1. RESPIRATORY SYSTEM (STRUCTURE AND FUNCTION)
بسم الله الرحمن الرحيم
RESPIRATORY SYSTEM (STRUCTURE AND FUNCTION)
Dr. Mohammed Sharique Ahmed Quadri
Assistant Prof. physiology
Al maarefa college

2. Anatomy Of Respiratory System
Nasal passages (Nose)
Pharynx (Throat )
Larynx (Voice box)
Trachea –Divides into Right main bronchus and Left main bronchus
Bronchi
Bronchioles—large and small
Terminal Bronchioles
Respiratory Bronchioles
Alveolar Duct
Alveoli

6. Important Points
Trachea divides into Right and Left Bronchi which enter Right and Left Lungs
Within each lung, bronchi continue to branch into narrow (small diameter),shorter and more numerous airways like branching of a tree.
Small braches are known as Bronchioles- lastly Terminal bronchioles

7. Important Points [Cont]
At the end of Terminal Bronchioles, are Respiratory Bronchioles , Alveolar duct, Alveoli.
Tiny sacs(Alveoli) where gas exchange takes place between alveolar air and blood capillaries

8. Important Points [Cont]
Trachea and large bronchi have cartilaginous rings that prevent these from collapsing.
Very small bronchioles have no cartilage to hold them open. Their wall has smooth muscle
This smooth muscle is innervated by Autonomic Nervous System, and is also sensitive to some hormones and local chemicals, which affect the air flow in small bronchioles

9. Important Points [Cont]
Sympathetic stimulation causes bronchodialation by acting on β2(adrenergic) receptors.
Parasympathetic stimulation causes bronchoconstriction by acting on muscarinic receptors

10. FUNCTIONS OF RESPIRATORY SYSTEM
1- Breathing Oxygen in, and breathing out Carbon dioxide

11. RESPIRATION TYPES Cellular Respiration ( Internal Respiration)
External Respiration
Cellular Respiration
It refers to intracellular metabolic process in the Mitochondria, which uses O2 to derive energy (ATP) from food and produces CO2 as a byproduct.

12. CELLULAR RESPIRATION

13. CELLULAR RESPIRATION (CONT)
During intracellular metabolic process
On a mixed diet ( Carbohydrate, Fat, Protein ) O2 used is 250 ml/min and CO2 produced is 200 ml/min.
We use the Term Respiratory Quotient (RQ)
CO2 produced = 200
RQ =
O2 used = 250
- On a mixed diet RQ = O.8
-- RQ depends on the type of food used
-- when Carbohydrate is used RQ= 1
-- when Fat is used RQ= 0.7
-- when Protein used RQ=0.8

14. EXTERNAL RESPIRATION
Exchange of O2and CO2 between External environment and cells of body. It has 4 steps.
1 – Gas exchange between the atmosphere and alveoli.
2- Exchange of O2 and CO2 between air in the alveoli and blood in pulmonary capillaries.
Transport of O2 and CO2 by the blood to the tissues.
4 – Exchange of O2 and CO2 between system capillaries and tissue cells

16. Non Respiratory Functions of Respiratory System
Helps in regulation of pH of blood (Acid –base balance) , by adjusting the rate of removal of CO2.
It is route for water loss and heat elimination.
(Inspired air is humidified and warmed by the respiratory airways.)
Respiratory pump – helps in venous return.
It enables speech, singing .

17. Non Respiratory Functions of Respiratory System [cont]
It defends against inhaled foreign material.
Prostaglandins are inactivated in the lungs.
Conversion of angiotensinI to angiotensinII hormone, by ACE ( angiotensin converting enzyme ).
Nose– part of respiratory system , organ of smell.

18. Gas Exchange Between Alveoli & Pulmonary Capillaries
O2 and CO2 diffuse through alveoli.
Rate of diffusion depends on thickness of alveolar membrane, surface area and partial pressure of O2 and CO2.
Alveolar wall consists of single layer of alveolar cells [type I].

19. Gas Exchange Between Alveoli & Pulmonary Capillaries [cont]
Each alveolus is surrounded by a network of pulmonary capillaries, which are also lined by single layer of endothelial cells.
The interstitial space between an alveolus and capillary is very thin 0.5 µm which facilitates gas exchange.
Respiratory Membrane [Alveolar wall and Capillary wall].

20. Gas Exchange Between Alveoli & Pulmonary Capillaries [cont]
Lungs contain about 500 million alveoli, each about 300 µm in diameter [surface area exposed between alveolar air and pulmonary capillary blood is about 75 m2, size of tennis court].
In alveoli, there are alsoType II alveolar cells . They secrete Pulmonary Surfactant.
Pulmonary Surfactant is a phospholipoprotein complex that helps in lung expansion.

23. Gas Exchange Between Alveoli & Pulmonary Capillaries [cont]
Also in alveolar lumen, present are alveolar macrophages which help in defense [Phagocytosis].
Pore of Kohn – are present between adjacent alveoli. Their presence permits air flow between adjacent alveoli. This process is called Collateral Ventilation.

24. Lungs & Thoracic Cavity
Two lungs
Right lung is divided into 3 lobes [upper, middle, lower] by oblique and transverse fissure.
Left lung is divided into 2 lobes [upper, lower and has lingula] by oblique fissure.
Lungs – has alveoli, blood vessels and large quantities of elastic connective tissues.
Changes in lung volume and alveolar volume are brought about through changes in dimensions of thoracic cavity.

25. Lungs & Thoracic Cavity [cont]
The outer chest [Thorax] is formed by 12 pairs of curved ribs, which join the sternum anteriorly and thoracic vertebrae posteriorly.
Diaphragm – forms floor of thoracic cavity. Diaphragm is sheet of skeletal muscle that separates thoracic cavity from abdominal cavity. It is penetrated by esophagus and blood vessels.
In the lung and chest wall, there is considerable amount of elastic connective tissue.

26. Lungs & Thoracic Cavity [cont]
Pleura – separates each lung from the thoracic wall.
Pleura which surround each lung has two layers – Visceral Pleura [inner layer] which surrounds the lung and Parietal Pleura [outer layer] which is under thorax.
Interior of pleural sac(space between parietal and visceral pleura) is known as Pleural Cavity.
Surfaces of pleura secrete intrapleural fluid which lubricates surfaces as they slide on each other during respiratory movements.
Clinical application – pleurisy – [inflammation of pleura]. It causes pain during inspiration and expiration, and friction rub.

28. References Human physiology by Lauralee Sherwood, seventh edition
Text book physiology by Guyton &Hall,11th edition
Text book of physiology by Linda .s contanzo,third edition

29. THANK YOU