Week 3 Respiratory Flashcards
What is the cardiac notch?
The only place where the lungs don’t separate the ribcage from the heart- at about the 3rd-5th intercostal space
Where is the lung base?
Diaphragmatic surface
Where are the lungs apexes?
Adjacent to thoracic inlet
What is the root composed of?
Grouped principal bronchus, pulmonary artery, veins, and nerves wrapped together in pleural covering, location of tracheobronchial lymph nodes, enters at the hilus
How many lobes does a dog have?
2 left; 4 right
How many lobes does a horse have?
2 left; 3 right
How are the lungs subdivided into lobules?
Bronchopulmonary segments- by connective tissue septa
Connective tissue septa contain what?
Collagen, elastin, blood vessels
What species have what consistency connective tissue septa (implications for spread of infection)?
thick in ruminants and pig
thin and incomplete in horse
almost non-existent in dog
How many lobes in the right lung? Larger or smaller than left lung?
3-4 lobes; larger
Who does not have a middle lobe?
Horse
What is the cranial lobe ventilated by in ruminants and pigs?
Tracheal bronchus
How do the pulmonary arteries travel?
oxygen depleted blood from RV–> pulmonary trunk–> left and right pulmonary arteries–> lungs (Follow bronchi down to the level of the alveoli)
What do the pulmonary veins follow?
Oxygen rich blood from the lungs–> Left atrium. Follow bronchi and also provide venous return from bronchi
What is the bronchial artery?
Arises from the aorta to supply bronchi and connective tissue (i.e. tissues not participating in gas exchange)
What are the two networks of lymphatic vessels in the lungs?
Superficial network- drains subpleural tissue into vessels at hilus of lung; deep network- drains deeper tissues via vessels running along airways (from level of bronchioles)
Where do the two networks of lymphatic vessels merge?
At the hilus; tracheobronchial lymph nodes–> cranial mediastinal nodes–> tracheal lymphatic vessels or thoracic duct
What are the lymphatics responsible for?
Removal of material phagocytosed by macrophages in airways; mounting immune response to infectious agents
Efferent innervation?
Regulates activity of bronchial glands
Smooth muscle of bronchi
Afferent innervation?
Stretch receptors- reflex modification of respiration
Mechanoreceptors– reflex coughing
Where are the alveoli?
Scattered in walls of respiratory bronchioles. Continuous in walls of alveolar ducts
What do alveolar ducts lead to?
Terminal alveolar sacs
What are type I alveolar epithelial cells?
Very flattened, cover majority of alveolar wall, sit on basement membrane, terminally differentiated (cannot divide), allow gas diffusion across cytoplasm
What are type II alveolar epithelial cells?
Cuboidal, cytoplasmic granules contain surfactant (coat alveolar and reduce surface tension), divide to replace type I and type II cells, also contain some macrophages
What are alveoli separated by?
Interalveolar septa: fibroblasts, mast cells, macrophages, rich in capillaries (endothelial cells, endothelial basement membrane)
What are alveolar pores?
Holes in septa that allow passage of air between alveoli
What is the blood air barrier?
Between the air and the blood plasma, oxygen must diffuse across:
* alveolar fluid
* alveolar epithelial cell
* basement membrane of alveolar epithelium (+/- thin interstitium)
* basement membrane of capillary endothelium
* capillary endothelial cell
barrier 0.2-2 microns thick
once in plasma, oxygen is taken up by the erythrocyte, then binds to haemoglobin
Where are pulmonary macrophages present (3)?
**Intravascular- associated with endothelium (pig, ruminants), ** interstitial, **alveolar- function to clear alveolar surface; removed via trachea (mucociliary clearance, coughing) or via interstitium–> lymphatic system
What is the most common cell in a healthy lung?
Macrophage
What is the interlobular septa made of?
Collagen and elastic fibres, blood vessels
What is pleura made of?
Squamous/ cuboidal epithelium overlying elastic and collagen fibres and capillaries
How do you find partial pressure?
If O2 is 20% of a gas mixture with a total pressure of 760 mm Hg: 0.20 x 760 = 152 mm Hg
What is water vapors possible partial pressure?
47 mm Hg
What is the average PO2 of alveolar air?
100 mm Hg
What is the average PCO2 of alveolar air?
40 mm Hg
When O2 is bound to haemoglobin, does it contribute to PO2 in blood?
No
What reaction does CO2 dissolved in blood undergo?
CO2+H2O H2CO3 H+ + HCO3- (lowered PCO2 in the blood)
What is PO2 in venous blood, alveolar air, arterial blood, and tissues?
40 (venous blood), 100, 100, 40 (tissues)
What is PCO2 in venous blood, alveolar air, arterial blood, tissues?
46 (venous blood), 40, 40, 46 (tissues)
How does gas exchange occur in alveoli and tissues?
Gas exchange in alveoli and tissues involves passive diffusion down partial pressure gradients
What is the Rate of gas diffusion through the tissues (DR)?
DR = (PD x A x DC)/T PD= partial pressure gradient across tissue barrier A= surface area available for diffusion DC= diffusion coefficient (related to solubility of specific gas in tissue) T= thickness of tissue barrier
When is surface area increased and reduced?
SA is increased during exercise and reduced during disease (e.g. emphysema)
When is barrier thickness increased?
During disease- pulmonary oedema (e.g. left- sided heart failure)
Pulmonary fibrosis
Pneumonia
What is the rate of blood flow in the alveolar bed?
Gas transfer in alveolar capillary bed happens in about 1/3 of the time it takes for blood to travel past alveolus–> existence of enormous diffusion reserve ???
During exercise what happens to blow flow?
Rate of flow increases– there is your need for the diffusion reserve; if diffusion reserve is exhausted–> hypoxaemia without hypercapnia
What are gills?
Delicate evaginations of tissue protruding into surrounding water; consist of thin epidermis highly perfused by circulatory system, providing high surface area for gas exchange between water and blood; breathing involves taking water into mouth while operculum (gill cover) is shut; the mouth is then shut and operculum opened thus forcing water over gills and through operculum; unidirectional system