FUNCTIONAL ANATOMY OF THE RESPIRATORY SYSTEM

Processes

1. Ventilation – movement of air in and out of lung

2. External respiration – gas exchange between air and blood at alveoli

3. Gas transport – oxygen and carbon dioxide in blood

4. Internal respiration – gas exchange between tissue and blood in capillaries

5. Cellular respiration – for aerobic; use of fuel with oxygen to produce energy

Zones and divisions

1. Conduction zone – warms and moistens; cleans; terminal bronchioles and bigger

2. Respiratory zone – respiratory bronchioles; alveolar ducts; alveoli

3. Upper respiratory system – nose to the pharynx

4. Lower respiratory system – larynx to the lungs

Nose

1. Function – warm, clean, moisten; olfaction; speech

2. External nose – vary greatly in size and shape

-a. Root – between eyebrows

-b. Bridge – between eyes

-c. Dorsum nasi – anterior margin

-d. Apex – tip of nose

-e. External nares – nostrils

-f. Alae – lateral to nares

3. Nasal cavity – open to the external nares

-a. Nasal septum – cartilage; perpendicular plate, ethmoid; vomer

-b. Posterior nares – where nasal cavity meets pharynx

-c. Roof – ethmoid and sphenoid bones

-d. Palate – floor of nasal cavity; separates from oral cavity

-e. Vibrissae – hairs that filter out dirt

-f. Olfactory mucosa – superior part of nasal cavity

-g. Conchae – three ridges; superior; middle; inferior; on lateral wall; turbulents

-h. Meatus – just below each conchae; superior; middle; inferior

-i. Mucosa – pseudostratified ciliated columnar epithelium

-j. Venous plexus – rich; under epithelium; warm air; bloody nose

4. Paranasal sinuses – frontal, sphenoid, ethmoid, and maxillary

Pharynx

1. Nasopharynx – posterior to nasal cavity; superior to soft palate

-a. Pharyngotympanic tube – tubes from middle ears open lateral wall

2. Oropharynx – from soft palate to epiglottis

3. Laryngopharynx – from epiglottis to larynx

4. Mucosa – becomes stratified Squamous in oropharynx and laryngopharynx

Larynx

1. Cartilage – 9 pieces form the framework

-a. Thyroid cartilage – large shield shaped; laryngeal prominence (Adam’s apple)

-b. Cricoid cartilage – ring of cartilage between thyroid cartilage and trachea

-c. Smaller cartilages – three pairs of cartilage (6)

-d. Epiglottis – closes over glottis; swallow; elastic; not hyaline

2. Mucosal folds – ligaments (cords) under the mucosa; cause it to fold

-a. Vestibular fold – superior fold; closes glottis

-b. Vocal fold – inferior fold; voice production

-c. Voice production – tighter cords, higher frequency

3. Mucosa – stratified squamous epithelium

4. Glottis –opening of the airway

5. Swallowing – larynx moves superiorly; epiglottis pulled over glottis

Trachea

1. Mucosa – pseudostratified ciliated columnar

2. Submucosa – connective tissue with many seromucus glands; much mucus needed

3. Adventia – outer most connective tissue layer

4. Hyaline cartilage – 16 - 20 C shaped rings; open end; esophagus; flexible; patent

5. Trachealis muscle – spans open end; esophagus expands; trachea narrows, cough

6. Esophagus – posterior to and attached to trachea; trachealis muscle

Bronchial tree

1. Primary bronchi – first branch of the trachea; enter lung

-a. Hilus – medial depression in lung; primary bronchi and major vessels enter it

2. Secondary bronchi – branches of the primary bronchi; to each lobe

3. Tertiary bronchi – branches of the secondary bronchi; segmental (10 right; 9 left)

4. Bronchioles – air passages under 1 mm in diameter

5. Terminal bronchioles – even small; less than 0.5 mm

6. Tissue composition – substantial changes as move down the respiratory tree

-a. Cartilage – rings replaced by irregular pieces; missing in bronchioles

-b. Epithelium – from ciliated pseudostratified to columnar to cuboid

-c. Smooth muscle – increases; in bronchioles a complete layer

Respiratory zone

1. Respiratory bronchioles – from terminal bronchioles; some alveoli; to the next

2. Alveolar duct – winding duct; terminate in alveolar sac

3. Alveolar sac – terminal cluster of alveoli

4. Alveoli – small spherical structures; gas exchange take place

Respiratory membrane

1. Type I cells – simple squamous; scant basal lamina

-a. Pulmonary capillaries – form web over alveoli

-b. Respiratory membrane – basal lamina of alveoli and capillary fuse

-c. External respiration – on one side of the membrane is air on the other, blood

