Respiratory system structure and function Flashcards
Explain the the anatomical structure of the respiratory system.
The respiratory system consists of the upper and lower. The upper includes: nose, nasal cavity, paranasal sinuses and paraynx. The lower includes: larynx, trachea, bronchi, bronchioles, and alveoli. It can be further sub divided into the conducting and respiratory portions. All of it is the conducting portion apart from the terminal bronchi and the alveoli which are the respiratory portion. This is where the gas exchange takes place. Here the cells are simple squamous epithelial to allow for quick and efficient gas exchange. The respiratory mucosa differs throughout the respiratory tract to suit its function. In the trachea and bronchi the lamina propria contains goblet cells that secrete mucus to line the tract and help to trap pathogens and dirt. The mucous escalator describes the process of cillia wafting these pathogens and dirt towards the parynx to be swollen.
Type II alveolar cells or septal cells secrete surfactant. Type I cells are alveolar epithelial cells.
The vasculature within the nasal tracts allows for the warming, cooling, humidifying and dehumidifying of the air before it enters the brocholies and exists.
The pharynx consists of nasopharynx (pseudostratified colunmar cilliated epithelial), oropharynx (stratified squamous) and the laryngopharynx (stratified squamous epithelial protect against abrasion ). Superior to inferior respectively.
The air flows from the pharynx into the larynx via the epiglottis. the larynx has several main types of cartilage starting with the thyroid cartilage that is superior to the cricoid cartilage.
Trachea start of the air way with C shaped cartilage incomplete cartilage rings around the it around 15-20. To ensure airway patency. An elastic ligament and the trachealis muscle, a band of smooth muscle, connect the ends of each tracheal cartilage. Contraction of the trachealis muscle alters the diameter of the trachea so that the volume of air flow can be altered. This is controlled primarily by the sympathetic division of the ANS. Sympathetic stimulation increases the diameter.
This then divides into two main bronchus. The junction where the trachea and the two primary bronchi branch is reinforced by a cartilage plate called the carina. The right is steeper in angle and has a larger diameter than the left which projects more to the side slightly. These still have the rings of cartilage. They are called the primary bronchus.
The left divides into two called the lobe bronchus. Whereas the right divides into three lobes. These air ways get progressively smaller when they pass the hilus where the vessels and nerves innervate the lungs. These are called the secondary bronchi or the lobar bronchi. This is called the bronchi tree. The tertiary bronchi supplies air to a single bronchi pulmonary segment. In the secondary and tertiary bronchi the cartilage because less and less and forms plates, and more smooth muscle is present. Then down to the broncholies and terminal bronchioles. These passages are the conducting airways.
The smallest bronchioles have blebs in there walls which are called alveoli, that go into alveolar ducts then into air sacs which are clusters of alveoli. They increase the surface area of the bronchiole passages. They are described as respiratory bronchioles as the lining of the structure here is thin enough to allow for diffusion of gases. There is elastic tissue in the alveoli that allows it to contract. Sympathetic activation of the ANS causes dilation of the the airway diameter increasing airflow. The respiratory membrane is a composite structure consisting of three parts: the squamous epithelial cells lining the alveolus, the endothelial cells lining an adjacent capillary, the fused basal laminae that lie between the alveolar and endothelila cells.
There is about 21% of O2 and 0.04% CO2 in air we breath in and 16% O2 and 4% CO2 in air we breathe out. The branch of the pulmonary artery is carrying blood with Ox saturation of about 75% next to the alveoli. CO2 will be high. The pulmonary branch will further break down into pulmonary capillaries. There is a higher alvelor O2 then blood O2, therefore will move down its concentration gradient and mostly become associated with Hb in RBCs. Therefore the O2 in the pulmonary vein will be at high sat 95%-100%, to take to the heart. The same happens in reverse for CO2 as it is highest in the blood and lowest in the alveolar and so diffuse down its concentration gradient into the alveoli out of the blood.
The muscles inbetween the ribs are the intercostal muscles. There is both internal and external intercostal muscles. These form the thoracic wall.
