Janet Wild, Sept 2014

ASC171 Animal Anatomy and Physiology

The Respiratory System – Part 1

“She talks so that you can

barely hear her.

She talks on the exhale,

because she cannot talk on

the inhale which means

that her sentences are

interrupted 15 times each

minute, for the breathing

machine to make her

breathe, which makes

conversations with her

quite leisurely, long pauses

in the sentences, and

everyone learns to be

patient …” Lorenzo Milam, writing

about his sister, 1984

[The iron lung]

http://www.oobject.com/category/12-iron-lungs/ http://archive.wired.com/images/article/full/2007/10/iron_lung_630x.jpg

www.bagofnothing.com http://amhistory.si.edu/polio/howpolio/enlargeiron_01.htm

http://archive.wired.com/science/discoveries/news/2007/10/dayintech_1012 www.theatlantic.com

Learning Objectives

o Outline the functions of the respiratory tract.

o Describe the gross anatomy of the respiratory system.

o Outline the passage of air from the atmosphere to the alveoli.

o Relate respiratory tract anatomy to function.

o Outline the physiology of respiration including gas exchange, ventilation, O2 and CO2 transport in the blood.

o Describe the pressure changes within the thorax during respiration and explain their effect on gas movement.

o Describe different lung volumes and capacities and explain their significance.

o Describe how respiration is controlled

o Outline some pathological conditions of the respiratory system

o Relate basic mammalian respiration to adaptations in different animals (fish, birds, reptiles)

[Christopher Reeve] http://www.famouspeoplearehuman.com/index.php/famous-

people-with-quadriplegia/

http://images.rapgenius.com/c2cebae13d55ff3fff4fde1f49cbda

d1.1000x750x1.png

Why respiration?

Why does an animal need oxygen?

Why does it need to get rid of carbon dioxide?

The animal needs energy to live

It gets it by oxidising glucose to carbon dioxide and water.

The energy it stores as ATP (initially)

The oxygen it gets from the air via the respiratory system

cardiovascular system every cell

The carbon dioxide it gets rid of in the opposite direction

from every cell cardiovascular system respiratory

system

Background – introduction:

Overview of Respiration

Divided between external respiration (breathing or ventilation +

cardiovascular transport) and internal (cellular) respiration

1. External respiration = transporting O2 and CO2 to and

from the cells

Exchange of oxygen and carbon dioxide between

atmosphere and body tissues

2. Internal respiration = cell metabolism to use O2 and

produce CO2

Oxidative phosphorylation (remember your muscle lectures)

Occasionally anaerobic glycolysis (as in intensive muscular

exercise)

1. External Respiration

Pulmonary ventilation (process of

breathing)

Exchange between lungs and blood

Transport of O2 and CO2 in blood

Exchange of gases between blood

and body tissues

Copyright © 2011 Pearson Education, Inc., publishing as Benjamin Cummings.

2. Internal (Cellular) Respiration

We won’t talk much about

internal respiration in

these lectures.

You’ll cover it elsewhere

in your course – as in

your previous muscle

lectures.

Mitochondria in

cells use O2

The CO2 is waste

Back to external respiration …

Outline of the functions of the respiratory tract.

What does it do? Why is it needed?

o Gas exchange: every cell in the body needs oxygen to survive: O2 goes in (inspired), CO2 comes out (expired)

o pH control: regulation of acid-base balance of blood: CO2 is an acidic gas, so if it in the blood, then the blood becomes more acidic.

o Thermoregulation: e.g. panting in the dog. Dog has only a few sweat glands in the skin.

o Warms and humidifies air to protect lungs. Loses some water too.

o Filters air and can generate immune response: to protect lungs from infective agents

o Vocalisation and voice projection

o Sense of smell: detection of olfactory stimuli. Warning of dangers.

The gross anatomy of the respiratory system

The gross anatomy of the respiratory system (cont)

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Copyright © 2011 Pearson Education, Inc.

Nasal cavity

Oral cavity Pharynx

Epiglottis Larynx

Upper respiratory tract

Lower respiratory tract

Oesophagus

Left lung Right lung

Alveolar sac

Respiratory Bronchioles –

the earliest site at which

gas exchange occurs

Terminal

bronchiole

Terminal

bronchioles

Alveoli

Glottis

Trachea

Primary bronchi

Secondary bronchi

Tertiary bronchi

Diaphragm

Cartilage rings

The gross anatomy of the respiratory system (cont)

Lower

The gross anatomy of the respiratory system (cont)

External opening of the airway:

Most species:

Soft, pliable, easily dilated

Cartilage support

Pig:

Rigid nostrils for digging

Contain bone

NOSTRILS (nares)

The gross anatomy of the respiratory system (cont)

Hard and soft palates

Divided in half = septum (cartilage)

Turbinate or conchae bones = fine & scroll like, surface area

Good blood supply

Mucous membrane covering

Warm & humidify the incoming air

Caudal area of nasal cavity, olfactory sensory cells lead to olfactory

lobe of rostral area of brain

NASAL CAVITY

The gross anatomy of the respiratory system (cont)

Air filled spaces in skull (lighter)

Connect to nasal cavity

Limited exchange of air

Thermal & mechanical protection

Maxillary sinus roots of cheek teeth

Frontal sinus extends into horn in adult sheep & cattle

SINUSES

The gross anatomy of the respiratory system (cont)

SINUSES

The gross anatomy of the respiratory system (cont)