2. Type II cells – cuboidal cells; make up much less

-a. Surfactant – excreted by these cells; reduces surface tension

3. Elastic fibers – surround alveoli; found through out respiratory tree

4. Alveolar pores – between alveoli; pressure equalization; alternate route

5. Dust cells – alveolar macrophages; keep surface sterile

Lungs

1. Root – vascular and bronchial attachments

2. Costal surface – curved surface; close contact to ribs

3. Base – inferior surface; on diaphragm

4. Hilus – concave surface; rest on lungs

5. Cardiac notch – concavity in left lung; left part of heart

6. Lobes – each served by a secondary bronchi

-a. Right lung – upper, middle, and lower lobes

-b. Left lung – upper and lower lobes

7. Fissures – separates lobes

-a. Right lung – horizontal (upper-middle); oblique (middle-lower)

-b. Left lung – oblique fissure

8. Bronchopulmonary segment – tertiary bronchi; 10 on right; 8 to 10 on left

9. Lobule – smallest visible subdivision; served by a single bronchiole

10. Stroma – mostly elastic connective tissue between air spaces

Blood supply to lungs

1. Pulmonary circulation – or pulmonary circuit

-a. Pulmonary arteries – deoxygenated blood pumped from right heart to lung

-b. Pulmonary capillary – surround alveoli; external respiration

-c. Pulmonary veins - oxygenated blood from lungs to left heart

2. Bronchial circulation – delivers oxygenated blood to lung, bronchi, ad pleura

-a. Bronchial arteries – run along branching bronchi; from aorta

-b. Alveoli – served by pulmonary circuit

-c. Bronchial veins – small; some systemic venous drainage; most pulmonary circuit

Innervation of the lung

1. Pulmonary plexus – enters lungs at root; runs along bronchi and vessels

2. Parasympathetic fibers – constrict air tubes

3. Sympathetic fibers – dilate them; more rare than parasympathetic

The pleura

1. Parietal pleura – lines thoracic wall and superior face of diaphragm

2. Visceral pleura – covers the external lung surface; dips down to become fissure

3. Pleural fluid – fills the pleural cavity

4. Pleural cavity – between the two pleura

5. Surface tension – of pleural fluid resist separation of the pleura

6. Pleurisy – inflammation of the pleura; more or less fluid made

MECHANICS OF BREATHING

Pressure relationship in thoracic cavity

1. Intrapulmonary pressure – inside alveoli; changes during breathing

2. Intrapleural pressure – in pleural cavity; must be less than alveoli or atmosphere

3. Pneumothrorax – air in the pleural cavity; could result in collapsed lung

Pulmonary ventilation: inspiration and expiration

1. Volume, pressure, flow relationships – volume changes, pressure changes, flow

2. Boyle’s law – P₁V₁= P₂V₂ ; pressure varies inversely with volume

Inspiration

1. Quiet inspiration – at rest; ↑ thorax cavity volume; ↓ pressure (1 mm, relative)

2. Inspiratory muscles – results from the contraction of these muscles

-a. Diaphragm – moves inferiorly; lungs increases in length (most important)

