Respiration=◦ Movement of air in and out of lungs◦ Appropriate rate

Tachypnea-increased rate Apnea-no breaths

◦ Sufficient volume to meet needs

Thorax-pressure is negative vs. Atmospheric pressure◦ Partial vacuum within thorax◦ Pulls lungs up against thoracic wall

Pleural fluid-between lungs and thoracic wall◦ Provides lubrication

***Lungs passively follow the thoracic wall!!

Cardiovascular effect◦ Large veins-no pump to push blood back to heart◦ Negative pressure helps draw blood back from

veins into heart (atria-receiving chamber)

Drawing air into lungs Enlarge thoracic cavity

◦ Diaphragm contraction-flattens the “dome”◦ External intercostal muscle contractions

Where thorax goes, lungs follow! Pressure within lungs lowers

◦ Air enters airways

Pushing air out of the lungs Thoracic cavity decreases in size-

increased pressure◦ Diaphragm relaxes-dome shape returns◦ Internal intercostal mm. contract◦ Abdominal mm. contract-push organs up

against diaphragm◦ Requires little work to exhale

Except with rapid shallow breaths

Quantity of air moved Tidal Volume= volume of air inspired and

expired in one breath Minute Volume= volume of air inspired and

expired in one minute Residual Volume= volume of air left in lungs

after maximum expiration

Tidal Volume= 10-15 ml/kg◦ 10 kg dog=10ml/kg X 10 kg=100-200 ml/breath

Minute Volume= TV X RR◦ If RR = 12◦ Minute Volume

= 100 ml/breath X 12 breaths/minute =1200 ml -2400ml in a minute

Exchange method-Simple Diffusion!!! Concentration gradient-difference between

concentrations of given substance on either side of barrier

Oxygen binds to hemoglobin on the heme unit.

1 hemoglobin can carry 4 oxygen particles

Binds vs. Releases based on oxygen concentration in location it is in.

Regulate gas diffusion =Total pressure of a mixture of gases is the

sum of the pressures of each individual gas.◦ Atmospheric pressure-760 mmHg◦ Atmospheric oxygen = 21%◦ Po2=760mmHg X 0.21=159.6 mm Hg

Partial pressures-valid for gaseous and dissolved gas states

PO2 and PCO2 of alveolar capillary blood is determined by PO2 and PCO2 of alveolar air

PO2 (alveolar air)=100 mmHg PO2 (alveolar capillary)=40 mmHg So which way will O2 diffuse??

PCO2 (capillary blood)=46 mmHg PCO2 (alveolar air)=40 mmHg So which way will CO2 diffuse??

Both lungs and cardiovascular system need to work for proper oxygenation of tissues◦ Ventilation (V)-lungs◦ Perfusion (Q)-cardiovascular◦ V/Q mismatch-disruption of either

Tissues suffer

Skeletal muscle-voluntary control But…. Breathing does not need to be a

conscious effort!! Respiratory Center in medulla oblongata

(brain stem)-Carbon Dioxide levels!

Sheep brain

Controls inspiration, expiration and holding breath

Subconscious level Nerves to respiratory muscles Conscious control-overrides

◦ Only for a short time!!!

Stretch receptors in lung◦ Reaches stretch set point during inspiration

Signal sent to respiratory center Stop inspiratory muscles, start expiratory muscles

◦ Reaches deflate set point during expiration

Chemical monitors in blood (Carotid and Aortic Bodies) and Brain stem◦ CO2 content◦ pH◦ O2 content of arterial blood

Any variation of these three parameters◦ Respiratory pattern will be altered

If CO2 rises, pH falls◦ Blood is more acidic◦ Trigger respiratory center

Increase respiratory rate Increase respiratory depth

If CO2 drops, pH rises◦ What do you expect to see??◦ When can this occur??

Low O2 in blood (hypoxia)◦ Triggers Respiratory center

Increase rate and depth of breathing Severe hypoxia

◦ Neurons in respiratory center weaken Can cause decreased or cessation of breathing

Due to extremely high metabolic rate, respiratory tract must be highly specialized to quickly and efficiently deliver Oxygen and remove CO2

Choanae-internal nares that opens from the nasal cavity onto the roof of the mouth

Larynx structures surrounding the glottis (opening into the trachea)◦ No vocal folds!!

Syrinx-Enlargement of the trachea above the sternum◦ Voice box of the bird◦ Number of muscle>>complex vocalization

Songbirds-7 pair Parrots-3 pair Ostrich, strokes, vultures-no pairs of muscles

Trachea branches into bronchi Bronchi enter the lungs, lose cartilaginous

protection>>Mesobronchi Mesobronchi branch into 4-6

ventrobronchi>>parabronchi Parabronchi connect to air capillaries for

gas exchange

Air Sacs◦ Paired air sacs

Cranial Thoracic Caudal Thoracic Cervical Abdominal

◦ Unpaired air sac Interclavicular air sac

Air Sac function◦ Reservoir for air◦ Warmth and moisture to improve diffusion of air

through lung capillaries◦ Thermoregulation-internal evaporation of

water>> cools◦ Buoyancy

Lungs◦ Very small◦ Attached to thoracic vertebrae and ribs◦ Highly vascular◦ Inelastic◦ House air and blood capillaries for gas exchange

First inhalation-expand thoracoabdominal space-creating a pressure gradient◦ Air moves into posterior air sacs to warm and

humidify First Expiration-air is pushed into the lungs

for gas exchange

Second Inspiration-◦ Air moves out of lungs into the anterior parts of

the air sacs Second Expiration-

◦ Air leaves the body via trachea No mixing of inspired and expired air!!

◦ 21% oxygen

Demo

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