Contents
❓Respiration and the Respiratory system
♈Respiratory system and the circulatory system
📛 Processes of Pulmonary ventilation
⛽Types of Cellular Respiration
🐙 Respiratory mechanism in the different Phyla of the Animal Kingdom
🛑 Functions of the Respiratory system
🐄 Respiratory System in higher Animals
🧠 Components of the Respiratory System
🐽 Nose / Nostrils / Nasal Cavity
🎳 Muscles in the Respiratory System
Learning Objectives
By the end of this section, you should be able to:
- Explain Respiration
- Describe the respiratory system
- Describe the Functions and structure of each respiratory organ
Introduction
The body system of animals work like a machine.
Just as a machine will not work unless it has diesel, a car will not start unless it has fuel or gas or electricity, so will an Animal's body not function unless it has oxygen. Oxygen is the fuel of Animal body cells. Body cells require oxygen to work, else they will breakdown and collapse.
Respiration and the Respiratory system
This Oxygen that we are talking about is abundant in the atmosphere. Air, which is a mixture of gases (Nitrogen, oxygen, carbon(IV)oxide and inert gases) is the main source of oxygen used by animals. Air is acquired and utilised by Animals by a process called RESPIRATION.
Before we fully discuss respiration, remember that while a machine uses fuel for its working processes, wastes will be produced by the machine. Wastes need to be taken away from the machine. Cars make use of exhaust pipes to lead wastes out, large factories use long pipes that go up into the upper atmosphere. This same thing happen in animals, cells produce wastes during metabolism that must not stay in the body, hence, need to be released. Gaseous wastes are released from the body through RESPIRATORY process.
This makes us to say that 'Respiration is the exchange of useful and non-useful gases between an Animal and its environment'.
The environment is the source of oxygen, and the site of disposal of respiratory waste product (carbon(IV)oxide + water vapour).
Respiration takes place in an animal's body through the use of several organs. These organs work together to take in and release gases from and to the environment, they make up the Respiratory system.
Processes of Respiration
Pulmonary ventilation
Pulmonary ventilation, or breathing in and breathing out, is the exchange of gases between the lungs and the atmosphere.
External respiration
External respiration is the exchange of gases between lungs and blood.
Internal respiration
Internal respiration is the exchange of gases between blood and body cells, tissues.
Cellular respiration
Cellular respiration involves how body cells use oxygen for their metabolic activities.
Respiratory system and the circulatory system
During pulmonary ventilation, oxygen is taken into the body. However, this oxygen need to reach every body cell. Respiratory system does not play any role in transporting oxygen to the body cells, hence the circulatory system come in play. Circulatory system collects oxygen that has been acquired, and transports it to every cells of the body (where it is finally collected and utilised). Gaseous waste products from the body cells are relayed to the respiratory system via circulatory system. Respiratory system collects these waste products and release them into the environment.
You can see that the Respiratory system and the Circulatory system are complementary.
Processes of Pulmonary ventilation
We have two processes which are inhalation and exhalation
Inhalation (breathing in) is the intake of gaseous materials from the environment into the body system. Inhalation can also be called inspiration.
Exhalation (breathing out) is the release of gaseous waste materials from the body system, into the environment. Exhalation can also be called expiration.
These two take place one after the other.
Types of Cellular Respiration
We have Anaerobic respiration and Aerobic respiration
There are some exception to Animals' use of oxygen as their cellular fuel. Some organisms don't require oxygen to function. They are referred to as anaerobes. Most anaerobes are primitive microscopic animals. They carry out their cellular metabolism in the absence of oxygen, this is called anaerobic respiration.
On the other hand, most other animals in the animal kingdom require oxygen as their cellular fuel (majorly for food breakdown to release energy). These organisms are called Aerobes (like you and I) and they carry out aerobic respiration.
Respiratory mechanism in the different Phyla of the Animal Kingdom
Protozoans
Protozoans are mostly unicellular organisms. They carry out gaseous exchange by Diffusion.
