Respiratory system and development Flashcards
Conducting zone
- main (primary) bronchi
- lobar bronchi
- segmental bronchi
Respiratory zone
bronchioles, alveolar ducts and sacs
Pharynx
passageway connecting the nasal and oral cavities, superior to the larynx, inferior to esophagus:
- nasopharynx - posterior to the NC and superior to the OC, air passageway, closed during swallowing
- oropharynx - posterior to the OC, common passage for food and air
- laryngopharynx - joint passageway for food and air
Larynx
framework of 9 cartilages connected by
ligaments and membranes, voice production, open airway, mechanism of directing air and food into their proper
channels – the trachea and esophagus, suspended from the hyoid bone, enclosed laterally by the pharynx, inferiorly continuous with the trachea
Trachea
windpipe, descends from the larynx through the neck and into the
mediastinum, where it ends by dividing into the two main (primary) bronchi
Right bronchi
wider, shorter, and runs more
vertically than left, aspirated foreign bodies are more likely to enter and lodge in the right bronchus or in one of its branches
Pleura cavity
a double-layered sac surrounding each lung, space between visceral and parietal,
- parietal pleura – lines the pleural cavity.
- visceral pleura – covers the lungs
Right and left lung
RL - 3 lobes – oblique and horizontal fissures
LL - 2 lobes – oblique fissure; cardiac notch
Ventilation
thorax an expandable container, entrance - the trachea, enlarging dimensions of the thorax decreases air pressure, causes air to flow in from the outside, air always moves from area of higher pressure to an area of a lower pressure
Normal inspiration
during normal inspiration, the diaphragm and intercostal muscles function to increase the volume of the thorax
Quiet vs. forced expiration
- quiet: relaxation of external intercostals + diaphragm; decrease thoracic volume
increase lung pressure - out flow of air - forced: involves internal intercostals and abdominal muscles
Thoracic volume inspiration
As the ribs are raised by the contracting external intercostal muscles, the anteroposterior dimension of the thorax also enlarges
Inspiration EIM
external intercostal muscles elevate the ribs during inspiration, causing
the thorax to expand laterally
Diaphragm
skeletal muscle, somatic motor and sensory innervation from phrenic nerves (C3-
C5) centrally and intercostal nerves
peripherally, blood supply from branches of the internal thoracic artery
Passive expiration
the diaphragm relaxes, moving superiorly, while the rib cage drops down subtly
Forced expiration
the abdominal wall muscles work together to increase intra- abdominal pressure, forcing the diaphragm superiorly. Also, the muscles of the abdominal wall depress the rib cage, decreasing thoracic volume
Embryonic period: weeks 4 - 7
- Laryngotracheal diverticulum forms (growth in a cranial/caudal direction)
- Primary bronchial buds form (growth in a lateral direction) - trachea and larynx form
- Primary Bronchi begin to differentiate, 3 lobes on right, 2 on left
Pseudoglandular period: weeks 5 - 17
- emerging respiratory apparatus resembles -> exocrine gland
- 14 additional branchings will yield the true respiratory tree and terminal bronchioles
- major respiratory developments are set in motion, except gas exchange
Canalicular period: weeks 16 - 25
- terminal bronchioles continue to mature and divide-> 2 or more respiratory bronchioles
- mesoderm -> vascularized, necessary for eventual gas exchange
- Terminal sacs have begun to develop at the ends of the respiratory bronchioles
- maturation begins cranially and
progresses caudally
Terminal sac period: weeks 24 - late fetal
terminal sacs develop -> epithelium lining them becomes thinner, allows for capillaries to bulge outward into the sacs, communication between epithelial
and endothelial is the precursor to the blood-air barriers, gas exchange is present
Alveolar period: weeks 36 - 8 yrs.
terminal sacs multiply, epithelium lining the sacs continues to thin, the capillary network increases its ability for gas exchange, the lung matures, 100,000,000+ sacs
Alveolar epithelium
must be thin so that gas can pass through and exchange via the capillaries, as scar tissue develops, interstitial tissues grow abnormally and/or bronchioles change with age and environment, the ability to adequately exchange gases diminishes
