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BIOLOGY OF HUMAN AGING
Chapter 11
The Respiratory System
Outline
• Review of the Structure and Function
• Nasal Cavity, Pharynx, Trachea, Bronchi, Alveoli, Lungs
• Age-Related Changes
• Trachea and Bronchi, Alveoli, Lungs Structural Changes
• Age-Related Dysfunctions
• Chronic Obstructive Pulmonary Disease
– Emphysema
– Chronic Bronchitis
• Pneumonia
• Tuberculosis
• Pulmonary Embolism
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 oxygen and carbon dioxide levels.
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.
Human Respiratory System
Pressure Relationships
Figure 22.12
Blood Transports Gases Between Lungs & Tissues
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.
–
More prominent in males (Adam’s apple).
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.
Human Respiratory System
Alveoli (Sing. Alveolus): Grapelike clusters of tiny air sacs
with very thin elastic walls through which gas exchange
occurs.
– Oxygen in air enters blood in capillaries.
– Carbon dioxide in blood enters air in alveoli.
There are several million alveoli in the human lungs, with a
total surface roughly equivalent to a tennis court.
The walls of the alveoli are very delicate.
Alveolar macrophages are phagocytic cells that swallow
inhaled particles (dust, bacteria, etc.) and digest them.
Exchange of Gases Occurs in Alveoli
Human Breathing: Inhalation and Exhalation
Lung volume and using spirometer
Lung volume and using spirometer
Age-related changes
• Trachea and Bronchi
– Progressive calcification
– Smooth-muscle replaced by fibrous connective tissue
– Reduced elasticity of the lungs
– VC begin to decrease ~ 40 years of age
– Mucous membrane lining the trachea and bronchi
show degenerative changes
– Decrease activity of cilia and phagocytic activity of
the macrophages
Age-related changes
• Alveoli
– Gradual deterioration of the walls of alveoli
– The size increases but less surface area for the
gas exchange
– Cross-linkage
– More collagen fibers and less elastic fibers
– Declining oxygen levels in the blood
Age-related changes
• Lungs
– Lose their elastic recoiling capabilities and offer less
resistance to expansion
– Insufficient ventilation contributing to an overall
reduction in oxygen saturation of arterial blood.
– Surface area
– Diminished sensitivity of chemo-receptors that
monitor oxygen and CO2 levels in the blood.
Human Breathing is Automatically Controlled
Age-related changes
• Structural changes
– Kyphosis and the hunching over reduces the volume
of the thoracic cavity and make it more difficult to
expand the lungs
– Loss of Ca and weakening of muscles
– Diminished elasticity and increases fibrosis of the
lungs
– Stiffness of the rib cage
– Older individual rely more on the diaphragm
Age-related dysfunctions
• Dysfunctions of respiratory system are more common
in older individuals
• These are not merely a result of aging, rather due to
constant exposure to environmental stimuli (air
pollution & smoking)
• Air pollutants damage trachea, bronchi, alveoli
• Most frequently occurring pulmonary disorders:
– Restrictive (hinder lung expansion)
– Obstructive (involve respiratory airways  increased
resistance to air flow
Chronic Obstructive Pulmonary Disease (COPD)
• Characterized by chronic air flow obstruction in lungs
• Reduction in the ratio of forced expiratory volume in the first
second to forced vital capacity (FEV1/FVC)
• Symptoms:
• Difficulty breathing, wheezing, cough, etc…
• Increase rapidly in >50 years of age, frequent in men
•
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•
•
Cause:
Environmental factors and age (also genetic predisposition)
80% of cases is due to cigarette smoking
Two most common types: Emphysema & Chronic bronchitis
Emphysema
• Excessive air accumulates in lungs as they lose their ability to
ventilate properly
• More prevalent in older people
• Gradual development in response to smoking, bronchitis,
pulmonary irritants
• Mechanism
• Chronic irritation, smoking, infections  paralyze & deteriorate
mucus membrane cilia  excessive mucus production w/in
airways to the lungs  persistent cough
•  collapse of airways  hinders air flow through lungs  air
becomes trapped in alveoli
• Trapped air  alveoli remain inflated  expiration (normally
passive action) requires muscular resistance  significant energy
needed to exhale  development of Barrel Chest
 Over-inflated alveoli destroy alveoli’s wall  replaced by fibrous
tissue  hinder gaseous exchange
 Early stages: gaseous exchange fairly adequate  no cyanosis
 Later stages: great reduction in area where gas exchange occurs
 cyanosis even w/ mild physical effort
 Patients often have low maximum breathing capacity and high
residual air volume
 The disease can not be reversed and gradually worsens
 Therapy: positive-pressure oxygen therapy to force O2 into alveoli
 Emphysema puts extra load on heart (attempts to pump more
blood into lungs to compensate for O2 deficiency)
 Patients suffering from emphysema die from heart failure
Dirty lung of an Emphysema (smoking) patient
Bronchitis
 Acute or chronic inflammation of the bronchial tree
 Caused by bacterial infection or by irritants (smoke in inhaled air)
 Chronic bronchitis is due to long-term exposure to environmental
insults  more common in elderly
 Similar to emphysema airway irritation responds by mucus
production
 In severe cases, mucus membrane becomes swollen and partially
obstruct airway  severe hindrance of gas exchange  cyanosis
 Excess mucus buildup is removed by persistent coughing
Pneumonia
 Inflammation of the lower airways of the lungs
 Symptoms: Fever, cough, sputum production (not restricted to older
individuals)
 Classification (due to variability in causative agents):
 Community acquired: viruses (influenza) or pneumococcus
 Hospital acquired: gram negative bacilli (E. Coli) or Enterobacter
 Aspiration pneumonia: inhalation of foods or foreign bodies that
obstruct bronchus
 causes lung collapse, fluid accumulation, infection
 More common in older (bedridden) individuals
Classification of Pneumonia
Tuberculosis
 Caused by mycobacterium tuberculosis ; enters body with inspired
air  lung tuberculosis is the most common form
 Symptoms: early (subtle) weight loss, fever, cough
 Diagnosis: skin test, chest x-ray, sputum culture
 Lung phagocytes  destroy the bug  alive bacteria are walled off
in small or calcified nodules (Tubercle)
 Evading bacteria  spread  lung tissue replaced by fibrous tissue
 reduced vital capacity and difficulty breathing
 Antibiotics harnessed TB till mid-80s  resurgence due to AIDS
 Role of immune system in controlling outward signs of the disease
 Dormancy  impaired immune system  Reactivation
tuberculosis
Causative agent:
mycobacterium
tuberculosis
X-ray film of infected lung
Pulmonary Embolism
 Ambolus: blood clot or foreign objects that flows freely w/in blood
vessels
 Can reach vessels with small diameter, can not pass through them 
partial or complete block  reduced blood flow to the tissue  tissue
dies
 Pulmonary embolism: a clot that blocks a branch of pulmonary artery
 Symptoms: shortness of breath, chest pain, spitting blood, accelerated
heart beat and breathing rate, anxiety
 Can occur at any age, more common in bedridden older individuals
 Immobile patients tend to develop clots in leg veins (low blood flow)
 Treatment:
– Anticoagulant drugs (streptokinase)