Anatomy & Development of Respiratory System

Question 1

what structure defines the boundaries of a bronchial pulmonary segment on the outer surface of the lung?

Answer 1

pulmonary veins

Question 2

what developing structure gives rise to 3 separate cavities in the thorax?

Answer 2

pleuropericardial folds

Question 3

in which location can trauma cause a pneumothorax and enter the pleural cavity without hitting in the lung?

Answer 3

9th intercostal space, mid axillary, left lung

Question 4

3 layers of the mesoderm

Answer 4

1. paraxial
2. intermediate
3. lateral plate

Question 5

lateral plate mesoderm

Answer 5

*forms most of the dermis layer of skin AND the serous membranes lining body cavities and covering of organs
*lateral plate mesoderm splits into 2 layers:
1. somatopleuric mesoderm (somatic)
-forms the dermis of the skin and the appendicular skeleton
2. splanchnopleuric mesoderm (splanchnic)
-associated with the serous membranes and lining of organs in body cavities

Question 6

intraembryonic coelom

Answer 6

*a hollow cavity (intraembryonic coelom) forms between the splanchnic and somatic mesoderm
-this is ONE CONTINUOUS BODY CAVITY that goes from the thorax down to the pelvis
-eventually must SEPARATE this intraembryonic coelom with a MUSCULAR DIAPHRAGM to form the thoracic cavity superiorly and the abdominopelvic cavity inferiorly

Question 7

development of the diaphragm - steps

Answer 7

1. septum transversum (a semicircular shelf of somatic mesoderm) grows out from the ventral body wall at C3-C5 and continually grows until it merges with the splanchnic mesoderm surrounding the gut tube
2. two horizontal folds of somatic mesoderm emerge on each dorsal lateral side of the body cavity (pleuroperitoneal membranes)
3. these pleuroperitoneal membranes fuse with the ventral septum transversum to close off the remaining space, completing the diaphragm

Question 8

separation of the thorax into 2 pleural cavities and 1 pericardial cavity

Answer 8

1. 2 pleuropericardial folds grow from the lateral body walls toward the midline in the thoracic cavity
2. these folds reach the splanchnic mesoderm covering the emerging lungs and forming heart, subdividing the thoracic cavity into 2 pleural and 1 pericardial cavities
   -heart (pericardial cavity) is anterior
   -lungs (pleural cavities) are posterior

Question 9

lung development

Answer 9

1. an endodermal outgrowth of the primitive foregut (laryngotracheal diverticulum) will form, which will ultimately develop into the larynx and trachea
2. the laryngotracheal diverticulum will separate from the future esophagus via 2 prominent tracheoesophageal folds
3. the 2 folds meet medially
4. lung buds form

Question 10

pseudoglandular stage of lung development

Answer 10

*weeks 8-16
*lung parenchyma resembles a gland

Question 11

canalicular stage of lung development

Answer 11

*weeks 17-26
*lumen of bronchi increase in diameter with vascularization of tissue

Question 12

saccular stage of lung development

Answer 12

*week 26-birth
*cells lining the terminal alveolar sacs become thin - SIMPLE SQUAMOUS EPITHELIUM
*capillary beds develop around sacs
*alveolar sacs start producing surfactant

Question 13

alveolar stage of lung development

Answer 13

*36 weeks to many years after birth
*maturation of alveoli; membrane between capillary and alveolus thins

Question 14

3 general steps involved in development of the respiratory system

Answer 14

1. separation of the thorax from the abdomen (pleuroperitoneal membrane)
2. separation of the thorax into 3 compartments (2 pleural cavities & 1 pericardial cavity - pleuropericardial folds)
3. maturation of the lungs

Question 15

pleural cavities - overview

Answer 15

*each pleural cavity is a separate sac formed by a serous membrane (the pleura)
*the serous membrane is covered by squamous epithelium and underlying connective tissue
*parietal pleura = pleura lining the thoracic wall
*visceral pleura = pleura covering the lungs
*note - the parietal and visceral pleura are CONTINUOUS at the root of the lung

Question 16

divisions of the parietal pleura

Answer 16

*recall - the parietal pleura is the pleura lining the thoracic cavity
-costosternal pleura
-mediastinal pleura
-diaphragmatic pleura
-cervical pleura/cupula

*2 important reflections of the pleura:
-costodiaphragmatic reflection (where the diaphragm meets the rib cage)
-costomediastinal reflection (where the rib cage meets the mediastinum)

Question 17

pleural cavity

Answer 17

*a potential space filled with a thin film of fluid that allows the visceral and parietal pleura to slide on one another as the lung fills
*surface tension of this fluid helps hold the visceral and parietal layers together

Question 18

pneumothorax

Answer 18

air in the pleural cavity

Question 19

hydrothorax

Answer 19

fluid in the pleural cavity (aka pleural effusion)

Question 20

empyema/pyothorax

Answer 20

pus in the pleural cavity

Question 21

hemothorax

Answer 21

blood in the pleural cavity

Question 22

atelectasis

Answer 22

collapsed lung

Question 23

congenital diaphragmatic hernia (CDH) is most commonly caused by…

Answer 23

CDH is most commonly caused by an embryologic defect in fusion of the pleuroperitoneal folds with the septum transversum on the LEFT side

Question 24

development of the diaphragm - components

Answer 24

*the formation of the diaphragm divides the intraembryonic coelom into thorax and abdomen:
*diaphragm components:
1. septum transversum
2. pleuroperitoneal membranes
3. paraxial mesoderm of the body wall
4. splanchnic mesoderm (esophagus)