the respiratory system Flashcards
what are the functions of the respiratory / circulatory system
- R: pulmonary ventilation, breathing, inspiration / expiration
- C/R: gas exchange of O2 and CO2 from air to lungs vice versa
- C: transport O2 and CO2 around body systemic BV and tissues / cells
- other: regulation of pH (lungs), olfactory (nose), sound production (larynx)
list aspects of upper and lower respiratory tract
- U: nose, nasal cavity, pharynx
- L: larynx, trachea, bronchi, lungs
describe the functional anatomy (conducting / respiratory zones)
C: conducts air into lungs
- nose, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles
- air is adjusted to body temp, humidified, filtered
- anatomical dead space (150mL air)
R: site of gas exchange between air and blood
- respiratory bronchioles, alveolar ducts, alveolar sac, alveoli
what is the external / internal nose
external:
- hyaline cartilage (lateral nasal cartilage, septal cartilage, lateral crus of greater alar cartilage)
- bones (frontal / nasal bone frontal process of maxilla)
- warms / moisturises / filters air, modifying speech
internal:
- large cavity in anterior aspect of skull
- palatine / maxillary bones (hard palate), ethmoid bone, nasal conchae (maxillary), nasal septum / vomer (medial wall)
- communicates with pharynx
describe the nasal cavity
- superior / middle / inferior nasal conchae: protrude from lateral walls, increase SA, enhance air turbulence
- respiratory mucosa: mucous / serous contain lysozyme and defensins, ciliated epithelium move contaminated mucous posteriorly to throat
- olfactory mucosa: lines superior cavity, olfactory receptors (form olfactory nerve)
what is the pharynx
- muscular tube (13cm), starts at choana (base of skull) ends at cricoid cartilage (C6)
- nasopharynx, oropharynx, laryngopharynx (becomes oesophagus)
- passage of air and food, resonating chamber (modify quality of voice), immune (adenoids in nasopharynx / palatine / lingual tonsils in oropharynx)
- 2 layers, outer circular and inner longitudinal (similar to intestine), skeletal muscles (swallowing)
what is the larynx
- midline of neck (C4-C6), anterior of oesophagus, attaches superiorly to hyoid bone (U shape)
- connects laryngopharynx to trachea
- airway, routes air and food, voice production
- hollow muscular, 9 cartilages, dense connective tissue
what are the vocal ligaments
- elastic fibres (core of vocal cords)
- opening between them is the glottis
- posterior cricoarytenoid muscles (abduction), lateral cricoarytenoid muscles (adduction), air ruches up from lungs folds vibrate to produce sound
how is voice produced
- adduction (closed)
- air exhaled upwards, blows them apart, folds = rapid vibratory pattern
- phonation: vibration of vocal folds, provides sound source (loudness = pressure, pitch = tension)
- resonation: modification of voice, chambers of pharynx, oral / nasal / sinus cavities = amplify / enhance quality
- enunciation: shaping / articulation of sound into language by muscles of pharynx, tongue, and lips
what is the trachea
- windpipe, from larynx to T5, 12cm, 2.5 diameter, anterior to oesophagus
- tubular passage for air
- mucosa: pseudo stratified ciliated columnar epithelium with goblet cells at luminal surface, basal cells, contain cilia
- submucosa: connective tissue , elastic / reticular fibres, seromucous glands
- hyaline cartilage: 16-20 incomplete rings (semi rigid support), posteriorly attach to oesophagus via fibromuscular membrane (trachealis muscle and elastic connective tissue)
- adventitia: outermost layer, connective tissue, encases hyaline cartilage
what is the bronchi
- air passages, 23 orders of branching (bronchial respiratory tree), conducting / respiratory zones
- primary: at T5 divides into right (vertical, shorter, wider, contain incomplete rings of cartilage) and left primary bronchus
- secondary / lobar: 2 in left lung, 3 in right lung (supply lobes of the lungs)
- tertiary / segmental:
- bronchioles
- terminal bronchioles (end of conducting zone, beginning of respiratory zone)
