Lecture 14



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

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