The Respiratory System

Lecture 18

The Respiratory System

·  Overview of the Respiratory System

o  Functions:

§  Provides ______ and carbon dioxide exchange

§  Serves for ______ and other vocalizations (laughing, crying)

§  Provides the sense of smell, which is important in social integration, food selection, and avoiding danger (such as spoiled food or a gas leak)

§  Breathing creates blood pressure gradients between the thorax and abdomen that promote the flow of ______ and venous blood

§  Taking a deep breath and holding it contracts the abdominal muscles helps to expel abdominal contents during urination, defecation, and ______

o  Divisions:

§  Conducting division

·  Passages that serve only for airflow

·  Nostrils through ______

§  Respiratory division

·  Consists of the ______ and other distal gas-exchange regions

·  The Upper Respiratory Tract

o  The Nose

§  The nose has several functions

·  It warms, ______, and humidifies the air

·  It detects odors in the airstream

·  It serves as a resonating chamber that amplifies the voice

§  It extends from a pair of anterior openings called the nostrils (external nares) to a pair of posterior opening called the posterior ______ (choanae)

§  The nasal cavity is divided into right and left halves called nasal ______

§  The separation between the right and left nasal fossa is the nasal septum

§  The facial part of the nose is shaped by ______ and hyaline cartilage

·  The superior part is shaped by the nasal bones and maxilla

·  The inferior part is shaped by lateral cartilage (below the nasal bones) and alar cartilage (surrounding the nostrils)

§  The nasal cavity begins with a chamber called the nasal ______

·  This space is lined with stratified squamous epithelium like the facial skin, and has stiff ______ (hairs) that block insects and large airborne particles from the nose

§  The nasal septum:

·  The vomer forms the ______ part

·  The perpendicular plate of the ethmoid bone supports the superior part

§  Much of the space inside the nasal cavity is occupied by the nasal conchae (superior, middle, and inferior)

·  They project from the lateral walls towards the septum

·  Beneath each of the conchae is a narrow ______ passage

·  The narrow space between the conchae forces most of the air to come in contact with the mucous membrane

o  Most dust in the air sticks to the mucus

o  The air picks up moisture and ______ from the mucosa

o  The conchae clean, warm, and moisten the air

·  The rest of the nasal cavity is covered in ciliated pseudostratified respiratory mucosa

o  It consists of goblet cells that secrete mucus and ciliated cells which drive the mucus toward the posterior ______ and into the pharynx

o  Pollen, dust, and other inhaled particles stick to the ______, and lysozyme in the mucus destroys bacteria

o  The Pharynx

§  The pharynx is a muscular funnel extending from the choanae to the larynx

§  It has three regions

·  The ______ lies posterior to the choanae

o  It receives the auditory tubes from the middle ears

o  It houses the pharyngeal tonsil

o  Inhaled air turns downward ______ degrees

§  Relatively large particles generally cannot make that turn and collide with the posterior wall, where it sticks to the mucosa near the tonsil

·  The oropharynx is a space between the soft palate and the root of the ______

o  It extends inferiorly as far as the hyoid bone

o  It contains the lingual and ______ tonsils

·  The laryngopharynx begins at the level of the hyoid bone

o  It passes inferiorly and dorsal to the larynx and ends at the opening of the esophagus, at the level of the ______ cartilage of the larynx

o  The Larynx

§  The larynx is the voicebox

§  It is a cartilaginous chamber about 4 cm long

§  Its primary function is to keep food and drink out of the airway

§  It also produces sounds in many animals, and ______ in humans

§  The glottis is the superior opening of the larynx

·  The epiglottis is flap of tissue that guards the glottis

o  At rest, the epiglottis stands almost ______

o  During swallowing, the extrinsic muscles of the larynx pull the larynx upward toward the ipiglottis, and the tongue pushes the epiglottis downward toward to meet it

o  The epiglottis directs food and drink into the esophagus dorsal to the airway

§  The larynx consists of nine cartilages

·  The epiglottic cartilage is the most ______ cartilage

o  It’s a spoon-shaped cartilage in the tissue of the epiglottis

·  The ______ cartilage is the largest cartilage

o  It’s named for its shield-like shape

o  It broadly covers the anterior and lateral aspects of the larynx

o  The Adam’s apple is an anterior peak of the thyroid cartilage

§  Testosterone stimulates the growth of the cartilage, so it is larger in ______

·  The cricoid cartilage is inferior to the thyroid cartilage

o  It’s ring-like in construction and connects the larynx to the ______

·  The arytenoid cartilages are posterior to the thyroid cartilage

·  The corniculate cartilages are a pair of little horns at the upper ends of the ______ cartilages

·  The cuneiform cartilages support soft tissues between the arytenoids and the epiglottis

§  The interior wall of the larynx has two folds on each side that stretch from the thyroid cartilage in front to the arytenoid cartilage in the back

