Exam 3 resp and digest, exam 3 meta

respiratory system

used to acquire oxygen and remove carbon dioxide from blood

7 structures of the respiratory system

external nose- for air inspiration

nasal cavity- clean, warm, humidify air

pharynx- common passageway for food and air

larynx- voice box, keeps airway patent

trachea- air cleaning tube into lungs

bronchi- tubes that direct air into lungs

lungs- network of alveoli and capillaries for gas exchange

conducting zone

nose to small air tubes in lungs strictly for pulmonary ventilation (breathing)

respiratory zone

specialized, small tubes and alveoli where gas exchange occurs

pulmonary ventilation

breathing

external respiration

gas exchange between blood and alveoli/lungs

transport of respiratory gases

blood carries gases throughout the body (hemoglobin)

internal respiration

gas exchange between blood and tissue cells= cellular respiration (systemic circuit)

additional functions of the respiratory system

regulation of blood pH- altered by changing blood CO2 levels

production of chemical mediators- ACE involved in blood pressure regulation

voice production- movement of air past vocal folds makes sound and speech

olfaction- smell occurs when airborne molecules drawn into nasal cavity

protection- preventing entry of microorganisms and removing them from respiratory surfaces

primary functions of respiratory system

pulmonary ventilation, external respiration, transport of respiratory gases, internal respiration

external nose

hyaline cartilage plates covered by skin

nasal cavity

-extends from nares (nostrils) to choanae (openings into pharynx)

-vestibule: just inside nares, lines with stratified squamous epithelium

-hard palate: floor or nasal cavity covered by highly vascular mucous membrane

-nasal septum: partition dividing cavity (anterior cartilage; posterior vomer, part of ethmoid)

-conchae: bony ridges on lateral walls with meatuses between

-openings to paranasal sinuses and nasolacrimal duct

nasal cavity features

-air passageway

-cleans air with hairs in vestibule and cilia in nasal conchae. conchae also create turbulence and increase surface area

-humidifies and warms air with pseudostratified ciliated columnar epithelium with goblet cells and tears draining from nasolacrimal duct

-contains olfactory epithelium for sense of smell

-resonating chambers for speech (with paranasal sinuses)

paranasal sinuses

-in the frontal, sphenoid, ethmoid, and maxillary bones

-lighten the skull

-help warm and moisten air moving through upper respiratory tract

-inflammation can lead to headache (sinusitis)

pharynx

-3 parts

-common opening for digestive and respiratory systems

nasopharynx

pseudostratified columnar epithelium with goblet cells; mucus and debris swallowed; openings of eustachian tubes; floor is soft palate and uvula; posterior wall houses pharyngeal tonsil

oropharynx

shared with digestive system. Lined with moist stratified squamous epithelium and contains palatine and lingual tonsils

laryngopharynx

epiglottis to esophagus. Lined with moist stratified squamous epithelium

larynx

-voice box that houses ligaments used for speech

-ligaments extend from arytenoids to thyroid cartilage

-contains vestibular folds/false vocal cords

-vocal folds or true vocal cords: sound production. opening between the glottis

thyroid cartilage

largest, adam's apple

cricoid cartilage

most inferior, base of larynx

epiglottis

attached to thyroid and has flap near base of tongue (elastic)

arytenoid

attached to cricoid

corniculate

attached to arytenoids

cuneiform

contained in mucus membrane anterior to corniculates

functions of the larynx

1. maintain open passageway for air movement: thyroid and cricoid cartilages

2. epiglottis and vestibular fold prevent swallowed material from moving into larynx

3. vocal folds are primary source of sound production

4. pseudostratified ciliated columnar epithelium traps and prevents debris from entering lower respiratory tract

trachea

-membranous tube of dense regular CT and smooth muscle

-supported by 15-20 hyaline cartilage C-shaped rings

-posterior surface is trachealis muscle that contracts during coughing (esophagus is posterior)