- respiratory zone: respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli
describe histological changes in the different sections of the bronchi
- 1-3: pseudo stratified ciliated columnar epithelium, protection, more than one layer, cilia
- larger bronchioles: simple ciliated columnar epithelium (some goblet / Clara cells)
- smaller bronchioles: simple ciliated cuboidal epithelium (no goblet cells)
- terminal: simple non-ciliated cuboidal epithelium, gas exchange, thin layer of cells
describe structural changes in the different sections of bronchi
- cartilage plates gradually replace rings of cartilage in primary bronchi, disappear in distal bronchioles
- smooth muscle: replaces cartilage, no cartilage = muscle spasms close airways (asthma, allergic reactions)
- ANS: sympathetic (epinephrine = relaxation / dilation) and parasympathetic (norepinephrine = contraction / constriction)
what are the lungs
- from diaphragm to upper margin of first rib (apex)
- mediastinum (separates lungs)
- base (concave, lies over convex diaphragm)
- costovertebral surface (matches rounded curvature of ribs)
- right: 3 lobes, separated by oblique / horizontal fissures
- left: 2 lobes (oblique fissure), 10% smaller, cardiac notch (medially)
- pleura: serous membrane,
- visceral (outer surface of lungs)
- parietal (inner of thoracic and mediastinum)
- intrapleural space: pleural cavity, thin liquid film, prevents separation of pleural sheets, lubrication, friction free movement
describe the conducting zone structures
- lobes are subdivided into bronchopulmonary segments
- segment: small bronchi, bronchioles, terminal bronchiole, respiratory bronchiole
- bronchopulmonary segments supplied by segmental bronchi
- 9 in left lung, 10 in right lung
- segments further divided into lobules (supplied by bronchioles)
what BV supply the lungs
- receive 2 sets of arteries
- pulmonary: carry deoxygenated blood through pulmonary parenchyma
- bronchial arteries: branch of aorta, perfuse the muscular walls of bronchi and bronchioles
what is the respiratory zone
- around 300 million alveoli
- most of lungs volume
- main site of gas exchange
- SA = 50-100 m2
what are alveoli
- cube shape structures surrounded by fine elastic fibres
- sac: 2 or more alveoli with a common opening
- pore: connect adjacent alveoli, allow air pressure throughout lung to be equalised
describe alveoli epithelium
- type 1: simple squamous epithelial cells, continuous lining along walls
- type 2: simple scattered rounded / cuboidal cells, contain microvilli, secrete surfactant and antimicrobial proteins
- surfactant: mixture of phospholipids and lipoproteins (reduces tendency of alveolar wall to collapse, lower tension)
- alveolar macrophages: dust cells, remove cellular debris, keep surfaces sterile
what is the respiratory membrane
- exchange of O2 and CO2 between air spaces in lungs and blood
- 0.5 um thick, air-blood barrier to allow rapid diffusion of gases
- alveolar / capillary walls fused basement membranes (four layers)
1. type 1, type 2, alveolar cells / macrophages (alveolar wall)
2. epithelial basement membrane
3. capillary basement membrane
4. capillary endothelium
what is pulmonary ventilation (external and internal)
- inspiration and expiration of air
- air flows to lungs by pressure (P) differences between atmosphere and alveoli
- external pulmonary: exchange of gases between air and blood
- internal: exchange of gases between systemic capillaries and cells
what are the gas laws
- pressure: of a gas is defined as the force that the gas exerts on the walls of its container
- airflow: driven by pressure gradient
- movement: air moves from regions of higher pressure to lower pressure
what is boyles law
- P and V of gas in closed container are inversely proportional when T is held constant
- V change = P change
- P change = gases flow to equalise pressure (ventilation)
what is atmospheric pressure
- force per unit of area exerted against a surface by the weight of the air above the surface
- reference pressure
