Biology 248 Anatomy & Physiology II Chapter 19 Vicki Maroon National Institute of Technology
Section 19.1: Introduction
The respiratory system consists of passages that filter incoming air and transport it into the body, into the lungs, and to the many microscopic air sacs where gases are exchanged
Respiration is the process of exchanging gases between the atmosphere and body cells
It consists of the following events:
Transport of gases
Section 19.2: Why We Breathe
Respiration is necessary because of cellular respiration , the process by which animal cells use oxygen to release energy from nutrients we eat. The metabolic waste gas, carbon dioxide is produced during CR, and it must be transported to the lungs to be expelled .
Gas exchange, oxygen and carbon dioxide, occur at the cellular and molecular levels
Aerobic reactions of cellular respiration allow for:
Carbon dioxide generation forming carbonic acid
Section 19.3: Organs of the Respiratory System
The organs of the respiratory system can be divided into two tracts:
Upper respiratory tract
Lower respiratory tract
Larynx Bronchus Nostril Right lung Left lung Soft palate Pharynx Epiglottis Esophagus Frontal sinus Nasal cavity Hard palate Oral cavity Trachea
The Upper Respiratory Organs
Lined with mucous membranes .
Epithelium over connective tissue with many goblet cells (mucus).
Specifically, pseudostratified columnar ET in the trachea.
The mucus functions to trap debris.
The cilia beat the debris to the pharynx to be swallowed and destroyed by digestive enzymes.
This tissue also serves to warm and moisten incoming air.
Nose Frontal sinus Nostril Hard palate Uvula Epiglottis Hyoid bone Larynx Superior Middle Inferior Sphenoidal sinus Pharyngeal tonsil Nasopharynx Palatine tonsil Oropharynx Lingual tonsil Laryngopharynx Esophagus Tongue Trachea Nasal conchae Opening of auditory tube
primary bronchus leads into each lung and then branches into
secondary or lobar bronchi, which branch to each lobe and then branch into
tertiary or segmental bronchi which each serve one of 10 lobules (bronchopulmonary segment) that divide into
intralobular bronchioles which branch several times into tubes called
Larynx Right middle lobe Right superior (upper) lobe Right primary bronchus Secondary bronchus Right inferior (lower) lobe Alveolar duct Alveolus Respiratory bronchiole Tertiary bronchus Terminal bronchiole Trachea Left superior (upper) lobe Left inferior (lower) lobe
Branches of the Bronchial Tree
The successive divisions of the branches from the trachea to the alveoli are:
Techniques to save a life when a person stops breathing:
Extracorporeal membrane oxygenation
Blood out of body, through gas-permeable membrane to add oxygen and remove carbon dioxide, blood pumped back into body
Lung assist device
Hundreds of porous hair-thin fibers implanted into inferior vena cava, receives oxygen here and gets rid of carbon dioxide
Only 30% efficacy of normal respiratory system
Location = thoracic cavity
paired, cone-shape organs
covered by pleural (serous) membranes
pleural cavity filled with serous fluid with high surface tension so membranes act as one
Thyroid cartilage Cricoid cartilage Clavicle Scapula Rib cartilage Sternum Superior (upper) lobe of right lung Middle lobe of right lung Inferior (lower) lobe of right lung Superior (upper) lobe of left lung Inferior (lower) lobe of left lung Trachea Right lung Heart Left lung Pericardium Pleura Plane of section Pericardial cavity Right pleural cavity Visceral pleura Parietal pleura Left pleural cavity
Each lung is divided into lobes by fissures:
Right lung has 3 lobes.
Left lung has 2 lobes.
Each lobe :
receives a secondary bronchus
is divided into lobules (bronchopulmonary segment)
Each lobule :
is wrapped in elastic CT
contains a lymphatic vessel, an arteriole, a venule, and a branch from a terminal bronchiole
19.2 Clinical Application
Asbestosis = shortness of breath due to lung scar tissue
Beryllium used in metal alloys & nuclear power
Symptoms appear 10 years after exposure
Cough, shortness of breath, fatigue, loss of appetite, fever, night sweats, weigh loss
A disorder with many names
Extrinsic allergic alveolitis
9/11 associated air pollution
World trade center cough
Particles of fiberglass, asbestos, concrete, etc
Section 19.4: Breathing Mechanism
Breathing or ventilation is the movement of air from outside of the body into the bronchial tree and the alveoli
The actions responsible for these air movements are inspiration, or inhalation, and expiration, or exhalation
Atmospheric pressure due to the weight of the air is the force that moves air into the lungs
At sea level, atmospheric pressure is 760 millimeters of mercury (mm Hg)
Moving the plunger of a syringe causes air to move in or out
Air movements in and out of the lungs occur in much the same way
Diaphragm Air passageway Atmospheric pressure of 760 mm Hg on the outside Atmospheric pressure of 760 mm Hg on the inside (a) (b)
The diaphragm muscle pushes downward.
