Chapter 25, f 09

1.Human Anatomy,Second Edition McKinley & O'Loughlin Chapter 25 Lecture Outline: Respiratory System 25-

Respiratory system is used for gas exchange: oxygen in and carbon dioxide out

Works closely with the cardiovascular system

Consists of anupperrespiratory tractand alower respiratory tract .

Conducting portion transports air .

From the nose to the bronchioles

Respiratory portion carries out gas exchange .

composed of small airways called respiratory bronchioles and alveolar ducts as well as air sacs called alveoli

Breathing (pulmonary ventilation).

Inhalation (inspiration)

Exhalation (expiration)

Gas exchange,gas conditioning, sound production, olfaction, regulation of blood pH, and defense.

Most common serious genetic disease in Caucasians (1/3200 births - 5% are carriers)

A missing chloride pump causes sodium and water to move from the mucus back into the secretory cells, dehydrating the mucus covering the epithelial surface

Mucus becomes thick and sticky clogging lungs, and ducts of the pancreas and salivary glands.

Pulmonary infections and destruction of pancreas.

In the skin, the chloride transport protein works in the opposite direction making skin salty tasting.

Treatment: break up mucus, replace pancreatic enzymes, etc. Also insertion of healthy gene.

Composed of the nose and nasal cavity, paranasal sinuses, pharynx (throat), and associated structures.

All part of the conducting portion of the respiratory system.

Warms air, moistens, traps and moves gunk

Resonating chamber for speech

Pseudostratified ciliated columnar epithelium (cilia beat toward the throat)

Four bones of the skull contain paired air spaces called the paranasal sinuses.

decrease skull bone weight

give resonance to voice

Named for the bones in which they are housed.

Thethroat.

Originates posterior to the nasal and oral cavities and extends to the bifurcation of the larynx and esophagus.

Common pathway for both air and food .

Walls are lined by a mucosa and contain skeletal muscles that areprimarily used for swallowing .

Flexible lateral walls are distensible in order to force swallowed food into the esophagus.

Has threeregions

Posterior to the nasal cavity and superior to the soft palate .

Normally, only air passes through .

Material from the oral cavity and oropharynx is typically blocked from entering the nasopharynx by the soft palate, which elevates whenwe swallow.

In the lateral walls, paired auditory tubesconnect to the middle ear.

Posterior wall has a single pharyngeal tonsil (commonly called the adenoids).

Posterior to the oral cavity.

Bounded by the edge of the soft palate superiorly and the hyoid bone inferiorly.

Common respiratory and digestive pathway .

2 pairs of muscular arches form the entrance from the oral cavity.

Lymphatic organs, tonsils, here provide the first line of defense against ingested or inhaled foreign materials.

Inferior, narrowed region of the pharynx.

Extends inferiorly from the hyoid bone and is continuous with the larynx and esophagus.

Terminates at the superior border of the esophagus and is equivalent to the inferior border of the cricoid cartilage in the larynx.

The larynx (voice box) forms the anterior wall

Lined with a nonkeratinized stratified squamous epithelium

Permits passage of both food and air.

Conducting airways(larynx, trachea, bronchi, bronchioles and their associated structures).

Respiratory portionof the respiratory system (respiratory bronchioles, alveolar ducts, and alveoli).

Voice boxis a short airway bounded posteriorly by thelaryngopharynx and inferiorly by the trachea.

Prevents swallowed materials from entering the lower respiratory tract.

Conducts air into the lower respiratory tract.

Produces sounds.

Supported by a framework of nine pieces of cartilage thatare held in place by ligaments and muscles.

Pseudostratified ciliated columnar epithelium begins below the vocal cords.

Unpaired

epiglottis- covers the opening of the larynx when swallowing

thyroid- has prominence called the Adams apple

cricoid- base of the others. Airway landmark for a tracheostomy

Paired

arytenoid- attachment point for vocal cords

corniculate- attachment point for false vocal cords

cuneiform

The inferior vocal ligaments,covered by a mucous membrane,are called thevocal folds .

thetrue vocal cordsproduce sound when air passes between them

attached to arytenoid cartilages

the tension, length,and position of the vocal folds determine the quality of the sound.

