Chapter 13

The Respiratory System

https://www.youtube.com/watch?v=hc1YtXc_84A

https://www.youtube.com/watch?v=9fxm85Fy4sQ

http://ed.ted.com/lessons/what-do-the-lungs-do-emma-bryce

Primary Function of Breathing

Gas Exchange (simple diffusion)

– Oxygen from the air enters the blood to be carried to all body cells

– Carbon dioxide from the blood enters the lungs to be removed

Overview of Breathing

Inspiration

– Breathing in

– Also called inhalation

– Air is conducted into the lungs

Expiration

– Breathing out

– Also called exhalation

– Air is conducted out of the lungs

Four Respiratory Events

Pulmonary Ventilation (breathing)

• the entry and exit of air into and out of lungs

External Respiration

• Gas exchange between air and blood

site = lungs

Internal Respiration

• Gas exchange between blood and tissue fluid

site = tissues

Transport of gases

• To and from the lungs and the tissues

Why O2? Cellular Respiration

• Production of ATP in the cells

– ATP = energy supply for the cells

• Requires oxygen

• Releases carbon dioxide

• Cellular respiration requires the four respiratory events

Overview Upper

• Nose

• Nasal Cavity

• Pharynx

• Larynx

Lower

• Trachea

• Bronchi

• Lungs

The Nasal Cavity

Nasal Conchae – bony ridges

• Increase surface area

Olfactory Epithelium – high in the nasal cavity

• Odor receptors on the cilia of cells

The Nasal Septum

• Bony separation between the nasal cavities

The Nasal Cavity…

• cleansing of air by coarse nostril hair, cilia, and mucus

• Cilia inside nasal cavity beat mucus into the throat for swallowing

• Cilia in trachea and bronchi beat mucus upward into the pharynx

• Lysozymes in mucus-kills bacteria

The Nasal Cavity…

• mucous membrane warms and moistens inhaled the air

• Cools air during expiration

• Moisture deposited on trachea

• Nose may drip – condensation

Mucociliary Escalator • What tissue type?

The Pharynx

• Commonly referred to as the “throat”

• Passageway and connection between the nasal and oral cavities

• Three parts:

– Nasopharynx

– Oropharynx – common path

for food and air

– Laryngopharynx -Leads to the larynx

The Larynx

• The “voicebox”

• Cartilaginous structure

• Passageway of air between the pharynx and the trachea

• Adam’s apple – thyroid cartilage

• Vocal cords – mucosal folds

– Glottis – opening between the folds

– Vibrate to produce sound

Vocal cords

Swallowing of food

• The larynx moves up against the epiglottis

• Epiglottis – a flap of elastic cartillage closes

• Food is prevented from entering the larynx through the glottis

The Trachea

• Commonly known as the “windpipe”

• Flexible tube – connects larynx to the primary bronchi

• Ventral (anterior) to the esophagus

• Is held open via a C-shaped cartilage

• Is lined by pseudostratified ciliated columnar epithelium

Tracheostomy

• Insertion of a breathing tube via an incision in the trachea

The Bronchial Tree

• The trachea divides into R and L primary bronchi

• The primary bronchi branch into secondary bronchi

• The secondary bronchi branch into tertiary bronchi

• Brochioles – the smallest conducting airways

• Contraction of smooth muscle during Asthma attack

Alveoli

• Pockets (sacs) connected to each bronchiole

• Fill up with air during inhalation

• Simple squamous epithelium

• Site of gas exchange

• Surrounded by pulmonary

capillaries

The Lungs • Paired organs inside the ribcage

• Each lung is inside its own pleural cavity

• Each lung is surrounded by visceral and parietal pleura

• Apex – superior narrow portion

• Base – inferior broad portion

– Lies on top of the diaphragm

• Divided into lobules made of alveoli

Location of the Lungs

• Thoracic cavity (sealed)

– Ribs join–Sternum anteriorly & Vertebrae posteriorly

– Intercostal muscles – between ribs

– Diaphragm – thin muscle, forms the floor

• Pleurae

– Visceral – on the lung surface

– Parietal – attached to the thoracic wall

– Pleural fluid in between

– Intrapleural pressure – between the pleura

• Lower than the atmospheric pressure

• Keeps lungs inflated

Ventilation

• Entry and exit of air into and out of the lungs

Inspiration

• Active phase of ventilation

• Diaphragm and intercostals contract

– Diaphragm flattens

– Ribs move up and out

• Lungs volume increases

• Air pressure in alveoli decreases (intrapulmonary pressure)