The size of thoracic cavity increases.
The pressure in the thoracic cavity decreases (758 mm Hg)
The air pressure inside the thoracic cavity (lungs) is less than the atmospheric pressure and therefore air rushes into lungs to equalize the pressure gradient.
Diaphragm (a) (b) Intra-alveolar pressure (760 mm Hg) Atmospheric pressure (760 mm Hg) Intra-alveolar pressure (758 mm Hg)
Adding CO 2 to air will stimulate rate and depth of breathing
Patients with COPD gradually adapt to high concentrations of CO 2
Therefore lower O 2 levels stimulate breathing
Caused by emotional upset
Lowered CO 2 levels & rise in pH
Localized vasoconstriction of cerebral arterioles
Decrease blood supply to brain
Can cause fainting
19.4 Clinical Application
Exercise and Breathing
Exercise increases breathing rate
Muscles need more O 2 but also produce more CO 2
P O and P CO 2 rates don’t change
Increase demand on respiratory & cardiovascular systems
“ out of breath” feeling = inability of cardiovascular system to move enough blood between lungs and cells
Section 19.6: Alveolar Gas Exchanges
The alveoli are the sites of the vital process of gas exchange between the air and the blood
Air is a mixture of gases:
.04% Carbon Dioxide
In a mixture of gases, the amount of pressure that each gas creates = partial pressure.
In air that reaches the alveoli:
O2 = 21% PO2 = 104 mm Hg
CO2 = .04% PCO2 = 40 mm Hg
Diffusion of gases through the respiratory membrane proceeds from where a gas is at high pp low pp.
PCO2 = 40 mm Hg PO2 = 104 mm Hg
PCO2 = 45 mm Hg PO2 = 40 mm Hg
Therefore, CO2 will flow from lung capillary to the alveolus & O2 will flow from alveolus to the lung capillary.
Capillary lumen Alveolus Macrophage Capillary Alveolus Red blood cell Diffusion of CO 2 Diffusion of O 2 Capillary endothelium Interstitial space Alveolar epithelium Type I (squamous epithelial) cell of alveolar wall Type II (surfactant- secreting) cell Fluid with surfactant Respiratory membrane Cell of capillary wall Alveolar fluid (with surfactant) Basement membrane of alveolar epithelium Basement membrane of capillary endothelium Respiratory membrane
Part of the wall of an alveolus is made up of cells (type II cells) that secrete pulmonary surfactant
The bulk of the wall of an alveolus consists of a layer of simple squamous epithelium (type I cells)
Both of these layers make up the respiratory membrane through which gas exchange takes place
AS AS BM IS RBC EP
Alveolus Diffusion of CO 2 Diffusion of O 2 Capillary Alveolar wall Blood flow (from body tissues) Blood flow (to body tissues) P CO 2 = 45 mm Hg P CO 2 = 40 mm Hg P O 2 = 40 mm Hg P O 2 = 104 mm Hg P O 2 = 104 mm Hg P CO 2 = 40 mm Hg
Diffusion Through the Respiratory Membrane
The rate of diffusion of gases also depends on a number of factors, including the following:
gas exchange surface area
breathing rate and depth.
Increased diffusion is favored with more surface area, shorter distance, greater solubility of gases and a steeper partial pressure gradient
Decreased diffusion occurs from decreased surface area
Exposure to high oxygen concentration
May damage lung tissue (esp. capillary wall)
Excess fluid escapes capillaries and flood alveolar air spaces
Interfers with gas exchange
Retrolental fibroplasia (RLF)
Infants with damaged retinal capillaries
Can lead to blindness
Section 19.7: Gas Transport
Blood transports O 2 and CO 2 between the lungs and the body cells
As the gases enter the blood, they dissolve in the plasma or chemically combine with other atoms or molecules
Almost all oxygen carried in the blood is bound to the protein hemoglobin in the form of oxyhemoglobin
Chemical bonds between O 2 and hemoglobin are relatively unstable
Oxyhemoglobin releases O 2 into the body cells
About 75% of the O 2 remains bound to hemoglobin in the venous blood ensuring safe CO 2 levels and thereby pH
Alveolus Capillary 2 2 2 (a) (b) Blood flow (from body tissues) Alveolar wall Oxygen molecules Hemoglobin molecules Diffusion of oxygen Oxyhemoglobin molecule Hemoglobin molecules Diffusion of oxygen Blood flow (to lungs) Blood P O = 40 mm Hg Blood P O = 95 mm Hg Tissue cells Tissue P O = 40 mm Hg
10 20 30 40 50 60 70 80 90 100 Oxyhemoglobin dissociation at 38°C % saturation of hemoglobin 10 0 40 50 60 70 90 80 100 1 10 120 130 140 20 30 P O 2 (mm Hg)
The release of oxygen from hemoglobin depends on many factors :
high blood [CO2]
low blood pH (acidity)
high blood temperature
Carbon Monoxide (CO) binds to hemoglobin more efficiently than oxygen.
