The document outlines the structures and functions of the human respiratory system and the processes of respiration. It discusses that respiration provides energy to cells through the breakdown of glucose and involves the exchange of oxygen and carbon dioxide between the lungs and blood (external respiration) and between the blood and cells (internal respiration). It also describes the stages of inhalation and exhalation during breathing and different types of respiration such as aerobic and anaerobic. Common respiratory disorders are also listed along with an assignment on the topics covered.

1. OUTLINE
• Introduction
• Respiration
• Structures and functions of the respiratory system
• Processes (stages) of respiration
• Types of respiration
• Breathing
• Some common respiratory disorders
• Assignment
❖ INTRODUCTION
The cells of the body need energy (ATP) for all their metabolic activities. Most of this energy is
derived from chemical reactions which can only take place in the presence of oxygen (O2) in
multicellular organisms and the absence of oxygen (O2) in some unicellular organisms. The main
waste/end product of these reactions is carbon dioxide (CO2).
❖ RESPIRATION
Respiration can occur in both multicellular and unicellular organism. Therefore, respiration can
be defined as; the process of breaking down glucose with/without oxygen to release energy,
carbon dioxide (CO2) and water (H2O).
✓ Word Equation
Glucose + Oxygen Carbon dioxide + Water + Energy
✓ Chemical Equation
C6H12O6 + 6O2 6CO2 + 6H2O + Energy
Let’s discuss how important respiration is to a living cell. The only way energy (ATP) is made
available to the cells for metabolic activities is through the process called respiration. Without
this energy, cells would not be able to undergo cellular activities like growth and reproduction,
and these cells would ultimately die.
T H E R E S P I R A T O R Y S Y S T E M O F H U M A N S

2. ❖ STRUCTURES AND FUNCTIONS OF THE RESPIRATORY SYSTEM
The respiratory system is divided into two (2) parts. They are the upper respiratory and lower
respiratory tract.
✓ Upper respiratory tract
o Nose, nostrils and nasal cavity
o Pharynx
o Larynx
o Upper trachea
✓ Lower respiratory tract
o Lower trachea
o Lungs
o Bronchi
o Bronchioles
o Alveoli
▪ Nasal passage
It is the first passage point of entry of air. It has defensive mechanisms which are the hairs and
mucus. The hairs filter out large particles of dust from the incoming air. The mucus moistens and
warms the incoming air and helps trap any invading micro-organism.
▪ Pharynx
It is positioned behind the nasal cavity. It allows air to pass through to the lungs. It has tonsils as
its defensive structures. The tonsils contain white blood cells that would fight any disease-
causing organism that escaped the hairs and mucus of the nasal passage.
▪ Larynx (Voice box)
It is found at the region where the ‘Adam apple’ (thyroid cartilage). Air from the pharynx enters
the larynx through a small opening called glottis. This glottis is covered with a flap of tissue
called epiglottis. This flap of tissue prevents food and fluid from entering the air passage to cause
choking. Vocal cords are found at each side of the glottis. Exhaled air vibrates the vocal cords
over the glottis to produce sound. The larynx has cilia and mucus as its defense structures.
▪ Trachea (Wind pipe)
Air from the larynx enters the trachea. It also has cilia and mucus. It also warms and moistens the
air.
▪ Bronchi
The trachea splits into two short tubes called bronchi. They allow air to enter both lungs. They
also have cilia and mucus.
▪ Bronchioles
The bronchi sub-divide into numerous branches called bronchioles. They allow the passage of
air.
▪ Alveoli
The bronchioles end in a bunch of tiny air sacs called alveoli for which gaseous exchange occur.

3. ➢ Features of the alveoli that enable they to perform their functions
i. They have moist surfaces.
ii. Their walls are very thin and elastic.
iii. They are supplied and rich with blood capillaries.
iv. They have very large surface area.
v. They also have white blood cells that fight and invading micro-organism.
❖ STAGES OF RESPIRATION
✓ External respiration: this stage of respiration involves the exchange of gases between the
blood and the lungs.
✓ Internal respiration: this stage involves the exchange of gases between the blood and the
calls.
Differences between external respiration and internal respiration
External respiration Internal respiration
➢ Occurs outside the cells Occurs inside of cells
➢ Does not produce energy, carbon
dioxide and water
Produces energy, carbon dioxide
and water
➢ Does not involve the use of
glucose
Involves the use of glucose
❖ TYPES OF RESPIRATION
• Aerobic respiration
This type of respiration involves the use of oxygen to breakdown glucose to release
energy, carbon dioxide and water. Plants and animals are examples of organisms that
take part in aerobic respiration.
GLUCOSE + OXYGEN ENERGY + WATER + CARBON
DIOXIDE
• Anerobic respiration
There are some micro-organisms such as yeast and bacteria, and the skeletal muscle
tissue of vertebrates. With this type of respiration, energy is released in the absence of
oxygen. This is such that oxygen is not used to breakdown glucose to release energy.

4. ➢ Lactic acid/ lactate fermentation (In the human skeletal muscles)
GLUCOSE LESS ENERGY + LACTIC ACID
➢ Alcohol fermentation (In yeast and bacteria)
GLUCOSE LESS ENERGY + ALCOHOL + CARBON DIOXIDE
❖ BREATHING
Breathing is the process by which animals take oxygen into the lungs and give out carbon
dioxide. This means that breathing forms part of respiration. The process of breathing is
involuntary. It consists of two main stages.
• Inhalation/ Inspiration
✓ The ribs move up and outward.
✓ The diaphragm moves down.
• Exhalation/ Expiration
✓ The ribs move downward and inwards.
✓ The diaphragm moves up.
❖ SOME COMMON RESPIRATORY DISORDERS
✓ Common cold
✓ Tonsillitis
✓ Hay fever
✓ Bronchitis
✓ Asthma
✓ Tracheitis
❖ ASSIGMENT
1. Tabulate four (4) differences between inhalation and exhalation.
2. Tabulate three (3) differences between aerobic and anerobic respiration.
3. State the respiratory organ of the following organisms;
i. Tadpole
ii. Earthworm
iii. Elephant
iv. Amphibians
v. Insects
4. Tabulate the percentage composition of inhaled and exhaled air in the following;
i. Carbon dioxide
ii. Oxygen
iii. Water vapour
5. Briefly demonstrate an experiment to show that expired air contains carbon dioxide.
COMPLIED BY: MR. NOAMESI OYEH CORNELIUS
INTEGRATED SCIENCE FACILITATOR (CALVARY HILLCREST SCHOOLS)
RESEARCH SCIENTIST (UNIVERSITY OF CAPE COAST; DEPARTMENT OF
BIOMEDICAL SCIENCE)