UNIT 3:RESPIRATORY SYSTEM AND

GASEOUS EXCHANGE

Sequence of events that results in gas exchange.

In terrestrial vertebrates it includes 3 steps:1. Ventilation: Inspiration and

expiration.2. External respiration: Gas exchange

between air (in lungs) and blood. Blood then transport Oxygen to the body tissue cells.

3. Internal respiration: Gas exchange between blood and tissue fluid. Blood then transports carbon dioxide to the lungs.

BREATHING

External respiration

Internal respination

oxygenCarbon dioxide

oxygen Carbon dioxide

Alveoli filled with air (gas)

Body cells surrounded by tissue fluid

Blood – part of circulatory system contain red pigment – hemoglobin, to transport gasses

Gas exhange surface must be:•Moist•Thin•Large in relation of size of body

Process: Diffusion of gasses (oxygen and carbon dioxide

Is the process whereby an organism uses oxygen and food to produce energy (ATP) and 2 by products e.g. water and carbon dioxide

Glucose + O2 ATP + H2O + CO2

Therefore gaseous exchange is necessary for to get oxygen for cellular respiration.

Cellular respiration

Consists of:1. Nose2. Air passages:

Pharynx Trachea Bronchus Bronchioles

3. Lungs – Alveoli

HUMAN RESPIRATORY SYSTEM

Nose has a nasal cavity that leads to the pharynx.

Nasal cavity is lined with cilia and hairs and goblet cells that make mucus (anti-septic and moisten air)– filter the air – dust, pollen and other foreign material sticks to it.

3 x turbinate bones divide the nasal cavity into 4 passages – This enlarges the surface of the nasal cavity – For warming, cleaning and moisten of air.

Several surface blood vessels help to warm air.

NOSE

Pharynx – pass air form nose to trachea via larynx.

Trachea: long, straight tube kept open by C-shaped cartilage rings.

Trachea – lined with cilia and goblet cells (mucus production) – traps foreign particles

AIRPASSAGES

Lining of airpassages

CILIA (SEM) TRACHEAL LINING

Trachea divides in a right and left bronchus – consist of C-shaped cartilage rings and lined with goblet cells (mucus)

Bronchi branch in lung to form bronchioles – branch further and cartilage rings disappears – lead air to air sacs of lung.

AIRPASSAGES: BRONCHI AND BRONCHIOLES

Bronchiole

Left bronchus – long, branch in 2

Right bronchus-shortBranch in 3

LUNGS Right lung (3 lobes -

shorter) and left lung (2 lobes – longer, narrow)

Spongy, elastic pink organ.

Consists of several air sacs called alveoli.

Alveoli are grouped together and form the endings of the bronchioles.

ALVEOLI Lined with single layer

squamous epithelial cells – Thin easy diffusion of gas.

Alveoli is surrounded by a network of blood capillaries – gasses diffuse into and out of blood.

Alveoli is lined with moist layer – oxygen dissolves in moisture and diffuses through alveoli wall into blood capillary.

SEM TEM

Alveoli

Pulmonary artery (Deoxygenated blood)

Pulmonary vein (Oxygenated blood)

Diaphragm

Bronchiole

Bronchus

Trachea

Pharynx

Turbinate bones

BREATHING - The process whereby air (gasses) move in and out of the body.

INSPIRATION

INSPIRATION

EXPIRATION

EXPIRATION

Diaphragm contracts (moves down)

Diaphragm relaxes (moves up)

Rib cage expands as rib muscles contract

Rib cage gets smaller as rib muscles relax

Air inhaledAir exhaled

When pressure in lungs decrease – air rush in

When pressure in lungs increase – air is pushed out

Air moves in and out of the body via the same route.

All terrestrial vertebrates do this except for birds.

The lungs are not completely emptied during each breathing cycle.

The air entering mixes with used air remaining in the lungs.

This help to conserve water, but decreases gas-exchange efficiency

TIDAL VENTILATION MECHANISM

A spyrometer can be used to determine how much air enters the lungs.

Your lungs has a volume of +/- 5 liters. During a normal breath, only 0.5 liters of air

is exchanged – This air is known as tidal volume.

During forced breathing, as much as 3.5 liters of air can be exchanged, this is known as vital capacity. (The fitter you are, the higher your vital capacity.)

+/- 1.5 liters of air always remains in the lungs – this air is known as residual air/volume.

Determining lung capacity

RESPIRATORY CENTER

Normal breathing rate for adults: 12 – 20 ventilations per minute.