The superior vestibular ligaments, along with the mucosa covering them, are called thevestibular folds .

thefalse vocal cordshave no function in sound production, but protect the vocal folds.

attached to the corniculate cartilages .

Inflammation

Causes: virus, bacteria, overuse

Symptoms: hoarse voice, sore throat, maybe fever

Severe cases may spread to epiglottis

May dangerously obstruct airway in a child

Thewindpipe.

Anterior to the esophagus, inferior to the larynx, and superior to the primary bronchi of the lungs.

15 to 20C-shaped tracheal cartilages.

reinforce and provide some rigidity to ensure that the trachea remains open (patent) at all times

At the sternal angle (T5), the trachea bifurcatesinto the right and left primary bronchi.

Each primary bronchus projects laterally toward each lung.

The most inferior tracheal cartilage separates the primary bronchi at their origin and forms an internal ridge called the carina.The carina is very sensitive and may initiate a cough reflexif something lands there.

A highly branched system of air-conducting passages that originate from the bronchi and progressively branch before terminating in terminal bronchioles.

Incomplete rings of hyaline cartilage support the walls of the primary bronchi to ensure that they remain open.

Right primary bronchus is shorter, wider, and more vertically orientedthan the left primary bronchus.

Foreign particles are more likely to lodge in the right primary bronchus.

Theprimary bronchienter the hilum of each lung together with the pulmonary vessels, lymphatic vessels, and nerves.

Each primary bronchus then branches intosecondary bronchi (or lobar bronchi).

The left lung has two secondary bronchi since it has two lobes.

The right lung has three lobes and three secondary bronchi.

They further divide into tertiary bronchi.

The right lung is supplied by 10 tertiary bronchi, and the left lung is supplied by 8 to 10 tertiary bronchi.

Each tertiary bronchus is called a segmental bronchusbecause it supplies a part of the lung called a bronchopulmonarysegment.

As branching occurs, several structural changes occur

Cartilage rings become cartilage plates and then cartilage disappears

Pseudostratified ciliated columnar tissue becomes cuboidalin the terminal bronchioles (need macrophages then) and finally simple squamous in the respiratory bronchioles

As the cartilage decreases, there is an increase in the smooth muscle which is affected by the ANS and chemicals such as histamine and epinephrine

Inflammation

Causes: viruses, bacteria, chemicals, particulate matter, cigarette smoke

Acute bronchitis

Rapid development after an infection, e.g., a cold

Resolves usually in 10-14 days

Chronic bronchitis

Long-term exposure to irritants

Large amounts of mucus with a 3 mo. cough

Permanent damage may occur leading to increase chances of bacterial infections and increased chance of pneumonia

Lungs contain small saccular outpocketings called alveoli.

An alveolus is about 0.25 to 0.5 mm in diameter.

Its thin wall is specialized to promote diffusion of gases between the alveolus and the blood in the pulmonary capillaries.

Gas exchange can take place in the respiratory bronchioles and alveolar ducts as well as in the lungs, which contain approximately 300400 million alveoli (70 m 2 ).

Alveoli are the major site for gas exchange.

The spongy natureof the lung is due to the packing of millions of alveoli together.

Type 1 alveolar (squamous pulmonary epithelial) cells

Type 2 alveolar (septal) cells produce surfactant which reduces surface tension in the lungs preventing collapse of the air sacs

Alveolar macrophages or dust cells

Respiratory distress syndrome

Lack of surfactant

Often in preemies(less than 7 months) or infants of diabetic mothers

1.5% carried dissolved in the plasma

98.5% carried by the heme of Hb

Normally, Hb gives up about 25% of the O 2to the tissues

In active tissues, Hb gives up more O 2

The partial pressure gradient of O 2 ,pH, and temperature affect the amount of O 2released by the Hb

CO binds to heme 200x more tightly than oxygen .

Symptoms: cherry pink, nausea, sleepiness

Treatment: pure oxygen

From the tissues:

7% dissolved in plasmaas CO 2

23% binds to globinof Hb forming carbaminohemoglobin

70% is converted to H 2 CO 3by carbonic anhydrase which then quickly dissociates into H +and HCO 3 -(which quickly moves out of the RBC and is carried in the plasma)

In the lungs, the reverse occurs

The outer surface of each lung is tightly covered by the visceral pleura, while the internal thoracic walls, the lateral surfaces of the mediastinum, and the superior surface of the diaphragm are lined by the parietal pleura.