– Partial vacuum

– Alveolar P < atmospheric P

– Inward passive airflow until pressures equalize

Expiration

• Usually a passive phase

– No muscle effort required

• Diaphragm and external intercostal muscles relax

– Dome shaped diaphragm

– Rib cage down and in

• Lungs recoil

– P intra-alveolar (intrapulm.) > P atmosphere

– Prevention of collapse due to surfactant on alveoli

– Surfactant lowers surface tension

Maximum Inspiratory Effort • Exercise, Strenuous

activities

• Accessory Muscles of respiration required:

– Erector spinae (back), abdominals

– Pectoralis minor (chest)

– Scalene and sternocleidomastoid (neck)

• Maximum lung expansion

Forced Expiration

• Blowing into a musical instrument

• Using Internal intercostals, abdominals

Spirometer

Determines if a medical problems is preventing lungs from:

• Filling with air

• Releasing air

Spirometer records the volume of air exchanged during:

• Normal and deep breathing

Spirogram is created

Respiratory Volumes

• Tidal Volume – amount of air that moves in and out when we are relaxed

– 500ml

• Vital Capacity - amount of air that moves in and out during deep breathing

Inspiratory Reserve V + Expiratory Reserve V.

– Inspiratory Reserve Volume

• 2900ml above the tidal volume – forced inspiration

– Expiratory Reserve Volume

• 4900 ml

Dead Air Space • Inhaled air that never reaches the alveoli

• Remains in the nasal cavities, trachea, bronchi, and bronchioles

• About 30% of the tidal volume

• Can reduce this by breathing slowly and deeply

Residual Volume

• Air that is not exhaled and remains in the alveoli

• About 1000ml

• Has a large amount of CO2

• Is not used for gas exchange

• Increase in residual volume in Emphysema

• Vital capacity is reduced

Respiratory Control

• Nervous Input

• Chemical Input

Normal Ventilation

• Normal adult breathing rate:

– 12 – 20 ventilations/minute

• Controlled by the primary respiratory center

– Located in medulla oblongata

Primary Respiratory Center

• Automatic motor input to the diaphram

– The phrenic nerve

Normal Breathing Rhythm

• Pons in conjunction with medulla oblongata

Other Nervous Input

• Additional input from the higher Centers of the brain can cause changes in breathing

– cerebral cortex

– limbic system

– hypothalamus

– emotions

• Conscious control of respiration:

– Temporary holding of breath

Protective Mechanisms

• Hering-Breuer Reflex

– Limits extent of inspiration

– Prevents over-expansion of lungs

– Vagus control

Chemical Control of the Repiratory Center

• Chemoreceptors in the resp. center

• Input via levels of CO2 and H+

• Increase in levels of CO2 and H+

Increase in the rate and depth of breathing

Influence of Oxygen levels

• No direct influence on the primary resp. center

• Low O2 levels sensed by chemoreceptors in:

– Carotid bodies

– Aortic bodies

Control via Carotid and Aortic Bodies

• Low blood oxygen concentration

increase in the rate of respiration

Pulmonary Circulation

Pulmonary Circulation

• RV

• Pulm. A.

• Lungs –gas exchange

• Pulm V.

• Left A

Gas Exchange in the Lungs

• Capillaries surround alveoli

• O2 diffuses into the capillaries

• CO2 diffuses out of the capillaries

Gas Exchange in the tissues

• Internal respiration

• At the systemic capillaries and tissues

• O2 enters the tissues

• CO2 enters the capillaries

Gas transport

• O2 transport via:

– Fe in Hb

– plasma (2-3% only)

• CO2 transport:

– Plasma + cytoplasm of RBCs (10%)

– Globin of Hb (30%)

– CO2 + H2O Carbonic acid (H2CO3) (H+) + (HCO3-)

• majority

Hemoglobin

• Protein involved in gas

exchange

• Inside RBCs

Homeostasis

• Regulation of blood pH via respiratory control!