-b. Intecostal – pull rib cage outward; lungs outward dimensions increase

3. Pressure/volume changes

-a. Volume – few millimeters in either direction; 0.5 L

-b. Intrapulmonary pressure – drops about 1 mm; air rushes in

4. Deep forced respiration – other muscles; sternocleidomastoidal; pectoralis major

Expiration

1. Quiet expiration – passive; elastic property of lungs; muscles relax

2. Inspiratory muscles – relax; rib cage returns to original position

3. Lung recoils – pull back to their regular shape

4. Intrapulmonary pressure – due to decrease in volume; ↑pressure (1 mm, relative)

5. Forced expiration – active; abdominal and other muscles involved

Physical factors influencing pulmonary ventilation

1. Resistance – friction or drag of flowing air

2. Alveolar surface tension – strong attraction of liquid molecules

3. Lung compliance – expandability

Resistance

1. F=ΔP/R – flow directly proportional to pressure; inversely to resistance

2. Conducting tube diameter – determines the resistance in the respiratory tree

3. Bronchioles – give greatest resistance to air flow

-a. Smooth muscle – constricts and dilates to alter air flow

-b. Parasympathetic stimulation – when stimulated by histamine, reduce flow

4. Accumulations – mucus, tumors, other materials; air way resistance

Alveolar surface tension forces

1. Water molecules – have strong pull; would collapse alveoli

2. Type II alveolar cells – produce a surfactant that decreases surface tension

3. Surfactant – detergent like substances; contain proteins and lipids

4. Infant respiratory distress syndrome – premature; do not produce surfactant

Lung compliance

1. Elasticity – lots of elastic connective tissue

2. Factors reducing lung compliance

-a. Fibrosis – reduces resilience

-b. Mucus – blockage caused by infection

-c. Costal cartilage ossification – as occurs in old age

Respiratory volumes

1. Tidal volume – amount inhaled or exhaled with each breath; 500 ml

2. Inspiratory reserve volume – amount forcible inspired after tidal inhalation; 3100

3. Expiratory reserve volume – amount forcible expired after tidal exhalation; 1200

4. Residual volume – amount left in lungs after forced expiration; 1200 ml

Respiratory capacities

1. Total lung capacity – amount in lung after max. insp.; TV+IRV+ERV+RV; 6000

2. Vital capacity – amount exp. after max. insp. ; TV+IRV+ERV; 4800

3. Inspiratory capacity – amount to be insp. after normal exp.; TV + IRV

4. Functional residual capacity – amount in lungs after tidal volume exp. ERV + RV

Dead space

1. Anatomical dead space – air remaining in conduction zone (150 ml); 350 ml left

2. Alveolar dead space – alveoli stop functioning; collapsed or obstructed

3. Total dead space – sum of alveolar and anatomical dead space

Pulmonary function

1. Spirometer – inverted bell over water; measure lung volumes

2. Forced expiratory volume – amount of air expelled in a particular time interval

-a. Obstructive pulmonary disease – would have low forced expiratory volume

3. Forced vital capacity – deep breath; forcible expel maximum

-a. Restrictive pulmonary disease – structural or functional alteration; diagnosed