- Patm (760mmHg)
what is intrapulmonary pressure
- intra-alveolar P: Palv/Ppul, pressure in alveoli, 760 mmHg, fluctuates with breathing, equalises with Patm
- intra-pleural P: Pip, pressure in pleural cavity, always negative in comparison 754-6mmHg, two inward forces promote lung collapse / elastic recoil / decrease SA, hence one outward enlarges lungs
what are the relationships between the different pressures
- Palv and Pip = transpulmonary pressure, keeps airways open, increased pressure = larger lungs
- pneumothorax if Pip > Palv, lungs collapse, following trauma
what are respiratory muscles
diaphragm:
- most important, dome shaped, skeletal muscle, partition between thoracic / abdominal
- innervated by phrenic nerve
- 3 holes: inferior vena cava, oesophagus, aorta
- contraction: enlarge T cavity diameter and V, 75% airflow entering lungs during normal breathing
- pregnancy / obesity (prevent diaphragmatic flattening)
external IC:
- superficial, elevate ribs
- increase T cavity V, 25% air entering lungs
what are accessory muscles of inspiration / expiration
- minimum contribution, deep, forceful movement
- sternocleidomastoid: elevates sternum
- scalene: elevates first 2 ribs
- pectoralis minor: elevates 3-5 ribs
- internal IC: deeper, pulls ribs inferiorly, forced expiration, increase P in A / T cavities
- external / internal oblique, transversus / rectus abdominus (downward rib movement, increase intra-abdominal P)
describe process of inspiration (active)
- inspiratory muscles contract (diaphragm descends, external intercostals contract - rib cage rises)
- thoracic cavity V increases
- lungs are stretched (intrapulmonary V increases)
- intrapulmonary P drops, boyle’s law, lower than atmospheric P (758 mmHg)
- air (gases) flows into lungs down its P gradient until intrapulmonary P is equal to atmospheric P
describe process of expiration (passive)
- inspiratory muscles relax (diaphragm rises, external intercostals relax - rib cage descends due to elastic recoil of costal cartilage)
- thoracic cavity V decreases
- elastic recoil of lungs; intrapulmonary V decreases
- intrapulmonary P rises (762 mmHg), greater than the atmospheric P
- air flows out of the lungs down its P gradient until intra-pulmonary P is equal to atmospheric P
- forced expiration is an active process (abdominal / internal IC)
overview of inspiration / expiration and changes in pressure / volume
- inspiration: P inside lungs decrease, V increases, pleural cavity P = more negative = chest wall expands 0.5 L air movement
- expiration: P inside lungs increase, V decrease, pleural cavity P = less negative = chest wall retracts 0.5 L air movement
how does airway resistance influence pulmonary ventilation
- friction in the air passageways causes resistance
- decreases air passage, causes breathing movements to become more strenuous
- greatest resistance to air flow occurs in the midsize bronchi.
- smooth muscle: walls of airways, ANS, relaxation / dilation = inspiration vice versa
- COPD: chronic obstructive pulmonary disease / asthma, continuous contraction, decrease diameter, closing of airways continuously
how does alveolar surface tension influence pulmonary ventilation
- molecules of fluid lining alveoli are attracted to each
- produces surface tension that constantly draws the alveoli to their smallest possible dimension
- surfactant: type 2, reduce alveolar surface tension, reduce inward force
- deficiency of surfactant: collapse of alveoli after expiration, difficulty filling lungs with air
how does lung compliance influence pulmonary ventilation
- compliance: measure of lungs capacity to expand V as result of a change in pulmonary P
- high: easily expand
- low: resistance to expand
- pulmonary fibrosis: low, elastic replaced by collagen, lose ability to inflate during inspiration
- emphysema: high, elastin = degraded, destruction of lung tissue, easily inflate, reduce capacity to recoil (forced expiration)
what diseases are caused by decreased lung compliance
pulmonary fibrosis: scarring and thickening of tissue around alveoli
