Block Theory 3 Flashcards
Explain the respiratory system.
The respiratory system facilitates breathing and allows the body to acquire oxygen, which is required for metabolic function and cell survival. This system is made up of many organs that contribute to the conduction of air to and from the lungs, as well as gas exchange within the lungs.
What are the cyclic phases of breathing?
- Inspiration: draws oxygen rich air into the lungs.
- Expiration: forces oxygen poor air out of the lungs.
What are the functions of the respiratory system?
The respiratory system not only provides the structures for mechanical breathing, but also contributes to the functional mechanisms of respiration and immunity.
Gas exchange: involves the movement of gases across membranes. External respiration is the exchange of gas between the air and blood, where inspired oxygen moves across the cellular membranes of the alveolus of the lung and its associated capillaries into the blood, while carbon dioxide, moves in the opposite direction and out of the body through expiration. Internal respiration is a similar, exchanging gases between the blood and cells of the body.
Gas conditioning: gases entering the lungs need to be warmed and cleansed to prevent damage to the lungs. The conditioning of gases occurs in the nasal cavities and paranasal sinuses where air is swirled around to become warmed and humidified. Inhaled air is cleansed of particulate matter, through contact with the mucosal lining of respiratory epithelium.
Sound production: singing or speech, occurs by forceful expiration of air through the vocal cords in the larynx, causing them to vibrate. Different tensions of the vocal cords produce different sounds with help from the teeth, lips, and tongue.
Olfaction: olfactory epithelium covers the top of the nasal cavity with receptors for the sense of smell located within. When air is inhaled, airborne molecules dissolve in the mucus which lines the cavity and stimulates the receptors. Signals from these receptors travel to the brain through the olfactory nerve resulting in a sense of smell.
Defense: many airborne molecules and microbes can cause disease. The respiratory system has a line of defence against these molecules that cause infection. Course hairs of the nostrils, the ciliated cells of the respiratory epithelium, and the mucus lining help to trap particles and microorganisms from entering the nose and respiratory system.
What chamber of the heart does the deoxygenated blood exit from to enter the lungs?
The right ventricle
What chamber of the heart does oxygenated blood re-enter after exiting the lungs?
The left atrium
Discuss the respiratory tract epithelium.
RTE plays a large part in the defence of this system and lines most of the surfaces from the nasal cavity down to the terminal bronchi.
Pseudostratified ciliated columnar epithelium: the epithelium of the respiratory tract is pseudostratified, meaning that all cells are attached to the basal lamina, but only some reach the surface. The apical surface of the epithelium is covered in cilia, which are small finger like projections extending from the cell to increase surface area for conditioning air. These cilia also function to trap particles and microorganisms caught in mucus, and sweep them out of the respiratory tract.
Goblet mucus cells: found interspersed throughout the pseudostratified epithelium to produce mucus that forms a protective layer over the epithelium and traps particulate matter that may be inhaled. It also provides moisture to humidify the air.
What are the regions of the respiratory system?
Conducting portion: functions to transfer inhaled air from the outside world to the lung tissue, also conducting air from the lungs to the outside world. This is where humidification and trapping of debris occurs. No oxygen is absorbed into the blood in this region as the walls of the organs are too thick.
Respiratory portion: functions to transfer gases between the lungs and pulmonary capillaries. The pulmonary capillaries are the terminal structures within the lungs that have walls thin enough to facilitate the movement of gases from air to blood and vice versa.
Discuss the paranasal sinuses.
Paranasal sinuses are collection of air filled spaces within the bones of the skull communicating with the nasal cavity. The sinuses aid in the conditioning of air, defense, and act as resonance chambers for speech.
Paranasal sinuses are named after the bones of the skull that contain them. These include the frontal sinus, maxillary sinus, ethmoid sinus, and sphenoid sinus.
Paranasal sinuses are lined with respiratory tract epithelium for defence and conditioning.
Discuss the nasal cavity.
The nasal cavity is the first line of defence against invading pathogens, trapping them in coarse hairs and mucus. Air enters the vestibules of the nostrils and is passed into the nasal cavity where it is conditioned.
What are the nasal cavity boundaries?
The nasal cavity is surrounded by boney structures that create the 6 boundaries of the cavity.