-lumen lined with pseudostratified ciliated columnar epithelium with goblet cells (mucus traps debris and cilia push it toward larynx and pharynx)

-divides to form left and right primary bronchi

carina

cartilage at bifurcation which initiates cough reflex when irritated with debris

tracheobronchial tree

-trachea and network of air tubes in lungs

-ciliated for removal of debris

-cartilage holds tubes open and smooth muscle controls diameter. as tubes become smaller, the amount of cartilage decreases and amount smooth muscle increases

passageway through the bronchi

1. primary bronchi

2. secondary/lobar bronchi

3. segmental/tertiary bronchi

4. bronchioles

5. terminal bronchioles

secondary/lobar bronchi

-each serves a lobe of the lungs

-contain cartilage plates lined w/ pseudostratified ciliated columnar epithelium

-3 on right & 2 on left

segmental/tertiary bronchi

supply bronchopulmonary segments

bronchioles

<1 mm in diameter

terminal bronchioles

-no cartilage but prominent smooth muscle

-lined with ciliated simple cuboidal epithelium

bronchodilation

-smooth muscle relaxes

-decreased resistance to air flow so airflow increases

bronchoconstriction

-smooth muscle contracts

-increased resistance to air flow so airflow decreased

asthma attack

severe bronchoconstriction due to inflammation

alveoli

-site of pulmonary gas exchange

-300 million between 2 lungs

-no cilia: debris removed by macrophages that move into nearby lymphatics or into terminal bronchioles

respiratory bronchioles

branch from terminal bronchioles and have few alveoli

alveolar ducts

from respiratory bronchioles; alveoli open from duct

alveolar sacs

chambers connected to 2 or more alveoli at end of an alveolar duct

type 1 pneumocytes/alveolar cells

-thin squamous epithelial cells

-90% of surface of alveolus (transport much easier)

-gas exchange

type 2 pneumocytes/alveolar cells

-round or cube-shaped secretory cells

-produce surfactant to allow alveoli to expand during inspiration, decreases surface tension

respiratory membrane

-as RM increases, gas exchange decreases

-location of pulmonary gas exchange

-membrane very thin and composed of alveolar cell layer, capillary endothelial and interstitial space (air-blood barrier)

layers of respiratory membrane

1. Thin layer of fluid lining the alveolus

2. Alveolar epithelium (simple squamous epithelium)

3. Basement membrane of the alveolar epithelium

4. Thin interstitial space

5. Basement membrane of the capillary endothelium

6. Capillary endothelium composed of simple squamous epithelium

pleura

-thin double-layered serosal membrane that divides thoracic cavity into pleural compartments and mediastinum

pleural cavity

-surrounds each lung and is formed by the pleural membranes from thoracic cavity

-filled with pleural fluid that lubricates and assists in expansion/recoil of lungs

visceral pleura

adheres to lung: simple squamous epithelium

parietal pleura

adheres to internal thoracic wall, superior diaphragm, heart

pleurisy

inflammation of the pleura (often from pneumonia)

lungs

-base: sits on diaphragm

-apex: superior portion, above clavicle

-hilum: where bronchi and blood vessels enter

-right lung: 3 lobes separated by fissures

-left lung: 2 lobes and cardiac notch

pulmonary arteries

bring poorly oxygenated blood to lungs from right side of heart for oxygenation

pulmonary veins

-return oxygenated blood to left side of heart

-superficial and deep lymphatic vessels exit from hilum

-superficial drain superficial lung tissue and visceral pleura

-deep drain bronchi and associated CT

-no lymphatics drain alveoli

at rest, atmospheric and thoracic pressure and volume are

almost the same

boyle's law

- P=K/V (p=pressure, v=volume, k=constant at a given temp)

- as volume of container increases (thoracic cavity during inspiration) pressure inside decreases (inversely proportional)

- air flows down its pressure gradient

during inspiration air flows

into lungs

during expiration air flows

out of lungs

atmospheric pressure (Patm)

