Respiratory System: An Overview

Introduction to the Respiratory System

• Organs that make up the respiratory system are key to ventilation and respiration.
• The anatomy and the histology of the system is fundamental to understanding its function.
• Respiration involves both internal (cellular) and external respiration.
• Ventilation is a crucial process.
• Gas exchange occurs in specific locations within the system.
• Gases are transported by blood.
• Different diseases can affect the respiratory system.

Main Parts of the Respiratory System

• The human thorax contains several key components of the respiratory system.
• Key structures for the air pathway inclue the nose, pharynx, larynx, trachea and the bronchi.
• Anatomical structures that can be found are associated with the lungs, ribs & intercostal muscles, pleural muscles and the diaphragm.

Airway Pathway

• Nose: The entry point for air.
• Nasal Cavity: Where air is conditioned
• Nasopharynx: Connects nasal cavity to larynx
• Larynx: houses vocal cords
• Trachea: The main airway to the lungs.
• Bronchus: Branches off into each lung.
• Bronchioles: Smaller branches within the lungs.
• Alveolar Ducts: Connect to alveoli
• Alveoli (air sacs): Where gas exchange occurs

The Nose

• Each cavity is bounded by spongy bone, hyaline cartilage, and skeletal muscle.
• The posterior part contains the respiratory area, covered by pseudo-compound ciliated epithelium with goblet cells.
• Cilia and mucus trap and remove dust and pathogens from the air.
• Cilia also move mucus down to the pharynx, where. it is swallowed.

Nose Anatomy

• Nasal cavity looks like a pyramid, and is divided into two nasal passages.
• Nasal passages are covered by a moist mucous membrane.
• Air is made moist & warm to protect the lungs.
• Fine hairs in the nose filter dust particles.

Nose Functions

• Provides an airway for respiration.
• It moistens and warms air entering the respiratory system.
• It filters and cleans inspired air.
• It is a resonating chamber for speech.
• It detects odor in the air stream.

Pharynx

• The pharynx is an organ in the respiratory system.
• The pharynx is part of the throat behind the mouth and nasal cavity, above the esophagus and larynx.
• It connects the nasal cavity with the larynx and is lined with pseudo compound ciliated cells with goblet cells.
• It measures 2 to 3 cm wide and 3 to 4 cm long.
• It provides a passage for air during breathing.
• The nasopharynx remains open during muscle flex, to ensure respiratory functions are not impaired .

Pharynx Anatomy

• Consists of nasopharynx, oropharynx, and hypopharynx.
• The nasopharynx is the upper part of the throat behind the nose.

Larynx

• The larynx is commonly called the voice box.
• The larynx houses the coal folds (vocal cords), which are essential for phonation.
• The Larynx connects pharynx with the trachea.
• The Larynx has two functions which are prevention of food and fluid from entering the respiratory passages and Production of voice (is also known as the voice box.)
• The Larynx is lined with pseudo-compound ciliated epithelium with goblet cells in between , except the vocal chords and the anterior surface of the epiglottis which are covered only with compound squamous epithelium.
• It is formed by elastic cartilage and also the epiglottis.

Trachea

• It is a tube around 20 cm long.
• It divides below into two primary bronchi.
• It is kept open by approximately 20 c-shaped or incomplete rings of hyaline cartilage.
• The trachea features incomplete rings of hyaline cartilage in order to allow the trachea to collapse slightly to allow food to pass down the esophagus
• The trachea is lined with pseudo compound ciliated cells and the trachea epithelium lining produces mucus that traps dust, cilia moves the mucus towards the pharynx in order to be swallowed and digested.
• Provides a clear airway to enter and exit the lungs.

Bronchi

• The trachea (windpipe), conducts inhaled air into the lungs through its tubular branches, called bronchi.
• The bronchi divides into smaller branches (bronchioles), becoming microscopic.
• The bronchioles eventually end in clusters of microscopic air sacs called alveoli.
• Primary bronchi are located in the upper portion of the lungs, their secondary bronchi near the center, with tertiary bronchi near the bottom, above the bronchioles.
• No gas exchanges happen in the bronchi.
• The main function of the bronchi and bronchioles is to carry air from the trachea into the lungs.
• The smooth muscle tissue in walls helps to regulate airflow into the lungs.
• The bronchi and bronchioles use their epithelial lining to trap and move dust and other contaminants away from the lungs.

Lungs

• The human lungs are the main organs, pair of big spongy organs, responsible for gas exchange.
• There are two lungs found at each side in the thoracic cavity.
• The right lung has three lobes and the left lung has two lobes.
• Each lung is formed of the bronchial tree, alveolar ducts, alveoli, and blood vessels.
• The lung contains about 300,000,000 alveoli, primarily for gases exchange.
• Each lung consists of the bronchial tree, alveolar ducts, alveoli approximately 300 millions for gases exchange with the blood and blood vessels.
• Located in the thoracic cavity their gasses can exchange in the blood here.

Alveoli

• Alveoli are the functional units of the lungs.
• Alveoli permit gas exchange between the air in the lungs and the blood in the capillaries of the lungs.
• Each alveolus is a hollow, cup-shaped cavity surrounded by many capillaries.
• At the end of each alveolar duct there are a number of alveoli, where surfactant is produced.
• Individual sacs group together.

Functionality of Alveoli

• Gas exchange of oxygen and carbon dioxide happens.
• Oxygen from the inhaled air diffuses through the capillarys in the alveoli, into the red blood cells.
• Oxygen is carried by the blood to the body tissues, carbon dioxide produced returns to the lung.
• Walls are extremely thin.
• Surface area is large.
• Gases can dissolve due to fluid lining.
• Surrounded by capillaries.

