The Respiratory System#BIOLOGYRESOURCENOTES

PHYSIOLOGY AND ANATOMY

A LESSON PREPARED BY: MR.HISHAM ZULFADHLI , SUBJECT HEAD OF BIOLO GY

Introduction• The primary function of respiration is to obtain oxygen ,that is used by the body cells and eliminate carbon dioxide, which the cells produce.

• Respiration consists of two related processes namely:

I. Internal Respiration

II. External Respiration

• Breathing occurs in two phases/parts:

I. Inhalation

II. Exhalation

What is Internal Respiration?• Internal respiration or cellular respiration refers to the intracellular metabolic process carried out in the mitochondria.

• The mitochondria uses oxygen and produces carbon dioxide.

• Once inside the cell the oxygen is used for producing energy in the form of ATP or adenosine triphosphate.

• Respiratory Quotient (RQ) is the ratio of carbon dioxide produced to oxygen used.

• The Respiratory Quotient may vary depending on the food consumed.

RQ = CO2 eliminated / O2 consumed

More on Internal Respiration• Internal Respiration can be aerobic with the presence of oxygen and anaerobic with the absence of oxygen.

• Oxygen is taken in is delivered by the circulatory system to body cells.

• Let’s Summarise what we have learnt!

• Internal respiration takes place at the tissues

• Gas transport

What is External Respiration?• External Respiration is the entire sequence of events in the exchange of oxygen and carbon dioxide between the surrounding environment and the body cells.

• External Respiration happens in four parts:

1) Air is alternately moved in and out of the lungs for the air to be exchanged between the atmosphere and the air sacs or alveoli that are located inside the lungs. This is called ventilation or more commonly, breathing.

2) Oxygen and carbon dioxide are exchanged in the air in the alveoli and the blood within the pulmonary capillaries through a process called diffusion.

3) The blood transports the oxygen and carbon dioxide between the lungs and the tissues.

4) Oxygen and carbon dioxide are exchanged between the tissues and blood by the process of diffusion across the tissue capillaries.

More on External Respiration• The respiratory system is only involved in part 1 & 2 while the circulatory system take cares of part 3 & 4.

• Let’s Summarise what we have learnt!

• External Respiration is the exchange of gases between the atmospheric air and the alveoli.

• Between the blood and the alveoli.

Internal and External RespirationLungs/Alveoli

Heart

1) Gas exchange between the air and the alveoli

2) Exchange of oxygen and carbon dioxide between the air and the blood

Tissues

3) Transport of oxygen and carbon dioxide from the lungs to the tissues

4) Exchange of gases between blood and tissues

Internal Respiration: Uses up oxygen to derive energy (Adenosine Triphosphate) from food and produces carbon dioxide as a by-product.

What is a by-product?

Organisms perform biochemical reactions to make products that they need to survive, but other products which are not needed can also be made in the process. These unwanted molecules are called the by-products of that reaction.

Example: Carbon Dioxide is a by-product of respiration but plants require carbon dioxide to photosynthesise.

The Respiratory System - Intro• The Respiratory system includes the respiratory airways leading to the lungs and the chest involved in the movement of air through the airways in and out of the lungs.

• The respiratory airways are tubes that carry air from the atmosphere to the alveoli that is located inside the lungs. The airways begin with the nasal passages.

• The lungs form the main organs in the respiratory system.

Anatomy of the Respiratory System• The Respiratory System is divided into two different parts:

I. Upper Respiratory Tract

II. Lower Respiratory Tract

• Upper Respiratory Tract

• The upper respiratory tract consists of the nasal passages, mouth, pharynx, larynx, glottis, epiglottis.

• Lower Respiratory Tract

• The lower respiratory tract consists of the trachea, bronchi, bronchioles, lungs, alveoli.

Anatomy of the Respiratory SystemFunctions:1) Nose and Nasal Cavity• The nose and nasal cavity form the main external opening for the

respiratory system and are the first section of the body’s airway. • The function of the nasal cavity is to warm, moisturize and filter the

air before it reaches the lungs. • The hairs and mucus on the nasal cavity helps to trap dust and

airborne particles.

