated with smoking, pollution,
and bacterial or viral infections.
 Pneumonia: Acute inflammation of the lungs.
Symptoms include high fever, chills, headache,
cough, and chest pain.
Causes: Bacterial, fungal, or viral infections.
Treatment: Antibiotics or other antimicrobials.

43. Diseases of the Respiratory System
 Emphysema: Permanent and irreversible
destruction of alveolar walls, resulting in loss of
lung elasticity and gas exchange surface.
Symptoms include shortness of breath,
difficulty exhaling, cough, weakness, anxiety,
confusion, heart failure, lung edema (swelling),
and respiratory failure.
Causes: Smoking, pollution, old age, and
infections.
Treatment: Oxygen to help breathing. No cure.

44. Diseases of the Respiratory System
 Lung Cancer: Cancerous growth that invades
and destroys lung tissue. Very high fatality
rate.
Symptoms include bloody sputum, persistent
cough, difficulty breathing, chest pain, and
repeated attacks of bronchitis or pneumonia.
Causes: Smoking (50% of all cases) and
pollution (radon, asbestos). Smokers are 10
times more likely to develop lung cancer than
nonsmokers.
Treatment: Surgery is most effective, but only
50% of all lung cancers are operable by time of
detection. Other treatments include radiation
and chemotherapy.

46. Human Fetus Exchanges Gases with Mother’s Blood
through the Placenta