The parietal and visceral pleural layers are continuous at the hilum of each lung.

Thepleura are serous membranes , simple squamous on top of connective tissue.

The potential space between these serous membrane layers is the pleural cavity.

The pleural membranes produce a thin, serous fluid that circulates in the pleural cavity and acts as a lubricant.

Free air in pleural cavityfrom an external injury or internally (e.g., broken rib)

Collapsed lung or part of lung results = atelectasis

Large amount requires a tube for removal

Dangerous type is tension pneumothorax where hole acts as a one-way valve

Fluids may accumulate in pleural cavity

Hemothorax if blood

Hydrothorax if serous fluid

Empyema if pus

Inflammation of pleura

May get decreased pleural fluid leading to pain or

May get increased pleural fluid leading to pressure on the lungs

Cone shaped.

Its base rests upon the diaphragm.

Its apex projects superiorly to a point that is slightly superior and posterior to the clavicle.

Both lungs are bordered by the thoracic wall anteriorly, laterally, and posteriorly, and supported by the rib cage.

The lungs are separated from each other by the mediastinum.

Surface in contact with the thoracic wall is called the costal surface of the lung.

Each segment is anautonomousunit.Therefore, a segment may be removed if diseased leaving the other segments intact.

Infection in the alveoli

Causes: viruses, bacteria, and sometimes fungi

Tissue swelling and WBCs accumulate decreasing gas exchange

Contagious

Symptoms: cough, fever, rapid breathing, sputum

Treatment: antibiotics, respiratory support, and medications for symptoms and possibly supplemental oxygen

Pulmonary trunkand its branches carry deoxygenated blood

Bronchial arteriesbring oxygenated blood from the systemic circuit

Two blood suppliescommunicateand most of the blood returns to the heart through the pulmonary veins

Lymph nodes and vessels are located within the connective tissue of the lung as well as around the bronchi and pleura.

Pulmonary ventilation or breathing

Exchange between atmosphere and lungs

About 16x/minute

About 500 ml of air exchanged/breath

Pulmonary or external respiration

Exchange between lungs and blood

Transport by blood

Tissue respiration or internal respiration

Between blood and cells

(Cellular respiration in mitochondria)

The pressure of a gas decreases if the volume of the container increases, and vice versa.

Elevation of the ribs increases the lateral dimensions of the thoracic cavity, while depression of the ribs decreases the lateral dimensionsof the thoracic cavity.

Diaphragm actively moves down with inspiration and passively up during normal expiration. Most important muscle for breathing.

Inhalation

The scalenes help increase thoracic cavity dimensions by elevating the first and second ribs during forced inhalation.

The ribs elevate upon contraction of theexternal intercostals , thereby increasing the transverse dimensions of the thoracic cavity during inhalation.

Exhalation

Contraction of theinternal intercostals depresses the ribs, but this only occurs during forced exhalation .

Normal exhalation requires no active muscular effort.

A small transversus thoracis extends across the inner surface of the thoracic cage and attaches to ribs 26. It helps depress the ribs.

Two posterior thorax muscles also assist with respiration.

In addition, some accessory muscles assist with respiratory activities.

Physical factors

Volition (conscious control)

Emotional factors

Chemical factors (most important)

Concentration of oxygen has little effect usually

Concentration of carbon dioxide has the most important effect

Increased arterial partial pressure of CO 2

Increases partial pressure of CO 2or decreases pH in CSF stimulatecentral chemoreceptors in the medulla(70% of response)

Stimulatesperipheral chemoreceptors in the carotid and aortic bodiesmediate 30% of response

Afferent impulses go to medullary respiratory centers

Efferent impulses go to respiratory muscles

Increased ventilation (more CO 2exhaled)

Arterial pCO 2and pH return to normal

The trachea, bronchial tree, and lungs are innervated by the autonomic nervous system.

The autonomic nerve fibers that innervatethe heart also send branches to the respiratory structures.

