CVRS - Respiratory Flashcards by Alice Harsant

What are the functions of the lungs?

Respiratory - exchange of gases
Non-respiratory
-Pulmonary endothelium secretes ACE
-Acid base balance
- Immune regulation
-Thermoregulation
-Metabolism of phasoactive metabolites

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What are the pulmonary volumes?

Tidal volume - amount of air moved in each breath
Inspiratory reserve volume - amount of air that can be inhaled with max effort after normal breath has been inhaled
Inspiration capacity is both these combined

Expiratory reserve volume - amount of air exhaled with max effort after normal breath has been exhaled

Vital capacity is the inspiration capacity plus expiratory reserve volume.

Residual volume is amount of air left in lungs after forceful exhalation.
(functional residual capacity is the normal amount left with normal breath)

Total lung capacity is all of this added

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Species variation of the left lung

All domestic animals have 2 lobed left lungs:
Cranial - this itself is also divided cranially and caudally
Caudal

The horse looks like one lobe but is two

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Species variation in the right lung

4 lobes
Cranial
Caudal
Middle
Accessory (sits under heart in ventral midline between caudal lobes in own pleura)

Horses hard to see
Ruminants look like 5 lobes but two cranial lobes have same lobar bronchus
Pigs and ruminants the cranial lobe is supplied by tracheal bronchus

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What does the diaphragm do and what is it made of?

Made of skeletal tissue and tendons

It contracts, pulling ribcase and changes pressure in thorx.

Supplied by phrenic nerve

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What are the pleural membranes?

Visceral pleura

Parietal pleura

Mediastinal

Plica venae cavae

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What are pleural membranes made of?

Simple squamous epithelium surrounded by connective tissues derived from somatic mesoderm.

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What are the three layers of parietal pleura?

Lines pleural cavity and is thicker. Split into three

Costal pleura - lines ribcage
Mediastinal pleura - lines mediastinal,
Diaphragmatic pleura - lines cranial surface of diaphragm

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What is the visceral pleura?

outer surface of lung continuous with parietal with lots of elastic fibres

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What is the mediastinal space?

The space in the cavity between the lungs is formed by apposition of the mediastinal pleura of right and left sacs.

Contains most of thoracic cavity (heart, thrachea/oesophagus, mediastinal, great vessesl and nerves)

A fold of the parietal pleura is the pilca venae cavae and contains lungs, caudal vena cava and right phrenic nerve.

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What does the upper respiratory tract consist of?

Pharynx and larynx

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Describe the pharynx

Common cavity where air and ingested material pass. It connects the oral cavity with the oesophagus and the nasal cavity with the larynx

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Where is the pharynx located?

Dorsally - bordered by base of skull and two cranial vertebrae

Ventrally - larynx and mandible

Laterally - pterygoid muscles and suspensory part of hyoid apparatus

Soft palate separates rostral part of pharynx to dorsal and ventral part of naso-/oro-pharynx

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What is the larynx?

Its a bilaterally symmetrical tube-shaped musculocartilagenous organ connecting pharynx to trachea

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What does the larynx do?

It protects the trachea from foreign material entering when swallowing

Important in vocalisation and increasing intra-abdominal pressure

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What are the cartilages of larynx?

Unpaired: thyroid, cricoid and epiglottis
Paired: arytenoids, corniculate and cuneiform

What is the cause of roaring?

The caudal recurrent laryngeal nerve is paralysed, this means the dorsal cricoarytenoid muscle can no longer abduct the arytenoid cartilage and creates a roaring noise

What makes up the lower respiratory zone?

Conductive zone - trachea to terminal bronchioles (to the hilus)
Non-conductive/transitional zone - respiratory bronchioles to alvolar sacs (to the acnius)

What is the trachea in the conductive zone?

A c-shaped ring held together by broncheal smooth muscle.

The lumen is lined with pseudostratified columnal epithelial (PCE) cells and the goblet cells, which secrete mucus.