The diaphragm lies below the thoracic cavity and above the abdomen. The ribs meet medially at the sternum. The external intercostal muscles contract pull the ribs up and out. (Active muscular contraction).
To facilitate inspiration the chest wall moves up and out and the diaphragm moves down and flattens. (contraction). Interplumonary volume increased, decrease pressure. Causes a pressure gradient between intraplumonary space and external environment resulting in relatively negative pressure inside lungs and so air is sucked in from the external environment through the airways.
Breathing out: relaxation of muscles ribs down and in diaphragm concave domed. Passive recoil process. Volume decreased, pressure increase to greater than the external environment. Air forced out of the lungs through the airways. This is Boyles Law.
Pleural membranes:
External pleural membrane around the inside if the thoracic cavity. Adherent to the inside of the thoracic cage.
Parietal membrane also lines the surface of the diaphragm. It is fixed. Each lung is surrounded by its own pleural membrane.
The visceral pleural membrane is adhered onto the surface of the lung. These two membranes are sucked together there is a negative pressure between the two.There is seros fluid between the two. Because of this when the chest wall moves the lung will move with it.
Control of the respiratory system
If diffusion rates at the peripheral and alveloar capillaries become unbalanced, homeostatic mechanisms intervene to restore equilibrium. This involves changes of blood flow and oxygen transport that are regulated at the local level, changes in the depth and rate of respiration under the control of the brain’s respiratory centres.
Local regulation of gas transport and alvelolar function:
When tissues become more active the interstitial P02 falls and PC02 rises. This increases the difference between the partial pressures in the tissues and the arriving blood so more O2 is delivered and CO2 taken away.
Increased CO2 also causes muscles in the local blood vessels to relax allowing for increased blood flow to the surround cells. Add more from the book page 861
However at the alvelolar the opposite occurs.
The respiratory centers of the brain:
The brain regulated the involuntary and voluntary control of the respiratory system. the involuntary control is via sensory information that arrives from the lungs, portions of the respiratory tract and other sites.
Voluntary control is from activity in the cebral cortex affecting activity in the respiratory centres in the medulla oblongata and pons or the motor nerons in the spinal cord that control respiratory muscles.
Respiratory reflexes:
Voluntary control of respiration:
Describe gas exchange and the different laws associated with the lungs?
Dalton’s Law: atmospheric pressure is 760 mmHg
in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases.
Henery’s Law:At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.
What is compliance?
The compliance of the lung is an indication of their expandability. The lower the compliance the greater the force required to fill and empty the lungs. The connective tissue, level of surfactant and the mobility of the thoracic cage all affect the compliance of the lungs.
What are the main functions of the respiratory system?
Providing a large surface area for exchange of gases between the air and circulating blood.
Moving air to and from the exchange surfaces of the lungs.
Depending the respiratory system from pathogens from the environment,
Providing sound for communication and olfactory senses.
The capillaries of the lungs indirectly assist in the regulation of blood volume and blood pressure, through the conversion of angiotensin I to angiotensinII by ACE.
Lung volumes
breaths per minute are 12 and volume 500ml so respiratory minute volume is around 6L per minute.
Resting tidal volume Expiratory reserve volume residual volume inspiratory reserve volume insiratory capacity functional residual capacity vital capacity total lung capacity
Blood departs the alveloi with 100mmHg O2 and 40mmHg CO2. At the pulmonary vein O2 is 90mmHg.
How is respiratory rate controlled
Signals sent to the medulla oblongata to dorsal and ventral respiratory group (dorsal only for quiet breathing). Pass to higher brain centers. Ventral used in addition in forced breathing nerves inervate accessory muscles that are used as well as respiratory muscles.
The receptors respond much more to CO2 that O2 the O2 has to drop to arounf 60mmHg before a response occurs where as Co2 only need to increase by 10% and increased respiration is stimulated.
Hypercapnia hypoventilation
Hypocapnia due to hyperventilation