Pulmonary plexus

Sympathetic innervation mainly causes bronchodilation

Parasympathetic innervation mainly causes bronchoconstriction

The involuntary, rhythmic activities that deliver and remove respiratory gases are regulated in the brainstem.

Regulatory respiratory centers are located within the reticular formation through both the medulla oblongata and pons.

Medulla sets mainly the rate (basic rhythm)

Dorsal group is the inspiratory center

Ventral group is the expiratory center for forced expiration

Pons sets the depth

Apneustic center gives inspiratory drive

Pneumotaxic center inhibits apneustic center and limits the length of inspiration and promotes expiration

Phrenic nerve serves the diaphragm

Intercostal nerves serve the external intercostals

Less efficient with age due to structural changes.

Decrease in elastic connective tissue in the lungs and the thoracic cavity wall.

Loss of elasticity reduces the amount of gas that can be exchanged with each breath and results in a decrease in the ventilation rate.

Vital capacity of lung decreases by 35% by age 70.

Emphysema may cause a loss of alveoli or their functionality

Reduced capacity for gas exchange can cause an older person to become short of breath upon exertion.

Carbon, dust, and pollution material gradually accumulate in our lymph nodes and lungs (less macrophages and ciliary function)

Cardiovascular and respiratory systems affect each other.

Increase in pulmonary disorders.

Thickness of respiratory membrane

Ex., edema increases thickness

Surface area of the respiratory membrane

Ex., emphysema and cancer decrease S.A.

Partial pressure of gas

Ex., less partial pressure at high altitude

Common features

Smoking, difficult breathing, coughing and infections common, most hypoxic, retain carbon dioxide so acidosis.

Disability and ultimately develop respiratory failure (death)

Emphysema

Alveoli enlarge.Inflammation leads to fibrosis and airways lose elasticity.

Hard to exhale and leads to exhaustion

Overinflation leads to a barrel chest

Air retained - > pink puffers(cyanosis late)

Chronic bronchitis

Inflammation of mucosa of lower respiratory passages -> increased mucus -> impaired ventilation and gas exchange-> increased risk of lung infection (e.g., pneumonia)

Hypoxia and carbon dioxide retention early in disease and cyanosis is common ->blue bloaters

A chronic condition characterized by episodes of bronchoconstriction and wheezing, coughing, shortness of breath and excess pulmonary mucus.

Usually a sensitivity to an airborne agent.Upon reexposure, a localized immune reaction occurs in the bronchi and bronchioles.

Usually lasts an hour or two.

Eventually, the walls may become permanently thickened. Severe attacks may be fatal.

Treatment: inhaled steroids and bronchodilators.Important to avoid triggering agent.Allergy shots may help some.

Smoking increases the risk and severity of atherosclerosis and is directly related to the development of cancers of the lung, esophagus, stomach, and urinary bladder.Smoking also increases wrinkling and impotency.

Lung cancer: smoking causes 85%.

Increases mucus

Paralyzes cilia and decreases macrophage activity

Has many carcinogens

Highly aggressive and frequently fatal .

1/3 cancer deaths in U.S, 7% 5 year cure rate.

Detection is late and it spreads fast. Average 9 month survival after diagnosis.

Treatment

Resection is best if not too late

Chemotherapy and radiation may be the only options

Three major types

Squamous cell carcinoma most common type from transformed epithelial cells.

Adenocarcinoma from mucin-producing glands.

Small-cell (oat-cell) carcinoma arises from the primary bronchi and eventually invades the mediastinum. From neuroendocrine cells and may produce hormones.Aggressive and early metastasis.

Sudden and unexplained death of an infant younger than 1 year(usually 2-4 months old and 60% male)

SIDS babies have trouble regulating and maintaining B.P., breathing and body temperature. Stress plus one or more of these three factors appears to be involved.

Back-to-sleep campaign has reduced incidence.

At birth,

Powerful contractions of diaphragm and external intercostal muscles cause inhalation

Rib cage expands and never returns to its former shape (important forensically).We never completely empty our lungs after birth.

More breaths increase inflation and surfactant helps prevent collapse.

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Chapter 25, f 09