Nonrespiratory air movement

1. Coughing – air forced against closed glottis

2. Sneezing – like cough but air forced into nasal cavity

3. Crying –inspiration followed by short expirations

4. Laughing – lot like crying

5. Hiccup – sudden inspiration due to diaphragm spasm

6. Yawn – deep inspiration; ventilates all alveoli

GAS EXCHANGES IN THE BODY

Composition of air

1. Mixture of gases – air is nitrogen, oxygen, carbon dioxide, and water vapor

2. Dalton’s law – total pressure equal sum of pressure exerted by each; proportional

3. Partial pressure – pressure exerted by each gas in a mixture of gas

4. P_N2 – 597 mm; 78% of air

5. P_O2 – 159 mm; 21% of air

6. P_CO2- 0.3 mm; 0.04% of air

7. P_H2O – 3.7 mm; 0.46% of air

Air – water interface

1. Henry’s law – amount of gas into liquid proportional to sol. coef. and part. pres.

2. Solubility differences – vary considerable for atmospheric gas

-a. Carbon dioxide – 0.57 solubility coefficient; most soluble

-b. Oxygen – 0.024 solubility coefficient; 1/20^th as soluble carbon dioxide

-c. Nitrogen – 0.012 solubility coefficient; ½ as soluble as oxygen

Composition of alveolar gas

1. P₀₂ – 13.7%; mixing; oxygen moves in to blood

2. P_CO2 – 5.2%; carbon dioxide moves out into alveoli

External respiration

1. Partial pressure gradient – between the alveoli and the blood

-a. Entering blood P_O2 – 40 mm

-b. Alveolar P_O2 – 104 mm; equilibrium reached by oxygen entering blood

-c. Leaving blood P_O2 – 104 mm

-d. Entering blood P_CO2 – 45 mm

-e. Alveolar P_CO2 – 40 mm; equilibrium reached by carbon dioxide leaving blood

-f. Leaving blood P_CO2 – 40 mm

2. Perfusion-ventilation coupling – autoregulation; blood goes where there is oxygen

3. Respiratory membrane structure - very thin; 140 m²

Internal respiration

1. Oxygen exchange – at tissue; out of blood and into tissue

-a. Entering blood P_O2 – 105 mm

-b. Tissue P_O2 – 40 mm; equilibrium reached by oxygen leaving blood

-c. Leaving blood P_O2 – 40 mm

2. Carbon dioxide exchange – in tissue; out of tissue and into blood

-a. Entering blood P_CO2 – 40 mm

-b. Tissue P_CO2 – 45 mm; equilibrium reached by carbon dioxide entering blood

-c. Leaving blood P_CO2 – 45 mm

TRANSPORTATION OF RESPIRATORY GASES

Oxygen Transport

Association / dissociation of oxygen and hemoglobin

1. Oxyhemoglobin (HbO₂) - hemoglobin oxygen combination

2. Reduced hemoglobin (HHb) – deoxyhemoglobin; lost it’s oxygen

3. Cooperation – the binding of each oxygen gives more affinity for binding more

Influences of P_O2 on hemoglobin saturation

1. Oxygen hemoglobin dissociation curve – not linear; due to cooperation

2. Oxygen content – amount of oxygen carried in 100 ml of blood; % volume

3. Arterial blood – PO2 = 104mm; 98% saturated; 20 % oxygen content

4. Venous blood – PO2 = 40mm; 75% saturated; 15% oxygen content; reserve

Other factors influencing hemoglobin saturation

1. High metabolism – increases heat and carbon dioxide; decrease oxygen affinity

2. Temperature – decreases oxygen affinity; increases BPG production

3. P_CO2 – decreases pH; increases the amount of hydrogen ions

4. pH decrease – H⁺ ion concentration; more acidity

5. Bohr effect – hydrogen ions reduce hemoglobin’s affinity for oxygen

6. BPG – 2,3-biphosphoglycerate; RBC anaerobic; binds to hemoglobin

Impaired oxygen transport

1. Hypoxia – inadequate supply of oxygen to body tissue

2. Anemic hypoxia – hypoxia resulting from anemia

3. Ischemic (stagnant) hypoxia – impaired circulation; embolism; congestive HD

4. Histotoxic hypoxia – unable to use oxygen due to toxin like cyanide

5. Hypoxemic (hypoxic) hypoxia – low arterial oxygen; CO poisoning; ventilation

Carbon Dioxide Transport

Mode of transport

1. Dissolved – no more than 10%

2. Carbaminohemoglobin – no more than 30%

-a. Globin binding – doesn’t compete with oxygen binding

-b. Haldane effect – deoxygenated hemoglobin binds to carbon dioxide more readily

-c. Bohr effect – hydrogen ions bounded by hemoglobin; less affinity for oxygen

3. Bicarbonate ion – about 70% of carbon dioxide transported

-a. Blood – CO₂ + H₂O ↔ H₂CO₃ ↔ H⁺ + HCO₃^- ; not as fast as in RBC

-b. RBC carbonic anhydrase – CO₂ + H₂O ↔ H₂CO₃ ↔ H⁺ + HCO₃^-; much faster

Bicarbonate transport

1. Tissue – Carbon dioxide comes out of tissue and into blood

-a. Carbon dioxide (CO₂) – much of it enters RBC

-b. Carbonic anhydrase – CO₂ + H₂O ↔ H₂CO₃

-c. Carbonic acid (H₂CO₃) – H₂CO₃ ↔ H⁺ + HCO₃^-

-d. Bicarbonate ion (HCO₃^-) – leaves RBC; carried to lungs

-e. Chloride shift (Cl^-) – comes into RBC; balances negative ion leaving

2. Lungs – Carbon dioxide comes out of blood and into alveoli

-a. Bicarbonate ion (HCO₃^- ) – enters RBC

-b. Chloride shift (Cl^-) – leaves RBC; balances negative ion coming in

-c. Carbonic acid (H₂CO₃) – H⁺ + HCO₃^-↔ H₂CO₃

-d. Carbonic anhydrase – H₂CO₃↔ CO₂ + H₂O

-e. Carbon dioxide (CO₂) – into blood; into alveoli

CONTROL OF RESPIRATION (VENTILATION)