·  The vestibular folds are the superior pair

o  They close the ______ during swallowing

·  The vocal folds are the inferior pair

o  They produce sound when air passes between them

o  Intrinsic muscles control the vocal cords by pulling on the ______ and arytenoids cartilages, causing the cartilages to pivot

o  When pulled taut, they produce ______ pitch

·  The Lower Respiratory Tract

o  The Trachea

§  The windpipe is a tube about 12 cm long and 2.5 cm in diameter

§  It is supported by rings of hyaline cartilage

§  The inner lining is pseudostratified columnar epithelium

·  It’s composed of mucus-secreting ______ cells, ciliated cells, and short basal stem cells

·  The mucus traps inhaled particles, and the cilia drives the debris-laden mucus toward the pharynx where it is ______

o  The Bronchi

§  The primary bronchi are forks branching to the right and left from the ______

o  The Lungs

§  Each lung is somewhat conical with a concave base resting on the diaphragm and a blunt peak called the ______ projecting above the clavicle

§  The costal surface is the portion pressed against the ribcage

§  The mediastinal surface is the portion the faces medially

§  The hilum is a slit in the ______ surface through which the primary bronchus, blood vessels, and nerves enter the lung

§  The right lung is shorter than the left because the liver rises higher on the right

·  It has three lobes (superior, middle, and inferior)

§  The left lung is taller but narrower

·  On the medial surface, there is a cardiac impression, where the ______ presses against it

·  It has only two lobes (superior and inferior)

§  Within each lung, there is a bronchial tree

·  Branching from the trachea into the two lungs there are primary bronchi

·  After entering the lung the primary bronchus branches into one ______ bronchus for each lobe of the lung

·  Each secondary bronchus divides into tertiary bronchi

§  Bronchioles are continuations of the airway that lack supportive cartilage and are 1 mm or less in diameter

·  Each bronchiole divides into terminal bronchioles, the final branches of the conducting division

·  Each terminal bronchiole gives off two or more smaller ______ bronchioles

§  Each respiratory bronchiole divides into thin-walled passages called alveolar ducts.

§  The alveolar ducts end in alveolar ______ which are grapelike cluster of alveoli

·  There are ______ networks around each alveolus, for the exchange of CO2 and O2

o  The Pleurae

§  The surface of the lung is covered by a serous membrane called the visceral pleura

§  At the hilum, the visceral pleura turns back on itself and forms the ______ pleura

§  The space between the parietal pleurae and visceral pleurae is called the pleural cavity

§  The pleural cavity contains a slippery pleural ______

§  The pleurae and pleural fluid have 3 functions

·  Reduction of friction

o  The fluid acts as a ______ that enables the lungs to expand and contract with minimal friction

·  Creation of pressure gradient

o  During inspiration (inhalation) the rib cage expands and draws the parietal pleura outward along with it

o  The visceral pleura clings to the parietal pleura, and since the visceral pleura is the lung surface, its outward movement ______ the lung

·  Compartmentalization

o  The pleurae, mediastinum, and pericardium compartmentalize the thoracic organs and prevent ______ of one organ from spreading easily to neighboring organs

·  Neuromuscular Aspects of Respiration

o  Inspiration

§  The ______ does most of the work of inspiration (inhalation)

·  It’s controlled by the phrenic nerves

·  It drops about 1.5 cm in quiet inspiration

·  It drops up to 7 cm in forced inspiration (______ breathing)

§  The external intercostals muscles are also important in inspiration

·  They are innervated by the intercostal nerves

·  The scalenes fix the first pair of ribs and the external intercostals lift the remaining ribs

o  They swing up and out, ______ the volume of the thoracic cavity

o  It creates a pressure gradient that draws air into the lungs

·  Deep inspiration is further aided by the pectoralis minor, ______, and erector spinae muscles

o  Expiration

§  Normal expiration is achieved by the elasticity of the lungs and thoracic cage

·  As structures recoil, the thoracic cage diminishes in size, the air pressure in the lungs rises above the atmospheric pressure, and the air flows ______

·  The only muscular effort involved in expiration is a braking action to keep the lungs from recoiling too ______

§  Forced expiration (to blow out the candles) employs internal intercostals and abdominal muscles

·  The internal intercostals muscles depress the ribs

·  The internal and external abdominal obliques, transverse abdominis, and rectus abdominis compress the abdominal organs, raise the intra-abdominal pressure, and push the viscera up against the ______

o  Respiration Centers of the Brainstem

§  Rhythm of unconscious breathing is caused by nuclei in the reticular formation of the medulla oblongata and pons

§  In the medulla, these nuclei include:

·  inspiratory neurons of the inspiratory center which fire during ______

·  expiratory neurons of the expiratory center fire during expiration

§  The pons contains respiratory nuclei

·  The lower pons has an ______ center whose function seems to prolong inspiration

·  The upper pons has a pneumotaxic center which sends a continual stream of signals to the inspiratory center of the medulla

o  It regulates the duration and ______ of each breath

§  Respiratory centers receive input from several sources

·  Chemoreceptors respond to pH and CO2 and O2 concentrations of the blood and cerebrospinal fluid

o  Peripheral chemoreceptors are found in the aortic bodies and ______ bodies

o  Central chemoreceptors are found close to the surface of the medulla oblongata

·  Stretch receptors in the bronchial tree monitor inflation of the lungs

·  The vagus nerves transmits singals from the respiratory ______ when they are stimulated by irritants in the airway

·  Higher brain centers allow for conscious control over breathing