AR

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 β†’ bronchioles β†’ 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 70mΒ² 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