Neural controls

1. Inspiratory area – dorsal in medulla; quiet inspiration; insp. muscles

-a. Eupnea – normal respiration; 12 – 15 times per minute

2. Expiratory area – ventral in medulla; exhalation; muscles

3. Pneumotaxic center – pons; fine tunes breathing rhythm; prevents over inflation

-a Pontine respiratory group.– also called this

4. Apneustic center – pons; coordinates transition between inspiration and expiration

5. Irritant reflexes – bronchiole receptor; vagal nerve; coughing response

6. Hering-Breuer reflex – stretch receptors; vagus nerve; respiratory center; modify

7. Hypothalamus – emotions (gasp); temperature (jump in cold water)

8. Cortical control – can bypass all centers to voluntary control of breathing

Chemical factors

1. Central chemoreceptors – laterally in medulla

2. Peripheral chemoreceptors – aorta and carotid bodies

3. High P_CO2 – arterial blood above 40 mm

-a. Hypercapnia – term for this

-b. Peripheral chemoreceptors – signal to medullary respiratory centers

-c. Central chemoreceptors – respond to free hydrogen ion; not carbon dioxide

-d. Hyperventilation – increased depth and rate of breating

4. Low P_CO2 – in arterial blood

-a. Hypocapnia – term for this

-b. Hypoventilation – slow shallow breathing

-c. Apnea – breathing stops; until arterial P_CO2 returns to normal

5. Very low P_O2 – peripheral receptors; respiratory center; increase rate

6. Low arterial pH - peripheral receptors; increase ventilation

EXERCISE AND HIGH ALTITUDE ADJUSTMENTS

Exercise

1. Ventilation – increases 10 to 20 fold

2. Hyperpnea – dipper more vigorous; little changes in rate

3. Neural factors – psychological; cortical; proprioceptors in muscles

4. Oxygen debt – and lactic acid; little effect; not resp; cardio. And muscle

High altitudes

1. Acute mountain sickness (AMS) – traveling quickly from sea level to >8000 ft.

-a. Symptoms – headaches; nausea; dizziness; pulmonary and cerebral edema

2. Acclimatization – respiratory and hematopoietic

-a. Respiratory – 2-3 L/min. increase within a couple of days

-b. Hematopoietic – kidneys; erythropoietin; increase RBCs

RESPIRATORY DISORDERS

Common infections

1. Laryngitis – inflammation of larynx

2. Rhinitis – nose inflammation due to cold virus

3. Flu – influenza virus; respiratory system

Chronic obstructive pulmonary disease (COPD)

1. Symptoms – smoking; difficult labored breathing; hypoxemia; obstruction

2. Emphysema – air trapped; elastin breakdown; lung fibrosis

3. Chronic bronchitis – bronchial edema; excessive mucus

Bronchial asthma

1. Symptoms –coughing; bronchial constriction; obstructive; episodic

2. Causes – inflammation due to type I hypersensitivity

3. Treatment – anti-inflammatory steroid; away from bronchodilators

Tuberculosis

1. Symptoms – fever, night sweats, hacking cough; spitting up blood

2. Mycobacterium tuberculosis – bacterial cause

3. Primary infection – immune response walls off in fibrous or calcified tubercles

4. Compromised immunity – as in AIDS; drug users; active disease

5. Epidemiology – becoming a real problem; not keeping with treatment

6. Treatment – 12 months antibiotics

Lung Cancer

1. Squamous cell carcinoma – epithelium of bronchi; masses that cavitate and bleed

2. Adenocarcinoma – peripheral lungs; alveolar cells to solitary nodules

3. Small (oat) cell carcinoma – clusters of cells; from primary bronchi;like lyphocyte