vet systems unit 3

what makes up the upper airways?

nares, nasal cavity, pharynx

what makes up the lower airways?

larynx, trachea, bronchial tree, lungs

other components of pulmonary system?

diaphragm, visceral and parietal pleura, pleural space

avian pulmonary system

have anterior and posterior sacs for unidirectional flow through lungs, this enhances exchange efficiency and allows them to fly over extreme altitudes

reptile pulmonary varieties

similar to mammals (crocodiles), use muscles of chest wall (snakes, lizards), or buccal pumping (some lizards)

amphibian pulmonary system

have simple lungs as secondary but depend primarily on skin for gas exchange, larval stages utilize gills and skin

horses pulmonary differences

obligate nasal breathers due to position of epiglottis

elephant pulmonary differences

no pleural space, have connective tissue that will allow them to snorkel with trunk

dolphin pulmonary differences

have collapsible lungs to extract oxygen more efficiently and prevent the bends

layers of respiratory system

tunica mucosa, tunica submucosa, tunica adventitia/serosa

tunica mucosa

innermost layer, has epithelium, lamina propria, and muscularis mucosa

lamina propria

loose connective tissue of the mucosa

muscularis mucosa

thin layer of smooth muscle that defines end of mucosa

tunica submucosa

connective tissue layer, may have glands and other inclusions

tunica adventitia/serosa

outermost layer of connective tissue, adventitia will blend into other organs’ connective tissue, serosa will be bounded by serous membrane

upper airway microanatomy

mucosa may not always have muscularis mucosa, submucosa will often have submucosal/mucus glands, will have adventitia that often has bone in nasal cavity

respiratory epithelium

usually pseudostratified columnar with cilia and goblet cells

olfactory epithelium

line nasal conchae, specialized for sensing odors, has Bowman’s glands below epithelium

Bowman’s/olfactory glands

produce mucus to remove old odors and refresh the system

larynx/voice box

cartilage that houses true and false vocal folds

false vocal fold

similar to other portions with respiratory epithelium and mixed glands

true vocal fold

muscular fold covered by stratified squamous non-keratinized epithelium

trachea

tunica mucosa may have muscularis mucosa, submucosa often has submucosal/seromucus glands, adventitia will have C-shaped cartilage rings

C-shaped cartilage rings

prevents trachea from collapsing with inhalation, trachealis muscle closes rings

diffuse neuroendocrine cells in tracheal epithelium

monitor environment and secrete products like serotonin, misregulation can contribute to asthma

why are the cartilage rings C shaped?

to accommodate for esophagus to expand

pleural cavity function

serous membrane is lubricated to minimize friction during respiration, cavity is slight negative pressure compared to lungs through specialized lymphatic drainage

spontaneous pneumothorax

air entering pleural cavity reducing negative pressure, usually caused by rupture of blebs/bullae on surface of lungs

dead space/conducting space

all volume that doesn’t have gas exchange

poiseulle’s law

resistance = ¼ radius

trachea to early bronchi have higher _

resistance

branching tree of bronchi for increased _, but smaller tubes increases _

surface area, resistance

bronchi

tunica mucosa has bronchial epithelium lamina propria and sometimes muscularis mucosa, submucosa has bronchial/seromucus glands, adventitia has cartilage plates instead of rings

bronchial epithelium

pesudostratified columnar with cilia and goblet cells, but shorter that respiratory epithelium and fewer goblet cells

bronchioles

tunica mucosa will have bronchiolar epithelium, club/clara cells, lamina propria, and muscularis mucosa, tunica submucosa will have no bronchial glands, and tunica adventitia has no cartilage

bronchiolar epithelium

simple columnar/cuboidal with cilia

club/clara cell

produce surfactant, break down mucus, and detoxify some substances (CYP450), act as stem cells

surfactant

reduces surface tension from water in lungs

why don’t bronchioles need cartilage?

less air velocity, have smooth muscle instead

progressing down respiratory tree

less cartilage, more smooth muscle, more clara cells, less goblet cells

respiratory bronchioles

first place for gas exchange, simple cuboidal epithelium, club cells, muscularis mucosa, and clear breaks in epithelium with connections to alveoli

alveolar ducts

where airway is almost completely covered by alveoli, smooth muscle will have knobs covered by a few cuboidal cells

alveolar sacs

dead ends of alveolar ducts, no smooth muscle knobs will have pointed septae, and no cuboidal epithelium

alveoli

blind end of respiratory tract where gas exchange occurs by diffusion across blood-air barrier (capillaries), will have type 1 pneumocytes, type 2 pneumocytes, alveolar macrophages, and endothelial cells

type 1 pneumocyte

squamous cells that form blood-air barrier with endothelial cells

stroma of blood-air barrier

made up of collagen and elastin, basement membrane of type 1 and endothelial cell

endothelial cell

squamous cells that line capillaries, form blood-air barrier with type-1 pneumocyte

blood-air barrier needs to be _ and _ for efficient diffusion

very large surface area, very thin

type 2 pneumocyte

cuboidal cell that secrete surfactant

feline asthma

over-reactive immune cells cause recruitment of more immune cells, increase mucus secretion and muscle contraction, will see bright branching pattern on radiograph that is inflammation of bronchi/bronchioles