- shortness of breath, dry cough, fatigue, weight loss
- chest x-ray, CT, pulmonary function testing, bronchoscopy / biopsy
- treated: corticosteroid, oxygen therapy, rehabilitation
tuberculosis: caused by mycobacterium tuberculosis, - large lesions leading to tissue death, healing by fibrosis / scaring - cough, fever, weight loss, night sweats, tiredness, loss of appetite, blood stained sputum
- chest x-ray, sputum sample
- treatment: antibiotics to obtain eradication of bacteria (6 months)
what disease is caused by increased lung compliance
emphysema: rupture of inner wall of alveolar sacs
- 1 large air space instead of many little ones
- cough, wheezing, shortness of breath, difficulty to expire
- chest x-ray, CT, pulmonary function testing
- treatment: bronchodilator, inhaled steroid, antibiotic, rehabilitation, oxygen therapy
describe the process of gas exchange (external respiration)
- oxygen diffuses from alveolar air (Po2 105mmHg high) into blood of pulmonary capillaries (Po2 40mmHg low)
- continues until Po2 of pulmonary capillaries matches Po2 of alveolar air
- CO2 diffuses from deoxygenated blood in pulmonary capillaries (Pco2 45mmHg high) to alveolar air (Pco2 40mmHg)
- continues until Pco2 blood reaches 40mmHg
how is gas / CO2 transported in the blood
- gases transported as liquid, dissolves in proportion to its partial pressure
- more CO2 dissolved in blood than O2 because CO2 is 24x more soluble than O2
- air we breath is mostly N2, very little dissolves = very low solubility
- CO2 never free
- combined to form carbonic acid or carbonate
how is oxygen transported in blood
- 1.5% plasma and 98.5% bound to haemoglobin (Hb) in RBC (oxyhaemoglobin)
- heme portion = 4 iron atoms = 4 O2 atoms
- higher Po2 = more O2 combines with Hb
what is the oxygen haemoglobin dissociation curve
- relationship between partial pressure of O2 and percent saturation of Hb and Po2
- depends on: Po2 and affinity between O2 and Hb
- high Po2 in lungs: loading portion of O2-Hb curve
- low Po2 in tissue: unloading portion of O2-Hb curve (75% saturated)
- Po2 > 60: almost flat, little change in saturation
- Po2 < 60: very steep small changes greatly reduce O2 in Hb
how does the respiratory system react to exercise
- recruiting reserve capacity
- rest 5 L min, small cardiac output 2/3 physiological dead space
- exercise: >15 L min, more capillaries conduct blood, increase cardiac output, no reserve, no physiological dead space
what is cystic fibrosis
- genetic disorder, epithelial transport of Cl in membrane of cells
- mucous secreted in airways, closure of airways, multi organ failure, infection of lungs, malnutrition
what are the effects of smoking
- arteriosclerosis: deposition of fatty plaques on inner wall of arteries
- COPD
- emphysema (enlarged alveolar sacs)
- chronic bronchitis (swollen passages, increase mucous)
- pathophysiological changes: increase neutrophils, chronic inflammation
what controls the respiratory system
- respiratory muscles: brain stem, reticular formation of medulla oblongata and pons
- pneumotaxic area: inhibitory impulses to DRG (limit inspiration)
- apneustic area: stimulatory impulses to DRG (prolong inspiration)
- inspiratory area: dorsal respiratory group (DRG), basic rhythm, excitatory impulses to diaphragm (phrenic), and intercostals (intercostal)
- expiratory area: ventral respiratory group (VRG), inspiratory / excitatory neurons, forceful breathing, excite accessory muscles
what chemical factors influence the respiratory system
- C chemoreceptors: ventrolateral area of medulla (H+ and CO2)
- P chemoreceptors: aortic and carotid bodies (H, CO2 and O2)
- stimulate change in respiratory muscles, change in CO2 and O2
what higher brain centres influence the respiratory system
- cortical controls: defensive mechanism, allows to hold breath during toxic environment, water, smoke, fumes
- hypothalamus: limbic system (influence of emotional stimuli / hyperventilation, pain anxiety)
- body temp: rise acts to increase rate (loss of heat)