- 760 mmHg at sea level

- respiratory pressures are relative to Patm

- (-) respiratory pressure

P atm

- zero respiratory pressure = P atm

intrapulmonary pressure (Ppul)

-pressure in alveoli

-fluctuates with breathing

-always eventually equalizes with P atm

intrapleural pressure

-Pip

- -4mmHg (756 mmHg)

-creates a vacuum, makes sure lungs don't collapse

forces promoting lung collapse

elasticity of lungs and surface tension of alveolar surfactant

forces promoting lungs expansion

-elasticity of chest wall and low Pip

-pressure in pleural space < pressure in lungs

-pleural space acts like a vacuum (sucks lungs open)

pneumothorax

-atelectasis

-collapsed lung due to removal of delta P

partial pressure

pressure exerted by each gas in a mixture

dalton's law

total pressure = sum of partial pressures

partial pressures of gases in the environment

nitrogen- 600 mmHg

oxygen- 160 mmHg

carbon dioxide- 0.3 mmHg

total= 760 mmHg

solubility coefficient

measure of how soluble a gas is in a liquid

henry's law

concentration of a gas in a liquid is determined by its partial pressure and its solubility coefficient at a given temperature

diffusion coefficient

-rate at which a gas diffuses into and out of a liquid or tissue

-factors: solubility coefficient and molecular weight of gas

diffusion coefficient for O2 compared to relative diffusion coefficient for CO2

CO2= 20

O2= 1

(20:1)

diffusion of gases through a respiratory membrane depends on:

- membrane thickness (increased thickness= decreased diffusion rate)

- diffusion coefficient

- surface area

- partial pressure differences: PO2 higher in alveoli than blood (opposite for CO2)

mechanisms of alveolar pulmonary ventilation

atmospheric air pressure (Patm)

intra-pulmonary pressure (Ppul) = air pressure in alveoli

during rest intrapulmonary pressure vs atmospheric pressure

1. Ppul = Patm - no air movement at end of expiration

2. Ppul < Patm - air movement into lungs due to increase in thoracic volume

3. Ppul = Patm - no air movement at end of inspiration

4. Ppul > Patm - air moves out of lungs due to decrease in thoracic volume

factors affecting alveolar ventilation

1. lung recoil: tendency for lungs to decrease in size after being stretched

2. alveolar elastic recoil: alveolar walls return to original shape after being stretched

3. surface tension: film of fluid lining alveoli tends to make alveoli collapse due to water molecule polarity

surfactant

reduces surface tension, produced by type 2 pneumocytes

infant respiratory distress syndrome

inadequate surfactant production in newborns or premature babies. Leads to increased surface tension and alveolar collapse.

diffusion through respiratory membrane depends on

1. diffusion coefficient of gas

2. partial pressure gradients: alveolar PO2 > blood PO2 (opposite for CO2)

3. membrane thickness: thicker respiratory membrane=lower diffusion rate. tuberculosis/pneumonia increase membrane thickness

4. surface area: decreased surface area=decreased diffusion rate. emphysema/lung cancer decrease available surface area

external respiration (partial pressure gradients promoting gas exchange)

-driven by pressure gradients

-ventilation: amount of gas reaching alveoli

-perfusion: amount of blood flow circulating alveoli

-ventilation perfusion coupling is tightly regulated

internal respiration (partial pressure gradients promoting gas exchange)

driven by pressure gradients

transport of oxygen

-98.5% of O2 transported by hemoglobin (cooperative binding for O2)

-1.5% dissolved in plasma

factors affecting hemoglobins affinity for O2

1. PO2: more O2 released when PO2 is decreased in tissues

2. temperature: more O2 released when temperature increased

3. blood pH: more O2 released when pH decreased

4. PCO2: more O2 released when PCO2 increased

5. 2,3-bisphosphoglycerate (BPG): more O2 released when increased BPG

transport of carbon dioxide

-7% dissolved in plasma

-23% bound to globin of hemoglobin

-70% transported as bicarbonate ion (HCO3-) - either as RBC or in blood plasma. CO2+H2O <-> H2CO3 <-> H+ + HCO3- catalyzed by carbonic anhydrase

