Ch. 22 - The Respiratory System

22.1 Anatomy of the Respiratory System

Variable affecting the efficiency of gas exchange in the alveolus - will be asked abt on the quiz

Oxyhemoglobin disassociation curve - may be questions on quiz

Overview

• Respiration

  • can mean ventilation of the lungs (breathing) OR

  • use of oxygen in cellular metabolism

• Functions of the respiratory system

  • Gas exchange: provides oxygen & CO2 exchange btw blood & air

  • Communication: serves for speech and other vocalization

  • Olfaction: sense of smell

  • Acid-Base balance: controls pH of the body fluid

  • Blood Pressure Regulation: help synthesize angiotensin II, a hormone that regulate BP

  • Platelet Production: half the blood platelets is made by megakaryocytes in the lungs

  • Blood and Lymph Flow: promote flow of lymph and venous blood bc breathing creates pressure gradients btw thorax & abdomen

  • Blood Filtration: filter small blood clots - preventing obstruction

  • Expulsion of abdominal contents: breath-holding & abdominal contraction help to expel abdominal contents during urination, defecation, & childbirth

• Air flows along a dead-end pathway consisting essentially of bronchi → bronchioles → alveoli

• Conducting zone: consisting of passage that serve only for airflow, essentially from nostrils through the major bronchioles

• Respiratory Zone: consists of the alveoli and other gas-exchange regions of the distal airway

• The Upper Respiratory Tract: nose through the larynx

• The Lower Respiratory Tract: Trachea through the lungs

The Nose

• Several functions: Warms, cleanses & humidifies inhaled air, detects oder, and serves as a resonating chamber that amplifies the voice

• Nostrils or Nares: anterior openings

• Posterior Nasal Apertures or choanae: posterior openings

• Facial part of the nose is shaped by bone & Hyaline cartilage

  • Superior half is supported by a pair small nasal bones medially and the maxillae laterally.

  • The inferior half is supported by the lateral and alar cartilages

  • The flared portion on each side of the lower end of the nose called the ala nasi, shaped by the alar cartilages and dense connective tissue

• Nasal Cavity - internal chamber of the nose

  • divides into right and left halves = nasal fossae

  • The dividing wall is a vertical plate called the nasal septum, which is composed of bone and hyaline cartilage

    • Vomer forms one-thrid

    • The perpendicular plate of the ethmoid forms the superior two thirds

    • Septal cartilage forms the non bony anterior part of the septum

  • Both the ethmoid & sphenoid compose the roof of the nasal cavity

  • paranasal sinuses and the nasolacrimal ducts of the orbit drain into the nasal cavity

  • Nasal cavity begins with a small dilated chamber called the vestibule just inside the nostril, bordered by the ala nasi

    • lined with stratified squamous epithelium, guard hairs, or vibrissae

  • Posterior to the vestibule, contained by three folds of tissue - the superior, middle, & inferior nasal conchae OR turbinates which project from the lateral walls toward the septum

    • Beneath each conchae are narrow air passages called a meatus

      • captures dust and air picks up moisture and heat from the mucosa - enables the the nose to cleanse, warm, & humidify the air more effectively

• The Mucosa

  • consists of ciliated pseudostratified columnar epithelium

  • Over most the mucosa, the epithelium is called the respiratory epithelium

  • goblet cells, secrete most of the mucus

  • brush cells - chemosensory

  • cilia beta in waves and dust & debris stick to the mucus

  • nasal mucosa has olfactory epithelium - concerned with sense of smell

  • in the olfactory mucosa, the lamina propria has large serous olfactory glands

  • Lamina propia contains large blood vessels that help warm the air

  • erectile tissue (swell body) - located in the inferior concha

    • every 30 to 60 minutes the erectile tissue on one side swells &Y restricts airflow through that fossa - keeps the engorged side time to recover from drying

      • This is called the nasal cycle

The Pharynx

• The pharynx is a muscular funnel extending from the posterior nasal apertures to the larynx