2) Mouth• Also called oral cavity, is the secondary respiratory opening for the

respiratory tract. • The mouth provides a shorter distance to the lungs so the mouth

does not warm, moisturize or filter the air before it reaches the lungs

Anatomy of the Respiratory System3) Pharynx

• Also known as the throat is a muscular tube that extends the end of the nasal cavity to the posterior end of the oesophagus and larynx.

• The pharynx is divided into 3 regions: the nasopharynx, oropharynx, and laryngopharynx.

4) Larynx

• Known as the voice box is a short section of the upper respiratory tract that connects the pharynx and the trachea.

• It contains the vocal fold which allows the body to produce sounds and speech.

Anatomy of the Respiratory System5) Trachea (Windpipe)

• Trachea is the main airway that connects the larynx to the bronchi in the lungs.

• In addition, the epithelium lining the trachea produces mucus that traps dust and other contaminants and prevents it from reaching the lungs.

6) Bronchi and bronchioles

• The airway splits into left and right branches known as the primary bronchi. The left and right bronchi run into each lung before branching off into smaller secondary bronchi. The secondary bronchi carry air into the lobes of the lungs—2 in the left lung and 3 in the right lung.

• The secondary bronchi in turn split into many smaller tertiary bronchi within each lobe.

• The tertiary bronchi split into many smaller bronchioles that spread throughout the lungs.

Anatomy of the Respiratory System6) Bronchi and Bronchioles (continued)

• The main function of the bronchi and bronchioles is to carry air from the trachea into the lungs.

7) Lungs

• The lungs are a pair of large, spongy organs found in the thorax lateral to the heart and superior to the diaphragm.

• The left and right lungs are slightly different in size and shape due to the heart pointing to the left side of the body. Therefore, the left lung have only two lobes while the right lung have three lobes.

• The lungs contains millions of alveoli which is responsible for gas exchange.

Inspiration and Expiration• During inspiration, the outer intercostal muscles contract which raises the chest cavity or the ribs. This is accompanied by the lowering of the diaphragm.

• Together these movements serve to increase the area of the thoracic cavity which reduces the pressure. The air from outside rushes into the lungs.

•During expiration, the inner intercostal muscles contract bringing the ribs back to the original position and the diaphragm is also raised.

•This reduces the space in the thoracic cavity and increases the pressure. This expels the air out of the lungs.

Airway Resistance• Airway resistance is the resistance of the respiratory tract to airflow during inspiration and expiration.

• Parasympathetic stimulation occurs only in quiet and relaxed situations when the demand for airflow is low promotes smooth muscle contraction which increases airway resistance producing bronchoconstriction.

• Sympathetic stimulation on the other hand, bring about bronchodilation which decreases airway resistance by promoting smooth muscle relaxation.

Airway Resistance

Status of airways Effect on Resistance Factors leading to the effect

Bronchoconstriction Decreased Radius, Increased resistance to airflow

Allergy-induced spasm of the airways by reactive substances of anaphylaxis and Histamine

Physical Blockage of the airways caused by excess mucus, edema airway collapsed.

Bronchodilation Increased Radius, Decreased resistance to airflow

Epinephrine Increased carbon dioxide

concentration

Chronic Obstructive Pulmonary Disease• Chronic obstructive pulmonary disease (COPD) is a group of lung disease that is characterised by increased in airway resistance resulting from narrowing of the lumen of the airways.

• COPD encompasses three chronic long-term diseases: Chronic Bronchitis, Asthma, Emphysema.

• Chronic Bronchitis

• A long-term inflammatory condition of the lower respiratory tract that is triggered by frequent exposure to cigarette smoke, polluted air and/or allergens.

• The airways become narrowed by the frequent thickening of the airway linings and due to the overproduction of mucus.

• Accumulated mucus permits bacterial growth.

Chronic Obstructive Pulmonary Disease• Asthma

• Airway obstruction is due to thickening of airway walls.

• Plugging of the airways due to excessive secretion of thick mucus.

• Airway Hyper-responsiveness, constriction of the smaller airways caused by trigger-induced spasm of the smooth muscle in the walls. Triggers that lead to these inflammatory changes include repeated exposure to allergens such as dust, pollen, irritants and infections.

Chronic Obstructive Pulmonary Disease• Emphysema

• As the fragile tissues between air sacs are destroyed, air pockets in the lungs develop.

• Air becomes trapped in these spaces of damaged lung tissue.

• The lungs slowly enlarge, and breathing requires more effort.