Porifera (Sponges)
Sponges carry out gaseous exchange by means of diffusion between the mesohyl (functional cells of sponges) and the external aquatic environment.
Cnidarians
Cnidarians carry out gaseous exchange by means of diffusion.
Flat Worms, Nematodes, Annelids
Flat worms, Round worms (nematodes) and Annelids (earthworms) carry out gaseous exchange by using their body surface.
Molluscs
Molluscs, e.g snails, carry out respiration by using their skins, and gills, situated in the palatial cavity (separates the mouth from the nose).
Arthropods
Arthropods like insects and arachnids carry out respiration via Spiracles and trachea. Trachea are tubes that carry air directly to cells for gaseous exchange. Spiracles are openings on the body surface through which air is taken into tracheae.
Echinoderms
Echinoderms, like starfish, do not have specialised respiratory structures. They diffuse gases, and some make use of their tube feet.
Fishes
Fishes' respiratory structure is called gills. Gills deliver dissolved oxygen into blood, and excrete dissolved gaseous wastes into water.
Amphibians
Amphibians, like frogs, have several respiratory structures such as skin surface, lungs, gills. Their skin have to stay moist in order for them to absorb oxygen. If their skin get too dry, they cannot breathe and they may die.
Reptiles
Reptiles' skins are covered in scales which make them unable to breathe via their skins. They use lungs for respiration, their lungs are usually more developed than that of the Amphibians.
Birds, Mammals
Birds and mammals breathe using nostrils, through which gases get to the lungs, where respiration and gaseous exchange occur.
Functions of the Respiratory system
- Respiratory system supplies the body with oxygen and disposes off carbon(IV)oxide.
- Respiratory system filters inhaled air.
- Respiratory system is responsible for the production of sound.
- Respiratory system contains receptors for smell.
Respiratory System in higher Animals
Respiratory organs are divided into two groups which is based on the function they carry out, these two groups are:
- Upper respiratory tract (nose to larynx)
- Lower respiratory tract ( trachea onwards)
Upper Respiratory Tract
The upper respiratory tract consists of the nose and the pharynx. Organs in the upper tract form part of the conduction zone. The primary function of URT is to receive air from the external environment, and filter, warm, and humidify it, before it reaches the delicate lungs where gas exchange will occur.
Lower Respiratory tract
The airways beyond the larynx is divided into two zones. The conducting zone, which continues from the upper respiratory tract, extends from the top of the trachea to the end of the terminal bronchioles.
This zone contains no alveoli, and does not exchange gases with blood.
The Respiratory zone, which is the second zone, extends from the bronchioles downwards.
The respiratory zone is where gas is exchanged. It consists of alveoli, alveolar sacs, alveolar ducts and respiratory bronchioles.
Components of the Respiratory System
The Respiratory system starts with the nostrils and ends in the alveolus (plural: alveoli)
Nose / Nostrils / Nasal Cavity
Nose is the outer opening of the respiratory system, and it serves as an entryway for air (from the environment) into the body of animals. Nose filters debris from air, and secretes antibacterial fluids which act on bacteria present in air.
Use yourself as an example, touch that muscle between your two nostrils, it divides your nasal cavity, and it is called Nasal septum.
Nose is separated from the mouth by soft palate and hard (bony) palate.
Nose contains hairs (bristle-like hairs) called Vibrissae, and most of the lines of the nose are filled with mucus.
There are three bony projections inside the nasal cavity:
- The superior nasal conchae
- The middle nasal conchae
- The inferior nasal conchae.
Air pass between these bony projections via nasal meatuses.
Mucus is secreted by the paranasal sinuses.
Nose warms and humidifies air; also enhances voice resonance.
Pharynx
Pharynx is a funnel-shaped tube that collects air from the nasal cavity (or nostrils), and passes it down into the oral cavity.
Pharynx is shared by both the respiratory system and the digestive system.
