Chapter 15

Respiratory System

Parts of Respiratory System• Nasal Cavity• Pharynx• Epiglottis covers the opening to trachea during

swallowing• Glottis Opening under the epiglottis• Larynx Made of cartilage that contains the voice

box• Trachea Breathing tube in the front of neck. Has

cartilage rings that keeps it open

• Trachea branches into two tubes. One tube goes to the right lung and the other tube goes to the left lung. These tubes are called the Bronchi (single is Bronchus).

• The Bronchi then branch into smaller tubes in the lungs called the Bronchioles.

• The bronchioles end at little sacs called Alveoli. It is at the alveoli that gas exchange with the blood is done.

Blood In

Blood Out

Alveoli

Which direction is the flow of blood?

More Parts of Respiration• The lungs are in the Thoracic Cavity. The Rib

cage form the top and sides of the thoracic cavity.

• The bottom of the thoracic cavity is maintained by the diaphragm. This is a large dome shaped muscle.

• The Lungs are encased by a membrane called the Pleural Membrane. The pleural membrane made up of two membranes.

Problems About Breathing• This is the most common way for a person to

get germs into their body. – So therefore the body filters the air before it

enters the lungs. • Filtering Air

1. Air moves into nasal cavity and thick hairs, mucus, and cilia.

2. Cilia cover the trachea and move things upward

• Cilia move dust, mucus, and food bits that went down the breathing tubes up.

• When there is enough debris that has moved up into the pharynx then it is either swallowed or spat out.

• Air is warmed and made moist before it gets too the lungs. – It is warmed by the blood that moves through the

lungs– Its is moistened by the wet surfaces of the

passages of the lungs.

So what do the Pleural Membranes do?

• The pleural cavity has a slightly lower pressure than the atmosphere.

• Why do the pleural membranes have a lower pressure?

• Research it Page 290

• The lower pressure in the pleural membranes create a lower pressure

• This lower pressure stops from lungs from collapsing.

• A collapsed lung can not get any oxygen.• If someone has an accident and gets their

pleural membrane broken then a common thing to happen is a collapsing of a lung

How we breath

• There are two parts that are involved in breathing1. Breathing in Inhalation Inhale2. Breathing out Exhalation Exhale

Inhalation• Starts in the Brain in a place called the respiratory

centre in the Medulla oblongata• There are special nerves that detect chemicals.

These nerves are called chemoreceptors. • These particular chemoreceptors detect carbon

dioxide (CO2) and hydrogen ion (H+) levels. • These chemoreceptors are located in in the carotid

arteries (carotid bodies) and are in the aorta (aortic bodies)

• When carbon dioxide levels and hydrogen ions are at high levels the chemoreceptors send a message to the respiratory centre and the rate and depth of breathing increases.

• The respiratory centre sends a message to the diaphragm and the muscles of the rib cage.

• The diaphragm contracts and moves down this causes the thoracic cavity to increase size

• The rib muscles contract the external intercostal muscles contract and this causes the rib cage to become wider and increases the size of the thoracic cavity

• This increase in the thoracic cavity size and volume creates negative pressure ( or a vacum) in the lungs and air rushes in. negative pressure because intrapleural pressure is even less

Exhalation• The respiratory centre stops sending nervous

signals this causes the diaphragm and the rib cage to relax and they return to their normal shapes

• They return to their normal shapes because of elastic forces the body pushing in on the lungs

• You can force extra air out if you contract the internal intercostal muscles. This forces the ribs cage to become smaller and forces the ‘guts’ to push up against the diaphragm and therefore pushes air out

• There are also stretch receptors in the lungs.• When the lungs are breathing in the alveoli

have stretch receptors and if they get too big then the respiratory centre stops sending its signal

Two types of Respiration

1. External Respiration– This refers to the exchange of gases between the

air in the alveoli and the blood

2. Internal Respiration– This refers to the exchange of gases between the

blood and Tissues in the body

External Respiration• The pressure of CO2 in the blood is higher than

that of the air. So CO2 moves from blood to air.

• Most of the CO2 is carried as bicarbonate ions (HCO3

-)• Carbonate ions combine with a hydrogen ion

to form hydrogen bicarbonate. This is then turned into water and carbon dioxide

H+ + HCO3- H2CO3 H2O + CO2

• This reaction is catalyzed by the enzyme carbonic anhydrase

• Hemoglobin is carrying no oxygen and is referred to as deoxyhemoglobin

• Oxygen concentrations are higher than that of the blood in the lungs so there is a pressure for oxygen to move into the blood

• Red blood cells take up the O2 and the hemoglobin is referred to as oxyhemoglobin

Hb + O2 Hb + O2

Internal Respiration

• Oxyhemoglobin gives up its oxygen and it then moves into tissues

Hb O2 Hb + O2

• Carbon dioxide diffuses into blood from the tissues because of the pressure difference

• Hemoglobin takes up a small amount of CO2

• The Hemoglobin that takes up CO2 creates carbaminohemoglobin

Hb + CO2 Carbaminohemoglobin

• Most of the CO2 is taken up by the water in the plasma and it forms carbonic acid

CO2 + H2O H2CO3 H+ + HCO3-