The mucus is to trap foreign material (mucosal escalator)

What is the bronchus in the conductive zone?

These are also made of PCE and goblet cells. The longside has some cartilage, so less organised looking than trachea.

What is the bronchioles of the conductive zone?

Made of cuboidal and clara cells (non-ciliated epithelial cells).

These secrete surfacatant to make it structurally sound.

Some smooth muscle to ensure even spread.

Terminal bronchioles have a bit of cartilage to support lymph nodes and little blood supply

What are the bronchioles of the conductive zone?

These are respiratory, and do not have cartilage.

What is the alveolar duct of the transitional zone?

Openings to the alveolar are guarded by knobs of smooth muscle, allowing redistribution of gas when closing a duct

What is the alveolus of the transitional zone?

Minute pologona chambers, which change shape with breath. They are interconnected for support and prevent atelectasis (collapsing). There are pores of Kohn (gaps) to allow movement.

Made of squamous epithelial cells .

Type I - gas exchange
Type II - secrete surfacant to minimise surface tension

What is the alveolar/blood-gas barrier?

The network of capillaries anastomose between the alveolar epithelial. These share a basement membrane, reducing the distance for O2 to travel. There are thicker walls of elastic fibres to allow structural integrity

What is compliance?

A measure of lung expandability and how much change in volume is required to get a change in pressure. If a small change in pressure leads to a high change in the volume of lungs there is a high level of compliance.

What increases lung compliance?

Surfactant makes it easier for lungs to expand and reducing energy required. It is produced by type II alveolar.

What is infant respiratory distress syndrome?

A lack of surfactant leads to stiff lungs and alveolar collapse.

What happens during inspiration?

1. Diaphragm contracts and flattens via phrenic nerve. This enlarges the throacic cavity. 2. Ribs move out and the parietal pleura pulls the visceral pleura and lung outwards. Lowering the pressure in the thorax 3. Air enters the lung

What happens during expiration?

1. Diaphragm relaxes, reducing volume aided by internal intercostal muscles. 2. Lungs recoil, expelling air

Whats different about horses breathing?

Horses expiration is biphasic. Its passive then active due to abdominal muscle contraction. Induced pulmonary haemorrhage can occur in racehorses where small vessels in the lungs burst.

What is the bronchial blood circulation?

The blood supply to the bronchials themselves. Bronchial and azygous veins are branches off the aorta. It is low volume, high blood pressure.

What is the pulmonary circulation?

A large volume system with low pressure input from the pulmonary trunk carrying venous blood from the right side of the heart to the lungs.

What is the right to left shunt?

The two circulatory systems (pulmonary and bronchial) are anastomosed. This means a small shunt from deoxygentated blood from bronchial can join pulmonary back to the left ventricle. Only significant in large numbers

What happens in times of low oxygen?

Hypoxic vasoconstriction restricts the amount of O2 via the pulmonary artery. This means the areas with high O2 is getting the best bloody supply

What is Ficks law?

The rate of transfer of gas through an area is proportional to the area and difference in partial pressure between the two sides. This is affected by: -Thickness of surface -Area of surface -PO2 difference -Pulmonary oedema Also affected by adequate ventilation (affected by hypoxia and atelectasis)

How does O2 gas exchange occur?

Oxygen binds to haemoglobin loosely and reversibly to heme portions of haemoglobin. In high areas of O2, it binds and released in lower areas

What affects saturation curve of O2?

Exercise - shifts sigmoid curve to right, ensuring muscles get a lot of oxygen pH - shifts, alkaline moves left and acid moves right

How does CO2 and CO gas exchange occur?

CO2 7% is found in plasma and is very dissolvable here 23% is found transported with haemoglobin, binds to amine radicles 70% is moved around as bicarbonate (HCO-3). Taken up by red blood cells and carbonic anhydrase forming bicarb. Buffers blood. CO binds to Hb as well, and has a greater affinity so displaces both O2 and CO2