the respiratory system copyright © the mcgraw-hill companies, inc. permission required for...

The Respiratory System

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Lecture Outline


o Major function is gas exchangeo Works with the cardiovascular

system to accomplish:• Breathing• External respiration• Internal respiration• Transport of gases


o The Respiratory Tract• Nasal hairs, cilia, and mucus cleanse

inhaled air Lysozyme in the mucus help kill bacteria Mucociliary escalator

• Inhaled air is warmed by superficial blood vessels lining the airways

• Air is moistened by the mucous membrane


• The Nose The only external portion of the

respiratory system Contains two nasal cavities

Lined by a mucous membrane Nasal conchae increase the surface area for

moistening and warming inhaled air Odor receptors located in the olfactory

epithelium


• The Pharynx (the “throat”) Connects the nasal and oral cavities to

the larynx Three parts:

Nasopharynx Oropharynx Laryngopharynx

Tonsils provide the primary lymphatic tissue defense for breathing

The air passage and the food passage cross


• The Larynx Passageway for air between the pharynx

and trachea Houses the vocal cords The epiglottis prevents food from entering

the larynx


• The Trachea (the windpipe) Connect the larynx to the primary bronchi Ventral to esophagus C-shaped cartilaginous rings Mucosal lining has pseudostratified

ciliated columnar epithelium that form the mucociliary escalator


• The Bronchial Tree The trachea divides into the right and left

primary bronchi The primary bronchi branch into

secondary bronchi Three for the right lung Two for the left lung

The secondary bronchi divide into tertiary bronchi

Bronchioles are the smallest conducting airways


o The Lungs• Paired, cone-shaped organs• Each lobe is divided into lobules• Each lobule has a bronchiole that

serves many alveoli• Pleurae

Double layered serous membrane The visceral pleura adheres to the surface of

the lung The parietal pleura lines the inside of the

thoracic cavity Produces a lubricating serous fluid


• The Alveoli Alveolar sacs are made up of simple

squamous epithelium surrounded by blood capillaries

Site of gas exchange Alveoli must stay open to receive inhaled

air Surfactant lowers the surface tension of water

lining the alveoli preventing them from collapsing completely

Respiratory distress syndrome occurs in premature infants who lack surfactant


• Respiratory Membrane Facilitates rapid gas exchange Composed of juxtaposed alveolar

epithelium and the capillary epithelium Extremely thin Large surface area (50-70m2)

Mechanism of Breathing

o Ventilation• The manner in which air enters and

exits the lungs• Conditions to consider:

The lungs lie within the sealed-off thoracic cavity

The lungs adhere to the thoracic cavity wall by way of the pleurae

A continuous column of air extends from the pharynx to the alveoli of the lungs


• Inspiration Active phase of ventilation Diaphragm contracts and flattens External intercostal muscles contract, and

the rib cage moves upward and outward Thoracic cavity volume increases, causing

the lungs to increase in volume Air pressure within the alveoli

(intrapulmonary pressure) decreases Air flows from an area of higher pressure

(atmospheric pressure) to an area of lower pressure (within the lungs)

Figure 14.6a


• Expiration Usually the passive phase of ventilation The diaphragm relaxes and resumes its

dome shape The intercostal muscles relax and the rib

cage moves down and in The volume of the thoracic cavity

decreases and the lungs recoil Lung volume decreases and the

intrapulmonary pressure increases Since intrapulmonary pressure is now

greater than atmospheric pressure, air will flow out of the lungs


• Maximum Inspiratory Effort Involves the accessory muscles of

respiration Erector spinae Pectoralis minor Scalene and sternocleidomastoid muscles

Help increase the size of the thoracic cavity larger than normal

• Forced Expiration During heavy exercise, singing, etc. Involves contraction of abdominal wall

muscles


o Spirometer – instrument that records the volume of air exchanged during breathing

o Spirogram – shows the measurements recorded by a spirometer


o Respiratory Volumes• Tidal volume

Normal, relaxed breathing About 500 mL

• Vital capacity Maximum volume of air that can be inhaled plus the

maximum volume of air that can be exhaled Depends on:

Inspiratory reserve volume Forced inspiration Increases the volume of air beyond the tidal volume by

2,900 mL Expiratory reserve volume

Increased volume of expired air 1,400 mL

• Residual volume Amount of air remaining in the lungs after a forced

expiration 1,000 mL


• Control of Ventilation Controlled by a primary respiratory center

in the medulla oblongata The phrenic nerve carries impulses to the

diaphragm The intercostal nerves stimulate the

external intercostal muscles Normal breathing rhythm also requires

input from the pons


Can be influenced by nervous and chemical input

Nervous input Can influence depth and rate of breathing Cerebral cortex, limbic system,

hypothalamus, and other brain centers Chemical input

The respiratory center is sensitive to the levels of CO2 and H+

Chemoreceptors in the carotid and aortic bodies are sensitive to the level of oxygen in the blood

Gas Exchange and Transport

o External Respiration• Exchange of gases in the lungs (between

the air in the alveoli and the blood in the pulmonary capillaries)

• Oxygen Higher concentration in the alveoli Diffuses from the alveoli into the blood

