The Respiratory System Flashcards
respiratory controller
autonomic control
behavioural control
ability to monitor and respond
ventilatory pump
create negative intrathoracic pressure
distrubute gas
minimize energy expenditure
structures of the respiratory system
soft tissue and pleua bony thorax lung and conducting airways muscles of respiration peripheral nerves
function of lungs
Gaseous exchange surfactant production reservoir for blood filter part of the immune system pH balance- 7.42pH controled by exchange of co2 forming with water to form carbonic acid, deeper breathing increases pH
Thoracic cage
age related changes
sychronised unit
changes in diameter in different planes
upper airway
consist of
nostril-nasal cavity
mouth-pharynx
Positive of nose breathing
warms air moistens the air filters the air produce nitric oxide- natural broncho-dilator Laminar nasal airflow
Tracheostomy
bipass nasal cavity
Pleura
two layers of pleura visceral underneath and parietal
serous membranes lining the thorax
Pneumothorax
air in the plural space
Pulmonary airway tree
terminal bronchiole
respiratory brochioles (3 orders)
alveolar ducts
alveolar sacs
conducting zone
up to division 17 trachea to terminal bronchioles no gas exchange gas transport by convection anatomical dead space
Respiratory zone
from division 17
respiratory bronchioles to alveioli
gas exchange occues from alveioli to capillaries by diffusion
large surface area
Fick law
rate of diffusion is directly proportional to the surface `area of exchange surface and diffusion gradien
Pulmonary Circulation
low pressure system as heart is near lungs
pulmonary artery receive all the output from the right ventricle
bronchial circulation supplies all airways
Boyles law
when you increase the volume the pressure decreases
when you increase the pressure the volume decreases
Respiratory muscles
accessory muscles of inspiration
sternocleidmastoid
scalene
pectoralis minor
serratus anterior
respiratory muscles
accessory muscles of expiration
internal intercostal muscles transverse thoracic muscle external obliques rectus abdominals internal obliques
Primary respiratory muscles
Diaphragm
external intercostal muscles
inspiration
The respiratory centre in the medulla oblongata sends impulses to initiate inspiration, the muscles of inspiration are initiated and contract, Accessory muscles include sternocleidomastoid, scalene, pectorals minor, sertatus anterior. The diaphragm contracts and descends. The rib cage swings up and out, increasing the volume within the thorax. The intrapulmonary pressure starts to drop. The pleural pressure in the pleural space becomes more negative as the rib cage moves up and out. Intrapulmonary pressure becomes less than atmospheric pressure. Air is moved into the lungs down concentration gradient until equilibrium is reached and air movement stops.
expiration
The respiratory centre in the medulla oblongata stops initiating inspiration, respiratory muscles relax, diaphragm moves up as the ribcage moves down and in. the lungs recois due to the elastic recoil, intra pulmonary pressure rises, intrapleural pressure becomes less negative air moves down a concentration gradient until equilibrium is reached.
Normal pattern
rate rhythmic active inspiration unconscious voluntary control passive expiration ratio 1:2
properties of the respiratory system
compliance resistance elasticity dynamic compression work of breathing
Respiratory membrance
made up of 3 layers Squamous epithelial cells lining the alveoli, the pulmonary capillary endothelium and fused basal laminae that lie between the alveolar & endothelial cells.
Alveoli
tiny air sacs where the exchange takes place, with over 150 millions alveoli in the lungs with a spongy appearance composed of single squamosus epithlium, (1/2 a tennis court). They contain roaming macrophages, phagocytose antigens, Pneumocytes type II scattered amongst squamous cells, produce surfactant. With each alveolus there is an extensive capillary network surrounded with network of elastic ibres for elastic recoil during expiration.
Capillaries
The capillary walll’s are thinnest of all blood vessel, only one cells thick (thinner diffusion pathway- ficks law) for rapid diffusion. Three processes are essential for the transfer of oxygen from the outside air to the blood flowing through the lungs: ventilation, diffusion, and perfusion.
Primary Bronci
Respiratory bronchi are the main passageway to the lungs, with air coiming in through the nasal cavity or the mouth to the pharynx, through the trachea to bificateing into the right and left primary bronchi. The bronchi are made of C-shaped cartilage rings with the right bronchi is shorter and wider than the left,with subdivisions into the secondary bronchi to supply the 3 lobes of the right lung, the left lung has 2 subdivisions to supply the 2 lobes of the left lung.
Changes from bronci to bronciloles
The airway descends to the secondary, than tertitary than terminal brochioles. The secondary, tertiary and broncioles get smaller the closes they get to the lung tissue. The bronchioles have well developed muscular wall and are the most delicate branch of the bronci tree lined with a cuboid epithelian and scattered cilia with no mucous glands or cells and rings of cartilage replaced by plates of catilage in secondary brochi and nonexistent in bronchioles.
Exchange at the respiratory membrance
Residual CO2 from cell metabolism diffuses much more readily than O2. it is carried in the blood combined with Hb & is given up easily across the respiratory membrane into the alveoli & exhaled.