If the hemoglobin (that is supposed to bind with oxygen) is bound to CO, much less Hb is available to bind and transport oxygen to the tissues
19.5 Clinical Application
Effects of High Altitude
High-altitude pulmonary edema (HAPE)
Severe attitude sickness with headache, nausea, vomiting, rapid heart rate and breathing, & cyanotic skin
Hypoxia causes vasoconstriction of pulmonary blood vessels
The amount of oxygen released from oxyhemoglobin increases with:
10 20 30 40 50 60 70 80 90 100 % saturation of hemoglobin 10 0 40 50 60 70 90 80 100 1 10 120 130 140 20 30 Oxyhemoglobin dissociation at 38°C 20 mm Hg 40 mm Hg 80 mm Hg P CO 2 = P O 2 (mm Hg) 10 20 30 40 50 60 70 80 90 100 Oxyhemoglobin dissociation at 38°C % saturation of hemoglobin 10 0 40 50 60 70 90 80 100 1 10 120 130 140 20 30 7.6 7.4 7.2 pH = P O 2 (mm Hg) 10 20 30 40 50 60 70 80 90 100 % saturation of hemoglobin 10 0 40 50 60 70 90 80 100 1 10 120 130 140 20 30 43°C 38°C 30°C 20°C 10°C 0°C P O 2 (mm Hg) Oxyhemoglobin dissociation at various temperatures Increased in P CO 2 Increased blood pH Increased blood temperature
19.6 Clinical Application
Disorders That Impair Gas Exchange:
Edema in alveoli causing reduced diffusion
Fibrous tubercles form causing reduced diffusion
Adult Respiratory Distress Syndrome
Caused by: pneumonia, near drowning, shock, sepsis, physical trauma, etc.
Results in collapsed lungs
Carbon Dioxide Transport
Blood flowing through capillaries gains CO 2 because the tissues have a high Pco 2
The CO 2 is transported to the lungs in one of three forms:
As CO 2 dissolved in plasma
As part of a compound with hemoglobin
As part of a bicarbonate ion
Tissue cell Cellular CO 2 Plasma Red blood cell Capillary wall Blood flow to systemic venule Tissue P CO 2 = 45 mm Hg CO 2 dissolved in plasma P CO 2 = 40 mm Hg Blood flow from systemic arteriole CO 2 combined with hemoglobin to form carbaminohemoglobin H 2 CO 3 H + combines with hemoglobin P CO 2 = 45 mm Hg HCO 3 - + H + CO 2 + H 2 O HCO 3 -
CO 2 CO 2 Alveolus Alveolar wall Capillary wall CO 2 HCO 3 - Carbaminohemoglobin Plasma Red blood cell P CO 2 = 45 mm Hg P CO 2 = 40 mm Hg CO 2 CO 2 dissolved in plasma Blood flow from pulmonary arteriole HCO 3 - + H + H 2 CO 3 H + released from hemoglobin Blood flow to pulmonary venule P CO 2 = 40 mm Hg + H 2 O CO 2 + hemoglobin
Section 19.8: Lifespan Changes
Lifespan changes reflect an accumulation of environmental influences and the effects of aging in other organ systems, and may include:
The cilia become less active
Swallowing, gagging, and coughing reflexes slowing
Macrophages in the lungs lose efficiency
An increased susceptibility to respiratory infections
A “barrel chest” may develop
Bronchial walls thin and collapse
Dead space increasing
Important Points in Chapter 19:
Identify the general functions of the respiratory system.
19.2: Why We Breathe
Explain why respiration is necessary for cellular survival.
19.3: Organs of the Respiratory System
Name and describe the locations of the organs of the respiratory system.
Describe the functions of each organ of the respiratory system.
19.4: Breathing Mechanism
Explain how inspiration and expiration are accomplished.
Name and define each of the respiratory air volumes and capacities.
Important Points in Chapter 19:
Calculate the alveolar ventilation rate.
List several non-respiratory air movements and explain how each occurs.
19.5: Control of Breathing
Locate the respiratory areas and explain control of normal breathing.
Discuss how various factors affect breathing.
19.6: Alveolar Gas Exchanges
Define partial pressure and explain its importance in diffusion of gases.
Describe gas exchange in the pulmonary and systemic circuits.
Important Points in Chapter 19:
Describe the structure and function of the respiratory membrane.
19.7: Gas Transport
Explain how the blood transports oxygen and carbon dioxide.
19.8: Lifespan Changes
Describe the effects of aging on the respiratory system.