main function of gas exchange

remove CO2 to maintain acid base balance

respiratory and transition zones

where gas exchange will occur

mucociliary tree

in dead zone, has cilia to move mucus

the mammalian lung will mix

inspired and alveolar gas, breathe in 1 L, lungs have 2-3 total Ls

lung lobules species differences

pigs and cattle lobules are not interconnected, cats and dogs there is profuse interconnectivity, horses are intermediate

lobule interconnection function

allow for collateral ventilation and lessen consequences of airway obstruction

type 1 alveolar cell

form thin projections, 90% of alveoli area

babies born before 34 weeks need

surfactant

alveolar macrophage will not eat

asbestos or silica

equilibration

pressure of gas in alveolar space and in blood leaving lungs is the same

ventilation

process where gas gets into alveoli, first process that enable O2 across blood-gas interface

not all gas will go into alveolar space,

1/3 will stay in dead space

transit time

ratio of pulmonary capillary volume/cardiac output, exercise will increase volume and greatly increase cardiac output which will decrease transit time

total lung capacity

max amount of how much air can be in lungs

vital capacity

distance between total lung capacity and functional residual capacity

tidal volume

average amount of air breathed in

functional residual capacity

at end of each breath, when no respiratory muscles are acting on lungs, great reference of lung volume

residual volume

minimum amount of air lungs wants to hold

VT =VA + VD

tidal volume= alveolar space + dead space

V’E=V’D+V’A

expired ventilation= dead space ventilation + alveolar ventilation

why is rapid shallow breathing less efficient?

too much air is wasted in dead space and not in alveolar space

bohr equation

VD/VT= PACO2-PECO2/PACO2, P difference b/n alveolar CO2 and expired CO2 over alveolar CO2, ratio of dead space to tidal volume,

alveolar ventilation during exercise

increases with volume of carbon dioxide to regulate mean expired carbon dioxide to keep arterial pH as close to 7.4 as possible

where is ventilation higher?

at base of lung, because tissue here is much more compliant and takes less force to stretch

dalton’s law of partial pressures

pressure exerted by a gas is proportional to total pressure multiplied by the fractional concentration of that gas

gases move across a membrane by _

pressure gradient

why does PO2/partial pressure decrease in alveoli

there is mixing with CO2 and O2 is removed at a greater rate than CO2

respiratory exchange ratio

ratio of flow of CO2 to flow of O2 uptake, VCO2/VO2, usually about .8

alveolar gas equation

PaO2 = PIO2 - (PaCO2/R), partial pressure of oxygen = partial pressure of inspired oxygen - (partial pressure of CO2/respiratory exchange ratio)

henry’s law

concentration of gas dissolved in a liquid is proportional to its partial pressure and solubility

the solubility of O2 is _, and the solubility of CO2 is _

very low at .003, and very high at .067

boyle’s law

P1V1=P2V2, helps us understand that as we inhale the negative pressure lowers the alveolar pressure past the atmospheric pressure, driving air into lungs to balance pressure, and the opposite for expiration

fick’s law

volume of gas that diffuses across a membrane per time is determined by V’gas=A/T x D(P1-P2), or area/thickness x diffusion constant (partial pressure on first side - partial pressure on second side)

how is diffusion constant determined?

solubility/ square root molecular weight

alveolar gas PO2 is _, and pulmonary capillary PO2 is _, what does this mean?

100, 40, O2 will flow rapidly down this pressure gradient

diffusion limitation

diseased lungs may take longer for equilibration or it may not happen at all causing blood leaving lung to have a lower O2 than alveolar gas

female humans, greyhound, and horses all experience what with diffusion?

the red blood cells are in the pulmonary capillary for a super short time because the cardiac output is so high, resulting in hypoxemic blood

Within a healthy lung, how long does it take for the capillary blood to equilibrate with the alveolar gas?

.25 s

What are the pressures of O2 and CO2 in the arterial blood, the venous blood, and the alveolar space?

PO2 100 mmHg and PCO2 40 mmHg, PO2 40 mmHg and PCO2 46 mmHg, PO2 100 mmHg and PCO2 40 mmHg

why is pulmonary artery pressure so low?

the blood gas barrier is very fragile

transmural pressure

difference between capillary lumen pressure and alveolar pressure

pressures are_ at rest

pulsatile, but not in capillaries, this increases with exercise

how is vascular resistance affected by lung volume?

with inhalation, volume of pulmonary capillaries are increased and resistance is lowered, with exhalation it will compress capillaries and increase resistance

why don’t we breathe at total lung capacity all the time?

it would overload the right ventricle and cause right heart failure and stiffen the lungs

how do the lung apex and base perfusion compare?

apex has low perfusion pressure and base has high perfusion pressure, this is due to gravity

pulmonary hypoxic vasoconstriction

blood flow past a messed up part/hypoxic region will decrease, but will cause right heart failure and brisket disease because pressure increases in artery

what animals are most affected by hypoxic pulmonary vasoconstriction at altitude?

pigs and cattle

blood flow in equine lung

dorsal surface gets more blood flow because arterioles here have higher sensitivity to vasodilation with exercise

why is PO2 higher as we move up lung?

because the V/Q ratio is higher

pulmonary edema

waterlogged lung, will have thickened blood gas barrier