Located at back of throat

Common passage for food & air

Soft palate separates entrance of mouth & nasal

passages

Epiglottis (of larynx) overlaps soft palate

epiglottis & soft palate move when swallowing

PHARYNX

Entrance to lower airways

Connects between pharynx & trachea

Made up of 5 interconnected cartilages

• Epiglottis

• Thyroid = “Adam’s apple”

• 2 x Arytenoid

• Cricoid

Vocal cords – sound production

Allows only gases into lower respiratory tract

The gross anatomy of the

respiratory system (cont)

LARYNX

Textbook of Veterinary Physiology (2002)

Cunningham, Fig 27-4 p. 233

Breathing

Swallowing

PHARYNX

The gross anatomy of the

respiratory system (cont)

Passage of food & air

through pharynx & larynx

Oral cavity

• Non-collapsible tube

• Passes down the neck: larynx lungs

• Incomplete cartilage rings connected dorsally by a muscle

• Bifurcates to become 2 bronchi – one to each lung

• Mucous membrane lining is ciliated

• Mucociliary escalator

• Moves mucus & debris up from lung, swallowed or coughed

TRACHEA

The gross anatomy of the

respiratory system (cont)

Hilus

Bronchus enters

Pulmonary artery & nerve enter

Pulmonary vein & lymphatics leave

Right lung always bigger (why?)

Divided into lobes by fissures

Mucociliary escalator

LUNGS

The gross anatomy of the respiratory system (cont)

2 lungs – fill thoracic space

No fixed shape or size

Pleural sacs

Pleural cavity

Soft, spongy texture

Crackle when squeezed, float in H2O

Colour varies

The gross anatomy of the respiratory system (cont)

Bovine lungs Cranial lobe trachea

Middle lobe

Accessory lobe

Caudal lobe

Caudal lobe

Cranial Lobe

Right lung Left lung

Trachea branches (bifurcates)

L & R principal (main) bronchi

Identical structure to trachea – but smaller

Continual division bronchial tree

Bronchioles do not have supporting cartilage

Respiratory or terminal bronchioles are the smallest

BRONCHI AND BRONCHIOLES

The gross anatomy of the respiratory system (cont)

Allows control of airway diameter

Contracts = narrower

Relaxes = wider

Contracts due to

Irritants- pollen, dust = asthma

nervous system control

Relaxes due to

Adrenaline

SMOOTH MUSCLE

in bronchioles

The gross anatomy of the

respiratory system (cont)

‘Air sacs’

Major site of gas exchange

ALVEOLI

The gross anatomy of the respiratory system (cont)

Air sacs – millions of them!

Gas exchange occurs here

Blood capillaries intimately associated

Bronchiole respiratory bronchiole alveolar sacs

Importance of matching ventilation with blood flow rates optimal gas exchange

Have 2 types of epithelial cells:

Type I alveolar cells – exchange gases

Type II alveolar cells – secrete surfactant to reduce surface tension

ALVEOLI

The gross anatomy of the respiratory system (cont)

Illustration of one alveolus at micro scale

Nostrils

Nasal cavity

Pharynx

Larynx

Trachea

L/R 1 bronchus

Bronchioles

Intralobar bronchioles

Terminal bronchioles

Respiratory bronchioles

Alveolar ducts

Alveoli

What structures does the air pass through

from the atmosphere to the alveoli

(and back again)?

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Relate respiratory tract anatomy to

function Nose (nares) (oral cavity)

Nasal cavity

Pharynx

Larynx

Trachea

Bronchi (1o, 2o, 3o)

Bronchioles (terminal, respiratory)

Alveoli

Blood vessels Respiratory muscles

Airsacs

Nose (nares)

Nasal cavity

Oral cavity

Pharynx

Larynx

Trachea

Bronchi (1o, 2o, 3o)

Bronchioles (terminal,

respiratory)

Alveoli

Relate respiratory tract

anatomy to function (cont)

Conducting zone

Respiratory zone

Efficient gas exchange involves both respiratory &

circulatory systems:

Pulmonary ventilation (breathing – the movement of air

into and out of the lungs)

Exchange of O2 & CO2 between lung air space & blood

(by diffusion)

Transport of O2 & CO2 in blood

Exchange of O2 & CO2 between blood & cells / tissues

(by diffusion)

Relate respiratory tract anatomy to function (cont)

All of these steps have to work for efficient

transport of O2 & CO2 between air and cells

1. Pulmonary ventilation

2. ‘External’ respiration (gas

exchange in lung)

3. Transport of respiratory gases

4. Internal (cellular) respiration

Relate respiratory tract anatomy to function (cont)

Conducting zone:

• Passages for air to enter respiratory zone

• Air is warmed & humidified

• Immune protection

• Goblet cells secrete mucus

• Ciliated cells move trapped particles in mucus up out of the lungs

Respiratory zone:

• surface area,

• thickness of epithelial wall

• no cilia or goblet cells

Respiratory tract anatomy related to function (cont)

Pressure changes within the thorax during respiration

and the effect on gas movement

Movement of air into and out of the lungs is called

pulmonary ventilation

Movement of air is an example of mass flow driven

by pressure gradients

Air moves down a pressure gradient (high

pressure to low pressure)

Inspiration

Pressure in alveoli < atmospheric pressure so air moves in

Expiration

Pressure in alveoli > atmospheric pressure so air moves out