Roof: the ethmoid bone
Floor: the hard palate
Medial wall: the nasal septum, composed of the vertical bones in the skull, separating the two halves of the nasal cavity
Lateral wall: contain structures known as nasal conchae that create turbulence in the air for conditioning and catching debris
Anterior: made of nares, the opening between the nose and nasal cavity
Posterior: opening to the nasopharynx (choanae), where the nasal cavity connects to the pharynx
Discuss the nasal cavity Histology.
The nasal cavity is mostly covered in RTE because if it’s role in protection and the conditioning of air. However, the roof of the nasal cavity is lined with olfactory epithelium which contains sensory receptors for smell. Olfactory epithelium is composed of pseudostratified ciliated columnar epithelium and bipolar olfactory receptor neurons.
Discuss the pharynx
The pharynx is a muscular tube that connects the nasal cavity in the larynx in the respiratory system. It also connects the oral cavity with the esophagus in the digestive system.
Nasopharynx: superior aspect of the pharynx
Oropharynx: middle aspect of the pharynx, acting as part of both the respiratory and digestive systems, passing air from the nasopharynx and food from the oral cavity into the laryngopharynx
Laryngopharynx: inferior aspect of the pharynx involved in both the digestive and respiratory systems, passing food and air into the respective systems
What is a Histology of the pharynx?
The nasopharynx is mostly RTE, because of its main respiratory function, while the oropharynx and laryngopharynx are lined with stratified squamous epithelium for durability when swallowing food.
When on an airplane, what is a good solution to equalize pressure in the middle ear?
A good solution is to swallow forcefully. The part of the pharynx that is associated with this is the nasopharynx.
Discuss the larynx
The larynx is the organ that produces sound, it is also known as the voicebox. It is made up of cartilage, ligaments, and associated muscles to serve its purpose. The larynx sits anterior to the esophagus, connecting the pharynx with the trachea and preventing food from entering the trachea.
What are the cartilages that make up the larynx?
Many cartilages serve to protect, attach, and aid in the function of the vocal cords.
Epiglottis: spoon shaped elastic cartilage that prevents food from passing into the trachea. During swallowing, the epiglottis flips downwards, and covers the opening of the trachea.
Thyroid cartilage: shield shaped hyaline cartilage that provides attachment for muscles as well as the vocal cords.
Cricoid cartilage: complete ring of hyaline cartilage that is narrow anteriorly and broad posteriorly, functioning as an attachment for muscles and vocal cords.
What are vocal cords?
Vocal cords are small ligaments attach to the laryngeal cartilages that vibrate when air is forced out of the lungs. When they vibrate, sound is produced. Different sounds can be made by altering the tension on the cords. True vocal cords are protected by a membranous flap, called the false vocal cords.
Discuss the trachea
The trachea extends from the larynx to the level of T4/T5 where it splits at the carina. The function of the trachea is the conduction of air to the lungs. The trachea is made up of 15 to 20 C-shaped cartilaginous rings which are incomplete posteriorly and function to keep the airway open. These rings are connected posteriorly by the trachealis muscle.
What is the Histology of the trachea?
Mucosa: RTE to clear debris that make it into the lower respiratory tract
Submucosa: made up of loose connective tissue containing larger vessels and nerves, as well as mucus, secreting glands.
Adventitia: outer layer of connective tissue surrounding the trachea and enclosing the C-shaped cartilaginous rings made of hyaline cartilage. These rings make the trachea flexible and durable for when organs in the thoracic cavity shift with breathing.
What type of cartilage are the cartilaginous rings of the trachea?
Hyaline
What are primary bronchi?
The left and right primary bronchi have the same functional and histological features as the trachea. Each primary bronchus enters its respective lung on the medial side at the hilus. The right primary bronchus is wider, shorter, and more vertical than the left primary bronchus.
Discuss the end of the conducting portion
The end of the conducting portion is characterized by bronchi dividing into smaller and smaller tubes. They move from a larger diameter, thick walled tube to a smaller diameter, thin walled tube for gas exchange. There’s also a corresponding change in histology as you move down the tree.
What is the order in which air travels from the environment to the end of the conducting portion of the respiratory system?
Nasal cavity, pharynx, larynx, trachea, primary bronchi, secondary bronchi, tertiary bronchi, terminal bronchioles.
What is the respiratory portion?
The respiratory portion serves to allow for gas exchange between air and blood. It is important to cells in the body need to absorb oxygen and expel carbon dioxide to survive. At this level of the bronchial tree, the walls of the remaining structures are one cell layer thick and gases are able to cross the membrane easily.