• Carbon dioxide Higher concentration in the blood Diffuses from the blood in the pulmonary

capillaries to the alveoli• Partial pressure

Amount of pressure exerted by each gas Symbolized as PO2 and PCO2

Alveolar PO2 is higher than in the blood


o Internal Respiration• Exchange of gases in the tissues (between

the blood in systemic capillaries and tissue fluids)

• Oxygen Higher concentration in the blood Diffuses from the blood into the tissue fluid

• Carbon dioxide Higher concentration in the tissue fluid Diffuses from the tissue fluid into the blood

• PO2 in the tissue fluid is lower than in the blood


o Gas Transport• Oxygen Transport

Transported by hemoglobin in the red blood cells

Can combine with oxygen – oxyhemoglobin Can release oxygen - deoxyhemoglobin

Small amount transported in the plasma

• Carbon Dioxide Transport


• Carbon Dioxide Transport As a dissolved gas in blood plasma and in

the cytoplasm of red blood cells Combined with globin portion of

hemoglobin – carbaminohemoglobin Most is carried as bicarbonate ions

Carbon dioxide combines with water to form carbonic acid

Carbonic acid dissociates into hydrogen ions and bicarbonate ions

Excess H+ combines with the globin portion of hemoglobin (reduced hemoglobin)

Bicarbonate ions diffuse out of red blood cells into the plasma


• pH The respiratory system regulates pH

Bicarbonate/Carbonic acid buffer system is altered by breathing.

Hypoventilation = increased CO2 = decreased pH = acidosis (pH less than 7.35)

Hyperventilation = decreased CO2 = increased pH = alkalosis (pH greater than 7.45)

Respiration and Health

o Upper Respiratory Tract Infections• Can spread from the nasal cavities to

the sinuses, middle ears, and larynx• Viral infections can lead to secondary

bacterial infections• Strep throat

Primary bacterial infection Caused by streptococcus pyogenes Can lead to a generalized upper

respiratory infection


• Sinusitis Infection of the cranial sinuses Develops when nasal congestion blocks

openings to the sinuses Symptoms include:

Postnasal discharge Facial pain

Treatment depends on restoring proper drainage of the sinuses


• Otitis Media Bacterial infection of the middle ear Often a complication seen in children who

have a nasal infection Pain is the primary symptom Other symptoms include:

Sense of fullness Hearing loss Vertigo Fever

Treatment is antibiotics


• Tonsillitis Tonsils become inflamed and enlarged Tonsillectomy – surgical removal of tonsils

• Laryngitis Inflammation of the larynx Hoarseness leads to the inability to talk in

an audible voice Causes:

Upper respiratory infection Overuse


o Lower Respiratory Tract Disorders• Lower Respiratory Infections

Bronchitis Bacterial infection of the primary and

secondary bronchi Usually preceded by a viral URI

Pneumonia Viral or bacterial infection of the lungs Bronchi and alveoli fill with thick fluid Risk factors include:

Advanced age Weakened immune system Smoking and being immobilized

May be localized in specific lobules of the lungs


Tuberculosis Caused by the tubercle bacillus bacterium Lung tissue develops tubercles around the

invading pathogens Tuberculosis skin test can detect if a person has

ever been exposed to the bacteria


• Restrictive Pulmonary Disorders Vital capacity is reduced Lungs have lost their elasticity Pulmonary fibrosis

Fibrous connective tissue buildup in the lungs Can be caused by inhaling:

Silica Coal dust Asbestos Clay Cement Flour Fiberglass


• Obstructive Pulmonary Disorders Air does not flow freely in the airways Maximal inhalation or exhalation time is

greatly increased COPD

Develop slowly, over a long period of time Recurrent Chronic bronchitis

Airways are inflamed and filled with mucus Bronchi have undergone degenerative

changes


Emphysema Incurable disorder Alveoli are distended Alveolar walls have been damaged and the

surface area available for gas exchange has been reduced

Often preceded by chronic bronchitis Lungs have lost their elasticity Exhaling is difficult and residual volume

increases Less oxygen reaches the heart and brain


Asthma – acute obstructive disorder Disease of the bronchi and bronchioles Marked by:

Wheezing Breathlessness Sometimes a cough and expectoration of

mucus Airways are sensitive to irritants Is not curable, but treatable


Lung Cancer Linked to smoking Progressive steps in the development of lung

cancer: Thickening and callusing of the cells lining

the primary bronchi Cells with atypical nuclea appear in the

callused lining Cells break loose and penetrate other

tissues (metastasis) Pneumonectomy – surgical removal of a

lobe of a lung or removal of the entire lung

Effects of Aging

o Respiratory fitness decreases with ageo Maximum breathing capacities declineo Gas exchange in the lungs becomes

less efficiento Respiratory membrane thickenso Ciliated cells of the trachea decline in

numbero Respiratory diseases are more common

Homeostasis

o Gas Exchangeo Regulation of Blood pHo Control of Blood Pressureo Defense

the respiratory system copyright © the mcgraw-hill companies, inc. permission required for...

Documents

larynx slide

surfactant slide

respiratory system copyright

respiratory system othe

olfactory epithelium

mucous membrane slide

mucociliary escalator

cardiovascular system