Anatomy Lecture 13/14 (II) Part 1

functions of respiratory system

blood and lymph flow, platelet production, blood filtration, and expulsion of abdominal contents

blood and lymph flow

breathing creates pressure gradients between thorax and abdomen that promote flow of lymph and blood

platelet production

more than half od platelets are made by megakaryocytes in lungs

blood filtration

lungs filter small clots and dissolves them

expulsion of abdominal contents

breath0holding assists in urination, defecation, and childbirth

principal organs of respiratory system

nose, pharynx, larynx, trachea, bronchi, lungs

conducting zone

passages that serve only for airflow; nostrils through major bronchioles

respiratory zone

regions that participate in gas exchange; alveoli and nearby structures

upper respiratory tract

airway from nose through larynx

lower respiratory tract

regions from trachea through lungs

nose

warms, cleanses, and humidifies inhaled air; detects odors; and serves as a resonating chamber that amplifies voice; extends from nostrils to posterior nasal apertures

nasal septum

divides nasal cavity into right and left nasal fossae

vestibule

small, dilated chamber just inside nostrils, lined with stratified squamous epithelium

guard hairs or vibrissae

stiff hairs that block insects and debris from entering nose

superior, middle, and inferior nasal conchae

project from lateral walls toward septum

meatus

narrow air passage beneath each concha

narrowness and turbulence ensure

most air contacts mucous membranes to clean, warm, and moisten the air

respiratory epithelium

covers nasal mucosa; ciliated pseudostratified columnar epithelium

ciliated cells

have motile cilia that propel the mucus posteriorly toward pharynx to be swallowed

goblet cells

produce most of the mucus, supplemented by mucous glands in lamina propria

olfactory epitheliium

involved in the sense of smell; located at roof of each nasal fossa; immobile cilia bind odorant molecules; glands secrete serous fluid to assist diffusion of odor molecules to receptors on the cilia

pharynx

muscular funnel extending about 13 cm from posterior nasal apertures to larynx; muscles assist in swallowing and speech

nasopharyx

posterior to nasal apertures and above soft palate; receives auditory tubes and contains pharyngeal tonsil

oropharynx

space between solft palate and epiglottis; contains palatine tonsils

laryngopharynx

posterior to larynx, from epiglottis to cricoid cartilage; esophagus begins at that point

larynx

cartilaginous chamber about 4 cm long; primary function is to keep food and drink out of airway; also involved in production of sound (voice box)

epiglottis

flap of tissue that guards superior opening of larynx; at rest, stands almost vertically; during swallowing, extrinsic muscles pull larynx upward, tongue pushes epiglottis down to meet it; closes airway and directs food to esopjagus behind it

vestibular folds

play greater role in keeping food and drink out of airway; plays no role in speech but close the larynx during swallowing

epiglottic cartilage

most superior; spoon-shaped supportive plate in epiglottis

thyroid cartilage

sheild-shaped and largest laryngeal cartilage; contains laryngeal prominence; testosterone stimulates growth, large in males

cricoid cartilage

ring like shape; connects larynx to trachea

vocal cords

produce sound when air passes between them; contain vocal ligaments covered with stratified squamous epithelium, suited to endure vibration and contact

glottis

vocal cords and the opening between them

extrinsic muscles

superficial layer of muscles connecting larynx to hyoid bone; elevate larynx during swallowing

intrinsic muscles

abduct or adduct vocal cords, depending on direction of rotation; air forced between adducted cords vibrates them producing high-pitched sound; lower pitched sound when cords are more slack

adult male vocal cords

usually longer and thicker, vibrate more slowly, and produce lower pitched sound

how is loudness determined?

by force of air passing between the vocal cords

what do vocal cords produce?

crude sounds that are formed into words by actions of pharynx, oral cavity, tongue, and lipids

trachea

tube that connects larynx to bronchi; commonly called the windpipe

structure of trachea

anterior to esophagus; superior to c shaped rings of hyaline cartilage; opening in cartilage rings faces posteriorly toward esophagus which allows it to expand as swallowed food passes by

c shaped rings of hyaline cartilage importance

prevent collapse of trachea during inhalation

trachealis

muscle spans opening in rings; contracts (parasym) or relaxes (sym) to adjust airflow

carina

lowermost tracheal cartilage has internal median ridge

histology of trachea

lined by ciliated pseudostratified columnar epithelium; contains mucus secreting cells, ciliated cells, and stem cells

mucociliary escalator

mechanism for debris removal; mucus traps inhaled particles, upward beating cilia moves mucous to pharynx to be swallowed

tracheotomy

to make a temporary opening in the trachea and insert a tube to allow airflow; prevents asphyxiation due to upper airway obstruction

what are potential problems of a tracheaotomy?