Pharynx is divided into:
- Nasopharynx
- Oropharynx
- Laryngopharynx
Tonsils (we discussed this in lymphatic system), form a ring at the connection of the oral cavity and the pharynx. Here, they protect against foreign invasion of antigens like bacteria.
Larynx
Larynx (called sirinx in birds) is composed mainly of three cartilages:
- Thyroid cartilage
- Cricoid cartilage
- Epiglottis
Thyroid cartilage
Thyroid cartilage is a hyaline cartilage and it forms the anterior (or front portion) of larynx. It is called Adam's apple in humans.
Cricoid cartilage
Cricoid cartilage is also a hyaline cartilage and it forms the posterior (or back portion) of the larynx.
Epiglottis
You might have been familiar with epiglottis before now, one of the softest bones (but is actually a cartilage) in the body right? Epiglottis is a cartilage of the larynx, and it blocks food that is coming from the mouth, from entering the respiratory system. It makes food enter oesophagus, instead of trachea.
Top section of the larynx | photo credit: National cancer inst.
Trachea
Trachea is a flexible tube, also called windpipe.
Tracheal wall contains several cartilaginous rings to prevent collapse of the tracheal airway.
Each tracheal ring is C-shaped, incomplete (not joined), which permits variation in diameter for increased ventilation requirements.
Bronchus (plural: Bronchi)
Bronchi are branches which originate from the trachea. Trachea splits into left and right to enter the two lungs, forming two bronchi. These first set of bronchi that is as a result of the splitting of trachea are called primary bronchi.
The primary bronchi further split to form the secondary bronchi (also called Lobar bronchi). The secondary bronchi split to form the tertiary bronchi (also called segmental bronchi).
Tertiary bronchi continue to split, the splitting of tertiary bronchi give rise to bronchioles.
Bronchioles split again to form the terminal bronchioles. One tertiary bronchus forms about 6500 terminal bronchioles.
At the end of the day, the splitting of several bronchi and bronchioles give rise to a Bronchial tree.
Alveolus (plural: Alveoli)
Terminal bronchioles connect to respiratory bronchioles, which then advance into the alveolar ducts. Alveolar ducts end in alveolar sacs. This means that each bronchiole terminates in an elongated space, enclosed by many air sacs called alveoli. Alveoli are usually surrounded by blood capillaries.
Present there as well, are Alveolar Macrophages, they ingest any microbe that reach the alveoli. The Pulmonary Alveoli are microscopic, which means they can only be seen through a microscope.
Alveoli are membranous, sac-like structures. They are the region of gaseous exchange between the lungs and the blood.
Respiration in the respiratory system moves along this trend:
Nose → Nasal cavity → Nasopharynx → Oropharynx → Laryngopharynx → Larynx → Trachea → Primary bronchi → Secondary bronchi → Tertiary bronchi → Multiple branches of bronchi → Bronchioles → Terminal bronchioles → Respiratory bronchioles → Alveolar ducts → Alveolar sacs
Cells in the Alveolus
Type I cells : simple squamous (=covered in scales) cells that form the internal lining of each alveolus.
Type II cells : may be called septal cells. They secrete surfactant - an oily secretion which contains phospholipids and proteins that coat alveolar surfaces and reduce surface tension.
Muscles in the Respiratory System
There are major muscles that play important roles in the respiratory system. They are:
- Intercostal muscles
- Diaphragm
- Abdominal wall muscles
- Scalenes
- Pectoralis minor
- Serratus anterior
- Sternocleidomastoid
Control of Respiration
Muscular contraction and relaxation controls the rate of expansion and constriction of the lungs. These muscles are stimulated by nerves that carry messages from the part of the brain that controls breathing, the medulla. Two systems control breathing: an automatic system and a voluntary system. Both are involved when you hold your breath.
States of breathing
Variations in breathing are related to the frequency of breathing cycles, depth of inspiration, or both.
Eupnea: quiet breathing.
Dyspnea: difficult breathing.
Hyperpnea: breathing characterized by increased depth, frequency, or both; usually follows active physical activity.