Respiratory Center in the Medulla Oblongata of the brain controls breathing.

The respiratory center send impulses through the phrenic nerve to the diaphragm and through the intercostal nerve to the intercostal muscles to either contract or relax. (Contract during inspiration and relax during expiration)

Nervous control of breathing

Brain

Respiratory center automatically regulates breathing

Intercostal nerves stimulate the intercostal muscles

Intercostal muscles

Pheric nerve stimulates the diaphragm

Diaphragm

GAS EXCHANGE

EXTERNAL RESPIRATION INTERNAL RESPIRATION

Gas exchange between air in lungs and blood

Movement driven by diffusion gradient. ( [] to [])

Gasses exerts pressure, the amount of pressure each gas exerts is called – partial pressure (PO2

and PCO2)

Gas exchange between blood and tissue fluid

Movement driven by diffusion gradient. ( [] to [])

Gasses exerts pressure, the amount of pressure each gas exerts is called – partial pressure (PO2

and PCO2)

If PO2 differs across a membrane – oxygen will

diffuse from a high to a low pressure.

If PCO2 differs across a membrane – carbon

dioxide will diffuse from a high to a low pressure.

During inspiration the alveoli fills with air – higher PO2

and lower PCO2 than blood.

Oxygen diffuse from alveoli into blood and carbon dioxide diffuse from blood into alveoli.

EXTERNAL RESPIRATSION

When blood reaches the tissue, cellular respiration in cells causes the tissue fluid to have a lower PO2

and a higher PCO2 than the

blood. Thus oxygen diffuse from a high pressure in

the blood to a low pressure in the tissue fluid and eventually in the tissue cells.

Carbon dioxide diffuse from a high pressure in the tissue fluid to a low pressure in the blood.

INTERNAL RESPIRATION

TRANSPORT OF OXYGEN Most oxygen is transported by hemoglobin

(red pigment protein in erythrocytes). Oxygen combines with hemoglobin to form

oxyhemoglobin.Hb + O2 = HbO2

Hemoglobin Oxygen Oxyhemoglobin

A small amount of oxygen is transported in solution in the blood plasma.

HEMOGLOBIN MOLECULE

Each red blood cell carries 250 million Hb molecules = 1 Billion Oxygen molecules

Consist of 4 polypeptide chains (protein – 2 alpha and 2 beta).

Each chain is associated with a heme group.

Each heme group contains an iron atom.

Iron binds with oxygen.

Most CO2 is transported as bicarbonate ions (HCO3

-)

HOW?

FIRST CO2 binds with water to form carbonic

acid (H2CO3)

CO2 + H2O = H2CO3

Then carbonic acid dissosiates to form hydrogen and bicarbonate ions.

H2CO3 = H+ + HCO3-

TRANSPORT OF CARBON DIOXIDE

A small amount of carbon dioxide is transported by the Hemoglobin molecules in the form of carbaminohemoglobin (HbCO2).

CO2 + Hb = HbCO2

The higher the amount of hydrogen ions in the blood the lower the pH. Therefor hydrogen ions bond with the globin part of Hb to keep the pH normal in the blood.

TRANSPORT OF CARBON DIOXIDE

The following lower respiratory tract disorders are caused by exposure to infectious pathogens and / or polluted air, including tobacco smoke.

PneumoniaPulmonary FibrosisPulmonary TuberculosisEmphysemaBronchitisAsthma

COMMON BRONCHIAL AND PULMONARY DISEASES

PNEUMONIA

Bacteria streptococcus can cause pneumonia

Alveoli fill with pus and fluid making gas exchange difficult

X-ray of a patient with pneumonia

Pulmonary fibrosis Fibrous connective

tissue builds up in lungs, reducing their elasticity and Oxygen diffusion.

PULMONARY TUBERCULOSIS

Caused by a bacillus bacterium

Emphysema Alveoli burst and fuse

into enlarged air spaces. – Surface area for gas exchange is reduced.

Bronchitis Airways are inflamed

due to infection (acute) or due to an irritant (Chronic). Coughing brings up mucus and pus.

ASTHMA Airways are inflamed

due to irritation and bronchioles constrict due to muscle spasms

Smoking causes almost 90% of all lung cancers and is also a major cause of emphysema.

SMOKING AND LUNG DISORDERS

Healthy normal lung of a non-smoker

Lung of a smoker

Lung with large tumors causing lung cancer