• Contains three regions: Nasopharynx, Oropharynx, & laryngopharynx

• The nasopharynx is distal to the posterior nasal apertures and superior to the soft palate - only passes air

• The oropharynx is the space btw the posterior margin of the soft palate and the epiglottis - pass air, food, & drink

• Laryngopharynx lies posterior to the larynx, extending from the superior margin of the epiglottis to the inferior margin of the cricoid cartilage - pass air, food, & drink

The Larynx

• Larynx is cartilaginous chamber, primary function is to keep food & drink out of the airway, but has evolved the additional role of sound production - the voice box

• superior opening guarded by the epiglottis

• Consists of 9 cartilages

  • First three - solitary & relatively large

    • Most superior, epiglottic cartilage, spoon shaped supportive of elastic cartilage

    • The largest, thryoid cartilage, is shield-like, has anterior peak called the laryngeal prominence or the Adam’s Apple, constitute the voice box

    • Cricoid cartilage, most inferior, constitute the voice box

  • Remaining cartilage - smaller & occur in three pairs

    • Arytenoid cartilages: Two, Posterior to the thyroid cartilage, attached to their upper ends is a pair of little horns which are the corniculate cartilages

    • Cuneiform cartilages: supports the soft tissues btw the arytenoids and the epiglottis

  • Thyroid membrane: broad sheet suspends the larynx from the hyoid bone below it

  • Cricothyroid ligament suspends the cricoid cartilage from the thyroid cartilage

    • cricothyrotomy

  • Cricotracheal ligament suspends the trachea from the cricoid cartilage.

• Contain two folds on each side

  • Vestibular folds - close larynx when swallowing

  • Vestibular ligaments - support the vestibular folds

  • Inferior vocal cords produce sounds when air passes btw them

    • contain vocal ligaments which are best suited to endure vibration and contact btw the cords

  • Vocal cords and the opening btw them are collectively called the glottis

The Trachea

• Or windpipe, anterior to the esophagus, supported by 16 to 20 C-shaped rings of hyaline cartilage

• These rings keep the trachea from collapsing when you inhale and create a partial vacuum in the airway

• The open part of the C, where it’s spanned by a smooth muscle. the trachealis

• Mucus in the trachea traps inhaled particles and the upward beat of the cilia drives the debris-laden mucus toward the pharynx, where it is swallowed - called the mucociliary escalator

• outermost layer of the trachea - adventitia - blends with the adventitia of other organs of the mediastinum

• Trachea ends at a fork called the tracheal bifurcation where it gives off right and left main bronchi - the lowermost tracheal cartilage has an internal median ridge called the carina

The Lungs and the Bronchial Tree

• Broad costal surface is pressed against rib cage

• mediastinal surface faces medially, toward the heart

• The mediastinal surface exhibits a slit called the hilum through which the lung receives the main bronchus, blood vessels, & lymphatics, and nerves

• These structures constitute the root of the lung

• 3 lobes of the lung nor are they symmetrical - right is shorter than the left

  • three lobes; superior, middle, & inferior

• On the medial surface, the left lung has an indention called the cardiac impression part of the this is visible anteriorly as a crescent shaped cardiac notch

• a deep groove called the horizontal fissure separates the superior & middle lobes, and a similar oblique fissure separates the middle and inferior lobes.

• oblique fissure separates the middle and inferior lobes

• the left lung has a only a superior and inferior lobe and a single oblique fissure

• The Bronchial Tree

  • branching system of air tubes called the bronchial tree

  • right main bronchus extends from the fork

    • gives off three branches - the superior, middle & inferior lobar (secondary) bronchi - one to each lobe of the lung

  • left main bronchus - slightly narrower and less vertical than the right

    • gives off superior and inferior lobar bronchi to the two lobes of the left lung

  • in both lungs the lobar bronchi branch into segmental (tertiary) bronchi

    • each one ventilates a functionally independent unit of lung tissue called bronchopulmary segment