Polypnea: rapid, shallow breathing.
Apnea: absence of breathing.
Diseases of the Respiratory system
Bronchitis: inflammation of the bronchus.
Asthma: restricted flow of air through the respiratory system, caused by various reasons ranging from genetics to blockage of the respiratory tract.
Cystic fibrosis: excessive mucus blocks the airway and lead to difficulty in breathing.
Tonsillitis: inflammation and swelling of the tonsils.
Pneumonia: bacterial or viral infection in the lungs where bronchi and alveoli fill with a thick fluid.
Summary
🏭 Respiration involves the exchange of gases between the body and its environment.
🏭 Oxygen is taken into the body from the environment and carbon(IV)oxide is released as a by-product.
🏭 Processes of respiration are:
- Pulmonary ventilation
- External respiration
- Internal respiration
- Cellular respiration
🏭 Several organs that work together to perform respiratory function are called respiratory system
🏭 Respiratory organs in agricultural animals include:
- Nose or nasal cavity
- Pharynx
- Larynx
- Trachea
- Bronchus
- Bronchioles
- Alveoli
🏭 Nose to bronchioles make up the conduction zone of the respiratory system.
🏭 Alveoli make up the respiratory zone.
🏭 Gaseous exchange between circulatory system and respiratory system take place in the alveoli.
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TEST QUESTIONS: RESPIRATORY SYSTEM
TEST QUESTIONS: RESPIRATORY SYSTEM
Total Questions: 30
you'll have 28 second to answer each question.
Quiz Result
Total Questions:
Attempt:
Correct:
Wrong:
Percentage:
Quiz Answers
1. Gills are found in the following except?
Mammals
2. Bronchioles terminate in grape-like sac clusters known as ...
Alveoli
3. A malfunction of the breathing centers in newborns may result in ...
Sudden infant death syndrome
4. A vessel that carries oxygen poor blood into the lungs is known as
Pulmonary artery
5. The process by which blood from the heart get its oxygen from the lungs is termed...
Pulmonary circulation
6. Diffusion of gases between air and blood occurs mostly in the?
Alveoli
7. A difficult, labored state of breathing is termed _
Dyspnea
8. The following are part of the respiratory system in Mammals except?
Spleen
9. The following statements about respiratory system are correct except _
Diffusion of carbon(IV)oxide from the blood into the body
10. Diffusion is the movement of materials from a low concentration to a higher concentration
False
11. Sponges and jellyfish take in gases directly from the surrounding water
True
12. Sponges and jellyfish lack specialized organs for respiration
True
13. Oxygen occupy what percentage of air volume in a given sample?
21%
14. Breathing in and breathing out are classified under...
Pulmonary ventilation
15. Exchange of gases between lungs and blood is termed...
External respiration
16. Exchange of gases between blood and body cells/tissues is termed...
Internal respiration
17. Anaerobes require oxygen to carry out cellular respiration
False
18. A respiratory organ in insects is ...
Trachea
19. _ is a cartilage that prevents food coming from the mouth from entering into the trachea
Epiglottis
20. _ divides the nasal cavity into left and right?
Septum
21. Vibrissae is...
Hair-like structures in the nose
22. The several bony projections inside the nasal cavity is called?
Conchae
23. Mucus is secreted in the nose by ...
Sinus
24. Tonsils present in the pharynx of respiratory systems perform major function of...
Protect against foreign invasion of antigens
25. _ is a muscle which separate the thoracic section from the abdominal section of an Animal's body
Diaphragm
26. Breathing during sleep is controlled by what part of the brain?
Medulla
27. Absence of breathing occur in some animals especially during sleep, this is called...
Apnea
28. Why do newborns breathe so heavily compared to an adult?
Adaptive process aimed at inflating the alveoli
29. Inability to inflate the alveoli of the lungs in newborns lead to
Sudden infant death syndrome
30. One of these correctly show the trend of the respiratory system?
Nasal Cavity > pharynx > larynx > trachea > bronchus > alveoli
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