inhaled air bypasses the nasal cavity and is not humidified; if left for long, will dry out mucous membranes; become encrusted and interefere with clearance of mucus from tract, thereby promoting infection

intubation

when a patient is on a ventilator, air is introduced directly into trachea; air must be filtered and humidified to precent respiratory tract damage

base

broad concave portion resting on diaphragm

apex

tip that projects just above the clavicle

costal surface

pressed against the ribcage

mediastinal surface

faces medially toward the heart

hilum

slit through which the lung receives the main bronchus, blood vessels, lymphatics, and nerves; structures near constitute the root of the lung

right lung

has greater volume than left lung; shorter than left because liver rises higher on the right ; has three lobes

horizontal fissue

separates superior and middle lobes

oblique fissure

separates middle and inferior lobes

left lung

tall and narrow because the heart tilts toward the left and occupies more space on this side of mediastinum; has two lobes

cardiac impression

has indentation to accomodate heart

bronchial tree

a branching system of air tubes in each lung; extends from main bronchus to 65,000 terminal bronchioles

main bronchus

right main bronchus is wider and more vertical than left main bronchus; aspirated foreign objects lodge in the right main brinchus more often than in the left

lobar/secondary bronchi

serves each lobe of each lung; right main gives off three and left gives off two branches

lobar bronchi branch into

segmental/tertiary bronchi

main bronchi supported by rings of hyaline cartilage

transition to crescent shaped plates in lobar and segmental bronchi

all bronchi are lined with

ciliated pseudostratified columnar epithelium; cells grow shorter and the epithelium thinner as we progress distally towards the bronchioles

lamina propria has abundance of

mucous glands and lymphoid nodules (mucosa-associated lymhoid tisse)

all divisions of bronchial tree have a large amount of

elastic connective tissue, contributes to recoil during respiration

muscularis mucosae

well-developed layer of smooth muscle in mucosa; contracts or relaxes to constrict or dilate the airway

bronchodilation

increase in diameter of bronchus or bronchiole; epinephrine and sympathetic stimulation increases airflow

bronchoconstriction

decrease in diameter of bronchus or bronchiole; histamine, parasympathetic nerves, cold air, and chemical irritants decreases airflow

bronchioles

continuations of airway that lack supportive cartilage; have ciliated cuboidal epithelium and well-developed layer of smooth muscle

pulmonary lobule

portion of lung ventilated by one bronchiole

terminal brinchioles

final branches of conducting zone; have no mucous glands or goblet cells; have cilia that move mucus by mucociliary escalator; each gives off two or more smaller respiratory bronchioles

respiratory bronchioles

considered the beginning of the respiratory zone since alveoli have alveoli budding from their walls

alveolar ducts

elongated, thin-walled passages with alveoli along their walls; end in alveolar sacs

alveolar sacs

clusters of alveoli around a central space

alveoli

microscopic air pouches in the lungs

squamous (type !) alveolar cells/pneumocytes

thin cells allow rapid gas diffusion between air and blood; cover 95%

great (type 2) alveolar cells/pneumocytes

cuboidal cells that cover the remaining 5% of surface; repair the alveolar epithelium when the squamous cells are damaged

pulmonary surfactant

mixture of phospholipids and proteins that coats the alveoli and prevents them for collapsing during exhalation; reduces surface tension of the alveoli

alveolar macrophages (dust cells)

most numerous of all cells in the lung; wander lumens of alveoli and connective tissue between them; keep alveoli free from debris by phagocytizing dust particles; millions of dust cells die each day as they ride up the mucociliary escalator to be swallowed and digested with their load of debris

respiratory membrane

thin barrier between the alveolar air and blood; each alveolus surrounded by a basket of capillaries supplied by the pulmonary artery; gases exchanged across

respiratory membrane layers

squamous alveolar cells, endothelial cells of blood capillary, and shared basement membrane

pulmonary circuit

pulmonary trunk → pulmonary arteries → lobar arteries → capillaries surrounding alveoli → pulmonary veins; serves to unload carbon dioxide from blood so it can be exhaled and pick up oxygen from inhaled air; exchange occurs at respiratory membrane

bronchial arteries

arise from aoirta, supply lung tissue with blood supply

bronchial veins

drains this blood into azygos vein of thorax

right to left shunt

some bronchial venous blood mixes with pulmonary venous blood; dilutes oxygen content somewhat before it reaches the left atrium

to prevent fluid accumulation

alevoli are kept dry by low blood pressure in capillaries; reabsorption overrides filtration and keeps the alveoli free of excess fluid; low capillary blood pressure prevents rupture of the delicate respiratory membrane

lungs have more…

extensive lympahtic drainage than any other organ

no lymphatic capillaries at

alveoli

pleura

serous membrane that lines thoracic wall and forms surface of lung

visceral pleura

forms surface of lung

parietal pleura

adheres to mediastinum, inner surface of the rib cage and superior surface of the diaphragm

pleural cavity

potential space between the visceral and parietal pleurae

pleural effusion

pathological seepage of fluid into pleural cavity

causes of pleural effusion

congestive heart failure, pneumonia, pulmonary embolism

functions of pleurae and pleural fluid

reduction of friction, creation of pressure gradient, compartmentalization

reduction of friction

allows lungs to move with minimal friction

creation of a pressure gradient

pressure gradient assists with lung inflation

compartmentalization

prevents spread of infection from one organ in mediastinum to others