    • Bronchioles are continuations of the airway that lack supportive cartilage

      • The portion of the lung ventilated by one bronchioles is called a pulmonary lobule

      • each bronchiole divides into 50 to 80 terminal bronchioles - the final branches of the conducting zone

      • each terminal bronchiole gives off two or more smaller respiratory bronchioles - beginning of the respiratory zone bc their alveoli participate in gas exchange

      • these further divide into 2 to 10 aveolar ducts

      • these further divide into alveolar sacs, which are clusters of alveoli arrayed around a central space called the atrium

• Alveoli

  • provide 70m² of gas exchange surface per lung - equal to the floor area of an American indoor handball court or a room 8.4m (25ft) square

  • Alveolus is a pouch about 0.2 to 0.5 mm in diameter

  • clustered like soap bubbles & have pores in their walls that directly exchange air with each other

  • functions of alveolar cells: repair alveolar epithelium when the squamous cells are damaged and they secrete pulmonary surfactant - a mix of phospholipids and protein that coats the alveoli and small bronchioles and prevents the bronchioles from collapsing when one exhales

  • alveolar macrophages (dust cells) are the most numerous and keep the alveoli free of debris

  • the barrier btw the alveolar air and blood is called the respiratory membrane

Pulmonary Circulation

• two blood supplies: pulmonary & systemic

• Pulmonary circuit

  • begins with the pulmonary trunk arising form the RV.

  • the trunk then divides right and left pulmonary arteries which then divide into lobar arteries, which supply the three lobes of the right and two lobes of the left

  • Serves to only unload CO2 and pick up fresh O2 from inhalation

    • The oxygenated blood returns to the heart by way of pulmonary veins

  • Lungs receive systemic blood supply from the bronchial arteries that arise from the thoracic aorta

    • lead to pleura, bronchi, bronchioles, and the larger pulmonary blood vessels. DO NOT LEAD TO AhLVEOLI

  • Bronchial veins drain this blood from the lungs into the azygos vein of the thorax

The Pleurae

• Serous membrane, the pleura, forms the surface of the lung

• There are two layers - visceral and parietal

  • the visceral forms the surface and extends even. into the fissues btw the lobes

  • The parietal pleura, adheres to the mediastinum, inner surface of the rib cage, and the superior surface of the diaphragm

• The space btw the parietal and visceral pleurae is called the pleural cavity

  • wraps around the lung

  • contains pleural fluid - only a potential space

• Pleurae and pleural cavity have three functions

  • Reduction of friction: acts as lubricant that enables lungs to expand and contract with minimal friction - can cause pleurisy which makes breathing painful

  • Creation of a pressure gradient

  • Compartmentalization: The pleurae, mediastinum, and pericardium

  • , compartmentalize the thoracic organs and prevent infections of one organ from spreading easily to neighboring organs

22.2 Pulmonary Ventilation

Overview

• Consists of a repetitive cycles of inspiration and expiration - one complete breathe (in and out) is called the respiratory cycle

• Two kinds - quiet & forced

  • Quiet respiration refers to relaxes, unconscious, automatic breathing

  • Forced means usually deep or rapid breathing

• Lungs do not ventilate themselves as they only contain smooth muscle

  • only adjusts the diameter of the airway and affects the speed of airflow

The Respiratory Muscles

• Principle muscles are the diaphragm and intercostal muscles

• Diaphragm is a prime mover; it alone produces abt two thirds of the pulmonary airflow

• The diaphragm, at rest, is domed, and when contracting, move downward

• Enlargement of the thoracic cavity lowers its internal pressure and produces an inflow of air

• Other muscles aid the diaphragm as synergists

  • internal and external intercostal muscles btw the ribs

    • primary function is to keep the chest form moving inward

  • The scalene muscles (of neck ribs 1 & 2; holding them stationary)

    • attach to the first rib and can pull upward during quiet breathing

    • and can pull upwards like the handle on a bucket and enlarge the chest laterally & anteriorly

  • Accessory muscles