-when CO2 levels are high in tissues: HCO3-/Cl- antiporter removes HCO3 from RBC via chloride shift. removing HCO3 from RBC promotes more HCO3 formation in RBC

-at lungs: HCO3 move into RBC and bind with H+ -> H2CO3. H2CO3->CO2+H2O. CO2 diffuses from blood into alveoli

haldane effect

as Hb binds to CO2 its affinity for O2 decreases. less O2 bound to Hb means CO2 can bind

venous return

-arterial blood O2 saturated is ~98%

-capillaries receive ~25% O2

-venous blood ~75% saturated (most O2 bound to Hb, venous return, for low PO2 in high altitudes or heavy exercise

regulation of pulmonary ventilation - local control

-chemoreceptors, baroreceptors

-pulmonary capillary perfusion

-pulmonary ventilation-perfusion coupling. disrupted by insufficient blood flow or air flow in alveoli

-regional distribution of blood flow partially determined by alveolar PO2 (primarily by gravity)

low PO2 (pulmonary) causes

arterioles to constrict so blood is shunted to the region of lung where alveoli are better ventilated

low PO2 (systemic circuit) causes

arterioles to dilate to deliver more blood to tissues

what happens when ventilation is less than perfusion?

-decreased ventilation and/or increased perfusion of alveoli causes local increase in PCO2 and decrease in PO2

-pulmonary arterioles constrict

-decrease in perfusion balances and decrease in ventilation

what happens when ventilation is more than perfusion?

-increased ventilation and/or decreased perfusion of alveoli causes local decrease in PCO2 and increase in PO2

-pulmonary arterioles dilate

-increase in perfusion balances and increase in ventilation

neural control of pulmonary ventilation

- under voluntary control when eating or speaking

- under involuntary control during sleep or when focused on other tasks

what areas of the brain regulate breathing?

pons and medulla oblongata

dorsal respiratory group (DRG)

-produces normal involuntary rhythm of breathing (eupnea)

-stimulates diaphragm (phrenic nerve)

-stimulates intercostals and abdominal muscles (basic rhythm of inspiration)

ventral respiratory groups (VRG)

-receives input from chemoreceptors and mechanoreceptors and other sources to modify respiratory rhythm

pontine respiratory center

-pontine (pneumotaxic) respiratory group (PRG)

-modulates pulmonary ventilation rate

-some neurons operate only in inspiration and others only in expiration (some in both)

-connects to medullary respiratory center and appears to play role in switching between inspiration and expiration and making it smooth

effect of PCO2 and pH on respiratory rate

-CO2 major regulator of pulmonary gas exchange during rest or exercise. small increase in blood [CO2] triggers large increase in rate and depth of ventilation (hyperventilation). decreased blood pH triggers hyperventilation

-medulla oblongata chemoreceptors more important for regulation of PCO2 and pH

-carotid bodies respond rapidly to change in blood pH due to exercise

hypercapnia

PCO2 > normal

hypocapnia

PCO2 < normal

hering-breuer reflex and respiratory rate

-sensed by mechanoreceptors

-limits depth of inspiration and prevents over inflation of lungs. stretch receptors in walls of bronchi and bronchioles. APs initiated with stretch and inhibit respiratory center (results in expiration)

cerebral and limbic control of respiratory rate

-rate and depth of respiration controlled voluntarily and involuntarily by cerebral cortex

-during exercise rate changes controlled by inputs to respiratory center

-highest level of exercise without significant change in blood pH is anaerobic threshold. beyond this, pH decreases and pulmonary ventilation increases

-emotions affect respiratory center (hyperventilation or gasps when crying

apnea

absence of breathing (voluntary or involuntary)