Ribs

• The function is to protect the lungs, solidify the thoracic region and aid ventilation.
• The intercostal muscles are 22 tiny muscle pairs found between the ribs.
• Consists of 11 pairs of internal intercostal and 11 pairs of external intercostal.

Diaphragm

• The diaphragm controls breathing and separates the chest cavity from the abdominal cavity.
• The diaphragm, is dome-shaped muscle at the bottom of the lungs.
• Various openings allow the esophagus, nerves, aorta, and vena cava to pass between cavities.

Summary of Structures

• The nasal cavity consists of spongy bone, hyaline cartilage and skeletal muscle.
• Larynx is made up of elastic cartilage and consists of nine cartilages, three unpaired (Thyroid, Cricoid, Epiglottis), three paired (Arytenoid, Corniculate, Cuneiform) which support the mammalian larynx and form its skeleton.
• The trachea is lined with pseudo compound ciliated epithelial cells and Made of incomplete rings of hyaline cartilage.

Respiration Types

• Internal and cellular respiration occurs in the mitochondria of cells, with its main function being to release energy.
• Two types of internal/cellular repiration are aerobic and anaerobic.
• Aerobic requires oxygen and releases a lot of energy:
  • C6H12O6 + 602 → 6H2O + 6CO2 + ATP
• Anaerobic does not require oxygen:
  • C6H12O6 → lactic acid + ATP
• ATP which forms during the 2 processes is broken down and hydrolyzed to form ADP + phosphoric acid, and releases energy also.
• External respiration is the process of ventilation with its main function being to take in oxygen from the air and return carbon dioxide.

Ventilation

• The human respiratory system has a tube leading from the nose and mouth down to two lungs, with millions specializes cells called alveoli that filter oxigen from the air.
• Its a process divided into two parts, inhalation and exhalation.

Inhalation

• It is the intake of air through changes of pressure and volume, due to the movement of muscles (intercostal muscles, the diaphragm) and the movement of the rib cage.
• Diaphragm relaxes and goes downwards, the inner intercostal relaxes, and the outer intercostal muscles contract.
• The ribcage goes outwards and upwards, increasing the volume of the lungs, decreasing the pressure inside the lungs, thus making air (gas) move from a region of high pressure (atmosphere) to a region of low pressure.

Exhalation

• It's the process of releasing air (gas) from the inside the lungs to the atmosphere
• The diaphragm contracts and goes upwards, decreasing the volume of the lungs
• The inner intercostal contracts, the outer intercostal muscles relax and the ribcage goes inwards and downwards.

Ventilation control

• Breathing is controlled by the expansion and contraction of the diaphragm.
• Normal breathing consists of the diaphragm contracting about 12-20 times per minute.

Air Flow Through the Respiratory System

• Air, warmed and filtered, enters the body through the nose before passing through the nasal cavity into the pharynx.
• The air passes over the larynx, then travels in the trachea.
• Once the air passes the larynx, it enters into the bronchi, into the lungs.
• Bronchi are lined with ciliated epithelial and mucus producing cells.
• Bronchi branch into bronchioles which terminate into alveoli.
• Alveoli have a network of capillaries to complete the respiration process.

Transport of Oxygen by Blood

• At rest, the body requires around 50,000,000 of oxygen per minute.
• Oxygen enters blood capillaries and unites with haemoglobin to form:- Hb+O2→ HbO₂
• The reaction is reversible therefore can go in either direction, right is for lungs, left for tissues to release oxygen.

Gas exchange and Haemoglobin

• Process is controlled by oxygen levels.
• Carbon dioxide also plays a role.
• Concentration levels control the formation or the breakdown of oxyhaemoglobin in lungs and tissue.
• When carbon dioxide reacts with water it forms the carbonic acid (H₂CO₃) which increases the acidity of the blood decreases the oxygen carrying the capacity of the haemoglobin.

Transport of Carbon Dioxide by Blood

• Some carbon dioxide is carried in loose chemical union with haemoglobin as carbaminhaemoglobin.
• Small amounts occurs as carbonic acid, but H2CO3 is converted into bicarbonates of sodium or potassium.
• Pass from tissues to the blood ( simple diffusion from high to low) to the lungs.
• Converting carbon dioxide into carbonic acid (and vice versa) is catalyzed by an enzyme called carbonic anhydrase.

Vein Note

• All veins inside the body take deoxygenated blood except one which is the pulmonary vein.
• All arteries inside the body take oxygenated blood except one which is the pulmonary artery.

Respiratory System Illnesses

• Emphysema: Usually caused from extended tobacco use, the lungs produce excessive mucus and the alveoli are damaged.
• Lung Cancer: Lung cancer is commonly contracted a result of tabacco smoke and cigarettes and is caused by the development of abnormal cell growths which line the walls of the bronchi, symptoms include, shortness of breath, and chest pain.
• Asthma: Asthma is when the chronic inflammation of the lung, which causes the airways to constrict making the flow of blood difficult. Management of asthma includes avoidance of triggers.
• Bronchitis: In bronchitis the membranes lining the larger bronchial tubes become inflamed and excessive mucus is produced.

Explore the organs essential for ventilation and respiration, focusing on their anatomy and histology. Understand both internal (cellular) and external respiration processes. Key areas include gas exchange and blood transport of gases, alongside common respiratory diseases.