The respiratory system of newborns consists of smaller but rapidly developing structures compared to adults. At birth, the lungs contain far fewer alveoli that increase nearly ninefold by age 12. The nasal cavity warms and moistens air through hairs, mucus and blood vessels. The pharynx connects the mouth and nose while the larynx produces sounds and prevents aspiration. The trachea and bronchi contain rings of cartilage and divide further in the lungs. Pulmonary surfactant, produced by type II alveolar cells, reduces surface tension in the alveoli and is crucial for lung function.

3. Respiratory system in the newborn
• The respiratory tract consists of a complex of
structures that function under neural and
hormonal control.
• At birth the respiratory system is relatively small,
but after the first breath the lungs grow rapidly.
• The shape of the chest changes gradually from a
relatively round configuration at birth to one that
is more or less flattened in the anteroposterior
diameter in adulthood

5. • during the first year the alveoli in the terminal
units rapidly increase in number
• . In addition, the early globular alveoli develop
septa causes them to become more lobular.
• They continue to increase steadily until, at the
age of 12 years, there are approximately nine
times as many as were present at birth.
• In later stages of growth the structures
lengthen and enlarge.

7. Main functions of respiratory system
in children:
• Breathing and gas exchange function
• Defence function
• Metabolic function
• Deposited function
• Filtrated function
• Endocrine function

8. Nasal Cavity
• The nasal cavity has three main functions.
• The first is the cleansing, warming, and moistening of inspired air.
• It achieves this via nasal hairs (vibrissae) extending from the inner lining of
the nostrils (which filter macrophages), and the mucus-secreting goblet
cells in the nasal epithelium (which hydrate air and pick up smoke and
dust)
• . Also assisting in the nasal cavity functions are the pseudostratified
columnar epithelium lining the conchae (which are ciliated and
responsible for air transport), along with the highly vascular nasal
epithelium (which warm the air), and the turbinate bones (which circulate
the air in the cavity).
• The peculiarities of the nose:
• The nose consists particular by of cartilage,
• The nasal meatuses are narrow,
• There is no inferior nasal meatuse (until 4 years),
• Undeveloped submucosal membrane (until 8-9 years).

9. Pharynx
• The pharynx connects the nasal and oral cavities
to the larynx
• . Its supporting walls are composed of skeletal
muscle, and the lumen is lined with mucous
membrane, which eases the passage of food, and
further humidifies and cleanses inspired air.
The peculiarities of the pharynx at the neonate
• The pharynx is relatively small and narrow,
• The auditory tubes are small, wide, straight and
horizontal.

10. Larynx
• The larynx connects the laryngophayrnx to the trachea
• . It primary functions consist of permitting the passage of air during breathing, prevention of food
or fluid from entering the trachea during swallowing, and the production of sound via the "voice
box“
• . The larynx is composed of a framework involving 9 cartilages.
• There are 3 large single cartilages, thyroid cartilage, epiglottis, and cricoid cartilage.
• The other 6 cartilages are 3 pairs involved in the production of sound; the arytenoid, cuneiform,
and corniculate cartilage pairs.
• The peculiarities of the larynx at the neonate
• The larynx is funnel-shaped (in the adult it is relatively round),
• It is relatively long,
• The cricoid's cartilage descendents from the level of the fourth cervical vertebra in the infant to
that of the sixth in the adult
• The fissure of glottis is narrow and its muscles fatigue soon,
• Vocal ligaments and mucous membrane are very tender and well blood-supplied,
• Vocal ligament are relatively short.

11. Trachea
• The trachea, also known as the windpipe, connects the larynx to the primary bronchi.
• It is stiffened by 16-20 C-shaped rings of cartilage
• . The open part of the ring is located posteriorly and covered by fibrous connective tissue and
smooth muscle.
• The lumen of the trachea is lined with pseudostratified ciliated columnar epithelium.
• The epithelium contains mucus-secreting goblet cells which trap inhaled dust particles.
• The beating of the cilia on the epithelium carries mucus and trapped particles up to the pharynx
where it is removed by a cough reflex. At the lower end of the trachea, it divides to form right and
left primary bronchi.
• The peculiarities of the trachea:
• The length of the trachea is relatively larger (about 4 cm (in the adult 7 cm) and wide,
• It is composed of 15-17 cartilage rings (the amount does not increase),
• The bifurcation of the trachea lies opposite the third thoracic vertebra in infant and descends to a
position opposite the fourth vertebra in the adult,
• Mucus membrane is soft, well blood supplied, but sometime dry,
• It can collapse easily.

12. Bronchial Tree
• The bronchial tree consists of primary, secondary, and segmental bronchi,
bronchioles, and terminal bronchioles which divide to form alveolar
ducts.
• The bronchi contain hyaline cartilage rings in their walls, so as to keep the
air ways open.
• The lumen of bronchi is lined by pseudostratified columnar epithelium.
• The bronchioles contain little cartilage in their walls, instead having a
thick layer of smooth muscle which controls the size of the lumen.
• The lumen of bronchioles is lined by simple cuboidal epithelium.
• The peculiarities of the bronchi:
• in young children the bronchi are relatively wide,
• the right bronchus is a straight continuation of the trachea,
• the muscle and elastic fibres are undeveloped,
• the lobules are segmental bronchus are narrow.

15. Alveoli
• The alveoli are the final branching of the respiratory tree and act as the primary
gas exchange units of the lung.
• The gas-blood barrier between the alveolar space and the pulmonary capillaries is
extremely thin, allowing for rapid gas exchange.
• To reach the blood, oxygen must diffuse through the alveolar epithelium, a thin
interstitial space, and the capillary endothelium; CO2 follows the reverse course to
reach the alveoli.
• There are two types of alveolar epithelial cells.
• Type I cells have long cytoplasmic extensions which spread out thinly along the
alveolar walls and comprise the thin alveolar epithelium.
• Type II cells are more compact and are responsible for producing surfactant, a
phospholipid which lines the alveoli and serves to differentially reduce surface
tension at different volumes, contributing to alveolar stability.
• The peculiarities of the lung:
• size of alveoli is smaller than in adult,
• quantity of alveoli is relatively less than adult.
•

16. Surfactant
• The lung surfactant is a surface active substance covering the respiration
system of the lung
• . Type II pneumocytes produce the surfactant which is stored as lamellar
bodies and finally released into the alveolar fluid phase. At the air/water-
interface spreading establishes a molecular film which dynamically adapts
the surface tension to the actual area of the interface during breathing.
The lung surfactant consists of lipids - mainly lecithine (DPPC), unsaturated
phosphatidyl cholins (PCs), negatively charged phosphatidyl glycerols
(PGs), and proteins
• . Two out of four specific proteins, SP-B and SP-C, together with lipids
seem to be responsible for its surface active properties. Pulmonary
surfactant is a surface-active lipoprotein formed by type II alveolar cells.
The proteins and lipids that comprise surfactant have both a hydrophilic
region and a hydrophobic region. By adsorbing to the air-water interface
of alveoli with the hydrophilic headgroups in the water and the
hydrophobic tails facing towards the air, the main lipid component of
surfactant, dipalmitoylphosphatidylcholine, reduces surface tension.