The gasses diffuse easily because:
Differences in partial pressure across the respiratory membrane are substantial – steeper gradient, faster diffusion
Distances involved in gas exchange are short
The gasses are lipid soluble so diffuse readily through surfactant layer, alveolar & endothelial plasma membranes
Total surface area of respiratory membrane is very large
Blood flow & air flow are co-ordinated & so efficient
Surfactant forms a thin oily layer over alveolar surface, coating a thin layer of water. Its interaction with the water molecules reduces surface tension & keeps the alveoli open. Reducing the effort of inspiration
Network of elastic fibres maintain position of alveoli & their recoil on exhalation reduces the size of the alveoli, helping push air out of the lungs
Pathological changes from increased thickness of repiratoy membrane
increases the diffusion distance (ficks law) impairs gas exchange decrease rate of diffusion. Eg CB, pneumonia, pulmonary oedema,
- Inflammation
- Oedema
- Surfactant
- Mucous retention
- Hyperplasia of alveoli wall
Pathological changes from decreased respiratory membrane
exchange surface area decreases (ficks law)
scar tissue
eg emphysema
Pathological changes from diffusion gradient
irflow limited in and out the lungs due to narrowed, blocked or compressed airways e.g. COPD including asthma, pneumonia
oxygenated blood needs to pass through respiratory membrane and replaces be deoxygenated blood to create a diffusion gradient, also insufficient Hb eg anaemia, haemorrhage.
exchange at alveoli
Oxygen in carried to the alveoli through the bronchi and is exchanges across the respiratory membrane made of the squamosus epithelial of the alveoli, the lamina fluid between the alveoli and the capillary, and the endothelium of the capillary. The partial pressure of oxygen in the alveoli is about 100mmHg whereas in the capillaries the partial pressure of oxygen is 20-40mmHg creating a diffusion gradient as a result oxygen moves from a where they are in high concentration to a region of low concentration and combined with haemoglobin in the red blood cells forming oxyhaemoglobin which is carried in the blood stream to respiring muscles.
Haemoglobin
4 polypeptide chains, 2 alpha and 2 beta polypeptide chains each with a heme molecule and an iron molecule which can bind reversibly with oxygen. 250 million Hb molecules found in a RBC.
Oxygen transport
Oxyhaemoglobin, each haemoglobin molecule contain 4 heme and 4 iron molecule and therefore has the ability to carry 4 oxygen molecules, this is responsible for carrying 98.5% of oxygen in blood, once one molecule of haemoglobin binds to haemoglobin the Hb affinity for oxygen increases and then picks ip oxygen more easily creating S shape of oxyhaemoglobin disassociation curve. When oxygen combines with Hb it releases a hydrogen ion. The remaining 1.5% is dissolved in plasma, controlling the saturation of Hb.
Carbon dioxide transport
5-10% carried in solution in the plasma. The remaining carbon dioxide enter the Hb molecule with 5-10% forming carbonimohaemoglobin bind to a different site to oxygen. The remaining 80-90% forms bicarbonate.
In this system, carbon dioxide diffuses into the red blood cells. The enzyme Carbonic anhydrase (CA) speeds the reaction by 13,000 times converts the carbon dioxide in red blood cells by binding with water into carbonic acid (H2CO3 ) Carbonic acid is an unstable, intermediate molecule that immediately dissociates into bicarbonate ions (HCO3-and hydrogen (H3O+ ions. Since carbon dioxide is quickly converted into bicarbonate ions.
2 H2O + CO2 H2CO3 + H2O H3O+ + HCO3-
exchange at metobalically active tissue
In respiring tissues, Partial pressure of oxygen is low and partial pressure of carbon dioxide is high, co2 therefore diffusing down a concentration gradient through the tissue to the capillary endothelium. 5-10% carried in solution in the plasma. The remaining carbon dioxide enter the Hb molecule with 5-10% forming carbonimohaemoglobin bind to a different site to oxygen. The remaining 80-90% forms bicarbonate. Oxygen from the plasma or bound to haemoglobin is released and diffuses from capillary membrane to respiring tissue picked up by myoglobin in muscle cells. into the mitochondria for aerobic respiration.
Nasal cavity
air enter the body via the nasal cavity as the main external opening made of cartilage, bone muscle and skin to support and protect the cavity. It’s a hallow space with the function to warm, moisturize and filter passing air, by hairs and mucous membrane that traps dust and contaminants. As air passes through the nasal cavity it also produces nitric oxide a natural bronco-dilator.
Phalanx and trachea
Once air has passed through the nasal cavity it reaches the phalanx which splits into the trachea and the oesophagus. Air passed down the wide hallowed trachea tube (12cm long. 2.5cm in diameter) which is of a thin membranous wall with C cartilage structures with narrow membranous regions in-between. The trachea epithelium is lined with cilia and plays a vital role in passive air flow as well as muscular wall allows powerful and productive cough upon contraction.
Primary Bronci
conducts air into the lungs. The bronchi are made of incomplerings of cartilage epithelium with the right bronchi shorter and wider than the left,with subdivisions into the secondary bronchi to supply the 3 lobes of the right lung, the left lung has 2 subdivisions to supply the 2 lobes of the left lung.
Secondary, tertiary and bronchioles
he secondary, tertiary and broncioles get smaller the closes they get to the lung tissue. The bronchioles have well developed muscular wall and are the most delicate branch of the bronci tree lined with a cuboid epithelian and scattered cilia with no mucous glands or cells and rings of cartilage replaced by plates of catilage in secondary brochi and nonexistent in bronchioles. `
respiratory bronchioles
terminate at alveolus, made of simple squampus cells diving into alveolar ducts, the alveolar ducts end in alceoli sac which are involved in gaseous exchange and secretion of alveolar fluid to keep alveoli moist.
